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-rw-r--r--compiler/rustc_abi/Cargo.toml4
-rw-r--r--compiler/rustc_abi/src/extern_abi.rs25
-rw-r--r--compiler/rustc_abi/src/lib.rs2
-rw-r--r--compiler/rustc_ast/Cargo.toml10
-rw-r--r--compiler/rustc_ast/src/ast.rs6
-rw-r--r--compiler/rustc_ast/src/token.rs20
-rw-r--r--compiler/rustc_ast_lowering/Cargo.toml4
-rw-r--r--compiler/rustc_ast_lowering/src/expr.rs6
-rw-r--r--compiler/rustc_ast_lowering/src/lib.rs4
-rw-r--r--compiler/rustc_ast_lowering/src/pat.rs9
-rw-r--r--compiler/rustc_ast_passes/Cargo.toml4
-rw-r--r--compiler/rustc_ast_passes/messages.ftl2
-rw-r--r--compiler/rustc_ast_pretty/Cargo.toml4
-rw-r--r--compiler/rustc_ast_pretty/src/pprust/state.rs2
-rw-r--r--compiler/rustc_attr_parsing/Cargo.toml2
-rw-r--r--compiler/rustc_attr_parsing/messages.ftl2
-rw-r--r--compiler/rustc_borrowck/Cargo.toml8
-rw-r--r--compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs11
-rw-r--r--compiler/rustc_builtin_macros/Cargo.toml4
-rwxr-xr-xcompiler/rustc_codegen_cranelift/scripts/test_rustc_tests.sh4
-rw-r--r--compiler/rustc_codegen_gcc/build_system/src/test.rs22
-rw-r--r--compiler/rustc_codegen_gcc/src/back/lto.rs13
-rw-r--r--compiler/rustc_codegen_gcc/src/lib.rs7
-rw-r--r--compiler/rustc_codegen_llvm/Cargo.toml14
-rw-r--r--compiler/rustc_codegen_llvm/src/attributes.rs51
-rw-r--r--compiler/rustc_codegen_llvm/src/back/lto.rs41
-rw-r--r--compiler/rustc_codegen_llvm/src/back/write.rs2
-rw-r--r--compiler/rustc_codegen_llvm/src/builder.rs29
-rw-r--r--compiler/rustc_codegen_llvm/src/builder/gpu_offload.rs2
-rw-r--r--compiler/rustc_codegen_llvm/src/context.rs14
-rw-r--r--compiler/rustc_codegen_llvm/src/intrinsic.rs26
-rw-r--r--compiler/rustc_codegen_llvm/src/lib.rs7
-rw-r--r--compiler/rustc_codegen_llvm/src/llvm/ffi.rs1
-rw-r--r--compiler/rustc_codegen_ssa/Cargo.toml14
-rw-r--r--compiler/rustc_codegen_ssa/messages.ftl14
-rw-r--r--compiler/rustc_codegen_ssa/src/back/link.rs17
-rw-r--r--compiler/rustc_codegen_ssa/src/back/linker.rs17
-rw-r--r--compiler/rustc_codegen_ssa/src/back/lto.rs8
-rw-r--r--compiler/rustc_codegen_ssa/src/back/symbol_export.rs52
-rw-r--r--compiler/rustc_codegen_ssa/src/back/write.rs150
-rw-r--r--compiler/rustc_codegen_ssa/src/base.rs80
-rw-r--r--compiler/rustc_codegen_ssa/src/codegen_attrs.rs9
-rw-r--r--compiler/rustc_codegen_ssa/src/lib.rs2
-rw-r--r--compiler/rustc_codegen_ssa/src/mir/rvalue.rs27
-rw-r--r--compiler/rustc_codegen_ssa/src/traits/write.rs6
-rw-r--r--compiler/rustc_const_eval/Cargo.toml6
-rw-r--r--compiler/rustc_const_eval/messages.ftl2
-rw-r--r--compiler/rustc_data_structures/Cargo.toml18
-rw-r--r--compiler/rustc_driver_impl/Cargo.toml6
-rw-r--r--compiler/rustc_driver_impl/messages.ftl4
-rw-r--r--compiler/rustc_error_messages/Cargo.toml2
-rw-r--r--compiler/rustc_errors/Cargo.toml4
-rw-r--r--compiler/rustc_errors/src/diagnostic.rs5
-rw-r--r--compiler/rustc_errors/src/emitter.rs1
-rw-r--r--compiler/rustc_errors/src/lib.rs29
-rw-r--r--compiler/rustc_expand/Cargo.toml4
-rw-r--r--compiler/rustc_expand/src/mbe/macro_parser.rs20
-rw-r--r--compiler/rustc_expand/src/mbe/transcribe.rs7
-rw-r--r--compiler/rustc_feature/Cargo.toml2
-rw-r--r--compiler/rustc_feature/src/accepted.rs3
-rw-r--r--compiler/rustc_feature/src/unstable.rs5
-rw-r--r--compiler/rustc_fluent_macro/Cargo.toml4
-rw-r--r--compiler/rustc_fs_util/Cargo.toml2
-rw-r--r--compiler/rustc_hir/Cargo.toml8
-rw-r--r--compiler/rustc_hir/src/hir.rs9
-rw-r--r--compiler/rustc_hir/src/intravisit.rs2
-rw-r--r--compiler/rustc_hir_analysis/Cargo.toml4
-rw-r--r--compiler/rustc_hir_analysis/src/check/check.rs2
-rw-r--r--compiler/rustc_hir_analysis/src/check/intrinsic.rs3
-rw-r--r--compiler/rustc_hir_analysis/src/check/mod.rs2
-rw-r--r--compiler/rustc_hir_analysis/src/check/region.rs8
-rw-r--r--compiler/rustc_hir_analysis/src/collect/generics_of.rs6
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/generics.rs9
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs4
-rw-r--r--compiler/rustc_hir_analysis/src/lib.rs59
-rw-r--r--compiler/rustc_hir_pretty/src/lib.rs6
-rw-r--r--compiler/rustc_hir_typeck/Cargo.toml4
-rw-r--r--compiler/rustc_hir_typeck/src/coercion.rs2
-rw-r--r--compiler/rustc_hir_typeck/src/expr.rs11
-rw-r--r--compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs17
-rw-r--r--compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs146
-rw-r--r--compiler/rustc_hir_typeck/src/pat.rs12
-rw-r--r--compiler/rustc_incremental/Cargo.toml4
-rw-r--r--compiler/rustc_index/src/interval.rs54
-rw-r--r--compiler/rustc_index_macros/Cargo.toml4
-rw-r--r--compiler/rustc_infer/Cargo.toml4
-rw-r--r--compiler/rustc_infer/src/infer/context.rs2
-rw-r--r--compiler/rustc_interface/Cargo.toml2
-rw-r--r--compiler/rustc_interface/src/interface.rs6
-rw-r--r--compiler/rustc_interface/src/passes.rs3
-rw-r--r--compiler/rustc_lexer/Cargo.toml2
-rw-r--r--compiler/rustc_lexer/src/lib.rs43
-rw-r--r--compiler/rustc_lint/Cargo.toml3
-rw-r--r--compiler/rustc_lint/src/foreign_modules.rs27
-rw-r--r--compiler/rustc_lint/src/lib.rs3
-rw-r--r--compiler/rustc_lint/src/types.rs875
-rw-r--r--compiler/rustc_lint/src/types/improper_ctypes.rs1016
-rw-r--r--compiler/rustc_lint_defs/src/builtin.rs54
-rw-r--r--compiler/rustc_llvm/Cargo.toml2
-rw-r--r--compiler/rustc_llvm/build.rs8
-rw-r--r--compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp11
-rw-r--r--compiler/rustc_log/Cargo.toml4
-rw-r--r--compiler/rustc_log/src/lib.rs2
-rw-r--r--compiler/rustc_macros/Cargo.toml4
-rw-r--r--compiler/rustc_metadata/Cargo.toml10
-rw-r--r--compiler/rustc_metadata/src/creader.rs18
-rw-r--r--compiler/rustc_middle/Cargo.toml12
-rw-r--r--compiler/rustc_middle/src/arena.rs1
-rw-r--r--compiler/rustc_middle/src/middle/codegen_fn_attrs.rs2
-rw-r--r--compiler/rustc_middle/src/middle/region.rs39
-rw-r--r--compiler/rustc_middle/src/mir/consts.rs2
-rw-r--r--compiler/rustc_middle/src/mir/statement.rs22
-rw-r--r--compiler/rustc_middle/src/mir/visit.rs18
-rw-r--r--compiler/rustc_middle/src/query/erase.rs5
-rw-r--r--compiler/rustc_middle/src/query/mod.rs10
-rw-r--r--compiler/rustc_middle/src/ty/codec.rs10
-rw-r--r--compiler/rustc_middle/src/ty/context.rs15
-rw-r--r--compiler/rustc_middle/src/ty/generics.rs2
-rw-r--r--compiler/rustc_middle/src/ty/rvalue_scopes.rs37
-rw-r--r--compiler/rustc_mir_build/Cargo.toml6
-rw-r--r--compiler/rustc_mir_dataflow/Cargo.toml4
-rw-r--r--compiler/rustc_mir_dataflow/src/impls/liveness.rs37
-rw-r--r--compiler/rustc_mir_dataflow/src/impls/mod.rs3
-rw-r--r--compiler/rustc_mir_dataflow/src/points.rs68
-rw-r--r--compiler/rustc_mir_dataflow/src/value_analysis.rs9
-rw-r--r--compiler/rustc_mir_transform/Cargo.toml6
-rw-r--r--compiler/rustc_mir_transform/src/check_inline_always_target_features.rs88
-rw-r--r--compiler/rustc_mir_transform/src/coverage/expansion.rs2
-rw-r--r--compiler/rustc_mir_transform/src/cross_crate_inline.rs11
-rw-r--r--compiler/rustc_mir_transform/src/dest_prop.rs794
-rw-r--r--compiler/rustc_mir_transform/src/errors.rs41
-rw-r--r--compiler/rustc_mir_transform/src/gvn.rs62
-rw-r--r--compiler/rustc_mir_transform/src/lib.rs4
-rw-r--r--compiler/rustc_mir_transform/src/lint_tail_expr_drop_order.rs5
-rw-r--r--compiler/rustc_mir_transform/src/simplify.rs18
-rw-r--r--compiler/rustc_mir_transform/src/ssa.rs4
-rw-r--r--compiler/rustc_monomorphize/Cargo.toml4
-rw-r--r--compiler/rustc_next_trait_solver/Cargo.toml4
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs47
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs151
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/inspect/build.rs399
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/mod.rs11
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/search_graph.rs14
-rw-r--r--compiler/rustc_parse/Cargo.toml8
-rw-r--r--compiler/rustc_parse/messages.ftl2
-rw-r--r--compiler/rustc_parse/src/lexer/mod.rs41
-rw-r--r--compiler/rustc_parse/src/lib.rs37
-rw-r--r--compiler/rustc_parse/src/parser/expr.rs5
-rw-r--r--compiler/rustc_parse/src/parser/mod.rs2
-rw-r--r--compiler/rustc_parse/src/parser/pat.rs2
-rw-r--r--compiler/rustc_parse_format/Cargo.toml2
-rw-r--r--compiler/rustc_passes/Cargo.toml2
-rw-r--r--compiler/rustc_passes/messages.ftl1
-rw-r--r--compiler/rustc_passes/src/errors.rs18
-rw-r--r--compiler/rustc_passes/src/liveness.rs52
-rw-r--r--compiler/rustc_pattern_analysis/Cargo.toml6
-rw-r--r--compiler/rustc_privacy/Cargo.toml2
-rw-r--r--compiler/rustc_proc_macro/Cargo.toml2
-rw-r--r--compiler/rustc_public/Cargo.toml4
-rw-r--r--compiler/rustc_public/src/unstable/convert/stable/ty.rs8
-rw-r--r--compiler/rustc_query_impl/Cargo.toml4
-rw-r--r--compiler/rustc_query_impl/src/lib.rs2
-rw-r--r--compiler/rustc_query_system/Cargo.toml2
-rw-r--r--compiler/rustc_query_system/messages.ftl4
-rw-r--r--compiler/rustc_resolve/Cargo.toml10
-rw-r--r--compiler/rustc_resolve/messages.ftl2
-rw-r--r--compiler/rustc_resolve/src/diagnostics.rs188
-rw-r--r--compiler/rustc_resolve/src/errors.rs12
-rw-r--r--compiler/rustc_resolve/src/ident.rs23
-rw-r--r--compiler/rustc_resolve/src/late.rs54
-rw-r--r--compiler/rustc_resolve/src/late/diagnostics.rs2
-rw-r--r--compiler/rustc_resolve/src/lib.rs16
-rw-r--r--compiler/rustc_sanitizers/Cargo.toml4
-rw-r--r--compiler/rustc_serialize/Cargo.toml6
-rw-r--r--compiler/rustc_session/Cargo.toml8
-rw-r--r--compiler/rustc_session/src/options.rs71
-rw-r--r--compiler/rustc_span/Cargo.toml8
-rw-r--r--compiler/rustc_span/src/symbol.rs3
-rw-r--r--compiler/rustc_symbol_mangling/Cargo.toml4
-rw-r--r--compiler/rustc_symbol_mangling/src/v0.rs8
-rw-r--r--compiler/rustc_target/Cargo.toml6
-rw-r--r--compiler/rustc_target/src/callconv/loongarch.rs137
-rw-r--r--compiler/rustc_target/src/spec/targets/aarch64_pc_windows_msvc.rs2
-rw-r--r--compiler/rustc_target/src/spec/targets/aarch64_unknown_trusty.rs2
-rw-r--r--compiler/rustc_target/src/spec/targets/arm64ec_pc_windows_msvc.rs4
-rw-r--r--compiler/rustc_target/src/spec/targets/armv7_unknown_trusty.rs2
-rw-r--r--compiler/rustc_target/src/spec/targets/loongarch64_unknown_none.rs2
-rw-r--r--compiler/rustc_target/src/spec/targets/nvptx64_nvidia_cuda.rs2
-rw-r--r--compiler/rustc_target/src/spec/targets/x86_64_unknown_trusty.rs2
-rw-r--r--compiler/rustc_thread_pool/Cargo.toml4
-rw-r--r--compiler/rustc_trait_selection/Cargo.toml6
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs2
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs77
-rw-r--r--compiler/rustc_trait_selection/src/lib.rs1
-rw-r--r--compiler/rustc_trait_selection/src/solve.rs16
-rw-r--r--compiler/rustc_trait_selection/src/solve/inspect/analyse.rs18
-rw-r--r--compiler/rustc_traits/Cargo.toml2
-rw-r--r--compiler/rustc_transmute/Cargo.toml4
-rw-r--r--compiler/rustc_ty_utils/Cargo.toml4
-rw-r--r--compiler/rustc_type_ir/Cargo.toml12
-rw-r--r--compiler/rustc_type_ir/src/interner.rs12
-rw-r--r--compiler/rustc_type_ir/src/search_graph/mod.rs42
-rw-r--r--compiler/rustc_type_ir/src/solve/inspect.rs29
-rw-r--r--compiler/rustc_type_ir_macros/Cargo.toml4
204 files changed, 3529 insertions, 2812 deletions
diff --git a/compiler/rustc_abi/Cargo.toml b/compiler/rustc_abi/Cargo.toml
index 3de6d186b8a..83d96d8d04d 100644
--- a/compiler/rustc_abi/Cargo.toml
+++ b/compiler/rustc_abi/Cargo.toml
@@ -5,7 +5,7 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-bitflags.workspace = true
+bitflags = "2.4.1"
 rand = { version = "0.9.0", default-features = false, optional = true }
 rand_xoshiro = { version = "0.7.0", optional = true }
 rustc_data_structures = { path = "../rustc_data_structures", optional = true }
@@ -15,7 +15,7 @@ rustc_index = { path = "../rustc_index", default-features = false }
 rustc_macros = { path = "../rustc_macros", optional = true }
 rustc_serialize = { path = "../rustc_serialize", optional = true }
 rustc_span = { path = "../rustc_span", optional = true }
-tracing.workspace = true
+tracing = "0.1"
 # tidy-alphabetical-end
 
 [features]
diff --git a/compiler/rustc_abi/src/extern_abi.rs b/compiler/rustc_abi/src/extern_abi.rs
index 41d744e1946..e3b2b1eff72 100644
--- a/compiler/rustc_abi/src/extern_abi.rs
+++ b/compiler/rustc_abi/src/extern_abi.rs
@@ -6,6 +6,8 @@ use std::hash::{Hash, Hasher};
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher, StableOrd};
 #[cfg(feature = "nightly")]
 use rustc_macros::{Decodable, Encodable};
+#[cfg(feature = "nightly")]
+use rustc_span::Symbol;
 
 use crate::AbiFromStrErr;
 
@@ -226,6 +228,13 @@ impl StableOrd for ExternAbi {
 #[cfg(feature = "nightly")]
 rustc_error_messages::into_diag_arg_using_display!(ExternAbi);
 
+#[cfg(feature = "nightly")]
+pub enum CVariadicStatus {
+    NotSupported,
+    Stable,
+    Unstable { feature: Symbol },
+}
+
 impl ExternAbi {
     /// An ABI "like Rust"
     ///
@@ -238,23 +247,33 @@ impl ExternAbi {
         matches!(self, Rust | RustCall | RustCold)
     }
 
-    pub fn supports_varargs(self) -> bool {
+    /// Returns whether the ABI supports C variadics. This only controls whether we allow *imports*
+    /// of such functions via `extern` blocks; there's a separate check during AST construction
+    /// guarding *definitions* of variadic functions.
+    #[cfg(feature = "nightly")]
+    pub fn supports_c_variadic(self) -> CVariadicStatus {
         // * C and Cdecl obviously support varargs.
         // * C can be based on Aapcs, SysV64 or Win64, so they must support varargs.
         // * EfiApi is based on Win64 or C, so it also supports it.
+        // * System automatically falls back to C when used with variadics, therefore supports it.
         //
         // * Stdcall does not, because it would be impossible for the callee to clean
         //   up the arguments. (callee doesn't know how many arguments are there)
         // * Same for Fastcall, Vectorcall and Thiscall.
         // * Other calling conventions are related to hardware or the compiler itself.
+        //
+        // All of the supported ones must have a test in `tests/codegen/cffi/c-variadic-ffi.rs`.
         match self {
             Self::C { .. }
             | Self::Cdecl { .. }
             | Self::Aapcs { .. }
             | Self::Win64 { .. }
             | Self::SysV64 { .. }
-            | Self::EfiApi => true,
-            _ => false,
+            | Self::EfiApi => CVariadicStatus::Stable,
+            Self::System { .. } => {
+                CVariadicStatus::Unstable { feature: rustc_span::sym::extern_system_varargs }
+            }
+            _ => CVariadicStatus::NotSupported,
         }
     }
 }
diff --git a/compiler/rustc_abi/src/lib.rs b/compiler/rustc_abi/src/lib.rs
index a1a0de5aaf8..369874521e5 100644
--- a/compiler/rustc_abi/src/lib.rs
+++ b/compiler/rustc_abi/src/lib.rs
@@ -63,6 +63,8 @@ mod tests;
 
 pub use callconv::{Heterogeneous, HomogeneousAggregate, Reg, RegKind};
 pub use canon_abi::{ArmCall, CanonAbi, InterruptKind, X86Call};
+#[cfg(feature = "nightly")]
+pub use extern_abi::CVariadicStatus;
 pub use extern_abi::{ExternAbi, all_names};
 #[cfg(feature = "nightly")]
 pub use layout::{FIRST_VARIANT, FieldIdx, Layout, TyAbiInterface, TyAndLayout, VariantIdx};
diff --git a/compiler/rustc_ast/Cargo.toml b/compiler/rustc_ast/Cargo.toml
index 7f948a65220..155e14a3796 100644
--- a/compiler/rustc_ast/Cargo.toml
+++ b/compiler/rustc_ast/Cargo.toml
@@ -5,9 +5,9 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-bitflags.workspace = true
-memchr.workspace = true
-rustc-literal-escaper.workspace = true
+bitflags = "2.4.1"
+memchr = "2.7.4"
+rustc-literal-escaper = "0.0.5"
 rustc_ast_ir = { path = "../rustc_ast_ir" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_index = { path = "../rustc_index" }
@@ -15,6 +15,6 @@ rustc_macros = { path = "../rustc_macros" }
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_span = { path = "../rustc_span" }
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
-thin-vec.workspace = true
-tracing.workspace = true
+thin-vec = "0.2.12"
+tracing = "0.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
index de3e0e0c87f..802a6fa3249 100644
--- a/compiler/rustc_ast/src/ast.rs
+++ b/compiler/rustc_ast/src/ast.rs
@@ -937,7 +937,7 @@ pub enum PatKind {
 #[derive(Clone, Copy, Encodable, Decodable, Debug, PartialEq, Walkable)]
 pub enum PatFieldsRest {
     /// `module::StructName { field, ..}`
-    Rest,
+    Rest(Span),
     /// `module::StructName { field, syntax error }`
     Recovered(ErrorGuaranteed),
     /// `module::StructName { field }`
@@ -4051,8 +4051,8 @@ mod size_asserts {
     static_assert_size!(Local, 96);
     static_assert_size!(MetaItemLit, 40);
     static_assert_size!(Param, 40);
-    static_assert_size!(Pat, 72);
-    static_assert_size!(PatKind, 48);
+    static_assert_size!(Pat, 80);
+    static_assert_size!(PatKind, 56);
     static_assert_size!(Path, 24);
     static_assert_size!(PathSegment, 24);
     static_assert_size!(Stmt, 32);
diff --git a/compiler/rustc_ast/src/token.rs b/compiler/rustc_ast/src/token.rs
index ea98bebd305..6dc6d1026f6 100644
--- a/compiler/rustc_ast/src/token.rs
+++ b/compiler/rustc_ast/src/token.rs
@@ -22,8 +22,7 @@ pub enum CommentKind {
     Block,
 }
 
-// This type must not implement `Hash` due to the unusual `PartialEq` impl below.
-#[derive(Copy, Clone, Debug, Encodable, Decodable, HashStable_Generic)]
+#[derive(Copy, Clone, PartialEq, Debug, Encodable, Decodable, HashStable_Generic)]
 pub enum InvisibleOrigin {
     // From the expansion of a metavariable in a declarative macro.
     MetaVar(MetaVarKind),
@@ -45,20 +44,6 @@ impl InvisibleOrigin {
     }
 }
 
-impl PartialEq for InvisibleOrigin {
-    #[inline]
-    fn eq(&self, _other: &InvisibleOrigin) -> bool {
-        // When we had AST-based nonterminals we couldn't compare them, and the
-        // old `Nonterminal` type had an `eq` that always returned false,
-        // resulting in this restriction:
-        // https://doc.rust-lang.org/nightly/reference/macros-by-example.html#forwarding-a-matched-fragment
-        // This `eq` emulates that behaviour. We could consider lifting this
-        // restriction now but there are still cases involving invisible
-        // delimiters that make it harder than it first appears.
-        false
-    }
-}
-
 /// Annoyingly similar to `NonterminalKind`, but the slight differences are important.
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Encodable, Decodable, Hash, HashStable_Generic)]
 pub enum MetaVarKind {
@@ -142,7 +127,8 @@ impl Delimiter {
         }
     }
 
-    // This exists because `InvisibleOrigin`s should be compared. It is only used for assertions.
+    // This exists because `InvisibleOrigin`s should not be compared. It is only used for
+    // assertions.
     pub fn eq_ignoring_invisible_origin(&self, other: &Delimiter) -> bool {
         match (self, other) {
             (Delimiter::Parenthesis, Delimiter::Parenthesis) => true,
diff --git a/compiler/rustc_ast_lowering/Cargo.toml b/compiler/rustc_ast_lowering/Cargo.toml
index 317742a3bb8..6ac258155fe 100644
--- a/compiler/rustc_ast_lowering/Cargo.toml
+++ b/compiler/rustc_ast_lowering/Cargo.toml
@@ -24,6 +24,6 @@ rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
-thin-vec.workspace = true
-tracing.workspace = true
+thin-vec = "0.2.12"
+tracing = "0.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
index cbd17d66b75..3674814b796 100644
--- a/compiler/rustc_ast_lowering/src/expr.rs
+++ b/compiler/rustc_ast_lowering/src/expr.rs
@@ -1434,10 +1434,10 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         self.dcx().emit_err(FunctionalRecordUpdateDestructuringAssignment {
                             span: e.span,
                         });
-                        true
+                        Some(self.lower_span(e.span))
                     }
-                    StructRest::Rest(_) => true,
-                    StructRest::None => false,
+                    StructRest::Rest(span) => Some(self.lower_span(*span)),
+                    StructRest::None => None,
                 };
                 let struct_pat = hir::PatKind::Struct(qpath, field_pats, fields_omitted);
                 return self.pat_without_dbm(lhs.span, struct_pat);
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index 70595391b85..72f20a95ff0 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -2028,7 +2028,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
                 (
                     hir::ParamName::Plain(self.lower_ident(param.ident)),
-                    hir::GenericParamKind::Const { ty, default, synthetic: false },
+                    hir::GenericParamKind::Const { ty, default },
                 )
             }
         }
@@ -2508,7 +2508,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         fields: &'hir [hir::PatField<'hir>],
     ) -> &'hir hir::Pat<'hir> {
         let qpath = hir::QPath::LangItem(lang_item, self.lower_span(span));
-        self.pat(span, hir::PatKind::Struct(qpath, fields, false))
+        self.pat(span, hir::PatKind::Struct(qpath, fields, None))
     }
 
     fn pat_ident(&mut self, span: Span, ident: Ident) -> (&'hir hir::Pat<'hir>, HirId) {
diff --git a/compiler/rustc_ast_lowering/src/pat.rs b/compiler/rustc_ast_lowering/src/pat.rs
index b8f86247875..ed159f37051 100644
--- a/compiler/rustc_ast_lowering/src/pat.rs
+++ b/compiler/rustc_ast_lowering/src/pat.rs
@@ -106,10 +106,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                         break hir::PatKind::Struct(
                             qpath,
                             fs,
-                            matches!(
-                                etc,
-                                ast::PatFieldsRest::Rest | ast::PatFieldsRest::Recovered(_)
-                            ),
+                            match etc {
+                                ast::PatFieldsRest::Rest(sp) => Some(self.lower_span(*sp)),
+                                ast::PatFieldsRest::Recovered(_) => Some(Span::default()),
+                                _ => None,
+                            },
                         );
                     }
                     PatKind::Tuple(pats) => {
diff --git a/compiler/rustc_ast_passes/Cargo.toml b/compiler/rustc_ast_passes/Cargo.toml
index 6d2bcbed22b..3e04f8b11ec 100644
--- a/compiler/rustc_ast_passes/Cargo.toml
+++ b/compiler/rustc_ast_passes/Cargo.toml
@@ -5,7 +5,7 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-itertools.workspace = true
+itertools = "0.12"
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_pretty = { path = "../rustc_ast_pretty" }
@@ -18,5 +18,5 @@ rustc_macros = { path = "../rustc_macros" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
-thin-vec.workspace = true
+thin-vec = "0.2.12"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_ast_passes/messages.ftl b/compiler/rustc_ast_passes/messages.ftl
index a95f1443968..e5f1fcdc4b4 100644
--- a/compiler/rustc_ast_passes/messages.ftl
+++ b/compiler/rustc_ast_passes/messages.ftl
@@ -57,7 +57,7 @@ ast_passes_auto_super_lifetime = auto traits cannot have super traits or lifetim
     .label = {ast_passes_auto_super_lifetime}
     .suggestion = remove the super traits or lifetime bounds
 
-ast_passes_bad_c_variadic = only foreign, `unsafe extern "C"`, or `unsafe extern "C-unwind"` functions may have a C-variadic arg
+ast_passes_bad_c_variadic = defining functions with C-variadic arguments is only allowed for free functions with the "C" or "C-unwind" calling convention
 
 ast_passes_body_in_extern = incorrect `{$kind}` inside `extern` block
     .cannot_have = cannot have a body
diff --git a/compiler/rustc_ast_pretty/Cargo.toml b/compiler/rustc_ast_pretty/Cargo.toml
index 0c7e55305b4..b704040be96 100644
--- a/compiler/rustc_ast_pretty/Cargo.toml
+++ b/compiler/rustc_ast_pretty/Cargo.toml
@@ -5,7 +5,7 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-itertools.workspace = true
+itertools = "0.12"
 rustc_ast = { path = "../rustc_ast" }
 rustc_lexer = { path = "../rustc_lexer" }
 rustc_span = { path = "../rustc_span" }
@@ -13,5 +13,5 @@ rustc_span = { path = "../rustc_span" }
 
 [dev-dependencies]
 # tidy-alphabetical-start
-thin-vec.workspace = true
+thin-vec = "0.2.12"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_ast_pretty/src/pprust/state.rs b/compiler/rustc_ast_pretty/src/pprust/state.rs
index a056ce3e29d..41b520b04c9 100644
--- a/compiler/rustc_ast_pretty/src/pprust/state.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/state.rs
@@ -1769,7 +1769,7 @@ impl<'a> State<'a> {
                     },
                     |f| f.pat.span,
                 );
-                if let ast::PatFieldsRest::Rest | ast::PatFieldsRest::Recovered(_) = etc {
+                if let ast::PatFieldsRest::Rest(_) | ast::PatFieldsRest::Recovered(_) = etc {
                     if !fields.is_empty() {
                         self.word_space(",");
                     }
diff --git a/compiler/rustc_attr_parsing/Cargo.toml b/compiler/rustc_attr_parsing/Cargo.toml
index 8bfde43fd33..79193f394fe 100644
--- a/compiler/rustc_attr_parsing/Cargo.toml
+++ b/compiler/rustc_attr_parsing/Cargo.toml
@@ -18,5 +18,5 @@ rustc_parse = { path = "../rustc_parse" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
-thin-vec.workspace = true
+thin-vec = "0.2.12"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_attr_parsing/messages.ftl b/compiler/rustc_attr_parsing/messages.ftl
index b8a748563d5..7fa1293463c 100644
--- a/compiler/rustc_attr_parsing/messages.ftl
+++ b/compiler/rustc_attr_parsing/messages.ftl
@@ -151,7 +151,7 @@ attr_parsing_unrecognized_repr_hint =
 attr_parsing_unstable_cfg_target_compact =
     compact `cfg(target(..))` is experimental and subject to change
 
-attr_parsing_unstable_feature_bound_incompatible_stability = Item annotated with `#[unstable_feature_bound]` should not be stable
+attr_parsing_unstable_feature_bound_incompatible_stability = item annotated with `#[unstable_feature_bound]` should not be stable
     .help = If this item is meant to be stable, do not use any functions annotated with `#[unstable_feature_bound]`. Otherwise, mark this item as unstable with `#[unstable]`
 
 attr_parsing_unsupported_literal_cfg_boolean =
diff --git a/compiler/rustc_borrowck/Cargo.toml b/compiler/rustc_borrowck/Cargo.toml
index 5f9dc41766b..9e7d55180a2 100644
--- a/compiler/rustc_borrowck/Cargo.toml
+++ b/compiler/rustc_borrowck/Cargo.toml
@@ -5,9 +5,9 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-either.workspace = true
-itertools.workspace = true
-polonius-engine.workspace = true
+either = "1.5.0"
+itertools = "0.12"
+polonius-engine = "0.13.0"
 rustc_abi = { path = "../rustc_abi" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
@@ -25,5 +25,5 @@ rustc_span = { path = "../rustc_span" }
 rustc_trait_selection = { path = "../rustc_trait_selection" }
 rustc_traits = { path = "../rustc_traits" }
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
-tracing.workspace = true
+tracing = "0.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs b/compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs
index 72615cb33b3..95c5366a6c8 100644
--- a/compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs
@@ -503,7 +503,16 @@ pub(crate) fn apply_computed_concrete_opaque_types<'tcx>(
     let mut errors = Vec::new();
     for &(key, hidden_type) in opaque_types {
         let Some(expected) = get_concrete_opaque_type(concrete_opaque_types, key.def_id) else {
-            assert!(tcx.use_typing_mode_borrowck(), "non-defining use in defining scope");
+            if !tcx.use_typing_mode_borrowck() {
+                if let ty::Alias(ty::Opaque, alias_ty) = hidden_type.ty.kind()
+                    && alias_ty.def_id == key.def_id.to_def_id()
+                    && alias_ty.args == key.args
+                {
+                    continue;
+                } else {
+                    unreachable!("non-defining use in defining scope");
+                }
+            }
             errors.push(DeferredOpaqueTypeError::NonDefiningUseInDefiningScope {
                 span: hidden_type.span,
                 opaque_type_key: key,
diff --git a/compiler/rustc_builtin_macros/Cargo.toml b/compiler/rustc_builtin_macros/Cargo.toml
index 9ca44d67150..e56b9e641a1 100644
--- a/compiler/rustc_builtin_macros/Cargo.toml
+++ b/compiler/rustc_builtin_macros/Cargo.toml
@@ -30,6 +30,6 @@ rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
-thin-vec.workspace = true
-tracing.workspace = true
+thin-vec = "0.2.12"
+tracing = "0.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_codegen_cranelift/scripts/test_rustc_tests.sh b/compiler/rustc_codegen_cranelift/scripts/test_rustc_tests.sh
index 52e02c857c7..62f1cc6a893 100755
--- a/compiler/rustc_codegen_cranelift/scripts/test_rustc_tests.sh
+++ b/compiler/rustc_codegen_cranelift/scripts/test_rustc_tests.sh
@@ -121,7 +121,7 @@ rm tests/ui/abi/large-byval-align.rs # exceeds implementation limit of Cranelift
 # ============================================================
 rm -r tests/run-make/remap-path-prefix-dwarf # requires llvm-dwarfdump
 rm -r tests/run-make/strip # same
-rm -r tests/run-make/compiler-builtins # Expects lib/rustlib/src/rust to contains the standard library source
+rm -r tests/run-make-cargo/compiler-builtins # Expects lib/rustlib/src/rust to contains the standard library source
 rm -r tests/run-make/translation # same
 rm -r tests/run-make/missing-unstable-trait-bound # This disables support for unstable features, but running cg_clif needs some unstable features
 rm -r tests/run-make/const-trait-stable-toolchain # same
@@ -166,5 +166,5 @@ index 073116933bd..c3e4578204d 100644
 EOF
 
 echo "[TEST] rustc test suite"
-./x.py test --stage 0 --test-args=--no-capture tests/{codegen-units,run-make,ui,incremental}
+./x.py test --stage 0 --test-args=--no-capture tests/{codegen-units,run-make,run-make-cargo,ui,incremental}
 popd
diff --git a/compiler/rustc_codegen_gcc/build_system/src/test.rs b/compiler/rustc_codegen_gcc/build_system/src/test.rs
index 3dd3fce2eec..1823aa71f40 100644
--- a/compiler/rustc_codegen_gcc/build_system/src/test.rs
+++ b/compiler/rustc_codegen_gcc/build_system/src/test.rs
@@ -1083,11 +1083,12 @@ where
 
 fn test_rustc(env: &Env, args: &TestArg) -> Result<(), String> {
     test_rustc_inner(env, args, |_| Ok(false), false, "run-make")?;
+    test_rustc_inner(env, args, |_| Ok(false), false, "run-make-cargo")?;
     test_rustc_inner(env, args, |_| Ok(false), false, "ui")
 }
 
 fn test_failing_rustc(env: &Env, args: &TestArg) -> Result<(), String> {
-    let result1 = test_rustc_inner(
+    let run_make_result = test_rustc_inner(
         env,
         args,
         retain_files_callback("tests/failing-run-make-tests.txt", "run-make"),
@@ -1095,7 +1096,15 @@ fn test_failing_rustc(env: &Env, args: &TestArg) -> Result<(), String> {
         "run-make",
     );
 
-    let result2 = test_rustc_inner(
+    let run_make_cargo_result = test_rustc_inner(
+        env,
+        args,
+        retain_files_callback("tests/failing-run-make-tests.txt", "run-make-cargo"),
+        false,
+        "run-make",
+    );
+
+    let ui_result = test_rustc_inner(
         env,
         args,
         retain_files_callback("tests/failing-ui-tests.txt", "ui"),
@@ -1103,7 +1112,7 @@ fn test_failing_rustc(env: &Env, args: &TestArg) -> Result<(), String> {
         "ui",
     );
 
-    result1.and(result2)
+    run_make_result.and(run_make_cargo_result).and(ui_result)
 }
 
 fn test_successful_rustc(env: &Env, args: &TestArg) -> Result<(), String> {
@@ -1120,6 +1129,13 @@ fn test_successful_rustc(env: &Env, args: &TestArg) -> Result<(), String> {
         remove_files_callback("tests/failing-run-make-tests.txt", "run-make"),
         false,
         "run-make",
+    )?;
+    test_rustc_inner(
+        env,
+        args,
+        remove_files_callback("tests/failing-run-make-tests.txt", "run-make-cargo"),
+        false,
+        "run-make-cargo",
     )
 }
 
diff --git a/compiler/rustc_codegen_gcc/src/back/lto.rs b/compiler/rustc_codegen_gcc/src/back/lto.rs
index fcee6b6df62..d29bba2570f 100644
--- a/compiler/rustc_codegen_gcc/src/back/lto.rs
+++ b/compiler/rustc_codegen_gcc/src/back/lto.rs
@@ -204,7 +204,7 @@ fn fat_lto(
             let path = tmp_path.path().to_path_buf().join(&module.name);
             let path = path.to_str().expect("path");
             let context = &module.module_llvm.context;
-            let config = cgcx.config(module.kind);
+            let config = &cgcx.module_config;
             // NOTE: we need to set the optimization level here in order for LTO to do its job.
             context.set_optimization_level(to_gcc_opt_level(config.opt_level));
             context.add_command_line_option("-flto=auto");
@@ -305,12 +305,9 @@ pub(crate) fn run_thin(
     )
 }
 
-pub(crate) fn prepare_thin(
-    module: ModuleCodegen<GccContext>,
-    _emit_summary: bool,
-) -> (String, ThinBuffer) {
+pub(crate) fn prepare_thin(module: ModuleCodegen<GccContext>) -> (String, ThinBuffer) {
     let name = module.name;
-    //let buffer = ThinBuffer::new(module.module_llvm.context, true, emit_summary);
+    //let buffer = ThinBuffer::new(module.module_llvm.context, true);
     let buffer = ThinBuffer::new(&module.module_llvm.context);
     (name, buffer)
 }
@@ -650,10 +647,6 @@ impl ThinBufferMethods for ThinBuffer {
     fn data(&self) -> &[u8] {
         &[]
     }
-
-    fn thin_link_data(&self) -> &[u8] {
-        unimplemented!();
-    }
 }
 
 pub struct ThinData; //(Arc<TempDir>);
diff --git a/compiler/rustc_codegen_gcc/src/lib.rs b/compiler/rustc_codegen_gcc/src/lib.rs
index 2d7df79ba95..f76f933cad4 100644
--- a/compiler/rustc_codegen_gcc/src/lib.rs
+++ b/compiler/rustc_codegen_gcc/src/lib.rs
@@ -408,11 +408,8 @@ impl WriteBackendMethods for GccCodegenBackend {
         back::write::codegen(cgcx, module, config)
     }
 
-    fn prepare_thin(
-        module: ModuleCodegen<Self::Module>,
-        emit_summary: bool,
-    ) -> (String, Self::ThinBuffer) {
-        back::lto::prepare_thin(module, emit_summary)
+    fn prepare_thin(module: ModuleCodegen<Self::Module>) -> (String, Self::ThinBuffer) {
+        back::lto::prepare_thin(module)
     }
 
     fn serialize_module(_module: ModuleCodegen<Self::Module>) -> (String, Self::ModuleBuffer) {
diff --git a/compiler/rustc_codegen_llvm/Cargo.toml b/compiler/rustc_codegen_llvm/Cargo.toml
index b04310f3d54..2d11628250c 100644
--- a/compiler/rustc_codegen_llvm/Cargo.toml
+++ b/compiler/rustc_codegen_llvm/Cargo.toml
@@ -8,15 +8,15 @@ test = false
 
 [dependencies]
 # tidy-alphabetical-start
-bitflags.workspace = true
+bitflags = "2.4.1"
 # To avoid duplicate dependencies, this should match the version of gimli used
 # by `rustc_codegen_ssa` via its `thorin-dwp` dependency.
 gimli = "0.31"
-itertools.workspace = true
-libc.workspace = true
-measureme.workspace = true
+itertools = "0.12"
+libc = "0.2"
+measureme = "12.0.1"
 object = { version = "0.37.0", default-features = false, features = ["std", "read"] }
-rustc-demangle.workspace = true
+rustc-demangle = "0.1.21"
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_codegen_ssa = { path = "../rustc_codegen_ssa" }
@@ -38,9 +38,9 @@ rustc_span = { path = "../rustc_span" }
 rustc_symbol_mangling = { path = "../rustc_symbol_mangling" }
 rustc_target = { path = "../rustc_target" }
 serde = { version = "1", features = ["derive"] }
-serde_json.workspace = true
+serde_json = "1"
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
-tracing.workspace = true
+tracing = "0.1"
 # tidy-alphabetical-end
 
 [features]
diff --git a/compiler/rustc_codegen_llvm/src/attributes.rs b/compiler/rustc_codegen_llvm/src/attributes.rs
index 5affb26483a..573c51a9539 100644
--- a/compiler/rustc_codegen_llvm/src/attributes.rs
+++ b/compiler/rustc_codegen_llvm/src/attributes.rs
@@ -29,8 +29,18 @@ pub(crate) fn apply_to_callsite(callsite: &Value, idx: AttributePlace, attrs: &[
 }
 
 /// Get LLVM attribute for the provided inline heuristic.
-#[inline]
-fn inline_attr<'ll>(cx: &CodegenCx<'ll, '_>, inline: InlineAttr) -> Option<&'ll Attribute> {
+pub(crate) fn inline_attr<'ll, 'tcx>(
+    cx: &CodegenCx<'ll, 'tcx>,
+    instance: ty::Instance<'tcx>,
+) -> Option<&'ll Attribute> {
+    // `optnone` requires `noinline`
+    let codegen_fn_attrs = cx.tcx.codegen_fn_attrs(instance.def_id());
+    let inline = match (codegen_fn_attrs.inline, &codegen_fn_attrs.optimize) {
+        (_, OptimizeAttr::DoNotOptimize) => InlineAttr::Never,
+        (InlineAttr::None, _) if instance.def.requires_inline(cx.tcx) => InlineAttr::Hint,
+        (inline, _) => inline,
+    };
+
     if !cx.tcx.sess.opts.unstable_opts.inline_llvm {
         // disable LLVM inlining
         return Some(AttributeKind::NoInline.create_attr(cx.llcx));
@@ -286,6 +296,19 @@ pub(crate) fn tune_cpu_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> Option<&'ll Attribu
         .map(|tune_cpu| llvm::CreateAttrStringValue(cx.llcx, "tune-cpu", tune_cpu))
 }
 
+/// Get the `target-features` LLVM attribute.
+pub(crate) fn target_features_attr<'ll>(
+    cx: &CodegenCx<'ll, '_>,
+    function_features: Vec<String>,
+) -> Option<&'ll Attribute> {
+    let global_features = cx.tcx.global_backend_features(()).iter().map(String::as_str);
+    let function_features = function_features.iter().map(String::as_str);
+    let target_features =
+        global_features.chain(function_features).intersperse(",").collect::<String>();
+    (!target_features.is_empty())
+        .then(|| llvm::CreateAttrStringValue(cx.llcx, "target-features", &target_features))
+}
+
 /// Get the `NonLazyBind` LLVM attribute,
 /// if the codegen options allow skipping the PLT.
 pub(crate) fn non_lazy_bind_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> Option<&'ll Attribute> {
@@ -346,14 +369,6 @@ pub(crate) fn llfn_attrs_from_instance<'ll, 'tcx>(
         OptimizeAttr::Speed => {}
     }
 
-    // `optnone` requires `noinline`
-    let inline = match (codegen_fn_attrs.inline, &codegen_fn_attrs.optimize) {
-        (_, OptimizeAttr::DoNotOptimize) => InlineAttr::Never,
-        (InlineAttr::None, _) if instance.def.requires_inline(cx.tcx) => InlineAttr::Hint,
-        (inline, _) => inline,
-    };
-    to_add.extend(inline_attr(cx, inline));
-
     if cx.sess().must_emit_unwind_tables() {
         to_add.push(uwtable_attr(cx.llcx, cx.sess().opts.unstable_opts.use_sync_unwind));
     }
@@ -488,6 +503,14 @@ pub(crate) fn llfn_attrs_from_instance<'ll, 'tcx>(
     let function_features =
         codegen_fn_attrs.target_features.iter().map(|f| f.name.as_str()).collect::<Vec<&str>>();
 
+    // Apply function attributes as per usual if there are no user defined
+    // target features otherwise this will get applied at the callsite.
+    if function_features.is_empty() {
+        if let Some(inline_attr) = inline_attr(cx, instance) {
+            to_add.push(inline_attr);
+        }
+    }
+
     let function_features = function_features
         .iter()
         // Convert to LLVMFeatures and filter out unavailable ones
@@ -513,13 +536,7 @@ pub(crate) fn llfn_attrs_from_instance<'ll, 'tcx>(
         }
     }
 
-    let global_features = cx.tcx.global_backend_features(()).iter().map(|s| s.as_str());
-    let function_features = function_features.iter().map(|s| s.as_str());
-    let target_features: String =
-        global_features.chain(function_features).intersperse(",").collect();
-    if !target_features.is_empty() {
-        to_add.push(llvm::CreateAttrStringValue(cx.llcx, "target-features", &target_features));
-    }
+    to_add.extend(target_features_attr(cx, function_features));
 
     attributes::apply_to_llfn(llfn, Function, &to_add);
 }
diff --git a/compiler/rustc_codegen_llvm/src/back/lto.rs b/compiler/rustc_codegen_llvm/src/back/lto.rs
index fc38c4f3e51..f571716d9dd 100644
--- a/compiler/rustc_codegen_llvm/src/back/lto.rs
+++ b/compiler/rustc_codegen_llvm/src/back/lto.rs
@@ -43,9 +43,7 @@ fn prepare_lto(
         .map(|symbol| CString::new(symbol.to_owned()).unwrap())
         .collect::<Vec<CString>>();
 
-    if cgcx.regular_module_config.instrument_coverage
-        || cgcx.regular_module_config.pgo_gen.enabled()
-    {
+    if cgcx.module_config.instrument_coverage || cgcx.module_config.pgo_gen.enabled() {
         // These are weak symbols that point to the profile version and the
         // profile name, which need to be treated as exported so LTO doesn't nix
         // them.
@@ -55,15 +53,15 @@ fn prepare_lto(
         symbols_below_threshold.extend(PROFILER_WEAK_SYMBOLS.iter().map(|&sym| sym.to_owned()));
     }
 
-    if cgcx.regular_module_config.sanitizer.contains(SanitizerSet::MEMORY) {
+    if cgcx.module_config.sanitizer.contains(SanitizerSet::MEMORY) {
         let mut msan_weak_symbols = Vec::new();
 
         // Similar to profiling, preserve weak msan symbol during LTO.
-        if cgcx.regular_module_config.sanitizer_recover.contains(SanitizerSet::MEMORY) {
+        if cgcx.module_config.sanitizer_recover.contains(SanitizerSet::MEMORY) {
             msan_weak_symbols.push(c"__msan_keep_going");
         }
 
-        if cgcx.regular_module_config.sanitizer_memory_track_origins != 0 {
+        if cgcx.module_config.sanitizer_memory_track_origins != 0 {
             msan_weak_symbols.push(c"__msan_track_origins");
         }
 
@@ -187,12 +185,9 @@ pub(crate) fn run_thin(
     thin_lto(cgcx, dcx, modules, upstream_modules, cached_modules, &symbols_below_threshold)
 }
 
-pub(crate) fn prepare_thin(
-    module: ModuleCodegen<ModuleLlvm>,
-    emit_summary: bool,
-) -> (String, ThinBuffer) {
+pub(crate) fn prepare_thin(module: ModuleCodegen<ModuleLlvm>) -> (String, ThinBuffer) {
     let name = module.name;
-    let buffer = ThinBuffer::new(module.module_llvm.llmod(), true, emit_summary);
+    let buffer = ThinBuffer::new(module.module_llvm.llmod(), true);
     (name, buffer)
 }
 
@@ -583,7 +578,7 @@ pub(crate) fn run_pass_manager(
     thin: bool,
 ) {
     let _timer = cgcx.prof.generic_activity_with_arg("LLVM_lto_optimize", &*module.name);
-    let config = cgcx.config(module.kind);
+    let config = &cgcx.module_config;
 
     // Now we have one massive module inside of llmod. Time to run the
     // LTO-specific optimization passes that LLVM provides.
@@ -689,9 +684,9 @@ unsafe impl Send for ThinBuffer {}
 unsafe impl Sync for ThinBuffer {}
 
 impl ThinBuffer {
-    pub(crate) fn new(m: &llvm::Module, is_thin: bool, emit_summary: bool) -> ThinBuffer {
+    pub(crate) fn new(m: &llvm::Module, is_thin: bool) -> ThinBuffer {
         unsafe {
-            let buffer = llvm::LLVMRustThinLTOBufferCreate(m, is_thin, emit_summary);
+            let buffer = llvm::LLVMRustThinLTOBufferCreate(m, is_thin);
             ThinBuffer(buffer)
         }
     }
@@ -700,21 +695,21 @@ impl ThinBuffer {
         let mut ptr = NonNull::new(ptr).unwrap();
         ThinBuffer(unsafe { ptr.as_mut() })
     }
-}
 
-impl ThinBufferMethods for ThinBuffer {
-    fn data(&self) -> &[u8] {
+    pub(crate) fn thin_link_data(&self) -> &[u8] {
         unsafe {
-            let ptr = llvm::LLVMRustThinLTOBufferPtr(self.0) as *const _;
-            let len = llvm::LLVMRustThinLTOBufferLen(self.0);
+            let ptr = llvm::LLVMRustThinLTOBufferThinLinkDataPtr(self.0) as *const _;
+            let len = llvm::LLVMRustThinLTOBufferThinLinkDataLen(self.0);
             slice::from_raw_parts(ptr, len)
         }
     }
+}
 
-    fn thin_link_data(&self) -> &[u8] {
+impl ThinBufferMethods for ThinBuffer {
+    fn data(&self) -> &[u8] {
         unsafe {
-            let ptr = llvm::LLVMRustThinLTOBufferThinLinkDataPtr(self.0) as *const _;
-            let len = llvm::LLVMRustThinLTOBufferThinLinkDataLen(self.0);
+            let ptr = llvm::LLVMRustThinLTOBufferPtr(self.0) as *const _;
+            let len = llvm::LLVMRustThinLTOBufferLen(self.0);
             slice::from_raw_parts(ptr, len)
         }
     }
@@ -745,7 +740,7 @@ pub(crate) fn optimize_thin_module(
     let module_llvm = ModuleLlvm::parse(cgcx, module_name, thin_module.data(), dcx);
     let mut module = ModuleCodegen::new_regular(thin_module.name(), module_llvm);
     // Given that the newly created module lacks a thinlto buffer for embedding, we need to re-add it here.
-    if cgcx.config(ModuleKind::Regular).embed_bitcode() {
+    if cgcx.module_config.embed_bitcode() {
         module.thin_lto_buffer = Some(thin_module.data().to_vec());
     }
     {
diff --git a/compiler/rustc_codegen_llvm/src/back/write.rs b/compiler/rustc_codegen_llvm/src/back/write.rs
index 7ea2ae6673b..423f0da4878 100644
--- a/compiler/rustc_codegen_llvm/src/back/write.rs
+++ b/compiler/rustc_codegen_llvm/src/back/write.rs
@@ -837,7 +837,7 @@ pub(crate) fn codegen(
                         "LLVM_module_codegen_make_bitcode",
                         &*module.name,
                     );
-                    ThinBuffer::new(llmod, config.emit_thin_lto, false)
+                    ThinBuffer::new(llmod, config.emit_thin_lto)
                 };
                 let data = thin.data();
                 let _timer = cgcx
diff --git a/compiler/rustc_codegen_llvm/src/builder.rs b/compiler/rustc_codegen_llvm/src/builder.rs
index 37379586d58..7d0691366e6 100644
--- a/compiler/rustc_codegen_llvm/src/builder.rs
+++ b/compiler/rustc_codegen_llvm/src/builder.rs
@@ -1392,7 +1392,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
     fn call(
         &mut self,
         llty: &'ll Type,
-        fn_attrs: Option<&CodegenFnAttrs>,
+        fn_call_attrs: Option<&CodegenFnAttrs>,
         fn_abi: Option<&FnAbi<'tcx, Ty<'tcx>>>,
         llfn: &'ll Value,
         args: &[&'ll Value],
@@ -1409,10 +1409,10 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         }
 
         // Emit CFI pointer type membership test
-        self.cfi_type_test(fn_attrs, fn_abi, instance, llfn);
+        self.cfi_type_test(fn_call_attrs, fn_abi, instance, llfn);
 
         // Emit KCFI operand bundle
-        let kcfi_bundle = self.kcfi_operand_bundle(fn_attrs, fn_abi, instance, llfn);
+        let kcfi_bundle = self.kcfi_operand_bundle(fn_call_attrs, fn_abi, instance, llfn);
         if let Some(kcfi_bundle) = kcfi_bundle.as_ref().map(|b| b.as_ref()) {
             bundles.push(kcfi_bundle);
         }
@@ -1429,6 +1429,29 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
                 c"".as_ptr(),
             )
         };
+
+        if let Some(instance) = instance {
+            // Attributes on the function definition being called
+            let fn_defn_attrs = self.cx.tcx.codegen_fn_attrs(instance.def_id());
+            if let Some(fn_call_attrs) = fn_call_attrs
+                && !fn_call_attrs.target_features.is_empty()
+                // If there is an inline attribute and a target feature that matches
+                // we will add the attribute to the callsite otherwise we'll omit
+                // this and not add the attribute to prevent soundness issues.
+                && let Some(inlining_rule) = attributes::inline_attr(&self.cx, instance)
+                && self.cx.tcx.is_target_feature_call_safe(
+                    &fn_call_attrs.target_features,
+                    &fn_defn_attrs.target_features,
+                )
+            {
+                attributes::apply_to_callsite(
+                    call,
+                    llvm::AttributePlace::Function,
+                    &[inlining_rule],
+                );
+            }
+        }
+
         if let Some(fn_abi) = fn_abi {
             fn_abi.apply_attrs_callsite(self, call);
         }
diff --git a/compiler/rustc_codegen_llvm/src/builder/gpu_offload.rs b/compiler/rustc_codegen_llvm/src/builder/gpu_offload.rs
index 1280ab1442a..0737a18384b 100644
--- a/compiler/rustc_codegen_llvm/src/builder/gpu_offload.rs
+++ b/compiler/rustc_codegen_llvm/src/builder/gpu_offload.rs
@@ -193,7 +193,7 @@ fn gen_define_handling<'ll>(
     // reference) types.
     let num_ptr_types = types
         .iter()
-        .map(|&x| matches!(cx.type_kind(x), rustc_codegen_ssa::common::TypeKind::Pointer))
+        .filter(|&x| matches!(cx.type_kind(x), rustc_codegen_ssa::common::TypeKind::Pointer))
         .count();
 
     // We do not know their size anymore at this level, so hardcode a placeholder.
diff --git a/compiler/rustc_codegen_llvm/src/context.rs b/compiler/rustc_codegen_llvm/src/context.rs
index 4fd6110ac4a..a69fa54a54a 100644
--- a/compiler/rustc_codegen_llvm/src/context.rs
+++ b/compiler/rustc_codegen_llvm/src/context.rs
@@ -217,6 +217,10 @@ pub(crate) unsafe fn create_module<'ll>(
             // LLVM 22.0 updated the default layout on avr: https://github.com/llvm/llvm-project/pull/153010
             target_data_layout = target_data_layout.replace("n8:16", "n8")
         }
+        if sess.target.arch == "nvptx64" {
+            // LLVM 22 updated the NVPTX layout to indicate 256-bit vector load/store: https://github.com/llvm/llvm-project/pull/155198
+            target_data_layout = target_data_layout.replace("-i256:256", "");
+        }
     }
 
     // Ensure the data-layout values hardcoded remain the defaults.
@@ -849,7 +853,7 @@ impl<'ll, 'tcx> MiscCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
     fn declare_c_main(&self, fn_type: Self::Type) -> Option<Self::Function> {
         let entry_name = self.sess().target.entry_name.as_ref();
         if self.get_declared_value(entry_name).is_none() {
-            Some(self.declare_entry_fn(
+            let llfn = self.declare_entry_fn(
                 entry_name,
                 llvm::CallConv::from_conv(
                     self.sess().target.entry_abi,
@@ -857,7 +861,13 @@ impl<'ll, 'tcx> MiscCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
                 ),
                 llvm::UnnamedAddr::Global,
                 fn_type,
-            ))
+            );
+            attributes::apply_to_llfn(
+                llfn,
+                llvm::AttributePlace::Function,
+                attributes::target_features_attr(self, vec![]).as_slice(),
+            );
+            Some(llfn)
         } else {
             // If the symbol already exists, it is an error: for example, the user wrote
             // #[no_mangle] extern "C" fn main(..) {..}
diff --git a/compiler/rustc_codegen_llvm/src/intrinsic.rs b/compiler/rustc_codegen_llvm/src/intrinsic.rs
index 49d3dedbeab..85f71f331a4 100644
--- a/compiler/rustc_codegen_llvm/src/intrinsic.rs
+++ b/compiler/rustc_codegen_llvm/src/intrinsic.rs
@@ -383,7 +383,9 @@ impl<'ll, 'tcx> IntrinsicCallBuilderMethods<'tcx> for Builder<'_, 'll, 'tcx> {
             | sym::rotate_left
             | sym::rotate_right
             | sym::saturating_add
-            | sym::saturating_sub => {
+            | sym::saturating_sub
+            | sym::unchecked_funnel_shl
+            | sym::unchecked_funnel_shr => {
                 let ty = args[0].layout.ty;
                 if !ty.is_integral() {
                     tcx.dcx().emit_err(InvalidMonomorphization::BasicIntegerType {
@@ -424,18 +426,26 @@ impl<'ll, 'tcx> IntrinsicCallBuilderMethods<'tcx> for Builder<'_, 'll, 'tcx> {
                     sym::bitreverse => {
                         self.call_intrinsic("llvm.bitreverse", &[llty], &[args[0].immediate()])
                     }
-                    sym::rotate_left | sym::rotate_right => {
-                        let is_left = name == sym::rotate_left;
-                        let val = args[0].immediate();
-                        let raw_shift = args[1].immediate();
-                        // rotate = funnel shift with first two args the same
+                    sym::rotate_left
+                    | sym::rotate_right
+                    | sym::unchecked_funnel_shl
+                    | sym::unchecked_funnel_shr => {
+                        let is_left = name == sym::rotate_left || name == sym::unchecked_funnel_shl;
+                        let lhs = args[0].immediate();
+                        let (rhs, raw_shift) =
+                            if name == sym::rotate_left || name == sym::rotate_right {
+                                // rotate = funnel shift with first two args the same
+                                (lhs, args[1].immediate())
+                            } else {
+                                (args[1].immediate(), args[2].immediate())
+                            };
                         let llvm_name = format!("llvm.fsh{}", if is_left { 'l' } else { 'r' });
 
                         // llvm expects shift to be the same type as the values, but rust
                         // always uses `u32`.
-                        let raw_shift = self.intcast(raw_shift, self.val_ty(val), false);
+                        let raw_shift = self.intcast(raw_shift, self.val_ty(lhs), false);
 
-                        self.call_intrinsic(llvm_name, &[llty], &[val, val, raw_shift])
+                        self.call_intrinsic(llvm_name, &[llty], &[lhs, rhs, raw_shift])
                     }
                     sym::saturating_add | sym::saturating_sub => {
                         let is_add = name == sym::saturating_add;
diff --git a/compiler/rustc_codegen_llvm/src/lib.rs b/compiler/rustc_codegen_llvm/src/lib.rs
index 628cb34fd9e..6fb23d09843 100644
--- a/compiler/rustc_codegen_llvm/src/lib.rs
+++ b/compiler/rustc_codegen_llvm/src/lib.rs
@@ -211,11 +211,8 @@ impl WriteBackendMethods for LlvmCodegenBackend {
     ) -> CompiledModule {
         back::write::codegen(cgcx, module, config)
     }
-    fn prepare_thin(
-        module: ModuleCodegen<Self::Module>,
-        emit_summary: bool,
-    ) -> (String, Self::ThinBuffer) {
-        back::lto::prepare_thin(module, emit_summary)
+    fn prepare_thin(module: ModuleCodegen<Self::Module>) -> (String, Self::ThinBuffer) {
+        back::lto::prepare_thin(module)
     }
     fn serialize_module(module: ModuleCodegen<Self::Module>) -> (String, Self::ModuleBuffer) {
         (module.name, back::lto::ModuleBuffer::new(module.module_llvm.llmod()))
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index b66fc157b3c..0679f55ab7f 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -2602,7 +2602,6 @@ unsafe extern "C" {
     pub(crate) fn LLVMRustThinLTOBufferCreate(
         M: &Module,
         is_thin: bool,
-        emit_summary: bool,
     ) -> &'static mut ThinLTOBuffer;
     pub(crate) fn LLVMRustThinLTOBufferFree(M: &'static mut ThinLTOBuffer);
     pub(crate) fn LLVMRustThinLTOBufferPtr(M: &ThinLTOBuffer) -> *const c_char;
diff --git a/compiler/rustc_codegen_ssa/Cargo.toml b/compiler/rustc_codegen_ssa/Cargo.toml
index 6f87b5749c6..2dfbc581643 100644
--- a/compiler/rustc_codegen_ssa/Cargo.toml
+++ b/compiler/rustc_codegen_ssa/Cargo.toml
@@ -6,12 +6,12 @@ edition = "2024"
 [dependencies]
 # tidy-alphabetical-start
 ar_archive_writer = "0.5"
-bitflags.workspace = true
+bitflags = "2.4.1"
 bstr = "1.11.3"
 # `cc` updates often break things, so we pin it here. Cargo enforces "max 1 semver-compat version
 # per crate", so if you change this, you need to also change it in `rustc_llvm`.
 cc = "=1.2.16"
-itertools.workspace = true
+itertools = "0.12"
 pathdiff = "0.2.0"
 regex = "1.4"
 rustc_abi = { path = "../rustc_abi" }
@@ -37,18 +37,18 @@ rustc_span = { path = "../rustc_span" }
 rustc_symbol_mangling = { path = "../rustc_symbol_mangling" }
 rustc_target = { path = "../rustc_target" }
 rustc_trait_selection = { path = "../rustc_trait_selection" }
-serde_json.workspace = true
+serde_json = "1.0.59"
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
-tempfile.workspace = true
-thin-vec.workspace = true
+tempfile = "3.2"
+thin-vec = "0.2.12"
 thorin-dwp = "0.9"
-tracing.workspace = true
+tracing = "0.1"
 wasm-encoder = "0.219"
 # tidy-alphabetical-end
 
 [target.'cfg(unix)'.dependencies]
 # tidy-alphabetical-start
-libc.workspace = true
+libc = "0.2.50"
 # tidy-alphabetical-end
 
 [dependencies.object]
diff --git a/compiler/rustc_codegen_ssa/messages.ftl b/compiler/rustc_codegen_ssa/messages.ftl
index 44b9941691a..dd688b8b345 100644
--- a/compiler/rustc_codegen_ssa/messages.ftl
+++ b/compiler/rustc_codegen_ssa/messages.ftl
@@ -40,15 +40,15 @@ codegen_ssa_dynamic_linking_with_lto =
     .note = only 'staticlib', 'bin', and 'cdylib' outputs are supported with LTO
 
 codegen_ssa_error_calling_dlltool =
-    Error calling dlltool '{$dlltool_path}': {$error}
+    error calling dlltool '{$dlltool_path}': {$error}
 
 codegen_ssa_error_creating_import_library =
-    Error creating import library for {$lib_name}: {$error}
+    error creating import library for {$lib_name}: {$error}
 
 codegen_ssa_error_creating_remark_dir = failed to create remark directory: {$error}
 
 codegen_ssa_error_writing_def_file =
-    Error writing .DEF file: {$error}
+    error writing .DEF file: {$error}
 
 codegen_ssa_expected_name_value_pair = expected name value pair
 
@@ -264,9 +264,9 @@ codegen_ssa_shuffle_indices_evaluation = could not evaluate shuffle_indices at c
 
 codegen_ssa_specify_libraries_to_link = use the `-l` flag to specify native libraries to link
 
-codegen_ssa_static_library_native_artifacts = Link against the following native artifacts when linking against this static library. The order and any duplication can be significant on some platforms.
+codegen_ssa_static_library_native_artifacts = link against the following native artifacts when linking against this static library. The order and any duplication can be significant on some platforms.
 
