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-rw-r--r--compiler/rustc_abi/src/callconv/reg.rs22
-rw-r--r--compiler/rustc_abi/src/layout.rs71
-rw-r--r--compiler/rustc_abi/src/layout/simple.rs27
-rw-r--r--compiler/rustc_abi/src/lib.rs87
-rw-r--r--compiler/rustc_ast/src/ast.rs3
-rw-r--r--compiler/rustc_ast/src/expand/autodiff_attrs.rs17
-rw-r--r--compiler/rustc_ast/src/expand/typetree.rs1
-rw-r--r--compiler/rustc_ast/src/lib.rs1
-rw-r--r--compiler/rustc_ast/src/tokenstream.rs4
-rw-r--r--compiler/rustc_ast_lowering/src/format.rs20
-rw-r--r--compiler/rustc_ast_passes/src/feature_gate.rs2
-rw-r--r--compiler/rustc_attr_parsing/messages.ftl10
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/debugger.rs60
-rw-r--r--compiler/rustc_attr_parsing/src/attributes/mod.rs1
-rw-r--r--compiler/rustc_attr_parsing/src/context.rs9
-rw-r--r--compiler/rustc_attr_parsing/src/lints.rs18
-rw-r--r--compiler/rustc_attr_parsing/src/parser.rs2
-rw-r--r--compiler/rustc_attr_parsing/src/session_diagnostics.rs3
-rw-r--r--compiler/rustc_borrowck/src/borrowck_errors.rs4
-rw-r--r--compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs8
-rw-r--r--compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs20
-rw-r--r--compiler/rustc_borrowck/src/lib.rs4
-rw-r--r--compiler/rustc_borrowck/src/region_infer/mod.rs4
-rw-r--r--compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs76
-rw-r--r--compiler/rustc_borrowck/src/root_cx.rs22
-rw-r--r--compiler/rustc_builtin_macros/src/autodiff.rs3
-rw-r--r--compiler/rustc_builtin_macros/src/deriving/coerce_pointee.rs15
-rw-r--r--compiler/rustc_builtin_macros/src/format.rs2
-rw-r--r--compiler/rustc_builtin_macros/src/lib.rs1
-rw-r--r--compiler/rustc_codegen_cranelift/src/abi/comments.rs2
-rw-r--r--compiler/rustc_codegen_cranelift/src/abi/pass_mode.rs2
-rw-r--r--compiler/rustc_codegen_cranelift/src/base.rs2
-rw-r--r--compiler/rustc_codegen_cranelift/src/debuginfo/mod.rs2
-rw-r--r--compiler/rustc_codegen_cranelift/src/debuginfo/types.rs6
-rw-r--r--compiler/rustc_codegen_cranelift/src/lib.rs4
-rw-r--r--compiler/rustc_codegen_cranelift/src/unsize.rs6
-rw-r--r--compiler/rustc_codegen_cranelift/src/value_and_place.rs6
-rw-r--r--compiler/rustc_codegen_gcc/src/builder.rs1
-rw-r--r--compiler/rustc_codegen_gcc/src/context.rs6
-rw-r--r--compiler/rustc_codegen_gcc/src/intrinsic/mod.rs1
-rw-r--r--compiler/rustc_codegen_gcc/src/lib.rs4
-rw-r--r--compiler/rustc_codegen_llvm/src/abi.rs9
-rw-r--r--compiler/rustc_codegen_llvm/src/allocator.rs49
-rw-r--r--compiler/rustc_codegen_llvm/src/attributes.rs191
-rw-r--r--compiler/rustc_codegen_llvm/src/back/lto.rs2
-rw-r--r--compiler/rustc_codegen_llvm/src/base.rs2
-rw-r--r--compiler/rustc_codegen_llvm/src/builder.rs17
-rw-r--r--compiler/rustc_codegen_llvm/src/builder/autodiff.rs15
-rw-r--r--compiler/rustc_codegen_llvm/src/consts.rs4
-rw-r--r--compiler/rustc_codegen_llvm/src/context.rs16
-rw-r--r--compiler/rustc_codegen_llvm/src/coverageinfo/llvm_cov.rs15
-rw-r--r--compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs2
-rw-r--r--compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs12
-rw-r--r--compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/native.rs4
-rw-r--r--compiler/rustc_codegen_llvm/src/debuginfo/mod.rs81
-rw-r--r--compiler/rustc_codegen_llvm/src/debuginfo/utils.rs2
-rw-r--r--compiler/rustc_codegen_llvm/src/declare.rs2
-rw-r--r--compiler/rustc_codegen_llvm/src/intrinsic.rs8
-rw-r--r--compiler/rustc_codegen_llvm/src/lib.rs14
-rw-r--r--compiler/rustc_codegen_llvm/src/llvm/enzyme_ffi.rs206
-rw-r--r--compiler/rustc_codegen_llvm/src/llvm/ffi.rs169
-rw-r--r--compiler/rustc_codegen_llvm/src/llvm/metadata_kind.rs71
-rw-r--r--compiler/rustc_codegen_llvm/src/llvm/mod.rs3
-rw-r--r--compiler/rustc_codegen_llvm/src/type_.rs8
-rw-r--r--compiler/rustc_codegen_llvm/src/typetree.rs122
-rw-r--r--compiler/rustc_codegen_llvm/src/va_arg.rs13
-rw-r--r--compiler/rustc_codegen_ssa/src/back/link.rs6
-rw-r--r--compiler/rustc_codegen_ssa/src/back/linker.rs13
-rw-r--r--compiler/rustc_codegen_ssa/src/base.rs4
-rw-r--r--compiler/rustc_codegen_ssa/src/mir/block.rs1
-rw-r--r--compiler/rustc_codegen_ssa/src/mir/intrinsic.rs2
-rw-r--r--compiler/rustc_codegen_ssa/src/mir/rvalue.rs2
-rw-r--r--compiler/rustc_codegen_ssa/src/mir/statement.rs2
-rw-r--r--compiler/rustc_codegen_ssa/src/size_of_val.rs8
-rw-r--r--compiler/rustc_codegen_ssa/src/traits/backend.rs11
-rw-r--r--compiler/rustc_codegen_ssa/src/traits/builder.rs3
-rw-r--r--compiler/rustc_const_eval/src/interpret/operator.rs2
-rw-r--r--compiler/rustc_const_eval/src/lib.rs1
-rw-r--r--compiler/rustc_const_eval/src/util/alignment.rs2
-rw-r--r--compiler/rustc_const_eval/src/util/caller_location.rs2
-rw-r--r--compiler/rustc_const_eval/src/util/check_validity_requirement.rs2
-rw-r--r--compiler/rustc_error_codes/src/error_codes/E0719.md14
-rw-r--r--compiler/rustc_expand/src/base.rs23
-rw-r--r--compiler/rustc_expand/src/expand.rs2
-rw-r--r--compiler/rustc_expand/src/mbe/macro_check.rs11
-rw-r--r--compiler/rustc_expand/src/mbe/macro_rules.rs28
-rw-r--r--compiler/rustc_feature/src/accepted.rs6
-rw-r--r--compiler/rustc_feature/src/removed.rs8
-rw-r--r--compiler/rustc_feature/src/unstable.rs22
-rw-r--r--compiler/rustc_hir/src/attrs/data_structures.rs19
-rw-r--r--compiler/rustc_hir/src/attrs/encode_cross_crate.rs1
-rw-r--r--compiler/rustc_hir/src/hir.rs5
-rw-r--r--compiler/rustc_hir/src/lang_items.rs1
-rw-r--r--compiler/rustc_hir/src/lints.rs15
-rw-r--r--compiler/rustc_hir_analysis/src/check/check.rs4
-rw-r--r--compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs9
-rw-r--r--compiler/rustc_hir_analysis/src/coherence/orphan.rs10
-rw-r--r--compiler/rustc_hir_analysis/src/collect.rs4
-rw-r--r--compiler/rustc_hir_analysis/src/collect/item_bounds.rs20
-rw-r--r--compiler/rustc_hir_analysis/src/collect/predicates_of.rs18
-rw-r--r--compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs12
-rw-r--r--compiler/rustc_hir_analysis/src/constrained_generic_params.rs55
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs32
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/cmse.rs3
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_trait.rs10
-rw-r--r--compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs18
-rw-r--r--compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs2
-rw-r--r--compiler/rustc_hir_typeck/src/expr.rs3
-rw-r--r--compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs18
-rw-r--r--compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs4
-rw-r--r--compiler/rustc_hir_typeck/src/lib.rs10
-rw-r--r--compiler/rustc_hir_typeck/src/method/confirm.rs4
-rw-r--r--compiler/rustc_hir_typeck/src/method/probe.rs267
-rw-r--r--compiler/rustc_hir_typeck/src/method/suggest.rs4
-rw-r--r--compiler/rustc_hir_typeck/src/opaque_types.rs19
-rw-r--r--compiler/rustc_hir_typeck/src/writeback.rs28
-rw-r--r--compiler/rustc_index/src/idx.rs6
-rw-r--r--compiler/rustc_infer/src/infer/canonical/query_response.rs20
-rw-r--r--compiler/rustc_infer/src/infer/mod.rs17
-rw-r--r--compiler/rustc_infer/src/infer/outlives/obligations.rs4
-rw-r--r--compiler/rustc_interface/src/passes.rs26
-rw-r--r--compiler/rustc_interface/src/tests.rs2
-rw-r--r--compiler/rustc_interface/src/util.rs76
-rw-r--r--compiler/rustc_lint_defs/src/builtin.rs11
-rw-r--r--compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp18
-rw-r--r--compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp117
-rw-r--r--compiler/rustc_macros/src/query.rs2
-rw-r--r--compiler/rustc_metadata/src/rmeta/decoder.rs2
-rw-r--r--compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs4
-rw-r--r--compiler/rustc_metadata/src/rmeta/def_path_hash_map.rs9
-rw-r--r--compiler/rustc_middle/src/arena.rs3
-rw-r--r--compiler/rustc_middle/src/error.rs1
-rw-r--r--compiler/rustc_middle/src/hooks/mod.rs2
-rw-r--r--compiler/rustc_middle/src/lib.rs1
-rw-r--r--compiler/rustc_middle/src/middle/debugger_visualizer.rs8
-rw-r--r--compiler/rustc_middle/src/mir/query.rs7
-rw-r--r--compiler/rustc_middle/src/query/mod.rs8
-rw-r--r--compiler/rustc_middle/src/traits/query.rs13
-rw-r--r--compiler/rustc_middle/src/traits/solve.rs45
-rw-r--r--compiler/rustc_middle/src/ty/context.rs19
-rw-r--r--compiler/rustc_middle/src/ty/mod.rs225
-rw-r--r--compiler/rustc_middle/src/ty/structural_impls.rs1
-rw-r--r--compiler/rustc_middle/src/ty/typeck_results.rs4
-rw-r--r--compiler/rustc_middle/src/ty/vtable.rs2
-rw-r--r--compiler/rustc_mir_build/src/builder/mod.rs6
-rw-r--r--compiler/rustc_mir_build/src/check_unsafety.rs15
-rw-r--r--compiler/rustc_mir_build/src/thir/pattern/check_match.rs8
-rw-r--r--compiler/rustc_mir_transform/src/abort_unwinding_calls.rs37
-rw-r--r--compiler/rustc_mir_transform/src/dataflow_const_prop.rs2
-rw-r--r--compiler/rustc_mir_transform/src/gvn.rs2
-rw-r--r--compiler/rustc_mir_transform/src/jump_threading.rs42
-rw-r--r--compiler/rustc_mir_transform/src/known_panics_lint.rs2
-rw-r--r--compiler/rustc_mir_transform/src/patch.rs30
-rw-r--r--compiler/rustc_mir_transform/src/simplify_branches.rs19
-rw-r--r--compiler/rustc_next_trait_solver/src/canonical/mod.rs8
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs5
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs5
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/effect_goals.rs21
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs29
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/mod.rs1
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs135
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/search_graph.rs26
-rw-r--r--compiler/rustc_next_trait_solver/src/solve/trait_goals.rs46
-rw-r--r--compiler/rustc_parse/src/lib.rs1
-rw-r--r--compiler/rustc_parse/src/parser/tokenstream/tests.rs2
-rw-r--r--compiler/rustc_passes/messages.ftl22
-rw-r--r--compiler/rustc_passes/src/check_attr.rs87
-rw-r--r--compiler/rustc_passes/src/debugger_visualizer.rs113
-rw-r--r--compiler/rustc_passes/src/errors.rs37
-rw-r--r--compiler/rustc_pattern_analysis/src/rustc.rs4
-rw-r--r--compiler/rustc_privacy/src/lib.rs22
-rw-r--r--compiler/rustc_resolve/src/build_reduced_graph.rs19
-rw-r--r--compiler/rustc_resolve/src/ident.rs44
-rw-r--r--compiler/rustc_resolve/src/imports.rs26
-rw-r--r--compiler/rustc_resolve/src/late/diagnostics.rs99
-rw-r--r--compiler/rustc_resolve/src/lib.rs134
-rw-r--r--compiler/rustc_resolve/src/macros.rs2
-rw-r--r--compiler/rustc_session/src/config.rs14
-rw-r--r--compiler/rustc_session/src/config/cfg.rs10
-rw-r--r--compiler/rustc_session/src/options.rs5
-rw-r--r--compiler/rustc_span/src/analyze_source_file.rs109
-rw-r--r--compiler/rustc_span/src/lib.rs2
-rw-r--r--compiler/rustc_span/src/symbol.rs6
-rw-r--r--compiler/rustc_target/src/callconv/arm.rs2
-rw-r--r--compiler/rustc_target/src/callconv/loongarch.rs2
-rw-r--r--compiler/rustc_target/src/callconv/mips.rs2
-rw-r--r--compiler/rustc_target/src/callconv/mips64.rs4
-rw-r--r--compiler/rustc_target/src/callconv/mod.rs2
-rw-r--r--compiler/rustc_target/src/callconv/nvptx64.rs4
-rw-r--r--compiler/rustc_target/src/callconv/powerpc64.rs2
-rw-r--r--compiler/rustc_target/src/callconv/riscv.rs2
-rw-r--r--compiler/rustc_target/src/callconv/sparc.rs2
-rw-r--r--compiler/rustc_target/src/callconv/sparc64.rs2
-rw-r--r--compiler/rustc_target/src/callconv/xtensa.rs2
-rw-r--r--compiler/rustc_target/src/spec/base/apple/mod.rs16
-rw-r--r--compiler/rustc_target/src/spec/base/windows_gnu.rs3
-rw-r--r--compiler/rustc_target/src/spec/crt_objects.rs17
-rw-r--r--compiler/rustc_target/src/spec/targets/armebv7r_none_eabi.rs2
-rw-r--r--compiler/rustc_target/src/spec/targets/armebv7r_none_eabihf.rs2
-rw-r--r--compiler/rustc_target/src/spec/targets/i686_pc_windows_gnu.rs8
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs17
-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/traits/mod.rs45
-rw-r--r--compiler/rustc_trait_selection/src/infer.rs14
-rw-r--r--compiler/rustc_trait_selection/src/regions.rs2
-rw-r--r--compiler/rustc_trait_selection/src/traits/query/evaluate_obligation.rs11
-rw-r--r--compiler/rustc_trait_selection/src/traits/query/type_op/implied_outlives_bounds.rs8
-rw-r--r--compiler/rustc_trait_selection/src/traits/select/mod.rs2
-rw-r--r--compiler/rustc_transmute/src/layout/tree.rs2
-rw-r--r--compiler/rustc_ty_utils/src/layout.rs10
-rw-r--r--compiler/rustc_ty_utils/src/layout/invariant.rs6
-rw-r--r--compiler/rustc_type_ir/src/flags.rs1
-rw-r--r--compiler/rustc_type_ir/src/infer_ctxt.rs2
-rw-r--r--compiler/rustc_type_ir/src/interner.rs8
-rw-r--r--compiler/rustc_type_ir/src/search_graph/mod.rs148
-rw-r--r--compiler/rustc_type_ir/src/solve/mod.rs13
215 files changed, 3053 insertions, 1526 deletions
diff --git a/compiler/rustc_abi/src/callconv/reg.rs b/compiler/rustc_abi/src/callconv/reg.rs
index 8cf140dbaad..66c8056d0c2 100644
--- a/compiler/rustc_abi/src/callconv/reg.rs
+++ b/compiler/rustc_abi/src/callconv/reg.rs
@@ -42,22 +42,22 @@ impl Reg {
         let dl = cx.data_layout();
         match self.kind {
             RegKind::Integer => match self.size.bits() {
-                1 => dl.i1_align.abi,
-                2..=8 => dl.i8_align.abi,
-                9..=16 => dl.i16_align.abi,
-                17..=32 => dl.i32_align.abi,
-                33..=64 => dl.i64_align.abi,
-                65..=128 => dl.i128_align.abi,
+                1 => dl.i1_align,
+                2..=8 => dl.i8_align,
+                9..=16 => dl.i16_align,
+                17..=32 => dl.i32_align,
+                33..=64 => dl.i64_align,
+                65..=128 => dl.i128_align,
                 _ => panic!("unsupported integer: {self:?}"),
             },
             RegKind::Float => match self.size.bits() {
-                16 => dl.f16_align.abi,
-                32 => dl.f32_align.abi,
-                64 => dl.f64_align.abi,
-                128 => dl.f128_align.abi,
+                16 => dl.f16_align,
+                32 => dl.f32_align,
+                64 => dl.f64_align,
+                128 => dl.f128_align,
                 _ => panic!("unsupported float: {self:?}"),
             },
-            RegKind::Vector => dl.llvmlike_vector_align(self.size).abi,
+            RegKind::Vector => dl.llvmlike_vector_align(self.size),
         }
     }
 }
diff --git a/compiler/rustc_abi/src/layout.rs b/compiler/rustc_abi/src/layout.rs
index 5004d0c8022..14356813b7b 100644
--- a/compiler/rustc_abi/src/layout.rs
+++ b/compiler/rustc_abi/src/layout.rs
@@ -174,11 +174,11 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
             // Non-power-of-two vectors have padding up to the next power-of-two.
             // If we're a packed repr, remove the padding while keeping the alignment as close
             // to a vector as possible.
-            (BackendRepr::Memory { sized: true }, AbiAlign { abi: Align::max_aligned_factor(size) })
+            (BackendRepr::Memory { sized: true }, Align::max_aligned_factor(size))
         } else {
             (BackendRepr::SimdVector { element: e_repr, count }, dl.llvmlike_vector_align(size))
         };
-        let size = size.align_to(align.abi);
+        let size = size.align_to(align);
 
         Ok(LayoutData {
             variants: Variants::Single { index: VariantIdx::new(0) },
@@ -190,7 +190,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
             largest_niche: elt.largest_niche,
             uninhabited: false,
             size,
-            align,
+            align: AbiAlign::new(align),
             max_repr_align: None,
             unadjusted_abi_align: elt.align.abi,
             randomization_seed: elt.randomization_seed.wrapping_add(Hash64::new(count)),
@@ -388,7 +388,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
                 return Err(LayoutCalculatorError::UnexpectedUnsized(*field));
             }
 
-            align = align.max(field.align);
+            align = align.max(field.align.abi);
             max_repr_align = max_repr_align.max(field.max_repr_align);
             size = cmp::max(size, field.size);
 
@@ -423,13 +423,13 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
         }
 
         if let Some(pack) = repr.pack {
-            align = align.min(AbiAlign::new(pack));
+            align = align.min(pack);
         }
         // The unadjusted ABI alignment does not include repr(align), but does include repr(pack).
         // See documentation on `LayoutData::unadjusted_abi_align`.
-        let unadjusted_abi_align = align.abi;
+        let unadjusted_abi_align = align;
         if let Some(repr_align) = repr.align {
-            align = align.max(AbiAlign::new(repr_align));
+            align = align.max(repr_align);
         }
         // `align` must not be modified after this, or `unadjusted_abi_align` could be inaccurate.
         let align = align;
@@ -441,14 +441,12 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
             Ok(Some((repr, _))) => match repr {
                 // Mismatched alignment (e.g. union is #[repr(packed)]): disable opt
                 BackendRepr::Scalar(_) | BackendRepr::ScalarPair(_, _)
-                    if repr.scalar_align(dl).unwrap() != align.abi =>
+                    if repr.scalar_align(dl).unwrap() != align =>
                 {
                     BackendRepr::Memory { sized: true }
                 }
                 // Vectors require at least element alignment, else disable the opt
-                BackendRepr::SimdVector { element, count: _ }
-                    if element.align(dl).abi > align.abi =>
-                {
+                BackendRepr::SimdVector { element, count: _ } if element.align(dl).abi > align => {
                     BackendRepr::Memory { sized: true }
                 }
                 // the alignment tests passed and we can use this
@@ -474,8 +472,8 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
             backend_repr,
             largest_niche: None,
             uninhabited: false,
-            align,
-            size: size.align_to(align.abi),
+            align: AbiAlign::new(align),
+            size: size.align_to(align),
             max_repr_align,
             unadjusted_abi_align,
             randomization_seed: combined_seed,
@@ -611,7 +609,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
 
             let mut align = dl.aggregate_align;
             let mut max_repr_align = repr.align;
-            let mut unadjusted_abi_align = align.abi;
+            let mut unadjusted_abi_align = align;
 
             let mut variant_layouts = variants
                 .iter_enumerated()
@@ -619,7 +617,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
                     let mut st = self.univariant(v, repr, StructKind::AlwaysSized).ok()?;
                     st.variants = Variants::Single { index: j };
 
-                    align = align.max(st.align);
+                    align = align.max(st.align.abi);
                     max_repr_align = max_repr_align.max(st.max_repr_align);
                     unadjusted_abi_align = unadjusted_abi_align.max(st.unadjusted_abi_align);
 
@@ -646,7 +644,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
             let (niche_start, niche_scalar) = niche.reserve(dl, count)?;
             let niche_offset = niche.offset;
             let niche_size = niche.value.size(dl);
-            let size = variant_layouts[largest_variant_index].size.align_to(align.abi);
+            let size = variant_layouts[largest_variant_index].size.align_to(align);
 
             let all_variants_fit = variant_layouts.iter_enumerated_mut().all(|(i, layout)| {
                 if i == largest_variant_index {
@@ -699,7 +697,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
                 .iter_enumerated()
                 .all(|(i, layout)| i == largest_variant_index || layout.size == Size::ZERO);
             let same_size = size == variant_layouts[largest_variant_index].size;
-            let same_align = align == variant_layouts[largest_variant_index].align;
+            let same_align = align == variant_layouts[largest_variant_index].align.abi;
 
             let uninhabited = variant_layouts.iter().all(|v| v.is_uninhabited());
             let abi = if same_size && same_align && others_zst {
@@ -746,7 +744,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
                 largest_niche,
                 uninhabited,
                 size,
-                align,
+                align: AbiAlign::new(align),
                 max_repr_align,
                 unadjusted_abi_align,
                 randomization_seed: combined_seed,
@@ -818,7 +816,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
 
         let mut align = dl.aggregate_align;
         let mut max_repr_align = repr.align;
-        let mut unadjusted_abi_align = align.abi;
+        let mut unadjusted_abi_align = align;
 
         let mut size = Size::ZERO;
 
@@ -860,7 +858,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
                     }
                 }
                 size = cmp::max(size, st.size);
-                align = align.max(st.align);
+                align = align.max(st.align.abi);
                 max_repr_align = max_repr_align.max(st.max_repr_align);
                 unadjusted_abi_align = unadjusted_abi_align.max(st.unadjusted_abi_align);
                 Ok(st)
@@ -868,7 +866,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
             .collect::<Result<IndexVec<VariantIdx, _>, _>>()?;
 
         // Align the maximum variant size to the largest alignment.
-        size = size.align_to(align.abi);
+        size = size.align_to(align);
 
         // FIXME(oli-obk): deduplicate and harden these checks
         if size.bytes() >= dl.obj_size_bound() {
@@ -1042,7 +1040,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
                 };
                 if pair_offsets[FieldIdx::new(0)] == Size::ZERO
                     && pair_offsets[FieldIdx::new(1)] == *offset
-                    && align == pair.align
+                    && align == pair.align.abi
                     && size == pair.size
                 {
                     // We can use `ScalarPair` only when it matches our
@@ -1066,7 +1064,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
                     // Also need to bump up the size and alignment, so that the entire value fits
                     // in here.
                     variant.size = cmp::max(variant.size, size);
-                    variant.align.abi = cmp::max(variant.align.abi, align.abi);
+                    variant.align.abi = cmp::max(variant.align.abi, align);
                 }
             }
         }
@@ -1092,7 +1090,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
             largest_niche,
             uninhabited,
             backend_repr: abi,
-            align,
+            align: AbiAlign::new(align),
             size,
             max_repr_align,
             unadjusted_abi_align,
@@ -1169,7 +1167,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
                 // To allow unsizing `&Foo<Type>` -> `&Foo<dyn Trait>`, the layout of the struct must
                 // not depend on the layout of the tail.
                 let max_field_align =
-                    fields_excluding_tail.iter().map(|f| f.align.abi.bytes()).max().unwrap_or(1);
+                    fields_excluding_tail.iter().map(|f| f.align.bytes()).max().unwrap_or(1);
                 let largest_niche_size = fields_excluding_tail
                     .iter()
                     .filter_map(|f| f.largest_niche)
@@ -1189,7 +1187,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
                     } else {
                         // Returns `log2(effective-align)`. The calculation assumes that size is an
                         // integer multiple of align, except for ZSTs.
-                        let align = layout.align.abi.bytes();
+                        let align = layout.align.bytes();
                         let size = layout.size.bytes();
                         let niche_size = layout.largest_niche.map(|n| n.available(dl)).unwrap_or(0);
                         // Group [u8; 4] with align-4 or [u8; 6] with align-2 fields.
@@ -1288,7 +1286,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
         if let StructKind::Prefixed(prefix_size, prefix_align) = kind {
             let prefix_align =
                 if let Some(pack) = pack { prefix_align.min(pack) } else { prefix_align };
-            align = align.max(AbiAlign::new(prefix_align));
+            align = align.max(prefix_align);
             offset = prefix_size.align_to(prefix_align);
         }
         for &i in &inverse_memory_index {
@@ -1312,7 +1310,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
                 field.align
             };
             offset = offset.align_to(field_align.abi);
-            align = align.max(field_align);
+            align = align.max(field_align.abi);
             max_repr_align = max_repr_align.max(field.max_repr_align);
 
             debug!("univariant offset: {:?} field: {:#?}", offset, field);
@@ -1339,9 +1337,9 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
 