-codegen_ssa_static_library_native_artifacts_to_file = Native artifacts to link against have been written to {$path}. The order and any duplication can be significant on some platforms.
+codegen_ssa_static_library_native_artifacts_to_file = native artifacts to link against have been written to {$path}. The order and any duplication can be significant on some platforms.
 
 codegen_ssa_stripping_debug_info_failed = stripping debug info with `{$util}` failed: {$status}
     .note = {$output}
@@ -364,13 +364,13 @@ codegen_ssa_unable_to_run = unable to run `{$util}`: {$error}
 
 codegen_ssa_unable_to_run_dsymutil = unable to run `dsymutil`: {$error}
 
-codegen_ssa_unable_to_write_debugger_visualizer = Unable to write debugger visualizer file `{$path}`: {$error}
+codegen_ssa_unable_to_write_debugger_visualizer = unable to write debugger visualizer file `{$path}`: {$error}
 
 codegen_ssa_unexpected_parameter_name = unexpected parameter name
     .label = expected `{$prefix_nops}` or `{$entry_nops}`
 
 codegen_ssa_unknown_archive_kind =
-    Don't know how to build archive of type: {$kind}
+    don't know how to build archive of type: {$kind}
 
 codegen_ssa_unknown_ctarget_feature =
     unknown and unstable feature specified for `-Ctarget-feature`: `{$feature}`
diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs
index 19c919c0e4e..48b01ea2df1 100644
--- a/compiler/rustc_codegen_ssa/src/back/link.rs
+++ b/compiler/rustc_codegen_ssa/src/back/link.rs
@@ -58,6 +58,7 @@ use super::linker::{self, Linker};
 use super::metadata::{MetadataPosition, create_wrapper_file};
 use super::rpath::{self, RPathConfig};
 use super::{apple, versioned_llvm_target};
+use crate::base::needs_allocator_shim_for_linking;
 use crate::{
     CodegenResults, CompiledModule, CrateInfo, NativeLib, errors, looks_like_rust_object_file,
 };
@@ -2080,9 +2081,17 @@ fn add_local_crate_regular_objects(cmd: &mut dyn Linker, codegen_results: &Codeg
 }
 
 /// Add object files for allocator code linked once for the whole crate tree.
-fn add_local_crate_allocator_objects(cmd: &mut dyn Linker, codegen_results: &CodegenResults) {
-    if let Some(obj) = codegen_results.allocator_module.as_ref().and_then(|m| m.object.as_ref()) {
-        cmd.add_object(obj);
+fn add_local_crate_allocator_objects(
+    cmd: &mut dyn Linker,
+    codegen_results: &CodegenResults,
+    crate_type: CrateType,
+) {
+    if needs_allocator_shim_for_linking(&codegen_results.crate_info.dependency_formats, crate_type)
+    {
+        if let Some(obj) = codegen_results.allocator_module.as_ref().and_then(|m| m.object.as_ref())
+        {
+            cmd.add_object(obj);
+        }
     }
 }
 
@@ -2281,7 +2290,7 @@ fn linker_with_args(
         codegen_results,
         metadata,
     );
-    add_local_crate_allocator_objects(cmd, codegen_results);
+    add_local_crate_allocator_objects(cmd, codegen_results, crate_type);
 
     // Avoid linking to dynamic libraries unless they satisfy some undefined symbols
     // at the point at which they are specified on the command line.
diff --git a/compiler/rustc_codegen_ssa/src/back/linker.rs b/compiler/rustc_codegen_ssa/src/back/linker.rs
index df1e91b12f9..a2efd420a32 100644
--- a/compiler/rustc_codegen_ssa/src/back/linker.rs
+++ b/compiler/rustc_codegen_ssa/src/back/linker.rs
@@ -11,8 +11,9 @@ use rustc_metadata::{
 };
 use rustc_middle::bug;
 use rustc_middle::middle::dependency_format::Linkage;
-use rustc_middle::middle::exported_symbols;
-use rustc_middle::middle::exported_symbols::{ExportedSymbol, SymbolExportInfo, SymbolExportKind};
+use rustc_middle::middle::exported_symbols::{
+    self, ExportedSymbol, SymbolExportInfo, SymbolExportKind, SymbolExportLevel,
+};
 use rustc_middle::ty::TyCtxt;
 use rustc_session::Session;
 use rustc_session::config::{self, CrateType, DebugInfo, LinkerPluginLto, Lto, OptLevel, Strip};
@@ -22,6 +23,8 @@ use tracing::{debug, warn};
 
 use super::command::Command;
 use super::symbol_export;
+use crate::back::symbol_export::allocator_shim_symbols;
+use crate::base::needs_allocator_shim_for_linking;
 use crate::errors;
 
 #[cfg(test)]
@@ -1827,7 +1830,7 @@ fn exported_symbols_for_non_proc_macro(
     let export_threshold = symbol_export::crates_export_threshold(&[crate_type]);
     for_each_exported_symbols_include_dep(tcx, crate_type, |symbol, info, cnum| {
         // Do not export mangled symbols from cdylibs and don't attempt to export compiler-builtins
-        // from any cdylib. The latter doesn't work anyway as we use hidden visibility for
+        // from any dylib. The latter doesn't work anyway as we use hidden visibility for
         // compiler-builtins. Most linkers silently ignore it, but ld64 gives a warning.
         if info.level.is_below_threshold(export_threshold) && !tcx.is_compiler_builtins(cnum) {
             symbols.push((
@@ -1838,6 +1841,14 @@ fn exported_symbols_for_non_proc_macro(
         }
     });
 
+    // Mark allocator shim symbols as exported only if they were generated.
+    if export_threshold == SymbolExportLevel::Rust
+        && needs_allocator_shim_for_linking(tcx.dependency_formats(()), crate_type)
+        && tcx.allocator_kind(()).is_some()
+    {
+        symbols.extend(allocator_shim_symbols(tcx));
+    }
+
     symbols
 }
 
diff --git a/compiler/rustc_codegen_ssa/src/back/lto.rs b/compiler/rustc_codegen_ssa/src/back/lto.rs
index c95038375a1..e6df6a2469f 100644
--- a/compiler/rustc_codegen_ssa/src/back/lto.rs
+++ b/compiler/rustc_codegen_ssa/src/back/lto.rs
@@ -8,8 +8,9 @@ use rustc_middle::ty::TyCtxt;
 use rustc_session::config::{CrateType, Lto};
 use tracing::info;
 
-use crate::back::symbol_export::{self, symbol_name_for_instance_in_crate};
+use crate::back::symbol_export::{self, allocator_shim_symbols, symbol_name_for_instance_in_crate};
 use crate::back::write::CodegenContext;
+use crate::base::allocator_kind_for_codegen;
 use crate::errors::{DynamicLinkingWithLTO, LtoDisallowed, LtoDylib, LtoProcMacro};
 use crate::traits::*;
 
@@ -115,6 +116,11 @@ pub(super) fn exported_symbols_for_lto(
         }
     }
 
+    // Mark allocator shim symbols as exported only if they were generated.
+    if export_threshold == SymbolExportLevel::Rust && allocator_kind_for_codegen(tcx).is_some() {
+        symbols_below_threshold.extend(allocator_shim_symbols(tcx).map(|(name, _kind)| name));
+    }
+
     symbols_below_threshold
 }
 
diff --git a/compiler/rustc_codegen_ssa/src/back/symbol_export.rs b/compiler/rustc_codegen_ssa/src/back/symbol_export.rs
index d8a1480e911..b49e67217fb 100644
--- a/compiler/rustc_codegen_ssa/src/back/symbol_export.rs
+++ b/compiler/rustc_codegen_ssa/src/back/symbol_export.rs
@@ -18,7 +18,7 @@ use rustc_symbol_mangling::mangle_internal_symbol;
 use rustc_target::spec::TlsModel;
 use tracing::debug;
 
-use crate::base::allocator_kind_for_codegen;
+use crate::back::symbol_export;
 
 fn threshold(tcx: TyCtxt<'_>) -> SymbolExportLevel {
     crates_export_threshold(tcx.crate_types())
@@ -217,31 +217,6 @@ fn exported_non_generic_symbols_provider_local<'tcx>(
         ));
     }
 
-    // Mark allocator shim symbols as exported only if they were generated.
-    if allocator_kind_for_codegen(tcx).is_some() {
-        for symbol_name in ALLOCATOR_METHODS
-            .iter()
-            .map(|method| mangle_internal_symbol(tcx, global_fn_name(method.name).as_str()))
-            .chain([
-                mangle_internal_symbol(tcx, "__rust_alloc_error_handler"),
-                mangle_internal_symbol(tcx, OomStrategy::SYMBOL),
-                mangle_internal_symbol(tcx, NO_ALLOC_SHIM_IS_UNSTABLE),
-            ])
-        {
-            let exported_symbol = ExportedSymbol::NoDefId(SymbolName::new(tcx, &symbol_name));
-
-            symbols.push((
-                exported_symbol,
-                SymbolExportInfo {
-                    level: SymbolExportLevel::Rust,
-                    kind: SymbolExportKind::Text,
-                    used: false,
-                    rustc_std_internal_symbol: true,
-                },
-            ));
-        }
-    }
-
     // Sort so we get a stable incr. comp. hash.
     symbols.sort_by_cached_key(|s| s.0.symbol_name_for_local_instance(tcx));
 
@@ -516,6 +491,31 @@ pub(crate) fn provide(providers: &mut Providers) {
         upstream_monomorphizations_for_provider;
 }
 
+pub(crate) fn allocator_shim_symbols(
+    tcx: TyCtxt<'_>,
+) -> impl Iterator<Item = (String, SymbolExportKind)> {
+    ALLOCATOR_METHODS
+        .iter()
+        .map(move |method| mangle_internal_symbol(tcx, global_fn_name(method.name).as_str()))
+        .chain([
+            mangle_internal_symbol(tcx, "__rust_alloc_error_handler"),
+            mangle_internal_symbol(tcx, OomStrategy::SYMBOL),
+            mangle_internal_symbol(tcx, NO_ALLOC_SHIM_IS_UNSTABLE),
+        ])
+        .map(move |symbol_name| {
+            let exported_symbol = ExportedSymbol::NoDefId(SymbolName::new(tcx, &symbol_name));
+
+            (
+                symbol_export::exporting_symbol_name_for_instance_in_crate(
+                    tcx,
+                    exported_symbol,
+                    LOCAL_CRATE,
+                ),
+                SymbolExportKind::Text,
+            )
+        })
+}
+
 fn symbol_export_level(tcx: TyCtxt<'_>, sym_def_id: DefId) -> SymbolExportLevel {
     // We export anything that's not mangled at the "C" layer as it probably has
     // to do with ABI concerns. We do not, however, apply such treatment to
diff --git a/compiler/rustc_codegen_ssa/src/back/write.rs b/compiler/rustc_codegen_ssa/src/back/write.rs
index 92582dcc399..cbaf67d7345 100644
--- a/compiler/rustc_codegen_ssa/src/back/write.rs
+++ b/compiler/rustc_codegen_ssa/src/back/write.rs
@@ -138,12 +138,23 @@ impl ModuleConfig {
 
         let emit_obj = if !should_emit_obj {
             EmitObj::None
-        } else if sess.target.obj_is_bitcode || sess.opts.cg.linker_plugin_lto.enabled() {
+        } else if sess.target.obj_is_bitcode
+            || (sess.opts.cg.linker_plugin_lto.enabled() && !no_builtins)
+        {
             // This case is selected if the target uses objects as bitcode, or
             // if linker plugin LTO is enabled. In the linker plugin LTO case
             // the assumption is that the final link-step will read the bitcode
             // and convert it to object code. This may be done by either the
             // native linker or rustc itself.
+            //
+            // Note, however, that the linker-plugin-lto requested here is
+            // explicitly ignored for `#![no_builtins]` crates. These crates are
+            // specifically ignored by rustc's LTO passes and wouldn't work if
+            // loaded into the linker. These crates define symbols that LLVM
+            // lowers intrinsics to, and these symbol dependencies aren't known
+            // until after codegen. As a result any crate marked
+            // `#![no_builtins]` is assumed to not participate in LTO and
+            // instead goes on to generate object code.
             EmitObj::Bitcode
         } else if need_bitcode_in_object(tcx) {
             EmitObj::ObjectCode(BitcodeSection::Full)
@@ -322,8 +333,8 @@ pub struct CodegenContext<B: WriteBackendMethods> {
     pub crate_types: Vec<CrateType>,
     pub output_filenames: Arc<OutputFilenames>,
     pub invocation_temp: Option<String>,
-    pub regular_module_config: Arc<ModuleConfig>,
-    pub allocator_module_config: Arc<ModuleConfig>,
+    pub module_config: Arc<ModuleConfig>,
+    pub allocator_config: Arc<ModuleConfig>,
     pub tm_factory: TargetMachineFactoryFn<B>,
     pub msvc_imps_needed: bool,
     pub is_pe_coff: bool,
@@ -361,13 +372,6 @@ impl<B: WriteBackendMethods> CodegenContext<B> {
     pub fn create_dcx(&self) -> DiagCtxt {
         DiagCtxt::new(Box::new(self.diag_emitter.clone()))
     }
-
-    pub fn config(&self, kind: ModuleKind) -> &ModuleConfig {
-        match kind {
-            ModuleKind::Regular => &self.regular_module_config,
-            ModuleKind::Allocator => &self.allocator_module_config,
-        }
-    }
 }
 
 fn generate_thin_lto_work<B: ExtraBackendMethods>(
@@ -431,6 +435,7 @@ pub(crate) fn start_async_codegen<B: ExtraBackendMethods>(
     backend: B,
     tcx: TyCtxt<'_>,
     target_cpu: String,
+    allocator_module: Option<ModuleCodegen<B::Module>>,
 ) -> OngoingCodegen<B> {
     let (coordinator_send, coordinator_receive) = channel();
 
@@ -454,6 +459,7 @@ pub(crate) fn start_async_codegen<B: ExtraBackendMethods>(
         coordinator_receive,
         Arc::new(regular_config),
         Arc::new(allocator_config),
+        allocator_module,
         coordinator_send.clone(),
     );
 
@@ -709,15 +715,6 @@ pub(crate) enum WorkItem<B: WriteBackendMethods> {
 }
 
 impl<B: WriteBackendMethods> WorkItem<B> {
-    fn module_kind(&self) -> ModuleKind {
-        match *self {
-            WorkItem::Optimize(ref m) => m.kind,
-            WorkItem::CopyPostLtoArtifacts(_) | WorkItem::FatLto { .. } | WorkItem::ThinLto(_) => {
-                ModuleKind::Regular
-            }
-        }
-    }
-
     /// Generate a short description of this work item suitable for use as a thread name.
     fn short_description(&self) -> String {
         // `pthread_setname()` on *nix ignores anything beyond the first 15
@@ -806,7 +803,7 @@ pub(crate) fn compute_per_cgu_lto_type(
     let linker_does_lto = opts.cg.linker_plugin_lto.enabled();
 
     // When we're automatically doing ThinLTO for multi-codegen-unit
-    // builds we don't actually want to LTO the allocator modules if
+    // builds we don't actually want to LTO the allocator module if
     // it shows up. This is due to various linker shenanigans that
     // we'll encounter later.
     let is_allocator = module_kind == ModuleKind::Allocator;
@@ -832,11 +829,17 @@ pub(crate) fn compute_per_cgu_lto_type(
 fn execute_optimize_work_item<B: ExtraBackendMethods>(
     cgcx: &CodegenContext<B>,
     mut module: ModuleCodegen<B::Module>,
-    module_config: &ModuleConfig,
 ) -> WorkItemResult<B> {
+    let _timer = cgcx.prof.generic_activity_with_arg("codegen_module_optimize", &*module.name);
+
     let dcx = cgcx.create_dcx();
     let dcx = dcx.handle();
 
+    let module_config = match module.kind {
+        ModuleKind::Regular => &cgcx.module_config,
+        ModuleKind::Allocator => &cgcx.allocator_config,
+    };
+
     B::optimize(cgcx, dcx, &mut module, module_config);
 
     // After we've done the initial round of optimizations we need to
@@ -848,7 +851,7 @@ fn execute_optimize_work_item<B: ExtraBackendMethods>(
 
     // If we're doing some form of incremental LTO then we need to be sure to
     // save our module to disk first.
-    let bitcode = if cgcx.config(module.kind).emit_pre_lto_bc {
+    let bitcode = if module_config.emit_pre_lto_bc {
         let filename = pre_lto_bitcode_filename(&module.name);
         cgcx.incr_comp_session_dir.as_ref().map(|path| path.join(&filename))
     } else {
@@ -861,7 +864,7 @@ fn execute_optimize_work_item<B: ExtraBackendMethods>(
             WorkItemResult::Finished(module)
         }
         ComputedLtoType::Thin => {
-            let (name, thin_buffer) = B::prepare_thin(module, false);
+            let (name, thin_buffer) = B::prepare_thin(module);
             if let Some(path) = bitcode {
                 fs::write(&path, thin_buffer.data()).unwrap_or_else(|e| {
                     panic!("Error writing pre-lto-bitcode file `{}`: {}", path.display(), e);
@@ -888,8 +891,11 @@ fn execute_optimize_work_item<B: ExtraBackendMethods>(
 fn execute_copy_from_cache_work_item<B: ExtraBackendMethods>(
     cgcx: &CodegenContext<B>,
     module: CachedModuleCodegen,
-    module_config: &ModuleConfig,
 ) -> WorkItemResult<B> {
+    let _timer = cgcx
+        .prof
+        .generic_activity_with_arg("codegen_copy_artifacts_from_incr_cache", &*module.name);
+
     let incr_comp_session_dir = cgcx.incr_comp_session_dir.as_ref().unwrap();
 
     let mut links_from_incr_cache = Vec::new();
@@ -948,6 +954,7 @@ fn execute_copy_from_cache_work_item<B: ExtraBackendMethods>(
         }
     };
 
+    let module_config = &cgcx.module_config;
     let should_emit_obj = module_config.emit_obj != EmitObj::None;
     let assembly = load_from_incr_cache(module_config.emit_asm, OutputType::Assembly);
     let llvm_ir = load_from_incr_cache(module_config.emit_ir, OutputType::LlvmAssembly);
@@ -959,8 +966,8 @@ fn execute_copy_from_cache_work_item<B: ExtraBackendMethods>(
 
     WorkItemResult::Finished(CompiledModule {
         links_from_incr_cache,
-        name: module.name,
         kind: ModuleKind::Regular,
+        name: module.name,
         object,
         dwarf_object,
         bytecode,
@@ -975,8 +982,9 @@ fn execute_fat_lto_work_item<B: ExtraBackendMethods>(
     each_linked_rlib_for_lto: &[PathBuf],
     mut needs_fat_lto: Vec<FatLtoInput<B>>,
     import_only_modules: Vec<(SerializedModule<B::ModuleBuffer>, WorkProduct)>,
-    module_config: &ModuleConfig,
 ) -> WorkItemResult<B> {
+    let _timer = cgcx.prof.generic_activity_with_arg("codegen_module_perform_lto", "everything");
+
     for (module, wp) in import_only_modules {
         needs_fat_lto.push(FatLtoInput::Serialized { name: wp.cgu_name, buffer: module })
     }
@@ -987,17 +995,18 @@ fn execute_fat_lto_work_item<B: ExtraBackendMethods>(
         each_linked_rlib_for_lto,
         needs_fat_lto,
     );
-    let module = B::codegen(cgcx, module, module_config);
+    let module = B::codegen(cgcx, module, &cgcx.module_config);
     WorkItemResult::Finished(module)
 }
 
 fn execute_thin_lto_work_item<B: ExtraBackendMethods>(
     cgcx: &CodegenContext<B>,
     module: lto::ThinModule<B>,
-    module_config: &ModuleConfig,
 ) -> WorkItemResult<B> {
+    let _timer = cgcx.prof.generic_activity_with_arg("codegen_module_perform_lto", module.name());
+
     let module = B::optimize_thin(cgcx, module);
-    let module = B::codegen(cgcx, module, module_config);
+    let module = B::codegen(cgcx, module, &cgcx.module_config);
     WorkItemResult::Finished(module)
 }
 
@@ -1082,6 +1091,7 @@ fn start_executing_work<B: ExtraBackendMethods>(
     coordinator_receive: Receiver<Message<B>>,
     regular_config: Arc<ModuleConfig>,
     allocator_config: Arc<ModuleConfig>,
+    allocator_module: Option<ModuleCodegen<B::Module>>,
     tx_to_llvm_workers: Sender<Message<B>>,
 ) -> thread::JoinHandle<Result<CompiledModules, ()>> {
     let coordinator_send = tx_to_llvm_workers;
@@ -1146,8 +1156,8 @@ fn start_executing_work<B: ExtraBackendMethods>(
         expanded_args: tcx.sess.expanded_args.clone(),
         diag_emitter: shared_emitter.clone(),
         output_filenames: Arc::clone(tcx.output_filenames(())),
-        regular_module_config: regular_config,
-        allocator_module_config: allocator_config,
+        module_config: regular_config,
+        allocator_config,
         tm_factory: backend.target_machine_factory(tcx.sess, ol, backend_features),
         msvc_imps_needed: msvc_imps_needed(tcx),
         is_pe_coff: tcx.sess.target.is_like_windows,
@@ -1301,7 +1311,6 @@ fn start_executing_work<B: ExtraBackendMethods>(
         // This is where we collect codegen units that have gone all the way
         // through codegen and LLVM.
         let mut compiled_modules = vec![];
-        let mut compiled_allocator_module = None;
         let mut needs_fat_lto = Vec::new();
         let mut needs_thin_lto = Vec::new();
         let mut lto_import_only_modules = Vec::new();
@@ -1342,6 +1351,17 @@ fn start_executing_work<B: ExtraBackendMethods>(
 
         let mut llvm_start_time: Option<VerboseTimingGuard<'_>> = None;
 
+        let compiled_allocator_module = allocator_module.and_then(|allocator_module| {
+            match execute_optimize_work_item(&cgcx, allocator_module) {
+                WorkItemResult::Finished(compiled_module) => return Some(compiled_module),
+                WorkItemResult::NeedsFatLto(fat_lto_input) => needs_fat_lto.push(fat_lto_input),
+                WorkItemResult::NeedsThinLto(name, thin_buffer) => {
+                    needs_thin_lto.push((name, thin_buffer))
+                }
+            }
+            None
+        });
+
         // Run the message loop while there's still anything that needs message
         // processing. Note that as soon as codegen is aborted we simply want to
         // wait for all existing work to finish, so many of the conditions here
@@ -1575,15 +1595,7 @@ fn start_executing_work<B: ExtraBackendMethods>(
 
                     match result {
                         Ok(WorkItemResult::Finished(compiled_module)) => {
-                            match compiled_module.kind {
-                                ModuleKind::Regular => {
-                                    compiled_modules.push(compiled_module);
-                                }
-                                ModuleKind::Allocator => {
-                                    assert!(compiled_allocator_module.is_none());
-                                    compiled_allocator_module = Some(compiled_module);
-                                }
-                            }
+                            compiled_modules.push(compiled_module);
                         }
                         Ok(WorkItemResult::NeedsFatLto(fat_lto_input)) => {
                             assert!(!started_lto);
@@ -1711,46 +1723,22 @@ fn spawn_work<'a, B: ExtraBackendMethods>(
     let cgcx = cgcx.clone();
 
     B::spawn_named_thread(cgcx.time_trace, work.short_description(), move || {
-        let result = std::panic::catch_unwind(AssertUnwindSafe(|| {
-            let module_config = cgcx.config(work.module_kind());
-
-            match work {
-                WorkItem::Optimize(m) => {
-                    let _timer =
-                        cgcx.prof.generic_activity_with_arg("codegen_module_optimize", &*m.name);
-                    execute_optimize_work_item(&cgcx, m, module_config)
-                }
-                WorkItem::CopyPostLtoArtifacts(m) => {
-                    let _timer = cgcx.prof.generic_activity_with_arg(
-                        "codegen_copy_artifacts_from_incr_cache",
-                        &*m.name,
-                    );
-                    execute_copy_from_cache_work_item(&cgcx, m, module_config)
-                }
-                WorkItem::FatLto {
-                    exported_symbols_for_lto,
-                    each_linked_rlib_for_lto,
-                    needs_fat_lto,
-                    import_only_modules,
-                } => {
-                    let _timer = cgcx
-                        .prof
-                        .generic_activity_with_arg("codegen_module_perform_lto", "everything");
-                    execute_fat_lto_work_item(
-                        &cgcx,
-                        &exported_symbols_for_lto,
-                        &each_linked_rlib_for_lto,
-                        needs_fat_lto,
-                        import_only_modules,
-                        module_config,
-                    )
-                }
-                WorkItem::ThinLto(m) => {
-                    let _timer =
-                        cgcx.prof.generic_activity_with_arg("codegen_module_perform_lto", m.name());
-                    execute_thin_lto_work_item(&cgcx, m, module_config)
-                }
-            }
+        let result = std::panic::catch_unwind(AssertUnwindSafe(|| match work {
+            WorkItem::Optimize(m) => execute_optimize_work_item(&cgcx, m),
+            WorkItem::CopyPostLtoArtifacts(m) => execute_copy_from_cache_work_item(&cgcx, m),
+            WorkItem::FatLto {
+                exported_symbols_for_lto,
+                each_linked_rlib_for_lto,
+                needs_fat_lto,
+                import_only_modules,
+            } => execute_fat_lto_work_item(
+                &cgcx,
+                &exported_symbols_for_lto,
+                &each_linked_rlib_for_lto,
+                needs_fat_lto,
+                import_only_modules,
+            ),
+            WorkItem::ThinLto(m) => execute_thin_lto_work_item(&cgcx, m),
         }));
 
         let msg = match result {
diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs
index 8abaf201aba..45b028aa8ef 100644
--- a/compiler/rustc_codegen_ssa/src/base.rs
+++ b/compiler/rustc_codegen_ssa/src/base.rs
@@ -17,6 +17,7 @@ use rustc_hir::lang_items::LangItem;
 use rustc_hir::{ItemId, Target};
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrs;
 use rustc_middle::middle::debugger_visualizer::{DebuggerVisualizerFile, DebuggerVisualizerType};
+use rustc_middle::middle::dependency_format::Dependencies;
 use rustc_middle::middle::exported_symbols::{self, SymbolExportKind};
 use rustc_middle::middle::lang_items;
 use rustc_middle::mir::BinOp;
@@ -630,14 +631,30 @@ pub fn allocator_kind_for_codegen(tcx: TyCtxt<'_>) -> Option<AllocatorKind> {
     // If the crate doesn't have an `allocator_kind` set then there's definitely
     // no shim to generate. Otherwise we also check our dependency graph for all
     // our output crate types. If anything there looks like its a `Dynamic`
-    // linkage, then it's already got an allocator shim and we'll be using that
-    // one instead. If nothing exists then it's our job to generate the
-    // allocator!
-    let any_dynamic_crate = tcx.dependency_formats(()).iter().any(|(_, list)| {
+    // linkage for all crate types we may link as, then it's already got an
+    // allocator shim and we'll be using that one instead. If nothing exists
+    // then it's our job to generate the allocator! If crate types disagree
+    // about whether an allocator shim is necessary or not, we generate one
+    // and let needs_allocator_shim_for_linking decide at link time whether or
+    // not to use it for any particular linker invocation.
+    let all_crate_types_any_dynamic_crate = tcx.dependency_formats(()).iter().all(|(_, list)| {
         use rustc_middle::middle::dependency_format::Linkage;
         list.iter().any(|&linkage| linkage == Linkage::Dynamic)
     });
-    if any_dynamic_crate { None } else { tcx.allocator_kind(()) }
+    if all_crate_types_any_dynamic_crate { None } else { tcx.allocator_kind(()) }
+}
+
+/// Decide if this particular crate type needs an allocator shim linked in.
+/// This may return true even when allocator_kind_for_codegen returns false. In
+/// this case no allocator shim shall be linked.
+pub(crate) fn needs_allocator_shim_for_linking(
+    dependency_formats: &Dependencies,
+    crate_type: CrateType,
+) -> bool {
+    use rustc_middle::middle::dependency_format::Linkage;
+    let any_dynamic_crate =
+        dependency_formats[&crate_type].iter().any(|&linkage| linkage == Linkage::Dynamic);
+    !any_dynamic_crate
 }
 
 pub fn codegen_crate<B: ExtraBackendMethods>(
@@ -647,7 +664,7 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
 ) -> OngoingCodegen<B> {
     // Skip crate items and just output metadata in -Z no-codegen mode.
     if tcx.sess.opts.unstable_opts.no_codegen || !tcx.sess.opts.output_types.should_codegen() {
-        let ongoing_codegen = start_async_codegen(backend, tcx, target_cpu);
+        let ongoing_codegen = start_async_codegen(backend, tcx, target_cpu, None);
 
         ongoing_codegen.codegen_finished(tcx);
 
@@ -678,7 +695,27 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
         }
     }
 
-    let ongoing_codegen = start_async_codegen(backend.clone(), tcx, target_cpu);
+    // Codegen an allocator shim, if necessary.
+    let allocator_module = if let Some(kind) = allocator_kind_for_codegen(tcx) {
+        let llmod_id =
+            cgu_name_builder.build_cgu_name(LOCAL_CRATE, &["crate"], Some("allocator")).to_string();
+
+        tcx.sess.time("write_allocator_module", || {
+            let module = backend.codegen_allocator(
+                tcx,
+                &llmod_id,
+                kind,
+                // If allocator_kind is Some then alloc_error_handler_kind must
+                // also be Some.
+                tcx.alloc_error_handler_kind(()).unwrap(),
+            );
+            Some(ModuleCodegen::new_allocator(llmod_id, module))
+        })
+    } else {
+        None
+    };
+
+    let ongoing_codegen = start_async_codegen(backend.clone(), tcx, target_cpu, allocator_module);
 
     // For better throughput during parallel processing by LLVM, we used to sort
     // CGUs largest to smallest. This would lead to better thread utilization
@@ -795,35 +832,6 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
         }
     }
 
-    // Codegen an allocator shim, if necessary.
-    // Do this last to ensure the LLVM_passes timer doesn't start while no CGUs have been codegened
-    // yet for the backend to optimize.
-    if let Some(kind) = allocator_kind_for_codegen(tcx) {
-        let llmod_id =
-            cgu_name_builder.build_cgu_name(LOCAL_CRATE, &["crate"], Some("allocator")).to_string();
-        let module_llvm = tcx.sess.time("write_allocator_module", || {
-            backend.codegen_allocator(
-                tcx,
-                &llmod_id,
-                kind,
-                // If allocator_kind is Some then alloc_error_handler_kind must
-                // also be Some.
-                tcx.alloc_error_handler_kind(()).unwrap(),
-            )
-        });
-
-        ongoing_codegen.wait_for_signal_to_codegen_item();
-        ongoing_codegen.check_for_errors(tcx.sess);
-
-        // These modules are generally cheap and won't throw off scheduling.
-        let cost = 0;
-        submit_codegened_module_to_llvm(
-            &ongoing_codegen.coordinator,
-            ModuleCodegen::new_allocator(llmod_id, module_llvm),
-            cost,
-        );
-    }
-
     ongoing_codegen.codegen_finished(tcx);
 
     // Since the main thread is sometimes blocked during codegen, we keep track
diff --git a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
index 961bb788149..008340e614d 100644
--- a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
+++ b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
@@ -428,9 +428,16 @@ fn check_result(
     // llvm/llvm-project#70563).
     if !codegen_fn_attrs.target_features.is_empty()
         && matches!(codegen_fn_attrs.inline, InlineAttr::Always)
+        && !tcx.features().target_feature_inline_always()
         && let Some(span) = interesting_spans.inline
     {
-        tcx.dcx().span_err(span, "cannot use `#[inline(always)]` with `#[target_feature]`");
+        feature_err(
+            tcx.sess,
+            sym::target_feature_inline_always,
+            span,
+            "cannot use `#[inline(always)]` with `#[target_feature]`",
+        )
+        .emit();
     }
 
     // warn that inline has no effect when no_sanitize is present
diff --git a/compiler/rustc_codegen_ssa/src/lib.rs b/compiler/rustc_codegen_ssa/src/lib.rs
index fe0500a5d4c..baba8f9ca3e 100644
--- a/compiler/rustc_codegen_ssa/src/lib.rs
+++ b/compiler/rustc_codegen_ssa/src/lib.rs
@@ -119,7 +119,7 @@ impl<M> ModuleCodegen<M> {
         });
 
         CompiledModule {
-            name: self.name.clone(),
+            name: self.name,
             kind: self.kind,
             object,
             dwarf_object,
diff --git a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
index 8a67b8d6e5f..f6f2e3f2a3a 100644
--- a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
@@ -1,3 +1,4 @@
+use itertools::Itertools as _;
 use rustc_abi::{self as abi, FIRST_VARIANT};
 use rustc_middle::ty::adjustment::PointerCoercion;
 use rustc_middle::ty::layout::{HasTyCtxt, HasTypingEnv, LayoutOf, TyAndLayout};
@@ -111,14 +112,13 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     let size = bx.const_usize(dest.layout.size.bytes());
 
                     // Use llvm.memset.p0i8.* to initialize all same byte arrays
-                    if let Some(int) = bx.cx().const_to_opt_u128(v, false) {
-                        let bytes = &int.to_le_bytes()[..cg_elem.layout.size.bytes_usize()];
-                        let first = bytes[0];
-                        if bytes[1..].iter().all(|&b| b == first) {
-                            let fill = bx.cx().const_u8(first);
-                            bx.memset(start, fill, size, dest.val.align, MemFlags::empty());
-                            return true;
-                        }
+                    if let Some(int) = bx.cx().const_to_opt_u128(v, false)
+                        && let bytes = &int.to_le_bytes()[..cg_elem.layout.size.bytes_usize()]
+                        && let Ok(&byte) = bytes.iter().all_equal_value()
+                    {
+                        let fill = bx.cx().const_u8(byte);
+                        bx.memset(start, fill, size, dest.val.align, MemFlags::empty());
+                        return true;
                     }
 
                     // Use llvm.memset.p0i8.* to initialize byte arrays
@@ -130,13 +130,10 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     false
                 };
 
-                match cg_elem.val {
-                    OperandValue::Immediate(v) => {
-                        if try_init_all_same(bx, v) {
-                            return;
-                        }
-                    }
-                    _ => (),
+                if let OperandValue::Immediate(v) = cg_elem.val
+                    && try_init_all_same(bx, v)
+                {
+                    return;
                 }
 
                 let count = self
diff --git a/compiler/rustc_codegen_ssa/src/traits/write.rs b/compiler/rustc_codegen_ssa/src/traits/write.rs
index cc7c4e46d7b..1ac1d7ef2e2 100644
--- a/compiler/rustc_codegen_ssa/src/traits/write.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/write.rs
@@ -50,16 +50,12 @@ pub trait WriteBackendMethods: Clone + 'static {
         module: ModuleCodegen<Self::Module>,
         config: &ModuleConfig,
     ) -> CompiledModule;
-    fn prepare_thin(
-        module: ModuleCodegen<Self::Module>,
-        want_summary: bool,
-    ) -> (String, Self::ThinBuffer);
+    fn prepare_thin(module: ModuleCodegen<Self::Module>) -> (String, Self::ThinBuffer);
     fn serialize_module(module: ModuleCodegen<Self::Module>) -> (String, Self::ModuleBuffer);
 }
 
 pub trait ThinBufferMethods: Send + Sync {
     fn data(&self) -> &[u8];
-    fn thin_link_data(&self) -> &[u8];
 }
 
 pub trait ModuleBufferMethods: Send + Sync {
diff --git a/compiler/rustc_const_eval/Cargo.toml b/compiler/rustc_const_eval/Cargo.toml
index acf19b0f2fc..51dcee8d882 100644
--- a/compiler/rustc_const_eval/Cargo.toml
+++ b/compiler/rustc_const_eval/Cargo.toml
@@ -5,9 +5,9 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-either.workspace = true
+either = "1"
 rustc_abi = { path = "../rustc_abi" }
-rustc_apfloat.workspace = true
+rustc_apfloat = "0.2.0"
 rustc_ast = { path = "../rustc_ast" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
@@ -22,5 +22,5 @@ rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
 rustc_trait_selection = { path = "../rustc_trait_selection" }
-tracing.workspace = true
+tracing = "0.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_const_eval/messages.ftl b/compiler/rustc_const_eval/messages.ftl
index 60518dafbf2..700d7c26752 100644
--- a/compiler/rustc_const_eval/messages.ftl
+++ b/compiler/rustc_const_eval/messages.ftl
@@ -457,7 +457,7 @@ const_eval_validation_failure =
     it is undefined behavior to use this value
 
 const_eval_validation_failure_note =
-    The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
+    the rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
 const_eval_validation_front_matter_invalid_value = constructing invalid value
 const_eval_validation_front_matter_invalid_value_with_path = constructing invalid value at {$path}
diff --git a/compiler/rustc_data_structures/Cargo.toml b/compiler/rustc_data_structures/Cargo.toml
index 852fc11350b..c8296e05f6b 100644
--- a/compiler/rustc_data_structures/Cargo.toml
+++ b/compiler/rustc_data_structures/Cargo.toml
@@ -6,15 +6,15 @@ edition = "2024"
 [dependencies]
 # tidy-alphabetical-start
 arrayvec = { version = "0.7", default-features = false }
-bitflags.workspace = true
-either.workspace = true
+bitflags = "2.4.1"
+either = "1.0"
 elsa = "1.11.0"
 ena = "0.14.3"
-indexmap.workspace = true
+indexmap = "2.4.0"
 jobserver_crate = { version = "0.1.28", package = "jobserver" }
-measureme.workspace = true
+measureme = "12.0.1"
 parking_lot = "0.12"
-rustc-hash.workspace = true
+rustc-hash = "2.0.0"
 rustc-stable-hash = { version = "0.1.0", features = ["nightly"] }
 rustc_arena = { path = "../rustc_arena" }
 rustc_graphviz = { path = "../rustc_graphviz" }
@@ -25,9 +25,9 @@ rustc_serialize = { path = "../rustc_serialize" }
 rustc_thread_pool = { path = "../rustc_thread_pool" }
 smallvec = { version = "1.8.1", features = ["const_generics", "union", "may_dangle"] }
 stacker = "0.1.17"
-tempfile.workspace = true
-thin-vec.workspace = true
-tracing.workspace = true
+tempfile = "3.2"
+thin-vec = "0.2.12"
+tracing = "0.1"
 # tidy-alphabetical-end
 
 [dependencies.hashbrown]
@@ -47,7 +47,7 @@ features = [
 
 [target.'cfg(unix)'.dependencies]
 # tidy-alphabetical-start
-libc.workspace = true
+libc = "0.2"
 # tidy-alphabetical-end
 
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
diff --git a/compiler/rustc_driver_impl/Cargo.toml b/compiler/rustc_driver_impl/Cargo.toml
index 196c8aa3547..ae1dbd2cf51 100644
--- a/compiler/rustc_driver_impl/Cargo.toml
+++ b/compiler/rustc_driver_impl/Cargo.toml
@@ -49,14 +49,14 @@ rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
 rustc_trait_selection = { path = "../rustc_trait_selection" }
 rustc_ty_utils = { path = "../rustc_ty_utils" }
-serde_json.workspace = true
+serde_json = "1.0.59"
 shlex = "1.0"
-tracing.workspace = true
+tracing = { version = "0.1.35" }
 # tidy-alphabetical-end
 
 [target.'cfg(all(unix, any(target_env = "gnu", target_os = "macos")))'.dependencies]
 # tidy-alphabetical-start
-libc.workspace = true
+libc = "0.2"
 # tidy-alphabetical-end
 
 [target.'cfg(windows)'.dependencies.windows]
diff --git a/compiler/rustc_driver_impl/messages.ftl b/compiler/rustc_driver_impl/messages.ftl
index 2c6a0291ac2..b62cdc35f51 100644
--- a/compiler/rustc_driver_impl/messages.ftl
+++ b/compiler/rustc_driver_impl/messages.ftl
@@ -14,7 +14,7 @@ driver_impl_ice_version = rustc {$version} running on {$triple}
 
 driver_impl_rlink_corrupt_file = corrupt metadata encountered in `{$file}`
 
-driver_impl_rlink_empty_version_number = The input does not contain version number
+driver_impl_rlink_empty_version_number = the input does not contain version number
 
 driver_impl_rlink_encoding_version_mismatch = .rlink file was produced with encoding version `{$version_array}`, but the current version is `{$rlink_version}`
 
@@ -24,6 +24,6 @@ driver_impl_rlink_rustc_version_mismatch = .rlink file was produced by rustc ver
 
 driver_impl_rlink_unable_to_read = failed to read rlink file: `{$err}`
 
-driver_impl_rlink_wrong_file_type = The input does not look like a .rlink file
+driver_impl_rlink_wrong_file_type = the input does not look like a .rlink file
 
 driver_impl_unstable_feature_usage = cannot dump feature usage metrics: {$error}
diff --git a/compiler/rustc_error_messages/Cargo.toml b/compiler/rustc_error_messages/Cargo.toml
index 7d2dc20e136..db22e065907 100644
--- a/compiler/rustc_error_messages/Cargo.toml
+++ b/compiler/rustc_error_messages/Cargo.toml
@@ -17,6 +17,6 @@ rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_span = { path = "../rustc_span" }
-tracing.workspace = true
+tracing = "0.1"
 unic-langid = { version = "0.9.0", features = ["macros"] }
 # tidy-alphabetical-end
diff --git a/compiler/rustc_errors/Cargo.toml b/compiler/rustc_errors/Cargo.toml
index 67a17ce88fa..7912b8e6098 100644
--- a/compiler/rustc_errors/Cargo.toml
+++ b/compiler/rustc_errors/Cargo.toml
@@ -21,10 +21,10 @@ rustc_macros = { path = "../rustc_macros" }
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_span = { path = "../rustc_span" }
 serde = { version = "1.0.125", features = ["derive"] }
-serde_json.workspace = true
+serde_json = "1.0.59"
 termcolor = "1.2.0"
 termize = "0.2"
-tracing.workspace = true
+tracing = "0.1"
 # tidy-alphabetical-end
 
 [target.'cfg(windows)'.dependencies.windows]
diff --git a/compiler/rustc_errors/src/diagnostic.rs b/compiler/rustc_errors/src/diagnostic.rs
index 96a4ed3218f..ae23ef1e255 100644
--- a/compiler/rustc_errors/src/diagnostic.rs
+++ b/compiler/rustc_errors/src/diagnostic.rs
@@ -945,11 +945,6 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
             None,
             "Span must not be empty and have no suggestion",
         );
-        debug_assert_eq!(
-            parts.array_windows().find(|[a, b]| a.span.overlaps(b.span)),
-            None,
-            "suggestion must not have overlapping parts",
-        );
 
         self.push_suggestion(CodeSuggestion {
             substitutions: vec![Substitution { parts }],
diff --git a/compiler/rustc_errors/src/emitter.rs b/compiler/rustc_errors/src/emitter.rs
index b94370e8e9b..93b1e6b7615 100644
--- a/compiler/rustc_errors/src/emitter.rs
+++ b/compiler/rustc_errors/src/emitter.rs
@@ -2354,7 +2354,6 @@ impl HumanEmitter {
                         .sum();
                     let underline_start = (span_start_pos + start) as isize + offset;
                     let underline_end = (span_start_pos + start + sub_len) as isize + offset;
-                    assert!(underline_start >= 0 && underline_end >= 0);
                     let padding: usize = max_line_num_len + 3;
                     for p in underline_start..underline_end {
                         if let DisplaySuggestion::Underline = show_code_change
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index 71fc54f0d33..8869799ce90 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -381,6 +381,17 @@ impl CodeSuggestion {
                 // Assumption: all spans are in the same file, and all spans
                 // are disjoint. Sort in ascending order.
                 substitution.parts.sort_by_key(|part| part.span.lo());
+                // Verify the assumption that all spans are disjoint
+                assert_eq!(
+                    substitution.parts.array_windows().find(|[a, b]| a.span.overlaps(b.span)),
+                    None,
+                    "all spans must be disjoint",
+                );
+
+                // Account for cases where we are suggesting the same code that's already
+                // there. This shouldn't happen often, but in some cases for multipart
+                // suggestions it's much easier to handle it here than in the origin.
+                substitution.parts.retain(|p| is_different(sm, &p.snippet, p.span));
 
                 // Find the bounding span.
                 let lo = substitution.parts.iter().map(|part| part.span.lo()).min()?;
@@ -470,16 +481,12 @@ impl CodeSuggestion {
                             _ => 1,
                         })
                         .sum();
-                    if !is_different(sm, &part.snippet, part.span) {
-                        // Account for cases where we are suggesting the same code that's already
-                        // there. This shouldn't happen often, but in some cases for multipart
-                        // suggestions it's much easier to handle it here than in the origin.
-                    } else {
-                        line_highlight.push(SubstitutionHighlight {
-                            start: (cur_lo.col.0 as isize + acc) as usize,
-                            end: (cur_lo.col.0 as isize + acc + len) as usize,
-                        });
-                    }
+
+                    line_highlight.push(SubstitutionHighlight {
+                        start: (cur_lo.col.0 as isize + acc) as usize,
+                        end: (cur_lo.col.0 as isize + acc + len) as usize,
+                    });
+
                     buf.push_str(&part.snippet);
                     let cur_hi = sm.lookup_char_pos(part.span.hi());
                     // Account for the difference between the width of the current code and the
@@ -1160,7 +1167,7 @@ impl<'a> DiagCtxtHandle<'a> {
         // - It's only produce with JSON output.
         // - It's not emitted the usual way, via `emit_diagnostic`.
         // - The `$message_type` field is "unused_externs" rather than the usual
-        //   "diagnosic".
+        //   "diagnostic".
         //
         // We count it as a lint error because it has a lint level. The value
         // of `loud` (which comes from "unused-externs" or
diff --git a/compiler/rustc_expand/Cargo.toml b/compiler/rustc_expand/Cargo.toml
index 9bb7143af51..f897833d85c 100644
--- a/compiler/rustc_expand/Cargo.toml
+++ b/compiler/rustc_expand/Cargo.toml
@@ -29,6 +29,6 @@ rustc_serialize = { path = "../rustc_serialize" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
-thin-vec.workspace = true
-tracing.workspace = true
+thin-vec = "0.2.12"
+tracing = "0.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_expand/src/mbe/macro_parser.rs b/compiler/rustc_expand/src/mbe/macro_parser.rs
index 0324057e331..ab8e059b7b7 100644
--- a/compiler/rustc_expand/src/mbe/macro_parser.rs
+++ b/compiler/rustc_expand/src/mbe/macro_parser.rs
@@ -77,7 +77,7 @@ use std::rc::Rc;
 
 pub(crate) use NamedMatch::*;
 pub(crate) use ParseResult::*;
-use rustc_ast::token::{self, DocComment, NonterminalKind, Token};
+use rustc_ast::token::{self, DocComment, NonterminalKind, Token, TokenKind};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::ErrorGuaranteed;
 use rustc_lint_defs::pluralize;
@@ -397,7 +397,23 @@ fn token_name_eq(t1: &Token, t2: &Token) -> bool {
     {
         ident1.name == ident2.name && is_raw1 == is_raw2
     } else {
-        t1.kind == t2.kind
+        // Note: we SHOULD NOT use `t1.kind == t2.kind` here, and we should instead compare the
+        // tokens using the special comparison logic below.
+        // It makes sure that variants containing `InvisibleOrigin` will
+        // never compare equal to one another.
+        //
+        // When we had AST-based nonterminals we couldn't compare them, and the
+        // old `Nonterminal` type had an `eq` that always returned false,
+        // resulting in this restriction:
+        // <https://doc.rust-lang.org/nightly/reference/macros-by-example.html#forwarding-a-matched-fragment>
+        // This comparison logic emulates that behaviour. We could consider lifting this
+        // restriction now but there are still cases involving invisible
+        // delimiters that make it harder than it first appears.
+        match (t1.kind, t2.kind) {
+            (TokenKind::OpenInvisible(_) | TokenKind::CloseInvisible(_), _)
+            | (_, TokenKind::OpenInvisible(_) | TokenKind::CloseInvisible(_)) => false,
+            (a, b) => a == b,
+        }
     }
 }
 
diff --git a/compiler/rustc_expand/src/mbe/transcribe.rs b/compiler/rustc_expand/src/mbe/transcribe.rs
index 174844d6ad6..e4e4866b64c 100644
--- a/compiler/rustc_expand/src/mbe/transcribe.rs
+++ b/compiler/rustc_expand/src/mbe/transcribe.rs
@@ -556,7 +556,12 @@ fn metavar_expr_concat<'tx>(
                         };
                         match &named_matches[*curr_idx] {
                             // FIXME(c410-f3r) Nested repetitions are unimplemented
-                            MatchedSeq(_) => unimplemented!(),
+                            MatchedSeq(_) => {
+                                return Err(dcx.struct_span_err(
+                                    ident.span,
+                                    "nested repetitions with `${concat(...)}` metavariable expressions are not yet supported",
+                                ));
+                            }
                             MatchedSingle(pnr) => extract_symbol_from_pnr(dcx, pnr, ident.span)?,
                         }
                     }
diff --git a/compiler/rustc_feature/Cargo.toml b/compiler/rustc_feature/Cargo.toml
index b58f2375852..a4746ac455c 100644
--- a/compiler/rustc_feature/Cargo.toml
+++ b/compiler/rustc_feature/Cargo.toml
@@ -9,5 +9,5 @@ rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_hir = { path = "../rustc_hir" }
 rustc_span = { path = "../rustc_span" }
 serde = { version = "1.0.125", features = ["derive"] }
-serde_json.workspace = true
+serde_json = "1.0.59"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_feature/src/accepted.rs b/compiler/rustc_feature/src/accepted.rs
index 9fe55216f93..6af4cfb0e56 100644
--- a/compiler/rustc_feature/src/accepted.rs
+++ b/compiler/rustc_feature/src/accepted.rs
@@ -203,6 +203,9 @@ declare_features! (
     (accepted, expr_fragment_specifier_2024, "1.83.0", Some(123742)),
     /// Allows arbitrary expressions in key-value attributes at parse time.
     (accepted, extended_key_value_attributes, "1.54.0", Some(78835)),
+    /// Allows using `aapcs`, `efiapi`, `sysv64` and `win64` as calling conventions
+    /// for functions with varargs.
+    (accepted, extended_varargs_abi_support, "CURRENT_RUSTC_VERSION", Some(100189)),
     /// Allows resolving absolute paths as paths from other crates.
     (accepted, extern_absolute_paths, "1.30.0", Some(44660)),
     /// Allows `extern crate foo as bar;`. This puts `bar` into extern prelude.
diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs
index 92b435b4b01..4f35bf63a1a 100644
--- a/compiler/rustc_feature/src/unstable.rs
+++ b/compiler/rustc_feature/src/unstable.rs
@@ -492,9 +492,6 @@ declare_features! (
     (incomplete, explicit_tail_calls, "1.72.0", Some(112788)),
     /// Allows using `#[export_stable]` which indicates that an item is exportable.
     (incomplete, export_stable, "1.88.0", Some(139939)),
-    /// Allows using `aapcs`, `efiapi`, `sysv64` and `win64` as calling conventions
-    /// for functions with varargs.
-    (unstable, extended_varargs_abi_support, "1.65.0", Some(100189)),
     /// Allows using `system` as a calling convention with varargs.
     (unstable, extern_system_varargs, "1.86.0", Some(136946)),
     /// Allows defining `extern type`s.
@@ -645,6 +642,8 @@ declare_features! (
     (unstable, super_let, "1.88.0", Some(139076)),
     /// Allows subtrait items to shadow supertrait items.
     (unstable, supertrait_item_shadowing, "1.86.0", Some(89151)),
+    /// Allows the use of target_feature when a function is marked inline(always).
+    (unstable, target_feature_inline_always, "CURRENT_RUSTC_VERSION", Some(145574)),
     /// Allows using `#[thread_local]` on `static` items.
     (unstable, thread_local, "1.0.0", Some(29594)),
     /// Allows defining `trait X = A + B;` alias items.
diff --git a/compiler/rustc_fluent_macro/Cargo.toml b/compiler/rustc_fluent_macro/Cargo.toml
index 60afd9aca87..d7ef4280aef 100644
--- a/compiler/rustc_fluent_macro/Cargo.toml
+++ b/compiler/rustc_fluent_macro/Cargo.toml
@@ -11,8 +11,8 @@ proc-macro = true
 annotate-snippets = "0.11"
 fluent-bundle = "0.16"
 fluent-syntax = "0.12"
-proc-macro2.workspace = true
-quote.workspace = true
+proc-macro2 = "1"
+quote = "1"
 syn = { version = "2", features = ["full"] }
 unic-langid = { version = "0.9.0", features = ["macros"] }
 # tidy-alphabetical-end
diff --git a/compiler/rustc_fs_util/Cargo.toml b/compiler/rustc_fs_util/Cargo.toml
index 37970e81fea..90a6acade8b 100644
--- a/compiler/rustc_fs_util/Cargo.toml
+++ b/compiler/rustc_fs_util/Cargo.toml
@@ -5,5 +5,5 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-tempfile.workspace = true
+tempfile = "3.7.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_hir/Cargo.toml b/compiler/rustc_hir/Cargo.toml
index e74fcfe7455..1008a3e787d 100644
--- a/compiler/rustc_hir/Cargo.toml
+++ b/compiler/rustc_hir/Cargo.toml
@@ -5,8 +5,8 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-bitflags.workspace = true
-odht.workspace = true
+bitflags = "2.9.1"
+odht = { version = "0.3.1", features = ["nightly"] }
 rustc_abi = { path = "../rustc_abi" }
 rustc_arena = { path = "../rustc_arena" }
 rustc_ast = { path = "../rustc_ast" }
@@ -21,6 +21,6 @@ rustc_serialize = { path = "../rustc_serialize" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
-thin-vec.workspace = true
-tracing.workspace = true
+thin-vec = "0.2.12"
+tracing = "0.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs
index e397c286de2..ae03121e5f7 100644
--- a/compiler/rustc_hir/src/hir.rs
+++ b/compiler/rustc_hir/src/hir.rs
@@ -784,7 +784,6 @@ pub enum GenericParamKind<'hir> {
         ty: &'hir Ty<'hir>,
         /// Optional default value for the const generic param
         default: Option<&'hir ConstArg<'hir>>,
-        synthetic: bool,
     },
 }
 
@@ -1884,8 +1883,8 @@ pub enum PatKind<'hir> {
     Binding(BindingMode, HirId, Ident, Option<&'hir Pat<'hir>>),
 
     /// A struct or struct variant pattern (e.g., `Variant {x, y, ..}`).
-    /// The `bool` is `true` in the presence of a `..`.
-    Struct(QPath<'hir>, &'hir [PatField<'hir>], bool),
+    /// The `Option` contains the span of a possible `..`.
+    Struct(QPath<'hir>, &'hir [PatField<'hir>], Option<Span>),
 