         // The unadjusted ABI alignment does not include repr(align), but does include repr(pack).
         // See documentation on `LayoutData::unadjusted_abi_align`.
-        let unadjusted_abi_align = align.abi;
+        let unadjusted_abi_align = align;
         if let Some(repr_align) = repr.align {
-            align = align.max(AbiAlign::new(repr_align));
+            align = align.max(repr_align);
         }
         // `align` must not be modified after this point, or `unadjusted_abi_align` could be inaccurate.
         let align = align;
@@ -1360,7 +1358,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
             debug_assert!(inverse_memory_index.iter().copied().eq(fields.indices()));
             inverse_memory_index.into_iter().map(|it| it.index() as u32).collect()
         };
-        let size = min_size.align_to(align.abi);
+        let size = min_size.align_to(align);
         // FIXME(oli-obk): deduplicate and harden these checks
         if size.bytes() >= dl.obj_size_bound() {
             return Err(LayoutCalculatorError::SizeOverflow);
@@ -1383,8 +1381,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
                     layout_of_single_non_zst_field = Some(field);
 
                     // Field fills the struct and it has a scalar or scalar pair ABI.
-                    if offsets[i].bytes() == 0 && align.abi == field.align.abi && size == field.size
-                    {
+                    if offsets[i].bytes() == 0 && align == field.align.abi && size == field.size {
                         match field.backend_repr {
                             // For plain scalars, or vectors of them, we can't unpack
                             // newtypes for `#[repr(C)]`, as that affects C ABIs.
@@ -1428,7 +1425,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
                             };
                             if offsets[i] == pair_offsets[FieldIdx::new(0)]
                                 && offsets[j] == pair_offsets[FieldIdx::new(1)]
-                                && align == pair.align
+                                && align == pair.align.abi
                                 && size == pair.size
                             {
                                 // We can use `ScalarPair` only when it matches our
@@ -1450,7 +1447,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
                 Some(l) => l.unadjusted_abi_align,
                 None => {
                     // `repr(transparent)` with all ZST fields.
-                    align.abi
+                    align
                 }
             }
         } else {
@@ -1465,7 +1462,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
             backend_repr: abi,
             largest_niche,
             uninhabited,
-            align,
+            align: AbiAlign::new(align),
             size,
             max_repr_align,
             unadjusted_abi_align,
@@ -1488,7 +1485,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
         for i in layout.fields.index_by_increasing_offset() {
             let offset = layout.fields.offset(i);
             let f = &fields[FieldIdx::new(i)];
-            write!(s, "[o{}a{}s{}", offset.bytes(), f.align.abi.bytes(), f.size.bytes()).unwrap();
+            write!(s, "[o{}a{}s{}", offset.bytes(), f.align.bytes(), f.size.bytes()).unwrap();
             if let Some(n) = f.largest_niche {
                 write!(
                     s,
diff --git a/compiler/rustc_abi/src/layout/simple.rs b/compiler/rustc_abi/src/layout/simple.rs
index 0d0706defc2..b3807c87273 100644
--- a/compiler/rustc_abi/src/layout/simple.rs
+++ b/compiler/rustc_abi/src/layout/simple.rs
@@ -4,7 +4,8 @@ use rustc_hashes::Hash64;
 use rustc_index::{Idx, IndexVec};
 
 use crate::{
-    BackendRepr, FieldsShape, HasDataLayout, LayoutData, Niche, Primitive, Scalar, Size, Variants,
+    AbiAlign, BackendRepr, FieldsShape, HasDataLayout, LayoutData, Niche, Primitive, Scalar, Size,
+    Variants,
 };
 
 /// "Simple" layout constructors that cannot fail.
@@ -20,10 +21,10 @@ impl<FieldIdx: Idx, VariantIdx: Idx> LayoutData<FieldIdx, VariantIdx> {
             backend_repr: BackendRepr::Memory { sized },
             largest_niche: None,
             uninhabited: false,
-            align: dl.i8_align,
+            align: AbiAlign::new(dl.i8_align),
             size: Size::ZERO,
             max_repr_align: None,
-            unadjusted_abi_align: dl.i8_align.abi,
+            unadjusted_abi_align: dl.i8_align,
             randomization_seed: Hash64::new(0),
         }
     }
@@ -37,10 +38,10 @@ impl<FieldIdx: Idx, VariantIdx: Idx> LayoutData<FieldIdx, VariantIdx> {
             backend_repr: BackendRepr::Memory { sized: true },
             largest_niche: None,
             uninhabited: true,
-            align: dl.i8_align,
+            align: AbiAlign::new(dl.i8_align),
             size: Size::ZERO,
             max_repr_align: None,
-            unadjusted_abi_align: dl.i8_align.abi,
+            unadjusted_abi_align: dl.i8_align,
             randomization_seed: Hash64::ZERO,
         }
     }
@@ -89,10 +90,10 @@ impl<FieldIdx: Idx, VariantIdx: Idx> LayoutData<FieldIdx, VariantIdx> {
 
     pub fn scalar_pair<C: HasDataLayout>(cx: &C, a: Scalar, b: Scalar) -> Self {
         let dl = cx.data_layout();
-        let b_align = b.align(dl);
-        let align = a.align(dl).max(b_align).max(dl.aggregate_align);
-        let b_offset = a.size(dl).align_to(b_align.abi);
-        let size = (b_offset + b.size(dl)).align_to(align.abi);
+        let b_align = b.align(dl).abi;
+        let align = a.align(dl).abi.max(b_align).max(dl.aggregate_align);
+        let b_offset = a.size(dl).align_to(b_align);
+        let size = (b_offset + b.size(dl)).align_to(align);
 
         // HACK(nox): We iter on `b` and then `a` because `max_by_key`
         // returns the last maximum.
@@ -112,10 +113,10 @@ impl<FieldIdx: Idx, VariantIdx: Idx> LayoutData<FieldIdx, VariantIdx> {
             backend_repr: BackendRepr::ScalarPair(a, b),
             largest_niche,
             uninhabited: false,
-            align,
+            align: AbiAlign::new(align),
             size,
             max_repr_align: None,
-            unadjusted_abi_align: align.abi,
+            unadjusted_abi_align: align,
             randomization_seed: Hash64::new(combined_seed),
         }
     }
@@ -138,10 +139,10 @@ impl<FieldIdx: Idx, VariantIdx: Idx> LayoutData<FieldIdx, VariantIdx> {
             backend_repr: BackendRepr::Memory { sized: true },
             largest_niche: None,
             uninhabited: true,
-            align: dl.i8_align,
+            align: AbiAlign::new(dl.i8_align),
             size: Size::ZERO,
             max_repr_align: None,
-            unadjusted_abi_align: dl.i8_align.abi,
+            unadjusted_abi_align: dl.i8_align,
             randomization_seed: Hash64::ZERO,
         }
     }
diff --git a/compiler/rustc_abi/src/lib.rs b/compiler/rustc_abi/src/lib.rs
index 369874521e5..de44c8755a0 100644
--- a/compiler/rustc_abi/src/lib.rs
+++ b/compiler/rustc_abi/src/lib.rs
@@ -229,7 +229,7 @@ pub struct PointerSpec {
     /// The size of the bitwise representation of the pointer.
     pointer_size: Size,
     /// The alignment of pointers for this address space
-    pointer_align: AbiAlign,
+    pointer_align: Align,
     /// The size of the value a pointer can be offset by in this address space.
     pointer_offset: Size,
     /// Pointers into this address space contain extra metadata
@@ -242,20 +242,20 @@ pub struct PointerSpec {
 #[derive(Debug, PartialEq, Eq)]
 pub struct TargetDataLayout {
     pub endian: Endian,
-    pub i1_align: AbiAlign,
-    pub i8_align: AbiAlign,
-    pub i16_align: AbiAlign,
-    pub i32_align: AbiAlign,
-    pub i64_align: AbiAlign,
-    pub i128_align: AbiAlign,
-    pub f16_align: AbiAlign,
-    pub f32_align: AbiAlign,
-    pub f64_align: AbiAlign,
-    pub f128_align: AbiAlign,
-    pub aggregate_align: AbiAlign,
+    pub i1_align: Align,
+    pub i8_align: Align,
+    pub i16_align: Align,
+    pub i32_align: Align,
+    pub i64_align: Align,
+    pub i128_align: Align,
+    pub f16_align: Align,
+    pub f32_align: Align,
+    pub f64_align: Align,
+    pub f128_align: Align,
+    pub aggregate_align: Align,
 
     /// Alignments for vector types.
-    pub vector_align: Vec<(Size, AbiAlign)>,
+    pub vector_align: Vec<(Size, Align)>,
 
     pub default_address_space: AddressSpace,
     pub default_address_space_pointer_spec: PointerSpec,
@@ -282,25 +282,25 @@ impl Default for TargetDataLayout {
         let align = |bits| Align::from_bits(bits).unwrap();
         TargetDataLayout {
             endian: Endian::Big,
-            i1_align: AbiAlign::new(align(8)),
-            i8_align: AbiAlign::new(align(8)),
-            i16_align: AbiAlign::new(align(16)),
-            i32_align: AbiAlign::new(align(32)),
-            i64_align: AbiAlign::new(align(32)),
-            i128_align: AbiAlign::new(align(32)),
-            f16_align: AbiAlign::new(align(16)),
-            f32_align: AbiAlign::new(align(32)),
-            f64_align: AbiAlign::new(align(64)),
-            f128_align: AbiAlign::new(align(128)),
-            aggregate_align: AbiAlign { abi: align(8) },
+            i1_align: align(8),
+            i8_align: align(8),
+            i16_align: align(16),
+            i32_align: align(32),
+            i64_align: align(32),
+            i128_align: align(32),
+            f16_align: align(16),
+            f32_align: align(32),
+            f64_align: align(64),
+            f128_align: align(128),
+            aggregate_align: align(8),
             vector_align: vec![
-                (Size::from_bits(64), AbiAlign::new(align(64))),
-                (Size::from_bits(128), AbiAlign::new(align(128))),
+                (Size::from_bits(64), align(64)),
+                (Size::from_bits(128), align(128)),
             ],
             default_address_space: AddressSpace::ZERO,
             default_address_space_pointer_spec: PointerSpec {
                 pointer_size: Size::from_bits(64),
-                pointer_align: AbiAlign::new(align(64)),
+                pointer_align: align(64),
                 pointer_offset: Size::from_bits(64),
                 _is_fat: false,
             },
@@ -360,7 +360,7 @@ impl TargetDataLayout {
                     .map_err(|err| TargetDataLayoutErrors::InvalidAlignment { cause, err })
             };
             let abi = parse_bits(s, "alignment", cause)?;
-            Ok(AbiAlign::new(align_from_bits(abi)?))
+            Ok(align_from_bits(abi)?)
         };
 
         // Parse an alignment sequence, possibly in the form `<align>[:<preferred_alignment>]`,
@@ -596,7 +596,7 @@ impl TargetDataLayout {
 
     /// psABI-mandated alignment for a vector type, if any
     #[inline]
-    fn cabi_vector_align(&self, vec_size: Size) -> Option<AbiAlign> {
+    fn cabi_vector_align(&self, vec_size: Size) -> Option<Align> {
         self.vector_align
             .iter()
             .find(|(size, _align)| *size == vec_size)
@@ -605,10 +605,9 @@ impl TargetDataLayout {
 
     /// an alignment resembling the one LLVM would pick for a vector
     #[inline]
-    pub fn llvmlike_vector_align(&self, vec_size: Size) -> AbiAlign {
-        self.cabi_vector_align(vec_size).unwrap_or(AbiAlign::new(
-            Align::from_bytes(vec_size.bytes().next_power_of_two()).unwrap(),
-        ))
+    pub fn llvmlike_vector_align(&self, vec_size: Size) -> Align {
+        self.cabi_vector_align(vec_size)
+            .unwrap_or(Align::from_bytes(vec_size.bytes().next_power_of_two()).unwrap())
     }
 
     /// Get the pointer size in the default data address space.
@@ -654,21 +653,19 @@ impl TargetDataLayout {
     /// Get the pointer alignment in the default data address space.
     #[inline]
     pub fn pointer_align(&self) -> AbiAlign {
-        self.default_address_space_pointer_spec.pointer_align
+        AbiAlign::new(self.default_address_space_pointer_spec.pointer_align)
     }
 
     /// Get the pointer alignment in a specific address space.
     #[inline]
     pub fn pointer_align_in(&self, c: AddressSpace) -> AbiAlign {
-        if c == self.default_address_space {
-            return self.default_address_space_pointer_spec.pointer_align;
-        }
-
-        if let Some(e) = self.address_space_info.iter().find(|(a, _)| a == &c) {
+        AbiAlign::new(if c == self.default_address_space {
+            self.default_address_space_pointer_spec.pointer_align
+        } else if let Some(e) = self.address_space_info.iter().find(|(a, _)| a == &c) {
             e.1.pointer_align
         } else {
             panic!("Use of unknown address space {c:?}");
-        }
+        })
     }
 }
 
@@ -1185,13 +1182,13 @@ impl Integer {
         use Integer::*;
         let dl = cx.data_layout();
 
-        match self {
+        AbiAlign::new(match self {
             I8 => dl.i8_align,
             I16 => dl.i16_align,
             I32 => dl.i32_align,
             I64 => dl.i64_align,
             I128 => dl.i128_align,
-        }
+        })
     }
 
     /// Returns the largest signed value that can be represented by this Integer.
@@ -1311,12 +1308,12 @@ impl Float {
         use Float::*;
         let dl = cx.data_layout();
 
-        match self {
+        AbiAlign::new(match self {
             F16 => dl.f16_align,
             F32 => dl.f32_align,
             F64 => dl.f64_align,
             F128 => dl.f128_align,
-        }
+        })
     }
 }
 
@@ -2159,7 +2156,7 @@ impl<FieldIdx: Idx, VariantIdx: Idx> LayoutData<FieldIdx, VariantIdx> {
 
     /// Returns `true` if the type is sized and a 1-ZST (meaning it has size 0 and alignment 1).
     pub fn is_1zst(&self) -> bool {
-        self.is_sized() && self.size.bytes() == 0 && self.align.abi.bytes() == 1
+        self.is_sized() && self.size.bytes() == 0 && self.align.bytes() == 1
     }
 
     /// Returns `true` if the type is a ZST and not unsized.
diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
index 3e8fddd9954..082d5e88ac7 100644
--- a/compiler/rustc_ast/src/ast.rs
+++ b/compiler/rustc_ast/src/ast.rs
@@ -114,8 +114,7 @@ impl PartialEq<Symbol> for Path {
 impl PartialEq<&[Symbol]> for Path {
     #[inline]
     fn eq(&self, names: &&[Symbol]) -> bool {
-        self.segments.len() == names.len()
-            && self.segments.iter().zip(names.iter()).all(|(s1, s2)| s1 == s2)
+        self.segments.iter().eq(*names)
     }
 }
 
diff --git a/compiler/rustc_ast/src/expand/autodiff_attrs.rs b/compiler/rustc_ast/src/expand/autodiff_attrs.rs
index 33451f99748..90f15753e99 100644
--- a/compiler/rustc_ast/src/expand/autodiff_attrs.rs
+++ b/compiler/rustc_ast/src/expand/autodiff_attrs.rs
@@ -6,6 +6,7 @@
 use std::fmt::{self, Display, Formatter};
 use std::str::FromStr;
 
+use crate::expand::typetree::TypeTree;
 use crate::expand::{Decodable, Encodable, HashStable_Generic};
 use crate::{Ty, TyKind};
 
@@ -84,6 +85,8 @@ pub struct AutoDiffItem {
     /// The name of the function being generated
     pub target: String,
     pub attrs: AutoDiffAttrs,
+    pub inputs: Vec<TypeTree>,
+    pub output: TypeTree,
 }
 
 #[derive(Clone, Eq, PartialEq, Encodable, Decodable, Debug, HashStable_Generic)]
@@ -275,14 +278,22 @@ impl AutoDiffAttrs {
         !matches!(self.mode, DiffMode::Error | DiffMode::Source)
     }
 
-    pub fn into_item(self, source: String, target: String) -> AutoDiffItem {
-        AutoDiffItem { source, target, attrs: self }
+    pub fn into_item(
+        self,
+        source: String,
+        target: String,
+        inputs: Vec<TypeTree>,
+        output: TypeTree,
+    ) -> AutoDiffItem {
+        AutoDiffItem { source, target, inputs, output, attrs: self }
     }
 }
 
 impl fmt::Display for AutoDiffItem {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "Differentiating {} -> {}", self.source, self.target)?;
-        write!(f, " with attributes: {:?}", self.attrs)
+        write!(f, " with attributes: {:?}", self.attrs)?;
+        write!(f, " with inputs: {:?}", self.inputs)?;
+        write!(f, " with output: {:?}", self.output)
     }
 }
diff --git a/compiler/rustc_ast/src/expand/typetree.rs b/compiler/rustc_ast/src/expand/typetree.rs
index 9a2dd2e85e0..e7b4f3aff41 100644
--- a/compiler/rustc_ast/src/expand/typetree.rs
+++ b/compiler/rustc_ast/src/expand/typetree.rs
@@ -31,6 +31,7 @@ pub enum Kind {
     Half,
     Float,
     Double,
+    F128,
     Unknown,
 }
 
diff --git a/compiler/rustc_ast/src/lib.rs b/compiler/rustc_ast/src/lib.rs
index f1951049b47..5fe218776e5 100644
--- a/compiler/rustc_ast/src/lib.rs
+++ b/compiler/rustc_ast/src/lib.rs
@@ -15,6 +15,7 @@
 #![feature(associated_type_defaults)]
 #![feature(box_patterns)]
 #![feature(if_let_guard)]
+#![feature(iter_order_by)]
 #![feature(macro_metavar_expr)]
 #![feature(rustdoc_internals)]
 #![recursion_limit = "256"]
diff --git a/compiler/rustc_ast/src/tokenstream.rs b/compiler/rustc_ast/src/tokenstream.rs
index a5d8fbfac61..4111182c3b7 100644
--- a/compiler/rustc_ast/src/tokenstream.rs
+++ b/compiler/rustc_ast/src/tokenstream.rs
@@ -48,9 +48,7 @@ impl TokenTree {
         match (self, other) {
             (TokenTree::Token(token, _), TokenTree::Token(token2, _)) => token.kind == token2.kind,
             (TokenTree::Delimited(.., delim, tts), TokenTree::Delimited(.., delim2, tts2)) => {
-                delim == delim2
-                    && tts.len() == tts2.len()
-                    && tts.iter().zip(tts2.iter()).all(|(a, b)| a.eq_unspanned(b))
+                delim == delim2 && tts.iter().eq_by(tts2.iter(), |a, b| a.eq_unspanned(b))
             }
             _ => false,
         }
diff --git a/compiler/rustc_ast_lowering/src/format.rs b/compiler/rustc_ast_lowering/src/format.rs
index ec9d26eb33f..2871430030c 100644
--- a/compiler/rustc_ast_lowering/src/format.rs
+++ b/compiler/rustc_ast_lowering/src/format.rs
@@ -487,26 +487,6 @@ fn expand_format_args<'hir>(
         // Generate:
         //     []
         (vec![], ctx.arena.alloc(ctx.expr(macsp, hir::ExprKind::Array(&[]))))
-    } else if argmap.len() == 1 && arguments.len() == 1 {
-        // Only one argument, so we don't need to make the `args` tuple.
-        //
-        // Generate:
-        //     super let args = [<core::fmt::Argument>::new_display(&arg)];
-        let args = ctx.arena.alloc_from_iter(argmap.iter().map(
-            |(&(arg_index, ty), &placeholder_span)| {
-                let arg = &arguments[arg_index];
-                let placeholder_span =
-                    placeholder_span.unwrap_or(arg.expr.span).with_ctxt(macsp.ctxt());
-                let arg = ctx.lower_expr(&arg.expr);
-                let ref_arg = ctx.arena.alloc(ctx.expr_ref(arg.span.with_ctxt(macsp.ctxt()), arg));
-                make_argument(ctx, placeholder_span, ref_arg, ty)
-            },
-        ));
-        let args = ctx.arena.alloc(ctx.expr(macsp, hir::ExprKind::Array(args)));
-        let args_ident = Ident::new(sym::args, macsp);
-        let (args_pat, args_hir_id) = ctx.pat_ident(macsp, args_ident);
-        let let_statement = ctx.stmt_super_let_pat(macsp, args_pat, Some(args));
-        (vec![let_statement], ctx.arena.alloc(ctx.expr_ident_mut(macsp, args_ident, args_hir_id)))
     } else {
         // Generate:
         //     super let args = (&arg0, &arg1, &…);
diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs
index 9ab5b0b3547..608ccfefeb6 100644
--- a/compiler/rustc_ast_passes/src/feature_gate.rs
+++ b/compiler/rustc_ast_passes/src/feature_gate.rs
@@ -183,7 +183,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                 gate_doc!(
                     "experimental" {
                         cfg => doc_cfg
-                        cfg_hide => doc_cfg_hide
+                        auto_cfg => doc_cfg
                         masked => doc_masked
                         notable_trait => doc_notable_trait
                     }
diff --git a/compiler/rustc_attr_parsing/messages.ftl b/compiler/rustc_attr_parsing/messages.ftl
index 81ec17077c1..6c5346e8355 100644
--- a/compiler/rustc_attr_parsing/messages.ftl
+++ b/compiler/rustc_attr_parsing/messages.ftl
@@ -8,7 +8,15 @@ attr_parsing_deprecated_item_suggestion =
 
 attr_parsing_empty_attribute =
     unused attribute
-    .suggestion = remove this attribute
+    .suggestion = {$valid_without_list ->
+        [true] remove these parentheses
+        *[other] remove this attribute
+    }
+    .note = {$valid_without_list ->
+        [true] using `{$attr_path}` with an empty list is equivalent to not using a list at all
+        *[other] using `{$attr_path}` with an empty list has no effect
+    }
+
 
 attr_parsing_invalid_target = `#[{$name}]` attribute cannot be used on {$target}
     .help = `#[{$name}]` can {$only}be applied to {$applied}
diff --git a/compiler/rustc_attr_parsing/src/attributes/debugger.rs b/compiler/rustc_attr_parsing/src/attributes/debugger.rs
new file mode 100644
index 00000000000..56ff10be426
--- /dev/null
+++ b/compiler/rustc_attr_parsing/src/attributes/debugger.rs
@@ -0,0 +1,60 @@
+use rustc_hir::attrs::{DebugVisualizer, DebuggerVisualizerType};
+
+use super::prelude::*;
+
+pub(crate) struct DebuggerViualizerParser;
+
+impl<S: Stage> CombineAttributeParser<S> for DebuggerViualizerParser {
+    const PATH: &[Symbol] = &[sym::debugger_visualizer];
+    const ALLOWED_TARGETS: AllowedTargets =
+        AllowedTargets::AllowList(&[Allow(Target::Mod), Allow(Target::Crate)]);
+    const TEMPLATE: AttributeTemplate = template!(
+        List: &[r#"natvis_file = "...", gdb_script_file = "...""#],
+        "https://doc.rust-lang.org/reference/attributes/debugger.html#the-debugger_visualizer-attribute"
+    );
+
+    type Item = DebugVisualizer;
+    const CONVERT: ConvertFn<Self::Item> = |v, _| AttributeKind::DebuggerVisualizer(v);
+
+    fn extend<'c>(
+        cx: &'c mut AcceptContext<'_, '_, S>,
+        args: &'c ArgParser<'_>,
+    ) -> impl IntoIterator<Item = Self::Item> + 'c {
+        let Some(l) = args.list() else {
+            cx.expected_list(args.span().unwrap_or(cx.attr_span));
+            return None;
+        };
+        let Some(single) = l.single() else {
+            cx.expected_single_argument(l.span);
+            return None;
+        };
+        let Some(mi) = single.meta_item() else {
+            cx.expected_name_value(single.span(), None);
+            return None;
+        };
+        let path = mi.path().word_sym();
+        let visualizer_type = match path {
+            Some(sym::natvis_file) => DebuggerVisualizerType::Natvis,
+            Some(sym::gdb_script_file) => DebuggerVisualizerType::GdbPrettyPrinter,
+            _ => {
+                cx.expected_specific_argument(
+                    mi.path().span(),
+                    &[sym::natvis_file, sym::gdb_script_file],
+                );
+                return None;
+            }
+        };
+
+        let Some(path) = mi.args().name_value() else {
+            cx.expected_name_value(single.span(), path);
+            return None;
+        };
+
+        let Some(path) = path.value_as_str() else {
+            cx.expected_string_literal(path.value_span, Some(path.value_as_lit()));
+            return None;
+        };
+
+        Some(DebugVisualizer { span: mi.span(), visualizer_type, path })
+    }
+}
diff --git a/compiler/rustc_attr_parsing/src/attributes/mod.rs b/compiler/rustc_attr_parsing/src/attributes/mod.rs
index 4ed13d239b9..8dbf4c0ef32 100644
--- a/compiler/rustc_attr_parsing/src/attributes/mod.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/mod.rs
@@ -36,6 +36,7 @@ pub(crate) mod cfg_old;
 pub(crate) mod codegen_attrs;
 pub(crate) mod confusables;
 pub(crate) mod crate_level;
+pub(crate) mod debugger;
 pub(crate) mod deprecation;
 pub(crate) mod dummy;
 pub(crate) mod inline;
diff --git a/compiler/rustc_attr_parsing/src/context.rs b/compiler/rustc_attr_parsing/src/context.rs
index de1ab5e9578..e8bb4caa416 100644
--- a/compiler/rustc_attr_parsing/src/context.rs
+++ b/compiler/rustc_attr_parsing/src/context.rs
@@ -28,6 +28,7 @@ use crate::attributes::crate_level::{
     CrateNameParser, MoveSizeLimitParser, NoCoreParser, NoStdParser, PatternComplexityLimitParser,
     RecursionLimitParser, RustcCoherenceIsCoreParser, TypeLengthLimitParser,
 };
+use crate::attributes::debugger::DebuggerViualizerParser;
 use crate::attributes::deprecation::DeprecationParser;
 use crate::attributes::dummy::DummyParser;
 use crate::attributes::inline::{InlineParser, RustcForceInlineParser};
@@ -163,6 +164,7 @@ attribute_parsers!(
         // tidy-alphabetical-start
         Combine<AllowConstFnUnstableParser>,
         Combine<AllowInternalUnstableParser>,
+        Combine<DebuggerViualizerParser>,
         Combine<ForceTargetFeatureParser>,
         Combine<LinkParser>,
         Combine<ReprParser>,
@@ -595,7 +597,12 @@ impl<'f, 'sess: 'f, S: Stage> AcceptContext<'f, 'sess, S> {
     }
 
     pub(crate) fn warn_empty_attribute(&mut self, span: Span) {
-        self.emit_lint(AttributeLintKind::EmptyAttribute { first_span: span }, span);
+        let attr_path = self.attr_path.clone();
+        let valid_without_list = self.template.word;
+        self.emit_lint(
+            AttributeLintKind::EmptyAttribute { first_span: span, attr_path, valid_without_list },
+            span,
+        );
     }
 }
 
diff --git a/compiler/rustc_attr_parsing/src/lints.rs b/compiler/rustc_attr_parsing/src/lints.rs
index ab8ba0daf1f..3a2a3704669 100644
--- a/compiler/rustc_attr_parsing/src/lints.rs
+++ b/compiler/rustc_attr_parsing/src/lints.rs
@@ -43,12 +43,18 @@ pub fn emit_attribute_lint<L: LintEmitter>(lint: &AttributeLint<L::Id>, lint_emi
                     ),
                 },
             ),
-        AttributeLintKind::EmptyAttribute { first_span } => lint_emitter.emit_node_span_lint(
-            rustc_session::lint::builtin::UNUSED_ATTRIBUTES,
-            *id,
-            *first_span,
-            session_diagnostics::EmptyAttributeList { attr_span: *first_span },
-        ),
+        AttributeLintKind::EmptyAttribute { first_span, attr_path, valid_without_list } => {
+            lint_emitter.emit_node_span_lint(
+                rustc_session::lint::builtin::UNUSED_ATTRIBUTES,
+                *id,
+                *first_span,
+                session_diagnostics::EmptyAttributeList {
+                    attr_span: *first_span,
+                    attr_path: attr_path.clone(),
+                    valid_without_list: *valid_without_list,
+                },
+            )
+        }
         AttributeLintKind::InvalidTarget { name, target, applied, only } => lint_emitter
             .emit_node_span_lint(
                 // This check is here because `deprecated` had its own lint group and removing this would be a breaking change
diff --git a/compiler/rustc_attr_parsing/src/parser.rs b/compiler/rustc_attr_parsing/src/parser.rs
index 4f903594225..3f4f5679015 100644
--- a/compiler/rustc_attr_parsing/src/parser.rs
+++ b/compiler/rustc_attr_parsing/src/parser.rs
@@ -49,7 +49,7 @@ impl<'a> PathParser<'a> {
     }
 
     pub fn segments_is(&self, segments: &[Symbol]) -> bool {
-        self.len() == segments.len() && self.segments().zip(segments).all(|(a, b)| a.name == *b)
+        self.segments().map(|segment| &segment.name).eq(segments)
     }
 
     pub fn word(&self) -> Option<Ident> {
diff --git a/compiler/rustc_attr_parsing/src/session_diagnostics.rs b/compiler/rustc_attr_parsing/src/session_diagnostics.rs
index 2c2b14c8a68..1194ac5872c 100644
--- a/compiler/rustc_attr_parsing/src/session_diagnostics.rs
+++ b/compiler/rustc_attr_parsing/src/session_diagnostics.rs
@@ -503,9 +503,12 @@ pub(crate) struct EmptyConfusables {
 
 #[derive(LintDiagnostic)]
 #[diag(attr_parsing_empty_attribute)]
+#[note]
 pub(crate) struct EmptyAttributeList {
     #[suggestion(code = "", applicability = "machine-applicable")]
     pub attr_span: Span,
+    pub attr_path: AttrPath,
+    pub valid_without_list: bool,
 }
 
 #[derive(LintDiagnostic)]
diff --git a/compiler/rustc_borrowck/src/borrowck_errors.rs b/compiler/rustc_borrowck/src/borrowck_errors.rs
index c9be5575da5..7c9011505d6 100644
--- a/compiler/rustc_borrowck/src/borrowck_errors.rs
+++ b/compiler/rustc_borrowck/src/borrowck_errors.rs
@@ -426,7 +426,7 @@ impl<'infcx, 'tcx> crate::MirBorrowckCtxt<'_, 'infcx, 'tcx> {
     }
 
     pub(crate) fn path_does_not_live_long_enough(&self, span: Span, path: &str) -> Diag<'infcx> {
-        struct_span_code_err!(self.dcx(), span, E0597, "{} does not live long enough", path,)
+        struct_span_code_err!(self.dcx(), span, E0597, "{} does not live long enough", path)
     }
 
     pub(crate) fn cannot_return_reference_to_local(
@@ -480,7 +480,7 @@ impl<'infcx, 'tcx> crate::MirBorrowckCtxt<'_, 'infcx, 'tcx> {
     }
 
     pub(crate) fn temporary_value_borrowed_for_too_long(&self, span: Span) -> Diag<'infcx> {
-        struct_span_code_err!(self.dcx(), span, E0716, "temporary value dropped while borrowed",)
+        struct_span_code_err!(self.dcx(), span, E0716, "temporary value dropped while borrowed")
     }
 }
 
diff --git a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
index a5b16b50838..fa1be4cec1e 100644
--- a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
@@ -2992,6 +2992,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
         self.buffer_error(err);
     }
 
+    #[tracing::instrument(level = "debug", skip(self, explanation))]
     fn report_local_value_does_not_live_long_enough(
         &self,
         location: Location,
@@ -3001,13 +3002,6 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
         borrow_spans: UseSpans<'tcx>,
         explanation: BorrowExplanation<'tcx>,
     ) -> Diag<'infcx> {
-        debug!(
-            "report_local_value_does_not_live_long_enough(\
-             {:?}, {:?}, {:?}, {:?}, {:?}\
-             )",
-            location, name, borrow, drop_span, borrow_spans
-        );
-
         let borrow_span = borrow_spans.var_or_use_path_span();
         if let BorrowExplanation::MustBeValidFor {
             category,
diff --git a/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs b/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
index 7ca07bb9b43..638d89f5bcb 100644
--- a/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
@@ -416,6 +416,26 @@ impl<'tcx> BorrowExplanation<'tcx> {
                 {
                     self.add_object_lifetime_default_note(tcx, err, unsize_ty);
                 }
+
+                let mut preds = path
+                    .iter()
+                    .filter_map(|constraint| match constraint.category {
+                        ConstraintCategory::Predicate(pred) if !pred.is_dummy() => Some(pred),
+                        _ => None,
+                    })
+                    .collect::<Vec<Span>>();
+                preds.sort();
+                preds.dedup();
+                if !preds.is_empty() {
+                    let s = if preds.len() == 1 { "" } else { "s" };
+                    err.span_note(
+                        preds,
+                        format!(
+                            "requirement{s} that the value outlives `{region_name}` introduced here"
+                        ),
+                    );
+                }
+
                 self.add_lifetime_bound_suggestion_to_diagnostic(err, &category, span, region_name);
             }
             _ => {}
diff --git a/compiler/rustc_borrowck/src/lib.rs b/compiler/rustc_borrowck/src/lib.rs
index cc27b9e5dde..865cfd7d2e2 100644
--- a/compiler/rustc_borrowck/src/lib.rs
+++ b/compiler/rustc_borrowck/src/lib.rs
@@ -119,7 +119,7 @@ pub fn provide(providers: &mut Providers) {
 fn mir_borrowck(
     tcx: TyCtxt<'_>,
     def: LocalDefId,
-) -> Result<&ConcreteOpaqueTypes<'_>, ErrorGuaranteed> {
+) -> Result<&DefinitionSiteHiddenTypes<'_>, ErrorGuaranteed> {
     assert!(!tcx.is_typeck_child(def.to_def_id()));
     let (input_body, _) = tcx.mir_promoted(def);
     debug!("run query mir_borrowck: {}", tcx.def_path_str(def));
@@ -130,7 +130,7 @@ fn mir_borrowck(
         Err(guar)
     } else if input_body.should_skip() {
         debug!("Skipping borrowck because of injected body");
-        let opaque_types = ConcreteOpaqueTypes(Default::default());
+        let opaque_types = DefinitionSiteHiddenTypes(Default::default());
         Ok(tcx.arena.alloc(opaque_types))
     } else {
         let mut root_cx = BorrowCheckRootCtxt::new(tcx, def, None);
diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs
index 0910e8ef4b3..e98c60e6338 100644
--- a/compiler/rustc_borrowck/src/region_infer/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/mod.rs
@@ -1382,10 +1382,10 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     }
 
     /// The constraints we get from equating the hidden type of each use of an opaque
-    /// with its final concrete type may end up getting preferred over other, potentially
+    /// with its final hidden type may end up getting preferred over other, potentially
     /// longer constraint paths.
     ///
-    /// Given that we compute the final concrete type by relying on this existing constraint
+    /// Given that we compute the final hidden type by relying on this existing constraint
     /// path, this can easily end up hiding the actual reason for why we require these regions
     /// to be equal.
     ///
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 0af636aa734..8d89f3e0d87 100644
--- a/compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs
@@ -8,7 +8,7 @@ use rustc_infer::infer::outlives::env::RegionBoundPairs;
 use rustc_infer::infer::{InferCtxt, NllRegionVariableOrigin, OpaqueTypeStorageEntries};
 use rustc_infer::traits::ObligationCause;
 use rustc_macros::extension;
-use rustc_middle::mir::{Body, ConcreteOpaqueTypes, ConstraintCategory};
+use rustc_middle::mir::{Body, ConstraintCategory, DefinitionSiteHiddenTypes};
 use rustc_middle::ty::{
     self, DefiningScopeKind, EarlyBinder, FallibleTypeFolder, GenericArg, GenericArgsRef,
     OpaqueHiddenType, OpaqueTypeKey, Region, RegionVid, Ty, TyCtxt, TypeFoldable,
@@ -129,9 +129,9 @@ fn nll_var_to_universal_region<'tcx>(
 /// Collect all defining uses of opaque types inside of this typeck root. This
 /// expects the hidden type to be mapped to the definition parameters of the opaque
 /// and errors if we end up with distinct hidden types.
-fn add_concrete_opaque_type<'tcx>(
+fn add_hidden_type<'tcx>(
     tcx: TyCtxt<'tcx>,
-    concrete_opaque_types: &mut ConcreteOpaqueTypes<'tcx>,
+    hidden_types: &mut DefinitionSiteHiddenTypes<'tcx>,
     def_id: LocalDefId,
     hidden_ty: OpaqueHiddenType<'tcx>,
 ) {
@@ -139,7 +139,7 @@ fn add_concrete_opaque_type<'tcx>(
     // back to the opaque type definition. E.g. we may have `OpaqueType<X, Y>` mapped to
     // `(X, Y)` and `OpaqueType<Y, X>` mapped to `(Y, X)`, and those are the same, but we
     // only know that once we convert the generic parameters to those of the opaque type.
-    if let Some(prev) = concrete_opaque_types.0.get_mut(&def_id) {
+    if let Some(prev) = hidden_types.0.get_mut(&def_id) {
         if prev.ty != hidden_ty.ty {
             let guar = hidden_ty.ty.error_reported().err().unwrap_or_else(|| {
                 let (Ok(e) | Err(e)) = prev.build_mismatch_error(&hidden_ty, tcx).map(|d| d.emit());
@@ -151,15 +151,15 @@ fn add_concrete_opaque_type<'tcx>(
         // FIXME(oli-obk): collect multiple spans for better diagnostics down the road.
         prev.span = prev.span.substitute_dummy(hidden_ty.span);
     } else {
-        concrete_opaque_types.0.insert(def_id, hidden_ty);
+        hidden_types.0.insert(def_id, hidden_ty);
     }
 }
 
-fn get_concrete_opaque_type<'tcx>(
-    concrete_opaque_types: &ConcreteOpaqueTypes<'tcx>,
+fn get_hidden_type<'tcx>(
+    hidden_types: &DefinitionSiteHiddenTypes<'tcx>,
     def_id: LocalDefId,
 ) -> Option<EarlyBinder<'tcx, OpaqueHiddenType<'tcx>>> {
-    concrete_opaque_types.0.get(&def_id).map(|ty| EarlyBinder::bind(*ty))
+    hidden_types.0.get(&def_id).map(|ty| EarlyBinder::bind(*ty))
 }
 
 #[derive(Debug)]
@@ -173,22 +173,22 @@ struct DefiningUse<'tcx> {
 }
 
 /// This computes the actual hidden types of the opaque types and maps them to their
-/// definition sites. Outside of registering the computed concrete types this function
+/// definition sites. Outside of registering the computed hidden types this function
 /// does not mutate the current borrowck state.
 ///
 /// While it may fail to infer the hidden type and return errors, we always apply
-/// the computed concrete hidden type to all opaque type uses to check whether they
+/// the computed hidden type to all opaque type uses to check whether they
 /// are correct. This is necessary to support non-defining uses of opaques in their
 /// defining scope.
 ///
 /// It also means that this whole function is not really soundness critical as we
 /// recheck all uses of the opaques regardless.
-pub(crate) fn compute_concrete_opaque_types<'tcx>(
+pub(crate) fn compute_definition_site_hidden_types<'tcx>(
     infcx: &BorrowckInferCtxt<'tcx>,
     universal_region_relations: &Frozen<UniversalRegionRelations<'tcx>>,
     constraints: &MirTypeckRegionConstraints<'tcx>,
     location_map: Rc<DenseLocationMap>,
-    concrete_opaque_types: &mut ConcreteOpaqueTypes<'tcx>,
+    hidden_types: &mut DefinitionSiteHiddenTypes<'tcx>,
     opaque_types: &[(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>)],
 ) -> Vec<DeferredOpaqueTypeError<'tcx>> {
     let mut errors = Vec::new();
@@ -201,8 +201,7 @@ pub(crate) fn compute_concrete_opaque_types<'tcx>(
     // We start by checking each use of an opaque type during type check and
     // check whether the generic arguments of the opaque type are fully
     // universal, if so, it's a defining use.
-    let defining_uses =
-        collect_defining_uses(&mut rcx, concrete_opaque_types, opaque_types, &mut errors);
+    let defining_uses = collect_defining_uses(&mut rcx, hidden_types, opaque_types, &mut errors);
 
     // We now compute and apply member constraints for all regions in the hidden
     // types of each defining use. This mutates the region values of the `rcx` which
@@ -210,11 +209,11 @@ pub(crate) fn compute_concrete_opaque_types<'tcx>(
     apply_member_constraints(&mut rcx, &defining_uses);
 
     // After applying member constraints, we now check whether all member regions ended
-    // up equal to one of their choice regions and compute the actual concrete type of
+    // up equal to one of their choice regions and compute the actual hidden type of
     // the opaque type definition. This is stored in the `root_cx`.
-    compute_concrete_types_from_defining_uses(
+    compute_definition_site_hidden_types_from_defining_uses(
         &rcx,
-        concrete_opaque_types,
+        hidden_types,
         &defining_uses,
         &mut errors,
     );
@@ -224,7 +223,7 @@ pub(crate) fn compute_concrete_opaque_types<'tcx>(
 #[instrument(level = "debug", skip_all, ret)]
 fn collect_defining_uses<'tcx>(
     rcx: &mut RegionCtxt<'_, 'tcx>,
-    concrete_opaque_types: &mut ConcreteOpaqueTypes<'tcx>,
+    hidden_types: &mut DefinitionSiteHiddenTypes<'tcx>,
     opaque_types: &[(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>)],
     errors: &mut Vec<DeferredOpaqueTypeError<'tcx>>,
 ) -> Vec<DefiningUse<'tcx>> {
@@ -244,9 +243,9 @@ fn collect_defining_uses<'tcx>(
             // with `TypingMode::Borrowck`.
             if infcx.tcx.use_typing_mode_borrowck() {
                 match err {
-                    NonDefiningUseReason::Tainted(guar) => add_concrete_opaque_type(
+                    NonDefiningUseReason::Tainted(guar) => add_hidden_type(
                         infcx.tcx,
-                        concrete_opaque_types,
+                        hidden_types,
                         opaque_type_key.def_id,
                         OpaqueHiddenType::new_error(infcx.tcx, guar),
                     ),
@@ -277,9 +276,9 @@ fn collect_defining_uses<'tcx>(
     defining_uses
 }
 
-fn compute_concrete_types_from_defining_uses<'tcx>(
+fn compute_definition_site_hidden_types_from_defining_uses<'tcx>(
     rcx: &RegionCtxt<'_, 'tcx>,
-    concrete_opaque_types: &mut ConcreteOpaqueTypes<'tcx>,
+    hidden_types: &mut DefinitionSiteHiddenTypes<'tcx>,
     defining_uses: &[DefiningUse<'tcx>],
     errors: &mut Vec<DeferredOpaqueTypeError<'tcx>>,
 ) {
@@ -358,9 +357,9 @@ fn compute_concrete_types_from_defining_uses<'tcx>(
                 },
             ));
         }
-        add_concrete_opaque_type(
+        add_hidden_type(
             tcx,
-            concrete_opaque_types,
+            hidden_types,
             opaque_type_key.def_id,
             OpaqueHiddenType { span: hidden_type.span, ty },
         );
@@ -489,20 +488,20 @@ impl<'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for ToArgRegionsFolder<'_, 'tcx> {
 ///
 /// It does this by equating the hidden type of each use with the instantiated final
 /// hidden type of the opaque.
-pub(crate) fn apply_computed_concrete_opaque_types<'tcx>(
+pub(crate) fn apply_definition_site_hidden_types<'tcx>(
     infcx: &BorrowckInferCtxt<'tcx>,
     body: &Body<'tcx>,
     universal_regions: &UniversalRegions<'tcx>,
     region_bound_pairs: &RegionBoundPairs<'tcx>,
     known_type_outlives_obligations: &[ty::PolyTypeOutlivesPredicate<'tcx>],
     constraints: &mut MirTypeckRegionConstraints<'tcx>,
-    concrete_opaque_types: &mut ConcreteOpaqueTypes<'tcx>,
+    hidden_types: &mut DefinitionSiteHiddenTypes<'tcx>,
     opaque_types: &[(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>)],
 ) -> Vec<DeferredOpaqueTypeError<'tcx>> {
     let tcx = infcx.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 {
+        let Some(expected) = get_hidden_type(hidden_types, key.def_id) else {
             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()
@@ -521,12 +520,7 @@ pub(crate) fn apply_computed_concrete_opaque_types<'tcx>(
                 hidden_type.span,
                 "non-defining use in the defining scope with no defining uses",
             );
-            add_concrete_opaque_type(
-                tcx,
-                concrete_opaque_types,
-                key.def_id,
-                OpaqueHiddenType::new_error(tcx, guar),
-            );
+            add_hidden_type(tcx, hidden_types, key.def_id, OpaqueHiddenType::new_error(tcx, guar));
             continue;
         };
 
@@ -566,18 +560,13 @@ pub(crate) fn apply_computed_concrete_opaque_types<'tcx>(
                 "equating opaque types",
             ),
         ) {
-            add_concrete_opaque_type(
-                tcx,
-                concrete_opaque_types,
-                key.def_id,
-                OpaqueHiddenType::new_error(tcx, guar),
-            );
+            add_hidden_type(tcx, hidden_types, key.def_id, OpaqueHiddenType::new_error(tcx, guar));
         }
     }
     errors
 }
 
-/// In theory `apply_concrete_opaque_types` could introduce new uses of opaque types.
+/// In theory `apply_definition_site_hidden_types` could introduce new uses of opaque types.
 /// We do not check these new uses so this could be unsound.
 ///
 /// We detect any new uses and simply delay a bug if they occur. If this results in
@@ -682,13 +671,6 @@ impl<'tcx> InferCtxt<'tcx> {
     ///
     /// (*) C1 and C2 were introduced in the comments on
     /// `register_member_constraints`. Read that comment for more context.
-    ///
-    /// # Parameters
-    ///
-    /// - `def_id`, the `impl Trait` type
-    /// - `args`, the args used to instantiate this opaque type
-    /// - `instantiated_ty`, the inferred type C1 -- fully resolved, lifted version of
-    ///   `opaque_defn.concrete_ty`
     #[instrument(level = "debug", skip(self))]
     fn infer_opaque_definition_from_instantiation(
         &self,
diff --git a/compiler/rustc_borrowck/src/root_cx.rs b/compiler/rustc_borrowck/src/root_cx.rs
index cd4e9683f2d..21c11e12873 100644
--- a/compiler/rustc_borrowck/src/root_cx.rs
+++ b/compiler/rustc_borrowck/src/root_cx.rs
@@ -12,12 +12,12 @@ use smallvec::SmallVec;
 use crate::consumers::BorrowckConsumer;
 use crate::nll::compute_closure_requirements_modulo_opaques;
 use crate::region_infer::opaque_types::{
-    apply_computed_concrete_opaque_types, clone_and_resolve_opaque_types,
-    compute_concrete_opaque_types, detect_opaque_types_added_while_handling_opaque_types,
+    apply_definition_site_hidden_types, clone_and_resolve_opaque_types,
+    compute_definition_site_hidden_types, detect_opaque_types_added_while_handling_opaque_types,
 };
 use crate::type_check::{Locations, constraint_conversion};
 use crate::{
-    ClosureRegionRequirements, CollectRegionConstraintsResult, ConcreteOpaqueTypes,
+    ClosureRegionRequirements, CollectRegionConstraintsResult, DefinitionSiteHiddenTypes,
     PropagatedBorrowCheckResults, borrowck_check_region_constraints,
     borrowck_collect_region_constraints,
 };
@@ -27,7 +27,7 @@ use crate::{
 pub(super) struct BorrowCheckRootCtxt<'tcx> {
     pub tcx: TyCtxt<'tcx>,
     root_def_id: LocalDefId,
-    concrete_opaque_types: ConcreteOpaqueTypes<'tcx>,
+    hidden_types: DefinitionSiteHiddenTypes<'tcx>,
     /// The region constraints computed by [borrowck_collect_region_constraints]. This uses
     /// an [FxIndexMap] to guarantee that iterating over it visits nested bodies before
     /// their parents.
@@ -49,7 +49,7 @@ impl<'tcx> BorrowCheckRootCtxt<'tcx> {
         BorrowCheckRootCtxt {
             tcx,
             root_def_id,
-            concrete_opaque_types: Default::default(),
+            hidden_types: Default::default(),
             collect_region_constraints_results: Default::default(),
             propagated_borrowck_results: Default::default(),
             tainted_by_errors: None,
@@ -72,11 +72,11 @@ impl<'tcx> BorrowCheckRootCtxt<'tcx> {
         &self.propagated_borrowck_results[&nested_body_def_id].used_mut_upvars
     }
 
-    pub(super) fn finalize(self) -> Result<&'tcx ConcreteOpaqueTypes<'tcx>, ErrorGuaranteed> {
+    pub(super) fn finalize(self) -> Result<&'tcx DefinitionSiteHiddenTypes<'tcx>, ErrorGuaranteed> {
         if let Some(guar) = self.tainted_by_errors {
             Err(guar)
         } else {
-            Ok(self.tcx.arena.alloc(self.concrete_opaque_types))
+            Ok(self.tcx.arena.alloc(self.hidden_types))
         }
     }
 
@@ -88,12 +88,12 @@ impl<'tcx> BorrowCheckRootCtxt<'tcx> {
                 &input.universal_region_relations,
                 &mut input.constraints,
             );
-            input.deferred_opaque_type_errors = compute_concrete_opaque_types(
+            input.deferred_opaque_type_errors = compute_definition_site_hidden_types(
                 &input.infcx,
                 &input.universal_region_relations,
                 &input.constraints,
                 Rc::clone(&input.location_map),
-                &mut self.concrete_opaque_types,
+                &mut self.hidden_types,
                 &opaque_types,
             );
             per_body_info.push((num_entries, opaque_types));
@@ -103,14 +103,14 @@ impl<'tcx> BorrowCheckRootCtxt<'tcx> {
             self.collect_region_constraints_results.values_mut().zip(per_body_info)
         {
             if input.deferred_opaque_type_errors.is_empty() {
-                input.deferred_opaque_type_errors = apply_computed_concrete_opaque_types(
+                input.deferred_opaque_type_errors = apply_definition_site_hidden_types(
                     &input.infcx,
                     &input.body_owned,
                     &input.universal_region_relations.universal_regions,
                     &input.region_bound_pairs,
                     &input.known_type_outlives_obligations,
                     &mut input.constraints,
-                    &mut self.concrete_opaque_types,
+                    &mut self.hidden_types,
                     &opaque_types,
                 );
             }
diff --git a/compiler/rustc_builtin_macros/src/autodiff.rs b/compiler/rustc_builtin_macros/src/autodiff.rs
index f4a923797e2..ddc59bfe141 100644
--- a/compiler/rustc_builtin_macros/src/autodiff.rs
+++ b/compiler/rustc_builtin_macros/src/autodiff.rs
@@ -377,8 +377,7 @@ mod llvm_enzyme {
                 (ast::AttrKind::Normal(a), ast::AttrKind::Normal(b)) => {
                     let a = &a.item.path;
                     let b = &b.item.path;
-                    a.segments.len() == b.segments.len()
-                        && a.segments.iter().zip(b.segments.iter()).all(|(a, b)| a.ident == b.ident)
+                    a.segments.iter().eq_by(&b.segments, |a, b| a.ident == b.ident)
                 }
                 _ => false,
             }
diff --git a/compiler/rustc_builtin_macros/src/deriving/coerce_pointee.rs b/compiler/rustc_builtin_macros/src/deriving/coerce_pointee.rs
index 75db5d77783..5b378de8bbd 100644
--- a/compiler/rustc_builtin_macros/src/deriving/coerce_pointee.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/coerce_pointee.rs
@@ -356,21 +356,14 @@ fn contains_maybe_sized_bound(bounds: &[GenericBound]) -> bool {
     bounds.iter().any(is_maybe_sized_bound)
 }
 