     /// A tuple struct/variant pattern `Variant(x, y, .., z)`.
     /// If the `..` pattern fragment is present, then `DotDotPos` denotes its position.
@@ -4979,8 +4978,8 @@ mod size_asserts {
     static_assert_size!(ItemKind<'_>, 64);
     static_assert_size!(LetStmt<'_>, 72);
     static_assert_size!(Param<'_>, 32);
-    static_assert_size!(Pat<'_>, 72);
-    static_assert_size!(PatKind<'_>, 48);
+    static_assert_size!(Pat<'_>, 80);
+    static_assert_size!(PatKind<'_>, 56);
     static_assert_size!(Path<'_>, 40);
     static_assert_size!(PathSegment<'_>, 48);
     static_assert_size!(QPath<'_>, 24);
diff --git a/compiler/rustc_hir/src/intravisit.rs b/compiler/rustc_hir/src/intravisit.rs
index 9b2f8ae75fa..25a7ae239f3 100644
--- a/compiler/rustc_hir/src/intravisit.rs
+++ b/compiler/rustc_hir/src/intravisit.rs
@@ -1085,7 +1085,7 @@ pub fn walk_generic_param<'v, V: Visitor<'v>>(
         GenericParamKind::Type { ref default, .. } => {
             visit_opt!(visitor, visit_ty_unambig, default)
         }
-        GenericParamKind::Const { ref ty, ref default, synthetic: _ } => {
+        GenericParamKind::Const { ref ty, ref default } => {
             try_visit!(visitor.visit_ty_unambig(ty));
             if let Some(default) = default {
                 try_visit!(visitor.visit_const_param_default(*hir_id, default));
diff --git a/compiler/rustc_hir_analysis/Cargo.toml b/compiler/rustc_hir_analysis/Cargo.toml
index bb86beb2251..e5017794d8f 100644
--- a/compiler/rustc_hir_analysis/Cargo.toml
+++ b/compiler/rustc_hir_analysis/Cargo.toml
@@ -9,7 +9,7 @@ doctest = false
 
 [dependencies]
 # tidy-alphabetical-start
-itertools.workspace = true
+itertools = "0.12"
 rustc_abi = { path = "../rustc_abi" }
 rustc_arena = { path = "../rustc_arena" }
 rustc_ast = { path = "../rustc_ast" }
@@ -29,5 +29,5 @@ rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
 rustc_trait_selection = { path = "../rustc_trait_selection" }
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
-tracing.workspace = true
+tracing = "0.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index eccb88a938f..08b344638dd 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -978,7 +978,7 @@ pub(crate) fn check_item_type(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Result<(),
                         tcx.ensure_ok().fn_sig(def_id);
                         let item = tcx.hir_foreign_item(item);
                         let hir::ForeignItemKind::Fn(sig, ..) = item.kind else { bug!() };
-                        require_c_abi_if_c_variadic(tcx, sig.decl, abi, item.span);
+                        check_c_variadic_abi(tcx, sig.decl, abi, item.span);
                     }
                     DefKind::Static { .. } => {
                         tcx.ensure_ok().codegen_fn_attrs(def_id);
diff --git a/compiler/rustc_hir_analysis/src/check/intrinsic.rs b/compiler/rustc_hir_analysis/src/check/intrinsic.rs
index cfc6bc2f3a0..aa2d27ab809 100644
--- a/compiler/rustc_hir_analysis/src/check/intrinsic.rs
+++ b/compiler/rustc_hir_analysis/src/check/intrinsic.rs
@@ -449,6 +449,9 @@ pub(crate) fn check_intrinsic_type(
         }
         sym::unchecked_shl | sym::unchecked_shr => (2, 0, vec![param(0), param(1)], param(0)),
         sym::rotate_left | sym::rotate_right => (1, 0, vec![param(0), tcx.types.u32], param(0)),
+        sym::unchecked_funnel_shl | sym::unchecked_funnel_shr => {
+            (1, 0, vec![param(0), param(0), tcx.types.u32], param(0))
+        }
         sym::unchecked_add | sym::unchecked_sub | sym::unchecked_mul => {
             (1, 0, vec![param(0), param(0)], param(0))
         }
diff --git a/compiler/rustc_hir_analysis/src/check/mod.rs b/compiler/rustc_hir_analysis/src/check/mod.rs
index 2e4b151d4dc..b5c0ca4727c 100644
--- a/compiler/rustc_hir_analysis/src/check/mod.rs
+++ b/compiler/rustc_hir_analysis/src/check/mod.rs
@@ -98,7 +98,7 @@ use tracing::debug;
 
 use self::compare_impl_item::collect_return_position_impl_trait_in_trait_tys;
 use self::region::region_scope_tree;
-use crate::{errors, require_c_abi_if_c_variadic};
+use crate::{check_c_variadic_abi, errors};
 
 /// Adds query implementations to the [Providers] vtable, see [`rustc_middle::query`]
 pub(super) fn provide(providers: &mut Providers) {
diff --git a/compiler/rustc_hir_analysis/src/check/region.rs b/compiler/rustc_hir_analysis/src/check/region.rs
index f5770b7312d..2ba7ed46f92 100644
--- a/compiler/rustc_hir_analysis/src/check/region.rs
+++ b/compiler/rustc_hir_analysis/src/check/region.rs
@@ -490,12 +490,8 @@ fn resolve_local<'tcx>(
             //
             // Iterate up to the enclosing destruction scope to find the same scope that will also
             // be used for the result of the block itself.
-            while let Some(s) = visitor.cx.var_parent {
-                let parent = visitor.scope_tree.parent_map.get(&s).cloned();
-                if let Some(Scope { data: ScopeData::Destruction, .. }) = parent {
-                    break;
-                }
-                visitor.cx.var_parent = parent;
+            if let Some(inner_scope) = visitor.cx.var_parent {
+                (visitor.cx.var_parent, _) = visitor.scope_tree.default_temporary_scope(inner_scope)
             }
         }
     }
diff --git a/compiler/rustc_hir_analysis/src/collect/generics_of.rs b/compiler/rustc_hir_analysis/src/collect/generics_of.rs
index ce0e51f106f..333cea23c41 100644
--- a/compiler/rustc_hir_analysis/src/collect/generics_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/generics_of.rs
@@ -305,7 +305,7 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
 
                 ty::GenericParamDefKind::Type { has_default: default.is_some(), synthetic }
             }
-            GenericParamKind::Const { ty: _, default, synthetic } => {
+            GenericParamKind::Const { ty: _, default } => {
                 if default.is_some() {
                     match param_default_policy.expect("no policy for generic param default") {
                         ParamDefaultPolicy::Allowed => {}
@@ -316,7 +316,7 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
                     }
                 }
 
-                ty::GenericParamDefKind::Const { has_default: default.is_some(), synthetic }
+                ty::GenericParamDefKind::Const { has_default: default.is_some() }
             }
         };
         Some(ty::GenericParamDef {
@@ -523,7 +523,7 @@ impl<'v> Visitor<'v> for AnonConstInParamTyDetector {
     type Result = ControlFlow<()>;
 
     fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) -> Self::Result {
-        if let GenericParamKind::Const { ty, default: _, synthetic: _ } = p.kind {
+        if let GenericParamKind::Const { ty, default: _ } = p.kind {
             let prev = self.in_param_ty;
             self.in_param_ty = true;
             let res = self.visit_ty_unambig(ty);
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/generics.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/generics.rs
index fc519c194bb..f5a64ede398 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/generics.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/generics.rs
@@ -419,14 +419,7 @@ pub(crate) fn check_generic_arg_count(
         .filter(|param| matches!(param.kind, ty::GenericParamDefKind::Type { synthetic: true, .. }))
         .count();
     let named_type_param_count = param_counts.types - has_self as usize - synth_type_param_count;
-    let synth_const_param_count = gen_params
-        .own_params
-        .iter()
-        .filter(|param| {
-            matches!(param.kind, ty::GenericParamDefKind::Const { synthetic: true, .. })
-        })
-        .count();
-    let named_const_param_count = param_counts.consts - synth_const_param_count;
+    let named_const_param_count = param_counts.consts;
     let infer_lifetimes =
         (gen_pos != GenericArgPosition::Type || seg.infer_args) && !gen_args.has_lifetime_params();
 
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
index c7b984d9b25..c5e079fe89a 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
@@ -52,11 +52,11 @@ use rustc_trait_selection::traits::{self, FulfillmentError};
 use tracing::{debug, instrument};
 
 use crate::check::check_abi;
+use crate::check_c_variadic_abi;
 use crate::errors::{AmbiguousLifetimeBound, BadReturnTypeNotation};
 use crate::hir_ty_lowering::errors::{GenericsArgsErrExtend, prohibit_assoc_item_constraint};
 use crate::hir_ty_lowering::generics::{check_generic_arg_count, lower_generic_args};
 use crate::middle::resolve_bound_vars as rbv;
-use crate::require_c_abi_if_c_variadic;
 
 /// A path segment that is semantically allowed to have generic arguments.
 #[derive(Debug)]
@@ -2412,7 +2412,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 Ty::new_tup_from_iter(tcx, fields.iter().map(|t| self.lower_ty(t)))
             }
             hir::TyKind::FnPtr(bf) => {
-                require_c_abi_if_c_variadic(tcx, bf.decl, bf.abi, hir_ty.span);
+                check_c_variadic_abi(tcx, bf.decl, bf.abi, hir_ty.span);
 
                 Ty::new_fn_ptr(
                     tcx,
diff --git a/compiler/rustc_hir_analysis/src/lib.rs b/compiler/rustc_hir_analysis/src/lib.rs
index 44a5ceed469..2562ab7542a 100644
--- a/compiler/rustc_hir_analysis/src/lib.rs
+++ b/compiler/rustc_hir_analysis/src/lib.rs
@@ -90,7 +90,7 @@ mod outlives;
 mod variance;
 
 pub use errors::NoVariantNamed;
-use rustc_abi::ExternAbi;
+use rustc_abi::{CVariadicStatus, ExternAbi};
 use rustc_hir::def::DefKind;
 use rustc_hir::lints::DelayedLint;
 use rustc_hir::{self as hir};
@@ -99,7 +99,6 @@ use rustc_middle::mir::interpret::GlobalId;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::{self, Const, Ty, TyCtxt};
 use rustc_session::parse::feature_err;
-use rustc_span::symbol::sym;
 use rustc_span::{ErrorGuaranteed, Span};
 use rustc_trait_selection::traits;
 
@@ -108,46 +107,34 @@ use crate::hir_ty_lowering::{FeedConstTy, HirTyLowerer};
 
 rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
 
-fn require_c_abi_if_c_variadic(
-    tcx: TyCtxt<'_>,
-    decl: &hir::FnDecl<'_>,
-    abi: ExternAbi,
-    span: Span,
-) {
-    // ABIs which can stably use varargs
-    if !decl.c_variadic || matches!(abi, ExternAbi::C { .. } | ExternAbi::Cdecl { .. }) {
+fn check_c_variadic_abi(tcx: TyCtxt<'_>, decl: &hir::FnDecl<'_>, abi: ExternAbi, span: Span) {
+    if !decl.c_variadic {
+        // Not even a variadic function.
         return;
     }
 
-    // ABIs with feature-gated stability
-    let extended_abi_support = tcx.features().extended_varargs_abi_support();
-    let extern_system_varargs = tcx.features().extern_system_varargs();
-
-    // If the feature gate has been enabled, we can stop here
-    if extern_system_varargs && let ExternAbi::System { .. } = abi {
-        return;
-    };
-    if extended_abi_support && abi.supports_varargs() {
-        return;
-    };
-
-    // Looks like we need to pick an error to emit.
-    // Is there any feature which we could have enabled to make this work?
-    let unstable_explain =
-        format!("C-variadic functions with the {abi} calling convention are unstable");
-    match abi {
-        ExternAbi::System { .. } => {
-            feature_err(&tcx.sess, sym::extern_system_varargs, span, unstable_explain)
+    match abi.supports_c_variadic() {
+        CVariadicStatus::Stable => {}
+        CVariadicStatus::NotSupported => {
+            tcx.dcx()
+                .create_err(errors::VariadicFunctionCompatibleConvention {
+                    span,
+                    convention: &format!("{abi}"),
+                })
+                .emit();
         }
-        abi if abi.supports_varargs() => {
-            feature_err(&tcx.sess, sym::extended_varargs_abi_support, span, unstable_explain)
+        CVariadicStatus::Unstable { feature } => {
+            if !tcx.features().enabled(feature) {
+                feature_err(
+                    &tcx.sess,
+                    feature,
+                    span,
+                    format!("C-variadic functions with the {abi} calling convention are unstable"),
+                )
+                .emit();
+            }
         }
-        _ => tcx.dcx().create_err(errors::VariadicFunctionCompatibleConvention {
-            span,
-            convention: &format!("{abi}"),
-        }),
     }
-    .emit();
 }
 
 /// Adds query implementations to the [Providers] vtable, see [`rustc_middle::query`]
diff --git a/compiler/rustc_hir_pretty/src/lib.rs b/compiler/rustc_hir_pretty/src/lib.rs
index be5859b57c5..b9d8eed54a9 100644
--- a/compiler/rustc_hir_pretty/src/lib.rs
+++ b/compiler/rustc_hir_pretty/src/lib.rs
@@ -1958,12 +1958,12 @@ impl<'a> State<'a> {
                 self.print_qpath(qpath, true);
                 self.nbsp();
                 self.word("{");
-                let empty = fields.is_empty() && !etc;
+                let empty = fields.is_empty() && etc.is_none();
                 if !empty {
                     self.space();
                 }
                 self.commasep_cmnt(Consistent, fields, |s, f| s.print_patfield(f), |f| f.pat.span);
-                if etc {
+                if etc.is_some() {
                     if !fields.is_empty() {
                         self.word_space(",");
                     }
@@ -2379,7 +2379,7 @@ impl<'a> State<'a> {
                     self.print_type(default);
                 }
             }
-            GenericParamKind::Const { ty, ref default, synthetic: _ } => {
+            GenericParamKind::Const { ty, ref default } => {
                 self.word_space(":");
                 self.print_type(ty);
                 if let Some(default) = default {
diff --git a/compiler/rustc_hir_typeck/Cargo.toml b/compiler/rustc_hir_typeck/Cargo.toml
index 5af0c6134ca..f00125c3e09 100644
--- a/compiler/rustc_hir_typeck/Cargo.toml
+++ b/compiler/rustc_hir_typeck/Cargo.toml
@@ -5,7 +5,7 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-itertools.workspace = true
+itertools = "0.12"
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_attr_parsing = { path = "../rustc_attr_parsing" }
@@ -25,5 +25,5 @@ rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
 rustc_trait_selection = { path = "../rustc_trait_selection" }
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
-tracing.workspace = true
+tracing = "0.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_hir_typeck/src/coercion.rs b/compiler/rustc_hir_typeck/src/coercion.rs
index e66601631fc..b99f811db1a 100644
--- a/compiler/rustc_hir_typeck/src/coercion.rs
+++ b/compiler/rustc_hir_typeck/src/coercion.rs
@@ -1897,7 +1897,7 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> {
                     fcx.suggest_semicolon_at_end(cond_expr.span, &mut err);
                 }
             }
-        };
+        }
 
         // If this is due to an explicit `return`, suggest adding a return type.
         if let Some((fn_id, fn_decl)) = fcx.get_fn_decl(block_or_return_id)
diff --git a/compiler/rustc_hir_typeck/src/expr.rs b/compiler/rustc_hir_typeck/src/expr.rs
index a652e08905a..7adbee7ff28 100644
--- a/compiler/rustc_hir_typeck/src/expr.rs
+++ b/compiler/rustc_hir_typeck/src/expr.rs
@@ -2585,12 +2585,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 .filter(|item| item.is_fn() && !item.is_method())
                 .filter_map(|item| {
                     // Only assoc fns that return `Self`
-                    let fn_sig = self.tcx.fn_sig(item.def_id).skip_binder();
-                    let ret_ty = fn_sig.output();
-                    let ret_ty = self.tcx.normalize_erasing_late_bound_regions(
-                        self.typing_env(self.param_env),
-                        ret_ty,
-                    );
+                    let fn_sig = self
+                        .tcx
+                        .fn_sig(item.def_id)
+                        .instantiate(self.tcx, self.fresh_args_for_item(span, item.def_id));
+                    let ret_ty = self.tcx.instantiate_bound_regions_with_erased(fn_sig.output());
                     if !self.can_eq(self.param_env, ret_ty, adt_ty) {
                         return None;
                     }
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
index 5aec50c8b53..94b635c41b4 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
@@ -1912,7 +1912,22 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             hir::StmtKind::Expr(ref expr) => {
                 // Check with expected type of `()`.
                 self.check_expr_has_type_or_error(expr, self.tcx.types.unit, |err| {
-                    if expr.can_have_side_effects() {
+                    if self.is_next_stmt_expr_continuation(stmt.hir_id)
+                        && let hir::ExprKind::Match(..) | hir::ExprKind::If(..) = expr.kind
+                    {
+                        // We have something like `match () { _ => true } && true`. Suggest
+                        // wrapping in parentheses. We find the statement or expression
+                        // following the `match` (`&& true`) and see if it is something that
+                        // can reasonably be interpreted as a binop following an expression.
+                        err.multipart_suggestion(
+                            "parentheses are required to parse this as an expression",
+                            vec![
+                                (expr.span.shrink_to_lo(), "(".to_string()),
+                                (expr.span.shrink_to_hi(), ")".to_string()),
+                            ],
+                            Applicability::MachineApplicable,
+                        );
+                    } else if expr.can_have_side_effects() {
                         self.suggest_semicolon_at_end(expr.span, err);
                     }
                 });
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
index aca3840712e..84ea2ec0f8a 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
@@ -1,3 +1,4 @@
+// ignore-tidy-filelength
 use core::cmp::min;
 use core::iter;
 
@@ -766,56 +767,121 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         needs_block: bool,
         parent_is_closure: bool,
     ) {
-        if expected.is_unit() {
-            // `BlockTailExpression` only relevant if the tail expr would be
-            // useful on its own.
-            match expression.kind {
-                ExprKind::Call(..)
-                | ExprKind::MethodCall(..)
-                | ExprKind::Loop(..)
-                | ExprKind::If(..)
-                | ExprKind::Match(..)
-                | ExprKind::Block(..)
-                    if expression.can_have_side_effects()
-                        // If the expression is from an external macro, then do not suggest
-                        // adding a semicolon, because there's nowhere to put it.
-                        // See issue #81943.
-                        && !expression.span.in_external_macro(self.tcx.sess.source_map()) =>
+        if !expected.is_unit() {
+            return;
+        }
+        // `BlockTailExpression` only relevant if the tail expr would be
+        // useful on its own.
+        match expression.kind {
+            ExprKind::Call(..)
+            | ExprKind::MethodCall(..)
+            | ExprKind::Loop(..)
+            | ExprKind::If(..)
+            | ExprKind::Match(..)
+            | ExprKind::Block(..)
+                if expression.can_have_side_effects()
+                    // If the expression is from an external macro, then do not suggest
+                    // adding a semicolon, because there's nowhere to put it.
+                    // See issue #81943.
+                    && !expression.span.in_external_macro(self.tcx.sess.source_map()) =>
+            {
+                if needs_block {
+                    err.multipart_suggestion(
+                        "consider using a semicolon here",
+                        vec![
+                            (expression.span.shrink_to_lo(), "{ ".to_owned()),
+                            (expression.span.shrink_to_hi(), "; }".to_owned()),
+                        ],
+                        Applicability::MachineApplicable,
+                    );
+                } else if let hir::Node::Block(block) = self.tcx.parent_hir_node(expression.hir_id)
+                    && let hir::Node::Expr(expr) = self.tcx.parent_hir_node(block.hir_id)
+                    && let hir::Node::Expr(if_expr) = self.tcx.parent_hir_node(expr.hir_id)
+                    && let hir::ExprKind::If(_cond, _then, Some(_else)) = if_expr.kind
+                    && let hir::Node::Stmt(stmt) = self.tcx.parent_hir_node(if_expr.hir_id)
+                    && let hir::StmtKind::Expr(_) = stmt.kind
+                    && self.is_next_stmt_expr_continuation(stmt.hir_id)
                 {
-                    if needs_block {
-                        err.multipart_suggestion(
-                            "consider using a semicolon here",
-                            vec![
-                                (expression.span.shrink_to_lo(), "{ ".to_owned()),
-                                (expression.span.shrink_to_hi(), "; }".to_owned()),
-                            ],
-                            Applicability::MachineApplicable,
-                        );
-                    } else {
-                        err.span_suggestion(
-                            expression.span.shrink_to_hi(),
-                            "consider using a semicolon here",
-                            ";",
-                            Applicability::MachineApplicable,
-                        );
-                    }
+                    err.multipart_suggestion(
+                        "parentheses are required to parse this as an expression",
+                        vec![
+                            (stmt.span.shrink_to_lo(), "(".to_string()),
+                            (stmt.span.shrink_to_hi(), ")".to_string()),
+                        ],
+                        Applicability::MachineApplicable,
+                    );
+                } else {
+                    err.span_suggestion(
+                        expression.span.shrink_to_hi(),
+                        "consider using a semicolon here",
+                        ";",
+                        Applicability::MachineApplicable,
+                    );
                 }
-                ExprKind::Path(..) | ExprKind::Lit(_)
-                    if parent_is_closure
-                        && !expression.span.in_external_macro(self.tcx.sess.source_map()) =>
+            }
+            ExprKind::Path(..) | ExprKind::Lit(_)
+                if parent_is_closure
+                    && !expression.span.in_external_macro(self.tcx.sess.source_map()) =>
+            {
+                err.span_suggestion_verbose(
+                    expression.span.shrink_to_lo(),
+                    "consider ignoring the value",
+                    "_ = ",
+                    Applicability::MachineApplicable,
+                );
+            }
+            _ => {
+                if let hir::Node::Block(block) = self.tcx.parent_hir_node(expression.hir_id)
+                    && let hir::Node::Expr(expr) = self.tcx.parent_hir_node(block.hir_id)
+                    && let hir::Node::Expr(if_expr) = self.tcx.parent_hir_node(expr.hir_id)
+                    && let hir::ExprKind::If(_cond, _then, Some(_else)) = if_expr.kind
+                    && let hir::Node::Stmt(stmt) = self.tcx.parent_hir_node(if_expr.hir_id)
+                    && let hir::StmtKind::Expr(_) = stmt.kind
+                    && self.is_next_stmt_expr_continuation(stmt.hir_id)
                 {
-                    err.span_suggestion_verbose(
-                        expression.span.shrink_to_lo(),
-                        "consider ignoring the value",
-                        "_ = ",
+                    // The error is pointing at an arm of an if-expression, and we want to get the
+                    // `Span` of the whole if-expression for the suggestion. This only works for a
+                    // single level of nesting, which is fine.
+                    // We have something like `if true { false } else { true } && true`. Suggest
+                    // wrapping in parentheses. We find the statement or expression following the
+                    // `if` (`&& true`) and see if it is something that can reasonably be
+                    // interpreted as a binop following an expression.
+                    err.multipart_suggestion(
+                        "parentheses are required to parse this as an expression",
+                        vec![
+                            (stmt.span.shrink_to_lo(), "(".to_string()),
+                            (stmt.span.shrink_to_hi(), ")".to_string()),
+                        ],
                         Applicability::MachineApplicable,
                     );
                 }
-                _ => (),
             }
         }
     }
 
+    pub(crate) fn is_next_stmt_expr_continuation(&self, hir_id: HirId) -> bool {
+        if let hir::Node::Block(b) = self.tcx.parent_hir_node(hir_id)
+            && let mut stmts = b.stmts.iter().skip_while(|s| s.hir_id != hir_id)
+            && let Some(_) = stmts.next() // The statement the statement that was passed in
+            && let Some(next) = match (stmts.next(), b.expr) { // The following statement
+                (Some(next), _) => match next.kind {
+                    hir::StmtKind::Expr(next) | hir::StmtKind::Semi(next) => Some(next),
+                    _ => None,
+                },
+                (None, Some(next)) => Some(next),
+                _ => None,
+            }
+            && let hir::ExprKind::AddrOf(..) // prev_stmt && next
+                | hir::ExprKind::Unary(..) // prev_stmt * next
+                | hir::ExprKind::Err(_) = next.kind
+        // prev_stmt + next
+        {
+            true
+        } else {
+            false
+        }
+    }
+
     /// A possible error is to forget to add a return type that is needed:
     ///
     /// ```compile_fail,E0308
diff --git a/compiler/rustc_hir_typeck/src/pat.rs b/compiler/rustc_hir_typeck/src/pat.rs
index 7dc736e5e6b..f735c0a4160 100644
--- a/compiler/rustc_hir_typeck/src/pat.rs
+++ b/compiler/rustc_hir_typeck/src/pat.rs
@@ -605,7 +605,15 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             },
             PatKind::Struct(_, fields, has_rest_pat) => match opt_path_res.unwrap() {
                 Ok(ResolvedPat { ty, kind: ResolvedPatKind::Struct { variant } }) => self
-                    .check_pat_struct(pat, fields, has_rest_pat, ty, variant, expected, pat_info),
+                    .check_pat_struct(
+                        pat,
+                        fields,
+                        has_rest_pat.is_some(),
+                        ty,
+                        variant,
+                        expected,
+                        pat_info,
+                    ),
                 Err(guar) => {
                     let ty_err = Ty::new_error(self.tcx, guar);
                     for field in fields {
@@ -2428,7 +2436,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let len = unmentioned_fields.len();
         let (prefix, postfix, sp) = match fields {
             [] => match &pat.kind {
-                PatKind::Struct(path, [], false) => {
+                PatKind::Struct(path, [], None) => {
                     (" { ", " }", path.span().shrink_to_hi().until(pat.span.shrink_to_hi()))
                 }
                 _ => return err,
diff --git a/compiler/rustc_incremental/Cargo.toml b/compiler/rustc_incremental/Cargo.toml
index 8d7f2eb8414..db0a5841887 100644
--- a/compiler/rustc_incremental/Cargo.toml
+++ b/compiler/rustc_incremental/Cargo.toml
@@ -19,6 +19,6 @@ rustc_middle = { path = "../rustc_middle" }
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
-thin-vec.workspace = true
-tracing.workspace = true
+thin-vec = "0.2.12"
+tracing = "0.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_index/src/interval.rs b/compiler/rustc_index/src/interval.rs
index 0225c5c4f32..dda5253e7c5 100644
--- a/compiler/rustc_index/src/interval.rs
+++ b/compiler/rustc_index/src/interval.rs
@@ -140,6 +140,30 @@ impl<I: Idx> IntervalSet<I> {
         result
     }
 
+    /// Specialized version of `insert` when we know that the inserted point is *after* any
+    /// contained.
+    pub fn append(&mut self, point: I) {
+        let point = point.index() as u32;
+
+        if let Some((_, last_end)) = self.map.last_mut() {
+            assert!(*last_end <= point);
+            if point == *last_end {
+                // The point is already in the set.
+            } else if point == *last_end + 1 {
+                *last_end = point;
+            } else {
+                self.map.push((point, point));
+            }
+        } else {
+            self.map.push((point, point));
+        }
+
+        debug_assert!(
+            self.check_invariants(),
+            "wrong intervals after append {point:?} to {self:?}"
+        );
+    }
+
     pub fn contains(&self, needle: I) -> bool {
         let needle = needle.index() as u32;
         let Some(last) = self.map.partition_point(|r| r.0 <= needle).checked_sub(1) else {
@@ -176,6 +200,32 @@ impl<I: Idx> IntervalSet<I> {
         })
     }
 
+    pub fn disjoint(&self, other: &IntervalSet<I>) -> bool
+    where
+        I: Step,
+    {
+        let helper = move || {
+            let mut self_iter = self.iter_intervals();
+            let mut other_iter = other.iter_intervals();
+
+            let mut self_current = self_iter.next()?;
+            let mut other_current = other_iter.next()?;
+
+            loop {
+                if self_current.end <= other_current.start {
+                    self_current = self_iter.next()?;
+                    continue;
+                }
+                if other_current.end <= self_current.start {
+                    other_current = other_iter.next()?;
+                    continue;
+                }
+                return Some(false);
+            }
+        };
+        helper().unwrap_or(true)
+    }
+
     pub fn is_empty(&self) -> bool {
         self.map.is_empty()
     }
@@ -325,6 +375,10 @@ impl<R: Idx, C: Step + Idx> SparseIntervalMatrix<R, C> {
         self.ensure_row(row).insert(point)
     }
 
+    pub fn append(&mut self, row: R, point: C) {
+        self.ensure_row(row).append(point)
+    }
+
     pub fn contains(&self, row: R, point: C) -> bool {
         self.row(row).is_some_and(|r| r.contains(point))
     }
diff --git a/compiler/rustc_index_macros/Cargo.toml b/compiler/rustc_index_macros/Cargo.toml
index 8593bde2615..34f3109a526 100644
--- a/compiler/rustc_index_macros/Cargo.toml
+++ b/compiler/rustc_index_macros/Cargo.toml
@@ -8,8 +8,8 @@ proc-macro = true
 
 [dependencies]
 # tidy-alphabetical-start
-proc-macro2.workspace = true
-quote.workspace = true
+proc-macro2 = "1"
+quote = "1"
 syn = { version = "2.0.9", features = ["full", "extra-traits"] }
 # tidy-alphabetical-end
 
diff --git a/compiler/rustc_infer/Cargo.toml b/compiler/rustc_infer/Cargo.toml
index 6d97fa6af1f..08c03614884 100644
--- a/compiler/rustc_infer/Cargo.toml
+++ b/compiler/rustc_infer/Cargo.toml
@@ -18,6 +18,6 @@ rustc_middle = { path = "../rustc_middle" }
 rustc_span = { path = "../rustc_span" }
 rustc_type_ir = { path = "../rustc_type_ir" }
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
-thin-vec.workspace = true
-tracing.workspace = true
+thin-vec = "0.2.12"
+tracing = "0.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_infer/src/infer/context.rs b/compiler/rustc_infer/src/infer/context.rs
index bb9c8850093..8265fccabc9 100644
--- a/compiler/rustc_infer/src/infer/context.rs
+++ b/compiler/rustc_infer/src/infer/context.rs
@@ -1,4 +1,4 @@
-///! Definition of `InferCtxtLike` from the librarified type layer.
+//! Definition of `InferCtxtLike` from the librarified type layer.
 use rustc_hir::def_id::DefId;
 use rustc_middle::traits::ObligationCause;
 use rustc_middle::ty::relate::RelateResult;
diff --git a/compiler/rustc_interface/Cargo.toml b/compiler/rustc_interface/Cargo.toml
index 40152e78f8a..473ac5e0cea 100644
--- a/compiler/rustc_interface/Cargo.toml
+++ b/compiler/rustc_interface/Cargo.toml
@@ -46,7 +46,7 @@ rustc_thread_pool = { path = "../rustc_thread_pool" }
 rustc_trait_selection = { path = "../rustc_trait_selection" }
 rustc_traits = { path = "../rustc_traits" }
 rustc_ty_utils = { path = "../rustc_ty_utils" }
-tracing.workspace = true
+tracing = "0.1"
 # tidy-alphabetical-end
 
 [dev-dependencies]
diff --git a/compiler/rustc_interface/src/interface.rs b/compiler/rustc_interface/src/interface.rs
index 8f131f45bbd..4c820b8877b 100644
--- a/compiler/rustc_interface/src/interface.rs
+++ b/compiler/rustc_interface/src/interface.rs
@@ -13,7 +13,7 @@ use rustc_lint::LintStore;
 use rustc_middle::ty;
 use rustc_middle::ty::CurrentGcx;
 use rustc_middle::util::Providers;
-use rustc_parse::new_parser_from_source_str;
+use rustc_parse::new_parser_from_simple_source_str;
 use rustc_parse::parser::attr::AllowLeadingUnsafe;
 use rustc_query_impl::QueryCtxt;
 use rustc_query_system::query::print_query_stack;
@@ -68,7 +68,7 @@ pub(crate) fn parse_cfg(dcx: DiagCtxtHandle<'_>, cfgs: Vec<String>) -> Cfg {
                 };
             }
 
-            match new_parser_from_source_str(&psess, filename, s.to_string()) {
+            match new_parser_from_simple_source_str(&psess, filename, s.to_string()) {
                 Ok(mut parser) => match parser.parse_meta_item(AllowLeadingUnsafe::No) {
                     Ok(meta_item) if parser.token == token::Eof => {
                         if meta_item.path.segments.len() != 1 {
@@ -166,7 +166,7 @@ pub(crate) fn parse_check_cfg(dcx: DiagCtxtHandle<'_>, specs: Vec<String>) -> Ch
             error!("expected `cfg(name, values(\"value1\", \"value2\", ... \"valueN\"))`")
         };
 
-        let mut parser = match new_parser_from_source_str(&psess, filename, s.to_string()) {
+        let mut parser = match new_parser_from_simple_source_str(&psess, filename, s.to_string()) {
             Ok(parser) => parser,
             Err(errs) => {
                 errs.into_iter().for_each(|err| err.cancel());
diff --git a/compiler/rustc_interface/src/passes.rs b/compiler/rustc_interface/src/passes.rs
index bc5ef04079e..ca8c10311fb 100644
--- a/compiler/rustc_interface/src/passes.rs
+++ b/compiler/rustc_interface/src/passes.rs
@@ -41,7 +41,7 @@ use rustc_span::{
     Symbol, sym,
 };
 use rustc_target::spec::PanicStrategy;
-use rustc_trait_selection::traits;
+use rustc_trait_selection::{solve, traits};
 use tracing::{info, instrument};
 
 use crate::interface::Compiler;
@@ -895,6 +895,7 @@ pub static DEFAULT_QUERY_PROVIDERS: LazyLock<Providers> = LazyLock::new(|| {
     rustc_hir_typeck::provide(providers);
     ty::provide(providers);
     traits::provide(providers);
+    solve::provide(providers);
     rustc_passes::provide(providers);
     rustc_traits::provide(providers);
     rustc_ty_utils::provide(providers);
diff --git a/compiler/rustc_lexer/Cargo.toml b/compiler/rustc_lexer/Cargo.toml
index e0019fb1821..343b81bd171 100644
--- a/compiler/rustc_lexer/Cargo.toml
+++ b/compiler/rustc_lexer/Cargo.toml
@@ -14,7 +14,7 @@ Rust lexer used by rustc. No stability guarantees are provided.
 
 # Note that this crate purposefully does not depend on other rustc crates
 [dependencies]
-memchr.workspace = true
+memchr = "2.7.4"
 unicode-properties = { version = "0.1.0", default-features = false, features = ["emoji"] }
 unicode-xid = "0.2.0"
 
diff --git a/compiler/rustc_lexer/src/lib.rs b/compiler/rustc_lexer/src/lib.rs
index d10b1920343..c29ab569f47 100644
--- a/compiler/rustc_lexer/src/lib.rs
+++ b/compiler/rustc_lexer/src/lib.rs
@@ -331,24 +331,37 @@ pub fn is_whitespace(c: char) -> bool {
 
     matches!(
         c,
-        // Usual ASCII suspects
-        '\u{0009}'   // \t
-        | '\u{000A}' // \n
+        // End-of-line characters
+        | '\u{000A}' // line feed (\n)
         | '\u{000B}' // vertical tab
         | '\u{000C}' // form feed
-        | '\u{000D}' // \r
-        | '\u{0020}' // space
-
-        // NEXT LINE from latin1
-        | '\u{0085}'
+        | '\u{000D}' // carriage return (\r)
+        | '\u{0085}' // next line (from latin1)
+        | '\u{2028}' // LINE SEPARATOR
+        | '\u{2029}' // PARAGRAPH SEPARATOR
 
-        // Bidi markers
+        // `Default_Ignorable_Code_Point` characters
         | '\u{200E}' // LEFT-TO-RIGHT MARK
         | '\u{200F}' // RIGHT-TO-LEFT MARK
 
-        // Dedicated whitespace characters from Unicode
-        | '\u{2028}' // LINE SEPARATOR
-        | '\u{2029}' // PARAGRAPH SEPARATOR
+        // Horizontal space characters
+        | '\u{0009}'   // tab (\t)
+        | '\u{0020}' // space
+    )
+}
+
+/// True if `c` is considered horizontal whitespace according to Rust language definition.
+pub fn is_horizontal_whitespace(c: char) -> bool {
+    // This is Pattern_White_Space.
+    //
+    // Note that this set is stable (ie, it doesn't change with different
+    // Unicode versions), so it's ok to just hard-code the values.
+
+    matches!(
+        c,
+        // Horizontal space characters
+        '\u{0009}'   // tab (\t)
+        | '\u{0020}' // space
     )
 }
 
@@ -538,7 +551,7 @@ impl Cursor<'_> {
         debug_assert!(length_opening >= 3);
 
         // whitespace between the opening and the infostring.
-        self.eat_while(|ch| ch != '\n' && is_whitespace(ch));
+        self.eat_while(|ch| ch != '\n' && is_horizontal_whitespace(ch));
 
         // copied from `eat_identifier`, but allows `-` and `.` in infostring to allow something like
         // `---Cargo.toml` as a valid opener
@@ -547,7 +560,7 @@ impl Cursor<'_> {
             self.eat_while(|c| is_id_continue(c) || c == '-' || c == '.');
         }
 
-        self.eat_while(|ch| ch != '\n' && is_whitespace(ch));
+        self.eat_while(|ch| ch != '\n' && is_horizontal_whitespace(ch));
         let invalid_infostring = self.first() != '\n';
 
         let mut found = false;
@@ -588,7 +601,7 @@ impl Cursor<'_> {
                 // on a standalone line. Might be wrong.
                 while let Some(closing) = rest.find("---") {
                     let preceding_chars_start = rest[..closing].rfind("\n").map_or(0, |i| i + 1);
-                    if rest[preceding_chars_start..closing].chars().all(is_whitespace) {
+                    if rest[preceding_chars_start..closing].chars().all(is_horizontal_whitespace) {
                         // candidate found
                         potential_closing = Some(closing);
                         break;
diff --git a/compiler/rustc_lint/Cargo.toml b/compiler/rustc_lint/Cargo.toml
index 7900e4b9ab2..3a50aac50cb 100644
--- a/compiler/rustc_lint/Cargo.toml
+++ b/compiler/rustc_lint/Cargo.toml
@@ -5,6 +5,7 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
+bitflags = "2.4.1"
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_pretty = { path = "../rustc_ast_pretty" }
@@ -24,6 +25,6 @@ rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
 rustc_trait_selection = { path = "../rustc_trait_selection" }
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
-tracing.workspace = true
+tracing = "0.1"
 unicode-security = "0.1.0"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_lint/src/foreign_modules.rs b/compiler/rustc_lint/src/foreign_modules.rs
index 3267e70f1de..ad73e15e31f 100644
--- a/compiler/rustc_lint/src/foreign_modules.rs
+++ b/compiler/rustc_lint/src/foreign_modules.rs
@@ -136,7 +136,6 @@ impl ClashingExternDeclarations {
             ty::TypingEnv::non_body_analysis(tcx, this_fi.owner_id),
             existing_decl_ty,
             this_decl_ty,
-            types::CItemKind::Declaration,
         ) {
             let orig = name_of_extern_decl(tcx, existing_did);
 
@@ -214,10 +213,9 @@ fn structurally_same_type<'tcx>(
     typing_env: ty::TypingEnv<'tcx>,
     a: Ty<'tcx>,
     b: Ty<'tcx>,
-    ckind: types::CItemKind,
 ) -> bool {
     let mut seen_types = UnordSet::default();
-    let result = structurally_same_type_impl(&mut seen_types, tcx, typing_env, a, b, ckind);
+    let result = structurally_same_type_impl(&mut seen_types, tcx, typing_env, a, b);
     if cfg!(debug_assertions) && result {
         // Sanity-check: must have same ABI, size and alignment.
         // `extern` blocks cannot be generic, so we'll always get a layout here.
@@ -236,7 +234,6 @@ fn structurally_same_type_impl<'tcx>(
     typing_env: ty::TypingEnv<'tcx>,
     a: Ty<'tcx>,
     b: Ty<'tcx>,
-    ckind: types::CItemKind,
 ) -> bool {
     debug!("structurally_same_type_impl(tcx, a = {:?}, b = {:?})", a, b);
 
@@ -307,7 +304,6 @@ fn structurally_same_type_impl<'tcx>(
                                 typing_env,
                                 tcx.type_of(a_did).instantiate(tcx, a_gen_args),
                                 tcx.type_of(b_did).instantiate(tcx, b_gen_args),
-                                ckind,
                             )
                         },
                     )
@@ -315,25 +311,19 @@ fn structurally_same_type_impl<'tcx>(
                 (ty::Array(a_ty, a_len), ty::Array(b_ty, b_len)) => {
                     // For arrays, we also check the length.
                     a_len == b_len
-                        && structurally_same_type_impl(
-                            seen_types, tcx, typing_env, *a_ty, *b_ty, ckind,
-                        )
+                        && structurally_same_type_impl(seen_types, tcx, typing_env, *a_ty, *b_ty)
                 }
                 (ty::Slice(a_ty), ty::Slice(b_ty)) => {
-                    structurally_same_type_impl(seen_types, tcx, typing_env, *a_ty, *b_ty, ckind)
+                    structurally_same_type_impl(seen_types, tcx, typing_env, *a_ty, *b_ty)
                 }
                 (ty::RawPtr(a_ty, a_mutbl), ty::RawPtr(b_ty, b_mutbl)) => {
                     a_mutbl == b_mutbl
-                        && structurally_same_type_impl(
-                            seen_types, tcx, typing_env, *a_ty, *b_ty, ckind,
-                        )
+                        && structurally_same_type_impl(seen_types, tcx, typing_env, *a_ty, *b_ty)
                 }
                 (ty::Ref(_a_region, a_ty, a_mut), ty::Ref(_b_region, b_ty, b_mut)) => {
                     // For structural sameness, we don't need the region to be same.
                     a_mut == b_mut
-                        && structurally_same_type_impl(
-                            seen_types, tcx, typing_env, *a_ty, *b_ty, ckind,
-                        )
+                        && structurally_same_type_impl(seen_types, tcx, typing_env, *a_ty, *b_ty)
                 }
                 (ty::FnDef(..), ty::FnDef(..)) => {
                     let a_poly_sig = a.fn_sig(tcx);
@@ -347,7 +337,7 @@ fn structurally_same_type_impl<'tcx>(
                     (a_sig.abi, a_sig.safety, a_sig.c_variadic)
                         == (b_sig.abi, b_sig.safety, b_sig.c_variadic)
                         && a_sig.inputs().iter().eq_by(b_sig.inputs().iter(), |a, b| {
-                            structurally_same_type_impl(seen_types, tcx, typing_env, *a, *b, ckind)
+                            structurally_same_type_impl(seen_types, tcx, typing_env, *a, *b)
                         })
                         && structurally_same_type_impl(
                             seen_types,
@@ -355,7 +345,6 @@ fn structurally_same_type_impl<'tcx>(
                             typing_env,
                             a_sig.output(),
                             b_sig.output(),
-                            ckind,
                         )
                 }
                 (ty::Tuple(..), ty::Tuple(..)) => {
@@ -383,14 +372,14 @@ fn structurally_same_type_impl<'tcx>(
                 // An Adt and a primitive or pointer type. This can be FFI-safe if non-null
                 // enum layout optimisation is being applied.
                 (ty::Adt(..) | ty::Pat(..), _) if is_primitive_or_pointer(b) => {
-                    if let Some(a_inner) = types::repr_nullable_ptr(tcx, typing_env, a, ckind) {
+                    if let Some(a_inner) = types::repr_nullable_ptr(tcx, typing_env, a) {
                         a_inner == b
                     } else {
                         false
                     }
                 }
                 (_, ty::Adt(..) | ty::Pat(..)) if is_primitive_or_pointer(a) => {
-                    if let Some(b_inner) = types::repr_nullable_ptr(tcx, typing_env, b, ckind) {
+                    if let Some(b_inner) = types::repr_nullable_ptr(tcx, typing_env, b) {
                         b_inner == a
                     } else {
                         false
diff --git a/compiler/rustc_lint/src/lib.rs b/compiler/rustc_lint/src/lib.rs
index bdbac7fc4d1..9bb53fea54a 100644
--- a/compiler/rustc_lint/src/lib.rs
+++ b/compiler/rustc_lint/src/lib.rs
@@ -194,8 +194,7 @@ late_lint_methods!(
             DefaultCouldBeDerived: DefaultCouldBeDerived::default(),
             DerefIntoDynSupertrait: DerefIntoDynSupertrait,
             DropForgetUseless: DropForgetUseless,
-            ImproperCTypesDeclarations: ImproperCTypesDeclarations,
-            ImproperCTypesDefinitions: ImproperCTypesDefinitions,
+            ImproperCTypesLint: ImproperCTypesLint,
             InvalidFromUtf8: InvalidFromUtf8,
             VariantSizeDifferences: VariantSizeDifferences,
             PathStatements: PathStatements,
diff --git a/compiler/rustc_lint/src/types.rs b/compiler/rustc_lint/src/types.rs
index f8a692313f0..a72b802eb5d 100644
--- a/compiler/rustc_lint/src/types.rs
+++ b/compiler/rustc_lint/src/types.rs
@@ -1,35 +1,28 @@
 use std::iter;
-use std::ops::ControlFlow;
 
-use rustc_abi::{BackendRepr, TagEncoding, VariantIdx, Variants, WrappingRange};
-use rustc_data_structures::fx::FxHashSet;
-use rustc_errors::DiagMessage;
-use rustc_hir::intravisit::VisitorExt;
-use rustc_hir::{AmbigArg, Expr, ExprKind, HirId, LangItem};
+use rustc_abi::{BackendRepr, TagEncoding, Variants, WrappingRange};
+use rustc_hir::{Expr, ExprKind, HirId, LangItem};
 use rustc_middle::bug;
 use rustc_middle::ty::layout::{LayoutOf, SizeSkeleton};
-use rustc_middle::ty::{
-    self, Adt, AdtKind, GenericArgsRef, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable,
-    TypeVisitableExt,
-};
+use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
 use rustc_session::{declare_lint, declare_lint_pass, impl_lint_pass};
-use rustc_span::def_id::LocalDefId;
 use rustc_span::{Span, Symbol, sym};
 use tracing::debug;
 use {rustc_ast as ast, rustc_hir as hir};
 
-mod improper_ctypes;
+mod improper_ctypes; // these filed do the implementation for ImproperCTypesDefinitions,ImproperCTypesDeclarations
+pub(crate) use improper_ctypes::ImproperCTypesLint;
 
 use crate::lints::{
     AmbiguousWidePointerComparisons, AmbiguousWidePointerComparisonsAddrMetadataSuggestion,
     AmbiguousWidePointerComparisonsAddrSuggestion, AmbiguousWidePointerComparisonsCastSuggestion,
     AmbiguousWidePointerComparisonsExpectSuggestion, AtomicOrderingFence, AtomicOrderingLoad,
-    AtomicOrderingStore, ImproperCTypes, InvalidAtomicOrderingDiag, InvalidNanComparisons,
+    AtomicOrderingStore, InvalidAtomicOrderingDiag, InvalidNanComparisons,
     InvalidNanComparisonsSuggestion, UnpredictableFunctionPointerComparisons,
-    UnpredictableFunctionPointerComparisonsSuggestion, UnusedComparisons, UsesPowerAlignment,
+    UnpredictableFunctionPointerComparisonsSuggestion, UnusedComparisons,
     VariantSizeDifferencesDiag,
 };
-use crate::{LateContext, LateLintPass, LintContext, fluent_generated as fluent};
+use crate::{LateContext, LateLintPass, LintContext};
 
 mod literal;
 
@@ -690,144 +683,6 @@ impl<'tcx> LateLintPass<'tcx> for TypeLimits {
     }
 }
 
-declare_lint! {
-    /// The `improper_ctypes` lint detects incorrect use of types in foreign
-    /// modules.
-    ///
-    /// ### Example
-    ///
-    /// ```rust
-    /// unsafe extern "C" {
-    ///     static STATIC: String;
-    /// }
-    /// ```
-    ///
-    /// {{produces}}
-    ///
-    /// ### Explanation
-    ///
-    /// The compiler has several checks to verify that types used in `extern`
-    /// blocks are safe and follow certain rules to ensure proper
-    /// compatibility with the foreign interfaces. This lint is issued when it
-    /// detects a probable mistake in a definition. The lint usually should
-    /// provide a description of the issue, along with possibly a hint on how
-    /// to resolve it.
-    IMPROPER_CTYPES,
-    Warn,
-    "proper use of libc types in foreign modules"
-}
-
-declare_lint_pass!(ImproperCTypesDeclarations => [IMPROPER_CTYPES]);
-
-declare_lint! {
-    /// The `improper_ctypes_definitions` lint detects incorrect use of
-    /// [`extern` function] definitions.
-    ///
-    /// [`extern` function]: https://doc.rust-lang.org/reference/items/functions.html#extern-function-qualifier
-    ///
-    /// ### Example
-    ///
-    /// ```rust
-    /// # #![allow(unused)]
-    /// pub extern "C" fn str_type(p: &str) { }
-    /// ```
-    ///
-    /// {{produces}}
-    ///
-    /// ### Explanation
-    ///
-    /// There are many parameter and return types that may be specified in an
-    /// `extern` function that are not compatible with the given ABI. This
-    /// lint is an alert that these types should not be used. The lint usually
-    /// should provide a description of the issue, along with possibly a hint
-    /// on how to resolve it.
-    IMPROPER_CTYPES_DEFINITIONS,
-    Warn,
-    "proper use of libc types in foreign item definitions"
-}
-
-declare_lint! {
-    /// The `uses_power_alignment` lint detects specific `repr(C)`
-    /// aggregates on AIX.
-    /// In its platform C ABI, AIX uses the "power" (as in PowerPC) alignment
-    /// rule (detailed in https://www.ibm.com/docs/en/xl-c-and-cpp-aix/16.1?topic=data-using-alignment-modes#alignment),
-    /// which can also be set for XLC by `#pragma align(power)` or
-    /// `-qalign=power`. Aggregates with a floating-point type as the
-    /// recursively first field (as in "at offset 0") modify the layout of
-    /// *subsequent* fields of the associated structs to use an alignment value
-    /// where the floating-point type is aligned on a 4-byte boundary.
-    ///
-    /// Effectively, subsequent floating-point fields act as-if they are `repr(packed(4))`. This
-    /// would be unsound to do in a `repr(C)` type without all the restrictions that come with
-    /// `repr(packed)`. Rust instead chooses a layout that maintains soundness of Rust code, at the
-    /// expense of incompatibility with C code.
-    ///
-    /// ### Example
-    ///
-    /// ```rust,ignore (fails on non-powerpc64-ibm-aix)
-    /// #[repr(C)]
-    /// pub struct Floats {
-    ///     a: f64,
-    ///     b: u8,
-    ///     c: f64,
-    /// }
-    /// ```
-    ///
-    /// This will produce:
-    ///
-    /// ```text
-    /// warning: repr(C) does not follow the power alignment rule. This may affect platform C ABI compatibility for this type
-    ///  --> <source>:5:3
-    ///   |
-    /// 5 |   c: f64,
-    ///   |   ^^^^^^
-    ///   |
-    ///   = note: `#[warn(uses_power_alignment)]` on by default
-    /// ```
-    ///
-    /// ### Explanation
-    ///
-    /// The power alignment rule specifies that the above struct has the
-    /// following alignment:
-    ///  - offset_of!(Floats, a) == 0
-    ///  - offset_of!(Floats, b) == 8
-    ///  - offset_of!(Floats, c) == 12
-    ///
-    /// However, Rust currently aligns `c` at `offset_of!(Floats, c) == 16`.
-    /// Using offset 12 would be unsound since `f64` generally must be 8-aligned on this target.
-    /// Thus, a warning is produced for the above struct.
-    USES_POWER_ALIGNMENT,
-    Warn,
-    "Structs do not follow the power alignment rule under repr(C)"
-}
-
-declare_lint_pass!(ImproperCTypesDefinitions => [IMPROPER_CTYPES_DEFINITIONS, USES_POWER_ALIGNMENT]);
-
-#[derive(Clone, Copy)]
-pub(crate) enum CItemKind {
-    Declaration,
-    Definition,
-}
-
-struct ImproperCTypesVisitor<'a, 'tcx> {
-    cx: &'a LateContext<'tcx>,
-    mode: CItemKind,
-}
-
-/// Accumulator for recursive ffi type checking
-struct CTypesVisitorState<'tcx> {
-    cache: FxHashSet<Ty<'tcx>>,
-    /// The original type being checked, before we recursed
-    /// to any other types it contains.
-    base_ty: Ty<'tcx>,
-}
-
-enum FfiResult<'tcx> {
-    FfiSafe,
-    FfiPhantom(Ty<'tcx>),
-    FfiUnsafe { ty: Ty<'tcx>, reason: DiagMessage, help: Option<DiagMessage> },
-}
-
 pub(crate) fn nonnull_optimization_guaranteed<'tcx>(
     tcx: TyCtxt<'tcx>,
     def: ty::AdtDef<'tcx>,
@@ -855,14 +710,13 @@ fn ty_is_known_nonnull<'tcx>(
     tcx: TyCtxt<'tcx>,
     typing_env: ty::TypingEnv<'tcx>,
     ty: Ty<'tcx>,
-    mode: CItemKind,
 ) -> bool {
     let ty = tcx.try_normalize_erasing_regions(typing_env, ty).unwrap_or(ty);
 
     match ty.kind() {
         ty::FnPtr(..) => true,
         ty::Ref(..) => true,
-        ty::Adt(def, _) if def.is_box() && matches!(mode, CItemKind::Definition) => true,
+        ty::Adt(def, _) if def.is_box() => true,
         ty::Adt(def, args) if def.repr().transparent() && !def.is_union() => {
             let marked_non_null = nonnull_optimization_guaranteed(tcx, *def);
 
@@ -878,10 +732,10 @@ fn ty_is_known_nonnull<'tcx>(
             def.variants()
                 .iter()
                 .filter_map(|variant| transparent_newtype_field(tcx, variant))
-                .any(|field| ty_is_known_nonnull(tcx, typing_env, field.ty(tcx, args), mode))
+                .any(|field| ty_is_known_nonnull(tcx, typing_env, field.ty(tcx, args)))
         }
         ty::Pat(base, pat) => {
-            ty_is_known_nonnull(tcx, typing_env, *base, mode)
+            ty_is_known_nonnull(tcx, typing_env, *base)
                 || pat_ty_is_known_nonnull(tcx, typing_env, *pat)
         }
         _ => false,
@@ -992,7 +846,6 @@ pub(crate) fn repr_nullable_ptr<'tcx>(
     tcx: TyCtxt<'tcx>,
     typing_env: ty::TypingEnv<'tcx>,
     ty: Ty<'tcx>,
-    ckind: CItemKind,
 ) -> Option<Ty<'tcx>> {
     debug!("is_repr_nullable_ptr(tcx, ty = {:?})", ty);
     match ty.kind() {
@@ -1017,7 +870,7 @@ pub(crate) fn repr_nullable_ptr<'tcx>(
                 _ => return None,
             };
 
-            if !ty_is_known_nonnull(tcx, typing_env, field_ty, ckind) {
+            if !ty_is_known_nonnull(tcx, typing_env, field_ty) {
                 return None;
             }
 