-fn path_segment_is_exact_match(path_segments: &[ast::PathSegment], syms: &[Symbol]) -> bool {
-    path_segments.iter().zip(syms).all(|(segment, &symbol)| segment.ident.name == symbol)
-}
-
 fn is_sized_marker(path: &ast::Path) -> bool {
     const CORE_UNSIZE: [Symbol; 3] = [sym::core, sym::marker, sym::Sized];
     const STD_UNSIZE: [Symbol; 3] = [sym::std, sym::marker, sym::Sized];
-    if path.segments.len() == 4 && path.is_global() {
-        path_segment_is_exact_match(&path.segments[1..], &CORE_UNSIZE)
-            || path_segment_is_exact_match(&path.segments[1..], &STD_UNSIZE)
-    } else if path.segments.len() == 3 {
-        path_segment_is_exact_match(&path.segments, &CORE_UNSIZE)
-            || path_segment_is_exact_match(&path.segments, &STD_UNSIZE)
+    let segments = || path.segments.iter().map(|segment| segment.ident.name);
+    if path.is_global() {
+        segments().skip(1).eq(CORE_UNSIZE) || segments().skip(1).eq(STD_UNSIZE)
     } else {
-        *path == sym::Sized
+        segments().eq(CORE_UNSIZE) || segments().eq(STD_UNSIZE) || *path == sym::Sized
     }
 }
 
diff --git a/compiler/rustc_builtin_macros/src/format.rs b/compiler/rustc_builtin_macros/src/format.rs
index d70888205a5..bffc0407e81 100644
--- a/compiler/rustc_builtin_macros/src/format.rs
+++ b/compiler/rustc_builtin_macros/src/format.rs
@@ -768,7 +768,7 @@ fn report_missing_placeholders(
 
     if !found_foreign && invalid_refs.is_empty() {
         // Show example if user didn't use any format specifiers
-        let show_example = used.iter().all(|used| !used);
+        let show_example = !used.contains(&true);
 
         if !show_example {
             if unused.len() > 1 {
diff --git a/compiler/rustc_builtin_macros/src/lib.rs b/compiler/rustc_builtin_macros/src/lib.rs
index 4541e2cd3b4..57cf62ea612 100644
--- a/compiler/rustc_builtin_macros/src/lib.rs
+++ b/compiler/rustc_builtin_macros/src/lib.rs
@@ -11,6 +11,7 @@
 #![feature(box_patterns)]
 #![feature(decl_macro)]
 #![feature(if_let_guard)]
+#![feature(iter_order_by)]
 #![feature(proc_macro_internals)]
 #![feature(proc_macro_quote)]
 #![feature(rustdoc_internals)]
diff --git a/compiler/rustc_codegen_cranelift/src/abi/comments.rs b/compiler/rustc_codegen_cranelift/src/abi/comments.rs
index c74efeb59f3..d1b2b9a502a 100644
--- a/compiler/rustc_codegen_cranelift/src/abi/comments.rs
+++ b/compiler/rustc_codegen_cranelift/src/abi/comments.rs
@@ -89,7 +89,7 @@ pub(super) fn add_local_place_comments<'tcx>(
         format!("{:?}", local),
         format!("{:?}", ty),
         size.bytes(),
-        align.abi.bytes(),
+        align.bytes(),
         if extra.is_empty() { "" } else { "                " },
         extra,
     ));
diff --git a/compiler/rustc_codegen_cranelift/src/abi/pass_mode.rs b/compiler/rustc_codegen_cranelift/src/abi/pass_mode.rs
index 2031842062d..7a909a740b0 100644
--- a/compiler/rustc_codegen_cranelift/src/abi/pass_mode.rs
+++ b/compiler/rustc_codegen_cranelift/src/abi/pass_mode.rs
@@ -233,7 +233,7 @@ pub(super) fn from_casted_value<'tcx>(
         // It may also be smaller for example when the type is a wrapper around an integer with a
         // larger alignment than the integer.
         std::cmp::max(abi_param_size, layout_size),
-        u32::try_from(layout.align.abi.bytes()).unwrap(),
+        u32::try_from(layout.align.bytes()).unwrap(),
     );
     let mut block_params_iter = block_params.iter().copied();
     for (offset, _) in abi_params {
diff --git a/compiler/rustc_codegen_cranelift/src/base.rs b/compiler/rustc_codegen_cranelift/src/base.rs
index a2f844642f8..ebf2ccf74de 100644
--- a/compiler/rustc_codegen_cranelift/src/base.rs
+++ b/compiler/rustc_codegen_cranelift/src/base.rs
@@ -846,7 +846,7 @@ fn codegen_stmt<'tcx>(fx: &mut FunctionCx<'_, '_, 'tcx>, cur_block: Block, stmt:
                     let layout = fx.layout_of(fx.monomorphize(ty));
                     let val = match null_op {
                         NullOp::SizeOf => layout.size.bytes(),
-                        NullOp::AlignOf => layout.align.abi.bytes(),
+                        NullOp::AlignOf => layout.align.bytes(),
                         NullOp::OffsetOf(fields) => fx
                             .tcx
                             .offset_of_subfield(
diff --git a/compiler/rustc_codegen_cranelift/src/debuginfo/mod.rs b/compiler/rustc_codegen_cranelift/src/debuginfo/mod.rs
index 286e02b986b..4c438742f3d 100644
--- a/compiler/rustc_codegen_cranelift/src/debuginfo/mod.rs
+++ b/compiler/rustc_codegen_cranelift/src/debuginfo/mod.rs
@@ -304,7 +304,7 @@ impl DebugContext {
         entry.set(gimli::DW_AT_decl_file, AttributeValue::FileIndex(Some(file_id)));
         entry.set(gimli::DW_AT_decl_line, AttributeValue::Udata(line));
 
-        entry.set(gimli::DW_AT_alignment, AttributeValue::Udata(static_layout.align.abi.bytes()));
+        entry.set(gimli::DW_AT_alignment, AttributeValue::Udata(static_layout.align.bytes()));
 
         let mut expr = Expression::new();
         expr.op_addr(address_for_data(data_id));
diff --git a/compiler/rustc_codegen_cranelift/src/debuginfo/types.rs b/compiler/rustc_codegen_cranelift/src/debuginfo/types.rs
index 25b922c8be4..0d49f32373c 100644
--- a/compiler/rustc_codegen_cranelift/src/debuginfo/types.rs
+++ b/compiler/rustc_codegen_cranelift/src/debuginfo/types.rs
@@ -166,7 +166,7 @@ impl DebugContext {
         let tuple_entry = self.dwarf.unit.get_mut(tuple_type_id);
         tuple_entry.set(gimli::DW_AT_name, AttributeValue::StringRef(self.dwarf.strings.add(name)));
         tuple_entry.set(gimli::DW_AT_byte_size, AttributeValue::Udata(layout.size.bytes()));
-        tuple_entry.set(gimli::DW_AT_alignment, AttributeValue::Udata(layout.align.abi.bytes()));
+        tuple_entry.set(gimli::DW_AT_alignment, AttributeValue::Udata(layout.align.bytes()));
 
         for (i, (ty, dw_ty)) in components.into_iter().enumerate() {
             let member_id = self.dwarf.unit.add(tuple_type_id, gimli::DW_TAG_member);
@@ -178,9 +178,7 @@ impl DebugContext {
             member_entry.set(gimli::DW_AT_type, AttributeValue::UnitRef(dw_ty));
             member_entry.set(
                 gimli::DW_AT_alignment,
-                AttributeValue::Udata(
-                    FullyMonomorphizedLayoutCx(tcx).layout_of(ty).align.abi.bytes(),
-                ),
+                AttributeValue::Udata(FullyMonomorphizedLayoutCx(tcx).layout_of(ty).align.bytes()),
             );
             member_entry.set(
                 gimli::DW_AT_data_member_location,
diff --git a/compiler/rustc_codegen_cranelift/src/lib.rs b/compiler/rustc_codegen_cranelift/src/lib.rs
index 8e34436fb5e..5fd7c4d4f41 100644
--- a/compiler/rustc_codegen_cranelift/src/lib.rs
+++ b/compiler/rustc_codegen_cranelift/src/lib.rs
@@ -165,6 +165,10 @@ impl CodegenBackend for CraneliftCodegenBackend {
         ""
     }
 
+    fn name(&self) -> &'static str {
+        "cranelift"
+    }
+
     fn init(&self, sess: &Session) {
         use rustc_session::config::{InstrumentCoverage, Lto};
         match sess.lto() {
diff --git a/compiler/rustc_codegen_cranelift/src/unsize.rs b/compiler/rustc_codegen_cranelift/src/unsize.rs
index 643c7feb89a..d994f3e32ec 100644
--- a/compiler/rustc_codegen_cranelift/src/unsize.rs
+++ b/compiler/rustc_codegen_cranelift/src/unsize.rs
@@ -167,7 +167,7 @@ pub(crate) fn size_and_align_of<'tcx>(
     if layout.is_sized() {
         return (
             fx.bcx.ins().iconst(fx.pointer_type, layout.size.bytes() as i64),
-            fx.bcx.ins().iconst(fx.pointer_type, layout.align.abi.bytes() as i64),
+            fx.bcx.ins().iconst(fx.pointer_type, layout.align.bytes() as i64),
         );
     }
 
@@ -186,7 +186,7 @@ pub(crate) fn size_and_align_of<'tcx>(
             // times the unit size.
             (
                 fx.bcx.ins().imul_imm(info.unwrap(), unit.size.bytes() as i64),
-                fx.bcx.ins().iconst(fx.pointer_type, unit.align.abi.bytes() as i64),
+                fx.bcx.ins().iconst(fx.pointer_type, unit.align.bytes() as i64),
             )
         }
         ty::Foreign(_) => {
@@ -224,7 +224,7 @@ pub(crate) fn size_and_align_of<'tcx>(
             let unsized_offset_unadjusted = layout.fields.offset(i).bytes();
             let unsized_offset_unadjusted =
                 fx.bcx.ins().iconst(fx.pointer_type, unsized_offset_unadjusted as i64);
-            let sized_align = layout.align.abi.bytes();
+            let sized_align = layout.align.bytes();
             let sized_align = fx.bcx.ins().iconst(fx.pointer_type, sized_align as i64);
 
             // Recurse to get the size of the dynamically sized field (must be
diff --git a/compiler/rustc_codegen_cranelift/src/value_and_place.rs b/compiler/rustc_codegen_cranelift/src/value_and_place.rs
index 25bba48a9e3..db9b80c0f6a 100644
--- a/compiler/rustc_codegen_cranelift/src/value_and_place.rs
+++ b/compiler/rustc_codegen_cranelift/src/value_and_place.rs
@@ -383,7 +383,7 @@ impl<'tcx> CPlace<'tcx> {
 
         let stack_slot = fx.create_stack_slot(
             u32::try_from(layout.size.bytes()).unwrap(),
-            u32::try_from(layout.align.abi.bytes()).unwrap(),
+            u32::try_from(layout.align.bytes()).unwrap(),
         );
         CPlace { inner: CPlaceInner::Addr(stack_slot, None), layout }
     }
@@ -641,8 +641,8 @@ impl<'tcx> CPlace<'tcx> {
                         let size = dst_layout.size.bytes();
                         // `emit_small_memory_copy` uses `u8` for alignments, just use the maximum
                         // alignment that fits in a `u8` if the actual alignment is larger.
-                        let src_align = src_layout.align.abi.bytes().try_into().unwrap_or(128);
-                        let dst_align = dst_layout.align.abi.bytes().try_into().unwrap_or(128);
+                        let src_align = src_layout.align.bytes().try_into().unwrap_or(128);
+                        let dst_align = dst_layout.align.bytes().try_into().unwrap_or(128);
                         fx.bcx.emit_small_memory_copy(
                             fx.target_config,
                             to_addr,
diff --git a/compiler/rustc_codegen_gcc/src/builder.rs b/compiler/rustc_codegen_gcc/src/builder.rs
index f7a7a3f8c7e..5657620879c 100644
--- a/compiler/rustc_codegen_gcc/src/builder.rs
+++ b/compiler/rustc_codegen_gcc/src/builder.rs
@@ -1383,6 +1383,7 @@ impl<'a, 'gcc, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'gcc, 'tcx> {
         _src_align: Align,
         size: RValue<'gcc>,
         flags: MemFlags,
+        _tt: Option<rustc_ast::expand::typetree::FncTree>, // Autodiff TypeTrees are LLVM-only, ignored in GCC backend
     ) {
         assert!(!flags.contains(MemFlags::NONTEMPORAL), "non-temporal memcpy not supported");
         let size = self.intcast(size, self.type_size_t(), false);
diff --git a/compiler/rustc_codegen_gcc/src/context.rs b/compiler/rustc_codegen_gcc/src/context.rs
index 9815fb07eaa..c9ae96777de 100644
--- a/compiler/rustc_codegen_gcc/src/context.rs
+++ b/compiler/rustc_codegen_gcc/src/context.rs
@@ -147,7 +147,7 @@ impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
             let layout = tcx
                 .layout_of(ty::TypingEnv::fully_monomorphized().as_query_input(rust_type))
                 .unwrap();
-            let align = layout.align.abi.bytes();
+            let align = layout.align.bytes();
             // For types with size 1, the alignment can be 1 and only 1
             // So, we can skip the call to ``get_aligned`.
             // In the future, we can add a GCC API to query the type align,
@@ -186,9 +186,9 @@ impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
             (i128_type, u128_type)
         } else {
             /*let layout = tcx.layout_of(ParamEnv::reveal_all().and(tcx.types.i128)).unwrap();
-            let i128_align = layout.align.abi.bytes();
+            let i128_align = layout.align.bytes();
             let layout = tcx.layout_of(ParamEnv::reveal_all().and(tcx.types.u128)).unwrap();
-            let u128_align = layout.align.abi.bytes();*/
+            let u128_align = layout.align.bytes();*/
 
             // TODO(antoyo): re-enable the alignment when libgccjit fixed the issue in
             // gcc_jit_context_new_array_constructor (it should not use reinterpret_cast).
diff --git a/compiler/rustc_codegen_gcc/src/intrinsic/mod.rs b/compiler/rustc_codegen_gcc/src/intrinsic/mod.rs
index a915f5d6418..99a4f9b9f7e 100644
--- a/compiler/rustc_codegen_gcc/src/intrinsic/mod.rs
+++ b/compiler/rustc_codegen_gcc/src/intrinsic/mod.rs
@@ -770,6 +770,7 @@ impl<'gcc, 'tcx> ArgAbiExt<'gcc, 'tcx> for ArgAbi<'tcx, Ty<'tcx>> {
                     scratch_align,
                     bx.const_usize(self.layout.size.bytes()),
                     MemFlags::empty(),
+                    None,
                 );
 
                 bx.lifetime_end(scratch, scratch_size);
diff --git a/compiler/rustc_codegen_gcc/src/lib.rs b/compiler/rustc_codegen_gcc/src/lib.rs
index f76f933cad4..ec7eab8489a 100644
--- a/compiler/rustc_codegen_gcc/src/lib.rs
+++ b/compiler/rustc_codegen_gcc/src/lib.rs
@@ -184,6 +184,10 @@ impl CodegenBackend for GccCodegenBackend {
         crate::DEFAULT_LOCALE_RESOURCE
     }
 
+    fn name(&self) -> &'static str {
+        "gcc"
+    }
+
     fn init(&self, _sess: &Session) {
         #[cfg(feature = "master")]
         {
diff --git a/compiler/rustc_codegen_llvm/src/abi.rs b/compiler/rustc_codegen_llvm/src/abi.rs
index 11be7041167..1703cab942b 100644
--- a/compiler/rustc_codegen_llvm/src/abi.rs
+++ b/compiler/rustc_codegen_llvm/src/abi.rs
@@ -246,6 +246,7 @@ impl<'ll, 'tcx> ArgAbiExt<'ll, 'tcx> for ArgAbi<'tcx, Ty<'tcx>> {
                     scratch_align,
                     bx.const_usize(copy_bytes),
                     MemFlags::empty(),
+                    None,
                 );
                 bx.lifetime_end(llscratch, scratch_size);
             }
@@ -538,7 +539,13 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
 
         // If the declaration has an associated instance, compute extra attributes based on that.
         if let Some(instance) = instance {
-            llfn_attrs_from_instance(cx, llfn, instance);
+            llfn_attrs_from_instance(
+                cx,
+                cx.tcx,
+                llfn,
+                &cx.tcx.codegen_instance_attrs(instance.def),
+                Some(instance),
+            );
         }
     }
 
diff --git a/compiler/rustc_codegen_llvm/src/allocator.rs b/compiler/rustc_codegen_llvm/src/allocator.rs
index df3e49279d9..896d6755c75 100644
--- a/compiler/rustc_codegen_llvm/src/allocator.rs
+++ b/compiler/rustc_codegen_llvm/src/allocator.rs
@@ -5,15 +5,17 @@ use rustc_ast::expand::allocator::{
 };
 use rustc_codegen_ssa::traits::BaseTypeCodegenMethods as _;
 use rustc_middle::bug;
+use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
 use rustc_middle::ty::TyCtxt;
 use rustc_session::config::{DebugInfo, OomStrategy};
+use rustc_span::sym;
 use rustc_symbol_mangling::mangle_internal_symbol;
-use smallvec::SmallVec;
 
+use crate::attributes::llfn_attrs_from_instance;
 use crate::builder::SBuilder;
 use crate::declare::declare_simple_fn;
 use crate::llvm::{self, FALSE, TRUE, Type, Value};
-use crate::{SimpleCx, attributes, debuginfo, llvm_util};
+use crate::{SimpleCx, attributes, debuginfo};
 
 pub(crate) unsafe fn codegen(
     tcx: TyCtxt<'_>,
@@ -58,7 +60,26 @@ pub(crate) unsafe fn codegen(
             let from_name = mangle_internal_symbol(tcx, &global_fn_name(method.name));
             let to_name = mangle_internal_symbol(tcx, &default_fn_name(method.name));
 
-            create_wrapper_function(tcx, &cx, &from_name, Some(&to_name), &args, output, false);
+            let alloc_attr_flag = match method.name {
+                sym::alloc => CodegenFnAttrFlags::ALLOCATOR,
+                sym::dealloc => CodegenFnAttrFlags::DEALLOCATOR,
+                sym::realloc => CodegenFnAttrFlags::REALLOCATOR,
+                sym::alloc_zeroed => CodegenFnAttrFlags::ALLOCATOR_ZEROED,
+                _ => unreachable!("Unknown allocator method!"),
+            };
+
+            let mut attrs = CodegenFnAttrs::new();
+            attrs.flags |= alloc_attr_flag;
+            create_wrapper_function(
+                tcx,
+                &cx,
+                &from_name,
+                Some(&to_name),
+                &args,
+                output,
+                false,
+                &attrs,
+            );
         }
     }
 
@@ -71,6 +92,7 @@ pub(crate) unsafe fn codegen(
         &[usize, usize], // size, align
         None,
         true,
+        &CodegenFnAttrs::new(),
     );
 
     unsafe {
@@ -92,6 +114,7 @@ pub(crate) unsafe fn codegen(
             &[],
             None,
             false,
+            &CodegenFnAttrs::new(),
         );
     }
 
@@ -138,6 +161,7 @@ fn create_wrapper_function(
     args: &[&Type],
     output: Option<&Type>,
     no_return: bool,
+    attrs: &CodegenFnAttrs,
 ) {
     let ty = cx.type_func(args, output.unwrap_or_else(|| cx.type_void()));
     let llfn = declare_simple_fn(
@@ -149,18 +173,7 @@ fn create_wrapper_function(
         ty,
     );
 
-    let mut attrs = SmallVec::<[_; 2]>::new();
-
-    let target_cpu = llvm_util::target_cpu(tcx.sess);
-    let target_cpu_attr = llvm::CreateAttrStringValue(cx.llcx, "target-cpu", target_cpu);
-
-    let tune_cpu_attr = llvm_util::tune_cpu(tcx.sess)
-        .map(|tune_cpu| llvm::CreateAttrStringValue(cx.llcx, "tune-cpu", tune_cpu));
-
-    attrs.push(target_cpu_attr);
-    attrs.extend(tune_cpu_attr);
-
-    attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &attrs);
+    llfn_attrs_from_instance(cx, tcx, llfn, attrs, None);
 
     let no_return = if no_return {
         // -> ! DIFlagNoReturn
@@ -171,12 +184,6 @@ fn create_wrapper_function(
         None
     };
 
-    if tcx.sess.must_emit_unwind_tables() {
-        let uwtable =
-            attributes::uwtable_attr(cx.llcx, tcx.sess.opts.unstable_opts.use_sync_unwind);
-        attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &[uwtable]);
-    }
-
     let llbb = unsafe { llvm::LLVMAppendBasicBlockInContext(cx.llcx, llfn, c"entry".as_ptr()) };
     let mut bx = SBuilder::build(&cx, llbb);
 
diff --git a/compiler/rustc_codegen_llvm/src/attributes.rs b/compiler/rustc_codegen_llvm/src/attributes.rs
index dcf6b945497..8070ea0b3e9 100644
--- a/compiler/rustc_codegen_llvm/src/attributes.rs
+++ b/compiler/rustc_codegen_llvm/src/attributes.rs
@@ -1,20 +1,21 @@
 //! Set and unset common attributes on LLVM values.
-use rustc_codegen_ssa::traits::*;
 use rustc_hir::attrs::{InlineAttr, InstructionSetAttr, OptimizeAttr};
 use rustc_hir::def_id::DefId;
-use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, PatchableFunctionEntry};
+use rustc_middle::middle::codegen_fn_attrs::{
+    CodegenFnAttrFlags, CodegenFnAttrs, PatchableFunctionEntry,
+};
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_session::config::{BranchProtection, FunctionReturn, OptLevel, PAuthKey, PacRet};
 use rustc_symbol_mangling::mangle_internal_symbol;
 use rustc_target::spec::{FramePointer, SanitizerSet, StackProbeType, StackProtector};
 use smallvec::SmallVec;
 
-use crate::context::CodegenCx;
+use crate::context::SimpleCx;
 use crate::errors::SanitizerMemtagRequiresMte;
 use crate::llvm::AttributePlace::Function;
 use crate::llvm::{self, AllocKindFlags, Attribute, AttributeKind, AttributePlace, MemoryEffects};
 use crate::value::Value;
-use crate::{attributes, llvm_util};
+use crate::{Session, attributes, llvm_util};
 
 pub(crate) fn apply_to_llfn(llfn: &Value, idx: AttributePlace, attrs: &[&Attribute]) {
     if !attrs.is_empty() {
@@ -30,18 +31,19 @@ pub(crate) fn apply_to_callsite(callsite: &Value, idx: AttributePlace, attrs: &[
 
 /// Get LLVM attribute for the provided inline heuristic.
 pub(crate) fn inline_attr<'ll, 'tcx>(
-    cx: &CodegenCx<'ll, 'tcx>,
+    cx: &SimpleCx<'ll>,
+    tcx: TyCtxt<'tcx>,
     instance: ty::Instance<'tcx>,
 ) -> Option<&'ll Attribute> {
     // `optnone` requires `noinline`
-    let codegen_fn_attrs = cx.tcx.codegen_fn_attrs(instance.def_id());
+    let codegen_fn_attrs = 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,
+        (InlineAttr::None, _) if instance.def.requires_inline(tcx) => InlineAttr::Hint,
         (inline, _) => inline,
     };
 
-    if !cx.tcx.sess.opts.unstable_opts.inline_llvm {
+    if !tcx.sess.opts.unstable_opts.inline_llvm {
         // disable LLVM inlining
         return Some(AttributeKind::NoInline.create_attr(cx.llcx));
     }
@@ -51,7 +53,7 @@ pub(crate) fn inline_attr<'ll, 'tcx>(
             Some(AttributeKind::AlwaysInline.create_attr(cx.llcx))
         }
         InlineAttr::Never => {
-            if cx.sess().target.arch != "amdgpu" {
+            if tcx.sess.target.arch != "amdgpu" {
                 Some(AttributeKind::NoInline.create_attr(cx.llcx))
             } else {
                 None
@@ -63,12 +65,13 @@ pub(crate) fn inline_attr<'ll, 'tcx>(
 
 #[inline]
 fn patchable_function_entry_attrs<'ll>(
-    cx: &CodegenCx<'ll, '_>,
+    cx: &SimpleCx<'ll>,
+    sess: &Session,
     attr: Option<PatchableFunctionEntry>,
 ) -> SmallVec<[&'ll Attribute; 2]> {
     let mut attrs = SmallVec::new();
     let patchable_spec = attr.unwrap_or_else(|| {
-        PatchableFunctionEntry::from_config(cx.tcx.sess.opts.unstable_opts.patchable_function_entry)
+        PatchableFunctionEntry::from_config(sess.opts.unstable_opts.patchable_function_entry)
     });
     let entry = patchable_spec.entry();
     let prefix = patchable_spec.prefix();
@@ -91,12 +94,13 @@ fn patchable_function_entry_attrs<'ll>(
 
 /// Get LLVM sanitize attributes.
 #[inline]
-pub(crate) fn sanitize_attrs<'ll>(
-    cx: &CodegenCx<'ll, '_>,
+pub(crate) fn sanitize_attrs<'ll, 'tcx>(
+    cx: &SimpleCx<'ll>,
+    tcx: TyCtxt<'tcx>,
     no_sanitize: SanitizerSet,
 ) -> SmallVec<[&'ll Attribute; 4]> {
     let mut attrs = SmallVec::new();
-    let enabled = cx.tcx.sess.opts.unstable_opts.sanitizer - no_sanitize;
+    let enabled = tcx.sess.opts.unstable_opts.sanitizer - no_sanitize;
     if enabled.contains(SanitizerSet::ADDRESS) || enabled.contains(SanitizerSet::KERNELADDRESS) {
         attrs.push(llvm::AttributeKind::SanitizeAddress.create_attr(cx.llcx));
     }
@@ -114,11 +118,11 @@ pub(crate) fn sanitize_attrs<'ll>(
     }
     if enabled.contains(SanitizerSet::MEMTAG) {
         // Check to make sure the mte target feature is actually enabled.
-        let features = cx.tcx.global_backend_features(());
+        let features = tcx.global_backend_features(());
         let mte_feature =
             features.iter().map(|s| &s[..]).rfind(|n| ["+mte", "-mte"].contains(&&n[..]));
         if let None | Some("-mte") = mte_feature {
-            cx.tcx.dcx().emit_err(SanitizerMemtagRequiresMte);
+            tcx.dcx().emit_err(SanitizerMemtagRequiresMte);
         }
 
         attrs.push(llvm::AttributeKind::SanitizeMemTag.create_attr(cx.llcx));
@@ -139,9 +143,12 @@ pub(crate) fn uwtable_attr(llcx: &llvm::Context, use_sync_unwind: Option<bool>)
     llvm::CreateUWTableAttr(llcx, async_unwind)
 }
 
-pub(crate) fn frame_pointer_type_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> Option<&'ll Attribute> {
-    let mut fp = cx.sess().target.frame_pointer;
-    let opts = &cx.sess().opts;
+pub(crate) fn frame_pointer_type_attr<'ll>(
+    cx: &SimpleCx<'ll>,
+    sess: &Session,
+) -> Option<&'ll Attribute> {
+    let mut fp = sess.target.frame_pointer;
+    let opts = &sess.opts;
     // "mcount" function relies on stack pointer.
     // See <https://sourceware.org/binutils/docs/gprof/Implementation.html>.
     if opts.unstable_opts.instrument_mcount {
@@ -156,8 +163,8 @@ pub(crate) fn frame_pointer_type_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> Option<&'
     Some(llvm::CreateAttrStringValue(cx.llcx, "frame-pointer", attr_value))
 }
 
-fn function_return_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> Option<&'ll Attribute> {
-    let function_return_attr = match cx.sess().opts.unstable_opts.function_return {
+fn function_return_attr<'ll>(cx: &SimpleCx<'ll>, sess: &Session) -> Option<&'ll Attribute> {
+    let function_return_attr = match sess.opts.unstable_opts.function_return {
         FunctionReturn::Keep => return None,
         FunctionReturn::ThunkExtern => AttributeKind::FnRetThunkExtern,
     };
@@ -167,17 +174,20 @@ fn function_return_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> Option<&'ll Attribute>
 
 /// Tell LLVM what instrument function to insert.
 #[inline]
-fn instrument_function_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> SmallVec<[&'ll Attribute; 4]> {
+fn instrument_function_attr<'ll>(
+    cx: &SimpleCx<'ll>,
+    sess: &Session,
+) -> SmallVec<[&'ll Attribute; 4]> {
     let mut attrs = SmallVec::new();
-    if cx.sess().opts.unstable_opts.instrument_mcount {
+    if sess.opts.unstable_opts.instrument_mcount {
         // Similar to `clang -pg` behavior. Handled by the
         // `post-inline-ee-instrument` LLVM pass.
 
         // The function name varies on platforms.
         // See test/CodeGen/mcount.c in clang.
-        let mcount_name = match &cx.sess().target.llvm_mcount_intrinsic {
+        let mcount_name = match &sess.target.llvm_mcount_intrinsic {
             Some(llvm_mcount_intrinsic) => llvm_mcount_intrinsic.as_ref(),
-            None => cx.sess().target.mcount.as_ref(),
+            None => sess.target.mcount.as_ref(),
         };
 
         attrs.push(llvm::CreateAttrStringValue(
@@ -186,7 +196,7 @@ fn instrument_function_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> SmallVec<[&'ll Attr
             mcount_name,
         ));
     }
-    if let Some(options) = &cx.sess().opts.unstable_opts.instrument_xray {
+    if let Some(options) = &sess.opts.unstable_opts.instrument_xray {
         // XRay instrumentation is similar to __cyg_profile_func_{enter,exit}.
         // Function prologue and epilogue are instrumented with NOP sleds,
         // a runtime library later replaces them with detours into tracing code.
@@ -217,20 +227,20 @@ fn instrument_function_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> SmallVec<[&'ll Attr
     attrs
 }
 
-fn nojumptables_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> Option<&'ll Attribute> {
-    if !cx.sess().opts.unstable_opts.no_jump_tables {
+fn nojumptables_attr<'ll>(cx: &SimpleCx<'ll>, sess: &Session) -> Option<&'ll Attribute> {
+    if !sess.opts.unstable_opts.no_jump_tables {
         return None;
     }
 
     Some(llvm::CreateAttrStringValue(cx.llcx, "no-jump-tables", "true"))
 }
 
-fn probestack_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> Option<&'ll Attribute> {
+fn probestack_attr<'ll, 'tcx>(cx: &SimpleCx<'ll>, tcx: TyCtxt<'tcx>) -> Option<&'ll Attribute> {
     // Currently stack probes seem somewhat incompatible with the address
     // sanitizer and thread sanitizer. With asan we're already protected from
     // stack overflow anyway so we don't really need stack probes regardless.
-    if cx
-        .sess()
+    if tcx
+        .sess
         .opts
         .unstable_opts
         .sanitizer
@@ -240,22 +250,22 @@ fn probestack_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> Option<&'ll Attribute> {
     }
 
     // probestack doesn't play nice either with `-C profile-generate`.
-    if cx.sess().opts.cg.profile_generate.enabled() {
+    if tcx.sess.opts.cg.profile_generate.enabled() {
         return None;
     }
 
-    let attr_value = match cx.sess().target.stack_probes {
+    let attr_value = match tcx.sess.target.stack_probes {
         StackProbeType::None => return None,
         // Request LLVM to generate the probes inline. If the given LLVM version does not support
         // this, no probe is generated at all (even if the attribute is specified).
         StackProbeType::Inline => "inline-asm",
         // Flag our internal `__rust_probestack` function as the stack probe symbol.
         // This is defined in the `compiler-builtins` crate for each architecture.
-        StackProbeType::Call => &mangle_internal_symbol(cx.tcx, "__rust_probestack"),
+        StackProbeType::Call => &mangle_internal_symbol(tcx, "__rust_probestack"),
         // Pick from the two above based on the LLVM version.
         StackProbeType::InlineOrCall { min_llvm_version_for_inline } => {
             if llvm_util::get_version() < min_llvm_version_for_inline {
-                &mangle_internal_symbol(cx.tcx, "__rust_probestack")
+                &mangle_internal_symbol(tcx, "__rust_probestack")
             } else {
                 "inline-asm"
             }
@@ -264,8 +274,8 @@ fn probestack_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> Option<&'ll Attribute> {
     Some(llvm::CreateAttrStringValue(cx.llcx, "probe-stack", attr_value))
 }
 
-fn stackprotector_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> Option<&'ll Attribute> {
-    let sspattr = match cx.sess().stack_protector() {
+fn stackprotector_attr<'ll>(cx: &SimpleCx<'ll>, sess: &Session) -> Option<&'ll Attribute> {
+    let sspattr = match sess.stack_protector() {
         StackProtector::None => return None,
         StackProtector::All => AttributeKind::StackProtectReq,
         StackProtector::Strong => AttributeKind::StackProtectStrong,
@@ -275,33 +285,34 @@ fn stackprotector_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> Option<&'ll Attribute> {
     Some(sspattr.create_attr(cx.llcx))
 }
 
-fn backchain_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> Option<&'ll Attribute> {
-    if cx.sess().target.arch != "s390x" {
+fn backchain_attr<'ll>(cx: &SimpleCx<'ll>, sess: &Session) -> Option<&'ll Attribute> {
+    if sess.target.arch != "s390x" {
         return None;
     }
 
-    let requested_features = cx.sess().opts.cg.target_feature.split(',');
+    let requested_features = sess.opts.cg.target_feature.split(',');
     let found_positive = requested_features.clone().any(|r| r == "+backchain");
 
     if found_positive { Some(llvm::CreateAttrString(cx.llcx, "backchain")) } else { None }
 }
 
-pub(crate) fn target_cpu_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> &'ll Attribute {
-    let target_cpu = llvm_util::target_cpu(cx.tcx.sess);
+pub(crate) fn target_cpu_attr<'ll>(cx: &SimpleCx<'ll>, sess: &Session) -> &'ll Attribute {
+    let target_cpu = llvm_util::target_cpu(sess);
     llvm::CreateAttrStringValue(cx.llcx, "target-cpu", target_cpu)
 }
 
-pub(crate) fn tune_cpu_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> Option<&'ll Attribute> {
-    llvm_util::tune_cpu(cx.tcx.sess)
+pub(crate) fn tune_cpu_attr<'ll>(cx: &SimpleCx<'ll>, sess: &Session) -> Option<&'ll Attribute> {
+    llvm_util::tune_cpu(sess)
         .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, '_>,
+pub(crate) fn target_features_attr<'ll, 'tcx>(
+    cx: &SimpleCx<'ll>,
+    tcx: TyCtxt<'tcx>,
     function_features: Vec<String>,
 ) -> Option<&'ll Attribute> {
-    let global_features = cx.tcx.global_backend_features(()).iter().map(String::as_str);
+    let global_features = 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>();
@@ -311,22 +322,22 @@ pub(crate) fn target_features_attr<'ll>(
 
 /// 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> {
+pub(crate) fn non_lazy_bind_attr<'ll>(
+    cx: &SimpleCx<'ll>,
+    sess: &Session,
+) -> Option<&'ll Attribute> {
     // Don't generate calls through PLT if it's not necessary
-    if !cx.sess().needs_plt() {
-        Some(AttributeKind::NonLazyBind.create_attr(cx.llcx))
-    } else {
-        None
-    }
+    if !sess.needs_plt() { Some(AttributeKind::NonLazyBind.create_attr(cx.llcx)) } else { None }
 }
 
 /// Get the default optimizations attrs for a function.
 #[inline]
 pub(crate) fn default_optimisation_attrs<'ll>(
-    cx: &CodegenCx<'ll, '_>,
+    cx: &SimpleCx<'ll>,
+    sess: &Session,
 ) -> SmallVec<[&'ll Attribute; 2]> {
     let mut attrs = SmallVec::new();
-    match cx.sess().opts.optimize {
+    match sess.opts.optimize {
         OptLevel::Size => {
             attrs.push(llvm::AttributeKind::OptimizeForSize.create_attr(cx.llcx));
         }
@@ -347,17 +358,18 @@ fn create_alloc_family_attr(llcx: &llvm::Context) -> &llvm::Attribute {
 /// Composite function which sets LLVM attributes for function depending on its AST (`#[attribute]`)
 /// attributes.
 pub(crate) fn llfn_attrs_from_instance<'ll, 'tcx>(
-    cx: &CodegenCx<'ll, 'tcx>,
+    cx: &SimpleCx<'ll>,
+    tcx: TyCtxt<'tcx>,
     llfn: &'ll Value,
-    instance: ty::Instance<'tcx>,
+    codegen_fn_attrs: &CodegenFnAttrs,
+    instance: Option<ty::Instance<'tcx>>,
 ) {
-    let codegen_fn_attrs = cx.tcx.codegen_instance_attrs(instance.def);
-
+    let sess = tcx.sess;
     let mut to_add = SmallVec::<[_; 16]>::new();
 
     match codegen_fn_attrs.optimize {
         OptimizeAttr::Default => {
-            to_add.extend(default_optimisation_attrs(cx));
+            to_add.extend(default_optimisation_attrs(cx, sess));
         }
         OptimizeAttr::DoNotOptimize => {
             to_add.push(llvm::AttributeKind::OptimizeNone.create_attr(cx.llcx));
@@ -369,21 +381,21 @@ pub(crate) fn llfn_attrs_from_instance<'ll, 'tcx>(
         OptimizeAttr::Speed => {}
     }
 
-    if cx.sess().must_emit_unwind_tables() {
-        to_add.push(uwtable_attr(cx.llcx, cx.sess().opts.unstable_opts.use_sync_unwind));
+    if sess.must_emit_unwind_tables() {
+        to_add.push(uwtable_attr(cx.llcx, sess.opts.unstable_opts.use_sync_unwind));
     }
 
-    if cx.sess().opts.unstable_opts.profile_sample_use.is_some() {
+    if sess.opts.unstable_opts.profile_sample_use.is_some() {
         to_add.push(llvm::CreateAttrString(cx.llcx, "use-sample-profile"));
     }
 
     // FIXME: none of these functions interact with source level attributes.
-    to_add.extend(frame_pointer_type_attr(cx));
-    to_add.extend(function_return_attr(cx));
-    to_add.extend(instrument_function_attr(cx));
-    to_add.extend(nojumptables_attr(cx));
-    to_add.extend(probestack_attr(cx));
-    to_add.extend(stackprotector_attr(cx));
+    to_add.extend(frame_pointer_type_attr(cx, sess));
+    to_add.extend(function_return_attr(cx, sess));
+    to_add.extend(instrument_function_attr(cx, sess));
+    to_add.extend(nojumptables_attr(cx, sess));
+    to_add.extend(probestack_attr(cx, tcx));
+    to_add.extend(stackprotector_attr(cx, sess));
 
     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::NO_BUILTINS) {
         to_add.push(llvm::CreateAttrString(cx.llcx, "no-builtins"));
@@ -404,13 +416,13 @@ pub(crate) fn llfn_attrs_from_instance<'ll, 'tcx>(
         // not used.
     } else {
         // Do not set sanitizer attributes for naked functions.
-        to_add.extend(sanitize_attrs(cx, codegen_fn_attrs.no_sanitize));
+        to_add.extend(sanitize_attrs(cx, tcx, codegen_fn_attrs.no_sanitize));
 
         // For non-naked functions, set branch protection attributes on aarch64.
         if let Some(BranchProtection { bti, pac_ret, gcs }) =
-            cx.sess().opts.unstable_opts.branch_protection
+            sess.opts.unstable_opts.branch_protection
         {
-            assert!(cx.sess().target.arch == "aarch64");
+            assert!(sess.target.arch == "aarch64");
             if bti {
                 to_add.push(llvm::CreateAttrString(cx.llcx, "branch-target-enforcement"));
             }
@@ -438,14 +450,15 @@ pub(crate) fn llfn_attrs_from_instance<'ll, 'tcx>(
         || codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::ALLOCATOR_ZEROED)
     {
         to_add.push(create_alloc_family_attr(cx.llcx));
-        if let Some(zv) =
-            cx.tcx.get_attr(instance.def_id(), rustc_span::sym::rustc_allocator_zeroed_variant)
+        if let Some(instance) = instance
+            && let Some(zv) =
+                tcx.get_attr(instance.def_id(), rustc_span::sym::rustc_allocator_zeroed_variant)
             && let Some(name) = zv.value_str()
         {
             to_add.push(llvm::CreateAttrStringValue(
                 cx.llcx,
                 "alloc-variant-zeroed",
-                &mangle_internal_symbol(cx.tcx, name.as_str()),
+                &mangle_internal_symbol(tcx, name.as_str()),
             ));
         }
         // apply to argument place instead of function
@@ -490,18 +503,22 @@ pub(crate) fn llfn_attrs_from_instance<'ll, 'tcx>(
     if let Some(align) = codegen_fn_attrs.alignment {
         llvm::set_alignment(llfn, align);
     }
-    if let Some(backchain) = backchain_attr(cx) {
+    if let Some(backchain) = backchain_attr(cx, sess) {
         to_add.push(backchain);
     }
-    to_add.extend(patchable_function_entry_attrs(cx, codegen_fn_attrs.patchable_function_entry));
+    to_add.extend(patchable_function_entry_attrs(
+        cx,
+        sess,
+        codegen_fn_attrs.patchable_function_entry,
+    ));
 
     // Always annotate functions with the target-cpu they are compiled for.
     // Without this, ThinLTO won't inline Rust functions into Clang generated
     // functions (because Clang annotates functions this way too).
-    to_add.push(target_cpu_attr(cx));
+    to_add.push(target_cpu_attr(cx, sess));
     // tune-cpu is only conveyed through the attribute for our purpose.
     // The target doesn't care; the subtarget reads our attribute.
-    to_add.extend(tune_cpu_attr(cx));
+    to_add.extend(tune_cpu_attr(cx, sess));
 
     let function_features =
         codegen_fn_attrs.target_features.iter().map(|f| f.name.as_str()).collect::<Vec<&str>>();
@@ -509,7 +526,9 @@ pub(crate) fn llfn_attrs_from_instance<'ll, 'tcx>(
     // 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) {
+        if let Some(instance) = instance
+            && let Some(inline_attr) = inline_attr(cx, tcx, instance)
+        {
             to_add.push(inline_attr);
         }
     }
@@ -517,7 +536,7 @@ pub(crate) fn llfn_attrs_from_instance<'ll, 'tcx>(
     let function_features = function_features
         .iter()
         // Convert to LLVMFeatures and filter out unavailable ones
-        .flat_map(|feat| llvm_util::to_llvm_features(cx.tcx.sess, feat))
+        .flat_map(|feat| llvm_util::to_llvm_features(sess, feat))
         // Convert LLVMFeatures & dependencies to +<feats>s
         .flat_map(|feat| feat.into_iter().map(|f| format!("+{f}")))
         .chain(codegen_fn_attrs.instruction_set.iter().map(|x| match x {
@@ -526,20 +545,22 @@ pub(crate) fn llfn_attrs_from_instance<'ll, 'tcx>(
         }))
         .collect::<Vec<String>>();
 
-    if cx.tcx.sess.target.is_like_wasm {
+    if sess.target.is_like_wasm {
         // If this function is an import from the environment but the wasm
         // import has a specific module/name, apply them here.
-        if let Some(module) = wasm_import_module(cx.tcx, instance.def_id()) {
+        if let Some(instance) = instance
+            && let Some(module) = wasm_import_module(tcx, instance.def_id())
+        {
             to_add.push(llvm::CreateAttrStringValue(cx.llcx, "wasm-import-module", module));
 
             let name =
-                codegen_fn_attrs.symbol_name.unwrap_or_else(|| cx.tcx.item_name(instance.def_id()));
+                codegen_fn_attrs.symbol_name.unwrap_or_else(|| tcx.item_name(instance.def_id()));
             let name = name.as_str();
             to_add.push(llvm::CreateAttrStringValue(cx.llcx, "wasm-import-name", name));
         }
     }
 
-    to_add.extend(target_features_attr(cx, function_features));
+    to_add.extend(target_features_attr(cx, tcx, 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 78107d95e5a..5ac3a87c158 100644
--- a/compiler/rustc_codegen_llvm/src/back/lto.rs
+++ b/compiler/rustc_codegen_llvm/src/back/lto.rs
@@ -563,6 +563,8 @@ fn enable_autodiff_settings(ad: &[config::AutoDiff]) {
             config::AutoDiff::Enable => {}
             // We handle this below
             config::AutoDiff::NoPostopt => {}
+            // Disables TypeTree generation
+            config::AutoDiff::NoTT => {}
         }
     }
     // This helps with handling enums for now.
diff --git a/compiler/rustc_codegen_llvm/src/base.rs b/compiler/rustc_codegen_llvm/src/base.rs
index 978134cc32b..6d12b511e9c 100644
--- a/compiler/rustc_codegen_llvm/src/base.rs
+++ b/compiler/rustc_codegen_llvm/src/base.rs
@@ -105,7 +105,7 @@ pub(crate) fn compile_codegen_unit(
             if let Some(entry) =
                 maybe_create_entry_wrapper::<Builder<'_, '_, '_>>(&cx, cx.codegen_unit)
             {
-                let attrs = attributes::sanitize_attrs(&cx, SanitizerSet::empty());
+                let attrs = attributes::sanitize_attrs(&cx, tcx, SanitizerSet::empty());
                 attributes::apply_to_llfn(entry, llvm::AttributePlace::Function, &attrs);
             }
 
diff --git a/compiler/rustc_codegen_llvm/src/builder.rs b/compiler/rustc_codegen_llvm/src/builder.rs
index 0f17cc9063a..5271d0b4bb8 100644
--- a/compiler/rustc_codegen_llvm/src/builder.rs
+++ b/compiler/rustc_codegen_llvm/src/builder.rs
@@ -2,6 +2,7 @@ use std::borrow::{Borrow, Cow};
 use std::ops::Deref;
 use std::{iter, ptr};
 
+use rustc_ast::expand::typetree::FncTree;
 pub(crate) mod autodiff;
 pub(crate) mod gpu_offload;
 
@@ -1107,11 +1108,12 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         src_align: Align,
         size: &'ll Value,
         flags: MemFlags,
+        tt: Option<FncTree>,
     ) {
         assert!(!flags.contains(MemFlags::NONTEMPORAL), "non-temporal memcpy not supported");
         let size = self.intcast(size, self.type_isize(), false);
         let is_volatile = flags.contains(MemFlags::VOLATILE);
-        unsafe {
+        let memcpy = unsafe {
             llvm::LLVMRustBuildMemCpy(
                 self.llbuilder,
                 dst,
@@ -1120,7 +1122,16 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
                 src_align.bytes() as c_uint,
                 size,
                 is_volatile,
-            );
+            )
+        };
+
+        // TypeTree metadata for memcpy is especially important: when Enzyme encounters
+        // a memcpy during autodiff, it needs to know the structure of the data being
+        // copied to properly track derivatives. For example, copying an array of floats
+        // vs. copying a struct with mixed types requires different derivative handling.
+        // The TypeTree tells Enzyme exactly what memory layout to expect.
+        if let Some(tt) = tt {
+            crate::typetree::add_tt(self.cx().llmod, self.cx().llcx, memcpy, tt);
         }
     }
 
@@ -1433,7 +1444,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
                 // 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)
+                && let Some(inlining_rule) = attributes::inline_attr(&self.cx, self.cx.tcx, instance)
                 && self.cx.tcx.is_target_feature_call_safe(
                     &fn_call_attrs.target_features,
                     &fn_defn_attrs.target_features,
diff --git a/compiler/rustc_codegen_llvm/src/builder/autodiff.rs b/compiler/rustc_codegen_llvm/src/builder/autodiff.rs
index b66e3dfdeec..4a749642265 100644
--- a/compiler/rustc_codegen_llvm/src/builder/autodiff.rs
+++ b/compiler/rustc_codegen_llvm/src/builder/autodiff.rs
@@ -1,6 +1,7 @@
 use std::ptr;
 
 use rustc_ast::expand::autodiff_attrs::{AutoDiffAttrs, DiffActivity, DiffMode};
+use rustc_ast::expand::typetree::FncTree;
 use rustc_codegen_ssa::common::TypeKind;
 use rustc_codegen_ssa::traits::{BaseTypeCodegenMethods, BuilderMethods};
 use rustc_middle::ty::{Instance, PseudoCanonicalInput, TyCtxt, TypingEnv};
@@ -294,6 +295,7 @@ pub(crate) fn generate_enzyme_call<'ll, 'tcx>(
     fn_args: &[&'ll Value],
     attrs: AutoDiffAttrs,
     dest: PlaceRef<'tcx, &'ll Value>,
+    fnc_tree: FncTree,
 ) {
     // We have to pick the name depending on whether we want forward or reverse mode autodiff.
     let mut ad_name: String = match attrs.mode {
@@ -370,7 +372,18 @@ pub(crate) fn generate_enzyme_call<'ll, 'tcx>(
         fn_args,
     );
 
+    if !fnc_tree.args.is_empty() || !fnc_tree.ret.0.is_empty() {
+        crate::typetree::add_tt(cx.llmod, cx.llcx, fn_to_diff, fnc_tree);
+    }
+
     let call = builder.call(enzyme_ty, None, None, ad_fn, &args, None, None);
 
-    builder.store_to_place(call, dest.val);
+    let fn_ret_ty = builder.cx.val_ty(call);
+    if fn_ret_ty != builder.cx.type_void() && fn_ret_ty != builder.cx.type_struct(&[], false) {
+        // If we return void or an empty struct, then our caller (due to how we generated it)
+        // does not expect a return value. As such, we have no pointer (or place) into which
+        // we could store our value, and would store into an undef, which would cause UB.
+        // As such, we just ignore the return value in those cases.
+        builder.store_to_place(call, dest.val);
+    }
 }
diff --git a/compiler/rustc_codegen_llvm/src/consts.rs b/compiler/rustc_codegen_llvm/src/consts.rs
index a110ecbb75d..40375ef6510 100644
--- a/compiler/rustc_codegen_llvm/src/consts.rs
+++ b/compiler/rustc_codegen_llvm/src/consts.rs
@@ -564,7 +564,7 @@ impl<'ll> CodegenCx<'ll, '_> {
         let g = self.define_global(&sym, llty).unwrap_or_else(|| {
             bug!("symbol `{}` is already defined", sym);
         });
-        set_global_alignment(self, g, self.tcx.data_layout.i8_align.abi);
+        set_global_alignment(self, g, self.tcx.data_layout.i8_align);
         llvm::set_initializer(g, llval);
         llvm::set_linkage(g, llvm::Linkage::PrivateLinkage);
         llvm::set_section(g, c"__TEXT,__cstring,cstring_literals");
@@ -680,7 +680,7 @@ impl<'ll> CodegenCx<'ll, '_> {
         let methname_g = self.define_global(&methname_sym, methname_llty).unwrap_or_else(|| {
             bug!("symbol `{}` is already defined", methname_sym);
         });
-        set_global_alignment(self, methname_g, self.tcx.data_layout.i8_align.abi);
+        set_global_alignment(self, methname_g, self.tcx.data_layout.i8_align);
         llvm::set_initializer(methname_g, methname_llval);
         llvm::set_linkage(methname_g, llvm::Linkage::PrivateLinkage);
         llvm::set_section(
diff --git a/compiler/rustc_codegen_llvm/src/context.rs b/compiler/rustc_codegen_llvm/src/context.rs
index b7d2241da47..b1da6f7c740 100644
--- a/compiler/rustc_codegen_llvm/src/context.rs
+++ b/compiler/rustc_codegen_llvm/src/context.rs
@@ -34,7 +34,7 @@ use smallvec::SmallVec;
 use crate::back::write::to_llvm_code_model;
 use crate::callee::get_fn;
 use crate::debuginfo::metadata::apply_vcall_visibility_metadata;
-use crate::llvm::Metadata;
+use crate::llvm::{Metadata, MetadataKindId};
 use crate::type_::Type;
 use crate::value::Value;
 use crate::{attributes, common, coverageinfo, debuginfo, llvm, llvm_util};
@@ -876,7 +876,7 @@ impl<'ll, 'tcx> MiscCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
                 } else {
                     let fty = self.type_variadic_func(&[], self.type_i32());
                     let llfn = self.declare_cfn(name, llvm::UnnamedAddr::Global, fty);
-                    let target_cpu = attributes::target_cpu_attr(self);
+                    let target_cpu = attributes::target_cpu_attr(self, self.sess());
                     attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &[target_cpu]);
                     llfn
                 }
@@ -891,15 +891,15 @@ impl<'ll, 'tcx> MiscCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
     }
 
     fn set_frame_pointer_type(&self, llfn: &'ll Value) {
-        if let Some(attr) = attributes::frame_pointer_type_attr(self) {
+        if let Some(attr) = attributes::frame_pointer_type_attr(self, self.sess()) {
             attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &[attr]);
         }
     }
 
     fn apply_target_cpu_attr(&self, llfn: &'ll Value) {
         let mut attrs = SmallVec::<[_; 2]>::new();
-        attrs.push(attributes::target_cpu_attr(self));
-        attrs.extend(attributes::tune_cpu_attr(self));
+        attrs.push(attributes::target_cpu_attr(self, self.sess()));
+        attrs.extend(attributes::tune_cpu_attr(self, self.sess()));
         attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &attrs);
     }
 