@@ -1076,710 +929,6 @@ fn get_nullable_type_from_pat<'tcx>(
     }
 }
 
-impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
-    /// Check if the type is array and emit an unsafe type lint.
-    fn check_for_array_ty(&mut self, sp: Span, ty: Ty<'tcx>) -> bool {
-        if let ty::Array(..) = ty.kind() {
-            self.emit_ffi_unsafe_type_lint(
-                ty,
-                sp,
-                fluent::lint_improper_ctypes_array_reason,
-                Some(fluent::lint_improper_ctypes_array_help),
-            );
-            true
-        } else {
-            false
-        }
-    }
-
-    /// Checks if the given field's type is "ffi-safe".
-    fn check_field_type_for_ffi(
-        &self,
-        acc: &mut CTypesVisitorState<'tcx>,
-        field: &ty::FieldDef,
-        args: GenericArgsRef<'tcx>,
-    ) -> FfiResult<'tcx> {
-        let field_ty = field.ty(self.cx.tcx, args);
-        let field_ty = self
-            .cx
-            .tcx
-            .try_normalize_erasing_regions(self.cx.typing_env(), field_ty)
-            .unwrap_or(field_ty);
-        self.check_type_for_ffi(acc, field_ty)
-    }
-
-    /// Checks if the given `VariantDef`'s field types are "ffi-safe".
-    fn check_variant_for_ffi(
-        &self,
-        acc: &mut CTypesVisitorState<'tcx>,
-        ty: Ty<'tcx>,
-        def: ty::AdtDef<'tcx>,
-        variant: &ty::VariantDef,
-        args: GenericArgsRef<'tcx>,
-    ) -> FfiResult<'tcx> {
-        use FfiResult::*;
-        let transparent_with_all_zst_fields = if def.repr().transparent() {
-            if let Some(field) = transparent_newtype_field(self.cx.tcx, variant) {
-                // Transparent newtypes have at most one non-ZST field which needs to be checked..
-                match self.check_field_type_for_ffi(acc, field, args) {
-                    FfiUnsafe { ty, .. } if ty.is_unit() => (),
-                    r => return r,
-                }
-
-                false
-            } else {
-                // ..or have only ZST fields, which is FFI-unsafe (unless those fields are all
-                // `PhantomData`).
-                true
-            }
-        } else {
-            false
-        };
-
-        // We can't completely trust `repr(C)` markings, so make sure the fields are actually safe.
-        let mut all_phantom = !variant.fields.is_empty();
-        for field in &variant.fields {
-            all_phantom &= match self.check_field_type_for_ffi(acc, field, args) {
-                FfiSafe => false,
-                // `()` fields are FFI-safe!
-                FfiUnsafe { ty, .. } if ty.is_unit() => false,
-                FfiPhantom(..) => true,
-                r @ FfiUnsafe { .. } => return r,
-            }
-        }
-
-        if all_phantom {
-            FfiPhantom(ty)
-        } else if transparent_with_all_zst_fields {
-            FfiUnsafe { ty, reason: fluent::lint_improper_ctypes_struct_zst, help: None }
-        } else {
-            FfiSafe
-        }
-    }
-
-    /// Checks if the given type is "ffi-safe" (has a stable, well-defined
-    /// representation which can be exported to C code).
-    fn check_type_for_ffi(
-        &self,
-        acc: &mut CTypesVisitorState<'tcx>,
-        ty: Ty<'tcx>,
-    ) -> FfiResult<'tcx> {
-        use FfiResult::*;
-
-        let tcx = self.cx.tcx;
-
-        // Protect against infinite recursion, for example
-        // `struct S(*mut S);`.
-        // FIXME: A recursion limit is necessary as well, for irregular
-        // recursive types.
-        if !acc.cache.insert(ty) {
-            return FfiSafe;
-        }
-
-        match *ty.kind() {
-            ty::Adt(def, args) => {
-                if let Some(boxed) = ty.boxed_ty()
-                    && matches!(self.mode, CItemKind::Definition)
-                {
-                    if boxed.is_sized(tcx, self.cx.typing_env()) {
-                        return FfiSafe;
-                    } else {
-                        return FfiUnsafe {
-                            ty,
-                            reason: fluent::lint_improper_ctypes_box,
-                            help: None,
-                        };
-                    }
-                }
-                if def.is_phantom_data() {
-                    return FfiPhantom(ty);
-                }
-                match def.adt_kind() {
-                    AdtKind::Struct | AdtKind::Union => {
-                        if let Some(sym::cstring_type | sym::cstr_type) =
-                            tcx.get_diagnostic_name(def.did())
-                            && !acc.base_ty.is_mutable_ptr()
-                        {
-                            return FfiUnsafe {
-                                ty,
-                                reason: fluent::lint_improper_ctypes_cstr_reason,
-                                help: Some(fluent::lint_improper_ctypes_cstr_help),
-                            };
-                        }
-
-                        if !def.repr().c() && !def.repr().transparent() {
-                            return FfiUnsafe {
-                                ty,
-                                reason: if def.is_struct() {
-                                    fluent::lint_improper_ctypes_struct_layout_reason
-                                } else {
-                                    fluent::lint_improper_ctypes_union_layout_reason
-                                },
-                                help: if def.is_struct() {
-                                    Some(fluent::lint_improper_ctypes_struct_layout_help)
-                                } else {
-                                    Some(fluent::lint_improper_ctypes_union_layout_help)
-                                },
-                            };
-                        }
-
-                        if def.non_enum_variant().field_list_has_applicable_non_exhaustive() {
-                            return FfiUnsafe {
-                                ty,
-                                reason: if def.is_struct() {
-                                    fluent::lint_improper_ctypes_struct_non_exhaustive
-                                } else {
-                                    fluent::lint_improper_ctypes_union_non_exhaustive
-                                },
-                                help: None,
-                            };
-                        }
-
-                        if def.non_enum_variant().fields.is_empty() {
-                            return FfiUnsafe {
-                                ty,
-                                reason: if def.is_struct() {
-                                    fluent::lint_improper_ctypes_struct_fieldless_reason
-                                } else {
-                                    fluent::lint_improper_ctypes_union_fieldless_reason
-                                },
-                                help: if def.is_struct() {
-                                    Some(fluent::lint_improper_ctypes_struct_fieldless_help)
-                                } else {
-                                    Some(fluent::lint_improper_ctypes_union_fieldless_help)
-                                },
-                            };
-                        }
-
-                        self.check_variant_for_ffi(acc, ty, def, def.non_enum_variant(), args)
-                    }
-                    AdtKind::Enum => {
-                        if def.variants().is_empty() {
-                            // Empty enums are okay... although sort of useless.
-                            return FfiSafe;
-                        }
-                        // Check for a repr() attribute to specify the size of the
-                        // discriminant.
-                        if !def.repr().c() && !def.repr().transparent() && def.repr().int.is_none()
-                        {
-                            // Special-case types like `Option<extern fn()>` and `Result<extern fn(), ()>`
-                            if let Some(ty) =
-                                repr_nullable_ptr(self.cx.tcx, self.cx.typing_env(), ty, self.mode)
-                            {
-                                return self.check_type_for_ffi(acc, ty);
-                            }
-
-                            return FfiUnsafe {
-                                ty,
-                                reason: fluent::lint_improper_ctypes_enum_repr_reason,
-                                help: Some(fluent::lint_improper_ctypes_enum_repr_help),
-                            };
-                        }
-
-                        use improper_ctypes::check_non_exhaustive_variant;
-
-                        let non_exhaustive = def.variant_list_has_applicable_non_exhaustive();
-                        // Check the contained variants.
-                        let ret = def.variants().iter().try_for_each(|variant| {
-                            check_non_exhaustive_variant(non_exhaustive, variant)
-                                .map_break(|reason| FfiUnsafe { ty, reason, help: None })?;
-
-                            match self.check_variant_for_ffi(acc, ty, def, variant, args) {
-                                FfiSafe => ControlFlow::Continue(()),
-                                r => ControlFlow::Break(r),
-                            }
-                        });
-                        if let ControlFlow::Break(result) = ret {
-                            return result;
-                        }
-
-                        FfiSafe
-                    }
-                }
-            }
-
-            ty::Char => FfiUnsafe {
-                ty,
-                reason: fluent::lint_improper_ctypes_char_reason,
-                help: Some(fluent::lint_improper_ctypes_char_help),
-            },
-
-            // It's just extra invariants on the type that you need to uphold,
-            // but only the base type is relevant for being representable in FFI.
-            ty::Pat(base, ..) => self.check_type_for_ffi(acc, base),
-
-            // Primitive types with a stable representation.
-            ty::Bool | ty::Int(..) | ty::Uint(..) | ty::Float(..) | ty::Never => FfiSafe,
-
-            ty::Slice(_) => FfiUnsafe {
-                ty,
-                reason: fluent::lint_improper_ctypes_slice_reason,
-                help: Some(fluent::lint_improper_ctypes_slice_help),
-            },
-
-            ty::Dynamic(..) => {
-                FfiUnsafe { ty, reason: fluent::lint_improper_ctypes_dyn, help: None }
-            }
-
-            ty::Str => FfiUnsafe {
-                ty,
-                reason: fluent::lint_improper_ctypes_str_reason,
-                help: Some(fluent::lint_improper_ctypes_str_help),
-            },
-
-            ty::Tuple(..) => FfiUnsafe {
-                ty,
-                reason: fluent::lint_improper_ctypes_tuple_reason,
-                help: Some(fluent::lint_improper_ctypes_tuple_help),
-            },
-
-            ty::RawPtr(ty, _) | ty::Ref(_, ty, _)
-                if {
-                    matches!(self.mode, CItemKind::Definition)
-                        && ty.is_sized(self.cx.tcx, self.cx.typing_env())
-                } =>
-            {
-                FfiSafe
-            }
-
-            ty::RawPtr(ty, _)
-                if match ty.kind() {
-                    ty::Tuple(tuple) => tuple.is_empty(),
-                    _ => false,
-                } =>
-            {
-                FfiSafe
-            }
-
-            ty::RawPtr(ty, _) | ty::Ref(_, ty, _) => self.check_type_for_ffi(acc, ty),
-
-            ty::Array(inner_ty, _) => self.check_type_for_ffi(acc, inner_ty),
-
-            ty::FnPtr(sig_tys, hdr) => {
-                let sig = sig_tys.with(hdr);
-                if sig.abi().is_rustic_abi() {
-                    return FfiUnsafe {
-                        ty,
-                        reason: fluent::lint_improper_ctypes_fnptr_reason,
-                        help: Some(fluent::lint_improper_ctypes_fnptr_help),
-                    };
-                }
-
-                let sig = tcx.instantiate_bound_regions_with_erased(sig);
-                for arg in sig.inputs() {
-                    match self.check_type_for_ffi(acc, *arg) {
-                        FfiSafe => {}
-                        r => return r,
-                    }
-                }
-
-                let ret_ty = sig.output();
-                if ret_ty.is_unit() {
-                    return FfiSafe;
-                }
-
-                self.check_type_for_ffi(acc, ret_ty)
-            }
-
-            ty::Foreign(..) => FfiSafe,
-
-            // While opaque types are checked for earlier, if a projection in a struct field
-            // normalizes to an opaque type, then it will reach this branch.
-            ty::Alias(ty::Opaque, ..) => {
-                FfiUnsafe { ty, reason: fluent::lint_improper_ctypes_opaque, help: None }
-            }
-
-            // `extern "C" fn` functions can have type parameters, which may or may not be FFI-safe,
-            //  so they are currently ignored for the purposes of this lint.
-            ty::Param(..) | ty::Alias(ty::Projection | ty::Inherent, ..)
-                if matches!(self.mode, CItemKind::Definition) =>
-            {
-                FfiSafe
-            }
-
-            ty::UnsafeBinder(_) => todo!("FIXME(unsafe_binder)"),
-
-            ty::Param(..)
-            | ty::Alias(ty::Projection | ty::Inherent | ty::Free, ..)
-            | ty::Infer(..)
-            | ty::Bound(..)
-            | ty::Error(_)
-            | ty::Closure(..)
-            | ty::CoroutineClosure(..)
-            | ty::Coroutine(..)
-            | ty::CoroutineWitness(..)
-            | ty::Placeholder(..)
-            | ty::FnDef(..) => bug!("unexpected type in foreign function: {:?}", ty),
-        }
-    }
-
-    fn emit_ffi_unsafe_type_lint(
-        &mut self,
-        ty: Ty<'tcx>,
-        sp: Span,
-        note: DiagMessage,
-        help: Option<DiagMessage>,
-    ) {
-        let lint = match self.mode {
-            CItemKind::Declaration => IMPROPER_CTYPES,
-            CItemKind::Definition => IMPROPER_CTYPES_DEFINITIONS,
-        };
-        let desc = match self.mode {
-            CItemKind::Declaration => "block",
-            CItemKind::Definition => "fn",
-        };
-        let span_note = if let ty::Adt(def, _) = ty.kind()
-            && let Some(sp) = self.cx.tcx.hir_span_if_local(def.did())
-        {
-            Some(sp)
-        } else {
-            None
-        };
-        self.cx.emit_span_lint(
-            lint,
-            sp,
-            ImproperCTypes { ty, desc, label: sp, help, note, span_note },
-        );
-    }
-
-    fn check_for_opaque_ty(&mut self, sp: Span, ty: Ty<'tcx>) -> bool {
-        struct ProhibitOpaqueTypes;
-        impl<'tcx> ty::TypeVisitor<TyCtxt<'tcx>> for ProhibitOpaqueTypes {
-            type Result = ControlFlow<Ty<'tcx>>;
-
-            fn visit_ty(&mut self, ty: Ty<'tcx>) -> Self::Result {
-                if !ty.has_opaque_types() {
-                    return ControlFlow::Continue(());
-                }
-
-                if let ty::Alias(ty::Opaque, ..) = ty.kind() {
-                    ControlFlow::Break(ty)
-                } else {
-                    ty.super_visit_with(self)
-                }
-            }
-        }
-
-        if let Some(ty) = self
-            .cx
-            .tcx
-            .try_normalize_erasing_regions(self.cx.typing_env(), ty)
-            .unwrap_or(ty)
-            .visit_with(&mut ProhibitOpaqueTypes)
-            .break_value()
-        {
-            self.emit_ffi_unsafe_type_lint(ty, sp, fluent::lint_improper_ctypes_opaque, None);
-            true
-        } else {
-            false
-        }
-    }
-
-    fn check_type_for_ffi_and_report_errors(
-        &mut self,
-        sp: Span,
-        ty: Ty<'tcx>,
-        is_static: bool,
-        is_return_type: bool,
-    ) {
-        if self.check_for_opaque_ty(sp, ty) {
-            // We've already emitted an error due to an opaque type.
-            return;
-        }
-
-        let ty = self.cx.tcx.try_normalize_erasing_regions(self.cx.typing_env(), ty).unwrap_or(ty);
-
-        // C doesn't really support passing arrays by value - the only way to pass an array by value
-        // is through a struct. So, first test that the top level isn't an array, and then
-        // recursively check the types inside.
-        if !is_static && self.check_for_array_ty(sp, ty) {
-            return;
-        }
-
-        // Don't report FFI errors for unit return types. This check exists here, and not in
-        // the caller (where it would make more sense) so that normalization has definitely
-        // happened.
-        if is_return_type && ty.is_unit() {
-            return;
-        }
-
-        let mut acc = CTypesVisitorState { cache: FxHashSet::default(), base_ty: ty };
-        match self.check_type_for_ffi(&mut acc, ty) {
-            FfiResult::FfiSafe => {}
-            FfiResult::FfiPhantom(ty) => {
-                self.emit_ffi_unsafe_type_lint(
-                    ty,
-                    sp,
-                    fluent::lint_improper_ctypes_only_phantomdata,
-                    None,
-                );
-            }
-            FfiResult::FfiUnsafe { ty, reason, help } => {
-                self.emit_ffi_unsafe_type_lint(ty, sp, reason, help);
-            }
-        }
-    }
-
-    /// Check if a function's argument types and result type are "ffi-safe".
-    ///
-    /// For a external ABI function, argument types and the result type are walked to find fn-ptr
-    /// types that have external ABIs, as these still need checked.
-    fn check_fn(&mut self, def_id: LocalDefId, decl: &'tcx hir::FnDecl<'_>) {
-        let sig = self.cx.tcx.fn_sig(def_id).instantiate_identity();
-        let sig = self.cx.tcx.instantiate_bound_regions_with_erased(sig);
-
-        for (input_ty, input_hir) in iter::zip(sig.inputs(), decl.inputs) {
-            for (fn_ptr_ty, span) in self.find_fn_ptr_ty_with_external_abi(input_hir, *input_ty) {
-                self.check_type_for_ffi_and_report_errors(span, fn_ptr_ty, false, false);
-            }
-        }
-
-        if let hir::FnRetTy::Return(ret_hir) = decl.output {
-            for (fn_ptr_ty, span) in self.find_fn_ptr_ty_with_external_abi(ret_hir, sig.output()) {
-                self.check_type_for_ffi_and_report_errors(span, fn_ptr_ty, false, true);
-            }
-        }
-    }
-
-    /// Check if a function's argument types and result type are "ffi-safe".
-    fn check_foreign_fn(&mut self, def_id: LocalDefId, decl: &'tcx hir::FnDecl<'_>) {
-        let sig = self.cx.tcx.fn_sig(def_id).instantiate_identity();
-        let sig = self.cx.tcx.instantiate_bound_regions_with_erased(sig);
-
-        for (input_ty, input_hir) in iter::zip(sig.inputs(), decl.inputs) {
-            self.check_type_for_ffi_and_report_errors(input_hir.span, *input_ty, false, false);
-        }
-
-        if let hir::FnRetTy::Return(ret_hir) = decl.output {
-            self.check_type_for_ffi_and_report_errors(ret_hir.span, sig.output(), false, true);
-        }
-    }
-
-    fn check_foreign_static(&mut self, id: hir::OwnerId, span: Span) {
-        let ty = self.cx.tcx.type_of(id).instantiate_identity();
-        self.check_type_for_ffi_and_report_errors(span, ty, true, false);
-    }
-
-    /// Find any fn-ptr types with external ABIs in `ty`.
-    ///
-    /// For example, `Option<extern "C" fn()>` returns `extern "C" fn()`
-    fn find_fn_ptr_ty_with_external_abi(
-        &self,
-        hir_ty: &hir::Ty<'tcx>,
-        ty: Ty<'tcx>,
-    ) -> Vec<(Ty<'tcx>, Span)> {
-        struct FnPtrFinder<'tcx> {
-            spans: Vec<Span>,
-            tys: Vec<Ty<'tcx>>,
-        }
-
-        impl<'tcx> hir::intravisit::Visitor<'_> for FnPtrFinder<'tcx> {
-            fn visit_ty(&mut self, ty: &'_ hir::Ty<'_, AmbigArg>) {
-                debug!(?ty);
-                if let hir::TyKind::FnPtr(hir::FnPtrTy { abi, .. }) = ty.kind
-                    && !abi.is_rustic_abi()
-                {
-                    self.spans.push(ty.span);
-                }
-
-                hir::intravisit::walk_ty(self, ty)
-            }
-        }
-
-        impl<'tcx> ty::TypeVisitor<TyCtxt<'tcx>> for FnPtrFinder<'tcx> {
-            type Result = ();
-
-            fn visit_ty(&mut self, ty: Ty<'tcx>) -> Self::Result {
-                if let ty::FnPtr(_, hdr) = ty.kind()
-                    && !hdr.abi.is_rustic_abi()
-                {
-                    self.tys.push(ty);
-                }
-
-                ty.super_visit_with(self)
-            }
-        }
-
-        let mut visitor = FnPtrFinder { spans: Vec::new(), tys: Vec::new() };
-        ty.visit_with(&mut visitor);
-        visitor.visit_ty_unambig(hir_ty);
-
-        iter::zip(visitor.tys.drain(..), visitor.spans.drain(..)).collect()
-    }
-}
-
-impl<'tcx> LateLintPass<'tcx> for ImproperCTypesDeclarations {
-    fn check_foreign_item(&mut self, cx: &LateContext<'tcx>, it: &hir::ForeignItem<'tcx>) {
-        let mut vis = ImproperCTypesVisitor { cx, mode: CItemKind::Declaration };
-        let abi = cx.tcx.hir_get_foreign_abi(it.hir_id());
-
-        match it.kind {
-            hir::ForeignItemKind::Fn(sig, _, _) => {
-                if abi.is_rustic_abi() {
-                    vis.check_fn(it.owner_id.def_id, sig.decl)
-                } else {
-                    vis.check_foreign_fn(it.owner_id.def_id, sig.decl);
-                }
-            }
-            hir::ForeignItemKind::Static(ty, _, _) if !abi.is_rustic_abi() => {
-                vis.check_foreign_static(it.owner_id, ty.span);
-            }
-            hir::ForeignItemKind::Static(..) | hir::ForeignItemKind::Type => (),
-        }
-    }
-}
-
-impl ImproperCTypesDefinitions {
-    fn check_ty_maybe_containing_foreign_fnptr<'tcx>(
-        &mut self,
-        cx: &LateContext<'tcx>,
-        hir_ty: &'tcx hir::Ty<'_>,
-        ty: Ty<'tcx>,
-    ) {
-        let mut vis = ImproperCTypesVisitor { cx, mode: CItemKind::Definition };
-        for (fn_ptr_ty, span) in vis.find_fn_ptr_ty_with_external_abi(hir_ty, ty) {
-            vis.check_type_for_ffi_and_report_errors(span, fn_ptr_ty, true, false);
-        }
-    }
-
-    fn check_arg_for_power_alignment<'tcx>(
-        &mut self,
-        cx: &LateContext<'tcx>,
-        ty: Ty<'tcx>,
-    ) -> bool {
-        assert!(cx.tcx.sess.target.os == "aix");
-        // Structs (under repr(C)) follow the power alignment rule if:
-        //   - the first field of the struct is a floating-point type that
-        //     is greater than 4-bytes, or
-        //   - the first field of the struct is an aggregate whose
-        //     recursively first field is a floating-point type greater than
-        //     4 bytes.
-        if ty.is_floating_point() && ty.primitive_size(cx.tcx).bytes() > 4 {
-            return true;
-        } else if let Adt(adt_def, _) = ty.kind()
-            && adt_def.is_struct()
-            && adt_def.repr().c()
-            && !adt_def.repr().packed()
-            && adt_def.repr().align.is_none()
-        {
-            let struct_variant = adt_def.variant(VariantIdx::ZERO);
-            // Within a nested struct, all fields are examined to correctly
-            // report if any fields after the nested struct within the
-            // original struct are misaligned.
-            for struct_field in &struct_variant.fields {
-                let field_ty = cx.tcx.type_of(struct_field.did).instantiate_identity();
-                if self.check_arg_for_power_alignment(cx, field_ty) {
-                    return true;
-                }
-            }
-        }
-        return false;
-    }
-
-    fn check_struct_for_power_alignment<'tcx>(
-        &mut self,
-        cx: &LateContext<'tcx>,
-        item: &'tcx hir::Item<'tcx>,
-    ) {
-        let adt_def = cx.tcx.adt_def(item.owner_id.to_def_id());
-        // repr(C) structs also with packed or aligned representation
-        // should be ignored.
-        if adt_def.repr().c()
-            && !adt_def.repr().packed()
-            && adt_def.repr().align.is_none()
-            && cx.tcx.sess.target.os == "aix"
-            && !adt_def.all_fields().next().is_none()
-        {
-            let struct_variant_data = item.expect_struct().2;
-            for field_def in struct_variant_data.fields().iter().skip(1) {
-                // Struct fields (after the first field) are checked for the
-                // power alignment rule, as fields after the first are likely
-                // to be the fields that are misaligned.
-                let def_id = field_def.def_id;
-                let ty = cx.tcx.type_of(def_id).instantiate_identity();
-                if self.check_arg_for_power_alignment(cx, ty) {
-                    cx.emit_span_lint(USES_POWER_ALIGNMENT, field_def.span, UsesPowerAlignment);
-                }
-            }
-        }
-    }
-}
-
-/// `ImproperCTypesDefinitions` checks items outside of foreign items (e.g. stuff that isn't in
-/// `extern "C" { }` blocks):
-///
-/// - `extern "<abi>" fn` definitions are checked in the same way as the
-///   `ImproperCtypesDeclarations` visitor checks functions if `<abi>` is external (e.g. "C").
-/// - All other items which contain types (e.g. other functions, struct definitions, etc) are
-///   checked for extern fn-ptrs with external ABIs.
-impl<'tcx> LateLintPass<'tcx> for ImproperCTypesDefinitions {
-    fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
-        match item.kind {
-            hir::ItemKind::Static(_, _, ty, _)
-            | hir::ItemKind::Const(_, _, ty, _)
-            | hir::ItemKind::TyAlias(_, _, ty) => {
-                self.check_ty_maybe_containing_foreign_fnptr(
-                    cx,
-                    ty,
-                    cx.tcx.type_of(item.owner_id).instantiate_identity(),
-                );
-            }
-            // See `check_fn`..
-            hir::ItemKind::Fn { .. } => {}
-            // Structs are checked based on if they follow the power alignment
-            // rule (under repr(C)).
-            hir::ItemKind::Struct(..) => {
-                self.check_struct_for_power_alignment(cx, item);
-            }
-            // See `check_field_def`..
-            hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {}
-            // Doesn't define something that can contain a external type to be checked.
-            hir::ItemKind::Impl(..)
-            | hir::ItemKind::TraitAlias(..)
-            | hir::ItemKind::Trait(..)
-            | hir::ItemKind::GlobalAsm { .. }
-            | hir::ItemKind::ForeignMod { .. }
-            | hir::ItemKind::Mod(..)
-            | hir::ItemKind::Macro(..)
-            | hir::ItemKind::Use(..)
-            | hir::ItemKind::ExternCrate(..) => {}
-        }
-    }
-
-    fn check_field_def(&mut self, cx: &LateContext<'tcx>, field: &'tcx hir::FieldDef<'tcx>) {
-        self.check_ty_maybe_containing_foreign_fnptr(
-            cx,
-            field.ty,
-            cx.tcx.type_of(field.def_id).instantiate_identity(),
-        );
-    }
-
-    fn check_fn(
-        &mut self,
-        cx: &LateContext<'tcx>,
-        kind: hir::intravisit::FnKind<'tcx>,
-        decl: &'tcx hir::FnDecl<'_>,
-        _: &'tcx hir::Body<'_>,
-        _: Span,
-        id: LocalDefId,
-    ) {
-        use hir::intravisit::FnKind;
-
-        let abi = match kind {
-            FnKind::ItemFn(_, _, header, ..) => header.abi,
-            FnKind::Method(_, sig, ..) => sig.header.abi,
-            _ => return,
-        };
-
-        let mut vis = ImproperCTypesVisitor { cx, mode: CItemKind::Definition };
-        if abi.is_rustic_abi() {
-            vis.check_fn(id, decl);
-        } else {
-            vis.check_foreign_fn(id, decl);
-        }
-    }
-}
-
 declare_lint_pass!(VariantSizeDifferences => [VARIANT_SIZE_DIFFERENCES]);
 
 impl<'tcx> LateLintPass<'tcx> for VariantSizeDifferences {
diff --git a/compiler/rustc_lint/src/types/improper_ctypes.rs b/compiler/rustc_lint/src/types/improper_ctypes.rs
index 13afa540afc..7ca57b0094e 100644
--- a/compiler/rustc_lint/src/types/improper_ctypes.rs
+++ b/compiler/rustc_lint/src/types/improper_ctypes.rs
@@ -1,10 +1,141 @@
+use std::iter;
 use std::ops::ControlFlow;
 
+use bitflags::bitflags;
+use rustc_abi::VariantIdx;
+use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::DiagMessage;
 use rustc_hir::def::CtorKind;
-use rustc_middle::ty;
+use rustc_hir::intravisit::VisitorExt;
+use rustc_hir::{self as hir, AmbigArg};
+use rustc_middle::bug;
+use rustc_middle::ty::{
+    self, Adt, AdtDef, AdtKind, GenericArgsRef, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable,
+    TypeVisitableExt,
+};
+use rustc_session::{declare_lint, declare_lint_pass};
+use rustc_span::def_id::LocalDefId;
+use rustc_span::{Span, sym};
+use tracing::debug;
 
-use crate::fluent_generated as fluent;
+use super::repr_nullable_ptr;
+use crate::lints::{ImproperCTypes, UsesPowerAlignment};
+use crate::{LateContext, LateLintPass, LintContext, fluent_generated as fluent};
+
+declare_lint! {
+    /// The `improper_ctypes` lint detects incorrect use of types in foreign
+    /// modules.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// unsafe extern "C" {
+    ///     static STATIC: String;
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// The compiler has several checks to verify that types used in `extern`
+    /// blocks are safe and follow certain rules to ensure proper
+    /// compatibility with the foreign interfaces. This lint is issued when it
+    /// detects a probable mistake in a definition. The lint usually should
+    /// provide a description of the issue, along with possibly a hint on how
+    /// to resolve it.
+    IMPROPER_CTYPES,
+    Warn,
+    "proper use of libc types in foreign modules"
+}
+
+declare_lint! {
+    /// The `improper_ctypes_definitions` lint detects incorrect use of
+    /// [`extern` function] definitions.
+    ///
+    /// [`extern` function]: https://doc.rust-lang.org/reference/items/functions.html#extern-function-qualifier
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// # #![allow(unused)]
+    /// pub extern "C" fn str_type(p: &str) { }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// There are many parameter and return types that may be specified in an
+    /// `extern` function that are not compatible with the given ABI. This
+    /// lint is an alert that these types should not be used. The lint usually
+    /// should provide a description of the issue, along with possibly a hint
+    /// on how to resolve it.
+    IMPROPER_CTYPES_DEFINITIONS,
+    Warn,
+    "proper use of libc types in foreign item definitions"
+}
+
+declare_lint! {
+    /// The `uses_power_alignment` lint detects specific `repr(C)`
+    /// aggregates on AIX.
+    /// In its platform C ABI, AIX uses the "power" (as in PowerPC) alignment
+    /// rule (detailed in https://www.ibm.com/docs/en/xl-c-and-cpp-aix/16.1?topic=data-using-alignment-modes#alignment),
+    /// which can also be set for XLC by `#pragma align(power)` or
+    /// `-qalign=power`. Aggregates with a floating-point type as the
+    /// recursively first field (as in "at offset 0") modify the layout of
+    /// *subsequent* fields of the associated structs to use an alignment value
+    /// where the floating-point type is aligned on a 4-byte boundary.
+    ///
+    /// Effectively, subsequent floating-point fields act as-if they are `repr(packed(4))`. This
+    /// would be unsound to do in a `repr(C)` type without all the restrictions that come with
+    /// `repr(packed)`. Rust instead chooses a layout that maintains soundness of Rust code, at the
+    /// expense of incompatibility with C code.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,ignore (fails on non-powerpc64-ibm-aix)
+    /// #[repr(C)]
+    /// pub struct Floats {
+    ///     a: f64,
+    ///     b: u8,
+    ///     c: f64,
+    /// }
+    /// ```
+    ///
+    /// This will produce:
+    ///
+    /// ```text
+    /// warning: repr(C) does not follow the power alignment rule. This may affect platform C ABI compatibility for this type
+    ///  --> <source>:5:3
+    ///   |
+    /// 5 |   c: f64,
+    ///   |   ^^^^^^
+    ///   |
+    ///   = note: `#[warn(uses_power_alignment)]` on by default
+    /// ```
+    ///
+    /// ### Explanation
+    ///
+    /// The power alignment rule specifies that the above struct has the
+    /// following alignment:
+    ///  - offset_of!(Floats, a) == 0
+    ///  - offset_of!(Floats, b) == 8
+    ///  - offset_of!(Floats, c) == 12
+    ///
+    /// However, Rust currently aligns `c` at `offset_of!(Floats, c) == 16`.
+    /// Using offset 12 would be unsound since `f64` generally must be 8-aligned on this target.
+    /// Thus, a warning is produced for the above struct.
+    USES_POWER_ALIGNMENT,
+    Warn,
+    "Structs do not follow the power alignment rule under repr(C)"
+}
+
+declare_lint_pass!(ImproperCTypesLint => [
+    IMPROPER_CTYPES,
+    IMPROPER_CTYPES_DEFINITIONS,
+    USES_POWER_ALIGNMENT
+]);
 
 /// Check a variant of a non-exhaustive enum for improper ctypes
 ///
@@ -41,3 +172,884 @@ fn variant_has_complex_ctor(variant: &ty::VariantDef) -> bool {
     // CtorKind::Const means a "unit" ctor
     !matches!(variant.ctor_kind(), Some(CtorKind::Const))
 }
+
+/// Per-struct-field function that checks if a struct definition follows
+/// the Power alignment Rule (see the `check_struct_for_power_alignment` function).
+fn check_arg_for_power_alignment<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
+    let tcx = cx.tcx;
+    assert!(tcx.sess.target.os == "aix");
+    // Structs (under repr(C)) follow the power alignment rule if:
+    //   - the first field of the struct is a floating-point type that
+    //     is greater than 4-bytes, or
+    //   - the first field of the struct is an aggregate whose
+    //     recursively first field is a floating-point type greater than
+    //     4 bytes.
+    if ty.is_floating_point() && ty.primitive_size(tcx).bytes() > 4 {
+        return true;
+    } else if let Adt(adt_def, _) = ty.kind()
+        && adt_def.is_struct()
+        && adt_def.repr().c()
+        && !adt_def.repr().packed()
+        && adt_def.repr().align.is_none()
+    {
+        let struct_variant = adt_def.variant(VariantIdx::ZERO);
+        // Within a nested struct, all fields are examined to correctly
+        // report if any fields after the nested struct within the
+        // original struct are misaligned.
+        for struct_field in &struct_variant.fields {
+            let field_ty = tcx.type_of(struct_field.did).instantiate_identity();
+            if check_arg_for_power_alignment(cx, field_ty) {
+                return true;
+            }
+        }
+    }
+    return false;
+}
+
+/// Check a struct definition for respect of the Power alignment Rule (as in PowerPC),
+/// which should be respected in the "aix" target OS.
+/// To do so, we must follow one of the two following conditions:
+/// - The first field of the struct must be floating-point type that
+///    is greater than 4-bytes.
+///  - The first field of the struct must be an aggregate whose
+///    recursively first field is a floating-point type greater than
+///    4 bytes.
+fn check_struct_for_power_alignment<'tcx>(
+    cx: &LateContext<'tcx>,
+    item: &'tcx hir::Item<'tcx>,
+    adt_def: AdtDef<'tcx>,
+) {
+    let tcx = cx.tcx;
+    // repr(C) structs also with packed or aligned representation
+    // should be ignored.
+    if adt_def.repr().c()
+        && !adt_def.repr().packed()
+        && adt_def.repr().align.is_none()
+        && tcx.sess.target.os == "aix"
+        && !adt_def.all_fields().next().is_none()
+    {
+        let struct_variant_data = item.expect_struct().2;
+        for field_def in struct_variant_data.fields().iter().skip(1) {
+            // Struct fields (after the first field) are checked for the
+            // power alignment rule, as fields after the first are likely
+            // to be the fields that are misaligned.
+            let def_id = field_def.def_id;
+            let ty = tcx.type_of(def_id).instantiate_identity();
+            if check_arg_for_power_alignment(cx, ty) {
+                cx.emit_span_lint(USES_POWER_ALIGNMENT, field_def.span, UsesPowerAlignment);
+            }
+        }
+    }
+}
+
+#[derive(Clone, Copy)]
+enum CItemKind {
+    Declaration,
+    Definition,
+}
+
+enum FfiResult<'tcx> {
+    FfiSafe,
+    FfiPhantom(Ty<'tcx>),
+    FfiUnsafe { ty: Ty<'tcx>, reason: DiagMessage, help: Option<DiagMessage> },
+}
+
+/// The result when a type has been checked but perhaps not completely. `None` indicates that
+/// FFI safety/unsafety has not yet been determined, `Some(res)` indicates that the safety/unsafety
+/// in the `FfiResult` is final.
+type PartialFfiResult<'tcx> = Option<FfiResult<'tcx>>;
+
+bitflags! {
+    #[derive(Clone, Copy, Debug, PartialEq, Eq)]
+    struct VisitorState: u8 {
+        /// For use in (externally-linked) static variables.
+        const STATIC = 0b000001;
+        /// For use in functions in general.
+        const FUNC = 0b000010;
+        /// For variables in function returns (implicitly: not for static variables).
+        const FN_RETURN = 0b000100;
+        /// For variables in functions/variables which are defined in rust.
+        const DEFINED = 0b001000;
+        /// For times where we are only defining the type of something
+        /// (struct/enum/union definitions, FnPtrs).
+        const THEORETICAL = 0b010000;
+    }
+}
+
+impl VisitorState {
+    // The values that can be set.
+    const STATIC_TY: Self = Self::STATIC;
+    const ARGUMENT_TY_IN_DEFINITION: Self =
+        Self::from_bits(Self::FUNC.bits() | Self::DEFINED.bits()).unwrap();
+    const RETURN_TY_IN_DEFINITION: Self =
+        Self::from_bits(Self::FUNC.bits() | Self::FN_RETURN.bits() | Self::DEFINED.bits()).unwrap();
+    const ARGUMENT_TY_IN_DECLARATION: Self = Self::FUNC;
+    const RETURN_TY_IN_DECLARATION: Self =
+        Self::from_bits(Self::FUNC.bits() | Self::FN_RETURN.bits()).unwrap();
+    const ARGUMENT_TY_IN_FNPTR: Self =
+        Self::from_bits(Self::FUNC.bits() | Self::THEORETICAL.bits()).unwrap();
+    const RETURN_TY_IN_FNPTR: Self =
+        Self::from_bits(Self::FUNC.bits() | Self::THEORETICAL.bits() | Self::FN_RETURN.bits())
+            .unwrap();
+
+    /// Get the proper visitor state for a given function's arguments.
+    fn argument_from_fnmode(fn_mode: CItemKind) -> Self {
+        match fn_mode {
+            CItemKind::Definition => VisitorState::ARGUMENT_TY_IN_DEFINITION,
+            CItemKind::Declaration => VisitorState::ARGUMENT_TY_IN_DECLARATION,
+        }
+    }
+
+    /// Get the proper visitor state for a given function's return type.
+    fn return_from_fnmode(fn_mode: CItemKind) -> Self {
+        match fn_mode {
+            CItemKind::Definition => VisitorState::RETURN_TY_IN_DEFINITION,
+            CItemKind::Declaration => VisitorState::RETURN_TY_IN_DECLARATION,
+        }
+    }
+
+    /// Whether the type is used in a function.
+    fn is_in_function(self) -> bool {
+        let ret = self.contains(Self::FUNC);
+        if ret {
+            debug_assert!(!self.contains(Self::STATIC));
+        }
+        ret
+    }
+    /// Whether the type is used (directly or not) in a function, in return position.
+    fn is_in_function_return(self) -> bool {
+        let ret = self.contains(Self::FN_RETURN);
+        if ret {
+            debug_assert!(self.is_in_function());
+        }
+        ret
+    }
+    /// Whether the type is used (directly or not) in a defined function.
+    /// In other words, whether or not we allow non-FFI-safe types behind a C pointer,
+    /// to be treated as an opaque type on the other side of the FFI boundary.
+    fn is_in_defined_function(self) -> bool {
+        self.contains(Self::DEFINED) && self.is_in_function()
+    }
+
+    /// Whether the type is used (directly or not) in a function pointer type.
+    /// Here, we also allow non-FFI-safe types behind a C pointer,
+    /// to be treated as an opaque type on the other side of the FFI boundary.
+    fn is_in_fnptr(self) -> bool {
+        self.contains(Self::THEORETICAL) && self.is_in_function()
+    }
+
+    /// Whether we can expect type parameters and co in a given type.
+    fn can_expect_ty_params(self) -> bool {
+        // rust-defined functions, as well as FnPtrs
+        self.contains(Self::THEORETICAL) || self.is_in_defined_function()
+    }
+}
+
+/// Visitor used to recursively traverse MIR types and evaluate FFI-safety.
+/// It uses ``check_*`` methods as entrypoints to be called elsewhere,
+/// and ``visit_*`` methods to recurse.
+struct ImproperCTypesVisitor<'a, 'tcx> {
+    cx: &'a LateContext<'tcx>,
+    /// To prevent problems with recursive types,
+    /// add a types-in-check cache.
+    cache: FxHashSet<Ty<'tcx>>,
+    /// The original type being checked, before we recursed
+    /// to any other types it contains.
+    base_ty: Ty<'tcx>,
+    base_fn_mode: CItemKind,
+}
+
+impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
+    fn new(cx: &'a LateContext<'tcx>, base_ty: Ty<'tcx>, base_fn_mode: CItemKind) -> Self {
+        Self { cx, base_ty, base_fn_mode, cache: FxHashSet::default() }
+    }
+
+    /// Checks if the given field's type is "ffi-safe".
+    fn check_field_type_for_ffi(
+        &mut self,
+        state: VisitorState,
+        field: &ty::FieldDef,
+        args: GenericArgsRef<'tcx>,
+    ) -> FfiResult<'tcx> {
+        let field_ty = field.ty(self.cx.tcx, args);
+        let field_ty = self
+            .cx
+            .tcx
+            .try_normalize_erasing_regions(self.cx.typing_env(), field_ty)
+            .unwrap_or(field_ty);
+        self.visit_type(state, field_ty)
+    }
+
+    /// Checks if the given `VariantDef`'s field types are "ffi-safe".
+    fn check_variant_for_ffi(
+        &mut self,
+        state: VisitorState,
+        ty: Ty<'tcx>,
+        def: ty::AdtDef<'tcx>,
+        variant: &ty::VariantDef,
+        args: GenericArgsRef<'tcx>,
+    ) -> FfiResult<'tcx> {
+        use FfiResult::*;
+        let transparent_with_all_zst_fields = if def.repr().transparent() {
+            if let Some(field) = super::transparent_newtype_field(self.cx.tcx, variant) {
+                // Transparent newtypes have at most one non-ZST field which needs to be checked..
+                match self.check_field_type_for_ffi(state, field, args) {
+                    FfiUnsafe { ty, .. } if ty.is_unit() => (),
+                    r => return r,
+                }
+
+                false
+            } else {
+                // ..or have only ZST fields, which is FFI-unsafe (unless those fields are all
+                // `PhantomData`).
+                true
+            }
+        } else {
+            false
+        };
+
+        // We can't completely trust `repr(C)` markings, so make sure the fields are actually safe.
+        let mut all_phantom = !variant.fields.is_empty();
+        for field in &variant.fields {
+            all_phantom &= match self.check_field_type_for_ffi(state, field, args) {
+                FfiSafe => false,
+                // `()` fields are FFI-safe!
+                FfiUnsafe { ty, .. } if ty.is_unit() => false,
+                FfiPhantom(..) => true,
+                r @ FfiUnsafe { .. } => return r,
+            }
+        }
+
+        if all_phantom {
+            FfiPhantom(ty)
+        } else if transparent_with_all_zst_fields {
+            FfiUnsafe { ty, reason: fluent::lint_improper_ctypes_struct_zst, help: None }
+        } else {
+            FfiSafe
+        }
+    }
+
+    /// Checks if the given type is "ffi-safe" (has a stable, well-defined
+    /// representation which can be exported to C code).
+    fn visit_type(&mut self, state: VisitorState, ty: Ty<'tcx>) -> FfiResult<'tcx> {
+        use FfiResult::*;
+
+        let tcx = self.cx.tcx;
+
+        // Protect against infinite recursion, for example
+        // `struct S(*mut S);`.
+        // FIXME: A recursion limit is necessary as well, for irregular
+        // recursive types.
+        if !self.cache.insert(ty) {
+            return FfiSafe;
+        }
+
+        match *ty.kind() {
+            ty::Adt(def, args) => {
+                if let Some(boxed) = ty.boxed_ty()
+                    && (
+                        // FIXME(ctypes): this logic is broken, but it still fits the current tests
+                        state.is_in_defined_function()
+                            || (state.is_in_fnptr()
+                                && matches!(self.base_fn_mode, CItemKind::Definition))
+                    )
+                {
+                    if boxed.is_sized(tcx, self.cx.typing_env()) {
+                        return FfiSafe;
+                    } else {
+                        return FfiUnsafe {
+                            ty,
+                            reason: fluent::lint_improper_ctypes_box,
+                            help: None,
+                        };
+                    }
+                }
+                if def.is_phantom_data() {
+                    return FfiPhantom(ty);
+                }
+                match def.adt_kind() {
+                    AdtKind::Struct | AdtKind::Union => {
+                        if let Some(sym::cstring_type | sym::cstr_type) =
+                            tcx.get_diagnostic_name(def.did())
+                            && !self.base_ty.is_mutable_ptr()
+                        {
+                            return FfiUnsafe {
+                                ty,
+                                reason: fluent::lint_improper_ctypes_cstr_reason,
+                                help: Some(fluent::lint_improper_ctypes_cstr_help),
+                            };
+                        }
+
+                        if !def.repr().c() && !def.repr().transparent() {
+                            return FfiUnsafe {
+                                ty,
+                                reason: if def.is_struct() {
+                                    fluent::lint_improper_ctypes_struct_layout_reason
+                                } else {
+                                    fluent::lint_improper_ctypes_union_layout_reason
+                                },
+                                help: if def.is_struct() {
+                                    Some(fluent::lint_improper_ctypes_struct_layout_help)
+                                } else {
+                                    Some(fluent::lint_improper_ctypes_union_layout_help)
+                                },
+                            };
+                        }
+
+                        if def.non_enum_variant().field_list_has_applicable_non_exhaustive() {
+                            return FfiUnsafe {
+                                ty,
+                                reason: if def.is_struct() {
+                                    fluent::lint_improper_ctypes_struct_non_exhaustive
+                                } else {
+                                    fluent::lint_improper_ctypes_union_non_exhaustive
+                                },
+                                help: None,
+                            };
+                        }
+
+                        if def.non_enum_variant().fields.is_empty() {
+                            return FfiUnsafe {
+                                ty,
+                                reason: if def.is_struct() {
+                                    fluent::lint_improper_ctypes_struct_fieldless_reason
+                                } else {
+                                    fluent::lint_improper_ctypes_union_fieldless_reason
+                                },
+                                help: if def.is_struct() {
+                                    Some(fluent::lint_improper_ctypes_struct_fieldless_help)
+                                } else {
+                                    Some(fluent::lint_improper_ctypes_union_fieldless_help)
+                                },
+                            };
+                        }
+
+                        self.check_variant_for_ffi(state, ty, def, def.non_enum_variant(), args)
+                    }
+                    AdtKind::Enum => {
+                        if def.variants().is_empty() {
+                            // Empty enums are okay... although sort of useless.
+                            return FfiSafe;
+                        }
+                        // Check for a repr() attribute to specify the size of the
+                        // discriminant.
+                        if !def.repr().c() && !def.repr().transparent() && def.repr().int.is_none()
+                        {
+                            // Special-case types like `Option<extern fn()>` and `Result<extern fn(), ()>`
+                            if let Some(ty) =
+                                repr_nullable_ptr(self.cx.tcx, self.cx.typing_env(), ty)
+                            {
+                                return self.visit_type(state, ty);
+                            }
+
+                            return FfiUnsafe {
+                                ty,
+                                reason: fluent::lint_improper_ctypes_enum_repr_reason,
+                                help: Some(fluent::lint_improper_ctypes_enum_repr_help),
+                            };
+                        }
+
+                        let non_exhaustive = def.variant_list_has_applicable_non_exhaustive();
+                        // Check the contained variants.
+                        let ret = def.variants().iter().try_for_each(|variant| {
+                            check_non_exhaustive_variant(non_exhaustive, variant)
+                                .map_break(|reason| FfiUnsafe { ty, reason, help: None })?;
+
+                            match self.check_variant_for_ffi(state, ty, def, variant, args) {
+                                FfiSafe => ControlFlow::Continue(()),
+                                r => ControlFlow::Break(r),
+                            }
+                        });
+                        if let ControlFlow::Break(result) = ret {
+                            return result;
+                        }
+
+                        FfiSafe
+                    }
+                }
+            }
+
+            ty::Char => FfiUnsafe {
+                ty,
+                reason: fluent::lint_improper_ctypes_char_reason,
+                help: Some(fluent::lint_improper_ctypes_char_help),
+            },
+
+            // It's just extra invariants on the type that you need to uphold,
+            // but only the base type is relevant for being representable in FFI.
+            ty::Pat(base, ..) => self.visit_type(state, base),
+
+            // Primitive types with a stable representation.
+            ty::Bool | ty::Int(..) | ty::Uint(..) | ty::Float(..) | ty::Never => FfiSafe,
+
+            ty::Slice(_) => FfiUnsafe {
+                ty,
+                reason: fluent::lint_improper_ctypes_slice_reason,
+                help: Some(fluent::lint_improper_ctypes_slice_help),
+            },
+
+            ty::Dynamic(..) => {
+                FfiUnsafe { ty, reason: fluent::lint_improper_ctypes_dyn, help: None }
+            }
+
+            ty::Str => FfiUnsafe {
+                ty,
+                reason: fluent::lint_improper_ctypes_str_reason,
+                help: Some(fluent::lint_improper_ctypes_str_help),
+            },
+
+            ty::Tuple(..) => FfiUnsafe {
+                ty,
+                reason: fluent::lint_improper_ctypes_tuple_reason,
+                help: Some(fluent::lint_improper_ctypes_tuple_help),
+            },
+
+            ty::RawPtr(ty, _) | ty::Ref(_, ty, _)
+                if {
+                    (state.is_in_defined_function() || state.is_in_fnptr())
+                        && ty.is_sized(self.cx.tcx, self.cx.typing_env())
+                } =>
+            {
+                FfiSafe
+            }
+
+            ty::RawPtr(ty, _)
+                if match ty.kind() {
+                    ty::Tuple(tuple) => tuple.is_empty(),
+                    _ => false,
+                } =>
+            {
+                FfiSafe
+            }
+
+            ty::RawPtr(ty, _) | ty::Ref(_, ty, _) => self.visit_type(state, ty),
+
+            ty::Array(inner_ty, _) => self.visit_type(state, inner_ty),
+
+            ty::FnPtr(sig_tys, hdr) => {
+                let sig = sig_tys.with(hdr);
+                if sig.abi().is_rustic_abi() {
+                    return FfiUnsafe {
+                        ty,
+                        reason: fluent::lint_improper_ctypes_fnptr_reason,
+                        help: Some(fluent::lint_improper_ctypes_fnptr_help),
+                    };
+                }
+
+                let sig = tcx.instantiate_bound_regions_with_erased(sig);
+                for arg in sig.inputs() {
+                    match self.visit_type(VisitorState::ARGUMENT_TY_IN_FNPTR, *arg) {
+                        FfiSafe => {}
+                        r => return r,
+                    }
+                }
+
+                let ret_ty = sig.output();
+                if ret_ty.is_unit() {
+                    return FfiSafe;
+                }
+
+                self.visit_type(VisitorState::RETURN_TY_IN_FNPTR, ret_ty)
+            }
+
+            ty::Foreign(..) => FfiSafe,
+
+            // While opaque types are checked for earlier, if a projection in a struct field
+            // normalizes to an opaque type, then it will reach this branch.
+            ty::Alias(ty::Opaque, ..) => {
+                FfiUnsafe { ty, reason: fluent::lint_improper_ctypes_opaque, help: None }
+            }
+
+            // `extern "C" fn` functions can have type parameters, which may or may not be FFI-safe,
+            //  so they are currently ignored for the purposes of this lint.
+            ty::Param(..) | ty::Alias(ty::Projection | ty::Inherent, ..)
+                if state.can_expect_ty_params() =>
+            {
+                FfiSafe
+            }
+
+            ty::UnsafeBinder(_) => todo!("FIXME(unsafe_binder)"),
+
+            ty::Param(..)
+            | ty::Alias(ty::Projection | ty::Inherent | ty::Free, ..)
+            | ty::Infer(..)
+            | ty::Bound(..)
+            | ty::Error(_)
+            | ty::Closure(..)
+            | ty::CoroutineClosure(..)
+            | ty::Coroutine(..)
+            | ty::CoroutineWitness(..)
+            | ty::Placeholder(..)
+            | ty::FnDef(..) => bug!("unexpected type in foreign function: {:?}", ty),
+        }
+    }
+
+    fn visit_for_opaque_ty(&mut self, ty: Ty<'tcx>) -> PartialFfiResult<'tcx> {
+        struct ProhibitOpaqueTypes;
+        impl<'tcx> ty::TypeVisitor<TyCtxt<'tcx>> for ProhibitOpaqueTypes {
+            type Result = ControlFlow<Ty<'tcx>>;
+
+            fn visit_ty(&mut self, ty: Ty<'tcx>) -> Self::Result {
+                if !ty.has_opaque_types() {
+                    return ControlFlow::Continue(());
+                }
+
+                if let ty::Alias(ty::Opaque, ..) = ty.kind() {
+                    ControlFlow::Break(ty)
+                } else {
+                    ty.super_visit_with(self)
+                }
+            }
+        }
+
+        if let Some(ty) = self
+            .cx
+            .tcx
+            .try_normalize_erasing_regions(self.cx.typing_env(), ty)
+            .unwrap_or(ty)
+            .visit_with(&mut ProhibitOpaqueTypes)
+            .break_value()
+        {
+            Some(FfiResult::FfiUnsafe {
+                ty,
+                reason: fluent::lint_improper_ctypes_opaque,
+                help: None,
+            })
+        } else {
+            None
+        }
+    }
+
+    /// Check if the type is array and emit an unsafe type lint.
+    fn check_for_array_ty(&mut self, ty: Ty<'tcx>) -> PartialFfiResult<'tcx> {
+        if let ty::Array(..) = ty.kind() {
+            Some(FfiResult::FfiUnsafe {
+                ty,
+                reason: fluent::lint_improper_ctypes_array_reason,
+                help: Some(fluent::lint_improper_ctypes_array_help),
+            })
+        } else {
+            None
+        }
+    }
+
+    /// Determine the FFI-safety of a single (MIR) type, given the context of how it is used.
+    fn check_type(&mut self, state: VisitorState, ty: Ty<'tcx>) -> FfiResult<'tcx> {
+        if let Some(res) = self.visit_for_opaque_ty(ty) {
+            return res;
+        }
+
+        let ty = self.cx.tcx.try_normalize_erasing_regions(self.cx.typing_env(), ty).unwrap_or(ty);
+
+        // C doesn't really support passing arrays by value - the only way to pass an array by value
+        // is through a struct. So, first test that the top level isn't an array, and then
+        // recursively check the types inside.
+        if state.is_in_function() {
+            if let Some(res) = self.check_for_array_ty(ty) {
+                return res;
+            }
+        }
+
+        // Don't report FFI errors for unit return types. This check exists here, and not in
+        // the caller (where it would make more sense) so that normalization has definitely
+        // happened.
+        if state.is_in_function_return() && ty.is_unit() {
+            return FfiResult::FfiSafe;
+        }
+
+        self.visit_type(state, ty)
+    }
+}
+
+impl<'tcx> ImproperCTypesLint {
+    /// Find any fn-ptr types with external ABIs in `ty`, and FFI-checks them.
+    /// For example, `Option<extern "C" fn()>` FFI-checks `extern "C" fn()`.
+    fn check_type_for_external_abi_fnptr(
+        &mut self,
+        cx: &LateContext<'tcx>,
+        state: VisitorState,
+        hir_ty: &hir::Ty<'tcx>,
+        ty: Ty<'tcx>,
+        fn_mode: CItemKind,
+    ) {
+        struct FnPtrFinder<'tcx> {
+            spans: Vec<Span>,
+            tys: Vec<Ty<'tcx>>,
+        }
+
+        impl<'tcx> hir::intravisit::Visitor<'_> for FnPtrFinder<'tcx> {
+            fn visit_ty(&mut self, ty: &'_ hir::Ty<'_, AmbigArg>) {
+                debug!(?ty);
+                if let hir::TyKind::FnPtr(hir::FnPtrTy { abi, .. }) = ty.kind
+                    && !abi.is_rustic_abi()
+                {
+                    self.spans.push(ty.span);
+                }
+
+                hir::intravisit::walk_ty(self, ty)
+            }
+        }
+
+        impl<'tcx> ty::TypeVisitor<TyCtxt<'tcx>> for FnPtrFinder<'tcx> {
+            type Result = ();
+
+            fn visit_ty(&mut self, ty: Ty<'tcx>) -> Self::Result {
+                if let ty::FnPtr(_, hdr) = ty.kind()
+                    && !hdr.abi.is_rustic_abi()
+                {
+                    self.tys.push(ty);
+                }
+
+                ty.super_visit_with(self)
+            }
+        }
+
+        let mut visitor = FnPtrFinder { spans: Vec::new(), tys: Vec::new() };
+        ty.visit_with(&mut visitor);
+        visitor.visit_ty_unambig(hir_ty);
+
+        let all_types = iter::zip(visitor.tys.drain(..), visitor.spans.drain(..));
+        for (fn_ptr_ty, span) in all_types {
+            let mut visitor = ImproperCTypesVisitor::new(cx, fn_ptr_ty, fn_mode);
+            // FIXME(ctypes): make a check_for_fnptr
+            let ffi_res = visitor.check_type(state, fn_ptr_ty);
+
+            self.process_ffi_result(cx, span, ffi_res, fn_mode);
+        }
+    }
+
+    /// Regardless of a function's need to be "ffi-safe", look for fn-ptr argument/return types
+    /// that need to be checked for ffi-safety.
+    fn check_fn_for_external_abi_fnptr(
+        &mut self,
+        cx: &LateContext<'tcx>,
+        fn_mode: CItemKind,
+        def_id: LocalDefId,
+        decl: &'tcx hir::FnDecl<'_>,
+    ) {
+        let sig = cx.tcx.fn_sig(def_id).instantiate_identity();
+        let sig = cx.tcx.instantiate_bound_regions_with_erased(sig);
+
+        for (input_ty, input_hir) in iter::zip(sig.inputs(), decl.inputs) {
+            let state = VisitorState::argument_from_fnmode(fn_mode);
+            self.check_type_for_external_abi_fnptr(cx, state, input_hir, *input_ty, fn_mode);
+        }
+
+        if let hir::FnRetTy::Return(ret_hir) = decl.output {
+            let state = VisitorState::return_from_fnmode(fn_mode);
+            self.check_type_for_external_abi_fnptr(cx, state, ret_hir, sig.output(), fn_mode);
+        }
+    }
+
+    /// For a local definition of a #[repr(C)] struct/enum/union, check that it is indeed FFI-safe.
+    fn check_reprc_adt(
+        &mut self,
+        cx: &LateContext<'tcx>,
+        item: &'tcx hir::Item<'tcx>,
+        adt_def: AdtDef<'tcx>,
+    ) {
+        debug_assert!(
+            adt_def.repr().c() && !adt_def.repr().packed() && adt_def.repr().align.is_none()
+        );
+
+        // FIXME(ctypes): this following call is awkward.
+        // is there a way to perform its logic in MIR space rather than HIR space?
+        // (so that its logic can be absorbed into visitor.visit_struct_or_union)
+        check_struct_for_power_alignment(cx, item, adt_def);
+    }
+
+    fn check_foreign_static(&mut self, cx: &LateContext<'tcx>, id: hir::OwnerId, span: Span) {
+        let ty = cx.tcx.type_of(id).instantiate_identity();
+        let mut visitor = ImproperCTypesVisitor::new(cx, ty, CItemKind::Declaration);
+        let ffi_res = visitor.check_type(VisitorState::STATIC_TY, ty);
+        self.process_ffi_result(cx, span, ffi_res, CItemKind::Declaration);
+    }
+
+    /// Check if a function's argument types and result type are "ffi-safe".
+    fn check_foreign_fn(
+        &mut self,
+        cx: &LateContext<'tcx>,
+        fn_mode: CItemKind,
+        def_id: LocalDefId,
+        decl: &'tcx hir::FnDecl<'_>,
+    ) {
+        let sig = cx.tcx.fn_sig(def_id).instantiate_identity();
+        let sig = cx.tcx.instantiate_bound_regions_with_erased(sig);
+
+        for (input_ty, input_hir) in iter::zip(sig.inputs(), decl.inputs) {
+            let state = VisitorState::argument_from_fnmode(fn_mode);
+            let mut visitor = ImproperCTypesVisitor::new(cx, *input_ty, fn_mode);
+            let ffi_res = visitor.check_type(state, *input_ty);
+            self.process_ffi_result(cx, input_hir.span, ffi_res, fn_mode);
+        }
+
+        if let hir::FnRetTy::Return(ret_hir) = decl.output {
+            let state = VisitorState::return_from_fnmode(fn_mode);
+            let mut visitor = ImproperCTypesVisitor::new(cx, sig.output(), fn_mode);
+            let ffi_res = visitor.check_type(state, sig.output());
+            self.process_ffi_result(cx, ret_hir.span, ffi_res, fn_mode);
+        }
+    }
+
+    fn process_ffi_result(
+        &self,
+        cx: &LateContext<'tcx>,
+        sp: Span,
+        res: FfiResult<'tcx>,
+        fn_mode: CItemKind,
+    ) {
+        match res {
+            FfiResult::FfiSafe => {}
+            FfiResult::FfiPhantom(ty) => {
+                self.emit_ffi_unsafe_type_lint(
+                    cx,
+                    ty,
+                    sp,
+                    fluent::lint_improper_ctypes_only_phantomdata,
+                    None,
+                    fn_mode,
+                );
+            }
+            FfiResult::FfiUnsafe { ty, reason, help } => {
+                self.emit_ffi_unsafe_type_lint(cx, ty, sp, reason, help, fn_mode);
+            }
+        }
+    }
+
+    fn emit_ffi_unsafe_type_lint(
+        &self,
+        cx: &LateContext<'tcx>,
+        ty: Ty<'tcx>,
+        sp: Span,
+        note: DiagMessage,
+        help: Option<DiagMessage>,
+        fn_mode: CItemKind,
+    ) {
+        let lint = match fn_mode {
+            CItemKind::Declaration => IMPROPER_CTYPES,
+            CItemKind::Definition => IMPROPER_CTYPES_DEFINITIONS,
+        };
+        let desc = match fn_mode {
+            CItemKind::Declaration => "block",
+            CItemKind::Definition => "fn",
+        };
+        let span_note = if let ty::Adt(def, _) = ty.kind()
+            && let Some(sp) = cx.tcx.hir_span_if_local(def.did())
+        {
+            Some(sp)
+        } else {
+            None
+        };
+        cx.emit_span_lint(lint, sp, ImproperCTypes { ty, desc, label: sp, help, note, span_note });
+    }
+}
+
+/// `ImproperCTypesDefinitions` checks items outside of foreign items (e.g. stuff that isn't in
+/// `extern "C" { }` blocks):
+///
+/// - `extern "<abi>" fn` definitions are checked in the same way as the
+///   `ImproperCtypesDeclarations` visitor checks functions if `<abi>` is external (e.g. "C").
+/// - All other items which contain types (e.g. other functions, struct definitions, etc) are
+///   checked for extern fn-ptrs with external ABIs.
+impl<'tcx> LateLintPass<'tcx> for ImproperCTypesLint {
+    fn check_foreign_item(&mut self, cx: &LateContext<'tcx>, it: &hir::ForeignItem<'tcx>) {
+        let abi = cx.tcx.hir_get_foreign_abi(it.hir_id());
+
+        match it.kind {
+            hir::ForeignItemKind::Fn(sig, _, _) => {
+                // fnptrs are a special case, they always need to be treated as
+                // "the element rendered unsafe" because their unsafety doesn't affect
+                // their surroundings, and their type is often declared inline
+                if !abi.is_rustic_abi() {
+                    self.check_foreign_fn(cx, CItemKind::Declaration, it.owner_id.def_id, sig.decl);
+                } else {
+                    self.check_fn_for_external_abi_fnptr(
+                        cx,
+                        CItemKind::Declaration,
+                        it.owner_id.def_id,
+                        sig.decl,
+                    );
+                }
+            }
+            hir::ForeignItemKind::Static(ty, _, _) if !abi.is_rustic_abi() => {
+                self.check_foreign_static(cx, it.owner_id, ty.span);
+            }
+            hir::ForeignItemKind::Static(..) | hir::ForeignItemKind::Type => (),
+        }
+    }
+
+    fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
+        match item.kind {
+            hir::ItemKind::Static(_, _, ty, _)
+            | hir::ItemKind::Const(_, _, ty, _)
+            | hir::ItemKind::TyAlias(_, _, ty) => {
+                self.check_type_for_external_abi_fnptr(
+                    cx,
+                    VisitorState::STATIC_TY,
+                    ty,
+                    cx.tcx.type_of(item.owner_id).instantiate_identity(),
+                    CItemKind::Definition,
+                );
+            }
+            // See `check_fn` for declarations, `check_foreign_items` for definitions in extern blocks
+            hir::ItemKind::Fn { .. } => {}
+            hir::ItemKind::Struct(..) | hir::ItemKind::Union(..) | hir::ItemKind::Enum(..) => {
+                // looking for extern FnPtr:s is delegated to `check_field_def`.
+                let adt_def: AdtDef<'tcx> = cx.tcx.adt_def(item.owner_id.to_def_id());
+
+                if adt_def.repr().c() && !adt_def.repr().packed() && adt_def.repr().align.is_none()
+                {
+                    self.check_reprc_adt(cx, item, adt_def);
+                }
+            }
+
+            // Doesn't define something that can contain a external type to be checked.
+            hir::ItemKind::Impl(..)
+            | hir::ItemKind::TraitAlias(..)
+            | hir::ItemKind::Trait(..)
+            | hir::ItemKind::GlobalAsm { .. }
+            | hir::ItemKind::ForeignMod { .. }
+            | hir::ItemKind::Mod(..)
+            | hir::ItemKind::Macro(..)
+            | hir::ItemKind::Use(..)
+            | hir::ItemKind::ExternCrate(..) => {}
+        }
+    }
+
+    fn check_field_def(&mut self, cx: &LateContext<'tcx>, field: &'tcx hir::FieldDef<'tcx>) {
+        self.check_type_for_external_abi_fnptr(
+            cx,
+            VisitorState::STATIC_TY,
+            field.ty,
+            cx.tcx.type_of(field.def_id).instantiate_identity(),
+            CItemKind::Definition,
+        );
+    }
+
+    fn check_fn(
+        &mut self,
+        cx: &LateContext<'tcx>,
+        kind: hir::intravisit::FnKind<'tcx>,
+        decl: &'tcx hir::FnDecl<'_>,
+        _: &'tcx hir::Body<'_>,
+        _: Span,
+        id: LocalDefId,
+    ) {
+        use hir::intravisit::FnKind;
+
+        let abi = match kind {
+            FnKind::ItemFn(_, _, header, ..) => header.abi,
+            FnKind::Method(_, sig, ..) => sig.header.abi,
+            _ => return,
+        };
+
+        // fnptrs are a special case, they always need to be treated as
+        // "the element rendered unsafe" because their unsafety doesn't affect
+        // their surroundings, and their type is often declared inline
+        if !abi.is_rustic_abi() {
+            self.check_foreign_fn(cx, CItemKind::Definition, id, decl);
+        } else {
+            self.check_fn_for_external_abi_fnptr(cx, CItemKind::Definition, id, decl);
+        }
+    }
+}
diff --git a/compiler/rustc_lint_defs/src/builtin.rs b/compiler/rustc_lint_defs/src/builtin.rs
index ce92263babd..b79075ac09b 100644
--- a/compiler/rustc_lint_defs/src/builtin.rs
+++ b/compiler/rustc_lint_defs/src/builtin.rs
@@ -5141,3 +5141,57 @@ declare_lint! {
     "detects tail calls of functions marked with `#[track_caller]`",
     @feature_gate = explicit_tail_calls;
 }
+declare_lint! {
+    /// The `inline_always_mismatching_target_features` lint will trigger when a
+    /// function with the `#[inline(always)]` and `#[target_feature(enable = "...")]`
+    /// attributes is called and cannot be inlined due to missing target features in the caller.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,ignore (fails on x86_64)
+    /// #[inline(always)]
+    /// #[target_feature(enable = "fp16")]
+    /// unsafe fn callee() {
+    ///     // operations using fp16 types
+    /// }
+    ///
+    /// // Caller does not enable the required target feature
+    /// fn caller() {
+    ///     unsafe { callee(); }
+    /// }
+    ///
+    /// fn main() {
+    ///     caller();
+    /// }
+    /// ```
+    ///
+    /// This will produce:
+    ///
+    /// ```text
+    /// warning: call to `#[inline(always)]`-annotated `callee` requires the same target features. Function will not have `alwaysinline` attribute applied
+    ///   --> $DIR/builtin.rs:5192:14
+    ///    |
+    /// 10 |     unsafe { callee(); }
+    ///    |              ^^^^^^^^
+    ///    |
+    /// note: `fp16` target feature enabled in `callee` here but missing from `caller`
+    ///   --> $DIR/builtin.rs:5185:1
+    ///    |
+    /// 3  | #[target_feature(enable = "fp16")]
+    ///    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    /// 4  | unsafe fn callee() {
+    ///    | ------------------
+    ///    = note: `#[warn(inline_always_mismatching_target_features)]` on by default
+    /// warning: 1 warning emitted
+    /// ```
+    ///
+    /// ### Explanation
+    ///
+    /// Inlining a function with a target feature attribute into a caller that
+    /// lacks the corresponding target feature can lead to unsound behavior.
+    /// LLVM may select the wrong instructions or registers, or reorder
+    /// operations, potentially resulting in runtime errors.
+    pub INLINE_ALWAYS_MISMATCHING_TARGET_FEATURES,
+    Warn,
+    r#"detects when a function annotated with `#[inline(always)]` and `#[target_feature(enable = "..")]` is inlined into a caller without the required target feature"#,
+}
diff --git a/compiler/rustc_llvm/Cargo.toml b/compiler/rustc_llvm/Cargo.toml
index e74de453be2..cd352ce3d0f 100644
--- a/compiler/rustc_llvm/Cargo.toml
+++ b/compiler/rustc_llvm/Cargo.toml
@@ -5,7 +5,7 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-libc.workspace = true
+libc = "0.2.73"
 # tidy-alphabetical-end
 