@@ -918,7 +918,7 @@ impl<'ll, 'tcx> MiscCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
             attributes::apply_to_llfn(
                 llfn,
                 llvm::AttributePlace::Function,
-                attributes::target_features_attr(self, vec![]).as_slice(),
+                attributes::target_features_attr(self, self.tcx, vec![]).as_slice(),
             );
             Some(llfn)
         } else {
@@ -1006,11 +1006,11 @@ impl<'ll, CX: Borrow<SCx<'ll>>> GenericCx<'ll, CX> {
     pub(crate) fn set_metadata<'a>(
         &self,
         val: &'a Value,
-        kind_id: impl Into<llvm::MetadataKindId>,
+        kind_id: MetadataKindId,
         md: &'ll Metadata,
     ) {
         let node = self.get_metadata_value(md);
-        llvm::LLVMSetMetadata(val, kind_id.into(), node);
+        llvm::LLVMSetMetadata(val, kind_id, node);
     }
 }
 
diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/llvm_cov.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/llvm_cov.rs
index bc4f6bb6a82..d50eb533ffd 100644
--- a/compiler/rustc_codegen_llvm/src/coverageinfo/llvm_cov.rs
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/llvm_cov.rs
@@ -2,26 +2,25 @@
 
 use std::ffi::CString;
 
-use crate::common::AsCCharPtr;
 use crate::coverageinfo::ffi;
 use crate::llvm;
 
 pub(crate) fn covmap_var_name() -> CString {
-    CString::new(llvm::build_byte_buffer(|s| unsafe {
+    CString::new(llvm::build_byte_buffer(|s| {
         llvm::LLVMRustCoverageWriteCovmapVarNameToString(s);
     }))
     .expect("covmap variable name should not contain NUL")
 }
 
 pub(crate) fn covmap_section_name(llmod: &llvm::Module) -> CString {
-    CString::new(llvm::build_byte_buffer(|s| unsafe {
+    CString::new(llvm::build_byte_buffer(|s| {
         llvm::LLVMRustCoverageWriteCovmapSectionNameToString(llmod, s);
     }))
     .expect("covmap section name should not contain NUL")
 }
 
 pub(crate) fn covfun_section_name(llmod: &llvm::Module) -> CString {
-    CString::new(llvm::build_byte_buffer(|s| unsafe {
+    CString::new(llvm::build_byte_buffer(|s| {
         llvm::LLVMRustCoverageWriteCovfunSectionNameToString(llmod, s);
     }))
     .expect("covfun section name should not contain NUL")
@@ -34,7 +33,7 @@ pub(crate) fn create_pgo_func_name_var<'ll>(
     unsafe {
         llvm::LLVMRustCoverageCreatePGOFuncNameVar(
             llfn,
-            mangled_fn_name.as_c_char_ptr(),
+            mangled_fn_name.as_ptr(),
             mangled_fn_name.len(),
         )
     }
@@ -44,7 +43,7 @@ pub(crate) fn write_filenames_to_buffer(filenames: &[impl AsRef<str>]) -> Vec<u8
     let (pointers, lengths) = filenames
         .into_iter()
         .map(AsRef::as_ref)
-        .map(|s: &str| (s.as_c_char_ptr(), s.len()))
+        .map(|s: &str| (s.as_ptr(), s.len()))
         .unzip::<_, _, Vec<_>, Vec<_>>();
 
     llvm::build_byte_buffer(|buffer| unsafe {
@@ -89,12 +88,12 @@ pub(crate) fn write_function_mappings_to_buffer(
 /// Hashes some bytes into a 64-bit hash, via LLVM's `IndexedInstrProf::ComputeHash`,
 /// as required for parts of the LLVM coverage mapping format.
 pub(crate) fn hash_bytes(bytes: &[u8]) -> u64 {
-    unsafe { llvm::LLVMRustCoverageHashBytes(bytes.as_c_char_ptr(), bytes.len()) }
+    unsafe { llvm::LLVMRustCoverageHashBytes(bytes.as_ptr(), bytes.len()) }
 }
 
 /// Returns LLVM's `coverage::CovMapVersion::CurrentVersion` (CoverageMapping.h)
 /// as a raw numeric value. For historical reasons, the numeric value is 1 less
 /// than the number in the version's name, so `Version7` is actually `6u32`.
 pub(crate) fn mapping_version() -> u32 {
-    unsafe { llvm::LLVMRustCoverageMappingVersion() }
+    llvm::LLVMRustCoverageMappingVersion()
 }
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs b/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs
index 7a6dc008c7b..3081badb821 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs
@@ -2,9 +2,9 @@
 
 use rustc_codegen_ssa::base::collect_debugger_visualizers_transitive;
 use rustc_codegen_ssa::traits::*;
+use rustc_hir::attrs::DebuggerVisualizerType;
 use rustc_hir::def_id::LOCAL_CRATE;
 use rustc_middle::bug;
-use rustc_middle::middle::debugger_visualizer::DebuggerVisualizerType;
 use rustc_session::config::{CrateType, DebugInfo};
 
 use crate::builder::Builder;
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
index 4ba72cd61a0..bc20c759413 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
@@ -117,7 +117,7 @@ fn build_fixed_size_array_di_node<'ll, 'tcx>(
         .try_to_target_usize(cx.tcx)
         .expect("expected monomorphic const in codegen") as c_longlong;
 
-    let subrange = unsafe { llvm::LLVMRustDIBuilderGetOrCreateSubrange(DIB(cx), 0, upper_bound) };
+    let subrange = unsafe { llvm::LLVMDIBuilderGetOrCreateSubrange(DIB(cx), 0, upper_bound) };
     let subscripts = &[subrange];
 
     let di_node = unsafe {
@@ -1043,7 +1043,7 @@ fn create_member_type<'ll, 'tcx>(
             file_metadata,
             line_number,
             layout.size.bits(),
-            layout.align.abi.bits() as u32,
+            layout.align.bits() as u32,
             offset.bits(),
             flags,
             type_di_node,
@@ -1611,16 +1611,12 @@ pub(crate) fn apply_vcall_visibility_metadata<'ll, 'tcx>(
         let v = [llvm::LLVMValueAsMetadata(cx.const_usize(0)), typeid];
         llvm::LLVMRustGlobalAddMetadata(
             vtable,
-            llvm::MD_type as c_uint,
+            llvm::MD_type,
             llvm::LLVMMDNodeInContext2(cx.llcx, v.as_ptr(), v.len()),
         );
         let vcall_visibility = llvm::LLVMValueAsMetadata(cx.const_u64(vcall_visibility as u64));
         let vcall_visibility_metadata = llvm::LLVMMDNodeInContext2(cx.llcx, &vcall_visibility, 1);
-        llvm::LLVMGlobalSetMetadata(
-            vtable,
-            llvm::MetadataType::MD_vcall_visibility as c_uint,
-            vcall_visibility_metadata,
-        );
+        llvm::LLVMGlobalSetMetadata(vtable, llvm::MD_vcall_visibility, vcall_visibility_metadata);
     }
 }
 
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/native.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/native.rs
index 62d38d463ab..1ae6e6e5eec 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/native.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/native.rs
@@ -289,7 +289,7 @@ fn build_enum_variant_part_di_node<'ll, 'tcx>(
                 file_metadata,
                 line_number,
                 enum_type_and_layout.size.bits(),
-                enum_type_and_layout.align.abi.bits() as u32,
+                enum_type_and_layout.align.bits() as u32,
                 DIFlags::FlagZero,
                 tag_member_di_node,
                 create_DIArray(DIB(cx), &[]),
@@ -449,7 +449,7 @@ fn build_enum_variant_member_di_node<'ll, 'tcx>(
             file_di_node,
             line_number,
             enum_type_and_layout.size.bits(),
-            enum_type_and_layout.align.abi.bits() as u32,
+            enum_type_and_layout.align.bits() as u32,
             Size::ZERO.bits(),
             discr,
             DIFlags::FlagZero,
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs b/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
index 126082aa3aa..af64e4ebed0 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
@@ -52,15 +52,6 @@ mod utils;
 use self::create_scope_map::compute_mir_scopes;
 pub(crate) use self::metadata::build_global_var_di_node;
 
-// FIXME(Zalathar): These `DW_TAG_*` constants are fake values that were
-// removed from LLVM in 2015, and are only used by our own `RustWrapper.cpp`
-// to decide which C++ API to call. Instead, we should just have two separate
-// FFI functions and choose the correct one on the Rust side.
-#[allow(non_upper_case_globals)]
-const DW_TAG_auto_variable: c_uint = 0x100;
-#[allow(non_upper_case_globals)]
-const DW_TAG_arg_variable: c_uint = 0x101;
-
 /// A context object for maintaining all state needed by the debuginfo module.
 pub(crate) struct CodegenUnitDebugContext<'ll, 'tcx> {
     llmod: &'ll llvm::Module,
@@ -174,35 +165,38 @@ impl<'ll> DebugInfoBuilderMethods for Builder<'_, 'll, '_> {
 
         if direct_offset.bytes() > 0 {
             addr_ops.push(DW_OP_plus_uconst);
-            addr_ops.push(direct_offset.bytes() as u64);
+            addr_ops.push(direct_offset.bytes());
         }
         for &offset in indirect_offsets {
             addr_ops.push(DW_OP_deref);
             if offset.bytes() > 0 {
                 addr_ops.push(DW_OP_plus_uconst);
-                addr_ops.push(offset.bytes() as u64);
+                addr_ops.push(offset.bytes());
             }
         }
         if let Some(fragment) = fragment {
             // `DW_OP_LLVM_fragment` takes as arguments the fragment's
             // offset and size, both of them in bits.
             addr_ops.push(DW_OP_LLVM_fragment);
-            addr_ops.push(fragment.start.bits() as u64);
-            addr_ops.push((fragment.end - fragment.start).bits() as u64);
+            addr_ops.push(fragment.start.bits());
+            addr_ops.push((fragment.end - fragment.start).bits());
         }
 
+        let di_builder = DIB(self.cx());
+        let addr_expr = unsafe {
+            llvm::LLVMDIBuilderCreateExpression(di_builder, addr_ops.as_ptr(), addr_ops.len())
+        };
         unsafe {
             // FIXME(eddyb) replace `llvm.dbg.declare` with `llvm.dbg.addr`.
-            llvm::LLVMRustDIBuilderInsertDeclareAtEnd(
-                DIB(self.cx()),
+            llvm::LLVMDIBuilderInsertDeclareRecordAtEnd(
+                di_builder,
                 variable_alloca,
                 dbg_var,
-                addr_ops.as_ptr(),
-                addr_ops.len() as c_uint,
+                addr_expr,
                 dbg_loc,
                 self.llbb(),
-            );
-        }
+            )
+        };
     }
 
     fn set_dbg_loc(&mut self, dbg_loc: &'ll DILocation) {
@@ -630,28 +624,39 @@ impl<'ll, 'tcx> DebugInfoCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
 
         let type_metadata = spanned_type_di_node(self, variable_type, span);
 
-        let (argument_index, dwarf_tag) = match variable_kind {
-            ArgumentVariable(index) => (index as c_uint, DW_TAG_arg_variable),
-            LocalVariable => (0, DW_TAG_auto_variable),
-        };
         let align = self.align_of(variable_type);
 
         let name = variable_name.as_str();
-        unsafe {
-            llvm::LLVMRustDIBuilderCreateVariable(
-                DIB(self),
-                dwarf_tag,
-                scope_metadata,
-                name.as_c_char_ptr(),
-                name.len(),
-                file_metadata,
-                loc.line,
-                type_metadata,
-                true,
-                DIFlags::FlagZero,
-                argument_index,
-                align.bits() as u32,
-            )
+
+        match variable_kind {
+            ArgumentVariable(arg_index) => unsafe {
+                llvm::LLVMDIBuilderCreateParameterVariable(
+                    DIB(self),
+                    scope_metadata,
+                    name.as_ptr(),
+                    name.len(),
+                    arg_index as c_uint,
+                    file_metadata,
+                    loc.line,
+                    type_metadata,
+                    llvm::Bool::TRUE, // (preserve descriptor during optimizations)
+                    DIFlags::FlagZero,
+                )
+            },
+            LocalVariable => unsafe {
+                llvm::LLVMDIBuilderCreateAutoVariable(
+                    DIB(self),
+                    scope_metadata,
+                    name.as_ptr(),
+                    name.len(),
+                    file_metadata,
+                    loc.line,
+                    type_metadata,
+                    llvm::Bool::TRUE, // (preserve descriptor during optimizations)
+                    DIFlags::FlagZero,
+                    align.bits() as u32,
+                )
+            },
         }
     }
 }
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/utils.rs b/compiler/rustc_codegen_llvm/src/debuginfo/utils.rs
index cc1d504b430..7e1e49310f6 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/utils.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/utils.rs
@@ -28,7 +28,7 @@ pub(crate) fn create_DIArray<'ll>(
     builder: &DIBuilder<'ll>,
     arr: &[Option<&'ll DIDescriptor>],
 ) -> &'ll DIArray {
-    unsafe { llvm::LLVMRustDIBuilderGetOrCreateArray(builder, arr.as_ptr(), arr.len() as u32) }
+    unsafe { llvm::LLVMDIBuilderGetOrCreateArray(builder, arr.as_ptr(), arr.len()) }
 }
 
 #[inline]
diff --git a/compiler/rustc_codegen_llvm/src/declare.rs b/compiler/rustc_codegen_llvm/src/declare.rs
index 960a895a203..36cdb498839 100644
--- a/compiler/rustc_codegen_llvm/src/declare.rs
+++ b/compiler/rustc_codegen_llvm/src/declare.rs
@@ -76,7 +76,7 @@ pub(crate) fn declare_raw_fn<'ll, 'tcx>(
         attrs.push(llvm::AttributeKind::NoRedZone.create_attr(cx.llcx));
     }
 
-    attrs.extend(attributes::non_lazy_bind_attr(cx));
+    attrs.extend(attributes::non_lazy_bind_attr(cx, cx.tcx.sess));
 
     attributes::apply_to_llfn(llfn, Function, &attrs);
 
diff --git a/compiler/rustc_codegen_llvm/src/intrinsic.rs b/compiler/rustc_codegen_llvm/src/intrinsic.rs
index 50398a32142..467655b0bfc 100644
--- a/compiler/rustc_codegen_llvm/src/intrinsic.rs
+++ b/compiler/rustc_codegen_llvm/src/intrinsic.rs
@@ -297,7 +297,7 @@ impl<'ll, 'tcx> IntrinsicCallBuilderMethods<'tcx> for Builder<'_, 'll, 'tcx> {
                 let align = if name == sym::unaligned_volatile_load {
                     1
                 } else {
-                    result.layout.align.abi.bytes() as u32
+                    result.layout.align.bytes() as u32
                 };
                 unsafe {
                     llvm::LLVMSetAlignment(load, align);
@@ -1047,7 +1047,7 @@ fn codegen_emcc_try<'ll, 'tcx>(
         // create an alloca and pass a pointer to that.
         let ptr_size = bx.tcx().data_layout.pointer_size();
         let ptr_align = bx.tcx().data_layout.pointer_align().abi;
-        let i8_align = bx.tcx().data_layout.i8_align.abi;
+        let i8_align = bx.tcx().data_layout.i8_align;
         // Required in order for there to be no padding between the fields.
         assert!(i8_align <= ptr_align);
         let catch_data = bx.alloca(2 * ptr_size, ptr_align);
@@ -1212,6 +1212,9 @@ fn codegen_autodiff<'ll, 'tcx>(
         &mut diff_attrs.input_activity,
     );
 
+    let fnc_tree =
+        rustc_middle::ty::fnc_typetrees(tcx, fn_source.ty(tcx, TypingEnv::fully_monomorphized()));
+
     // Build body
     generate_enzyme_call(
         bx,
@@ -1222,6 +1225,7 @@ fn codegen_autodiff<'ll, 'tcx>(
         &val_arr,
         diff_attrs.clone(),
         result,
+        fnc_tree,
     );
 }
 
diff --git a/compiler/rustc_codegen_llvm/src/lib.rs b/compiler/rustc_codegen_llvm/src/lib.rs
index 13bdb7cb1a2..2405a25c702 100644
--- a/compiler/rustc_codegen_llvm/src/lib.rs
+++ b/compiler/rustc_codegen_llvm/src/lib.rs
@@ -68,6 +68,7 @@ mod llvm_util;
 mod mono_item;
 mod type_;
 mod type_of;
+mod typetree;
 mod va_arg;
 mod value;
 
@@ -231,6 +232,10 @@ impl CodegenBackend for LlvmCodegenBackend {
         crate::DEFAULT_LOCALE_RESOURCE
     }
 
+    fn name(&self) -> &'static str {
+        "llvm"
+    }
+
     fn init(&self, sess: &Session) {
         llvm_util::init(sess); // Make sure llvm is inited
     }
@@ -349,7 +354,14 @@ impl CodegenBackend for LlvmCodegenBackend {
 
         // Run the linker on any artifacts that resulted from the LLVM run.
         // This should produce either a finished executable or library.
-        link_binary(sess, &LlvmArchiveBuilderBuilder, codegen_results, metadata, outputs);
+        link_binary(
+            sess,
+            &LlvmArchiveBuilderBuilder,
+            codegen_results,
+            metadata,
+            outputs,
+            self.name(),
+        );
     }
 }
 
diff --git a/compiler/rustc_codegen_llvm/src/llvm/enzyme_ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/enzyme_ffi.rs
index 695435eb6da..e63043b2122 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/enzyme_ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/enzyme_ffi.rs
@@ -3,9 +3,36 @@
 use libc::{c_char, c_uint};
 
 use super::MetadataKindId;
-use super::ffi::{AttributeKind, BasicBlock, Metadata, Module, Type, Value};
+use super::ffi::{AttributeKind, BasicBlock, Context, Metadata, Module, Type, Value};
 use crate::llvm::{Bool, Builder};
 
+// TypeTree types
+pub(crate) type CTypeTreeRef = *mut EnzymeTypeTree;
+
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub(crate) struct EnzymeTypeTree {
+    _unused: [u8; 0],
+}
+
+#[repr(u32)]
+#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
+#[allow(non_camel_case_types)]
+pub(crate) enum CConcreteType {
+    DT_Anything = 0,
+    DT_Integer = 1,
+    DT_Pointer = 2,
+    DT_Half = 3,
+    DT_Float = 4,
+    DT_Double = 5,
+    DT_Unknown = 6,
+    DT_FP128 = 9,
+}
+
+pub(crate) struct TypeTree {
+    pub(crate) inner: CTypeTreeRef,
+}
+
 #[link(name = "llvm-wrapper", kind = "static")]
 unsafe extern "C" {
     // Enzyme
@@ -68,10 +95,40 @@ pub(crate) mod Enzyme_AD {
 
     use libc::c_void;
 
+    use super::{CConcreteType, CTypeTreeRef, Context};
+
     unsafe extern "C" {
         pub(crate) fn EnzymeSetCLBool(arg1: *mut ::std::os::raw::c_void, arg2: u8);
         pub(crate) fn EnzymeSetCLString(arg1: *mut ::std::os::raw::c_void, arg2: *const c_char);
     }
+
+    // TypeTree functions
+    unsafe extern "C" {
+        pub(crate) fn EnzymeNewTypeTree() -> CTypeTreeRef;
+        pub(crate) fn EnzymeNewTypeTreeCT(arg1: CConcreteType, ctx: &Context) -> CTypeTreeRef;
+        pub(crate) fn EnzymeNewTypeTreeTR(arg1: CTypeTreeRef) -> CTypeTreeRef;
+        pub(crate) fn EnzymeFreeTypeTree(CTT: CTypeTreeRef);
+        pub(crate) fn EnzymeMergeTypeTree(arg1: CTypeTreeRef, arg2: CTypeTreeRef) -> bool;
+        pub(crate) fn EnzymeTypeTreeOnlyEq(arg1: CTypeTreeRef, pos: i64);
+        pub(crate) fn EnzymeTypeTreeData0Eq(arg1: CTypeTreeRef);
+        pub(crate) fn EnzymeTypeTreeShiftIndiciesEq(
+            arg1: CTypeTreeRef,
+            data_layout: *const c_char,
+            offset: i64,
+            max_size: i64,
+            add_offset: u64,
+        );
+        pub(crate) fn EnzymeTypeTreeInsertEq(
+            CTT: CTypeTreeRef,
+            indices: *const i64,
+            len: usize,
+            ct: CConcreteType,
+            ctx: &Context,
+        );
+        pub(crate) fn EnzymeTypeTreeToString(arg1: CTypeTreeRef) -> *const c_char;
+        pub(crate) fn EnzymeTypeTreeToStringFree(arg1: *const c_char);
+    }
+
     unsafe extern "C" {
         static mut EnzymePrintPerf: c_void;
         static mut EnzymePrintActivity: c_void;
@@ -141,6 +198,67 @@ pub(crate) use self::Fallback_AD::*;
 pub(crate) mod Fallback_AD {
     #![allow(unused_variables)]
 
+    use libc::c_char;
+
+    use super::{CConcreteType, CTypeTreeRef, Context};
+
+    // TypeTree function fallbacks
+    pub(crate) unsafe fn EnzymeNewTypeTree() -> CTypeTreeRef {
+        unimplemented!()
+    }
+
+    pub(crate) unsafe fn EnzymeNewTypeTreeCT(arg1: CConcreteType, ctx: &Context) -> CTypeTreeRef {
+        unimplemented!()
+    }
+
+    pub(crate) unsafe fn EnzymeNewTypeTreeTR(arg1: CTypeTreeRef) -> CTypeTreeRef {
+        unimplemented!()
+    }
+
+    pub(crate) unsafe fn EnzymeFreeTypeTree(CTT: CTypeTreeRef) {
+        unimplemented!()
+    }
+
+    pub(crate) unsafe fn EnzymeMergeTypeTree(arg1: CTypeTreeRef, arg2: CTypeTreeRef) -> bool {
+        unimplemented!()
+    }
+
+    pub(crate) unsafe fn EnzymeTypeTreeOnlyEq(arg1: CTypeTreeRef, pos: i64) {
+        unimplemented!()
+    }
+
+    pub(crate) unsafe fn EnzymeTypeTreeData0Eq(arg1: CTypeTreeRef) {
+        unimplemented!()
+    }
+
+    pub(crate) unsafe fn EnzymeTypeTreeShiftIndiciesEq(
+        arg1: CTypeTreeRef,
+        data_layout: *const c_char,
+        offset: i64,
+        max_size: i64,
+        add_offset: u64,
+    ) {
+        unimplemented!()
+    }
+
+    pub(crate) unsafe fn EnzymeTypeTreeInsertEq(
+        CTT: CTypeTreeRef,
+        indices: *const i64,
+        len: usize,
+        ct: CConcreteType,
+        ctx: &Context,
+    ) {
+        unimplemented!()
+    }
+
+    pub(crate) unsafe fn EnzymeTypeTreeToString(arg1: CTypeTreeRef) -> *const c_char {
+        unimplemented!()
+    }
+
+    pub(crate) unsafe fn EnzymeTypeTreeToStringFree(arg1: *const c_char) {
+        unimplemented!()
+    }
+
     pub(crate) fn set_inline(val: bool) {
         unimplemented!()
     }
@@ -169,3 +287,89 @@ pub(crate) mod Fallback_AD {
         unimplemented!()
     }
 }
+
+impl TypeTree {
+    pub(crate) fn new() -> TypeTree {
+        let inner = unsafe { EnzymeNewTypeTree() };
+        TypeTree { inner }
+    }
+
+    pub(crate) fn from_type(t: CConcreteType, ctx: &Context) -> TypeTree {
+        let inner = unsafe { EnzymeNewTypeTreeCT(t, ctx) };
+        TypeTree { inner }
+    }
+
+    pub(crate) fn merge(self, other: Self) -> Self {
+        unsafe {
+            EnzymeMergeTypeTree(self.inner, other.inner);
+        }
+        drop(other);
+        self
+    }
+
+    #[must_use]
+    pub(crate) fn shift(
+        self,
+        layout: &str,
+        offset: isize,
+        max_size: isize,
+        add_offset: usize,
+    ) -> Self {
+        let layout = std::ffi::CString::new(layout).unwrap();
+
+        unsafe {
+            EnzymeTypeTreeShiftIndiciesEq(
+                self.inner,
+                layout.as_ptr(),
+                offset as i64,
+                max_size as i64,
+                add_offset as u64,
+            );
+        }
+
+        self
+    }
+
+    pub(crate) fn insert(&mut self, indices: &[i64], ct: CConcreteType, ctx: &Context) {
+        unsafe {
+            EnzymeTypeTreeInsertEq(self.inner, indices.as_ptr(), indices.len(), ct, ctx);
+        }
+    }
+}
+
+impl Clone for TypeTree {
+    fn clone(&self) -> Self {
+        let inner = unsafe { EnzymeNewTypeTreeTR(self.inner) };
+        TypeTree { inner }
+    }
+}
+
+impl std::fmt::Display for TypeTree {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let ptr = unsafe { EnzymeTypeTreeToString(self.inner) };
+        let cstr = unsafe { std::ffi::CStr::from_ptr(ptr) };
+        match cstr.to_str() {
+            Ok(x) => write!(f, "{}", x)?,
+            Err(err) => write!(f, "could not parse: {}", err)?,
+        }
+
+        // delete C string pointer
+        unsafe {
+            EnzymeTypeTreeToStringFree(ptr);
+        }
+
+        Ok(())
+    }
+}
+
+impl std::fmt::Debug for TypeTree {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        <Self as std::fmt::Display>::fmt(self, f)
+    }
+}
+
+impl Drop for TypeTree {
+    fn drop(&mut self) {
+        unsafe { EnzymeFreeTypeTree(self.inner) }
+    }
+}
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index 38a6a311954..e9f92267a7d 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -25,10 +25,11 @@ use rustc_target::spec::SymbolVisibility;
 use super::RustString;
 use super::debuginfo::{
     DIArray, DIBuilder, DIDerivedType, DIDescriptor, DIEnumerator, DIFile, DIFlags,
-    DIGlobalVariableExpression, DILocation, DISPFlags, DIScope, DISubprogram, DISubrange,
-    DITemplateTypeParameter, DIType, DIVariable, DebugEmissionKind, DebugNameTableKind,
+    DIGlobalVariableExpression, DILocation, DISPFlags, DIScope, DISubprogram,
+    DITemplateTypeParameter, DIType, DebugEmissionKind, DebugNameTableKind,
 };
 use crate::llvm;
+use crate::llvm::MetadataKindId;
 
 /// In the LLVM-C API, boolean values are passed as `typedef int LLVMBool`,
 /// which has a different ABI from Rust or C++ `bool`.
@@ -513,31 +514,6 @@ pub(crate) enum FileType {
     ObjectFile,
 }
 
-/// LLVMMetadataType
-#[derive(Copy, Clone)]
-#[repr(C)]
-#[expect(dead_code, reason = "Some variants are unused, but are kept to match LLVM-C")]
-pub(crate) enum MetadataType {
-    MD_dbg = 0,
-    MD_tbaa = 1,
-    MD_prof = 2,
-    MD_fpmath = 3,
-    MD_range = 4,
-    MD_tbaa_struct = 5,
-    MD_invariant_load = 6,
-    MD_alias_scope = 7,
-    MD_noalias = 8,
-    MD_nontemporal = 9,
-    MD_mem_parallel_loop_access = 10,
-    MD_nonnull = 11,
-    MD_unpredictable = 15,
-    MD_align = 17,
-    MD_type = 19,
-    MD_vcall_visibility = 28,
-    MD_noundef = 29,
-    MD_kcfi_type = 36,
-}
-
 /// Must match the layout of `LLVMInlineAsmDialect`.
 #[derive(Copy, Clone, PartialEq)]
 #[repr(C)]
@@ -807,6 +783,8 @@ unsafe extern "C" {
     pub(crate) type Metadata;
     pub(crate) type BasicBlock;
     pub(crate) type Comdat;
+    /// `&'ll DbgRecord` represents `LLVMDbgRecordRef`.
+    pub(crate) type DbgRecord;
 }
 #[repr(C)]
 pub(crate) struct Builder<'a>(InvariantOpaque<'a>);
@@ -891,7 +869,6 @@ pub(crate) mod debuginfo {
     pub(crate) type DIVariable = DIDescriptor;
     pub(crate) type DIGlobalVariableExpression = DIDescriptor;
     pub(crate) type DIArray = DIDescriptor;
-    pub(crate) type DISubrange = DIDescriptor;
     pub(crate) type DIEnumerator = DIDescriptor;
     pub(crate) type DITemplateTypeParameter = DIDescriptor;
 
@@ -1034,16 +1011,6 @@ pub(crate) type GetSymbolsCallback =
     unsafe extern "C" fn(*mut c_void, *const c_char) -> *mut c_void;
 pub(crate) type GetSymbolsErrorCallback = unsafe extern "C" fn(*const c_char) -> *mut c_void;
 
-#[derive(Copy, Clone)]
-#[repr(transparent)]
-pub(crate) struct MetadataKindId(c_uint);
-
-impl From<MetadataType> for MetadataKindId {
-    fn from(value: MetadataType) -> Self {
-        Self(value as c_uint)
-    }
-}
-
 unsafe extern "C" {
     // Create and destroy contexts.
     pub(crate) fn LLVMContextDispose(C: &'static mut Context);
@@ -1138,7 +1105,11 @@ unsafe extern "C" {
     pub(crate) fn LLVMSetValueName2(Val: &Value, Name: *const c_char, NameLen: size_t);
     pub(crate) fn LLVMReplaceAllUsesWith<'a>(OldVal: &'a Value, NewVal: &'a Value);
     pub(crate) safe fn LLVMSetMetadata<'a>(Val: &'a Value, KindID: MetadataKindId, Node: &'a Value);
-    pub(crate) fn LLVMGlobalSetMetadata<'a>(Val: &'a Value, KindID: c_uint, Metadata: &'a Metadata);
+    pub(crate) fn LLVMGlobalSetMetadata<'a>(
+        Val: &'a Value,
+        KindID: MetadataKindId,
+        Metadata: &'a Metadata,
+    );
     pub(crate) safe fn LLVMValueAsMetadata(Node: &Value) -> &Metadata;
 
     // Operations on constants of any type
@@ -1992,6 +1963,59 @@ unsafe extern "C" {
         Scope: Option<&'ll Metadata>,
         AlignInBits: u32, // (optional; default is 0)
     ) -> &'ll Metadata;
+
+    pub(crate) fn LLVMDIBuilderGetOrCreateSubrange<'ll>(
+        Builder: &DIBuilder<'ll>,
+        LowerBound: i64,
+        Count: i64,
+    ) -> &'ll Metadata;
+
+    pub(crate) fn LLVMDIBuilderGetOrCreateArray<'ll>(
+        Builder: &DIBuilder<'ll>,
+        Data: *const Option<&'ll Metadata>,
+        NumElements: size_t,
+    ) -> &'ll Metadata;
+
+    pub(crate) fn LLVMDIBuilderCreateExpression<'ll>(
+        Builder: &DIBuilder<'ll>,
+        Addr: *const u64,
+        Length: size_t,
+    ) -> &'ll Metadata;
+
+    pub(crate) fn LLVMDIBuilderInsertDeclareRecordAtEnd<'ll>(
+        Builder: &DIBuilder<'ll>,
+        Storage: &'ll Value,
+        VarInfo: &'ll Metadata,
+        Expr: &'ll Metadata,
+        DebugLoc: &'ll Metadata,
+        Block: &'ll BasicBlock,
+    ) -> &'ll DbgRecord;
+
+    pub(crate) fn LLVMDIBuilderCreateAutoVariable<'ll>(
+        Builder: &DIBuilder<'ll>,
+        Scope: &'ll Metadata,
+        Name: *const c_uchar, // See "PTR_LEN_STR".
+        NameLen: size_t,
+        File: &'ll Metadata,
+        LineNo: c_uint,
+        Ty: &'ll Metadata,
+        AlwaysPreserve: llvm::Bool, // "If true, this descriptor will survive optimizations."
+        Flags: DIFlags,
+        AlignInBits: u32,
+    ) -> &'ll Metadata;
+
+    pub(crate) fn LLVMDIBuilderCreateParameterVariable<'ll>(
+        Builder: &DIBuilder<'ll>,
+        Scope: &'ll Metadata,
+        Name: *const c_uchar, // See "PTR_LEN_STR".
+        NameLen: size_t,
+        ArgNo: c_uint,
+        File: &'ll Metadata,
+        LineNo: c_uint,
+        Ty: &'ll Metadata,
+        AlwaysPreserve: llvm::Bool, // "If true, this descriptor will survive optimizations."
+        Flags: DIFlags,
+    ) -> &'ll Metadata;
 }
 
 #[link(name = "llvm-wrapper", kind = "static")]
@@ -2005,7 +2029,7 @@ unsafe extern "C" {
     // Operations on all values
     pub(crate) fn LLVMRustGlobalAddMetadata<'a>(
         Val: &'a Value,
-        KindID: c_uint,
+        KindID: MetadataKindId,
         Metadata: &'a Metadata,
     );
     pub(crate) fn LLVMRustIsNonGVFunctionPointerTy(Val: &Value) -> bool;
@@ -2202,8 +2226,11 @@ unsafe extern "C" {
         ConstraintsLen: size_t,
     ) -> bool;
 
+    /// A list of pointer-length strings is passed as two pointer-length slices,
+    /// one slice containing pointers and one slice containing their corresponding
+    /// lengths. The implementation will check that both slices have the same length.
     pub(crate) fn LLVMRustCoverageWriteFilenamesToBuffer(
-        Filenames: *const *const c_char,
+        Filenames: *const *const c_uchar, // See "PTR_LEN_STR".
         FilenamesLen: size_t,
         Lengths: *const size_t,
         LengthsLen: size_t,
@@ -2226,18 +2253,25 @@ unsafe extern "C" {
 
     pub(crate) fn LLVMRustCoverageCreatePGOFuncNameVar(
         F: &Value,
-        FuncName: *const c_char,
+        FuncName: *const c_uchar, // See "PTR_LEN_STR".
         FuncNameLen: size_t,
     ) -> &Value;
-    pub(crate) fn LLVMRustCoverageHashBytes(Bytes: *const c_char, NumBytes: size_t) -> u64;
+    pub(crate) fn LLVMRustCoverageHashBytes(
+        Bytes: *const c_uchar, // See "PTR_LEN_STR".
+        NumBytes: size_t,
+    ) -> u64;
 
-    pub(crate) fn LLVMRustCoverageWriteCovmapSectionNameToString(M: &Module, OutStr: &RustString);
-
-    pub(crate) fn LLVMRustCoverageWriteCovfunSectionNameToString(M: &Module, OutStr: &RustString);
-
-    pub(crate) fn LLVMRustCoverageWriteCovmapVarNameToString(OutStr: &RustString);
+    pub(crate) safe fn LLVMRustCoverageWriteCovmapSectionNameToString(
+        M: &Module,
+        OutStr: &RustString,
+    );
+    pub(crate) safe fn LLVMRustCoverageWriteCovfunSectionNameToString(
+        M: &Module,
+        OutStr: &RustString,
+    );
+    pub(crate) safe fn LLVMRustCoverageWriteCovmapVarNameToString(OutStr: &RustString);
 
-    pub(crate) fn LLVMRustCoverageMappingVersion() -> u32;
+    pub(crate) safe fn LLVMRustCoverageMappingVersion() -> u32;
     pub(crate) fn LLVMRustDebugMetadataVersion() -> u32;
     pub(crate) fn LLVMRustVersionMajor() -> u32;
     pub(crate) fn LLVMRustVersionMinor() -> u32;
@@ -2358,43 +2392,6 @@ unsafe extern "C" {
         AlignInBits: u32,
     ) -> &'a DIGlobalVariableExpression;
 
-    pub(crate) fn LLVMRustDIBuilderCreateVariable<'a>(
-        Builder: &DIBuilder<'a>,
-        Tag: c_uint,
-        Scope: &'a DIDescriptor,
-        Name: *const c_char,
-        NameLen: size_t,
-        File: &'a DIFile,
-        LineNo: c_uint,
-        Ty: &'a DIType,
-        AlwaysPreserve: bool,
-        Flags: DIFlags,
-        ArgNo: c_uint,
-        AlignInBits: u32,
-    ) -> &'a DIVariable;
-
-    pub(crate) fn LLVMRustDIBuilderGetOrCreateSubrange<'a>(
-        Builder: &DIBuilder<'a>,
-        Lo: i64,
-        Count: i64,
-    ) -> &'a DISubrange;
-
-    pub(crate) fn LLVMRustDIBuilderGetOrCreateArray<'a>(
-        Builder: &DIBuilder<'a>,
-        Ptr: *const Option<&'a DIDescriptor>,
-        Count: c_uint,
-    ) -> &'a DIArray;
-
-    pub(crate) fn LLVMRustDIBuilderInsertDeclareAtEnd<'a>(
-        Builder: &DIBuilder<'a>,
-        Val: &'a Value,
-        VarInfo: &'a DIVariable,
-        AddrOps: *const u64,
-        AddrOpsCount: c_uint,
-        DL: &'a DILocation,
-        InsertAtEnd: &'a BasicBlock,
-    );
-
     pub(crate) fn LLVMRustDIBuilderCreateEnumerator<'a>(
         Builder: &DIBuilder<'a>,
         Name: *const c_char,
diff --git a/compiler/rustc_codegen_llvm/src/llvm/metadata_kind.rs b/compiler/rustc_codegen_llvm/src/llvm/metadata_kind.rs
new file mode 100644
index 00000000000..a8a671b5c85
--- /dev/null
+++ b/compiler/rustc_codegen_llvm/src/llvm/metadata_kind.rs
@@ -0,0 +1,71 @@
+use libc::c_uint;
+
+pub(crate) use self::fixed_kinds::*;
+
+#[derive(Copy, Clone)]
+#[repr(transparent)]
+pub(crate) struct MetadataKindId(c_uint);
+
+macro_rules! declare_fixed_metadata_kinds {
+    (
+        $(
+            FIXED_MD_KIND($variant:ident, $value:literal)
+        )*
+    ) => {
+        // Use a submodule to group all declarations into one `#[expect(..)]`.
+        #[expect(dead_code)]
+        mod fixed_kinds {
+            use super::MetadataKindId;
+            $(
+                #[expect(non_upper_case_globals)]
+                pub(crate) const $variant: MetadataKindId = MetadataKindId($value);
+            )*
+        }
+    };
+}
+
+// Must be kept in sync with the corresponding static assertions in `RustWrapper.cpp`.
+declare_fixed_metadata_kinds! {
+    FIXED_MD_KIND(MD_dbg, 0)
+    FIXED_MD_KIND(MD_tbaa, 1)
+    FIXED_MD_KIND(MD_prof, 2)
+    FIXED_MD_KIND(MD_fpmath, 3)
+    FIXED_MD_KIND(MD_range, 4)
+    FIXED_MD_KIND(MD_tbaa_struct, 5)
+    FIXED_MD_KIND(MD_invariant_load, 6)
+    FIXED_MD_KIND(MD_alias_scope, 7)
+    FIXED_MD_KIND(MD_noalias, 8)
+    FIXED_MD_KIND(MD_nontemporal, 9)
+    FIXED_MD_KIND(MD_mem_parallel_loop_access, 10)
+    FIXED_MD_KIND(MD_nonnull, 11)
+    FIXED_MD_KIND(MD_dereferenceable, 12)
+    FIXED_MD_KIND(MD_dereferenceable_or_null, 13)
+    FIXED_MD_KIND(MD_make_implicit, 14)
+    FIXED_MD_KIND(MD_unpredictable, 15)
+    FIXED_MD_KIND(MD_invariant_group, 16)
+    FIXED_MD_KIND(MD_align, 17)
+    FIXED_MD_KIND(MD_loop, 18)
+    FIXED_MD_KIND(MD_type, 19)
+    FIXED_MD_KIND(MD_section_prefix, 20)
+    FIXED_MD_KIND(MD_absolute_symbol, 21)
+    FIXED_MD_KIND(MD_associated, 22)
+    FIXED_MD_KIND(MD_callees, 23)
+    FIXED_MD_KIND(MD_irr_loop, 24)
+    FIXED_MD_KIND(MD_access_group, 25)
+    FIXED_MD_KIND(MD_callback, 26)
+    FIXED_MD_KIND(MD_preserve_access_index, 27)
+    FIXED_MD_KIND(MD_vcall_visibility, 28)
+    FIXED_MD_KIND(MD_noundef, 29)
+    FIXED_MD_KIND(MD_annotation, 30)
+    FIXED_MD_KIND(MD_nosanitize, 31)
+    FIXED_MD_KIND(MD_func_sanitize, 32)
+    FIXED_MD_KIND(MD_exclude, 33)
+    FIXED_MD_KIND(MD_memprof, 34)
+    FIXED_MD_KIND(MD_callsite, 35)
+    FIXED_MD_KIND(MD_kcfi_type, 36)
+    FIXED_MD_KIND(MD_pcsections, 37)
+    FIXED_MD_KIND(MD_DIAssignID, 38)
+    FIXED_MD_KIND(MD_coro_outside_frame, 39)
+    FIXED_MD_KIND(MD_mmra, 40)
+    FIXED_MD_KIND(MD_noalias_addrspace, 41)
+}
diff --git a/compiler/rustc_codegen_llvm/src/llvm/mod.rs b/compiler/rustc_codegen_llvm/src/llvm/mod.rs
index 1115d82fa85..9a53dacb1df 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/mod.rs
@@ -11,13 +11,14 @@ use rustc_llvm::RustString;
 
 pub(crate) use self::CallConv::*;
 pub(crate) use self::CodeGenOptSize::*;
-pub(crate) use self::MetadataType::*;
 pub(crate) use self::ffi::*;
+pub(crate) use self::metadata_kind::*;
 use crate::common::AsCCharPtr;
 
 pub(crate) mod diagnostic;
 pub(crate) mod enzyme_ffi;
 mod ffi;
+mod metadata_kind;
 
 pub(crate) use self::enzyme_ffi::*;
 
diff --git a/compiler/rustc_codegen_llvm/src/type_.rs b/compiler/rustc_codegen_llvm/src/type_.rs
index 9ecaf5f24fe..5b97898a4b8 100644
--- a/compiler/rustc_codegen_llvm/src/type_.rs
+++ b/compiler/rustc_codegen_llvm/src/type_.rs
@@ -306,7 +306,7 @@ impl<'ll, 'tcx> TypeMembershipCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
             let v = [llvm::LLVMValueAsMetadata(self.const_usize(0)), typeid_metadata];
             llvm::LLVMRustGlobalAddMetadata(
                 function,
-                llvm::MD_type as c_uint,
+                llvm::MD_type,
                 llvm::LLVMMDNodeInContext2(self.llcx, v.as_ptr(), v.len()),
             )
         }
@@ -318,7 +318,7 @@ impl<'ll, 'tcx> TypeMembershipCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
             let v = [llvm::LLVMValueAsMetadata(self.const_usize(0)), typeid_metadata];
             llvm::LLVMGlobalSetMetadata(
                 function,
-                llvm::MD_type as c_uint,
+                llvm::MD_type,
                 llvm::LLVMMDNodeInContext2(self.llcx, v.as_ptr(), v.len()),
             )
         }
@@ -333,7 +333,7 @@ impl<'ll, 'tcx> TypeMembershipCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
         unsafe {
             llvm::LLVMRustGlobalAddMetadata(
                 function,
-                llvm::MD_kcfi_type as c_uint,
+                llvm::MD_kcfi_type,
                 llvm::LLVMMDNodeInContext2(
                     self.llcx,
                     &llvm::LLVMValueAsMetadata(kcfi_type_metadata),
@@ -348,7 +348,7 @@ impl<'ll, 'tcx> TypeMembershipCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
         unsafe {
             llvm::LLVMGlobalSetMetadata(
                 function,
-                llvm::MD_kcfi_type as c_uint,
+                llvm::MD_kcfi_type,
                 llvm::LLVMMDNodeInContext2(
                     self.llcx,
                     &llvm::LLVMValueAsMetadata(kcfi_type_metadata),
diff --git a/compiler/rustc_codegen_llvm/src/typetree.rs b/compiler/rustc_codegen_llvm/src/typetree.rs
new file mode 100644
index 00000000000..7e263503700
--- /dev/null
+++ b/compiler/rustc_codegen_llvm/src/typetree.rs
@@ -0,0 +1,122 @@
+use rustc_ast::expand::typetree::FncTree;
+#[cfg(feature = "llvm_enzyme")]
+use {
+    crate::attributes,
+    rustc_ast::expand::typetree::TypeTree as RustTypeTree,
+    std::ffi::{CString, c_char, c_uint},
+};
+
+use crate::llvm::{self, Value};
+
+#[cfg(feature = "llvm_enzyme")]
+fn to_enzyme_typetree(
+    rust_typetree: RustTypeTree,
+    _data_layout: &str,
+    llcx: &llvm::Context,
+) -> llvm::TypeTree {
+    let mut enzyme_tt = llvm::TypeTree::new();
+    process_typetree_recursive(&mut enzyme_tt, &rust_typetree, &[], llcx);
+    enzyme_tt
+}
+#[cfg(feature = "llvm_enzyme")]
+fn process_typetree_recursive(
+    enzyme_tt: &mut llvm::TypeTree,
+    rust_typetree: &RustTypeTree,
+    parent_indices: &[i64],
+    llcx: &llvm::Context,
+) {
+    for rust_type in &rust_typetree.0 {
+        let concrete_type = match rust_type.kind {
+            rustc_ast::expand::typetree::Kind::Anything => llvm::CConcreteType::DT_Anything,
+            rustc_ast::expand::typetree::Kind::Integer => llvm::CConcreteType::DT_Integer,
+            rustc_ast::expand::typetree::Kind::Pointer => llvm::CConcreteType::DT_Pointer,
+            rustc_ast::expand::typetree::Kind::Half => llvm::CConcreteType::DT_Half,
+            rustc_ast::expand::typetree::Kind::Float => llvm::CConcreteType::DT_Float,
+            rustc_ast::expand::typetree::Kind::Double => llvm::CConcreteType::DT_Double,
+            rustc_ast::expand::typetree::Kind::F128 => llvm::CConcreteType::DT_FP128,
+            rustc_ast::expand::typetree::Kind::Unknown => llvm::CConcreteType::DT_Unknown,
+        };
+
+        let mut indices = parent_indices.to_vec();
+        if !parent_indices.is_empty() {
+            indices.push(rust_type.offset as i64);
+        } else if rust_type.offset == -1 {
+            indices.push(-1);
+        } else {
+            indices.push(rust_type.offset as i64);
+        }
+
+        enzyme_tt.insert(&indices, concrete_type, llcx);
+
+        if rust_type.kind == rustc_ast::expand::typetree::Kind::Pointer
+            && !rust_type.child.0.is_empty()
+        {
+            process_typetree_recursive(enzyme_tt, &rust_type.child, &indices, llcx);
+        }
+    }
+}
+
+#[cfg(feature = "llvm_enzyme")]
+pub(crate) fn add_tt<'ll>(
+    llmod: &'ll llvm::Module,
+    llcx: &'ll llvm::Context,
+    fn_def: &'ll Value,
+    tt: FncTree,
+) {
+    let inputs = tt.args;
+    let ret_tt: RustTypeTree = tt.ret;
+
+    let llvm_data_layout: *const c_char = unsafe { llvm::LLVMGetDataLayoutStr(&*llmod) };
+    let llvm_data_layout =
+        std::str::from_utf8(unsafe { std::ffi::CStr::from_ptr(llvm_data_layout) }.to_bytes())
+            .expect("got a non-UTF8 data-layout from LLVM");
+
+    let attr_name = "enzyme_type";
+    let c_attr_name = CString::new(attr_name).unwrap();
+
+    for (i, input) in inputs.iter().enumerate() {
+        unsafe {
+            let enzyme_tt = to_enzyme_typetree(input.clone(), llvm_data_layout, llcx);
+            let c_str = llvm::EnzymeTypeTreeToString(enzyme_tt.inner);
+            let c_str = std::ffi::CStr::from_ptr(c_str);
+
+            let attr = llvm::LLVMCreateStringAttribute(
+                llcx,
+                c_attr_name.as_ptr(),
+                c_attr_name.as_bytes().len() as c_uint,
+                c_str.as_ptr(),
+                c_str.to_bytes().len() as c_uint,
+            );
+
+            attributes::apply_to_llfn(fn_def, llvm::AttributePlace::Argument(i as u32), &[attr]);
+            llvm::EnzymeTypeTreeToStringFree(c_str.as_ptr());
+        }
+    }
+
+    unsafe {
+        let enzyme_tt = to_enzyme_typetree(ret_tt, llvm_data_layout, llcx);
+        let c_str = llvm::EnzymeTypeTreeToString(enzyme_tt.inner);
+        let c_str = std::ffi::CStr::from_ptr(c_str);
+
+        let ret_attr = llvm::LLVMCreateStringAttribute(
+            llcx,
+            c_attr_name.as_ptr(),
+            c_attr_name.as_bytes().len() as c_uint,
+            c_str.as_ptr(),
+            c_str.to_bytes().len() as c_uint,
+        );
+
+        attributes::apply_to_llfn(fn_def, llvm::AttributePlace::ReturnValue, &[ret_attr]);
+        llvm::EnzymeTypeTreeToStringFree(c_str.as_ptr());
+    }
+}
+
+#[cfg(not(feature = "llvm_enzyme"))]
+pub(crate) fn add_tt<'ll>(
+    _llmod: &'ll llvm::Module,
+    _llcx: &'ll llvm::Context,
+    _fn_def: &'ll Value,
+    _tt: FncTree,
+) {
+    unimplemented!()
+}
diff --git a/compiler/rustc_codegen_llvm/src/va_arg.rs b/compiler/rustc_codegen_llvm/src/va_arg.rs
index ab08125217f..234366e491c 100644
--- a/compiler/rustc_codegen_llvm/src/va_arg.rs
+++ b/compiler/rustc_codegen_llvm/src/va_arg.rs
@@ -193,7 +193,7 @@ fn emit_aapcs_va_arg<'ll, 'tcx>(
     // the offset again.
 
     bx.switch_to_block(maybe_reg);
-    if gr_type && layout.align.abi.bytes() > 8 {
+    if gr_type && layout.align.bytes() > 8 {
         reg_off_v = bx.add(reg_off_v, bx.const_i32(15));
         reg_off_v = bx.and(reg_off_v, bx.const_i32(-16));
     }
@@ -291,7 +291,7 @@ fn emit_powerpc_va_arg<'ll, 'tcx>(
         bx.inbounds_ptradd(va_list_addr, bx.const_usize(1)) // fpr
     };
 
-    let mut num_regs = bx.load(bx.type_i8(), num_regs_addr, dl.i8_align.abi);
+    let mut num_regs = bx.load(bx.type_i8(), num_regs_addr, dl.i8_align);
 
     // "Align" the register count when the type is passed as `i64`.
     if is_i64 || (is_f64 && is_soft_float_abi) {
@@ -329,7 +329,7 @@ fn emit_powerpc_va_arg<'ll, 'tcx>(
         // Increase the used-register count.
         let reg_incr = if is_i64 || (is_f64 && is_soft_float_abi) { 2 } else { 1 };
         let new_num_regs = bx.add(num_regs, bx.cx.const_u8(reg_incr));
-        bx.store(new_num_regs, num_regs_addr, dl.i8_align.abi);
+        bx.store(new_num_regs, num_regs_addr, dl.i8_align);
 
         bx.br(end);
 
@@ -339,7 +339,7 @@ fn emit_powerpc_va_arg<'ll, 'tcx>(
     let mem_addr = {
         bx.switch_to_block(in_mem);
 