 [build-dependencies]
diff --git a/compiler/rustc_llvm/build.rs b/compiler/rustc_llvm/build.rs
index d01f79dcade..225ab8c846d 100644
--- a/compiler/rustc_llvm/build.rs
+++ b/compiler/rustc_llvm/build.rs
@@ -174,10 +174,10 @@ fn main() {
 
     // Prevent critical warnings when we're compiling from rust-lang/rust CI,
     // except on MSVC, as the compiler throws warnings that are only reported
-    // for this platform. See https://github.com/rust-lang/rust/pull/145031#issuecomment-3162677202
-    // FIXME(llvm22): It looks like the specific problem code has been removed
-    // in https://github.com/llvm/llvm-project/commit/e8fc808bf8e78a3c80d1f8e293a92677b92366dd,
-    // retry msvc once we bump our LLVM version.
+    // for this platform. See https://github.com/rust-lang/rust/pull/145031#issuecomment-3162677202.
+    // Moreover, LLVM generally guarantees warning-freedom only when building with Clang, as other
+    // compilers have too many false positives. This is typically the case for MSVC, which throws
+    // many false-positive warnings. We keep it excluded, for these reasons.
     if std::env::var_os("CI").is_some() && !target.contains("msvc") {
         cfg.warnings_into_errors(true);
     }
diff --git a/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp
index dd492325814..3bb1533c2fe 100644
--- a/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp
@@ -1568,12 +1568,11 @@ extern "C" bool LLVMRustPrepareThinLTOImport(const LLVMRustThinLTOData *Data,
   return true;
 }
 
-extern "C" LLVMRustThinLTOBuffer *
-LLVMRustThinLTOBufferCreate(LLVMModuleRef M, bool is_thin, bool emit_summary) {
+extern "C" LLVMRustThinLTOBuffer *LLVMRustThinLTOBufferCreate(LLVMModuleRef M,
+                                                              bool is_thin) {
   auto Ret = std::make_unique<LLVMRustThinLTOBuffer>();
   {
     auto OS = raw_string_ostream(Ret->data);
-    auto ThinLinkOS = raw_string_ostream(Ret->thin_link_data);
     {
       if (is_thin) {
         PassBuilder PB;
@@ -1587,11 +1586,7 @@ LLVMRustThinLTOBufferCreate(LLVMModuleRef M, bool is_thin, bool emit_summary) {
         PB.registerLoopAnalyses(LAM);
         PB.crossRegisterProxies(LAM, FAM, CGAM, MAM);
         ModulePassManager MPM;
-        // We only pass ThinLinkOS to be filled in if we want the summary,
-        // because otherwise LLVM does extra work and may double-emit some
-        // errors or warnings.
-        MPM.addPass(
-            ThinLTOBitcodeWriterPass(OS, emit_summary ? &ThinLinkOS : nullptr));
+        MPM.addPass(ThinLTOBitcodeWriterPass(OS, nullptr));
         MPM.run(*unwrap(M), MAM);
       } else {
         WriteBitcodeToFile(*unwrap(M), OS);
diff --git a/compiler/rustc_log/Cargo.toml b/compiler/rustc_log/Cargo.toml
index e9d7b4723f8..2332ff9b323 100644
--- a/compiler/rustc_log/Cargo.toml
+++ b/compiler/rustc_log/Cargo.toml
@@ -5,10 +5,10 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-tracing-core = "=0.1.30" # FIXME(Nilstrieb) tracing has a deadlock: https://github.com/tokio-rs/tracing/issues/2635
+# tracing > 0.1.37 have huge binary size / instructions regression
+tracing = "=0.1.37"
 tracing-subscriber = { version = "0.3.3", default-features = false, features = ["fmt", "env-filter", "smallvec", "parking_lot", "ansi"] }
 tracing-tree = "0.3.1"
-tracing.workspace = true
 # tidy-alphabetical-end
 
 [features]
diff --git a/compiler/rustc_log/src/lib.rs b/compiler/rustc_log/src/lib.rs
index df648bbd489..26475eec1c1 100644
--- a/compiler/rustc_log/src/lib.rs
+++ b/compiler/rustc_log/src/lib.rs
@@ -38,7 +38,7 @@ use std::fmt::{self, Display};
 use std::io::{self, IsTerminal};
 
 use tracing::dispatcher::SetGlobalDefaultError;
-use tracing_core::{Event, Subscriber};
+use tracing::{Event, Subscriber};
 use tracing_subscriber::filter::{Directive, EnvFilter, LevelFilter};
 use tracing_subscriber::fmt::FmtContext;
 use tracing_subscriber::fmt::format::{self, FormatEvent, FormatFields};
diff --git a/compiler/rustc_macros/Cargo.toml b/compiler/rustc_macros/Cargo.toml
index 5add2691b88..f9d3b758359 100644
--- a/compiler/rustc_macros/Cargo.toml
+++ b/compiler/rustc_macros/Cargo.toml
@@ -8,8 +8,8 @@ proc-macro = true
 
 [dependencies]
 # tidy-alphabetical-start
-proc-macro2.workspace = true
-quote.workspace = true
+proc-macro2 = "1"
+quote = "1"
 syn = { version = "2.0.9", features = ["full"] }
 synstructure = "0.13.0"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_metadata/Cargo.toml b/compiler/rustc_metadata/Cargo.toml
index a8f3dd18353..1b40d9f684e 100644
--- a/compiler/rustc_metadata/Cargo.toml
+++ b/compiler/rustc_metadata/Cargo.toml
@@ -5,9 +5,9 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-bitflags.workspace = true
+bitflags = "2.4.1"
 libloading = "0.8.0"
-odht.workspace = true
+odht = { version = "0.3.1", features = ["nightly"] }
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_attr_parsing = { path = "../rustc_attr_parsing" }
@@ -30,11 +30,11 @@ rustc_serialize = { path = "../rustc_serialize" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
-tempfile.workspace = true
-tracing.workspace = true
+tempfile = "3.7.1"
+tracing = "0.1"
 # tidy-alphabetical-end
 
 [target.'cfg(target_os = "aix")'.dependencies]
 # tidy-alphabetical-start
-libc.workspace = true
+libc = "0.2"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_metadata/src/creader.rs b/compiler/rustc_metadata/src/creader.rs
index 5d776ea581d..9e23da88f5e 100644
--- a/compiler/rustc_metadata/src/creader.rs
+++ b/compiler/rustc_metadata/src/creader.rs
@@ -412,7 +412,7 @@ impl CStore {
             match (&left_name_val, &right_name_val) {
                 (Some(l), Some(r)) => match l.1.opt.cmp(&r.1.opt) {
                     cmp::Ordering::Equal => {
-                        if l.0.tech_value != r.0.tech_value {
+                        if !l.1.consistent(&tcx.sess.opts, Some(&r.1)) {
                             report_diff(
                                 &l.0.prefix,
                                 &l.0.name,
@@ -424,20 +424,28 @@ impl CStore {
                         right_name_val = None;
                     }
                     cmp::Ordering::Greater => {
-                        report_diff(&r.0.prefix, &r.0.name, None, Some(&r.1.value_name));
+                        if !r.1.consistent(&tcx.sess.opts, None) {
+                            report_diff(&r.0.prefix, &r.0.name, None, Some(&r.1.value_name));
+                        }
                         right_name_val = None;
                     }
                     cmp::Ordering::Less => {
-                        report_diff(&l.0.prefix, &l.0.name, Some(&l.1.value_name), None);
+                        if !l.1.consistent(&tcx.sess.opts, None) {
+                            report_diff(&l.0.prefix, &l.0.name, Some(&l.1.value_name), None);
+                        }
                         left_name_val = None;
                     }
                 },
                 (Some(l), None) => {
-                    report_diff(&l.0.prefix, &l.0.name, Some(&l.1.value_name), None);
+                    if !l.1.consistent(&tcx.sess.opts, None) {
+                        report_diff(&l.0.prefix, &l.0.name, Some(&l.1.value_name), None);
+                    }
                     left_name_val = None;
                 }
                 (None, Some(r)) => {
-                    report_diff(&r.0.prefix, &r.0.name, None, Some(&r.1.value_name));
+                    if !r.1.consistent(&tcx.sess.opts, None) {
+                        report_diff(&r.0.prefix, &r.0.name, None, Some(&r.1.value_name));
+                    }
                     right_name_val = None;
                 }
                 (None, None) => break,
diff --git a/compiler/rustc_middle/Cargo.toml b/compiler/rustc_middle/Cargo.toml
index f0832405567..fbcce16cedc 100644
--- a/compiler/rustc_middle/Cargo.toml
+++ b/compiler/rustc_middle/Cargo.toml
@@ -5,12 +5,12 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-bitflags.workspace = true
-either.workspace = true
+bitflags = "2.4.1"
+either = "1.5.0"
 gsgdt = "0.1.2"
-polonius-engine.workspace = true
+polonius-engine = "0.13.0"
 rustc_abi = { path = "../rustc_abi" }
-rustc_apfloat.workspace = true
+rustc_apfloat = "0.2.0"
 rustc_arena = { path = "../rustc_arena" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_ir = { path = "../rustc_ast_ir" }
@@ -34,8 +34,8 @@ rustc_target = { path = "../rustc_target" }
 rustc_thread_pool = { path = "../rustc_thread_pool" }
 rustc_type_ir = { path = "../rustc_type_ir" }
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
-thin-vec.workspace = true
-tracing.workspace = true
+thin-vec = "0.2.12"
+tracing = "0.1"
 # tidy-alphabetical-end
 
 [features]
diff --git a/compiler/rustc_middle/src/arena.rs b/compiler/rustc_middle/src/arena.rs
index 4b6e38cd52d..52fbe19c9f2 100644
--- a/compiler/rustc_middle/src/arena.rs
+++ b/compiler/rustc_middle/src/arena.rs
@@ -80,6 +80,7 @@ macro_rules! arena_types {
                 rustc_middle::infer::canonical::Canonical<'tcx,
                     rustc_middle::infer::canonical::QueryResponse<'tcx, rustc_middle::ty::Ty<'tcx>>
                 >,
+            [] inspect_probe: rustc_middle::traits::solve::inspect::Probe<rustc_middle::ty::TyCtxt<'tcx>>,
             [] effective_visibilities: rustc_middle::middle::privacy::EffectiveVisibilities,
             [] upvars_mentioned: rustc_data_structures::fx::FxIndexMap<rustc_hir::HirId, rustc_hir::Upvar>,
             [] dyn_compatibility_violations: rustc_middle::traits::DynCompatibilityViolation,
diff --git a/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs b/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
index 866736f74a0..8b4503073b0 100644
--- a/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
+++ b/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
@@ -82,7 +82,7 @@ pub enum TargetFeatureKind {
     Forced,
 }
 
-#[derive(Copy, Clone, Debug, TyEncodable, TyDecodable, HashStable)]
+#[derive(Copy, Clone, Debug, Eq, PartialEq, TyEncodable, TyDecodable, HashStable)]
 pub struct TargetFeature {
     /// The name of the target feature (e.g. "avx")
     pub name: Symbol,
diff --git a/compiler/rustc_middle/src/middle/region.rs b/compiler/rustc_middle/src/middle/region.rs
index 857d041224f..5367e5edd49 100644
--- a/compiler/rustc_middle/src/middle/region.rs
+++ b/compiler/rustc_middle/src/middle/region.rs
@@ -299,4 +299,43 @@ impl ScopeTree {
 
         true
     }
+
+    /// Returns the scope of non-lifetime-extended temporaries within a given scope, as well as
+    /// whether we've recorded a potential backwards-incompatible change to lint on.
+    /// Returns `None` when no enclosing temporary scope is found, such as for static items.
+    pub fn default_temporary_scope(&self, inner: Scope) -> (Option<Scope>, Option<Scope>) {
+        let mut id = inner;
+        let mut backwards_incompatible = None;
+
+        while let Some(&p) = self.parent_map.get(&id) {
+            match p.data {
+                ScopeData::Destruction => {
+                    debug!("temporary_scope({inner:?}) = {id:?} [enclosing]");
+                    return (Some(id), backwards_incompatible);
+                }
+                ScopeData::IfThenRescope | ScopeData::MatchGuard => {
+                    debug!("temporary_scope({inner:?}) = {p:?} [enclosing]");
+                    return (Some(p), backwards_incompatible);
+                }
+                ScopeData::Node
+                | ScopeData::CallSite
+                | ScopeData::Arguments
+                | ScopeData::IfThen
+                | ScopeData::Remainder(_) => {
+                    // If we haven't already passed through a backwards-incompatible node,
+                    // then check if we are passing through one now and record it if so.
+                    // This is for now only working for cases where a temporary lifetime is
+                    // *shortened*.
+                    if backwards_incompatible.is_none() {
+                        backwards_incompatible =
+                            self.backwards_incompatible_scope.get(&p.local_id).copied();
+                    }
+                    id = p
+                }
+            }
+        }
+
+        debug!("temporary_scope({inner:?}) = None");
+        (None, backwards_incompatible)
+    }
 }
diff --git a/compiler/rustc_middle/src/mir/consts.rs b/compiler/rustc_middle/src/mir/consts.rs
index 164433aede2..5764a9c84ee 100644
--- a/compiler/rustc_middle/src/mir/consts.rs
+++ b/compiler/rustc_middle/src/mir/consts.rs
@@ -579,7 +579,7 @@ impl<'tcx> Display for Const<'tcx> {
 }
 
 ///////////////////////////////////////////////////////////////////////////
-/// Const-related utilities
+// Const-related utilities
 
 impl<'tcx> TyCtxt<'tcx> {
     pub fn span_as_caller_location(self, span: Span) -> ConstValue {
diff --git a/compiler/rustc_middle/src/mir/statement.rs b/compiler/rustc_middle/src/mir/statement.rs
index 6e52bc775ef..ec2a8e86077 100644
--- a/compiler/rustc_middle/src/mir/statement.rs
+++ b/compiler/rustc_middle/src/mir/statement.rs
@@ -408,14 +408,14 @@ impl<'tcx> Place<'tcx> {
         self.as_ref().project_deeper(more_projections, tcx)
     }
 
-    pub fn ty_from<D: ?Sized>(
+    pub fn ty_from<D>(
         local: Local,
         projection: &[PlaceElem<'tcx>],
         local_decls: &D,
         tcx: TyCtxt<'tcx>,
     ) -> PlaceTy<'tcx>
     where
-        D: HasLocalDecls<'tcx>,
+        D: ?Sized + HasLocalDecls<'tcx>,
     {
         PlaceTy::from_ty(local_decls.local_decls()[local].ty).multi_projection_ty(tcx, projection)
     }
@@ -529,9 +529,9 @@ impl<'tcx> PlaceRef<'tcx> {
         Place { local: self.local, projection: tcx.mk_place_elems(new_projections) }
     }
 
-    pub fn ty<D: ?Sized>(&self, local_decls: &D, tcx: TyCtxt<'tcx>) -> PlaceTy<'tcx>
+    pub fn ty<D>(&self, local_decls: &D, tcx: TyCtxt<'tcx>) -> PlaceTy<'tcx>
     where
-        D: HasLocalDecls<'tcx>,
+        D: ?Sized + HasLocalDecls<'tcx>,
     {
         Place::ty_from(self.local, self.projection, local_decls, tcx)
     }
@@ -630,9 +630,9 @@ impl<'tcx> Operand<'tcx> {
         if let ty::FnDef(def_id, args) = *const_ty.kind() { Some((def_id, args)) } else { None }
     }
 
-    pub fn ty<D: ?Sized>(&self, local_decls: &D, tcx: TyCtxt<'tcx>) -> Ty<'tcx>
+    pub fn ty<D>(&self, local_decls: &D, tcx: TyCtxt<'tcx>) -> Ty<'tcx>
     where
-        D: HasLocalDecls<'tcx>,
+        D: ?Sized + HasLocalDecls<'tcx>,
     {
         match self {
             &Operand::Copy(ref l) | &Operand::Move(ref l) => l.ty(local_decls, tcx).ty,
@@ -640,9 +640,9 @@ impl<'tcx> Operand<'tcx> {
         }
     }
 
-    pub fn span<D: ?Sized>(&self, local_decls: &D) -> Span
+    pub fn span<D>(&self, local_decls: &D) -> Span
     where
-        D: HasLocalDecls<'tcx>,
+        D: ?Sized + HasLocalDecls<'tcx>,
     {
         match self {
             &Operand::Copy(ref l) | &Operand::Move(ref l) => {
@@ -674,7 +674,7 @@ impl<'tcx> ConstOperand<'tcx> {
 }
 
 ///////////////////////////////////////////////////////////////////////////
-/// Rvalues
+// Rvalues
 
 pub enum RvalueInitializationState {
     Shallow,
@@ -721,9 +721,9 @@ impl<'tcx> Rvalue<'tcx> {
         }
     }
 
-    pub fn ty<D: ?Sized>(&self, local_decls: &D, tcx: TyCtxt<'tcx>) -> Ty<'tcx>
+    pub fn ty<D>(&self, local_decls: &D, tcx: TyCtxt<'tcx>) -> Ty<'tcx>
     where
-        D: HasLocalDecls<'tcx>,
+        D: ?Sized + HasLocalDecls<'tcx>,
     {
         match *self {
             Rvalue::Use(ref operand) => operand.ty(local_decls, tcx),
diff --git a/compiler/rustc_middle/src/mir/visit.rs b/compiler/rustc_middle/src/mir/visit.rs
index 904d78d69b6..b498b7b8912 100644
--- a/compiler/rustc_middle/src/mir/visit.rs
+++ b/compiler/rustc_middle/src/mir/visit.rs
@@ -1415,6 +1415,24 @@ impl PlaceContext {
         )
     }
 
+    /// Returns `true` if this place context may be used to know the address of the given place.
+    #[inline]
+    pub fn may_observe_address(self) -> bool {
+        matches!(
+            self,
+            PlaceContext::NonMutatingUse(
+                NonMutatingUseContext::SharedBorrow
+                    | NonMutatingUseContext::RawBorrow
+                    | NonMutatingUseContext::FakeBorrow
+            ) | PlaceContext::MutatingUse(
+                MutatingUseContext::Drop
+                    | MutatingUseContext::Borrow
+                    | MutatingUseContext::RawBorrow
+                    | MutatingUseContext::AsmOutput
+            )
+        )
+    }
+
     /// Returns `true` if this place context represents a storage live or storage dead marker.
     #[inline]
     pub fn is_storage_marker(self) -> bool {
diff --git a/compiler/rustc_middle/src/query/erase.rs b/compiler/rustc_middle/src/query/erase.rs
index ea62461ebeb..bea2191c560 100644
--- a/compiler/rustc_middle/src/query/erase.rs
+++ b/compiler/rustc_middle/src/query/erase.rs
@@ -6,6 +6,7 @@ use rustc_span::ErrorGuaranteed;
 
 use crate::mir::interpret::EvalToValTreeResult;
 use crate::query::CyclePlaceholder;
+use crate::traits::solve;
 use crate::ty::adjustment::CoerceUnsizedInfo;
 use crate::ty::{self, Ty, TyCtxt};
 use crate::{mir, traits};
@@ -219,6 +220,10 @@ impl<T0, T1> EraseType for (&'_ T0, &'_ T1) {
     type Result = [u8; size_of::<(&'static (), &'static ())>()];
 }
 
+impl<T0> EraseType for (solve::QueryResult<'_>, &'_ T0) {
+    type Result = [u8; size_of::<(solve::QueryResult<'static>, &'static ())>()];
+}
+
 impl<T0, T1> EraseType for (&'_ T0, &'_ [T1]) {
     type Result = [u8; size_of::<(&'static (), &'static [()])>()];
 }
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index 8ce70f75c67..874cee54c7c 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -131,7 +131,7 @@ use crate::traits::query::{
 };
 use crate::traits::{
     CodegenObligationError, DynCompatibilityViolation, EvaluationResult, ImplSource,
-    ObligationCause, OverflowError, WellFormedLoc, specialization_graph,
+    ObligationCause, OverflowError, WellFormedLoc, solve, specialization_graph,
 };
 use crate::ty::fast_reject::SimplifiedType;
 use crate::ty::layout::ValidityRequirement;
@@ -2563,6 +2563,14 @@ rustc_queries! {
         desc { "computing autoderef types for `{}`", goal.canonical.value.value }
     }
 
+    /// Used by `-Znext-solver` to compute proof trees.
+    query evaluate_root_goal_for_proof_tree_raw(
+        goal: solve::CanonicalInput<'tcx>,
+    ) -> (solve::QueryResult<'tcx>, &'tcx solve::inspect::Probe<TyCtxt<'tcx>>) {
+        no_hash
+        desc { "computing proof tree for `{}`", goal.canonical.value.goal.predicate }
+    }
+
     /// Returns the Rust target features for the current target. These are not always the same as LLVM target features!
     query rust_target_features(_: CrateNum) -> &'tcx UnordMap<String, rustc_target::target_features::Stability> {
         arena_cache
diff --git a/compiler/rustc_middle/src/ty/codec.rs b/compiler/rustc_middle/src/ty/codec.rs
index 95759d1f31a..3f37595d0ee 100644
--- a/compiler/rustc_middle/src/ty/codec.rs
+++ b/compiler/rustc_middle/src/ty/codec.rs
@@ -216,10 +216,7 @@ impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for ty::ParamEnv<'tcx> {
 #[inline]
 fn decode_arena_allocable<'tcx, D: TyDecoder<'tcx>, T: ArenaAllocatable<'tcx> + Decodable<D>>(
     decoder: &mut D,
-) -> &'tcx T
-where
-    D: TyDecoder<'tcx>,
-{
+) -> &'tcx T {
     decoder.interner().arena.alloc(Decodable::decode(decoder))
 }
 
@@ -230,10 +227,7 @@ fn decode_arena_allocable_slice<
     T: ArenaAllocatable<'tcx> + Decodable<D>,
 >(
     decoder: &mut D,
-) -> &'tcx [T]
-where
-    D: TyDecoder<'tcx>,
-{
+) -> &'tcx [T] {
     decoder.interner().arena.alloc_from_iter(<Vec<T> as Decodable<D>>::decode(decoder))
 }
 
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 07cfc87250b..de6fa4c344e 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -72,9 +72,9 @@ use crate::query::plumbing::QuerySystem;
 use crate::query::{IntoQueryParam, LocalCrate, Providers, TyCtxtAt};
 use crate::thir::Thir;
 use crate::traits;
-use crate::traits::solve;
 use crate::traits::solve::{
-    ExternalConstraints, ExternalConstraintsData, PredefinedOpaques, PredefinedOpaquesData,
+    self, CanonicalInput, ExternalConstraints, ExternalConstraintsData, PredefinedOpaques,
+    PredefinedOpaquesData, QueryResult, inspect,
 };
 use crate::ty::predicate::ExistentialPredicateStableCmpExt as _;
 use crate::ty::{
@@ -756,6 +756,17 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
             self.opaque_types_defined_by(defining_anchor).iter().chain(coroutines_defined_by),
         )
     }
+
+    type Probe = &'tcx inspect::Probe<TyCtxt<'tcx>>;
+    fn mk_probe(self, probe: inspect::Probe<Self>) -> &'tcx inspect::Probe<TyCtxt<'tcx>> {
+        self.arena.alloc(probe)
+    }
+    fn evaluate_root_goal_for_proof_tree_raw(
+        self,
+        canonical_goal: CanonicalInput<'tcx>,
+    ) -> (QueryResult<'tcx>, &'tcx inspect::Probe<TyCtxt<'tcx>>) {
+        self.evaluate_root_goal_for_proof_tree_raw(canonical_goal)
+    }
 }
 
 macro_rules! bidirectional_lang_item_map {
diff --git a/compiler/rustc_middle/src/ty/generics.rs b/compiler/rustc_middle/src/ty/generics.rs
index c7b3b541549..b6b10e24585 100644
--- a/compiler/rustc_middle/src/ty/generics.rs
+++ b/compiler/rustc_middle/src/ty/generics.rs
@@ -13,7 +13,7 @@ use crate::ty::{EarlyBinder, GenericArgsRef};
 pub enum GenericParamDefKind {
     Lifetime,
     Type { has_default: bool, synthetic: bool },
-    Const { has_default: bool, synthetic: bool },
+    Const { has_default: bool },
 }
 
 impl GenericParamDefKind {
diff --git a/compiler/rustc_middle/src/ty/rvalue_scopes.rs b/compiler/rustc_middle/src/ty/rvalue_scopes.rs
index 7dfe2d28051..8b92e48ed1a 100644
--- a/compiler/rustc_middle/src/ty/rvalue_scopes.rs
+++ b/compiler/rustc_middle/src/ty/rvalue_scopes.rs
@@ -35,41 +35,8 @@ impl RvalueScopes {
         // if there's one. Static items, for instance, won't
         // have an enclosing scope, hence no scope will be
         // returned.
-        let mut id = Scope { local_id: expr_id, data: ScopeData::Node };
-        let mut backwards_incompatible = None;
-
-        while let Some(&p) = region_scope_tree.parent_map.get(&id) {
-            match p.data {
-                ScopeData::Destruction => {
-                    debug!("temporary_scope({expr_id:?}) = {id:?} [enclosing]");
-                    return (Some(id), backwards_incompatible);
-                }
-                ScopeData::IfThenRescope | ScopeData::MatchGuard => {
-                    debug!("temporary_scope({expr_id:?}) = {p:?} [enclosing]");
-                    return (Some(p), backwards_incompatible);
-                }
-                ScopeData::Node
-                | ScopeData::CallSite
-                | ScopeData::Arguments
-                | ScopeData::IfThen
-                | ScopeData::Remainder(_) => {
-                    // If we haven't already passed through a backwards-incompatible node,
-                    // then check if we are passing through one now and record it if so.
-                    // This is for now only working for cases where a temporary lifetime is
-                    // *shortened*.
-                    if backwards_incompatible.is_none() {
-                        backwards_incompatible = region_scope_tree
-                            .backwards_incompatible_scope
-                            .get(&p.local_id)
-                            .copied();
-                    }
-                    id = p
-                }
-            }
-        }
-
-        debug!("temporary_scope({expr_id:?}) = None");
-        (None, backwards_incompatible)
+        region_scope_tree
+            .default_temporary_scope(Scope { local_id: expr_id, data: ScopeData::Node })
     }
 
     /// Make an association between a sub-expression and an extended lifetime
diff --git a/compiler/rustc_mir_build/Cargo.toml b/compiler/rustc_mir_build/Cargo.toml
index 440cb0bdbf3..f756f0a19ee 100644
--- a/compiler/rustc_mir_build/Cargo.toml
+++ b/compiler/rustc_mir_build/Cargo.toml
@@ -5,9 +5,9 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-itertools.workspace = true
+itertools = "0.12"
 rustc_abi = { path = "../rustc_abi" }
-rustc_apfloat.workspace = true
+rustc_apfloat = "0.2.0"
 rustc_arena = { path = "../rustc_arena" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_data_structures = { path = "../rustc_data_structures" }
@@ -23,5 +23,5 @@ rustc_pattern_analysis = { path = "../rustc_pattern_analysis" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_trait_selection = { path = "../rustc_trait_selection" }
-tracing.workspace = true
+tracing = "0.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_mir_dataflow/Cargo.toml b/compiler/rustc_mir_dataflow/Cargo.toml
index 11713bb77f1..9621f9f20bd 100644
--- a/compiler/rustc_mir_dataflow/Cargo.toml
+++ b/compiler/rustc_mir_dataflow/Cargo.toml
@@ -5,7 +5,7 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-polonius-engine.workspace = true
+polonius-engine = "0.13.0"
 regex = "1"
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
@@ -18,5 +18,5 @@ rustc_macros = { path = "../rustc_macros" }
 rustc_middle = { path = "../rustc_middle" }
 rustc_span = { path = "../rustc_span" }
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
-tracing.workspace = true
+tracing = "0.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_mir_dataflow/src/impls/liveness.rs b/compiler/rustc_mir_dataflow/src/impls/liveness.rs
index 6ec1b03a34e..5eba474a60c 100644
--- a/compiler/rustc_mir_dataflow/src/impls/liveness.rs
+++ b/compiler/rustc_mir_dataflow/src/impls/liveness.rs
@@ -92,7 +92,7 @@ impl<'tcx> Visitor<'tcx> for TransferFunction<'_> {
         }
 
         match DefUse::for_place(*place, context) {
-            Some(DefUse::Def) => {
+            DefUse::Def => {
                 if let PlaceContext::MutatingUse(
                     MutatingUseContext::Call | MutatingUseContext::AsmOutput,
                 ) = context
@@ -105,8 +105,8 @@ impl<'tcx> Visitor<'tcx> for TransferFunction<'_> {
                     self.0.kill(place.local);
                 }
             }
-            Some(DefUse::Use) => self.0.gen_(place.local),
-            None => {}
+            DefUse::Use => self.0.gen_(place.local),
+            DefUse::PartialWrite | DefUse::NonUse => {}
         }
 
         self.visit_projection(place.as_ref(), context, location);
@@ -131,23 +131,29 @@ impl<'tcx> Visitor<'tcx> for YieldResumeEffect<'_> {
 }
 
 #[derive(Eq, PartialEq, Clone)]
-enum DefUse {
+pub enum DefUse {
+    /// Full write to the local.
     Def,
+    /// Read of any part of the local.
     Use,
+    /// Partial write to the local.
+    PartialWrite,
+    /// Non-use, like debuginfo.
+    NonUse,
 }
 
 impl DefUse {
     fn apply(state: &mut DenseBitSet<Local>, place: Place<'_>, context: PlaceContext) {
         match DefUse::for_place(place, context) {
-            Some(DefUse::Def) => state.kill(place.local),
-            Some(DefUse::Use) => state.gen_(place.local),
-            None => {}
+            DefUse::Def => state.kill(place.local),
+            DefUse::Use => state.gen_(place.local),
+            DefUse::PartialWrite | DefUse::NonUse => {}
         }
     }
 
-    fn for_place(place: Place<'_>, context: PlaceContext) -> Option<DefUse> {
+    pub fn for_place(place: Place<'_>, context: PlaceContext) -> DefUse {
         match context {
-            PlaceContext::NonUse(_) => None,
+            PlaceContext::NonUse(_) => DefUse::NonUse,
 
             PlaceContext::MutatingUse(
                 MutatingUseContext::Call
@@ -156,21 +162,20 @@ impl DefUse {
                 | MutatingUseContext::Store
                 | MutatingUseContext::Deinit,
             ) => {
+                // Treat derefs as a use of the base local. `*p = 4` is not a def of `p` but a use.
                 if place.is_indirect() {
-                    // Treat derefs as a use of the base local. `*p = 4` is not a def of `p` but a
-                    // use.
-                    Some(DefUse::Use)
+                    DefUse::Use
                 } else if place.projection.is_empty() {
-                    Some(DefUse::Def)
+                    DefUse::Def
                 } else {
-                    None
+                    DefUse::PartialWrite
                 }
             }
 
             // Setting the discriminant is not a use because it does no reading, but it is also not
             // a def because it does not overwrite the whole place
             PlaceContext::MutatingUse(MutatingUseContext::SetDiscriminant) => {
-                place.is_indirect().then_some(DefUse::Use)
+                if place.is_indirect() { DefUse::Use } else { DefUse::PartialWrite }
             }
 
             // All other contexts are uses...
@@ -188,7 +193,7 @@ impl DefUse {
                 | NonMutatingUseContext::PlaceMention
                 | NonMutatingUseContext::FakeBorrow
                 | NonMutatingUseContext::SharedBorrow,
-            ) => Some(DefUse::Use),
+            ) => DefUse::Use,
 
             PlaceContext::MutatingUse(MutatingUseContext::Projection)
             | PlaceContext::NonMutatingUse(NonMutatingUseContext::Projection) => {
diff --git a/compiler/rustc_mir_dataflow/src/impls/mod.rs b/compiler/rustc_mir_dataflow/src/impls/mod.rs
index 3f29b819a6d..6d573e1c00e 100644
--- a/compiler/rustc_mir_dataflow/src/impls/mod.rs
+++ b/compiler/rustc_mir_dataflow/src/impls/mod.rs
@@ -9,7 +9,8 @@ pub use self::initialized::{
     MaybeUninitializedPlaces, MaybeUninitializedPlacesDomain,
 };
 pub use self::liveness::{
-    MaybeLiveLocals, MaybeTransitiveLiveLocals, TransferFunction as LivenessTransferFunction,
+    DefUse, MaybeLiveLocals, MaybeTransitiveLiveLocals,
+    TransferFunction as LivenessTransferFunction,
 };
 pub use self::storage_liveness::{
     MaybeRequiresStorage, MaybeStorageDead, MaybeStorageLive, always_storage_live_locals,
diff --git a/compiler/rustc_mir_dataflow/src/points.rs b/compiler/rustc_mir_dataflow/src/points.rs
index 70d1a34b5fb..e3d1e04a319 100644
--- a/compiler/rustc_mir_dataflow/src/points.rs
+++ b/compiler/rustc_mir_dataflow/src/points.rs
@@ -1,9 +1,5 @@
-use rustc_index::bit_set::DenseBitSet;
-use rustc_index::interval::SparseIntervalMatrix;
 use rustc_index::{Idx, IndexVec};
-use rustc_middle::mir::{self, BasicBlock, Body, Location};
-
-use crate::framework::{Analysis, Results, ResultsVisitor, visit_results};
+use rustc_middle::mir::{BasicBlock, Body, Location};
 
 /// Maps between a `Location` and a `PointIndex` (and vice versa).
 pub struct DenseLocationMap {
@@ -93,65 +89,3 @@ rustc_index::newtype_index! {
     #[debug_format = "PointIndex({})"]
     pub struct PointIndex {}
 }
-
-/// Add points depending on the result of the given dataflow analysis.
-pub fn save_as_intervals<'tcx, N, A>(
-    elements: &DenseLocationMap,
-    body: &mir::Body<'tcx>,
-    mut analysis: A,
-    results: Results<A::Domain>,
-) -> SparseIntervalMatrix<N, PointIndex>
-where
-    N: Idx,
-    A: Analysis<'tcx, Domain = DenseBitSet<N>>,
-{
-    let values = SparseIntervalMatrix::new(elements.num_points());
-    let mut visitor = Visitor { elements, values };
-    visit_results(
-        body,
-        body.basic_blocks.reverse_postorder().iter().copied(),
-        &mut analysis,
-        &results,
-        &mut visitor,
-    );
-    visitor.values
-}
-
-struct Visitor<'a, N: Idx> {
-    elements: &'a DenseLocationMap,
-    values: SparseIntervalMatrix<N, PointIndex>,
-}
-
-impl<'tcx, A, N> ResultsVisitor<'tcx, A> for Visitor<'_, N>
-where
-    A: Analysis<'tcx, Domain = DenseBitSet<N>>,
-    N: Idx,
-{
-    fn visit_after_primary_statement_effect<'mir>(
-        &mut self,
-        _analysis: &mut A,
-        state: &A::Domain,
-        _statement: &'mir mir::Statement<'tcx>,
-        location: Location,
-    ) {
-        let point = self.elements.point_from_location(location);
-        // Use internal iterator manually as it is much more efficient.
-        state.iter().for_each(|node| {
-            self.values.insert(node, point);
-        });
-    }
-
-    fn visit_after_primary_terminator_effect<'mir>(
-        &mut self,
-        _analysis: &mut A,
-        state: &A::Domain,
-        _terminator: &'mir mir::Terminator<'tcx>,
-        location: Location,
-    ) {
-        let point = self.elements.point_from_location(location);
-        // Use internal iterator manually as it is much more efficient.
-        state.iter().for_each(|node| {
-            self.values.insert(node, point);
-        });
-    }
-}
diff --git a/compiler/rustc_mir_dataflow/src/value_analysis.rs b/compiler/rustc_mir_dataflow/src/value_analysis.rs
index 005e7973130..9a00831dc01 100644
--- a/compiler/rustc_mir_dataflow/src/value_analysis.rs
+++ b/compiler/rustc_mir_dataflow/src/value_analysis.rs
@@ -6,7 +6,7 @@ use rustc_data_structures::fx::{FxHashMap, FxIndexSet, StdEntry};
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_index::IndexVec;
 use rustc_index::bit_set::DenseBitSet;
-use rustc_middle::mir::visit::{MutatingUseContext, PlaceContext, Visitor};
+use rustc_middle::mir::visit::{PlaceContext, Visitor};
 use rustc_middle::mir::*;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use tracing::debug;
@@ -917,12 +917,7 @@ pub fn excluded_locals(body: &Body<'_>) -> DenseBitSet<Local> {
 
     impl<'tcx> Visitor<'tcx> for Collector {
         fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, _location: Location) {
-            if (context.is_borrow()
-                || context.is_address_of()
-                || context.is_drop()
-                || context == PlaceContext::MutatingUse(MutatingUseContext::AsmOutput))
-                && !place.is_indirect()
-            {
+            if context.may_observe_address() && !place.is_indirect() {
                 // A pointer to a place could be used to access other places with the same local,
                 // hence we have to exclude the local completely.
                 self.result.insert(place.local);
diff --git a/compiler/rustc_mir_transform/Cargo.toml b/compiler/rustc_mir_transform/Cargo.toml
index 99ef67e2625..08c43a4648c 100644
--- a/compiler/rustc_mir_transform/Cargo.toml
+++ b/compiler/rustc_mir_transform/Cargo.toml
@@ -5,8 +5,8 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-either.workspace = true
-itertools.workspace = true
+either = "1"
+itertools = "0.12"
 rustc_abi = { path = "../rustc_abi" }
 rustc_arena = { path = "../rustc_arena" }
 rustc_ast = { path = "../rustc_ast" }
@@ -26,5 +26,5 @@ rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
 rustc_trait_selection = { path = "../rustc_trait_selection" }
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
-tracing.workspace = true
+tracing = "0.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_mir_transform/src/check_inline_always_target_features.rs b/compiler/rustc_mir_transform/src/check_inline_always_target_features.rs
new file mode 100644
index 00000000000..abad28f0a8f
--- /dev/null
+++ b/compiler/rustc_mir_transform/src/check_inline_always_target_features.rs
@@ -0,0 +1,88 @@
+use rustc_hir::attrs::InlineAttr;
+use rustc_middle::middle::codegen_fn_attrs::{TargetFeature, TargetFeatureKind};
+use rustc_middle::mir::{Body, TerminatorKind};
+use rustc_middle::ty::{self, TyCtxt};
+
+use crate::pass_manager::MirLint;
+
+pub(super) struct CheckInlineAlwaysTargetFeature;
+
+impl<'tcx> MirLint<'tcx> for CheckInlineAlwaysTargetFeature {
+    fn run_lint(&self, tcx: TyCtxt<'tcx>, body: &Body<'tcx>) {
+        check_inline_always_target_features(tcx, body)
+    }
+}
+
+/// `#[target_feature]`-annotated functions can be marked `#[inline]` and will only be inlined if
+/// the target features match (as well as all of the other inlining heuristics). `#[inline(always)]`
+/// will always inline regardless of matching target features, which can result in errors from LLVM.
+/// However, it is desirable to be able to always annotate certain functions (e.g. SIMD intrinsics)
+/// as `#[inline(always)]` but check the target features match in Rust to avoid the LLVM errors.
+///
+/// We check the caller and callee target features to ensure that this can
+/// be done or emit a lint.
+#[inline]
+fn check_inline_always_target_features<'tcx>(tcx: TyCtxt<'tcx>, body: &Body<'tcx>) {
+    let caller_def_id = body.source.def_id().expect_local();
+    if !tcx.def_kind(caller_def_id).has_codegen_attrs() {
+        return;
+    }
+
+    let caller_codegen_fn_attrs = tcx.codegen_fn_attrs(caller_def_id);
+
+    for bb in body.basic_blocks.iter() {
+        let terminator = bb.terminator();
+        match &terminator.kind {
+            TerminatorKind::Call { func, .. } | TerminatorKind::TailCall { func, .. } => {
+                let fn_ty = func.ty(body, tcx);
+                let ty::FnDef(callee_def_id, _) = *fn_ty.kind() else {
+                    continue;
+                };
+
+                if !tcx.def_kind(callee_def_id).has_codegen_attrs() {
+                    continue;
+                }
+                let callee_codegen_fn_attrs = tcx.codegen_fn_attrs(callee_def_id);
+                if callee_codegen_fn_attrs.inline != InlineAttr::Always
+                    || callee_codegen_fn_attrs.target_features.is_empty()
+                {
+                    continue;
+                }
+
+                // Scan the users defined target features and ensure they
+                // match the caller.
+                if tcx.is_target_feature_call_safe(
+                    &callee_codegen_fn_attrs.target_features,
+                    &caller_codegen_fn_attrs
+                        .target_features
+                        .iter()
+                        .cloned()
+                        .chain(tcx.sess.target_features.iter().map(|feat| TargetFeature {
+                            name: *feat,
+                            kind: TargetFeatureKind::Implied,
+                        }))
+                        .collect::<Vec<_>>(),
+                ) {
+                    continue;
+                }
+
+                let callee_only: Vec<_> = callee_codegen_fn_attrs
+                    .target_features
+                    .iter()
+                    .filter(|it| !caller_codegen_fn_attrs.target_features.contains(it))
+                    .filter(|it| !matches!(it.kind, TargetFeatureKind::Implied))
+                    .map(|it| it.name.as_str())
+                    .collect();
+
+                crate::errors::emit_inline_always_target_feature_diagnostic(
+                    tcx,
+                    terminator.source_info.span,
+                    callee_def_id,
+                    caller_def_id.into(),
+                    &callee_only,
+                );
+            }
+            _ => (),
+        }
+    }
+}
diff --git a/compiler/rustc_mir_transform/src/coverage/expansion.rs b/compiler/rustc_mir_transform/src/coverage/expansion.rs
index 91e0528f52f..851bbaeed48 100644
--- a/compiler/rustc_mir_transform/src/coverage/expansion.rs
+++ b/compiler/rustc_mir_transform/src/coverage/expansion.rs
@@ -82,7 +82,7 @@ impl ExpnNode {
         Self {
             expn_id,
 
-            expn_kind: expn_data.kind.clone(),
+            expn_kind: expn_data.kind,
             call_site,
             call_site_expn_id,
 
diff --git a/compiler/rustc_mir_transform/src/cross_crate_inline.rs b/compiler/rustc_mir_transform/src/cross_crate_inline.rs
index b186c2bd775..df98c07f549 100644
--- a/compiler/rustc_mir_transform/src/cross_crate_inline.rs
+++ b/compiler/rustc_mir_transform/src/cross_crate_inline.rs
@@ -135,7 +135,16 @@ impl<'tcx> Visitor<'tcx> for CostChecker<'_, 'tcx> {
                     }
                 }
             }
-            TerminatorKind::Call { unwind, .. } => {
+            TerminatorKind::Call { ref func, unwind, .. } => {
+                // We track calls because they make our function not a leaf (and in theory, the
+                // number of calls indicates how likely this function is to perturb other CGUs).
+                // But intrinsics don't have a body that gets assigned to a CGU, so they are
+                // ignored.
+                if let Some((fn_def_id, _)) = func.const_fn_def()
+                    && self.tcx.has_attr(fn_def_id, sym::rustc_intrinsic)
+                {
+                    return;
+                }
                 self.calls += 1;
                 if let UnwindAction::Cleanup(_) = unwind {
                     self.landing_pads += 1;
diff --git a/compiler/rustc_mir_transform/src/dest_prop.rs b/compiler/rustc_mir_transform/src/dest_prop.rs
index cf7425251e8..9ba2d274691 100644
--- a/compiler/rustc_mir_transform/src/dest_prop.rs
+++ b/compiler/rustc_mir_transform/src/dest_prop.rs
@@ -59,6 +59,12 @@
 //! The first two conditions are simple structural requirements on the `Assign` statements that can
 //! be trivially checked. The third requirement however is more difficult and costly to check.
 //!
+//! ## Current implementation
+//!
+//! The current implementation relies on live range computation to check for conflicts. We only
+//! allow to merge locals that have disjoint live ranges. The live range are defined with
+//! half-statement granularity, so as to make all writes be live for at least a half statement.
+//!
 //! ## Future Improvements
 //!
 //! There are a number of ways in which this pass could be improved in the future:
@@ -117,9 +123,8 @@
 //! - Layout optimizations for coroutines have been added to improve code generation for
 //!   async/await, which are very similar in spirit to what this optimization does.
 //!
-//! Also, rustc now has a simple NRVO pass (see `nrvo.rs`), which handles a subset of the cases that
-//! this destination propagation pass handles, proving that similar optimizations can be performed
-//! on MIR.
+//! [The next approach][attempt 4] computes a conflict matrix between locals by forbidding merging
+//! locals with competing writes or with one write while the other is live.
 //!
 //! ## Pre/Post Optimization
 //!
@@ -130,20 +135,18 @@
 //! [attempt 1]: https://github.com/rust-lang/rust/pull/47954
 //! [attempt 2]: https://github.com/rust-lang/rust/pull/71003
 //! [attempt 3]: https://github.com/rust-lang/rust/pull/72632
+//! [attempt 4]: https://github.com/rust-lang/rust/pull/96451
 
-use rustc_data_structures::fx::{FxIndexMap, IndexEntry, IndexOccupiedEntry};
+use rustc_data_structures::union_find::UnionFind;
 use rustc_index::bit_set::DenseBitSet;
 use rustc_index::interval::SparseIntervalMatrix;
-use rustc_middle::bug;
+use rustc_index::{IndexVec, newtype_index};
 use rustc_middle::mir::visit::{MutVisitor, PlaceContext, Visitor};
-use rustc_middle::mir::{
-    Body, HasLocalDecls, InlineAsmOperand, Local, LocalKind, Location, MirDumper, Operand,
-    PassWhere, Place, Rvalue, Statement, StatementKind, TerminatorKind, traversal,
-};
+use rustc_middle::mir::*;
 use rustc_middle::ty::TyCtxt;
-use rustc_mir_dataflow::Analysis;
-use rustc_mir_dataflow::impls::MaybeLiveLocals;
-use rustc_mir_dataflow::points::{DenseLocationMap, PointIndex, save_as_intervals};
+use rustc_mir_dataflow::impls::{DefUse, MaybeLiveLocals};
+use rustc_mir_dataflow::points::DenseLocationMap;
+use rustc_mir_dataflow::{Analysis, Results};
 use tracing::{debug, trace};
 
 pub(super) struct DestinationPropagation;
@@ -161,84 +164,81 @@ impl<'tcx> crate::MirPass<'tcx> for DestinationPropagation {
         sess.mir_opt_level() >= 3
     }
 
+    #[tracing::instrument(level = "trace", skip(self, tcx, body))]
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         let def_id = body.source.def_id();
-        let mut candidates = Candidates::default();
-        let mut write_info = WriteInfo::default();
-        trace!(func = ?tcx.def_path_str(def_id));
+        trace!(?def_id);
 
         let borrowed = rustc_mir_dataflow::impls::borrowed_locals(body);
 
+        let candidates = Candidates::find(body, &borrowed);
+        trace!(?candidates);
+        if candidates.c.is_empty() {
+            return;
+        }
+
         let live = MaybeLiveLocals.iterate_to_fixpoint(tcx, body, Some("MaybeLiveLocals-DestProp"));
+
         let points = DenseLocationMap::new(body);
-        let mut live = save_as_intervals(&points, body, live.analysis, live.results);
-
-        // In order to avoid having to collect data for every single pair of locals in the body, we
-        // do not allow doing more than one merge for places that are derived from the same local at
-        // once. To avoid missed opportunities, we instead iterate to a fixed point - we'll refer to
-        // each of these iterations as a "round."
-        //
-        // Reaching a fixed point could in theory take up to `min(l, s)` rounds - however, we do not
-        // expect to see MIR like that. To verify this, a test was run against `[rust-lang/regex]` -
-        // the average MIR body saw 1.32 full iterations of this loop. The most that was hit were 30
-        // for a single function. Only 80/2801 (2.9%) of functions saw at least 5.
-        //
-        // [rust-lang/regex]:
-        //     https://github.com/rust-lang/regex/tree/b5372864e2df6a2f5e543a556a62197f50ca3650
-        let mut round_count = 0;
-        loop {
-            // PERF: Can we do something smarter than recalculating the candidates and liveness
-            // results?
-            candidates.reset_and_find(body, &borrowed);
-            trace!(?candidates);
-            dest_prop_mir_dump(tcx, body, &points, &live, round_count);
-
-            FilterInformation::filter_liveness(
-                &mut candidates,
-                &points,
-                &live,
-                &mut write_info,
-                body,
-            );
-
-            // Because we only filter once per round, it is unsound to use a local for more than
-            // one merge operation within a single round of optimizations. We store here which ones
-            // we have already used.
-            let mut merged_locals: DenseBitSet<Local> =
-                DenseBitSet::new_empty(body.local_decls.len());
-
-            // This is the set of merges we will apply this round. It is a subset of the candidates.
-            let mut merges = FxIndexMap::default();
-
-            for (src, candidates) in candidates.c.iter() {
-                if merged_locals.contains(*src) {
-                    continue;
-                }
-                let Some(dest) = candidates.iter().find(|dest| !merged_locals.contains(**dest))
-                else {
-                    continue;
-                };
-
-                // Replace `src` by `dest` everywhere.
-                merges.insert(*src, *dest);
-                merged_locals.insert(*src);
-                merged_locals.insert(*dest);
-
-                // Update liveness information based on the merge we just performed.
-                // Every location where `src` was live, `dest` will be live.
-                live.union_rows(*src, *dest);
+        let mut relevant = RelevantLocals::compute(&candidates, body.local_decls.len());
+        let mut live = save_as_intervals(&points, body, &relevant, live.results);
+
+        dest_prop_mir_dump(tcx, body, &points, &live, &relevant);
+
+        let mut merged_locals = DenseBitSet::new_empty(body.local_decls.len());
+
+        for (src, dst) in candidates.c.into_iter() {
+            trace!(?src, ?dst);
+
+            let Some(mut src) = relevant.find(src) else { continue };
+            let Some(mut dst) = relevant.find(dst) else { continue };
+            if src == dst {
+                continue;
             }
-            trace!(merging = ?merges);
 
-            if merges.is_empty() {
-                break;
+            let Some(src_live_ranges) = live.row(src) else { continue };
+            let Some(dst_live_ranges) = live.row(dst) else { continue };
+            trace!(?src, ?src_live_ranges);
+            trace!(?dst, ?dst_live_ranges);
+
+            if src_live_ranges.disjoint(dst_live_ranges) {
+                // We want to replace `src` by `dst`.
+                let mut orig_src = relevant.original[src];
+                let mut orig_dst = relevant.original[dst];
+
+                // The return place and function arguments are required and cannot be renamed.
+                // This check cannot be made during candidate collection, as we may want to
+                // unify the same non-required local with several required locals.
+                match (is_local_required(orig_src, body), is_local_required(orig_dst, body)) {
+                    // Renaming `src` is ok.
+                    (false, _) => {}
+                    // Renaming `src` is wrong, but renaming `dst` is ok.
+                    (true, false) => {
+                        std::mem::swap(&mut src, &mut dst);
+                        std::mem::swap(&mut orig_src, &mut orig_dst);
+                    }
+                    // Neither local can be renamed, so skip this case.
+                    (true, true) => continue,
+                }
+
+                trace!(?src, ?dst, "merge");
+                merged_locals.insert(orig_src);
+                merged_locals.insert(orig_dst);
+
+                // Replace `src` by `dst`.
+                let head = relevant.union(src, dst);
+                live.union_rows(/* read */ src, /* write */ head);
+                live.union_rows(/* read */ dst, /* write */ head);
             }
-            round_count += 1;
+        }
+        trace!(?merged_locals);
+        trace!(?relevant.renames);
 
-            apply_merges(body, tcx, merges, merged_locals);
+        if merged_locals.is_empty() {
+            return;
         }
 
-        trace!(round_count);
+        apply_merges(body, tcx, relevant, merged_locals);
     }
 
     fn is_required(&self) -> bool {
@@ -246,30 +246,6 @@ impl<'tcx> crate::MirPass<'tcx> for DestinationPropagation {
     }
 }
 
-#[derive(Debug, Default)]
-struct Candidates {
-    /// The set of candidates we are considering in this optimization.
-    ///
-    /// We will always merge the key into at most one of its values.
-    ///
-    /// Whether a place ends up in the key or the value does not correspond to whether it appears as
-    /// the lhs or rhs of any assignment. As a matter of fact, the places in here might never appear
-    /// in an assignment at all. This happens because if we see an assignment like this:
-    ///
-    /// ```ignore (syntax-highlighting-only)
-    /// _1.0 = _2.0
-    /// ```
-    ///
-    /// We will still report that we would like to merge `_1` and `_2` in an attempt to allow us to
-    /// remove that assignment.
-    c: FxIndexMap<Local, Vec<Local>>,
-
-    /// A reverse index of the `c` set; if the `c` set contains `a => Place { local: b, proj }`,
-    /// then this contains `b => a`.
-    // PERF: Possibly these should be `SmallVec`s?
-    reverse: FxIndexMap<Local, Vec<Local>>,
-}
-
 //////////////////////////////////////////////////////////
 // Merging
 //
@@ -278,16 +254,16 @@ struct Candidates {
 fn apply_merges<'tcx>(
     body: &mut Body<'tcx>,
     tcx: TyCtxt<'tcx>,
-    merges: FxIndexMap<Local, Local>,
+    relevant: RelevantLocals,
     merged_locals: DenseBitSet<Local>,
 ) {
-    let mut merger = Merger { tcx, merges, merged_locals };
+    let mut merger = Merger { tcx, relevant, merged_locals };
     merger.visit_body_preserves_cfg(body);
 }
 
 struct Merger<'tcx> {
     tcx: TyCtxt<'tcx>,
-    merges: FxIndexMap<Local, Local>,
+    relevant: RelevantLocals,
     merged_locals: DenseBitSet<Local>,
 }
 
@@ -297,8 +273,8 @@ impl<'tcx> MutVisitor<'tcx> for Merger<'tcx> {
     }
 
     fn visit_local(&mut self, local: &mut Local, _: PlaceContext, _location: Location) {
-        if let Some(dest) = self.merges.get(local) {
-            *local = *dest;
+        if let Some(relevant) = self.relevant.find(*local) {
+            *local = self.relevant.original[relevant];
         }
     }
 
@@ -336,414 +312,95 @@ impl<'tcx> MutVisitor<'tcx> for Merger<'tcx> {
 }
 
 //////////////////////////////////////////////////////////
-// Liveness filtering
+// Relevant locals
 //
-// This section enforces bullet point 2
+// Small utility to reduce size of the conflict matrix by only considering locals that appear in
+// the candidates
 
-struct FilterInformation<'a, 'tcx> {
-    body: &'a Body<'tcx>,
-    points: &'a DenseLocationMap,
-    live: &'a SparseIntervalMatrix<Local, PointIndex>,
-    candidates: &'a mut Candidates,
-    write_info: &'a mut WriteInfo,
-    at: Location,
+newtype_index! {
+    /// Represent a subset of locals which appear in candidates.
+    struct RelevantLocal {}
 }
 
-// We first implement some utility functions which we will expose removing candidates according to
-// different needs. Throughout the liveness filtering, the `candidates` are only ever accessed
-// through these methods, and not directly.
-impl Candidates {
-    /// Collects the candidates for merging.
-    ///
-    /// This is responsible for enforcing the first and third bullet point.
-    fn reset_and_find<'tcx>(&mut self, body: &Body<'tcx>, borrowed: &DenseBitSet<Local>) {
-        self.c.clear();
-        self.reverse.clear();
-        let mut visitor = FindAssignments { body, candidates: &mut self.c, borrowed };
-        visitor.visit_body(body);
-        // Deduplicate candidates.
-        for (_, cands) in self.c.iter_mut() {
-            cands.sort();
-            cands.dedup();
-        }
-        // Generate the reverse map.
-        for (src, cands) in self.c.iter() {
-            for dest in cands.iter().copied() {
-                self.reverse.entry(dest).or_default().push(*src);
-            }
-        }
-    }
-
-    /// Just `Vec::retain`, but the condition is inverted and we add debugging output
-    fn vec_filter_candidates(
-        src: Local,
-        v: &mut Vec<Local>,
-        mut f: impl FnMut(Local) -> CandidateFilter,
-        at: Location,
-    ) {
-        v.retain(|dest| {
-            let remove = f(*dest);
-            if remove == CandidateFilter::Remove {
-                trace!("eliminating {:?} => {:?} due to conflict at {:?}", src, dest, at);
-            }
-            remove == CandidateFilter::Keep
-        });
-    }
-
-    /// `vec_filter_candidates` but for an `Entry`
-    fn entry_filter_candidates(
-        mut entry: IndexOccupiedEntry<'_, Local, Vec<Local>>,
-        p: Local,
-        f: impl FnMut(Local) -> CandidateFilter,
-        at: Location,
-    ) {
-        let candidates = entry.get_mut();
-        Self::vec_filter_candidates(p, candidates, f, at);
-        if candidates.len() == 0 {
-            // FIXME(#120456) - is `swap_remove` correct?
-            entry.swap_remove();
-        }
-    }
-
-    /// For all candidates `(p, q)` or `(q, p)` removes the candidate if `f(q)` says to do so
-    fn filter_candidates_by(
-        &mut self,
-        p: Local,
-        mut f: impl FnMut(Local) -> CandidateFilter,
-        at: Location,
-    ) {
-        // Cover the cases where `p` appears as a `src`
-        if let IndexEntry::Occupied(entry) = self.c.entry(p) {
-            Self::entry_filter_candidates(entry, p, &mut f, at);
-        }
-        // And the cases where `p` appears as a `dest`
-        let Some(srcs) = self.reverse.get_mut(&p) else {
-            return;
-        };
-        // We use `retain` here to remove the elements from the reverse set if we've removed the
-        // matching candidate in the forward set.
-        srcs.retain(|src| {
-            if f(*src) == CandidateFilter::Keep {
-                return true;
-            }
-            let IndexEntry::Occupied(entry) = self.c.entry(*src) else {
-                return false;
-            };
-            Self::entry_filter_candidates(
-                entry,
-                *src,
-                |dest| {
-                    if dest == p { CandidateFilter::Remove } else { CandidateFilter::Keep }
-                },
-                at,
-            );
-            false
-        });
-    }
+#[derive(Debug)]
+struct RelevantLocals {
+    original: IndexVec<RelevantLocal, Local>,
+    shrink: IndexVec<Local, Option<RelevantLocal>>,
+    renames: UnionFind<RelevantLocal>,
 }
 
-#[derive(Copy, Clone, PartialEq, Eq)]
-enum CandidateFilter {
-    Keep,
-    Remove,
-}
+impl RelevantLocals {
+    #[tracing::instrument(level = "trace", skip(candidates, num_locals), ret)]
+    fn compute(candidates: &Candidates, num_locals: usize) -> RelevantLocals {
+        let mut original = IndexVec::with_capacity(candidates.c.len());
+        let mut shrink = IndexVec::from_elem_n(None, num_locals);
 
-impl<'a, 'tcx> FilterInformation<'a, 'tcx> {
-    /// Filters the set of candidates to remove those that conflict.
-    ///
-    /// The steps we take are exactly those that are outlined at the top of the file. For each
-    /// statement/terminator, we collect the set of locals that are written to in that
-    /// statement/terminator, and then we remove all pairs of candidates that contain one such local
-    /// and another one that is live.
-    ///
-    /// We need to be careful about the ordering of operations within each statement/terminator
-    /// here. Many statements might write and read from more than one place, and we need to consider
-    /// them all. The strategy for doing this is as follows: We first gather all the places that are
-    /// written to within the statement/terminator via `WriteInfo`. Then, we use the liveness
-    /// analysis from *before* the statement/terminator (in the control flow sense) to eliminate
-    /// candidates - this is because we want to conservatively treat a pair of locals that is both
-    /// read and written in the statement/terminator to be conflicting, and the liveness analysis
-    /// before the statement/terminator will correctly report locals that are read in the
-    /// statement/terminator to be live. We are additionally conservative by treating all written to
-    /// locals as also being read from.
-    fn filter_liveness(
-        candidates: &mut Candidates,
-        points: &DenseLocationMap,
-        live: &SparseIntervalMatrix<Local, PointIndex>,
-        write_info: &mut WriteInfo,
-        body: &Body<'tcx>,
-    ) {
-        let mut this = FilterInformation {
-            body,
-            points,
-            live,
-            candidates,
-            // We don't actually store anything at this scope, we just keep things here to be able
-            // to reuse the allocation.
-            write_info,
-            // Doesn't matter what we put here, will be overwritten before being used
-            at: Location::START,
+        // Mark a local as relevant and record it into the maps.
+        let mut declare = |local| {
+            shrink.get_or_insert_with(local, || original.push(local));
         };
-        this.internal_filter_liveness();
-    }
 
-    fn internal_filter_liveness(&mut self) {
-        for (block, data) in traversal::preorder(self.body) {
-            self.at = Location { block, statement_index: data.statements.len() };
-            self.write_info.for_terminator(&data.terminator().kind);
-            self.apply_conflicts();
-
-            for (i, statement) in data.statements.iter().enumerate().rev() {
-                self.at = Location { block, statement_index: i };
-                self.write_info.for_statement(&statement.kind, self.body);
-                self.apply_conflicts();
-            }
+        for &(src, dest) in candidates.c.iter() {
+            declare(src);
+            declare(dest)
         }
-    }
 
-    fn apply_conflicts(&mut self) {
-        let writes = &self.write_info.writes;
-        for p in writes {
-            let other_skip = self.write_info.skip_pair.and_then(|(a, b)| {
-                if a == *p {
-                    Some(b)
-                } else if b == *p {
-                    Some(a)
-                } else {
-                    None
-                }
-            });
-            let at = self.points.point_from_location(self.at);
-            self.candidates.filter_candidates_by(
-                *p,
-                |q| {
-                    if Some(q) == other_skip {
-                        return CandidateFilter::Keep;
-                    }
-                    // It is possible that a local may be live for less than the
-                    // duration of a statement This happens in the case of function
-                    // calls or inline asm. Because of this, we also mark locals as
-                    // conflicting when both of them are written to in the same
-                    // statement.
-                    if self.live.contains(q, at) || writes.contains(&q) {
-                        CandidateFilter::Remove
-                    } else {
-                        CandidateFilter::Keep
-                    }
-                },
-                self.at,
-            );
-        }
+        let renames = UnionFind::new(original.len());
+        RelevantLocals { original, shrink, renames }
     }
-}
 
-/// Describes where a statement/terminator writes to
-#[derive(Default, Debug)]
-struct WriteInfo {
-    writes: Vec<Local>,
-    /// If this pair of locals is a candidate pair, completely skip processing it during this
-    /// statement. All other candidates are unaffected.
-    skip_pair: Option<(Local, Local)>,
-}
-
-impl WriteInfo {
-    fn for_statement<'tcx>(&mut self, statement: &StatementKind<'tcx>, body: &Body<'tcx>) {
-        self.reset();
-        match statement {
-            StatementKind::Assign(box (lhs, rhs)) => {
-                self.add_place(*lhs);
-                match rhs {
-                    Rvalue::Use(op) => {
-                        self.add_operand(op);
-                        self.consider_skipping_for_assign_use(*lhs, op, body);
-                    }
-                    Rvalue::Repeat(op, _) => {
-                        self.add_operand(op);
-                    }
-                    Rvalue::Cast(_, op, _)
-                    | Rvalue::UnaryOp(_, op)
-                    | Rvalue::ShallowInitBox(op, _) => {
-                        self.add_operand(op);
-                    }
-                    Rvalue::BinaryOp(_, ops) => {
-                        for op in [&ops.0, &ops.1] {
-                            self.add_operand(op);
-                        }
-                    }
-                    Rvalue::Aggregate(_, ops) => {
-                        for op in ops {
-                            self.add_operand(op);
-                        }
-                    }
-                    Rvalue::WrapUnsafeBinder(op, _) => {
-                        self.add_operand(op);
-                    }
-                    Rvalue::ThreadLocalRef(_)
-                    | Rvalue::NullaryOp(_, _)
-                    | Rvalue::Ref(_, _, _)
-                    | Rvalue::RawPtr(_, _)
-                    | Rvalue::Len(_)
-                    | Rvalue::Discriminant(_)
-                    | Rvalue::CopyForDeref(_) => {}
-                }
-            }
-            // Retags are technically also reads, but reporting them as a write suffices
-            StatementKind::SetDiscriminant { place, .. }
-            | StatementKind::Deinit(place)
-            | StatementKind::Retag(_, place) => {
-                self.add_place(**place);
-            }
-            StatementKind::Intrinsic(_)
-            | StatementKind::ConstEvalCounter
-            | StatementKind::Nop
-            | StatementKind::Coverage(_)
-            | StatementKind::StorageLive(_)
-            | StatementKind::StorageDead(_)
-            | StatementKind::BackwardIncompatibleDropHint { .. }
-            | StatementKind::PlaceMention(_) => {}
-            StatementKind::FakeRead(_) | StatementKind::AscribeUserType(_, _) => {
-                bug!("{:?} not found in this MIR phase", statement)
-            }
-        }
+    fn find(&mut self, src: Local) -> Option<RelevantLocal> {
+        let src = self.shrink[src]?;
+        let src = self.renames.find(src);
+        Some(src)
     }
 
-    fn consider_skipping_for_assign_use<'tcx>(
-        &mut self,
-        lhs: Place<'tcx>,
-        rhs: &Operand<'tcx>,
-        body: &Body<'tcx>,
-    ) {
-        let Some(rhs) = rhs.place() else { return };
-        if let Some(pair) = places_to_candidate_pair(lhs, rhs, body) {
-            self.skip_pair = Some(pair);
-        }
-    }
-
-    fn for_terminator<'tcx>(&mut self, terminator: &TerminatorKind<'tcx>) {
-        self.reset();
-        match terminator {
-            TerminatorKind::SwitchInt { discr: op, .. }
-            | TerminatorKind::Assert { cond: op, .. } => {
-                self.add_operand(op);
-            }
-            TerminatorKind::Call { destination, func, args, .. } => {
-                self.add_place(*destination);
-                self.add_operand(func);
-                for arg in args {
-                    self.add_operand(&arg.node);
-                }
-            }
-            TerminatorKind::TailCall { func, args, .. } => {
-                self.add_operand(func);
-                for arg in args {
-                    self.add_operand(&arg.node);
-                }
-            }
-            TerminatorKind::InlineAsm { operands, .. } => {
-                for asm_operand in operands {
-                    match asm_operand {
-                        InlineAsmOperand::In { value, .. } => {
-                            self.add_operand(value);
-                        }
-                        InlineAsmOperand::Out { place, .. } => {
-                            if let Some(place) = place {
-                                self.add_place(*place);
-                            }
-                        }
-                        // Note that the `late` field in `InOut` is about whether the registers used
-                        // for these things overlap, and is of absolutely no interest to us.
-                        InlineAsmOperand::InOut { in_value, out_place, .. } => {
-                            if let Some(place) = out_place {
-                                self.add_place(*place);
-                            }
-                            self.add_operand(in_value);
-                        }
-                        InlineAsmOperand::Const { .. }
-                        | InlineAsmOperand::SymFn { .. }
-                        | InlineAsmOperand::SymStatic { .. }
-                        | InlineAsmOperand::Label { .. } => {}
-                    }
-                }
-            }
-            TerminatorKind::Goto { .. }
-            | TerminatorKind::UnwindResume
-            | TerminatorKind::UnwindTerminate(_)
-            | TerminatorKind::Return
-            | TerminatorKind::Unreachable { .. } => (),
-            TerminatorKind::Drop { .. } => {
-                // `Drop`s create a `&mut` and so are not considered
-            }
-            TerminatorKind::Yield { .. }
-            | TerminatorKind::CoroutineDrop
-            | TerminatorKind::FalseEdge { .. }
-            | TerminatorKind::FalseUnwind { .. } => {
-                bug!("{:?} not found in this MIR phase", terminator)
-            }
-        }
-    }
-
-    fn add_place(&mut self, place: Place<'_>) {
-        self.writes.push(place.local);
-    }
-
-    fn add_operand<'tcx>(&mut self, op: &Operand<'tcx>) {
-        match op {
-            // FIXME(JakobDegen): In a previous version, the `Move` case was incorrectly treated as
-            // being a read only. This was unsound, however we cannot add a regression test because
-            // it is not possible to set this off with current MIR. Once we have that ability, a
-            // regression test should be added.
-            Operand::Move(p) => self.add_place(*p),
-            Operand::Copy(_) | Operand::Constant(_) => (),
-        }
-    }
-
-    fn reset(&mut self) {
-        self.writes.clear();
-        self.skip_pair = None;
+    fn union(&mut self, lhs: RelevantLocal, rhs: RelevantLocal) -> RelevantLocal {
+        let head = self.renames.unify(lhs, rhs);
+        // We need to ensure we keep the original local of the RHS, as it may be a required local.
+        self.original[head] = self.original[rhs];
+        head
     }
 }
 
 /////////////////////////////////////////////////////
 // Candidate accumulation
 
-/// If the pair of places is being considered for merging, returns the candidate which would be
-/// merged in order to accomplish this.
-///
-/// The contract here is in one direction - there is a guarantee that merging the locals that are
-/// outputted by this function would result in an assignment between the inputs becoming a
-/// self-assignment. However, there is no guarantee that the returned pair is actually suitable for
-/// merging - candidate collection must still check this independently.
-///
-/// This output is unique for each unordered pair of input places.
-fn places_to_candidate_pair<'tcx>(
-    a: Place<'tcx>,
-    b: Place<'tcx>,
-    body: &Body<'tcx>,
-) -> Option<(Local, Local)> {
-    let (mut a, mut b) = if a.projection.len() == 0 && b.projection.len() == 0 {
-        (a.local, b.local)
-    } else {
-        return None;
-    };
+#[derive(Debug, Default)]
+struct Candidates {
+    /// The set of candidates we are considering in this optimization.
+    ///
+    /// Whether a place ends up in the key or the value does not correspond to whether it appears as
+    /// the lhs or rhs of any assignment. As a matter of fact, the places in here might never appear
+    /// in an assignment at all. This happens because if we see an assignment like this:
+    ///
+    /// ```ignore (syntax-highlighting-only)
+    /// _1.0 = _2.0
+    /// ```
+    ///
+    /// We will still report that we would like to merge `_1` and `_2` in an attempt to allow us to
+    /// remove that assignment.
+    c: Vec<(Local, Local)>,
+}
 
-    // By sorting, we make sure we're input order independent
-    if a > b {
-        std::mem::swap(&mut a, &mut b);
-    }
+// We first implement some utility functions which we will expose removing candidates according to
+// different needs. Throughout the liveness filtering, the `candidates` are only ever accessed
+// through these methods, and not directly.
+impl Candidates {
+    /// Collects the candidates for merging.
+    ///
+    /// This is responsible for enforcing the first and third bullet point.
+    fn find(body: &Body<'_>, borrowed: &DenseBitSet<Local>) -> Candidates {
+        let mut visitor = FindAssignments { body, candidates: Default::default(), borrowed };
+        visitor.visit_body(body);
 
-    // We could now return `(a, b)`, but then we miss some candidates in the case where `a` can't be
-    // used as a `src`.
-    if is_local_required(a, body) {
-        std::mem::swap(&mut a, &mut b);
+        Candidates { c: visitor.candidates }
     }
-    // We could check `is_local_required` again here, but there's no need - after all, we make no
-    // promise that the candidate pair is actually valid
-    Some((a, b))
 }
 
 struct FindAssignments<'a, 'tcx> {
     body: &'a Body<'tcx>,
-    candidates: &'a mut FxIndexMap<Local, Vec<Local>>,
+    candidates: Vec<(Local, Local)>,
     borrowed: &'a DenseBitSet<Local>,
 }
 
@@ -753,11 +410,9 @@ impl<'tcx> Visitor<'tcx> for FindAssignments<'_, 'tcx> {
             lhs,
             Rvalue::CopyForDeref(rhs) | Rvalue::Use(Operand::Copy(rhs) | Operand::Move(rhs)),
         )) = &statement.kind
+            && let Some(src) = lhs.as_local()
+            && let Some(dest) = rhs.as_local()
         {
-            let Some((src, dest)) = places_to_candidate_pair(*lhs, *rhs, self.body) else {
-                return;
-            };
-
             // As described at the top of the file, we do not go near things that have
             // their address taken.
             if self.borrowed.contains(src) || self.borrowed.contains(dest) {
@@ -774,13 +429,8 @@ impl<'tcx> Visitor<'tcx> for FindAssignments<'_, 'tcx> {
                 return;
             }
 
-            // Also, we need to make sure that MIR actually allows the `src` to be removed
-            if is_local_required(src, self.body) {
-                return;
-            }
-
             // We may insert duplicates here, but that's fine
-            self.candidates.entry(src).or_default().push(dest);
+            self.candidates.push((src, dest));
         }
     }
 }
@@ -803,22 +453,162 @@ fn dest_prop_mir_dump<'tcx>(
     tcx: TyCtxt<'tcx>,
     body: &Body<'tcx>,
     points: &DenseLocationMap,
-    live: &SparseIntervalMatrix<Local, PointIndex>,
-    round: usize,
+    live: &SparseIntervalMatrix<RelevantLocal, TwoStepIndex>,
+    relevant: &RelevantLocals,
 ) {
     let locals_live_at = |location| {
-        let location = points.point_from_location(location);
-        live.rows().filter(|&r| live.contains(r, location)).collect::<Vec<_>>()
+        live.rows()
+            .filter(|&r| live.contains(r, location))
+            .map(|rl| relevant.original[rl])
+            .collect::<Vec<_>>()
     };
 
     if let Some(dumper) = MirDumper::new(tcx, "DestinationPropagation-dataflow", body) {
         let extra_data = &|pass_where, w: &mut dyn std::io::Write| {
             if let PassWhere::BeforeLocation(loc) = pass_where {
-                writeln!(w, "        // live: {:?}", locals_live_at(loc))?;
+                let location = TwoStepIndex::new(points, loc, Effect::Before);
+                let live = locals_live_at(location);
+                writeln!(w, "        // before: {:?} => {:?}", location, live)?;
+            }
+            if let PassWhere::AfterLocation(loc) = pass_where {
+                let location = TwoStepIndex::new(points, loc, Effect::After);
+                let live = locals_live_at(location);
+                writeln!(w, "        // after: {:?} => {:?}", location, live)?;
             }
             Ok(())
         };
 
-        dumper.set_disambiguator(&round).set_extra_data(extra_data).dump_mir(body)
+        dumper.set_extra_data(extra_data).dump_mir(body)
     }
 }
+
+#[derive(Copy, Clone, Debug)]
+enum Effect {
+    Before,
+    After,
+}
+
+rustc_index::newtype_index! {
+    /// A reversed `PointIndex` but with the lower bit encoding early/late inside the statement.
+    /// The reversed order allows to use the more efficient `IntervalSet::append` method while we
+    /// iterate on the statements in reverse order.
+    #[orderable]
+    #[debug_format = "TwoStepIndex({})"]
+    struct TwoStepIndex {}
+}
+
+impl TwoStepIndex {
+    fn new(elements: &DenseLocationMap, location: Location, effect: Effect) -> TwoStepIndex {
+        let point = elements.point_from_location(location);
+        let effect = match effect {
+            Effect::Before => 0,
+            Effect::After => 1,
+        };
+        let max_index = 2 * elements.num_points() as u32 - 1;
+        let index = 2 * point.as_u32() + (effect as u32);
+        // Reverse the indexing to use more efficient `IntervalSet::append`.
+        TwoStepIndex::from_u32(max_index - index)
+    }
+}
+
+struct VisitPlacesWith<F>(F);
+
+impl<'tcx, F> Visitor<'tcx> for VisitPlacesWith<F>
+where
+    F: FnMut(Place<'tcx>, PlaceContext),
+{
+    fn visit_local(&mut self, local: Local, ctxt: PlaceContext, _: Location) {
+        (self.0)(local.into(), ctxt);
+    }
+
+    fn visit_place(&mut self, place: &Place<'tcx>, ctxt: PlaceContext, location: Location) {
+        (self.0)(*place, ctxt);
+        self.visit_projection(place.as_ref(), ctxt, location);
+    }
+}
+
+/// Add points depending on the result of the given dataflow analysis.
+fn save_as_intervals<'tcx>(
+    elements: &DenseLocationMap,
+    body: &Body<'tcx>,
+    relevant: &RelevantLocals,
+    results: Results<DenseBitSet<Local>>,
+) -> SparseIntervalMatrix<RelevantLocal, TwoStepIndex> {
+    let mut values = SparseIntervalMatrix::new(2 * elements.num_points());
+    let mut state = MaybeLiveLocals.bottom_value(body);
+    let reachable_blocks = traversal::reachable_as_bitset(body);
+
+    let two_step_loc = |location, effect| TwoStepIndex::new(elements, location, effect);
+    let append_at =
+        |values: &mut SparseIntervalMatrix<_, _>, state: &DenseBitSet<Local>, twostep| {
+            for (relevant, &original) in relevant.original.iter_enumerated() {
+                if state.contains(original) {
+                    values.append(relevant, twostep);
+                }
+            }
+        };
+
+    // Iterate blocks in decreasing order, to visit locations in decreasing order. This
+    // allows to use the more efficient `append` method to interval sets.
+    for block in body.basic_blocks.indices().rev() {
+        if !reachable_blocks.contains(block) {
+            continue;
+        }
+
+        state.clone_from(&results[block]);
+
+        let block_data = &body.basic_blocks[block];
+        let loc = Location { block, statement_index: block_data.statements.len() };
+
+        let term = block_data.terminator();
+        let mut twostep = two_step_loc(loc, Effect::After);
+        append_at(&mut values, &state, twostep);
+        // Ensure we have a non-zero live range even for dead stores. This is done by marking all
+        // the written-to locals as live in the second half of the statement.
+        // We also ensure that operands read by terminators conflict with writes by that terminator.
+        // For instance a function call may read args after having written to the destination.
+        VisitPlacesWith(|place, ctxt| match DefUse::for_place(place, ctxt) {
+            DefUse::Def | DefUse::Use | DefUse::PartialWrite => {
+                if let Some(relevant) = relevant.shrink[place.local] {
+                    values.insert(relevant, twostep);
+                }
+            }
+            DefUse::NonUse => {}
+        })
+        .visit_terminator(term, loc);
+
+        twostep = TwoStepIndex::from_u32(twostep.as_u32() + 1);
+        debug_assert_eq!(twostep, two_step_loc(loc, Effect::Before));
+        MaybeLiveLocals.apply_early_terminator_effect(&mut state, term, loc);
+        MaybeLiveLocals.apply_primary_terminator_effect(&mut state, term, loc);
+        append_at(&mut values, &state, twostep);
+
+        for (statement_index, stmt) in block_data.statements.iter().enumerate().rev() {
+            let loc = Location { block, statement_index };
+            twostep = TwoStepIndex::from_u32(twostep.as_u32() + 1);
+            debug_assert_eq!(twostep, two_step_loc(loc, Effect::After));
+            append_at(&mut values, &state, twostep);
+            // Ensure we have a non-zero live range even for dead stores. This is done by marking
+            // all the written-to locals as live in the second half of the statement.
+            VisitPlacesWith(|place, ctxt| match DefUse::for_place(place, ctxt) {
+                DefUse::Def | DefUse::PartialWrite => {
+                    if let Some(relevant) = relevant.shrink[place.local] {
+                        values.insert(relevant, twostep);
+                    }
+                }
+                DefUse::Use | DefUse::NonUse => {}
+            })
+            .visit_statement(stmt, loc);
+
+            twostep = TwoStepIndex::from_u32(twostep.as_u32() + 1);
+            debug_assert_eq!(twostep, two_step_loc(loc, Effect::Before));
+            MaybeLiveLocals.apply_early_statement_effect(&mut state, stmt, loc);
+            MaybeLiveLocals.apply_primary_statement_effect(&mut state, stmt, loc);
+            // ... but reads from operands are marked as live here so they do not conflict with
+            // the all the writes we manually marked as live in the second half of the statement.
+            append_at(&mut values, &state, twostep);
+        }
+    }
+
+    values
+}
diff --git a/compiler/rustc_mir_transform/src/errors.rs b/compiler/rustc_mir_transform/src/errors.rs
index ad9635aae33..775f5f9a7cf 100644
--- a/compiler/rustc_mir_transform/src/errors.rs
+++ b/compiler/rustc_mir_transform/src/errors.rs
@@ -2,6 +2,7 @@ use rustc_errors::codes::*;
 use rustc_errors::{Diag, LintDiagnostic};
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
 use rustc_middle::mir::AssertKind;
+use rustc_middle::query::Key;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::lint::{self, Lint};
 use rustc_span::def_id::DefId;
@@ -9,6 +10,46 @@ use rustc_span::{Ident, Span, Symbol};
 
 use crate::fluent_generated as fluent;
 
+/// Emit diagnostic for calls to `#[inline(always)]`-annotated functions with a
+/// `#[target_feature]` attribute where the caller enables a different set of target features.
+pub(crate) fn emit_inline_always_target_feature_diagnostic<'a, 'tcx>(
+    tcx: TyCtxt<'tcx>,
+    call_span: Span,
+    callee_def_id: DefId,
+    caller_def_id: DefId,
+    callee_only: &[&'a str],
+) {
+    let callee = tcx.def_path_str(callee_def_id);
+    let caller = tcx.def_path_str(caller_def_id);
+
+    tcx.node_span_lint(
+        lint::builtin::INLINE_ALWAYS_MISMATCHING_TARGET_FEATURES,
+        tcx.local_def_id_to_hir_id(caller_def_id.as_local().unwrap()),
+        call_span,
+        |lint| {
+            lint.primary_message(format!(
+                "call to `#[inline(always)]`-annotated `{callee}` \
+                requires the same target features to be inlined"
+            ));
+            lint.note("function will not be inlined");
+
+            lint.note(format!(
+                "the following target features are on `{callee}` but missing from `{caller}`: {}",
+                callee_only.join(", ")
+            ));
+            lint.span_note(callee_def_id.default_span(tcx), format!("`{callee}` is defined here"));
+
+            let feats = callee_only.join(",");
+            lint.span_suggestion(
+                tcx.def_span(caller_def_id).shrink_to_lo(),
+                format!("add `#[target_feature]` attribute to `{caller}`"),
+                format!("#[target_feature(enable = \"{feats}\")]\n"),
+                lint::Applicability::MaybeIncorrect,
+            );
+        },
+    );
+}
+
 #[derive(LintDiagnostic)]
 #[diag(mir_transform_unconditional_recursion)]
 #[help]
diff --git a/compiler/rustc_mir_transform/src/gvn.rs b/compiler/rustc_mir_transform/src/gvn.rs
index 5a13394543b..f867c130efb 100644
--- a/compiler/rustc_mir_transform/src/gvn.rs
+++ b/compiler/rustc_mir_transform/src/gvn.rs
@@ -87,6 +87,7 @@
 use std::borrow::Cow;
 
 use either::Either;
+use itertools::Itertools as _;
 use rustc_abi::{self as abi, BackendRepr, FIRST_VARIANT, FieldIdx, Primitive, Size, VariantIdx};
 use rustc_const_eval::const_eval::DummyMachine;
 use rustc_const_eval::interpret::{
@@ -895,18 +896,13 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
 
     fn simplify_aggregate_to_copy(
         &mut self,
-        lhs: &Place<'tcx>,
-        rvalue: &mut Rvalue<'tcx>,
-        location: Location,
-        fields: &[VnIndex],
+        ty: Ty<'tcx>,
         variant_index: VariantIdx,
+        fields: &[VnIndex],
     ) -> Option<VnIndex> {
-        let Some(&first_field) = fields.first() else {
-            return None;
-        };
-        let Value::Projection(copy_from_value, _) = *self.get(first_field) else {
-            return None;
-        };
+        let Some(&first_field) = fields.first() else { return None };
+        let Value::Projection(copy_from_value, _) = *self.get(first_field) else { return None };
+
         // All fields must correspond one-to-one and come from the same aggregate value.
         if fields.iter().enumerate().any(|(index, &v)| {
             if let Value::Projection(pointer, ProjectionElem::Field(from_index, _)) = *self.get(v)
@@ -933,21 +929,8 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
             }
         }
 
-        // Allow introducing places with non-constant offsets, as those are still better than
-        // reconstructing an aggregate.
-        if self.ty(copy_from_local_value) == rvalue.ty(self.local_decls, self.tcx)
-            && let Some(place) = self.try_as_place(copy_from_local_value, location, true)
-        {
-            // Avoid creating `*a = copy (*b)`, as they might be aliases resulting in overlapping assignments.
-            // FIXME: This also avoids any kind of projection, not just derefs. We can add allowed projections.
-            if lhs.as_local().is_some() {
-                self.reused_locals.insert(place.local);
-                *rvalue = Rvalue::Use(Operand::Copy(place));
-            }
-            return Some(copy_from_local_value);
-        }
-
-        None
+        // Both must be variants of the same type.
+        if self.ty(copy_from_local_value) == ty { Some(copy_from_local_value) } else { None }
     }
 
     fn simplify_aggregate(
@@ -1023,20 +1006,27 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
             }
         };
 
-        if ty.is_array() && fields.len() > 4 {
-            let first = fields[0];
-            if fields.iter().all(|&v| v == first) {
-                let len = ty::Const::from_target_usize(self.tcx, fields.len().try_into().unwrap());
-                if let Some(op) = self.try_as_operand(first, location) {
-                    *rvalue = Rvalue::Repeat(op, len);
-                }
-                return Some(self.insert(ty, Value::Repeat(first, len)));
+        if ty.is_array()
+            && fields.len() > 4
+            && let Ok(&first) = fields.iter().all_equal_value()
+        {
+            let len = ty::Const::from_target_usize(self.tcx, fields.len().try_into().unwrap());
+            if let Some(op) = self.try_as_operand(first, location) {
+                *rvalue = Rvalue::Repeat(op, len);
             }
+            return Some(self.insert(ty, Value::Repeat(first, len)));
         }
 
-        if let Some(value) =
-            self.simplify_aggregate_to_copy(lhs, rvalue, location, &fields, variant_index)
-        {
+        if let Some(value) = self.simplify_aggregate_to_copy(ty, variant_index, &fields) {
+            // Allow introducing places with non-constant offsets, as those are still better than
+            // reconstructing an aggregate. But avoid creating `*a = copy (*b)`, as they might be
+            // aliases resulting in overlapping assignments.
+            let allow_complex_projection =
+                lhs.projection[..].iter().all(PlaceElem::is_stable_offset);
+            if let Some(place) = self.try_as_place(value, location, allow_complex_projection) {
+                self.reused_locals.insert(place.local);
+                *rvalue = Rvalue::Use(Operand::Copy(place));
+            }
             return Some(value);
         }
 
diff --git a/compiler/rustc_mir_transform/src/lib.rs b/compiler/rustc_mir_transform/src/lib.rs
index 8f319e64916..1663dfa744f 100644
--- a/compiler/rustc_mir_transform/src/lib.rs
+++ b/compiler/rustc_mir_transform/src/lib.rs
@@ -117,6 +117,7 @@ declare_passes! {
     mod add_subtyping_projections : Subtyper;
     mod check_inline : CheckForceInline;
     mod check_call_recursion : CheckCallRecursion, CheckDropRecursion;
+    mod check_inline_always_target_features: CheckInlineAlwaysTargetFeature;
     mod check_alignment : CheckAlignment;
     mod check_enums : CheckEnums;
     mod check_const_item_mutation : CheckConstItemMutation;
@@ -384,6 +385,9 @@ fn mir_built(tcx: TyCtxt<'_>, def: LocalDefId) -> &Steal<Body<'_>> {
             // MIR-level lints.
             &Lint(check_inline::CheckForceInline),
             &Lint(check_call_recursion::CheckCallRecursion),
+            // Check callee's target features match callers target features when
+            // using `#[inline(always)]`
+            &Lint(check_inline_always_target_features::CheckInlineAlwaysTargetFeature),
             &Lint(check_packed_ref::CheckPackedRef),
             &Lint(check_const_item_mutation::CheckConstItemMutation),
             &Lint(function_item_references::FunctionItemReferences),
diff --git a/compiler/rustc_mir_transform/src/lint_tail_expr_drop_order.rs b/compiler/rustc_mir_transform/src/lint_tail_expr_drop_order.rs
index 794984d2f3e..61c9bbe3123 100644
--- a/compiler/rustc_mir_transform/src/lint_tail_expr_drop_order.rs
+++ b/compiler/rustc_mir_transform/src/lint_tail_expr_drop_order.rs
@@ -2,6 +2,7 @@ use std::cell::RefCell;
 use std::collections::hash_map;
 use std::rc::Rc;
 
+use itertools::Itertools as _;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
 use rustc_data_structures::unord::{UnordMap, UnordSet};
 use rustc_errors::Subdiagnostic;
@@ -339,9 +340,9 @@ pub(crate) fn run_lint<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId, body: &Body<
             // Suppose that all BIDs point into the same local,
             // we can remove the this local from the observed drops,
             // so that we can focus our diagnosis more on the others.
-            if candidates.iter().all(|&(_, place)| candidates[0].1.local == place.local) {
+            if let Ok(local) = candidates.iter().map(|&(_, place)| place.local).all_equal_value() {
                 for path_idx in all_locals_dropped.iter() {
-                    if move_data.move_paths[path_idx].place.local == candidates[0].1.local {
+                    if move_data.move_paths[path_idx].place.local == local {
                         to_exclude.insert(path_idx);
                     }
                 }
diff --git a/compiler/rustc_mir_transform/src/simplify.rs b/compiler/rustc_mir_transform/src/simplify.rs
index 468ef742dfb..75917d23883 100644
--- a/compiler/rustc_mir_transform/src/simplify.rs
+++ b/compiler/rustc_mir_transform/src/simplify.rs
@@ -34,6 +34,7 @@
 //! The normal logic that a program with UB can be changed to do anything does not apply to
 //! pre-"runtime" MIR!
 
+use itertools::Itertools as _;
 use rustc_index::{Idx, IndexSlice, IndexVec};
 use rustc_middle::mir::visit::{MutVisitor, MutatingUseContext, PlaceContext, Visitor};
 use rustc_middle::mir::*;
@@ -288,20 +289,13 @@ impl<'a, 'tcx> CfgSimplifier<'a, 'tcx> {
             return false;
         };
 
-        let first_succ = {
-            if let Some(first_succ) = terminator.successors().next() {
-                if terminator.successors().all(|s| s == first_succ) {
-                    let count = terminator.successors().count();
-                    self.pred_count[first_succ] -= (count - 1) as u32;
-                    first_succ
-                } else {
-                    return false;
-                }
-            } else {
-                return false;
-            }
+        let Ok(first_succ) = terminator.successors().all_equal_value() else {
+            return false;
         };
 
+        let count = terminator.successors().count();
+        self.pred_count[first_succ] -= (count - 1) as u32;
+
         debug!("simplifying branch {:?}", terminator);
         terminator.kind = TerminatorKind::Goto { target: first_succ };
         true
diff --git a/compiler/rustc_mir_transform/src/ssa.rs b/compiler/rustc_mir_transform/src/ssa.rs
index cd9a7f4a39d..73c249a3c8c 100644
--- a/compiler/rustc_mir_transform/src/ssa.rs
+++ b/compiler/rustc_mir_transform/src/ssa.rs
@@ -225,6 +225,9 @@ impl SsaVisitor<'_, '_> {
 
 impl<'tcx> Visitor<'tcx> for SsaVisitor<'_, 'tcx> {
     fn visit_local(&mut self, local: Local, ctxt: PlaceContext, loc: Location) {
+        if ctxt.may_observe_address() {
+            self.borrowed_locals.insert(local);
+        }
         match ctxt {
             PlaceContext::MutatingUse(MutatingUseContext::Projection)
             | PlaceContext::NonMutatingUse(NonMutatingUseContext::Projection) => bug!(),
@@ -237,7 +240,6 @@ impl<'tcx> Visitor<'tcx> for SsaVisitor<'_, 'tcx> {
             PlaceContext::NonMutatingUse(
                 NonMutatingUseContext::SharedBorrow | NonMutatingUseContext::FakeBorrow,
             ) => {
-                self.borrowed_locals.insert(local);
                 self.check_dominates(local, loc);
                 self.direct_uses[local] += 1;
             }
diff --git a/compiler/rustc_monomorphize/Cargo.toml b/compiler/rustc_monomorphize/Cargo.toml
index 78266d3c6d8..09a55f0b5f8 100644
--- a/compiler/rustc_monomorphize/Cargo.toml
+++ b/compiler/rustc_monomorphize/Cargo.toml
@@ -16,6 +16,6 @@ rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
 serde = "1"
-serde_json.workspace = true
-tracing.workspace = true
+serde_json = "1"
+tracing = "0.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_next_trait_solver/Cargo.toml b/compiler/rustc_next_trait_solver/Cargo.toml
index 43db90c08f3..05bcabad02f 100644
--- a/compiler/rustc_next_trait_solver/Cargo.toml
+++ b/compiler/rustc_next_trait_solver/Cargo.toml
@@ -5,13 +5,13 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-derive-where.workspace = true
+derive-where = "1.2.7"
 rustc_data_structures = { path = "../rustc_data_structures", optional = true }
 rustc_index = { path = "../rustc_index", default-features = false }
 rustc_macros = { path = "../rustc_macros", optional = true }
 rustc_type_ir = { path = "../rustc_type_ir", default-features = false }
 rustc_type_ir_macros = { path = "../rustc_type_ir_macros" }
-tracing.workspace = true
+tracing = "0.1"
 # tidy-alphabetical-end
 
 [features]
diff --git a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs
index 4644b145b18..6f9f4067384 100644
--- a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs
@@ -56,22 +56,23 @@ where
     ///
     /// This expects `goal` and `opaque_types` to be eager resolved.
     pub(super) fn canonicalize_goal(
-        &self,
+        delegate: &D,
         goal: Goal<I, I::Predicate>,
         opaque_types: Vec<(ty::OpaqueTypeKey<I>, I::Ty)>,
     ) -> (Vec<I::GenericArg>, CanonicalInput<I, I::Predicate>) {
         let mut orig_values = Default::default();
         let canonical = Canonicalizer::canonicalize_input(
-            self.delegate,
+            delegate,
             &mut orig_values,
             QueryInput {
                 goal,
-                predefined_opaques_in_body: self
+                predefined_opaques_in_body: delegate
                     .cx()
                     .mk_predefined_opaques_in_body(PredefinedOpaquesData { opaque_types }),
             },
         );
-        let query_input = ty::CanonicalQueryInput { canonical, typing_mode: self.typing_mode() };
+        let query_input =
+            ty::CanonicalQueryInput { canonical, typing_mode: delegate.typing_mode() };
         (orig_values, query_input)
     }
 
@@ -271,28 +272,23 @@ where
     /// - we apply the `external_constraints` returned by the query, returning
     ///   the `normalization_nested_goals`
     pub(super) fn instantiate_and_apply_query_response(
-        &mut self,
+        delegate: &D,
         param_env: I::ParamEnv,
         original_values: &[I::GenericArg],
         response: CanonicalResponse<I>,
+        span: I::Span,
     ) -> (NestedNormalizationGoals<I>, Certainty) {
         let instantiation = Self::compute_query_response_instantiation_values(
-            self.delegate,
+            delegate,
             &original_values,
             &response,
-            self.origin_span,
+            span,
         );
 
         let Response { var_values, external_constraints, certainty } =
-            self.delegate.instantiate_canonical(response, instantiation);
+            delegate.instantiate_canonical(response, instantiation);
 
-        Self::unify_query_var_values(
-            self.delegate,
-            param_env,
-            &original_values,
-            var_values,
-            self.origin_span,
-        );
+        Self::unify_query_var_values(delegate, param_env, &original_values, var_values, span);
 
         let ExternalConstraintsData {
             region_constraints,
@@ -300,8 +296,8 @@ where
             normalization_nested_goals,
         } = &*external_constraints;
 
-        self.register_region_constraints(region_constraints);
-        self.register_new_opaque_types(opaque_types);
+        Self::register_region_constraints(delegate, region_constraints, span);
+        Self::register_new_opaque_types(delegate, opaque_types, span);
 
         (normalization_nested_goals.clone(), certainty)
     }
@@ -424,21 +420,26 @@ where
     }
 
     fn register_region_constraints(
-        &mut self,
+        delegate: &D,
         outlives: &[ty::OutlivesPredicate<I, I::GenericArg>],
+        span: I::Span,
     ) {
         for &ty::OutlivesPredicate(lhs, rhs) in outlives {
             match lhs.kind() {
-                ty::GenericArgKind::Lifetime(lhs) => self.register_region_outlives(lhs, rhs),
-                ty::GenericArgKind::Type(lhs) => self.register_ty_outlives(lhs, rhs),
+                ty::GenericArgKind::Lifetime(lhs) => delegate.sub_regions(rhs, lhs, span),
+                ty::GenericArgKind::Type(lhs) => delegate.register_ty_outlives(lhs, rhs, span),
                 ty::GenericArgKind::Const(_) => panic!("const outlives: {lhs:?}: {rhs:?}"),
             }
         }
     }
 
-    fn register_new_opaque_types(&mut self, opaque_types: &[(ty::OpaqueTypeKey<I>, I::Ty)]) {
+    fn register_new_opaque_types(
+        delegate: &D,
+        opaque_types: &[(ty::OpaqueTypeKey<I>, I::Ty)],
+        span: I::Span,
+    ) {
         for &(key, ty) in opaque_types {
-            let prev = self.delegate.register_hidden_type_in_storage(key, ty, self.origin_span);
+            let prev = delegate.register_hidden_type_in_storage(key, ty, span);
             // We eagerly resolve inference variables when computing the query response.
             // This can cause previously distinct opaque type keys to now be structurally equal.
             //
@@ -447,7 +448,7 @@ where
             // types here. However, doing so is difficult as it may result in nested goals and
             // any errors may make it harder to track the control flow for diagnostics.
             if let Some(prev) = prev {
-                self.delegate.add_duplicate_opaque_type(key, prev, self.origin_span);
+                delegate.add_duplicate_opaque_type(key, prev, span);
             }
         }
     }
diff --git a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs
index 606fbcab4b3..99aa9bef5ac 100644
--- a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs
@@ -20,13 +20,12 @@ use crate::coherence;
 use crate::delegate::SolverDelegate;
 use crate::placeholder::BoundVarReplacer;
 use crate::resolve::eager_resolve_vars;
-use crate::solve::inspect::{self, ProofTreeBuilder};
 use crate::solve::search_graph::SearchGraph;
 use crate::solve::ty::may_use_unstable_feature;
 use crate::solve::{
-    CanonicalInput, Certainty, FIXPOINT_STEP_LIMIT, Goal, GoalEvaluation, GoalEvaluationKind,
-    GoalSource, GoalStalledOn, HasChanged, NestedNormalizationGoals, NoSolution, QueryInput,
-    QueryResult,
+    CanonicalInput, Certainty, FIXPOINT_STEP_LIMIT, Goal, GoalEvaluation, GoalSource,
+    GoalStalledOn, HasChanged, NestedNormalizationGoals, NoSolution, QueryInput, QueryResult,
+    inspect,
 };
 
 pub(super) mod canonical;
@@ -130,7 +129,7 @@ where
     // evaluation code.
     tainted: Result<(), NoSolution>,
 
-    pub(super) inspect: ProofTreeBuilder<D>,
+    pub(super) inspect: inspect::EvaluationStepBuilder<D>,
 }
 
 #[derive(PartialEq, Eq, Debug, Hash, Clone, Copy)]
@@ -172,10 +171,7 @@ pub trait SolverDelegateEvalExt: SolverDelegate {
         goal: Goal<Self::Interner, <Self::Interner as Interner>::Predicate>,
         span: <Self::Interner as Interner>::Span,
     ) -> (
-        Result<
-            (NestedNormalizationGoals<Self::Interner>, GoalEvaluation<Self::Interner>),
-            NoSolution,
-        >,
+        Result<NestedNormalizationGoals<Self::Interner>, NoSolution>,
         inspect::GoalEvaluation<Self::Interner>,
     );
 }
@@ -192,14 +188,9 @@ where
         span: I::Span,
         stalled_on: Option<GoalStalledOn<I>>,
     ) -> Result<GoalEvaluation<I>, NoSolution> {
-        EvalCtxt::enter_root(
-            self,
-            self.cx().recursion_limit(),
-            GenerateProofTree::No,
-            span,
-            |ecx| ecx.evaluate_goal(GoalEvaluationKind::Root, GoalSource::Misc, goal, stalled_on),
-        )
-        .0
+        EvalCtxt::enter_root(self, self.cx().recursion_limit(), span, |ecx| {
+            ecx.evaluate_goal(GoalSource::Misc, goal, stalled_on)
+        })
     }
 
     fn root_goal_may_hold_with_depth(
@@ -208,10 +199,9 @@ where
         goal: Goal<Self::Interner, <Self::Interner as Interner>::Predicate>,
     ) -> bool {
         self.probe(|| {
-            EvalCtxt::enter_root(self, root_depth, GenerateProofTree::No, I::Span::dummy(), |ecx| {
-                ecx.evaluate_goal(GoalEvaluationKind::Root, GoalSource::Misc, goal, None)
+            EvalCtxt::enter_root(self, root_depth, I::Span::dummy(), |ecx| {
+                ecx.evaluate_goal(GoalSource::Misc, goal, None)
             })
-            .0
         })
         .is_ok()
     }
@@ -221,18 +211,8 @@ where
         &self,
         goal: Goal<I, I::Predicate>,
         span: I::Span,
-    ) -> (
-        Result<(NestedNormalizationGoals<I>, GoalEvaluation<I>), NoSolution>,
-        inspect::GoalEvaluation<I>,
-    ) {
-        let (result, proof_tree) = EvalCtxt::enter_root(
-            self,
-            self.cx().recursion_limit(),
-            GenerateProofTree::Yes,
-            span,
-            |ecx| ecx.evaluate_goal_raw(GoalEvaluationKind::Root, GoalSource::Misc, goal, None),
-        );
-        (result, proof_tree.unwrap())
+    ) -> (Result<NestedNormalizationGoals<I>, NoSolution>, inspect::GoalEvaluation<I>) {
+        evaluate_root_goal_for_proof_tree(self, goal, span)
     }
 }
 
@@ -301,17 +281,16 @@ where
     pub(super) fn enter_root<R>(
         delegate: &D,
         root_depth: usize,
-        generate_proof_tree: GenerateProofTree,
         origin_span: I::Span,
         f: impl FnOnce(&mut EvalCtxt<'_, D>) -> R,
-    ) -> (R, Option<inspect::GoalEvaluation<I>>) {
+    ) -> R {
         let mut search_graph = SearchGraph::new(root_depth);
 
         let mut ecx = EvalCtxt {
             delegate,
             search_graph: &mut search_graph,
             nested_goals: Default::default(),
-            inspect: ProofTreeBuilder::new_maybe_root(generate_proof_tree),
+            inspect: inspect::EvaluationStepBuilder::new_noop(),
 
             // Only relevant when canonicalizing the response,
             // which we don't do within this evaluation context.
@@ -324,15 +303,12 @@ where
             tainted: Ok(()),
         };
         let result = f(&mut ecx);
-
-        let proof_tree = ecx.inspect.finalize();
         assert!(
             ecx.nested_goals.is_empty(),
             "root `EvalCtxt` should not have any goals added to it"
         );
-
         assert!(search_graph.is_empty());
-        (result, proof_tree)
+        result
     }
 
     /// Creates a nested evaluation context that shares the same search graph as the
@@ -346,11 +322,10 @@ where
         cx: I,
         search_graph: &'a mut SearchGraph<D>,
         canonical_input: CanonicalInput<I>,
-        canonical_goal_evaluation: &mut ProofTreeBuilder<D>,
+        proof_tree_builder: &mut inspect::ProofTreeBuilder<D>,
         f: impl FnOnce(&mut EvalCtxt<'_, D>, Goal<I, I::Predicate>) -> R,
     ) -> R {
         let (ref delegate, input, var_values) = D::build_with_canonical(cx, &canonical_input);
-
         for &(key, ty) in &input.predefined_opaques_in_body.opaque_types {
             let prev = delegate.register_hidden_type_in_storage(key, ty, I::Span::dummy());
             // It may be possible that two entries in the opaque type storage end up
@@ -381,12 +356,12 @@ where
             nested_goals: Default::default(),
             origin_span: I::Span::dummy(),
             tainted: Ok(()),
-            inspect: canonical_goal_evaluation.new_goal_evaluation_step(var_values),
+            inspect: proof_tree_builder.new_evaluation_step(var_values),
         };
 
         let result = f(&mut ecx, input.goal);
         ecx.inspect.probe_final_state(ecx.delegate, ecx.max_input_universe);
-        canonical_goal_evaluation.goal_evaluation_step(ecx.inspect);
+        proof_tree_builder.finish_evaluation_step(ecx.inspect);
 
         // When creating a query response we clone the opaque type constraints
         // instead of taking them. This would cause an ICE here, since we have
@@ -406,13 +381,12 @@ where
     /// been constrained and the certainty of the result.
     fn evaluate_goal(
         &mut self,
-        goal_evaluation_kind: GoalEvaluationKind,
         source: GoalSource,
         goal: Goal<I, I::Predicate>,
         stalled_on: Option<GoalStalledOn<I>>,
     ) -> Result<GoalEvaluation<I>, NoSolution> {
         let (normalization_nested_goals, goal_evaluation) =
-            self.evaluate_goal_raw(goal_evaluation_kind, source, goal, stalled_on)?;
+            self.evaluate_goal_raw(source, goal, stalled_on)?;
         assert!(normalization_nested_goals.is_empty());
         Ok(goal_evaluation)
     }
@@ -426,7 +400,6 @@ where
     /// storage.
     pub(super) fn evaluate_goal_raw(
         &mut self,
-        goal_evaluation_kind: GoalEvaluationKind,
         source: GoalSource,
         goal: Goal<I, I::Predicate>,
         stalled_on: Option<GoalStalledOn<I>>,
@@ -458,17 +431,14 @@ where
         let opaque_types = self.delegate.clone_opaque_types_lookup_table();
         let (goal, opaque_types) = eager_resolve_vars(self.delegate, (goal, opaque_types));
 
-        let (orig_values, canonical_goal) = self.canonicalize_goal(goal, opaque_types);
-        let mut goal_evaluation =
-            self.inspect.new_goal_evaluation(goal, &orig_values, goal_evaluation_kind);
+        let (orig_values, canonical_goal) =
+            Self::canonicalize_goal(self.delegate, goal, opaque_types);
         let canonical_result = self.search_graph.evaluate_goal(
             self.cx(),
             canonical_goal,
             self.step_kind_for_source(source),
-            &mut goal_evaluation,
+            &mut inspect::ProofTreeBuilder::new_noop(),
         );
-        goal_evaluation.query_result(canonical_result);
-        self.inspect.goal_evaluation(goal_evaluation);
         let response = match canonical_result {
             Err(e) => return Err(e),
             Ok(response) => response,
@@ -477,8 +447,13 @@ where
         let has_changed =
             if !has_only_region_constraints(response) { HasChanged::Yes } else { HasChanged::No };
 
-        let (normalization_nested_goals, certainty) =
-            self.instantiate_and_apply_query_response(goal.param_env, &orig_values, response);
+        let (normalization_nested_goals, certainty) = Self::instantiate_and_apply_query_response(
+            self.delegate,
+            goal.param_env,
+            &orig_values,
+            response,
+            self.origin_span,
+        );
 
         // FIXME: We previously had an assert here that checked that recomputing
         // a goal after applying its constraints did not change its response.
@@ -676,12 +651,7 @@ where
                 let (
                     NestedNormalizationGoals(nested_goals),
                     GoalEvaluation { goal, certainty, stalled_on, has_changed: _ },
-                ) = self.evaluate_goal_raw(
-                    GoalEvaluationKind::Nested,
-                    source,
-                    unconstrained_goal,
-                    stalled_on,
-                )?;
+                ) = self.evaluate_goal_raw(source, unconstrained_goal, stalled_on)?;
                 // Add the nested goals from normalization to our own nested goals.
                 trace!(?nested_goals);
                 self.nested_goals.extend(nested_goals.into_iter().map(|(s, g)| (s, g, None)));
@@ -734,7 +704,7 @@ where
                 }
             } else {
                 let GoalEvaluation { goal, certainty, has_changed, stalled_on } =
-                    self.evaluate_goal(GoalEvaluationKind::Nested, source, goal, stalled_on)?;
+                    self.evaluate_goal(source, goal, stalled_on)?;
                 if has_changed == HasChanged::Yes {
                     unchanged_certainty = None;
                 }
@@ -1297,3 +1267,62 @@ where
         if predicate.allow_normalization() { predicate.super_fold_with(self) } else { predicate }
     }
 }
+
+/// Do not call this directly, use the `tcx` query instead.
+pub fn evaluate_root_goal_for_proof_tree_raw_provider<
+    D: SolverDelegate<Interner = I>,
+    I: Interner,
+>(
+    cx: I,
+    canonical_goal: CanonicalInput<I>,
+) -> (QueryResult<I>, I::Probe) {
+    let mut inspect = inspect::ProofTreeBuilder::new();
+    let canonical_result = SearchGraph::<D>::evaluate_root_goal_for_proof_tree(
+        cx,
+        cx.recursion_limit(),
+        canonical_goal,
+        &mut inspect,
+    );
+    let final_revision = inspect.unwrap();
+    (canonical_result, cx.mk_probe(final_revision))
+}
+
+/// Evaluate a goal to build a proof tree.
+///
+/// This is a copy of [EvalCtxt::evaluate_goal_raw] which avoids relying on the
+/// [EvalCtxt] and uses a separate cache.
+pub(super) fn evaluate_root_goal_for_proof_tree<D: SolverDelegate<Interner = I>, I: Interner>(
+    delegate: &D,
+    goal: Goal<I, I::Predicate>,
+    origin_span: I::Span,
+) -> (Result<NestedNormalizationGoals<I>, NoSolution>, inspect::GoalEvaluation<I>) {
+    let opaque_types = delegate.clone_opaque_types_lookup_table();
+    let (goal, opaque_types) = eager_resolve_vars(delegate, (goal, opaque_types));
+
+    let (orig_values, canonical_goal) = EvalCtxt::canonicalize_goal(delegate, goal, opaque_types);
+
+    let (canonical_result, final_revision) =
+        delegate.cx().evaluate_root_goal_for_proof_tree_raw(canonical_goal);
+
+    let proof_tree = inspect::GoalEvaluation {
+        uncanonicalized_goal: goal,
+        orig_values,
+        final_revision,
+        result: canonical_result,
+    };
+
+    let response = match canonical_result {
+        Err(e) => return (Err(e), proof_tree),
+        Ok(response) => response,
+    };
+
+    let (normalization_nested_goals, _certainty) = EvalCtxt::instantiate_and_apply_query_response(
+        delegate,
+        goal.param_env,
+        &proof_tree.orig_values,
+        response,
+        origin_span,
+    );
+
+    (Ok(normalization_nested_goals), proof_tree)
+}
diff --git a/compiler/rustc_next_trait_solver/src/solve/inspect/build.rs b/compiler/rustc_next_trait_solver/src/solve/inspect/build.rs
index fc56b006d94..2675ed0d0da 100644
--- a/compiler/rustc_next_trait_solver/src/solve/inspect/build.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/inspect/build.rs
@@ -12,96 +12,86 @@ use rustc_type_ir::{self as ty, Interner};
 
 use crate::delegate::SolverDelegate;
 use crate::solve::eval_ctxt::canonical;
-use crate::solve::{
-    Certainty, GenerateProofTree, Goal, GoalEvaluationKind, GoalSource, QueryResult, inspect,
-};
+use crate::solve::{Certainty, Goal, GoalSource, QueryResult, inspect};
 
-/// The core data structure when building proof trees.
+/// We need to know whether to build a prove tree while evaluating. We
+/// pass a `ProofTreeBuilder` with `state: Some(None)` into the search
+/// graph which then causes the initial `EvalCtxt::compute_goal` to actually
+/// build a proof tree which then gets written into the `state`.
 ///
-/// In case the current evaluation does not generate a proof
-/// tree, `state` is simply `None` and we avoid any work.
-///
-/// The possible states of the solver are represented via
-/// variants of [DebugSolver]. For any nested computation we call
-/// `ProofTreeBuilder::new_nested_computation_kind` which
-/// creates a new `ProofTreeBuilder` to temporarily replace the
-/// current one. Once that nested computation is done,
-/// `ProofTreeBuilder::nested_computation_kind` is called
-/// to add the finished nested evaluation to the parent.
-///
-/// We provide additional information to the current state
-/// by calling methods such as `ProofTreeBuilder::probe_kind`.
-///
-/// The actual structure closely mirrors the finished proof
-/// trees. At the end of trait solving `ProofTreeBuilder::finalize`
-/// is called to recursively convert the whole structure to a
-/// finished proof tree.
+/// Building the proof tree for a single evaluation step happens via the
+/// [EvaluationStepBuilder] which is updated by the `EvalCtxt` when
+/// appropriate.
 pub(crate) struct ProofTreeBuilder<D, I = <D as SolverDelegate>::Interner>
 where
     D: SolverDelegate<Interner = I>,
     I: Interner,
 {
+    state: Option<Box<Option<inspect::Probe<I>>>>,
     _infcx: PhantomData<D>,
-    state: Option<Box<DebugSolver<I>>>,
 }
 
-/// The current state of the proof tree builder, at most places
-/// in the code, only one or two variants are actually possible.
-///
-/// We simply ICE in case that assumption is broken.
-#[derive_where(Debug; I: Interner)]
-enum DebugSolver<I: Interner> {
-    Root,
-    GoalEvaluation(WipGoalEvaluation<I>),
-    CanonicalGoalEvaluationStep(WipCanonicalGoalEvaluationStep<I>),
-}
+impl<D: SolverDelegate<Interner = I>, I: Interner> ProofTreeBuilder<D> {
+    pub(crate) fn new() -> ProofTreeBuilder<D> {
+        ProofTreeBuilder { state: Some(Box::new(None)), _infcx: PhantomData }
+    }
 
-impl<I: Interner> From<WipGoalEvaluation<I>> for DebugSolver<I> {
-    fn from(g: WipGoalEvaluation<I>) -> DebugSolver<I> {
-        DebugSolver::GoalEvaluation(g)
+    pub(crate) fn new_noop() -> ProofTreeBuilder<D> {
+        ProofTreeBuilder { state: None, _infcx: PhantomData }
     }
-}
 
-impl<I: Interner> From<WipCanonicalGoalEvaluationStep<I>> for DebugSolver<I> {
-    fn from(g: WipCanonicalGoalEvaluationStep<I>) -> DebugSolver<I> {
-        DebugSolver::CanonicalGoalEvaluationStep(g)
+    pub(crate) fn is_noop(&self) -> bool {
+        self.state.is_none()
     }
-}
 
-#[derive_where(PartialEq, Debug; I: Interner)]
-struct WipGoalEvaluation<I: Interner> {
-    pub uncanonicalized_goal: Goal<I, I::Predicate>,
-    pub orig_values: Vec<I::GenericArg>,
-    pub encountered_overflow: bool,
-    /// After we finished evaluating this is moved into `kind`.
-    pub final_revision: Option<WipCanonicalGoalEvaluationStep<I>>,
-    pub result: Option<QueryResult<I>>,
-}
+    pub(crate) fn new_evaluation_step(
+        &mut self,
+        var_values: ty::CanonicalVarValues<I>,
+    ) -> EvaluationStepBuilder<D> {
+        if self.is_noop() {
+            EvaluationStepBuilder { state: None, _infcx: PhantomData }
+        } else {
+            EvaluationStepBuilder {
+                state: Some(Box::new(WipEvaluationStep {
+                    var_values: var_values.var_values.to_vec(),
+                    evaluation: WipProbe {
+                        initial_num_var_values: var_values.len(),
+                        steps: vec![],
+                        kind: None,
+                        final_state: None,
+                    },
+                    probe_depth: 0,
+                })),
+                _infcx: PhantomData,
+            }
+        }
+    }
 
-impl<I: Interner> Eq for WipGoalEvaluation<I> {}
-
-impl<I: Interner> WipGoalEvaluation<I> {
-    fn finalize(self) -> inspect::GoalEvaluation<I> {
-        inspect::GoalEvaluation {
-            uncanonicalized_goal: self.uncanonicalized_goal,
-            orig_values: self.orig_values,
-            kind: if self.encountered_overflow {
-                assert!(self.final_revision.is_none());
-                inspect::GoalEvaluationKind::Overflow
-            } else {
-                let final_revision = self.final_revision.unwrap().finalize();
-                inspect::GoalEvaluationKind::Evaluation { final_revision }
-            },
-            result: self.result.unwrap(),
+    pub(crate) fn finish_evaluation_step(
+        &mut self,
+        goal_evaluation_step: EvaluationStepBuilder<D>,
+    ) {
+        if let Some(this) = self.state.as_deref_mut() {
+            *this = Some(goal_evaluation_step.state.unwrap().finalize());
         }
     }
+
+    pub(crate) fn unwrap(self) -> inspect::Probe<I> {
+        self.state.unwrap().unwrap()
+    }
 }
 
-/// This only exists during proof tree building and does not have
-/// a corresponding struct in `inspect`. We need this to track a
-/// bunch of metadata about the current evaluation.
-#[derive_where(PartialEq, Debug; I: Interner)]
-struct WipCanonicalGoalEvaluationStep<I: Interner> {
+pub(crate) struct EvaluationStepBuilder<D, I = <D as SolverDelegate>::Interner>
+where
+    D: SolverDelegate<Interner = I>,
+    I: Interner,
+{
+    state: Option<Box<WipEvaluationStep<I>>>,
+    _infcx: PhantomData<D>,
+}
+
+#[derive_where(PartialEq, Eq, Debug; I: Interner)]
+struct WipEvaluationStep<I: Interner> {
     /// Unlike `EvalCtxt::var_values`, we append a new
     /// generic arg here whenever we create a new inference
     /// variable.
@@ -113,9 +103,7 @@ struct WipCanonicalGoalEvaluationStep<I: Interner> {
     evaluation: WipProbe<I>,
 }
 
-impl<I: Interner> Eq for WipCanonicalGoalEvaluationStep<I> {}
-
-impl<I: Interner> WipCanonicalGoalEvaluationStep<I> {
+impl<I: Interner> WipEvaluationStep<I> {
     fn current_evaluation_scope(&mut self) -> &mut WipProbe<I> {
         let mut current = &mut self.evaluation;
         for _ in 0..self.probe_depth {
@@ -181,169 +169,48 @@ impl<I: Interner> WipProbeStep<I> {
     }
 }
 
-impl<D: SolverDelegate<Interner = I>, I: Interner> ProofTreeBuilder<D> {
-    fn new(state: impl Into<DebugSolver<I>>) -> ProofTreeBuilder<D> {
-        ProofTreeBuilder { state: Some(Box::new(state.into())), _infcx: PhantomData }
-    }
-
-    fn opt_nested<T: Into<DebugSolver<I>>>(&self, state: impl FnOnce() -> Option<T>) -> Self {
-        ProofTreeBuilder {
-            state: self.state.as_ref().and_then(|_| Some(state()?.into())).map(Box::new),
-            _infcx: PhantomData,
-        }
+impl<D: SolverDelegate<Interner = I>, I: Interner> EvaluationStepBuilder<D> {
+    pub(crate) fn new_noop() -> EvaluationStepBuilder<D> {
+        EvaluationStepBuilder { state: None, _infcx: PhantomData }
     }
 
-    fn nested<T: Into<DebugSolver<I>>>(&self, state: impl FnOnce() -> T) -> Self {
-        ProofTreeBuilder {
-            state: self.state.as_ref().map(|_| Box::new(state().into())),
-            _infcx: PhantomData,
-        }
+    pub(crate) fn is_noop(&self) -> bool {
+        self.state.is_none()
     }
 
-    fn as_mut(&mut self) -> Option<&mut DebugSolver<I>> {
+    fn as_mut(&mut self) -> Option<&mut WipEvaluationStep<I>> {
         self.state.as_deref_mut()
     }
 
-    pub(crate) fn take_and_enter_probe(&mut self) -> ProofTreeBuilder<D> {
-        let mut nested = ProofTreeBuilder { state: self.state.take(), _infcx: PhantomData };
+    pub(crate) fn take_and_enter_probe(&mut self) -> EvaluationStepBuilder<D> {
+        let mut nested = EvaluationStepBuilder { state: self.state.take(), _infcx: PhantomData };
         nested.enter_probe();
         nested
     }
 
-    pub(crate) fn finalize(self) -> Option<inspect::GoalEvaluation<I>> {
-        match *self.state? {
-            DebugSolver::GoalEvaluation(wip_goal_evaluation) => {
-                Some(wip_goal_evaluation.finalize())
-            }
-            root => unreachable!("unexpected proof tree builder root node: {:?}", root),
-        }
-    }
-
-    pub(crate) fn new_maybe_root(generate_proof_tree: GenerateProofTree) -> ProofTreeBuilder<D> {
-        match generate_proof_tree {
-            GenerateProofTree::No => ProofTreeBuilder::new_noop(),
-            GenerateProofTree::Yes => ProofTreeBuilder::new_root(),
-        }
-    }
-
-    fn new_root() -> ProofTreeBuilder<D> {
-        ProofTreeBuilder::new(DebugSolver::Root)
-    }
-
-    fn new_noop() -> ProofTreeBuilder<D> {
-        ProofTreeBuilder { state: None, _infcx: PhantomData }
-    }
-
-    pub(crate) fn is_noop(&self) -> bool {
-        self.state.is_none()
-    }
-
-    pub(in crate::solve) fn new_goal_evaluation(
-        &mut self,
-        uncanonicalized_goal: Goal<I, I::Predicate>,
-        orig_values: &[I::GenericArg],
-        kind: GoalEvaluationKind,
-    ) -> ProofTreeBuilder<D> {
-        self.opt_nested(|| match kind {
-            GoalEvaluationKind::Root => Some(WipGoalEvaluation {
-                uncanonicalized_goal,
-                orig_values: orig_values.to_vec(),
-                encountered_overflow: false,
-                final_revision: None,
-                result: None,
-            }),
-            GoalEvaluationKind::Nested => None,
-        })
-    }
-
-    pub(crate) fn canonical_goal_evaluation_overflow(&mut self) {
+    pub(crate) fn add_var_value<T: Into<I::GenericArg>>(&mut self, arg: T) {
         if let Some(this) = self.as_mut() {
-            match this {
-                DebugSolver::GoalEvaluation(goal_evaluation) => {
-                    goal_evaluation.encountered_overflow = true;
-                }
-                _ => unreachable!(),
-            };
+            this.var_values.push(arg.into());
         }
     }
 
-    pub(crate) fn goal_evaluation(&mut self, goal_evaluation: ProofTreeBuilder<D>) {
+    fn enter_probe(&mut self) {
         if let Some(this) = self.as_mut() {
-            match this {
-                DebugSolver::Root => *this = *goal_evaluation.state.unwrap(),
-                DebugSolver::CanonicalGoalEvaluationStep(_) => {
-                    assert!(goal_evaluation.state.is_none())
-                }
-                _ => unreachable!(),
-            }
-        }
-    }
-
-    pub(crate) fn new_goal_evaluation_step(
-        &mut self,
-        var_values: ty::CanonicalVarValues<I>,
-    ) -> ProofTreeBuilder<D> {
-        self.nested(|| WipCanonicalGoalEvaluationStep {
-            var_values: var_values.var_values.to_vec(),
-            evaluation: WipProbe {
-                initial_num_var_values: var_values.len(),
+            let initial_num_var_values = this.var_values.len();
+            this.current_evaluation_scope().steps.push(WipProbeStep::NestedProbe(WipProbe {
+                initial_num_var_values,
                 steps: vec![],
                 kind: None,
                 final_state: None,
-            },
-            probe_depth: 0,
-        })
-    }
-
-    pub(crate) fn goal_evaluation_step(&mut self, goal_evaluation_step: ProofTreeBuilder<D>) {
-        if let Some(this) = self.as_mut() {
-            match (this, *goal_evaluation_step.state.unwrap()) {
-                (
-                    DebugSolver::GoalEvaluation(goal_evaluation),
-                    DebugSolver::CanonicalGoalEvaluationStep(goal_evaluation_step),
-                ) => {
-                    goal_evaluation.final_revision = Some(goal_evaluation_step);
-                }
-                _ => unreachable!(),
-            }
-        }
-    }
-
-    pub(crate) fn add_var_value<T: Into<I::GenericArg>>(&mut self, arg: T) {
-        match self.as_mut() {
-            None => {}
-            Some(DebugSolver::CanonicalGoalEvaluationStep(state)) => {
-                state.var_values.push(arg.into());
-            }
-            Some(s) => panic!("tried to add var values to {s:?}"),
-        }
-    }
-
-    fn enter_probe(&mut self) {
-        match self.as_mut() {
-            None => {}
-            Some(DebugSolver::CanonicalGoalEvaluationStep(state)) => {
-                let initial_num_var_values = state.var_values.len();
-                state.current_evaluation_scope().steps.push(WipProbeStep::NestedProbe(WipProbe {
-                    initial_num_var_values,
-                    steps: vec![],
-                    kind: None,
-                    final_state: None,
-                }));
-                state.probe_depth += 1;
-            }
-            Some(s) => panic!("tried to start probe to {s:?}"),
+            }));
+            this.probe_depth += 1;
         }
     }
 
     pub(crate) fn probe_kind(&mut self, probe_kind: inspect::ProbeKind<I>) {
-        match self.as_mut() {
-            None => {}
-            Some(DebugSolver::CanonicalGoalEvaluationStep(state)) => {
-                let prev = state.current_evaluation_scope().kind.replace(probe_kind);
-                assert_eq!(prev, None);
-            }
-            _ => panic!(),
+        if let Some(this) = self.as_mut() {
+            let prev = this.current_evaluation_scope().kind.replace(probe_kind);
+            assert_eq!(prev, None);
         }
     }
 
@@ -352,19 +219,11 @@ impl<D: SolverDelegate<Interner = I>, I: Interner> ProofTreeBuilder<D> {
         delegate: &D,
         max_input_universe: ty::UniverseIndex,
     ) {
-        match self.as_mut() {
-            None => {}
-            Some(DebugSolver::CanonicalGoalEvaluationStep(state)) => {
-                let final_state = canonical::make_canonical_state(
-                    delegate,
-                    &state.var_values,
-                    max_input_universe,
-                    (),
-                );
-                let prev = state.current_evaluation_scope().final_state.replace(final_state);
-                assert_eq!(prev, None);
-            }
-            _ => panic!(),
+        if let Some(this) = self.as_mut() {
+            let final_state =
+                canonical::make_canonical_state(delegate, &this.var_values, max_input_universe, ());
+            let prev = this.current_evaluation_scope().final_state.replace(final_state);
+            assert_eq!(prev, None);
         }
     }
 
@@ -375,18 +234,14 @@ impl<D: SolverDelegate<Interner = I>, I: Interner> ProofTreeBuilder<D> {
         source: GoalSource,
         goal: Goal<I, I::Predicate>,
     ) {
-        match self.as_mut() {
-            None => {}
-            Some(DebugSolver::CanonicalGoalEvaluationStep(state)) => {
-                let goal = canonical::make_canonical_state(
-                    delegate,
-                    &state.var_values,
-                    max_input_universe,
-                    goal,
-                );
-                state.current_evaluation_scope().steps.push(WipProbeStep::AddGoal(source, goal))
-            }
-            _ => panic!(),
+        if let Some(this) = self.as_mut() {
+            let goal = canonical::make_canonical_state(
+                delegate,
+                &this.var_values,
+                max_input_universe,
+                goal,
+            );
+            this.current_evaluation_scope().steps.push(WipProbeStep::AddGoal(source, goal))
         }
     }
 
@@ -396,47 +251,31 @@ impl<D: SolverDelegate<Interner = I>, I: Interner> ProofTreeBuilder<D> {
         max_input_universe: ty::UniverseIndex,
         impl_args: I::GenericArgs,
     ) {
-        match self.as_mut() {
-            Some(DebugSolver::CanonicalGoalEvaluationStep(state)) => {
-                let impl_args = canonical::make_canonical_state(
-                    delegate,
-                    &state.var_values,
-                    max_input_universe,
-                    impl_args,
-                );
-                state
-                    .current_evaluation_scope()
-                    .steps
-                    .push(WipProbeStep::RecordImplArgs { impl_args });
-            }
-            None => {}
-            _ => panic!(),
+        if let Some(this) = self.as_mut() {
+            let impl_args = canonical::make_canonical_state(
+                delegate,
+                &this.var_values,
+                max_input_universe,
+                impl_args,
+            );
+            this.current_evaluation_scope().steps.push(WipProbeStep::RecordImplArgs { impl_args });
         }
     }
 
     pub(crate) fn make_canonical_response(&mut self, shallow_certainty: Certainty) {
-        match self.as_mut() {
-            Some(DebugSolver::CanonicalGoalEvaluationStep(state)) => {
-                state
-                    .current_evaluation_scope()
-                    .steps
-                    .push(WipProbeStep::MakeCanonicalResponse { shallow_certainty });
-            }
-            None => {}
-            _ => panic!(),
+        if let Some(this) = self.as_mut() {
+            this.current_evaluation_scope()
+                .steps
+                .push(WipProbeStep::MakeCanonicalResponse { shallow_certainty });
         }
     }
 
-    pub(crate) fn finish_probe(mut self) -> ProofTreeBuilder<D> {
-        match self.as_mut() {
-            None => {}
-            Some(DebugSolver::CanonicalGoalEvaluationStep(state)) => {
-                assert_ne!(state.probe_depth, 0);
-                let num_var_values = state.current_evaluation_scope().initial_num_var_values;
-                state.var_values.truncate(num_var_values);
-                state.probe_depth -= 1;
-            }
-            _ => panic!(),
+    pub(crate) fn finish_probe(mut self) -> EvaluationStepBuilder<D> {
+        if let Some(this) = self.as_mut() {
+            assert_ne!(this.probe_depth, 0);
+            let num_var_values = this.current_evaluation_scope().initial_num_var_values;
+            this.var_values.truncate(num_var_values);
+            this.probe_depth -= 1;
         }
 
         self
@@ -444,21 +283,7 @@ impl<D: SolverDelegate<Interner = I>, I: Interner> ProofTreeBuilder<D> {
 
     pub(crate) fn query_result(&mut self, result: QueryResult<I>) {
         if let Some(this) = self.as_mut() {
-            match this {
-                DebugSolver::GoalEvaluation(goal_evaluation) => {
-                    assert_eq!(goal_evaluation.result.replace(result), None);
-                }
-                DebugSolver::CanonicalGoalEvaluationStep(evaluation_step) => {
-                    assert_eq!(
-                        evaluation_step
-                            .evaluation
-                            .kind
-                            .replace(inspect::ProbeKind::Root { result }),
-                        None
-                    );
-                }
-                _ => unreachable!(),
-            }
+            assert_eq!(this.evaluation.kind.replace(inspect::ProbeKind::Root { result }), None);
         }
     }
 }
diff --git a/compiler/rustc_next_trait_solver/src/solve/mod.rs b/compiler/rustc_next_trait_solver/src/solve/mod.rs
index 710b59f662a..85f9d852d95 100644
--- a/compiler/rustc_next_trait_solver/src/solve/mod.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/mod.rs
@@ -27,7 +27,10 @@ pub use rustc_type_ir::solve::*;
 use rustc_type_ir::{self as ty, Interner, TypingMode};
 use tracing::instrument;
 
-pub use self::eval_ctxt::{EvalCtxt, GenerateProofTree, SolverDelegateEvalExt};
+pub use self::eval_ctxt::{
+    EvalCtxt, GenerateProofTree, SolverDelegateEvalExt,
+    evaluate_root_goal_for_proof_tree_raw_provider,
+};
 use crate::delegate::SolverDelegate;
 use crate::solve::assembly::Candidate;
 
@@ -42,12 +45,6 @@ use crate::solve::assembly::Candidate;
 /// recursion limit again. However, this feels very unlikely.
 const FIXPOINT_STEP_LIMIT: usize = 8;
 
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
-enum GoalEvaluationKind {
-    Root,
-    Nested,
-}
-
 /// Whether evaluating this goal ended up changing the
 /// inference state.
 #[derive(PartialEq, Eq, Debug, Hash, Clone, Copy)]
diff --git a/compiler/rustc_next_trait_solver/src/solve/search_graph.rs b/compiler/rustc_next_trait_solver/src/solve/search_graph.rs
index 84f8eda4f8d..f0342e0523f 100644
--- a/compiler/rustc_next_trait_solver/src/solve/search_graph.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/search_graph.rs
@@ -7,8 +7,9 @@ use rustc_type_ir::solve::{CanonicalInput, Certainty, NoSolution, QueryResult};
 use rustc_type_ir::{Interner, TypingMode};
 
 use crate::delegate::SolverDelegate;
-use crate::solve::inspect::ProofTreeBuilder;
-use crate::solve::{EvalCtxt, FIXPOINT_STEP_LIMIT, has_no_inference_or_external_constraints};
+use crate::solve::{
+    EvalCtxt, FIXPOINT_STEP_LIMIT, has_no_inference_or_external_constraints, inspect,
+};
 
 /// This type is never constructed. We only use it to implement `search_graph::Delegate`
 /// for all types which impl `SolverDelegate` and doing it directly fails in coherence.
@@ -34,7 +35,7 @@ where
 
     const FIXPOINT_STEP_LIMIT: usize = FIXPOINT_STEP_LIMIT;
 
-    type ProofTreeBuilder = ProofTreeBuilder<D>;
+    type ProofTreeBuilder = inspect::ProofTreeBuilder<D>;
     fn inspect_is_noop(inspect: &mut Self::ProofTreeBuilder) -> bool {
         inspect.is_noop()
     }
@@ -81,12 +82,7 @@ where
         Self::initial_provisional_result(cx, kind, input) == result
     }
 
-    fn on_stack_overflow(
-        cx: I,
-        input: CanonicalInput<I>,
-        inspect: &mut ProofTreeBuilder<D>,
-    ) -> QueryResult<I> {
-        inspect.canonical_goal_evaluation_overflow();
+    fn on_stack_overflow(cx: I, input: CanonicalInput<I>) -> QueryResult<I> {
         response_no_constraints(cx, input, Certainty::overflow(true))
     }
 
diff --git a/compiler/rustc_parse/Cargo.toml b/compiler/rustc_parse/Cargo.toml
index 7cb4ae7ff5f..6d738a10371 100644
--- a/compiler/rustc_parse/Cargo.toml
+++ b/compiler/rustc_parse/Cargo.toml
@@ -5,8 +5,8 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-bitflags.workspace = true
-rustc-literal-escaper.workspace = true
+bitflags = "2.4.1"
+rustc-literal-escaper = "0.0.5"
 rustc_ast = { path = "../rustc_ast" }
 rustc_ast_pretty = { path = "../rustc_ast_pretty" }
 rustc_data_structures = { path = "../rustc_data_structures" }
@@ -18,8 +18,8 @@ rustc_lexer = { path = "../rustc_lexer" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
-thin-vec.workspace = true
-tracing.workspace = true
+thin-vec = "0.2.12"
+tracing = "0.1"
 unicode-normalization = "0.1.11"
 unicode-width = "0.2.0"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_parse/messages.ftl b/compiler/rustc_parse/messages.ftl
index 4ca2f57bd87..77dd313d9b8 100644
--- a/compiler/rustc_parse/messages.ftl
+++ b/compiler/rustc_parse/messages.ftl
@@ -58,7 +58,7 @@ parse_async_use_order_incorrect = the order of `use` and `async` is incorrect
 parse_at_dot_dot_in_struct_pattern = `@ ..` is not supported in struct patterns
     .suggestion = bind to each field separately or, if you don't need them, just remove `{$ident} @`
 
-parse_at_in_struct_pattern = Unexpected `@` in struct pattern
+parse_at_in_struct_pattern = unexpected `@` in struct pattern
     .note = struct patterns use `field: pattern` syntax to bind to fields
     .help = consider replacing `new_name @ field_name` with `field_name: new_name` if that is what you intended
 
diff --git a/compiler/rustc_parse/src/lexer/mod.rs b/compiler/rustc_parse/src/lexer/mod.rs
index 9792240a548..f5f081efc49 100644
--- a/compiler/rustc_parse/src/lexer/mod.rs
+++ b/compiler/rustc_parse/src/lexer/mod.rs
@@ -6,7 +6,7 @@ use rustc_ast::util::unicode::{TEXT_FLOW_CONTROL_CHARS, contains_text_flow_contr
 use rustc_errors::codes::*;
 use rustc_errors::{Applicability, Diag, DiagCtxtHandle, StashKey};
 use rustc_lexer::{
-    Base, Cursor, DocStyle, FrontmatterAllowed, LiteralKind, RawStrError, is_whitespace,
+    Base, Cursor, DocStyle, FrontmatterAllowed, LiteralKind, RawStrError, is_horizontal_whitespace,
 };
 use rustc_literal_escaper::{EscapeError, Mode, check_for_errors};
 use rustc_session::lint::BuiltinLintDiag;
@@ -44,19 +44,44 @@ pub(crate) struct UnmatchedDelim {
     pub candidate_span: Option<Span>,
 }
 
+/// Which tokens should be stripped before lexing the tokens.
+pub(crate) enum StripTokens {
+    /// Strip both shebang and frontmatter.
+    ShebangAndFrontmatter,
+    /// Strip the shebang but not frontmatter.
+    ///
+    /// That means that char sequences looking like frontmatter are simply
+    /// interpreted as regular Rust lexemes.
+    Shebang,
+    /// Strip nothing.
+    ///
+    /// In other words, char sequences looking like a shebang or frontmatter
+    /// are simply interpreted as regular Rust lexemes.
+    Nothing,
+}
+
 pub(crate) fn lex_token_trees<'psess, 'src>(
     psess: &'psess ParseSess,
     mut src: &'src str,
     mut start_pos: BytePos,
     override_span: Option<Span>,
-    frontmatter_allowed: FrontmatterAllowed,
+    strip_tokens: StripTokens,
 ) -> Result<TokenStream, Vec<Diag<'psess>>> {
-    // Skip `#!`, if present.
-    if let Some(shebang_len) = rustc_lexer::strip_shebang(src) {
-        src = &src[shebang_len..];
-        start_pos = start_pos + BytePos::from_usize(shebang_len);
+    match strip_tokens {
+        StripTokens::Shebang | StripTokens::ShebangAndFrontmatter => {
+            if let Some(shebang_len) = rustc_lexer::strip_shebang(src) {
+                src = &src[shebang_len..];
+                start_pos = start_pos + BytePos::from_usize(shebang_len);
+            }
+        }
+        StripTokens::Nothing => {}
     }
 
+    let frontmatter_allowed = match strip_tokens {
+        StripTokens::ShebangAndFrontmatter => FrontmatterAllowed::Yes,
+        StripTokens::Shebang | StripTokens::Nothing => FrontmatterAllowed::No,
+    };
+
     let cursor = Cursor::new(src, frontmatter_allowed);
     let mut lexer = Lexer {
         psess,
@@ -597,7 +622,7 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
 
         let last_line_start = within.rfind('\n').map_or(0, |i| i + 1);
         let last_line = &within[last_line_start..];
-        let last_line_trimmed = last_line.trim_start_matches(is_whitespace);
+        let last_line_trimmed = last_line.trim_start_matches(is_horizontal_whitespace);
         let last_line_start_pos = frontmatter_opening_end_pos + BytePos(last_line_start as u32);
 
         let frontmatter_span = self.mk_sp(frontmatter_opening_pos, self.pos);
@@ -640,7 +665,7 @@ impl<'psess, 'src> Lexer<'psess, 'src> {
             });
         }
 
-        if !rest.trim_matches(is_whitespace).is_empty() {
+        if !rest.trim_matches(is_horizontal_whitespace).is_empty() {
             let span = self.mk_sp(last_line_start_pos, self.pos);
             self.dcx().emit_err(errors::FrontmatterExtraCharactersAfterClose { span });
         }
diff --git a/compiler/rustc_parse/src/lib.rs b/compiler/rustc_parse/src/lib.rs
index 197333d942d..d8792d7af4c 100644
--- a/compiler/rustc_parse/src/lib.rs
+++ b/compiler/rustc_parse/src/lib.rs
@@ -21,7 +21,6 @@ use rustc_ast::tokenstream::{DelimSpan, TokenStream};
 use rustc_ast::{AttrItem, Attribute, MetaItemInner, token};
 use rustc_ast_pretty::pprust;
 use rustc_errors::{Diag, EmissionGuarantee, FatalError, PResult, pluralize};
-use rustc_lexer::FrontmatterAllowed;
 use rustc_session::parse::ParseSess;
 use rustc_span::source_map::SourceMap;
 use rustc_span::{FileName, SourceFile, Span};
@@ -34,6 +33,8 @@ pub mod parser;
 use parser::Parser;
 use rustc_ast::token::Delimiter;
 
+use crate::lexer::StripTokens;
+
 pub mod lexer;
 
 mod errors;
@@ -62,7 +63,20 @@ pub fn new_parser_from_source_str(
     source: String,
 ) -> Result<Parser<'_>, Vec<Diag<'_>>> {
     let source_file = psess.source_map().new_source_file(name, source);
-    new_parser_from_source_file(psess, source_file)
+    new_parser_from_source_file(psess, source_file, StripTokens::ShebangAndFrontmatter)
+}
+
+/// Creates a new parser from a simple (no shebang, no frontmatter) source string.
+///
+/// On failure, the errors must be consumed via `unwrap_or_emit_fatal`, `emit`, `cancel`,
+/// etc., otherwise a panic will occur when they are dropped.
+pub fn new_parser_from_simple_source_str(
+    psess: &ParseSess,
+    name: FileName,
+    source: String,
+) -> Result<Parser<'_>, Vec<Diag<'_>>> {
+    let source_file = psess.source_map().new_source_file(name, source);
+    new_parser_from_source_file(psess, source_file, StripTokens::Nothing)
 }
 
 /// Creates a new parser from a filename. On failure, the errors must be consumed via
@@ -96,7 +110,7 @@ pub fn new_parser_from_file<'a>(
         }
         err.emit();
     });
-    new_parser_from_source_file(psess, source_file)
+    new_parser_from_source_file(psess, source_file, StripTokens::ShebangAndFrontmatter)
 }
 
 pub fn utf8_error<E: EmissionGuarantee>(
@@ -147,9 +161,10 @@ pub fn utf8_error<E: EmissionGuarantee>(
 fn new_parser_from_source_file(
     psess: &ParseSess,
     source_file: Arc<SourceFile>,
+    strip_tokens: StripTokens,
 ) -> Result<Parser<'_>, Vec<Diag<'_>>> {
     let end_pos = source_file.end_position();
-    let stream = source_file_to_stream(psess, source_file, None, FrontmatterAllowed::Yes)?;
+    let stream = source_file_to_stream(psess, source_file, None, strip_tokens)?;
     let mut parser = Parser::new(psess, stream, None);
     if parser.token == token::Eof {
         parser.token.span = Span::new(end_pos, end_pos, parser.token.span.ctxt(), None);
@@ -165,8 +180,8 @@ pub fn source_str_to_stream(
 ) -> Result<TokenStream, Vec<Diag<'_>>> {
     let source_file = psess.source_map().new_source_file(name, source);
     // used mainly for `proc_macro` and the likes, not for our parsing purposes, so don't parse
-    // frontmatters as frontmatters.
-    source_file_to_stream(psess, source_file, override_span, FrontmatterAllowed::No)
+    // frontmatters as frontmatters, but for compatibility reason still strip the shebang
+    source_file_to_stream(psess, source_file, override_span, StripTokens::Shebang)
 }
 
 /// Given a source file, produces a sequence of token trees. Returns any buffered errors from
@@ -175,7 +190,7 @@ fn source_file_to_stream<'psess>(
     psess: &'psess ParseSess,
     source_file: Arc<SourceFile>,
     override_span: Option<Span>,
-    frontmatter_allowed: FrontmatterAllowed,
+    strip_tokens: StripTokens,
 ) -> Result<TokenStream, Vec<Diag<'psess>>> {
     let src = source_file.src.as_ref().unwrap_or_else(|| {
         psess.dcx().bug(format!(
@@ -184,13 +199,7 @@ fn source_file_to_stream<'psess>(
         ));
     });
 
-    lexer::lex_token_trees(
-        psess,
-        src.as_str(),
-        source_file.start_pos,
-        override_span,
-        frontmatter_allowed,
-    )
+    lexer::lex_token_trees(psess, src.as_str(), source_file.start_pos, override_span, strip_tokens)
 }
 
 /// Runs the given subparser `f` on the tokens of the given `attr`'s item.
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index 7de4f6efd0b..4c02547357e 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -2742,7 +2742,7 @@ impl<'a> Parser<'a> {
     /// The specified `edition` in `let_chains_policy` should be that of the whole `if` construct,
     /// i.e. the same span we use to later decide whether the drop behaviour should be that of
     /// edition `..=2021` or that of `2024..`.
-    // Public because it is used in rustfmt forks such as https://github.com/tucant/rustfmt/blob/30c83df9e1db10007bdd16dafce8a86b404329b2/src/parse/macros/html.rs#L57 for custom if expressions.
+    // Public to use it for custom `if` expressions in rustfmt forks like https://github.com/tucant/rustfmt
     pub fn parse_expr_cond(
         &mut self,
         let_chains_policy: LetChainsPolicy,
@@ -2910,7 +2910,8 @@ impl<'a> Parser<'a> {
         }
     }
 
-    fn parse_for_head(&mut self) -> PResult<'a, (Box<Pat>, Box<Expr>)> {
+    // Public to use it for custom `for` expressions in rustfmt forks like https://github.com/tucant/rustfmt
+    pub fn parse_for_head(&mut self) -> PResult<'a, (Box<Pat>, Box<Expr>)> {
         let begin_paren = if self.token == token::OpenParen {
             // Record whether we are about to parse `for (`.
             // This is used below for recovery in case of `for ( $stuff ) $block`
diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs
index 15598f32429..3bbca622975 100644
--- a/compiler/rustc_parse/src/parser/mod.rs
+++ b/compiler/rustc_parse/src/parser/mod.rs
@@ -22,6 +22,8 @@ use std::{fmt, mem, slice};
 use attr_wrapper::{AttrWrapper, UsePreAttrPos};
 pub use diagnostics::AttemptLocalParseRecovery;
 pub(crate) use expr::ForbiddenLetReason;
+// Public to use it for custom `if` expressions in rustfmt forks like https://github.com/tucant/rustfmt
+pub use expr::LetChainsPolicy;
 pub(crate) use item::{FnContext, FnParseMode};
 pub use pat::{CommaRecoveryMode, RecoverColon, RecoverComma};
 pub use path::PathStyle;
diff --git a/compiler/rustc_parse/src/parser/pat.rs b/compiler/rustc_parse/src/parser/pat.rs
index 9754691a0b9..c4d30b3d328 100644
--- a/compiler/rustc_parse/src/parser/pat.rs
+++ b/compiler/rustc_parse/src/parser/pat.rs
@@ -1516,7 +1516,7 @@ impl<'a> Parser<'a> {
                 || self.check_noexpect(&token::DotDotDot)
                 || self.check_keyword(exp!(Underscore))
             {
-                etc = PatFieldsRest::Rest;
+                etc = PatFieldsRest::Rest(self.token.span);
                 let mut etc_sp = self.token.span;
                 if first_etc_and_maybe_comma_span.is_none() {
                     if let Some(comma_tok) =
diff --git a/compiler/rustc_parse_format/Cargo.toml b/compiler/rustc_parse_format/Cargo.toml
index 645e34b6e32..d178fcda1fb 100644
--- a/compiler/rustc_parse_format/Cargo.toml
+++ b/compiler/rustc_parse_format/Cargo.toml
@@ -5,7 +5,7 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-rustc-literal-escaper.workspace = true
+rustc-literal-escaper = "0.0.5"
 rustc_lexer = { path = "../rustc_lexer" }
 # tidy-alphabetical-end
 
diff --git a/compiler/rustc_passes/Cargo.toml b/compiler/rustc_passes/Cargo.toml
index c74608a6146..ba81ef3103b 100644
--- a/compiler/rustc_passes/Cargo.toml
+++ b/compiler/rustc_passes/Cargo.toml
@@ -24,5 +24,5 @@ rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
 rustc_trait_selection = { path = "../rustc_trait_selection" }
-tracing.workspace = true
+tracing = "0.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_passes/messages.ftl b/compiler/rustc_passes/messages.ftl
index 498d9a405fa..afd08319738 100644
--- a/compiler/rustc_passes/messages.ftl
+++ b/compiler/rustc_passes/messages.ftl
@@ -687,6 +687,7 @@ passes_unused_var_maybe_capture_ref = unused variable: `{$name}`
 
 passes_unused_var_remove_field = unused variable: `{$name}`
 passes_unused_var_remove_field_suggestion = try removing the field
+passes_unused_var_typo = you might have meant to pattern match on the similarly named {$kind} `{$item_name}`
 
 passes_unused_variable_args_in_macro = `{$name}` is captured in macro and introduced a unused variable
 
diff --git a/compiler/rustc_passes/src/errors.rs b/compiler/rustc_passes/src/errors.rs
index 680e2a26d84..23dcabef1a1 100644
--- a/compiler/rustc_passes/src/errors.rs
+++ b/compiler/rustc_passes/src/errors.rs
@@ -1367,6 +1367,22 @@ pub(crate) struct UnusedVarRemoveFieldSugg {
 #[note]
 pub(crate) struct UnusedVarAssignedOnly {
     pub name: String,
+    #[subdiagnostic]
+    pub typo: Option<PatternTypo>,
+}
+
+#[derive(Subdiagnostic)]
+#[multipart_suggestion(
+    passes_unused_var_typo,
+    style = "verbose",
+    applicability = "machine-applicable"
+)]
+pub(crate) struct PatternTypo {
+    #[suggestion_part(code = "{code}")]
+    pub span: Span,
+    pub code: String,
+    pub item_name: String,
+    pub kind: String,
 }
 
 #[derive(LintDiagnostic)]
@@ -1434,6 +1450,8 @@ pub(crate) struct UnusedVariableTryPrefix {
     #[subdiagnostic]
     pub sugg: UnusedVariableSugg,
     pub name: String,
+    #[subdiagnostic]
+    pub typo: Option<PatternTypo>,
 }
 
 #[derive(Subdiagnostic)]
diff --git a/compiler/rustc_passes/src/liveness.rs b/compiler/rustc_passes/src/liveness.rs
index 801a533c943..1b2ffb5b3db 100644
--- a/compiler/rustc_passes/src/liveness.rs
+++ b/compiler/rustc_passes/src/liveness.rs
@@ -95,8 +95,10 @@ use rustc_hir::{Expr, HirId, HirIdMap, HirIdSet, find_attr};
 use rustc_index::IndexVec;
 use rustc_middle::query::Providers;
 use rustc_middle::span_bug;
+use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::{self, RootVariableMinCaptureList, Ty, TyCtxt};
 use rustc_session::lint;
+use rustc_span::edit_distance::find_best_match_for_name;
 use rustc_span::{BytePos, Span, Symbol};
 use tracing::{debug, instrument};
 
@@ -1583,7 +1585,7 @@ impl<'tcx> Liveness<'_, 'tcx> {
         });
 
         let can_remove = match pat.kind {
-            hir::PatKind::Struct(_, fields, true) => {
+            hir::PatKind::Struct(_, fields, Some(_)) => {
                 // if all fields are shorthand, remove the struct field, otherwise, mark with _ as prefix
                 fields.iter().all(|f| f.is_shorthand)
             }
@@ -1688,6 +1690,51 @@ impl<'tcx> Liveness<'_, 'tcx> {
             let is_assigned =
                 if ln == self.exit_ln { false } else { self.assigned_on_exit(ln, var) };
 
+            let mut typo = None;
+            for (hir_id, _, span) in &hir_ids_and_spans {
+                let ty = self.typeck_results.node_type(*hir_id);
+                if let ty::Adt(adt, _) = ty.peel_refs().kind() {
+                    let name = Symbol::intern(&name);
+                    let adt_def = self.ir.tcx.adt_def(adt.did());
+                    let variant_names: Vec<_> = adt_def
+                        .variants()
+                        .iter()
+                        .filter(|v| matches!(v.ctor, Some((CtorKind::Const, _))))
+                        .map(|v| v.name)
+                        .collect();
+                    if let Some(name) = find_best_match_for_name(&variant_names, name, None)
+                        && let Some(variant) = adt_def.variants().iter().find(|v| {
+                            v.name == name && matches!(v.ctor, Some((CtorKind::Const, _)))
+                        })
+                    {
+                        typo = Some(errors::PatternTypo {
+                            span: *span,
+                            code: with_no_trimmed_paths!(self.ir.tcx.def_path_str(variant.def_id)),
+                            kind: self.ir.tcx.def_descr(variant.def_id).to_string(),
+                            item_name: variant.name.to_string(),
+                        });
+                    }
+                }
+            }
+            if typo.is_none() {
+                for (hir_id, _, span) in &hir_ids_and_spans {
+                    let ty = self.typeck_results.node_type(*hir_id);
+                    // Look for consts of the same type with similar names as well, not just unit
+                    // structs and variants.
+                    for def_id in self.ir.tcx.hir_body_owners() {
+                        if let DefKind::Const = self.ir.tcx.def_kind(def_id)
+                            && self.ir.tcx.type_of(def_id).instantiate_identity() == ty
+                        {
+                            typo = Some(errors::PatternTypo {
+                                span: *span,
+                                code: with_no_trimmed_paths!(self.ir.tcx.def_path_str(def_id)),
+                                kind: "constant".to_string(),
+                                item_name: self.ir.tcx.item_name(def_id).to_string(),
+                            });
+                        }
+                    }
+                }
+            }
             if is_assigned {
                 self.ir.tcx.emit_node_span_lint(
                     lint::builtin::UNUSED_VARIABLES,
@@ -1696,7 +1743,7 @@ impl<'tcx> Liveness<'_, 'tcx> {
                         .into_iter()
                         .map(|(_, _, ident_span)| ident_span)
                         .collect::<Vec<_>>(),
-                    errors::UnusedVarAssignedOnly { name },
+                    errors::UnusedVarAssignedOnly { name, typo },
                 )
             } else if can_remove {
                 let spans = hir_ids_and_spans
@@ -1788,6 +1835,7 @@ impl<'tcx> Liveness<'_, 'tcx> {
                             name,
                             sugg,
                             string_interp: suggestions,
+                            typo,
                         },
                     );
                 }
diff --git a/compiler/rustc_pattern_analysis/Cargo.toml b/compiler/rustc_pattern_analysis/Cargo.toml
index e4909ab6d16..a59f7bbeb9e 100644
--- a/compiler/rustc_pattern_analysis/Cargo.toml
+++ b/compiler/rustc_pattern_analysis/Cargo.toml
@@ -5,9 +5,9 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-rustc-hash.workspace = true
+rustc-hash = "2.0.0"
 rustc_abi = { path = "../rustc_abi", optional = true }
-rustc_apfloat.workspace = true
+rustc_apfloat = "0.2.0"
 rustc_arena = { path = "../rustc_arena", optional = true }
 rustc_data_structures = { path = "../rustc_data_structures", optional = true }
 rustc_errors = { path = "../rustc_errors", optional = true }
@@ -19,7 +19,7 @@ rustc_middle = { path = "../rustc_middle", optional = true }
 rustc_session = { path = "../rustc_session", optional = true }
 rustc_span = { path = "../rustc_span", optional = true }
 smallvec = { version = "1.8.1", features = ["union"] }
-tracing.workspace = true
+tracing = "0.1"
 # tidy-alphabetical-end
 
 [dev-dependencies]
diff --git a/compiler/rustc_privacy/Cargo.toml b/compiler/rustc_privacy/Cargo.toml
index 7de58132e13..c8bfdb91304 100644
--- a/compiler/rustc_privacy/Cargo.toml
+++ b/compiler/rustc_privacy/Cargo.toml
@@ -15,5 +15,5 @@ rustc_middle = { path = "../rustc_middle" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_ty_utils = { path = "../rustc_ty_utils" }
-tracing.workspace = true
+tracing = "0.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_proc_macro/Cargo.toml b/compiler/rustc_proc_macro/Cargo.toml
index 99e7fc7abc6..beb95aa3b52 100644
--- a/compiler/rustc_proc_macro/Cargo.toml
+++ b/compiler/rustc_proc_macro/Cargo.toml
@@ -16,7 +16,7 @@ doctest = false
 
 [dependencies]
 # tidy-alphabetical-start
-rustc-literal-escaper.workspace = true
+rustc-literal-escaper = "0.0.5"
 # tidy-alphabetical-end
 
 [features]
diff --git a/compiler/rustc_public/Cargo.toml b/compiler/rustc_public/Cargo.toml
index e67e4fe6739..70af30c1a5f 100644
--- a/compiler/rustc_public/Cargo.toml
+++ b/compiler/rustc_public/Cargo.toml
@@ -12,9 +12,9 @@ rustc_public_bridge = { path = "../rustc_public_bridge" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
-scoped-tls.workspace = true
+scoped-tls = "1.0"
 serde = { version = "1.0.125", features = [ "derive" ] }
-tracing.workspace = true
+tracing = "0.1"
 # tidy-alphabetical-end
 
 [features]
diff --git a/compiler/rustc_public/src/unstable/convert/stable/ty.rs b/compiler/rustc_public/src/unstable/convert/stable/ty.rs
index 5a661072bc7..207038db40d 100644
--- a/compiler/rustc_public/src/unstable/convert/stable/ty.rs
+++ b/compiler/rustc_public/src/unstable/convert/stable/ty.rs
@@ -656,13 +656,13 @@ impl<'tcx> Stable<'tcx> for rustc_middle::ty::GenericParamDefKind {
 
     fn stable(&self, _: &mut Tables<'_, BridgeTys>, _: &CompilerCtxt<'_, BridgeTys>) -> Self::T {
         use crate::ty::GenericParamDefKind;
-        match self {
+        match *self {
             ty::GenericParamDefKind::Lifetime => GenericParamDefKind::Lifetime,
             ty::GenericParamDefKind::Type { has_default, synthetic } => {
-                GenericParamDefKind::Type { has_default: *has_default, synthetic: *synthetic }
+                GenericParamDefKind::Type { has_default, synthetic }
             }
-            ty::GenericParamDefKind::Const { has_default, synthetic: _ } => {
-                GenericParamDefKind::Const { has_default: *has_default }
+            ty::GenericParamDefKind::Const { has_default } => {
+                GenericParamDefKind::Const { has_default }
             }
         }
     }
diff --git a/compiler/rustc_query_impl/Cargo.toml b/compiler/rustc_query_impl/Cargo.toml
index 3d5cf0eb72d..e5cceacf15d 100644
--- a/compiler/rustc_query_impl/Cargo.toml
+++ b/compiler/rustc_query_impl/Cargo.toml
@@ -5,7 +5,7 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-measureme.workspace = true 
+measureme = "12.0.1"
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_hashes = { path = "../rustc_hashes" }
 rustc_hir = { path = "../rustc_hir" }
@@ -15,5 +15,5 @@ rustc_query_system = { path = "../rustc_query_system" }
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
-tracing.workspace = true
+tracing = "0.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_query_impl/src/lib.rs b/compiler/rustc_query_impl/src/lib.rs
index 306d4dbc4b4..e499e08c82b 100644
--- a/compiler/rustc_query_impl/src/lib.rs
+++ b/compiler/rustc_query_impl/src/lib.rs
@@ -58,7 +58,7 @@ impl<'tcx, C: QueryCache, const ANON: bool, const DEPTH_LIMIT: bool, const FEEDA
     for DynamicConfig<'tcx, C, ANON, DEPTH_LIMIT, FEEDABLE>
 {
     fn clone(&self) -> Self {
-        DynamicConfig { dynamic: self.dynamic }
+        *self
     }
 }
 
diff --git a/compiler/rustc_query_system/Cargo.toml b/compiler/rustc_query_system/Cargo.toml
index 0df933bc81c..7480ba03474 100644
--- a/compiler/rustc_query_system/Cargo.toml
+++ b/compiler/rustc_query_system/Cargo.toml
@@ -21,7 +21,7 @@ rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_thread_pool = { path = "../rustc_thread_pool" }
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
-tracing.workspace = true
+tracing = "0.1"
 # tidy-alphabetical-end
 
 [dependencies.hashbrown]
diff --git a/compiler/rustc_query_system/messages.ftl b/compiler/rustc_query_system/messages.ftl
index f48dc60afa0..f686608034c 100644
--- a/compiler/rustc_query_system/messages.ftl
+++ b/compiler/rustc_query_system/messages.ftl
@@ -18,8 +18,8 @@ query_system_cycle_usage = cycle used when {$usage}
 query_system_increment_compilation = internal compiler error: encountered incremental compilation error with {$dep_node}
     .help = This is a known issue with the compiler. Run {$run_cmd} to allow your project to compile
 
-query_system_increment_compilation_note1 = Please follow the instructions below to create a bug report with the provided information
-query_system_increment_compilation_note2 = See <https://github.com/rust-lang/rust/issues/84970> for more information
+query_system_increment_compilation_note1 = please follow the instructions below to create a bug report with the provided information
+query_system_increment_compilation_note2 = see <https://github.com/rust-lang/rust/issues/84970> for more information
 
 query_system_overflow_note = query depth increased by {$depth} when {$desc}
 
diff --git a/compiler/rustc_resolve/Cargo.toml b/compiler/rustc_resolve/Cargo.toml
index 4da4c0840df..eb98a6e85c0 100644
--- a/compiler/rustc_resolve/Cargo.toml
+++ b/compiler/rustc_resolve/Cargo.toml
@@ -5,9 +5,9 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-bitflags.workspace = true
-indexmap.workspace = true
-itertools.workspace = true
+bitflags = "2.4.1"
+indexmap = "2.4.0"
+itertools = "0.12"
 pulldown-cmark = { version = "0.11", features = ["html"], default-features = false }
 rustc_arena = { path = "../rustc_arena" }
 rustc_ast = { path = "../rustc_ast" }
@@ -27,6 +27,6 @@ rustc_query_system = { path = "../rustc_query_system" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
-thin-vec.workspace = true
-tracing.workspace = true
+thin-vec = "0.2.12"
+tracing = "0.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_resolve/messages.ftl b/compiler/rustc_resolve/messages.ftl
index 47280a93677..0e566e20a12 100644
--- a/compiler/rustc_resolve/messages.ftl
+++ b/compiler/rustc_resolve/messages.ftl
@@ -470,6 +470,8 @@ resolve_variable_bound_with_different_mode =
     .label = bound in different ways
     .first_binding_span = first binding
 
+resolve_variable_is_a_typo = you might have meant to use the similarly named previously used binding `{$typo}`
+
 resolve_variable_is_not_bound_in_all_patterns =
     variable `{$name}` is not bound in all patterns
 
diff --git a/compiler/rustc_resolve/src/diagnostics.rs b/compiler/rustc_resolve/src/diagnostics.rs
index 5dfc4292a38..689e713ef46 100644
--- a/compiler/rustc_resolve/src/diagnostics.rs
+++ b/compiler/rustc_resolve/src/diagnostics.rs
@@ -1,3 +1,4 @@
+use itertools::Itertools as _;
 use rustc_ast::visit::{self, Visitor};
 use rustc_ast::{
     self as ast, CRATE_NODE_ID, Crate, ItemKind, ModKind, NodeId, Path, join_path_idents,
@@ -661,8 +662,12 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             ResolutionError::VariableNotBoundInPattern(binding_error, parent_scope) => {
                 let BindingError { name, target, origin, could_be_path } = binding_error;
 
-                let target_sp = target.iter().copied().collect::<Vec<_>>();
-                let origin_sp = origin.iter().copied().collect::<Vec<_>>();
+                let mut target_sp = target.iter().map(|pat| pat.span).collect::<Vec<_>>();
+                target_sp.sort();
+                target_sp.dedup();
+                let mut origin_sp = origin.iter().map(|(span, _)| *span).collect::<Vec<_>>();
+                origin_sp.sort();
+                origin_sp.dedup();
 
                 let msp = MultiSpan::from_spans(target_sp.clone());
                 let mut err = self
@@ -671,8 +676,35 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 for sp in target_sp {
                     err.subdiagnostic(errors::PatternDoesntBindName { span: sp, name });
                 }
-                for sp in origin_sp {
-                    err.subdiagnostic(errors::VariableNotInAllPatterns { span: sp });
+                for sp in &origin_sp {
+                    err.subdiagnostic(errors::VariableNotInAllPatterns { span: *sp });
+                }
+                let mut suggested_typo = false;
+                if !target.iter().all(|pat| matches!(pat.kind, ast::PatKind::Ident(..)))
+                    && !origin.iter().all(|(_, pat)| matches!(pat.kind, ast::PatKind::Ident(..)))
+                {
+                    // The check above is so that when we encounter `match foo { (a | b) => {} }`,
+                    // we don't suggest `(a | a) => {}`, which would never be what the user wants.
+                    let mut target_visitor = BindingVisitor::default();
+                    for pat in &target {
+                        target_visitor.visit_pat(pat);
+                    }
+                    target_visitor.identifiers.sort();
+                    target_visitor.identifiers.dedup();
+                    let mut origin_visitor = BindingVisitor::default();
+                    for (_, pat) in &origin {
+                        origin_visitor.visit_pat(pat);
+                    }
+                    origin_visitor.identifiers.sort();
+                    origin_visitor.identifiers.dedup();
+                    // Find if the binding could have been a typo
+                    if let Some(typo) =
+                        find_best_match_for_name(&target_visitor.identifiers, name.name, None)
+                        && !origin_visitor.identifiers.contains(&typo)
+                    {
+                        err.subdiagnostic(errors::PatternBindingTypo { spans: origin_sp, typo });
+                        suggested_typo = true;
+                    }
                 }
                 if could_be_path {
                     let import_suggestions = self.lookup_import_candidates(
@@ -693,10 +725,86 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                         },
                     );
 
-                    if import_suggestions.is_empty() {
+                    if import_suggestions.is_empty() && !suggested_typo {
+                        let kinds = [
+                            DefKind::Ctor(CtorOf::Variant, CtorKind::Const),
+                            DefKind::Ctor(CtorOf::Struct, CtorKind::Const),
+                            DefKind::Const,
+                            DefKind::AssocConst,
+                        ];
+                        let mut local_names = vec![];
+                        self.add_module_candidates(
+                            parent_scope.module,
+                            &mut local_names,
+                            &|res| matches!(res, Res::Def(_, _)),
+                            None,
+                        );
+                        let local_names: FxHashSet<_> = local_names
+                            .into_iter()
+                            .filter_map(|s| match s.res {
+                                Res::Def(_, def_id) => Some(def_id),
+                                _ => None,
+                            })
+                            .collect();
+
+                        let mut local_suggestions = vec![];
+                        let mut suggestions = vec![];
+                        for kind in kinds {
+                            if let Some(suggestion) = self.early_lookup_typo_candidate(
+                                ScopeSet::All(Namespace::ValueNS),
+                                &parent_scope,
+                                name,
+                                &|res: Res| match res {
+                                    Res::Def(k, _) => k == kind,
+                                    _ => false,
+                                },
+                            ) && let Res::Def(kind, mut def_id) = suggestion.res
+                            {
+                                if let DefKind::Ctor(_, _) = kind {
+                                    def_id = self.tcx.parent(def_id);
+                                }
+                                let kind = kind.descr(def_id);
+                                if local_names.contains(&def_id) {
+                                    // The item is available in the current scope. Very likely to
+                                    // be a typo. Don't use the full path.
+                                    local_suggestions.push((
+                                        suggestion.candidate,
+                                        suggestion.candidate.to_string(),
+                                        kind,
+                                    ));
+                                } else {
+                                    suggestions.push((
+                                        suggestion.candidate,
+                                        self.def_path_str(def_id),
+                                        kind,
+                                    ));
+                                }
+                            }
+                        }
+                        let suggestions = if !local_suggestions.is_empty() {
+                            // There is at least one item available in the current scope that is a
+                            // likely typo. We only show those.
+                            local_suggestions
+                        } else {
+                            suggestions
+                        };
+                        for (name, sugg, kind) in suggestions {
+                            err.span_suggestion_verbose(
+                                span,
+                                format!(
+                                    "you might have meant to use the similarly named {kind} `{name}`",
+                                ),
+                                sugg,
+                                Applicability::MaybeIncorrect,
+                            );
+                            suggested_typo = true;
+                        }
+                    }
+                    if import_suggestions.is_empty() && !suggested_typo {
                         let help_msg = format!(
-                            "if you meant to match on a variant or a `const` item, consider \
-                             making the path in the pattern qualified: `path::to::ModOrType::{name}`",
+                            "if you meant to match on a unit struct, unit variant or a `const` \
+                             item, consider making the path in the pattern qualified: \
+                             `path::to::ModOrType::{name}`",
                         );
                         err.span_help(span, help_msg);
                     }
@@ -1016,6 +1124,39 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         .emit()
     }
 
+    fn def_path_str(&self, mut def_id: DefId) -> String {
+        // We can't use `def_path_str` in resolve.
+        let mut path = vec![def_id];
+        while let Some(parent) = self.tcx.opt_parent(def_id) {
+            def_id = parent;
+            path.push(def_id);
+            if def_id.is_top_level_module() {
+                break;
+            }
+        }
+        // We will only suggest importing directly if it is accessible through that path.
+        path.into_iter()
+            .rev()
+            .map(|def_id| {
+                self.tcx
+                    .opt_item_name(def_id)
+                    .map(|name| {
+                        match (
+                            def_id.is_top_level_module(),
+                            def_id.is_local(),
+                            self.tcx.sess.edition(),
+                        ) {
+                            (true, true, Edition::Edition2015) => String::new(),
+                            (true, true, _) => kw::Crate.to_string(),
+                            (true, false, _) | (false, _, _) => name.to_string(),
+                        }
+                    })
+                    .unwrap_or_else(|| "_".to_string())
+            })
+            .collect::<Vec<String>>()
+            .join("::")
+    }
+
     pub(crate) fn add_scope_set_candidates(
         &mut self,
         suggestions: &mut Vec<TypoSuggestion>,
@@ -1846,7 +1987,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         let extern_prelude_ambiguity = || {
             self.extern_prelude.get(&Macros20NormalizedIdent::new(ident)).is_some_and(|entry| {
                 entry.item_binding.map(|(b, _)| b) == Some(b1)
-                    && entry.flag_binding.as_ref().and_then(|pb| pb.get().binding()) == Some(b2)
+                    && entry.flag_binding.as_ref().and_then(|pb| pb.get().0.binding()) == Some(b2)
             })
         };
         let (b1, b2, misc1, misc2, swapped) = if b2.span.is_dummy() && !b1.span.is_dummy() {
@@ -3329,16 +3470,11 @@ fn show_candidates(
                 err.note(note.to_string());
             }
         } else {
-            let (_, descr_first, _, _, _) = &inaccessible_path_strings[0];
-            let descr = if inaccessible_path_strings
+            let descr = inaccessible_path_strings
                 .iter()
-                .skip(1)
-                .all(|(_, descr, _, _, _)| descr == descr_first)
-            {
-                descr_first
-            } else {
-                "item"
-            };
+                .map(|&(_, descr, _, _, _)| descr)
+                .all_equal_value()
+                .unwrap_or("item");
             let plural_descr =
                 if descr.ends_with('s') { format!("{descr}es") } else { format!("{descr}s") };
 
@@ -3396,7 +3532,7 @@ impl UsePlacementFinder {
     }
 }
 
-impl<'tcx> visit::Visitor<'tcx> for UsePlacementFinder {
+impl<'tcx> Visitor<'tcx> for UsePlacementFinder {
     fn visit_crate(&mut self, c: &Crate) {
         if self.target_module == CRATE_NODE_ID {
             let inject = c.spans.inject_use_span;
@@ -3424,6 +3560,22 @@ impl<'tcx> visit::Visitor<'tcx> for UsePlacementFinder {
     }
 }
 
+#[derive(Default)]
+struct BindingVisitor {
+    identifiers: Vec<Symbol>,
+    spans: FxHashMap<Symbol, Vec<Span>>,
+}
+
+impl<'tcx> Visitor<'tcx> for BindingVisitor {
+    fn visit_pat(&mut self, pat: &ast::Pat) {
+        if let ast::PatKind::Ident(_, ident, _) = pat.kind {
+            self.identifiers.push(ident.name);
+            self.spans.entry(ident.name).or_default().push(ident.span);
+        }
+        visit::walk_pat(self, pat);
+    }
+}
+
 fn search_for_any_use_in_items(items: &[Box<ast::Item>]) -> Option<Span> {
     for item in items {
         if let ItemKind::Use(..) = item.kind
diff --git a/compiler/rustc_resolve/src/errors.rs b/compiler/rustc_resolve/src/errors.rs
index 63d6fa23a14..72be94e58db 100644
--- a/compiler/rustc_resolve/src/errors.rs
+++ b/compiler/rustc_resolve/src/errors.rs
@@ -986,6 +986,18 @@ pub(crate) struct VariableNotInAllPatterns {
     pub(crate) span: Span,
 }
 
+#[derive(Subdiagnostic)]
+#[multipart_suggestion(
+    resolve_variable_is_a_typo,
+    applicability = "maybe-incorrect",
+    style = "verbose"
+)]
+pub(crate) struct PatternBindingTypo {
+    #[suggestion_part(code = "{typo}")]
+    pub(crate) spans: Vec<Span>,
+    pub(crate) typo: Symbol,
+}
+
 #[derive(Diagnostic)]
 #[diag(resolve_name_defined_multiple_time)]
 #[note]
diff --git a/compiler/rustc_resolve/src/ident.rs b/compiler/rustc_resolve/src/ident.rs
index dae42645bec..bc06a227571 100644
--- a/compiler/rustc_resolve/src/ident.rs
+++ b/compiler/rustc_resolve/src/ident.rs
@@ -422,6 +422,8 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         // to detect potential ambiguities.
         let mut innermost_result: Option<(NameBinding<'_>, Flags)> = None;
         let mut determinacy = Determinacy::Determined;
+        let mut extern_prelude_item_binding = None;
+        let mut extern_prelude_flag_binding = None;
         // Shadowed bindings don't need to be marked as used or non-speculatively loaded.
         macro finalize_scope() {
             if innermost_result.is_none() { finalize } else { None }
@@ -558,7 +560,10 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     Scope::ExternPreludeItems => {
                         // FIXME: use `finalize_scope` here.
                         match this.reborrow().extern_prelude_get_item(ident, finalize.is_some()) {
-                            Some(binding) => Ok((binding, Flags::empty())),
+                            Some(binding) => {
+                                extern_prelude_item_binding = Some(binding);
+                                Ok((binding, Flags::empty()))
+                            }
                             None => Err(Determinacy::determined(
                                 this.graph_root.unexpanded_invocations.borrow().is_empty(),
                             )),
@@ -566,7 +571,10 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     }
                     Scope::ExternPreludeFlags => {
                         match this.extern_prelude_get_flag(ident, finalize_scope!().is_some()) {
-                            Some(binding) => Ok((binding, Flags::empty())),
+                            Some(binding) => {
+                                extern_prelude_flag_binding = Some(binding);
+                                Ok((binding, Flags::empty()))
+                            }
                             None => Err(Determinacy::Determined),
                         }
                     }
@@ -686,7 +694,16 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                                 } else {
                                     None
                                 };
-                                if let Some(kind) = ambiguity_error_kind {
+                                // Skip ambiguity errors for extern flag bindings "overridden"
+                                // by extern item bindings.
+                                // FIXME: Remove with lang team approval.
+                                let issue_145575_hack = Some(binding)
+                                    == extern_prelude_flag_binding
+                                    && extern_prelude_item_binding.is_some()
+                                    && extern_prelude_item_binding != Some(innermost_binding);
+                                if let Some(kind) = ambiguity_error_kind
+                                    && !issue_145575_hack
+                                {
                                     let misc = |f: Flags| {
                                         if f.contains(Flags::MISC_SUGGEST_CRATE) {
                                             AmbiguityErrorMisc::SuggestCrate
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index d4f7fb276a9..521fef2b9d4 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -8,7 +8,6 @@
 
 use std::assert_matches::debug_assert_matches;
 use std::borrow::Cow;
-use std::collections::BTreeSet;
 use std::collections::hash_map::Entry;
 use std::mem::{replace, swap, take};
 
@@ -3682,31 +3681,30 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
         // 2) Record any missing bindings or binding mode inconsistencies.
         for (map_outer, pat_outer) in not_never_pats.iter() {
             // Check against all arms except for the same pattern which is always self-consistent.
-            let inners = not_never_pats
-                .iter()
-                .filter(|(_, pat)| pat.id != pat_outer.id)
-                .flat_map(|(map, _)| map);
-
-            for (&name, binding_inner) in inners {
-                match map_outer.get(&name) {
-                    None => {
-                        // The inner binding is missing in the outer.
-                        let binding_error =
-                            missing_vars.entry(name).or_insert_with(|| BindingError {
-                                name,
-                                origin: BTreeSet::new(),
-                                target: BTreeSet::new(),
-                                could_be_path: name.as_str().starts_with(char::is_uppercase),
-                            });
-                        binding_error.origin.insert(binding_inner.span);
-                        binding_error.target.insert(pat_outer.span);
-                    }
-                    Some(binding_outer) => {
-                        if binding_outer.annotation != binding_inner.annotation {
-                            // The binding modes in the outer and inner bindings differ.
-                            inconsistent_vars
-                                .entry(name)
-                                .or_insert((binding_inner.span, binding_outer.span));
+            let inners = not_never_pats.iter().filter(|(_, pat)| pat.id != pat_outer.id);
+
+            for (map, pat) in inners {
+                for (&name, binding_inner) in map {
+                    match map_outer.get(&name) {
+                        None => {
+                            // The inner binding is missing in the outer.
+                            let binding_error =
+                                missing_vars.entry(name).or_insert_with(|| BindingError {
+                                    name,
+                                    origin: Default::default(),
+                                    target: Default::default(),
+                                    could_be_path: name.as_str().starts_with(char::is_uppercase),
+                                });
+                            binding_error.origin.push((binding_inner.span, (***pat).clone()));
+                            binding_error.target.push((***pat_outer).clone());
+                        }
+                        Some(binding_outer) => {
+                            if binding_outer.annotation != binding_inner.annotation {
+                                // The binding modes in the outer and inner bindings differ.
+                                inconsistent_vars
+                                    .entry(name)
+                                    .or_insert((binding_inner.span, binding_outer.span));
+                            }
                         }
                     }
                 }
@@ -3719,7 +3717,7 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                 v.could_be_path = false;
             }
             self.report_error(
-                *v.origin.iter().next().unwrap(),
+                v.origin.iter().next().unwrap().0,
                 ResolutionError::VariableNotBoundInPattern(v, self.parent_scope),
             );
         }
@@ -3922,7 +3920,7 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
 
     fn record_patterns_with_skipped_bindings(&mut self, pat: &Pat, rest: &ast::PatFieldsRest) {
         match rest {
-            ast::PatFieldsRest::Rest | ast::PatFieldsRest::Recovered(_) => {
+            ast::PatFieldsRest::Rest(_) | ast::PatFieldsRest::Recovered(_) => {
                 // Record that the pattern doesn't introduce all the bindings it could.
                 if let Some(partial_res) = self.r.partial_res_map.get(&pat.id)
                     && let Some(res) = partial_res.full_res()
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
index 80b2095d8cc..9e3c0938836 100644
--- a/compiler/rustc_resolve/src/late/diagnostics.rs
+++ b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -3099,7 +3099,7 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                 |err, _, span, message, suggestion, span_suggs| {
                     err.multipart_suggestion_verbose(
                         message,
-                        std::iter::once((span, suggestion)).chain(span_suggs.clone()).collect(),
+                        std::iter::once((span, suggestion)).chain(span_suggs).collect(),
                         Applicability::MaybeIncorrect,
                     );
                     true
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
index 9674c0356c2..8b185ce7ef2 100644
--- a/compiler/rustc_resolve/src/lib.rs
+++ b/compiler/rustc_resolve/src/lib.rs
@@ -230,8 +230,8 @@ enum Used {
 #[derive(Debug)]
 struct BindingError {
     name: Ident,
-    origin: BTreeSet<Span>,
-    target: BTreeSet<Span>,
+    origin: Vec<(Span, ast::Pat)>,
+    target: Vec<ast::Pat>,
     could_be_path: bool,
 }
 
@@ -1031,7 +1031,7 @@ struct ExternPreludeEntry<'ra> {
     /// `flag_binding` is `None`, or when `extern crate` introducing `item_binding` used renaming.
     item_binding: Option<(NameBinding<'ra>, /* introduced by item */ bool)>,
     /// Binding from an `--extern` flag, lazily populated on first use.
-    flag_binding: Option<Cell<PendingBinding<'ra>>>,
+    flag_binding: Option<Cell<(PendingBinding<'ra>, /* finalized */ bool)>>,
 }
 
 impl ExternPreludeEntry<'_> {
@@ -1042,7 +1042,7 @@ impl ExternPreludeEntry<'_> {
     fn flag() -> Self {
         ExternPreludeEntry {
             item_binding: None,
-            flag_binding: Some(Cell::new(PendingBinding::Pending)),
+            flag_binding: Some(Cell::new((PendingBinding::Pending, false))),
         }
     }
 }
@@ -2245,14 +2245,16 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
     fn extern_prelude_get_flag(&self, ident: Ident, finalize: bool) -> Option<NameBinding<'ra>> {
         let entry = self.extern_prelude.get(&Macros20NormalizedIdent::new(ident));
         entry.and_then(|entry| entry.flag_binding.as_ref()).and_then(|flag_binding| {
-            let binding = match flag_binding.get() {
+            let (pending_binding, finalized) = flag_binding.get();
+            let binding = match pending_binding {
                 PendingBinding::Ready(binding) => {
-                    if finalize {
+                    if finalize && !finalized {
                         self.cstore_mut().process_path_extern(self.tcx, ident.name, ident.span);
                     }
                     binding
                 }
                 PendingBinding::Pending => {
+                    debug_assert!(!finalized);
                     let crate_id = if finalize {
                         self.cstore_mut().process_path_extern(self.tcx, ident.name, ident.span)
                     } else {
@@ -2264,7 +2266,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     })
                 }
             };
-            flag_binding.set(PendingBinding::Ready(binding));
+            flag_binding.set((PendingBinding::Ready(binding), finalize || finalized));
             binding.or_else(|| finalize.then_some(self.dummy_binding))
         })
     }
diff --git a/compiler/rustc_sanitizers/Cargo.toml b/compiler/rustc_sanitizers/Cargo.toml
index 3dbeaa435f3..9069d2c233d 100644
--- a/compiler/rustc_sanitizers/Cargo.toml
+++ b/compiler/rustc_sanitizers/Cargo.toml
@@ -5,7 +5,7 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-bitflags.workspace = true
+bitflags = "2.5.0"
 rustc_abi = { path = "../rustc_abi" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_hir = { path = "../rustc_hir" }
@@ -13,6 +13,6 @@ rustc_middle = { path = "../rustc_middle" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
 rustc_trait_selection = { path = "../rustc_trait_selection" }
-tracing.workspace = true
+tracing = "0.1"
 twox-hash = "1.6.3"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_serialize/Cargo.toml b/compiler/rustc_serialize/Cargo.toml
index 853f87ebed9..948242352e7 100644
--- a/compiler/rustc_serialize/Cargo.toml
+++ b/compiler/rustc_serialize/Cargo.toml
@@ -5,14 +5,14 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-indexmap.workspace = true
+indexmap = "2.0.0"
 rustc_hashes = { path = "../rustc_hashes" }
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
-thin-vec.workspace = true
+thin-vec = "0.2.12"
 # tidy-alphabetical-end
 
 [dev-dependencies]
 # tidy-alphabetical-start
 rustc_macros = { path = "../rustc_macros" }
-tempfile.workspace = true
+tempfile = "3.2"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_session/Cargo.toml b/compiler/rustc_session/Cargo.toml
index 5870fb29ae8..60d56b1b808 100644
--- a/compiler/rustc_session/Cargo.toml
+++ b/compiler/rustc_session/Cargo.toml
@@ -5,7 +5,7 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-bitflags.workspace = true
+bitflags = "2.4.1"
 getopts = "0.2"
 rand = "0.9.0"
 rustc_abi = { path = "../rustc_abi" }
@@ -23,12 +23,14 @@ rustc_serialize = { path = "../rustc_serialize" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
 termize = "0.2"
-tracing.workspace = true
+tracing = "0.1"
 # tidy-alphabetical-end
 
 [target.'cfg(unix)'.dependencies]
+# FIXME: Remove this pin once this rustix issue is resolved
+# https://github.com/bytecodealliance/rustix/issues/1496
 # tidy-alphabetical-start
-libc.workspace = true
+libc = "=0.2.174"
 # tidy-alphabetical-end
 
 [target.'cfg(windows)'.dependencies.windows]
diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs
index 6d5be2d92cd..69facde6936 100644
--- a/compiler/rustc_session/src/options.rs
+++ b/compiler/rustc_session/src/options.rs
@@ -83,10 +83,77 @@ pub struct TargetModifier {
     pub value_name: String,
 }
 
+mod target_modifier_consistency_check {
+    use super::*;
+    pub(super) fn sanitizer(l: &TargetModifier, r: Option<&TargetModifier>) -> bool {
+        let mut lparsed: SanitizerSet = Default::default();
+        let lval = if l.value_name.is_empty() { None } else { Some(l.value_name.as_str()) };
+        parse::parse_sanitizers(&mut lparsed, lval);
+
+        let mut rparsed: SanitizerSet = Default::default();
+        let rval = r.filter(|v| !v.value_name.is_empty()).map(|v| v.value_name.as_str());
+        parse::parse_sanitizers(&mut rparsed, rval);
+
+        // Some sanitizers need to be target modifiers, and some do not.
+        // For now, we should mark all sanitizers as target modifiers except for these:
+        // AddressSanitizer, LeakSanitizer
+        let tmod_sanitizers = SanitizerSet::MEMORY
+            | SanitizerSet::THREAD
+            | SanitizerSet::HWADDRESS
+            | SanitizerSet::CFI
+            | SanitizerSet::MEMTAG
+            | SanitizerSet::SHADOWCALLSTACK
+            | SanitizerSet::KCFI
+            | SanitizerSet::KERNELADDRESS
+            | SanitizerSet::SAFESTACK
+            | SanitizerSet::DATAFLOW;
+
+        lparsed & tmod_sanitizers == rparsed & tmod_sanitizers
+    }
+    pub(super) fn sanitizer_cfi_normalize_integers(
+        opts: &Options,
+        l: &TargetModifier,
+        r: Option<&TargetModifier>,
+    ) -> bool {
+        // For kCFI, the helper flag -Zsanitizer-cfi-normalize-integers should also be a target modifier
+        if opts.unstable_opts.sanitizer.contains(SanitizerSet::KCFI) {
+            if let Some(r) = r {
+                return l.extend().tech_value == r.extend().tech_value;
+            } else {
+                return false;
+            }
+        }
+        true
+    }
+}
+
 impl TargetModifier {
     pub fn extend(&self) -> ExtendedTargetModifierInfo {
         self.opt.reparse(&self.value_name)
     }
+    // Custom consistency check for target modifiers (or default `l.tech_value == r.tech_value`)
+    // When other is None, consistency with default value is checked
+    pub fn consistent(&self, opts: &Options, other: Option<&TargetModifier>) -> bool {
+        assert!(other.is_none() || self.opt == other.unwrap().opt);
+        match self.opt {
+            OptionsTargetModifiers::UnstableOptions(unstable) => match unstable {
+                UnstableOptionsTargetModifiers::sanitizer => {
+                    return target_modifier_consistency_check::sanitizer(self, other);
+                }
+                UnstableOptionsTargetModifiers::sanitizer_cfi_normalize_integers => {
+                    return target_modifier_consistency_check::sanitizer_cfi_normalize_integers(
+                        opts, self, other,
+                    );
+                }
+                _ => {}
+            },
+            _ => {}
+        };
+        match other {
+            Some(other) => self.extend().tech_value == other.extend().tech_value,
+            None => false,
+        }
+    }
 }
 
 fn tmod_push_impl(
@@ -2504,13 +2571,13 @@ written to standard error output)"),
     retpoline_external_thunk: bool = (false, parse_bool, [TRACKED TARGET_MODIFIER],
         "enables retpoline-external-thunk, retpoline-indirect-branches and retpoline-indirect-calls \
         target features (default: no)"),
-    sanitizer: SanitizerSet = (SanitizerSet::empty(), parse_sanitizers, [TRACKED],
+    sanitizer: SanitizerSet = (SanitizerSet::empty(), parse_sanitizers, [TRACKED TARGET_MODIFIER],
         "use a sanitizer"),
     sanitizer_cfi_canonical_jump_tables: Option<bool> = (Some(true), parse_opt_bool, [TRACKED],
         "enable canonical jump tables (default: yes)"),
     sanitizer_cfi_generalize_pointers: Option<bool> = (None, parse_opt_bool, [TRACKED],
         "enable generalizing pointer types (default: no)"),
-    sanitizer_cfi_normalize_integers: Option<bool> = (None, parse_opt_bool, [TRACKED],
+    sanitizer_cfi_normalize_integers: Option<bool> = (None, parse_opt_bool, [TRACKED TARGET_MODIFIER],
         "enable normalizing integer types (default: no)"),
     sanitizer_dataflow_abilist: Vec<String> = (Vec::new(), parse_comma_list, [TRACKED],
         "additional ABI list files that control how shadow parameters are passed (comma separated)"),
diff --git a/compiler/rustc_span/Cargo.toml b/compiler/rustc_span/Cargo.toml
index da6f2101d23..43a2d692577 100644
--- a/compiler/rustc_span/Cargo.toml
+++ b/compiler/rustc_span/Cargo.toml
@@ -6,8 +6,8 @@ edition = "2024"
 [dependencies]
 # tidy-alphabetical-start
 blake3 = "1.5.2"
-derive-where.workspace = true
-indexmap.workspace = true
+derive-where = "1.2.7"
+indexmap = { version = "2.0.0" }
 itoa = "1.0"
 md5 = { package = "md-5", version = "0.10.0" }
 rustc_arena = { path = "../rustc_arena" }
@@ -16,9 +16,9 @@ rustc_hashes = { path = "../rustc_hashes" }
 rustc_index = { path = "../rustc_index" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_serialize = { path = "../rustc_serialize" }
-scoped-tls.workspace = true
+scoped-tls = "1.0"
 sha1 = "0.10.0"
 sha2 = "0.10.1"
-tracing.workspace = true
+tracing = "0.1"
 unicode-width = "0.2.0"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 77260d07c99..e5108d8b7e9 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -2162,6 +2162,7 @@ symbols! {
         target_family,
         target_feature,
         target_feature_11,
+        target_feature_inline_always,
         target_has_atomic,
         target_has_atomic_equal_alignment,
         target_has_atomic_load_store,
@@ -2280,6 +2281,8 @@ symbols! {
         unboxed_closures,
         unchecked_add,
         unchecked_div,
+        unchecked_funnel_shl,
+        unchecked_funnel_shr,
         unchecked_mul,
         unchecked_rem,
         unchecked_shl,
diff --git a/compiler/rustc_symbol_mangling/Cargo.toml b/compiler/rustc_symbol_mangling/Cargo.toml
index 0ceac4b3e1b..0df9c7682bf 100644
--- a/compiler/rustc_symbol_mangling/Cargo.toml
+++ b/compiler/rustc_symbol_mangling/Cargo.toml
@@ -6,7 +6,7 @@ edition = "2024"
 [dependencies]
 # tidy-alphabetical-start
 punycode = "0.4.0"
-rustc-demangle.workspace = true
+rustc-demangle = "0.1.21"
 rustc_abi = { path = "../rustc_abi" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
@@ -15,5 +15,5 @@ rustc_hir = { path = "../rustc_hir" }
 rustc_middle = { path = "../rustc_middle" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
-tracing.workspace = true
+tracing = "0.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_symbol_mangling/src/v0.rs b/compiler/rustc_symbol_mangling/src/v0.rs
index 0cbd48ba08c..0655c2d5e81 100644
--- a/compiler/rustc_symbol_mangling/src/v0.rs
+++ b/compiler/rustc_symbol_mangling/src/v0.rs
@@ -82,9 +82,13 @@ pub(super) fn mangle<'tcx>(
 }
 
 pub fn mangle_internal_symbol<'tcx>(tcx: TyCtxt<'tcx>, item_name: &str) -> String {
-    if item_name == "rust_eh_personality" {
+    match item_name {
         // rust_eh_personality must not be renamed as LLVM hard-codes the name
-        return "rust_eh_personality".to_owned();
+        "rust_eh_personality" => return item_name.to_owned(),
+        // Apple availability symbols need to not be mangled to be usable by
+        // C/Objective-C code.
+        "__isPlatformVersionAtLeast" | "__isOSVersionAtLeast" => return item_name.to_owned(),
+        _ => {}
     }
 
     let prefix = "_R";
diff --git a/compiler/rustc_target/Cargo.toml b/compiler/rustc_target/Cargo.toml
index ed59ee2a575..7fabb227d9a 100644
--- a/compiler/rustc_target/Cargo.toml
+++ b/compiler/rustc_target/Cargo.toml
@@ -5,7 +5,7 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-bitflags.workspace = true
+bitflags = "2.4.1"
 object = { version = "0.37.0", default-features = false, features = ["elf", "macho"] }
 rustc_abi = { path = "../rustc_abi" }
 rustc_data_structures = { path = "../rustc_data_structures" }
@@ -16,8 +16,8 @@ rustc_serialize = { path = "../rustc_serialize" }
 rustc_span = { path = "../rustc_span" }
 serde = "1.0.219"
 serde_derive = "1.0.219"
-serde_json.workspace = true
+serde_json = "1.0.59"
 serde_path_to_error = "0.1.17"
-tracing.workspace = true
+tracing = "0.1"
 # tidy-alphabetical-end
 
diff --git a/compiler/rustc_target/src/callconv/loongarch.rs b/compiler/rustc_target/src/callconv/loongarch.rs
index d567ad401bb..9213d73e24e 100644
--- a/compiler/rustc_target/src/callconv/loongarch.rs
+++ b/compiler/rustc_target/src/callconv/loongarch.rs
@@ -8,16 +8,16 @@ use crate::spec::HasTargetSpec;
 
 #[derive(Copy, Clone)]
 enum RegPassKind {
-    Float(Reg),
-    Integer(Reg),
+    Float { offset_from_start: Size, ty: Reg },
+    Integer { offset_from_start: Size, ty: Reg },
     Unknown,
 }
 
 #[derive(Copy, Clone)]
 enum FloatConv {
-    FloatPair(Reg, Reg),
+    FloatPair { first_ty: Reg, second_ty_offset_from_start: Size, second_ty: Reg },
     Float(Reg),
-    MixedPair(Reg, Reg),
+    MixedPair { first_ty: Reg, second_ty_offset_from_start: Size, second_ty: Reg },
 }
 
 #[derive(Copy, Clone)]
@@ -37,6 +37,7 @@ fn should_use_fp_conv_helper<'a, Ty, C>(
     flen: u64,
     field1_kind: &mut RegPassKind,
     field2_kind: &mut RegPassKind,
+    offset_from_start: Size,
 ) -> Result<(), CannotUseFpConv>
 where
     Ty: TyAbiInterface<'a, C> + Copy,
@@ -49,16 +50,16 @@ where
                 }
                 match (*field1_kind, *field2_kind) {
                     (RegPassKind::Unknown, _) => {
-                        *field1_kind = RegPassKind::Integer(Reg {
-                            kind: RegKind::Integer,
-                            size: arg_layout.size,
-                        });
+                        *field1_kind = RegPassKind::Integer {
+                            offset_from_start,
+                            ty: Reg { kind: RegKind::Integer, size: arg_layout.size },
+                        };
                     }
-                    (RegPassKind::Float(_), RegPassKind::Unknown) => {
-                        *field2_kind = RegPassKind::Integer(Reg {
-                            kind: RegKind::Integer,
-                            size: arg_layout.size,
-                        });
+                    (RegPassKind::Float { .. }, RegPassKind::Unknown) => {
+                        *field2_kind = RegPassKind::Integer {
+                            offset_from_start,
+                            ty: Reg { kind: RegKind::Integer, size: arg_layout.size },
+                        };
                     }
                     _ => return Err(CannotUseFpConv),
                 }
@@ -69,12 +70,16 @@ where
                 }
                 match (*field1_kind, *field2_kind) {
                     (RegPassKind::Unknown, _) => {
-                        *field1_kind =
-                            RegPassKind::Float(Reg { kind: RegKind::Float, size: arg_layout.size });
+                        *field1_kind = RegPassKind::Float {
+                            offset_from_start,
+                            ty: Reg { kind: RegKind::Float, size: arg_layout.size },
+                        };
                     }
                     (_, RegPassKind::Unknown) => {
-                        *field2_kind =
-                            RegPassKind::Float(Reg { kind: RegKind::Float, size: arg_layout.size });
+                        *field2_kind = RegPassKind::Float {
+                            offset_from_start,
+                            ty: Reg { kind: RegKind::Float, size: arg_layout.size },
+                        };
                     }
                     _ => return Err(CannotUseFpConv),
                 }
@@ -96,13 +101,14 @@ where
                             flen,
                             field1_kind,
                             field2_kind,
+                            offset_from_start,
                         );
                     }
                     return Err(CannotUseFpConv);
                 }
             }
             FieldsShape::Array { count, .. } => {
-                for _ in 0..count {
+                for i in 0..count {
                     let elem_layout = arg_layout.field(cx, 0);
                     should_use_fp_conv_helper(
                         cx,
@@ -111,6 +117,7 @@ where
                         flen,
                         field1_kind,
                         field2_kind,
+                        offset_from_start + elem_layout.size * i,
                     )?;
                 }
             }
@@ -121,7 +128,15 @@ where
                 }
                 for i in arg_layout.fields.index_by_increasing_offset() {
                     let field = arg_layout.field(cx, i);
-                    should_use_fp_conv_helper(cx, &field, xlen, flen, field1_kind, field2_kind)?;
+                    should_use_fp_conv_helper(
+                        cx,
+                        &field,
+                        xlen,
+                        flen,
+                        field1_kind,
+                        field2_kind,
+                        offset_from_start + arg_layout.fields.offset(i),
+                    )?;
                 }
             }
         },
@@ -140,14 +155,52 @@ where
 {
     let mut field1_kind = RegPassKind::Unknown;
     let mut field2_kind = RegPassKind::Unknown;
-    if should_use_fp_conv_helper(cx, arg, xlen, flen, &mut field1_kind, &mut field2_kind).is_err() {
+    if should_use_fp_conv_helper(
+        cx,
+        arg,
+        xlen,
+        flen,
+        &mut field1_kind,
+        &mut field2_kind,
+        Size::ZERO,
+    )
+    .is_err()
+    {
         return None;
     }
     match (field1_kind, field2_kind) {
-        (RegPassKind::Integer(l), RegPassKind::Float(r)) => Some(FloatConv::MixedPair(l, r)),
-        (RegPassKind::Float(l), RegPassKind::Integer(r)) => Some(FloatConv::MixedPair(l, r)),
-        (RegPassKind::Float(l), RegPassKind::Float(r)) => Some(FloatConv::FloatPair(l, r)),
-        (RegPassKind::Float(f), RegPassKind::Unknown) => Some(FloatConv::Float(f)),
+        (
+            RegPassKind::Integer { offset_from_start, .. }
+            | RegPassKind::Float { offset_from_start, .. },
+            _,
+        ) if offset_from_start != Size::ZERO => {
+            panic!("type {:?} has a first field with non-zero offset {offset_from_start:?}", arg.ty)
+        }
+        (
+            RegPassKind::Integer { ty: first_ty, .. },
+            RegPassKind::Float { offset_from_start, ty: second_ty },
+        ) => Some(FloatConv::MixedPair {
+            first_ty,
+            second_ty_offset_from_start: offset_from_start,
+            second_ty,
+        }),
+        (
+            RegPassKind::Float { ty: first_ty, .. },
+            RegPassKind::Integer { offset_from_start, ty: second_ty },
+        ) => Some(FloatConv::MixedPair {
+            first_ty,
+            second_ty_offset_from_start: offset_from_start,
+            second_ty,
+        }),
+        (
+            RegPassKind::Float { ty: first_ty, .. },
+            RegPassKind::Float { offset_from_start, ty: second_ty },
+        ) => Some(FloatConv::FloatPair {
+            first_ty,
+            second_ty_offset_from_start: offset_from_start,
+            second_ty,
+        }),
+        (RegPassKind::Float { ty, .. }, RegPassKind::Unknown) => Some(FloatConv::Float(ty)),
         _ => None,
     }
 }
@@ -165,11 +218,19 @@ where
             FloatConv::Float(f) => {
                 arg.cast_to(f);
             }
-            FloatConv::FloatPair(l, r) => {
-                arg.cast_to(CastTarget::pair(l, r));
+            FloatConv::FloatPair { first_ty, second_ty_offset_from_start, second_ty } => {
+                arg.cast_to(CastTarget::offset_pair(
+                    first_ty,
+                    second_ty_offset_from_start,
+                    second_ty,
+                ));
             }
-            FloatConv::MixedPair(l, r) => {
-                arg.cast_to(CastTarget::pair(l, r));
+            FloatConv::MixedPair { first_ty, second_ty_offset_from_start, second_ty } => {
+                arg.cast_to(CastTarget::offset_pair(
+                    first_ty,
+                    second_ty_offset_from_start,
+                    second_ty,
+                ));
             }
         }
         return false;
@@ -233,15 +294,27 @@ fn classify_arg<'a, Ty, C>(
                 arg.cast_to(f);
                 return;
             }
-            Some(FloatConv::FloatPair(l, r)) if *avail_fprs >= 2 => {
+            Some(FloatConv::FloatPair { first_ty, second_ty_offset_from_start, second_ty })
+                if *avail_fprs >= 2 =>
+            {
                 *avail_fprs -= 2;
-                arg.cast_to(CastTarget::pair(l, r));
+                arg.cast_to(CastTarget::offset_pair(
+                    first_ty,
+                    second_ty_offset_from_start,
+                    second_ty,
+                ));
                 return;
             }
-            Some(FloatConv::MixedPair(l, r)) if *avail_fprs >= 1 && *avail_gprs >= 1 => {
+            Some(FloatConv::MixedPair { first_ty, second_ty_offset_from_start, second_ty })
+                if *avail_fprs >= 1 && *avail_gprs >= 1 =>
+            {
                 *avail_gprs -= 1;
                 *avail_fprs -= 1;
-                arg.cast_to(CastTarget::pair(l, r));
+                arg.cast_to(CastTarget::offset_pair(
+                    first_ty,
+                    second_ty_offset_from_start,
+                    second_ty,
+                ));
                 return;
             }
             _ => (),
diff --git a/compiler/rustc_target/src/spec/targets/aarch64_pc_windows_msvc.rs b/compiler/rustc_target/src/spec/targets/aarch64_pc_windows_msvc.rs
index f1b6fa123de..cd55576ef81 100644
--- a/compiler/rustc_target/src/spec/targets/aarch64_pc_windows_msvc.rs
+++ b/compiler/rustc_target/src/spec/targets/aarch64_pc_windows_msvc.rs
@@ -15,7 +15,7 @@ pub(crate) fn target() -> Target {
         llvm_target: "aarch64-pc-windows-msvc".into(),
         metadata: TargetMetadata {
             description: Some("ARM64 Windows MSVC".into()),
-            tier: Some(2),
+            tier: Some(1),
             host_tools: Some(true),
             std: Some(true),
         },
diff --git a/compiler/rustc_target/src/spec/targets/aarch64_unknown_trusty.rs b/compiler/rustc_target/src/spec/targets/aarch64_unknown_trusty.rs
index 126f0251239..05783fde1ad 100644
--- a/compiler/rustc_target/src/spec/targets/aarch64_unknown_trusty.rs
+++ b/compiler/rustc_target/src/spec/targets/aarch64_unknown_trusty.rs
@@ -11,7 +11,7 @@ pub(crate) fn target() -> Target {
             description: Some("ARM64 Trusty".into()),
             tier: Some(3),
             host_tools: Some(false),
-            std: Some(false),
+            std: Some(true),
         },
         pointer_width: 64,
         data_layout: "e-m:e-p270:32:32-p271:32:32-p272:64:64-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128-Fn32".into(),
diff --git a/compiler/rustc_target/src/spec/targets/arm64ec_pc_windows_msvc.rs b/compiler/rustc_target/src/spec/targets/arm64ec_pc_windows_msvc.rs
index 8f93523909e..7292412a18d 100644
--- a/compiler/rustc_target/src/spec/targets/arm64ec_pc_windows_msvc.rs
+++ b/compiler/rustc_target/src/spec/targets/arm64ec_pc_windows_msvc.rs
@@ -20,9 +20,9 @@ pub(crate) fn target() -> Target {
         llvm_target: "arm64ec-pc-windows-msvc".into(),
         metadata: TargetMetadata {
             description: Some("Arm64EC Windows MSVC".into()),
-            tier: Some(3),
+            tier: Some(2),
             host_tools: Some(false),
-            std: None, // ?
+            std: Some(true),
         },
         pointer_width: 64,
         data_layout:
diff --git a/compiler/rustc_target/src/spec/targets/armv7_unknown_trusty.rs b/compiler/rustc_target/src/spec/targets/armv7_unknown_trusty.rs
index 31d492e83cd..2b0b0e1d117 100644
--- a/compiler/rustc_target/src/spec/targets/armv7_unknown_trusty.rs
+++ b/compiler/rustc_target/src/spec/targets/armv7_unknown_trusty.rs
@@ -13,7 +13,7 @@ pub(crate) fn target() -> Target {
             description: Some("Armv7-A Trusty".into()),
             tier: Some(3),
             host_tools: Some(false),
-            std: Some(false),
+            std: Some(true),
         },
         pointer_width: 32,
         data_layout: "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64".into(),
diff --git a/compiler/rustc_target/src/spec/targets/loongarch64_unknown_none.rs b/compiler/rustc_target/src/spec/targets/loongarch64_unknown_none.rs
index 91e3064aaed..b6a08958284 100644
--- a/compiler/rustc_target/src/spec/targets/loongarch64_unknown_none.rs
+++ b/compiler/rustc_target/src/spec/targets/loongarch64_unknown_none.rs
@@ -17,7 +17,7 @@ pub(crate) fn target() -> Target {
         arch: "loongarch64".into(),
         options: TargetOptions {
             cpu: "generic".into(),
-            features: "+f,+d".into(),
+            features: "+f,+d,-lsx".into(),
             linker_flavor: LinkerFlavor::Gnu(Cc::No, Lld::Yes),
             linker: Some("rust-lld".into()),
             llvm_abiname: "lp64d".into(),
diff --git a/compiler/rustc_target/src/spec/targets/nvptx64_nvidia_cuda.rs b/compiler/rustc_target/src/spec/targets/nvptx64_nvidia_cuda.rs
index 598f0f19f0d..cada0dd640a 100644
--- a/compiler/rustc_target/src/spec/targets/nvptx64_nvidia_cuda.rs
+++ b/compiler/rustc_target/src/spec/targets/nvptx64_nvidia_cuda.rs
@@ -6,7 +6,7 @@ use crate::spec::{
 pub(crate) fn target() -> Target {
     Target {
         arch: "nvptx64".into(),
-        data_layout: "e-p6:32:32-i64:64-i128:128-v16:16-v32:32-n16:32:64".into(),
+        data_layout: "e-p6:32:32-i64:64-i128:128-i256:256-v16:16-v32:32-n16:32:64".into(),
         llvm_target: "nvptx64-nvidia-cuda".into(),
         metadata: TargetMetadata {
             description: Some("--emit=asm generates PTX code that runs on NVIDIA GPUs".into()),
diff --git a/compiler/rustc_target/src/spec/targets/x86_64_unknown_trusty.rs b/compiler/rustc_target/src/spec/targets/x86_64_unknown_trusty.rs
index c7b002bc9bb..dbcb5fd4e11 100644
--- a/compiler/rustc_target/src/spec/targets/x86_64_unknown_trusty.rs
+++ b/compiler/rustc_target/src/spec/targets/x86_64_unknown_trusty.rs
@@ -12,7 +12,7 @@ pub(crate) fn target() -> Target {
             description: Some("x86_64 Trusty".into()),
             tier: Some(3),
             host_tools: Some(false),
-            std: Some(false),
+            std: Some(true),
         },
         pointer_width: 64,
         data_layout:
diff --git a/compiler/rustc_thread_pool/Cargo.toml b/compiler/rustc_thread_pool/Cargo.toml
index 8e8c6469512..c92984470b7 100644
--- a/compiler/rustc_thread_pool/Cargo.toml
+++ b/compiler/rustc_thread_pool/Cargo.toml
@@ -20,10 +20,10 @@ smallvec = "1.8.1"
 [dev-dependencies]
 rand = "0.9"
 rand_xorshift = "0.4"
-scoped-tls.workspace = true
+scoped-tls = "1.0"
 
 [target.'cfg(unix)'.dev-dependencies]
-libc.workspace = true
+libc = "0.2"
 
 [[test]]
 name = "stack_overflow_crash"
diff --git a/compiler/rustc_trait_selection/Cargo.toml b/compiler/rustc_trait_selection/Cargo.toml
index 6b79b98d1bf..1071105522d 100644
--- a/compiler/rustc_trait_selection/Cargo.toml
+++ b/compiler/rustc_trait_selection/Cargo.toml
@@ -5,7 +5,7 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-itertools.workspace = true
+itertools = "0.12"
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
 rustc_data_structures = { path = "../rustc_data_structures" }
@@ -21,6 +21,6 @@ rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_transmute = { path = "../rustc_transmute", features = ["rustc"] }
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
-thin-vec.workspace = true
-tracing.workspace = true
+thin-vec = "0.2"
+tracing = "0.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
index 9447612d026..812e20e4338 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
@@ -318,7 +318,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     let (expected, found) = if expected_str == found_str {
                         (join_path_syms(&expected_abs), join_path_syms(&found_abs))
                     } else {
-                        (expected_str.clone(), found_str.clone())
+                        (expected_str, found_str)
                     };
 
                     // We've displayed "expected `a::b`, found `a::b`". We add context to
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
index 40a27c9aebe..f6dbbeb51ca 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
@@ -32,8 +32,8 @@ use rustc_middle::ty::print::{
 };
 use rustc_middle::ty::{
     self, AdtKind, GenericArgs, InferTy, IsSuggestable, Ty, TyCtxt, TypeFoldable, TypeFolder,
-    TypeSuperFoldable, TypeVisitableExt, TypeckResults, Upcast, suggest_arbitrary_trait_bound,
-    suggest_constraining_type_param,
+    TypeSuperFoldable, TypeSuperVisitable, TypeVisitableExt, TypeVisitor, TypeckResults, Upcast,
+    suggest_arbitrary_trait_bound, suggest_constraining_type_param,
 };
 use rustc_middle::{bug, span_bug};
 use rustc_span::def_id::LocalDefId;
@@ -263,6 +263,9 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             _ => (false, None),
         };
 
+        let mut finder = ParamFinder { .. };
+        finder.visit_binder(&trait_pred);
+
         // FIXME: Add check for trait bound that is already present, particularly `?Sized` so we
         //        don't suggest `T: Sized + ?Sized`.
         loop {
@@ -411,6 +414,26 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     }
                 }
 
+                hir::Node::TraitItem(hir::TraitItem {
+                    generics,
+                    kind: hir::TraitItemKind::Fn(..),
+                    ..
+                })
+                | hir::Node::ImplItem(hir::ImplItem {
+                    generics,
+                    trait_item_def_id: None,
+                    kind: hir::ImplItemKind::Fn(..),
+                    ..
+                }) if finder.can_suggest_bound(generics) => {
+                    // Missing generic type parameter bound.
+                    suggest_arbitrary_trait_bound(
+                        self.tcx,
+                        generics,
+                        err,
+                        trait_pred,
+                        associated_ty,
+                    );
+                }
                 hir::Node::Item(hir::Item {
                     kind:
                         hir::ItemKind::Struct(_, generics, _)
@@ -423,7 +446,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                         | hir::ItemKind::Const(_, generics, _, _)
                         | hir::ItemKind::TraitAlias(_, generics, _),
                     ..
-                }) if !param_ty => {
+                }) if finder.can_suggest_bound(generics) => {
                     // Missing generic type parameter bound.
                     if suggest_arbitrary_trait_bound(
                         self.tcx,
@@ -5068,8 +5091,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         // Suggesting `T: ?Sized` is only valid in an ADT if `T` is only used in a
         // borrow. `struct S<'a, T: ?Sized>(&'a T);` is valid, `struct S<T: ?Sized>(T);`
         // is not. Look for invalid "bare" parameter uses, and suggest using indirection.
-        let mut visitor =
-            FindTypeParam { param: param.name.ident().name, invalid_spans: vec![], nested: false };
+        let mut visitor = FindTypeParam { param: param.name.ident().name, .. };
         visitor.visit_item(item);
         if visitor.invalid_spans.is_empty() {
             return false;
@@ -5228,7 +5250,7 @@ fn hint_missing_borrow<'tcx>(
 /// Used to suggest replacing associated types with an explicit type in `where` clauses.
 #[derive(Debug)]
 pub struct SelfVisitor<'v> {
-    pub paths: Vec<&'v hir::Ty<'v>>,
+    pub paths: Vec<&'v hir::Ty<'v>> = Vec::new(),
     pub name: Option<Symbol>,
 }
 
@@ -5599,7 +5621,7 @@ fn point_at_assoc_type_restriction<G: EmissionGuarantee>(
                 );
                 // Search for the associated type `Self::{name}`, get
                 // its type and suggest replacing the bound with it.
-                let mut visitor = SelfVisitor { paths: vec![], name: Some(name) };
+                let mut visitor = SelfVisitor { name: Some(name), .. };
                 visitor.visit_trait_ref(trait_ref);
                 for path in visitor.paths {
                     err.span_suggestion_verbose(
@@ -5610,7 +5632,7 @@ fn point_at_assoc_type_restriction<G: EmissionGuarantee>(
                     );
                 }
             } else {
-                let mut visitor = SelfVisitor { paths: vec![], name: None };
+                let mut visitor = SelfVisitor { name: None, .. };
                 visitor.visit_trait_ref(trait_ref);
                 let span: MultiSpan =
                     visitor.paths.iter().map(|p| p.span).collect::<Vec<Span>>().into();
@@ -5640,8 +5662,8 @@ fn get_deref_type_and_refs(mut ty: Ty<'_>) -> (Ty<'_>, Vec<hir::Mutability>) {
 /// `param: ?Sized` would be a valid constraint.
 struct FindTypeParam {
     param: rustc_span::Symbol,
-    invalid_spans: Vec<Span>,
-    nested: bool,
+    invalid_spans: Vec<Span> = Vec::new(),
+    nested: bool = false,
 }
 
 impl<'v> Visitor<'v> for FindTypeParam {
@@ -5679,3 +5701,38 @@ impl<'v> Visitor<'v> for FindTypeParam {
         }
     }
 }
+
+/// Look for type parameters in predicates. We use this to identify whether a bound is suitable in
+/// on a given item.
+struct ParamFinder {
+    params: Vec<Symbol> = Vec::new(),
+}
+
+impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ParamFinder {
+    fn visit_ty(&mut self, t: Ty<'tcx>) -> Self::Result {
+        match t.kind() {
+            ty::Param(p) => self.params.push(p.name),
+            _ => {}
+        }
+        t.super_visit_with(self)
+    }
+}
+
+impl ParamFinder {
+    /// Whether the `hir::Generics` of the current item can suggest the evaluated bound because its
+    /// references to type parameters are present in the generics.
+    fn can_suggest_bound(&self, generics: &hir::Generics<'_>) -> bool {
+        if self.params.is_empty() {
+            // There are no references to type parameters at all, so suggesting the bound
+            // would be reasonable.
+            return true;
+        }
+        generics.params.iter().any(|p| match p.name {
+            hir::ParamName::Plain(p_name) => {
+                // All of the parameters in the bound can be referenced in the current item.
+                self.params.iter().any(|p| *p == p_name.name || *p == kw::SelfUpper)
+            }
+            _ => true,
+        })
+    }
+}
diff --git a/compiler/rustc_trait_selection/src/lib.rs b/compiler/rustc_trait_selection/src/lib.rs
index e2b22f7bab7..fc0cf8f140a 100644
--- a/compiler/rustc_trait_selection/src/lib.rs
+++ b/compiler/rustc_trait_selection/src/lib.rs
@@ -19,6 +19,7 @@
 #![feature(assert_matches)]
 #![feature(associated_type_defaults)]
 #![feature(box_patterns)]
+#![feature(default_field_values)]
 #![feature(if_let_guard)]
 #![feature(iter_intersperse)]
 #![feature(iterator_try_reduce)]
diff --git a/compiler/rustc_trait_selection/src/solve.rs b/compiler/rustc_trait_selection/src/solve.rs
index f58961683a9..5d200c4d340 100644
--- a/compiler/rustc_trait_selection/src/solve.rs
+++ b/compiler/rustc_trait_selection/src/solve.rs
@@ -13,4 +13,20 @@ pub use normalize::{
     deeply_normalize, deeply_normalize_with_skipped_universes,
     deeply_normalize_with_skipped_universes_and_ambiguous_coroutine_goals,
 };
+use rustc_middle::query::Providers;
+use rustc_middle::ty::TyCtxt;
 pub use select::InferCtxtSelectExt;
+
+fn evaluate_root_goal_for_proof_tree_raw<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    canonical_input: CanonicalInput<TyCtxt<'tcx>>,
+) -> (QueryResult<TyCtxt<'tcx>>, &'tcx inspect::Probe<TyCtxt<'tcx>>) {
+    evaluate_root_goal_for_proof_tree_raw_provider::<SolverDelegate<'tcx>, TyCtxt<'tcx>>(
+        tcx,
+        canonical_input,
+    )
+}
+
+pub fn provide(providers: &mut Providers) {
+    *providers = Providers { evaluate_root_goal_for_proof_tree_raw, ..*providers };
+}
diff --git a/compiler/rustc_trait_selection/src/solve/inspect/analyse.rs b/compiler/rustc_trait_selection/src/solve/inspect/analyse.rs
index 308486811e6..342d7121fc3 100644
--- a/compiler/rustc_trait_selection/src/solve/inspect/analyse.rs
+++ b/compiler/rustc_trait_selection/src/solve/inspect/analyse.rs
@@ -37,7 +37,7 @@ pub struct InspectGoal<'a, 'tcx> {
     orig_values: Vec<ty::GenericArg<'tcx>>,
     goal: Goal<'tcx, ty::Predicate<'tcx>>,
     result: Result<Certainty, NoSolution>,
-    evaluation_kind: inspect::GoalEvaluationKind<TyCtxt<'tcx>>,
+    final_revision: &'tcx inspect::Probe<TyCtxt<'tcx>>,
     normalizes_to_term_hack: Option<NormalizesToTermHack<'tcx>>,
     source: GoalSource,
 }
@@ -249,7 +249,7 @@ impl<'a, 'tcx> InspectCandidate<'a, 'tcx> {
                     // `InspectGoal::new` so that the goal has the right result (and maintains
                     // the impression that we don't do this normalizes-to infer hack at all).
                     let (nested, proof_tree) = infcx.evaluate_root_goal_for_proof_tree(goal, span);
-                    let nested_goals_result = nested.and_then(|(nested, _)| {
+                    let nested_goals_result = nested.and_then(|nested| {
                         normalizes_to_term_hack.constrain_and(
                             infcx,
                             span,
@@ -391,15 +391,8 @@ impl<'a, 'tcx> InspectGoal<'a, 'tcx> {
 
     pub fn candidates(&'a self) -> Vec<InspectCandidate<'a, 'tcx>> {
         let mut candidates = vec![];
-        let last_eval_step = match &self.evaluation_kind {
-            // An annoying edge case in case the recursion limit is 0.
-            inspect::GoalEvaluationKind::Overflow => return vec![],
-            inspect::GoalEvaluationKind::Evaluation { final_revision } => final_revision,
-        };
-
         let mut nested_goals = vec![];
-        self.candidates_recur(&mut candidates, &mut nested_goals, &last_eval_step);
-
+        self.candidates_recur(&mut candidates, &mut nested_goals, &self.final_revision);
         candidates
     }
 
@@ -426,7 +419,8 @@ impl<'a, 'tcx> InspectGoal<'a, 'tcx> {
     ) -> Self {
         let infcx = <&SolverDelegate<'tcx>>::from(infcx);
 
-        let inspect::GoalEvaluation { uncanonicalized_goal, orig_values, kind, result } = root;
+        let inspect::GoalEvaluation { uncanonicalized_goal, orig_values, final_revision, result } =
+            root;
         // If there's a normalizes-to goal, AND the evaluation result with the result of
         // constraining the normalizes-to RHS and computing the nested goals.
         let result = result.and_then(|ok| {
@@ -441,7 +435,7 @@ impl<'a, 'tcx> InspectGoal<'a, 'tcx> {
             orig_values,
             goal: eager_resolve_vars(infcx, uncanonicalized_goal),
             result,
-            evaluation_kind: kind,
+            final_revision,
             normalizes_to_term_hack: term_hack_and_nested_certainty.map(|(n, _)| n),
             source,
         }
diff --git a/compiler/rustc_traits/Cargo.toml b/compiler/rustc_traits/Cargo.toml
index 24360a94cc7..9f40f4d5c23 100644
--- a/compiler/rustc_traits/Cargo.toml
+++ b/compiler/rustc_traits/Cargo.toml
@@ -10,5 +10,5 @@ rustc_infer = { path = "../rustc_infer" }
 rustc_middle = { path = "../rustc_middle" }
 rustc_span = { path = "../rustc_span" }
 rustc_trait_selection = { path = "../rustc_trait_selection" }
-tracing.workspace = true
+tracing = "0.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_transmute/Cargo.toml b/compiler/rustc_transmute/Cargo.toml
index 2ac2b46cc58..e61717e5e9c 100644
--- a/compiler/rustc_transmute/Cargo.toml
+++ b/compiler/rustc_transmute/Cargo.toml
@@ -11,12 +11,12 @@ rustc_hir = { path = "../rustc_hir", optional = true }
 rustc_middle = { path = "../rustc_middle", optional = true }
 rustc_span = { path = "../rustc_span", optional = true }
 smallvec = "1.8.1"
-tracing.workspace = true
+tracing = "0.1"
 # tidy-alphabetical-end
 
 [dev-dependencies]
 # tidy-alphabetical-start
-itertools.workspace = true
+itertools = "0.12"
 # tidy-alphabetical-end
 
 [features]
diff --git a/compiler/rustc_ty_utils/Cargo.toml b/compiler/rustc_ty_utils/Cargo.toml
index 394cde5a323..ce08b300cc8 100644
--- a/compiler/rustc_ty_utils/Cargo.toml
+++ b/compiler/rustc_ty_utils/Cargo.toml
@@ -5,7 +5,7 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-itertools.workspace = true
+itertools = "0.12"
 rustc_abi = { path = "../rustc_abi" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }
@@ -20,5 +20,5 @@ rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
 rustc_trait_selection = { path = "../rustc_trait_selection" }
-tracing.workspace = true
+tracing = "0.1"
 # tidy-alphabetical-end
diff --git a/compiler/rustc_type_ir/Cargo.toml b/compiler/rustc_type_ir/Cargo.toml
index 42860fa2d88..d55e9b3b1be 100644
--- a/compiler/rustc_type_ir/Cargo.toml
+++ b/compiler/rustc_type_ir/Cargo.toml
@@ -5,11 +5,11 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-bitflags.workspace = true
-derive-where.workspace = true
+bitflags = "2.4.1"
+derive-where = "1.2.7"
 ena = "0.14.3"
-indexmap.workspace = true
-rustc-hash.workspace = true
+indexmap = "2.0.0"
+rustc-hash = "2.0.0"
 rustc_ast_ir = { path = "../rustc_ast_ir", default-features = false }
 rustc_data_structures = { path = "../rustc_data_structures", optional = true }
 rustc_error_messages = { path = "../rustc_error_messages", optional = true }
@@ -19,8 +19,8 @@ rustc_serialize = { path = "../rustc_serialize", optional = true }
 rustc_span = { path = "../rustc_span", optional = true }
 rustc_type_ir_macros = { path = "../rustc_type_ir_macros" }
 smallvec = { version = "1.8.1", default-features = false, features = ["const_generics"] }
-thin-vec.workspace = true
-tracing.workspace = true
+thin-vec = "0.2.12"
+tracing = "0.1"
 # tidy-alphabetical-end
 
 [features]
diff --git a/compiler/rustc_type_ir/src/interner.rs b/compiler/rustc_type_ir/src/interner.rs
index 03a8f5e74b4..3a83b1739ff 100644
--- a/compiler/rustc_type_ir/src/interner.rs
+++ b/compiler/rustc_type_ir/src/interner.rs
@@ -1,3 +1,4 @@
+use std::borrow::Borrow;
 use std::fmt::Debug;
 use std::hash::Hash;
 use std::ops::Deref;
@@ -10,7 +11,9 @@ use crate::inherent::*;
 use crate::ir_print::IrPrint;
 use crate::lang_items::{SolverAdtLangItem, SolverLangItem, SolverTraitLangItem};
 use crate::relate::Relate;
-use crate::solve::{CanonicalInput, ExternalConstraintsData, PredefinedOpaquesData, QueryResult};
+use crate::solve::{
+    CanonicalInput, ExternalConstraintsData, PredefinedOpaquesData, QueryResult, inspect,
+};
 use crate::visit::{Flags, TypeVisitable};
 use crate::{self as ty, CanonicalParamEnvCacheEntry, search_graph};
 
@@ -394,6 +397,13 @@ pub trait Interner:
         self,
         defining_anchor: Self::LocalDefId,
     ) -> Self::LocalDefIds;
+
+    type Probe: Debug + Hash + Eq + Borrow<inspect::Probe<Self>>;
+    fn mk_probe(self, probe: inspect::Probe<Self>) -> Self::Probe;
+    fn evaluate_root_goal_for_proof_tree_raw(
+        self,
+        canonical_goal: CanonicalInput<Self>,
+    ) -> (QueryResult<Self>, Self::Probe);
 }
 
 /// Imagine you have a function `F: FnOnce(&[T]) -> R`, plus an iterator `iter`
diff --git a/compiler/rustc_type_ir/src/search_graph/mod.rs b/compiler/rustc_type_ir/src/search_graph/mod.rs
index 348178a527f..dbbc0c217d7 100644
--- a/compiler/rustc_type_ir/src/search_graph/mod.rs
+++ b/compiler/rustc_type_ir/src/search_graph/mod.rs
@@ -92,11 +92,7 @@ pub trait Delegate: Sized {
         input: <Self::Cx as Cx>::Input,
         result: <Self::Cx as Cx>::Result,
     ) -> bool;
-    fn on_stack_overflow(
-        cx: Self::Cx,
-        input: <Self::Cx as Cx>::Input,
-        inspect: &mut Self::ProofTreeBuilder,
-    ) -> <Self::Cx as Cx>::Result;
+    fn on_stack_overflow(cx: Self::Cx, input: <Self::Cx as Cx>::Input) -> <Self::Cx as Cx>::Result;
     fn on_fixpoint_overflow(
         cx: Self::Cx,
         input: <Self::Cx as Cx>::Input,
@@ -703,6 +699,31 @@ impl<D: Delegate<Cx = X>, X: Cx> SearchGraph<D> {
         }
     }
 
+    pub fn evaluate_root_goal_for_proof_tree(
+        cx: X,
+        root_depth: usize,
+        input: X::Input,
+        inspect: &mut D::ProofTreeBuilder,
+    ) -> X::Result {
+        let mut this = SearchGraph::<D>::new(root_depth);
+        let available_depth = AvailableDepth(root_depth);
+        let step_kind_from_parent = PathKind::Inductive; // is never used
+        this.stack.push(StackEntry {
+            input,
+            step_kind_from_parent,
+            available_depth,
+            provisional_result: None,
+            required_depth: 0,
+            heads: Default::default(),
+            encountered_overflow: false,
+            usages: None,
+            candidate_usages: None,
+            nested_goals: Default::default(),
+        });
+        let evaluation_result = this.evaluate_goal_in_task(cx, input, inspect);
+        evaluation_result.result
+    }
+
     /// Probably the most involved method of the whole solver.
     ///
     /// While goals get computed via `D::compute_goal`, this function handles
@@ -718,7 +739,7 @@ impl<D: Delegate<Cx = X>, X: Cx> SearchGraph<D> {
         let Some(available_depth) =
             AvailableDepth::allowed_depth_for_nested::<D>(self.root_depth, &self.stack)
         else {
-            return self.handle_overflow(cx, input, inspect);
+            return self.handle_overflow(cx, input);
         };
 
         // We check the provisional cache before checking the global cache. This simplifies
@@ -833,12 +854,7 @@ impl<D: Delegate<Cx = X>, X: Cx> SearchGraph<D> {
         result
     }
 
-    fn handle_overflow(
-        &mut self,
-        cx: X,
-        input: X::Input,
-        inspect: &mut D::ProofTreeBuilder,
-    ) -> X::Result {
+    fn handle_overflow(&mut self, cx: X, input: X::Input) -> X::Result {
         if let Some(last) = self.stack.last_mut() {
             last.encountered_overflow = true;
             // If computing a goal `B` depends on another goal `A` and
@@ -853,7 +869,7 @@ impl<D: Delegate<Cx = X>, X: Cx> SearchGraph<D> {
         }
 
         debug!("encountered stack overflow");
-        D::on_stack_overflow(cx, input, inspect)
+        D::on_stack_overflow(cx, input)
     }
 
     /// When reevaluating a goal with a changed provisional result, all provisional cache entry
diff --git a/compiler/rustc_type_ir/src/solve/inspect.rs b/compiler/rustc_type_ir/src/solve/inspect.rs
index afb4043648f..3af2f8dbaf2 100644
--- a/compiler/rustc_type_ir/src/solve/inspect.rs
+++ b/compiler/rustc_type_ir/src/solve/inspect.rs
@@ -45,31 +45,18 @@ pub type CanonicalState<I, T> = Canonical<I, State<I, T>>;
 /// for the `CanonicalVarValues` of the canonicalized goal.
 /// We use this to map any [CanonicalState] from the local `InferCtxt`
 /// of the solver query to the `InferCtxt` of the caller.
-#[derive_where(PartialEq, Hash; I: Interner)]
+#[derive_where(PartialEq, Eq, Hash; I: Interner)]
 pub struct GoalEvaluation<I: Interner> {
     pub uncanonicalized_goal: Goal<I, I::Predicate>,
     pub orig_values: Vec<I::GenericArg>,
-    pub kind: GoalEvaluationKind<I>,
+    pub final_revision: I::Probe,
     pub result: QueryResult<I>,
 }
 
-impl<I: Interner> Eq for GoalEvaluation<I> {}
-
-#[derive_where(PartialEq, Hash, Debug; I: Interner)]
-pub enum GoalEvaluationKind<I: Interner> {
-    Overflow,
-    Evaluation {
-        /// This is always `ProbeKind::Root`.
-        final_revision: Probe<I>,
-    },
-}
-
-impl<I: Interner> Eq for GoalEvaluationKind<I> {}
-
 /// A self-contained computation during trait solving. This either
 /// corresponds to a `EvalCtxt::probe(_X)` call or the root evaluation
 /// of a goal.
-#[derive_where(PartialEq, Hash, Debug; I: Interner)]
+#[derive_where(PartialEq, Eq, Hash, Debug; I: Interner)]
 pub struct Probe<I: Interner> {
     /// What happened inside of this probe in chronological order.
     pub steps: Vec<ProbeStep<I>>,
@@ -77,9 +64,7 @@ pub struct Probe<I: Interner> {
     pub final_state: CanonicalState<I, ()>,
 }
 
-impl<I: Interner> Eq for Probe<I> {}
-
-#[derive_where(PartialEq, Hash, Debug; I: Interner)]
+#[derive_where(PartialEq, Eq, Hash, Debug; I: Interner)]
 pub enum ProbeStep<I: Interner> {
     /// We added a goal to the `EvalCtxt` which will get proven
     /// the next time `EvalCtxt::try_evaluate_added_goals` is called.
@@ -98,12 +83,10 @@ pub enum ProbeStep<I: Interner> {
     MakeCanonicalResponse { shallow_certainty: Certainty },
 }
 
-impl<I: Interner> Eq for ProbeStep<I> {}
-
 /// What kind of probe we're in. In case the probe represents a candidate, or
 /// the final result of the current goal - via [ProbeKind::Root] - we also
 /// store the [QueryResult].
-#[derive_where(Clone, Copy, PartialEq, Hash, Debug; I: Interner)]
+#[derive_where(Clone, Copy, PartialEq, Eq, Hash, Debug; I: Interner)]
 #[derive(TypeVisitable_Generic, TypeFoldable_Generic)]
 pub enum ProbeKind<I: Interner> {
     /// The root inference context while proving a goal.
@@ -128,5 +111,3 @@ pub enum ProbeKind<I: Interner> {
     /// Checking that a rigid alias is well-formed.
     RigidAlias { result: QueryResult<I> },
 }
-
-impl<I: Interner> Eq for ProbeKind<I> {}
diff --git a/compiler/rustc_type_ir_macros/Cargo.toml b/compiler/rustc_type_ir_macros/Cargo.toml
index 29a2cc89033..15a55575099 100644
--- a/compiler/rustc_type_ir_macros/Cargo.toml
+++ b/compiler/rustc_type_ir_macros/Cargo.toml
@@ -8,8 +8,8 @@ proc-macro = true
 
 [dependencies]
 # tidy-alphabetical-start
-proc-macro2.workspace = true
-quote.workspace = true
+proc-macro2 = "1"
+quote = "1"
 syn = { version = "2.0.9", features = ["full"] }
 synstructure = "0.13.0"
 # tidy-alphabetical-end