-        bx.store(bx.const_u8(max_regs), num_regs_addr, dl.i8_align.abi);
+        bx.store(bx.const_u8(max_regs), num_regs_addr, dl.i8_align);
 
         // Everything in the overflow area is rounded up to a size of at least 4.
         let overflow_area_align = Align::from_bytes(4).unwrap();
@@ -738,6 +738,7 @@ fn copy_to_temporary_if_more_aligned<'ll, 'tcx>(
             src_align,
             bx.const_u32(layout.layout.size().bytes() as u32),
             MemFlags::empty(),
+            None,
         );
         tmp
     } else {
@@ -760,7 +761,7 @@ fn x86_64_sysv64_va_arg_from_memory<'ll, 'tcx>(
     // byte boundary if alignment needed by type exceeds 8 byte boundary.
     // It isn't stated explicitly in the standard, but in practice we use
     // alignment greater than 16 where necessary.
-    if layout.layout.align.abi.bytes() > 8 {
+    if layout.layout.align.bytes() > 8 {
         unreachable!("all instances of VaArgSafe have an alignment <= 8");
     }
 
@@ -813,7 +814,7 @@ fn emit_xtensa_va_arg<'ll, 'tcx>(
     let va_ndx_offset = va_reg_offset + 4;
     let offset_ptr = bx.inbounds_ptradd(va_list_addr, bx.cx.const_usize(va_ndx_offset));
 
-    let offset = bx.load(bx.type_i32(), offset_ptr, bx.tcx().data_layout.i32_align.abi);
+    let offset = bx.load(bx.type_i32(), offset_ptr, bx.tcx().data_layout.i32_align);
     let offset = round_up_to_alignment(bx, offset, layout.align.abi);
 
     let slot_size = layout.size.align_to(Align::from_bytes(4).unwrap()).bytes() as i32;
diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs
index d6c304c1b14..db2f2dd65b0 100644
--- a/compiler/rustc_codegen_ssa/src/back/link.rs
+++ b/compiler/rustc_codegen_ssa/src/back/link.rs
@@ -79,6 +79,7 @@ pub fn link_binary(
     codegen_results: CodegenResults,
     metadata: EncodedMetadata,
     outputs: &OutputFilenames,
+    codegen_backend: &'static str,
 ) {
     let _timer = sess.timer("link_binary");
     let output_metadata = sess.opts.output_types.contains_key(&OutputType::Metadata);
@@ -154,6 +155,7 @@ pub fn link_binary(
                         &codegen_results,
                         &metadata,
                         path.as_ref(),
+                        codegen_backend,
                     );
                 }
             }
@@ -680,6 +682,7 @@ fn link_natively(
     codegen_results: &CodegenResults,
     metadata: &EncodedMetadata,
     tmpdir: &Path,
+    codegen_backend: &'static str,
 ) {
     info!("preparing {:?} to {:?}", crate_type, out_filename);
     let (linker_path, flavor) = linker_and_flavor(sess);
@@ -705,6 +708,7 @@ fn link_natively(
         codegen_results,
         metadata,
         self_contained_components,
+        codegen_backend,
     );
 
     linker::disable_localization(&mut cmd);
@@ -2208,6 +2212,7 @@ fn linker_with_args(
     codegen_results: &CodegenResults,
     metadata: &EncodedMetadata,
     self_contained_components: LinkSelfContainedComponents,
+    codegen_backend: &'static str,
 ) -> Command {
     let self_contained_crt_objects = self_contained_components.is_crt_objects_enabled();
     let cmd = &mut *super::linker::get_linker(
@@ -2216,6 +2221,7 @@ fn linker_with_args(
         flavor,
         self_contained_components.are_any_components_enabled(),
         &codegen_results.crate_info.target_cpu,
+        codegen_backend,
     );
     let link_output_kind = link_output_kind(sess, crate_type);
 
diff --git a/compiler/rustc_codegen_ssa/src/back/linker.rs b/compiler/rustc_codegen_ssa/src/back/linker.rs
index 624ab1b5084..e644a43f883 100644
--- a/compiler/rustc_codegen_ssa/src/back/linker.rs
+++ b/compiler/rustc_codegen_ssa/src/back/linker.rs
@@ -52,6 +52,7 @@ pub(crate) fn get_linker<'a>(
     flavor: LinkerFlavor,
     self_contained: bool,
     target_cpu: &'a str,
+    codegen_backend: &'static str,
 ) -> Box<dyn Linker + 'a> {
     let msvc_tool = find_msvc_tools::find_tool(&sess.target.arch, "link.exe");
 
@@ -154,6 +155,7 @@ pub(crate) fn get_linker<'a>(
             is_ld: cc == Cc::No,
             is_gnu: flavor.is_gnu(),
             uses_lld: flavor.uses_lld(),
+            codegen_backend,
         }) as Box<dyn Linker>,
         LinkerFlavor::Msvc(..) => Box::new(MsvcLinker { cmd, sess }) as Box<dyn Linker>,
         LinkerFlavor::EmCc => Box::new(EmLinker { cmd, sess }) as Box<dyn Linker>,
@@ -367,6 +369,7 @@ struct GccLinker<'a> {
     is_ld: bool,
     is_gnu: bool,
     uses_lld: bool,
+    codegen_backend: &'static str,
 }
 
 impl<'a> GccLinker<'a> {
@@ -423,9 +426,15 @@ impl<'a> GccLinker<'a> {
         if let Some(path) = &self.sess.opts.unstable_opts.profile_sample_use {
             self.link_arg(&format!("-plugin-opt=sample-profile={}", path.display()));
         };
+        let prefix = if self.codegen_backend == "gcc" {
+            // The GCC linker plugin requires a leading dash.
+            "-"
+        } else {
+            ""
+        };
         self.link_args(&[
-            &format!("-plugin-opt={opt_level}"),
-            &format!("-plugin-opt=mcpu={}", self.target_cpu),
+            &format!("-plugin-opt={prefix}{opt_level}"),
+            &format!("-plugin-opt={prefix}mcpu={}", self.target_cpu),
         ]);
     }
 
diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs
index 68a2f43ec67..422b06350e1 100644
--- a/compiler/rustc_codegen_ssa/src/base.rs
+++ b/compiler/rustc_codegen_ssa/src/base.rs
@@ -11,12 +11,12 @@ use rustc_data_structures::fx::{FxHashMap, FxIndexSet};
 use rustc_data_structures::profiling::{get_resident_set_size, print_time_passes_entry};
 use rustc_data_structures::sync::{IntoDynSyncSend, par_map};
 use rustc_data_structures::unord::UnordMap;
-use rustc_hir::attrs::OptimizeAttr;
+use rustc_hir::attrs::{DebuggerVisualizerType, OptimizeAttr};
 use rustc_hir::def_id::{DefId, LOCAL_CRATE};
 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::debugger_visualizer::DebuggerVisualizerFile;
 use rustc_middle::middle::dependency_format::Dependencies;
 use rustc_middle::middle::exported_symbols::{self, SymbolExportKind};
 use rustc_middle::middle::lang_items;
diff --git a/compiler/rustc_codegen_ssa/src/mir/block.rs b/compiler/rustc_codegen_ssa/src/mir/block.rs
index 1b218a0d339..b2dc4fe32b0 100644
--- a/compiler/rustc_codegen_ssa/src/mir/block.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/block.rs
@@ -1626,6 +1626,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     align,
                     bx.const_usize(copy_bytes),
                     MemFlags::empty(),
+                    None,
                 );
                 // ...and then load it with the ABI type.
                 llval = load_cast(bx, cast, llscratch, scratch_align);
diff --git a/compiler/rustc_codegen_ssa/src/mir/intrinsic.rs b/compiler/rustc_codegen_ssa/src/mir/intrinsic.rs
index 3c667b8e882..befa00c6861 100644
--- a/compiler/rustc_codegen_ssa/src/mir/intrinsic.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/intrinsic.rs
@@ -30,7 +30,7 @@ fn copy_intrinsic<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     if allow_overlap {
         bx.memmove(dst, align, src, align, size, flags);
     } else {
-        bx.memcpy(dst, align, src, align, size, flags);
+        bx.memcpy(dst, align, src, align, size, flags, None);
     }
 }
 
diff --git a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
index 69478d078cc..d629003bff5 100644
--- a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
@@ -621,7 +621,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     }
                     mir::NullOp::AlignOf => {
                         assert!(bx.cx().type_is_sized(ty));
-                        let val = layout.align.abi.bytes();
+                        let val = layout.align.bytes();
                         bx.cx().const_usize(val)
                     }
                     mir::NullOp::OffsetOf(fields) => {
diff --git a/compiler/rustc_codegen_ssa/src/mir/statement.rs b/compiler/rustc_codegen_ssa/src/mir/statement.rs
index f164e0f9123..0a50d7f18db 100644
--- a/compiler/rustc_codegen_ssa/src/mir/statement.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/statement.rs
@@ -90,7 +90,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 let align = pointee_layout.align;
                 let dst = dst_val.immediate();
                 let src = src_val.immediate();
-                bx.memcpy(dst, align, src, align, bytes, crate::MemFlags::empty());
+                bx.memcpy(dst, align, src, align, bytes, crate::MemFlags::empty(), None);
             }
             mir::StatementKind::FakeRead(..)
             | mir::StatementKind::Retag { .. }
diff --git a/compiler/rustc_codegen_ssa/src/size_of_val.rs b/compiler/rustc_codegen_ssa/src/size_of_val.rs
index 577012151e4..e1bd8014d7a 100644
--- a/compiler/rustc_codegen_ssa/src/size_of_val.rs
+++ b/compiler/rustc_codegen_ssa/src/size_of_val.rs
@@ -21,7 +21,7 @@ pub fn size_and_align_of_dst<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     trace!("size_and_align_of_dst(ty={}, info={:?}): layout: {:?}", t, info, layout);
     if layout.is_sized() {
         let size = bx.const_usize(layout.size.bytes());
-        let align = bx.const_usize(layout.align.abi.bytes());
+        let align = bx.const_usize(layout.align.bytes());
         return (size, align);
     }
     match t.kind() {
@@ -49,7 +49,7 @@ pub fn size_and_align_of_dst<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
                 // All slice sizes must fit into `isize`, so this multiplication cannot
                 // wrap -- neither signed nor unsigned.
                 bx.unchecked_sumul(info.unwrap(), bx.const_usize(unit.size.bytes())),
-                bx.const_usize(unit.align.abi.bytes()),
+                bx.const_usize(unit.align.bytes()),
             )
         }
         ty::Foreign(_) => {
@@ -82,7 +82,7 @@ pub fn size_and_align_of_dst<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
 
             // This function does not return so we can now return whatever we want.
             let size = bx.const_usize(layout.size.bytes());
-            let align = bx.const_usize(layout.align.abi.bytes());
+            let align = bx.const_usize(layout.align.bytes());
             (size, align)
         }
         ty::Adt(..) | ty::Tuple(..) => {
@@ -94,7 +94,7 @@ pub fn size_and_align_of_dst<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
 
             let i = layout.fields.count() - 1;
             let unsized_offset_unadjusted = layout.fields.offset(i).bytes();
-            let sized_align = layout.align.abi.bytes();
+            let sized_align = layout.align.bytes();
             debug!(
                 "DST {} offset of dyn field: {}, statically sized align: {}",
                 t, unsized_offset_unadjusted, sized_align
diff --git a/compiler/rustc_codegen_ssa/src/traits/backend.rs b/compiler/rustc_codegen_ssa/src/traits/backend.rs
index 29ec7eb1da3..2400160075e 100644
--- a/compiler/rustc_codegen_ssa/src/traits/backend.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/backend.rs
@@ -41,6 +41,8 @@ pub trait CodegenBackend {
     /// Called before `init` so that all other functions are able to emit translatable diagnostics.
     fn locale_resource(&self) -> &'static str;
 
+    fn name(&self) -> &'static str;
+
     fn init(&self, _sess: &Session) {}
 
     fn print(&self, _req: &PrintRequest, _out: &mut String, _sess: &Session) {}
@@ -96,7 +98,14 @@ pub trait CodegenBackend {
         metadata: EncodedMetadata,
         outputs: &OutputFilenames,
     ) {
-        link_binary(sess, &ArArchiveBuilderBuilder, codegen_results, metadata, outputs);
+        link_binary(
+            sess,
+            &ArArchiveBuilderBuilder,
+            codegen_results,
+            metadata,
+            outputs,
+            self.name(),
+        );
     }
 }
 
diff --git a/compiler/rustc_codegen_ssa/src/traits/builder.rs b/compiler/rustc_codegen_ssa/src/traits/builder.rs
index 4a5694e97fa..60296e36e0c 100644
--- a/compiler/rustc_codegen_ssa/src/traits/builder.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/builder.rs
@@ -451,6 +451,7 @@ pub trait BuilderMethods<'a, 'tcx>:
         src_align: Align,
         size: Self::Value,
         flags: MemFlags,
+        tt: Option<rustc_ast::expand::typetree::FncTree>,
     );
     fn memmove(
         &mut self,
@@ -507,7 +508,7 @@ pub trait BuilderMethods<'a, 'tcx>:
             temp.val.store_with_flags(self, dst.with_type(layout), flags);
         } else if !layout.is_zst() {
             let bytes = self.const_usize(layout.size.bytes());
-            self.memcpy(dst.llval, dst.align, src.llval, src.align, bytes, flags);
+            self.memcpy(dst.llval, dst.align, src.llval, src.align, bytes, flags, None);
         }
     }
 
diff --git a/compiler/rustc_const_eval/src/interpret/operator.rs b/compiler/rustc_const_eval/src/interpret/operator.rs
index 74f8a0a7b09..f0819423aa0 100644
--- a/compiler/rustc_const_eval/src/interpret/operator.rs
+++ b/compiler/rustc_const_eval/src/interpret/operator.rs
@@ -528,7 +528,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 if !layout.is_sized() {
                     span_bug!(self.cur_span(), "unsized type for `NullaryOp::AlignOf`");
                 }
-                let val = layout.align.abi.bytes();
+                let val = layout.align.bytes();
                 ImmTy::from_uint(val, usize_layout())
             }
             OffsetOf(fields) => {
diff --git a/compiler/rustc_const_eval/src/lib.rs b/compiler/rustc_const_eval/src/lib.rs
index 8ace560d85d..9c0ec4e51a0 100644
--- a/compiler/rustc_const_eval/src/lib.rs
+++ b/compiler/rustc_const_eval/src/lib.rs
@@ -1,7 +1,6 @@
 // tidy-alphabetical-start
 #![allow(internal_features)]
 #![allow(rustc::diagnostic_outside_of_impl)]
-#![cfg_attr(bootstrap, feature(strict_overflow_ops))]
 #![doc(rust_logo)]
 #![feature(array_try_map)]
 #![feature(assert_matches)]
diff --git a/compiler/rustc_const_eval/src/util/alignment.rs b/compiler/rustc_const_eval/src/util/alignment.rs
index 9507b24f603..9aafc7efd8a 100644
--- a/compiler/rustc_const_eval/src/util/alignment.rs
+++ b/compiler/rustc_const_eval/src/util/alignment.rs
@@ -37,7 +37,7 @@ where
             debug!(
                 "is_disaligned({:?}) - align = {}, packed = {}; not disaligned",
                 place,
-                layout.align.abi.bytes(),
+                layout.align.bytes(),
                 pack.bytes()
             );
             false
diff --git a/compiler/rustc_const_eval/src/util/caller_location.rs b/compiler/rustc_const_eval/src/util/caller_location.rs
index 5249b32eca4..4e7c8310007 100644
--- a/compiler/rustc_const_eval/src/util/caller_location.rs
+++ b/compiler/rustc_const_eval/src/util/caller_location.rs
@@ -61,7 +61,7 @@ pub(crate) fn const_caller_location_provider(
     trace!("const_caller_location: {}:{}:{}", file, line, col);
     let mut ecx = mk_eval_cx_to_read_const_val(
         tcx,
-        rustc_span::DUMMY_SP, // FIXME: use a proper span here?
+        rustc_span::DUMMY_SP, // This interpreter cannot fail, so the span is irrelevant.
         ty::TypingEnv::fully_monomorphized(),
         CanAccessMutGlobal::No,
     );
diff --git a/compiler/rustc_const_eval/src/util/check_validity_requirement.rs b/compiler/rustc_const_eval/src/util/check_validity_requirement.rs
index b1f29598750..1dea7e4252d 100644
--- a/compiler/rustc_const_eval/src/util/check_validity_requirement.rs
+++ b/compiler/rustc_const_eval/src/util/check_validity_requirement.rs
@@ -129,7 +129,7 @@ fn check_validity_requirement_lax<'tcx>(
     if let Some(pointee) = this.ty.builtin_deref(false) {
         let pointee = cx.layout_of(pointee)?;
         // We need to ensure that the LLVM attributes `aligned` and `dereferenceable(size)` are satisfied.
-        if pointee.align.abi.bytes() > 1 {
+        if pointee.align.bytes() > 1 {
             // 0x01-filling is not aligned.
             return Ok(false);
         }
diff --git a/compiler/rustc_error_codes/src/error_codes/E0719.md b/compiler/rustc_error_codes/src/error_codes/E0719.md
index cd981db1058..6aec38b42a3 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0719.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0719.md
@@ -1,4 +1,4 @@
-An associated type value was specified more than once.
+An associated item was specified more than once in a trait object.
 
 Erroneous code example:
 
@@ -7,21 +7,15 @@ trait FooTrait {}
 trait BarTrait {}
 
 // error: associated type `Item` in trait `Iterator` is specified twice
-struct Foo<T: Iterator<Item: FooTrait, Item: BarTrait>> { f: T }
+type Foo = dyn Iterator<Item = u32, Item = u32>;
 ```
 
-`Item` in trait `Iterator` cannot be specified multiple times for struct `Foo`.
-To fix this, create a new trait that is a combination of the desired traits and
-specify the associated type with the new trait.
+To fix this, remove the duplicate specifier:
 
 Corrected example:
 
 ```
-trait FooTrait {}
-trait BarTrait {}
-trait FooBarTrait: FooTrait + BarTrait {}
-
-struct Foo<T: Iterator<Item: FooBarTrait>> { f: T } // ok!
+type Foo = dyn Iterator<Item = u32>; // ok!
 ```
 
 For more information about associated types, see [the book][bk-at]. For more
diff --git a/compiler/rustc_expand/src/base.rs b/compiler/rustc_expand/src/base.rs
index 3956125bace..33b712e3aed 100644
--- a/compiler/rustc_expand/src/base.rs
+++ b/compiler/rustc_expand/src/base.rs
@@ -324,16 +324,16 @@ pub trait BangProcMacro {
 
 impl<F> BangProcMacro for F
 where
-    F: Fn(TokenStream) -> TokenStream,
+    F: Fn(&mut ExtCtxt<'_>, Span, TokenStream) -> Result<TokenStream, ErrorGuaranteed>,
 {
     fn expand<'cx>(
         &self,
-        _ecx: &'cx mut ExtCtxt<'_>,
-        _span: Span,
+        ecx: &'cx mut ExtCtxt<'_>,
+        span: Span,
         ts: TokenStream,
     ) -> Result<TokenStream, ErrorGuaranteed> {
         // FIXME setup implicit context in TLS before calling self.
-        Ok(self(ts))
+        self(ecx, span, ts)
     }
 }
 
@@ -999,17 +999,14 @@ impl SyntaxExtension {
 
     /// A dummy bang macro `foo!()`.
     pub fn dummy_bang(edition: Edition) -> SyntaxExtension {
-        fn expander<'cx>(
-            cx: &'cx mut ExtCtxt<'_>,
+        fn expand(
+            ecx: &mut ExtCtxt<'_>,
             span: Span,
-            _: TokenStream,
-        ) -> MacroExpanderResult<'cx> {
-            ExpandResult::Ready(DummyResult::any(
-                span,
-                cx.dcx().span_delayed_bug(span, "expanded a dummy bang macro"),
-            ))
+            _ts: TokenStream,
+        ) -> Result<TokenStream, ErrorGuaranteed> {
+            Err(ecx.dcx().span_delayed_bug(span, "expanded a dummy bang macro"))
         }
-        SyntaxExtension::default(SyntaxExtensionKind::LegacyBang(Arc::new(expander)), edition)
+        SyntaxExtension::default(SyntaxExtensionKind::Bang(Arc::new(expand)), edition)
     }
 
     /// A dummy derive macro `#[derive(Foo)]`.
diff --git a/compiler/rustc_expand/src/expand.rs b/compiler/rustc_expand/src/expand.rs
index 4c0e0bbfe26..172bc3d1d9f 100644
--- a/compiler/rustc_expand/src/expand.rs
+++ b/compiler/rustc_expand/src/expand.rs
@@ -971,7 +971,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                             });
                         }
                     },
-                    SyntaxExtensionKind::LegacyBang(..) => {
+                    SyntaxExtensionKind::Bang(..) => {
                         let msg = "expanded a dummy glob delegation";
                         let guar = self.cx.dcx().span_delayed_bug(span, msg);
                         return ExpandResult::Ready(fragment_kind.dummy(span, guar));
diff --git a/compiler/rustc_expand/src/mbe/macro_check.rs b/compiler/rustc_expand/src/mbe/macro_check.rs
index ebd6e887f7d..0eae44a05e7 100644
--- a/compiler/rustc_expand/src/mbe/macro_check.rs
+++ b/compiler/rustc_expand/src/mbe/macro_check.rs
@@ -210,8 +210,7 @@ pub(super) fn check_meta_variables(
     guar.map_or(Ok(()), Err)
 }
 
-/// Checks `lhs` as part of the LHS of a macro definition, extends `binders` with new binders, and
-/// sets `valid` to false in case of errors.
+/// Checks `lhs` as part of the LHS of a macro definition.
 ///
 /// Arguments:
 /// - `psess` is used to emit diagnostics and lints
@@ -306,8 +305,7 @@ fn get_binder_info<'a>(
     binders.get(&name).or_else(|| macros.find_map(|state| state.binders.get(&name)))
 }
 
-/// Checks `rhs` as part of the RHS of a macro definition and sets `valid` to false in case of
-/// errors.
+/// Checks `rhs` as part of the RHS of a macro definition.
 ///
 /// Arguments:
 /// - `psess` is used to emit diagnostics and lints
@@ -372,7 +370,7 @@ enum NestedMacroState {
 }
 
 /// Checks `tts` as part of the RHS of a macro definition, tries to recognize nested macro
-/// definitions, and sets `valid` to false in case of errors.
+/// definitions.
 ///
 /// Arguments:
 /// - `psess` is used to emit diagnostics and lints
@@ -491,8 +489,7 @@ fn check_nested_occurrences(
     }
 }
 
-/// Checks the body of nested macro, returns where the check stopped, and sets `valid` to false in
-/// case of errors.
+/// Checks the body of nested macro, returns where the check stopped.
 ///
 /// The token trees are checked as long as they look like a list of (LHS) => {RHS} token trees. This
 /// check is a best-effort to detect a macro definition. It returns the position in `tts` where we
diff --git a/compiler/rustc_expand/src/mbe/macro_rules.rs b/compiler/rustc_expand/src/mbe/macro_rules.rs
index 1d147a0385c..d4504ba720e 100644
--- a/compiler/rustc_expand/src/mbe/macro_rules.rs
+++ b/compiler/rustc_expand/src/mbe/macro_rules.rs
@@ -33,8 +33,8 @@ use super::diagnostics::{FailedMacro, failed_to_match_macro};
 use super::macro_parser::{NamedMatches, NamedParseResult};
 use super::{SequenceRepetition, diagnostics};
 use crate::base::{
-    AttrProcMacro, DummyResult, ExpandResult, ExtCtxt, MacResult, MacroExpanderResult,
-    SyntaxExtension, SyntaxExtensionKind, TTMacroExpander,
+    AttrProcMacro, BangProcMacro, DummyResult, ExpandResult, ExtCtxt, MacResult,
+    MacroExpanderResult, SyntaxExtension, SyntaxExtensionKind, TTMacroExpander,
 };
 use crate::errors;
 use crate::expand::{AstFragment, AstFragmentKind, ensure_complete_parse, parse_ast_fragment};
@@ -267,16 +267,16 @@ impl AttrProcMacro for MacroRulesMacroExpander {
     }
 }
 
-struct DummyExpander(ErrorGuaranteed);
+struct DummyBang(ErrorGuaranteed);
 
-impl TTMacroExpander for DummyExpander {
+impl BangProcMacro for DummyBang {
     fn expand<'cx>(
         &self,
         _: &'cx mut ExtCtxt<'_>,
-        span: Span,
+        _: Span,
         _: TokenStream,
-    ) -> ExpandResult<Box<dyn MacResult + 'cx>, ()> {
-        ExpandResult::Ready(DummyResult::any(span, self.0))
+    ) -> Result<TokenStream, ErrorGuaranteed> {
+        Err(self.0)
     }
 }
 
@@ -664,7 +664,7 @@ pub fn compile_declarative_macro(
         SyntaxExtension::new(sess, kind, span, Vec::new(), edition, ident.name, attrs, is_local)
     };
     let dummy_syn_ext =
-        |guar| (mk_syn_ext(SyntaxExtensionKind::LegacyBang(Arc::new(DummyExpander(guar)))), 0);
+        |guar| (mk_syn_ext(SyntaxExtensionKind::Bang(Arc::new(DummyBang(guar)))), 0);
 
     let macro_rules = macro_def.macro_rules;
     let exp_sep = if macro_rules { exp!(Semi) } else { exp!(Comma) };
@@ -894,12 +894,12 @@ fn check_redundant_vis_repetition(
     seq: &SequenceRepetition,
     span: &DelimSpan,
 ) {
-    let is_zero_or_one: bool = seq.kleene.op == KleeneOp::ZeroOrOne;
-    let is_vis = seq.tts.first().map_or(false, |tt| {
-        matches!(tt, mbe::TokenTree::MetaVarDecl { kind: NonterminalKind::Vis, .. })
-    });
-
-    if is_vis && is_zero_or_one {
+    if seq.kleene.op == KleeneOp::ZeroOrOne
+        && matches!(
+            seq.tts.first(),
+            Some(mbe::TokenTree::MetaVarDecl { kind: NonterminalKind::Vis, .. })
+        )
+    {
         err.note("a `vis` fragment can already be empty");
         err.multipart_suggestion(
             "remove the `$(` and `)?`",
diff --git a/compiler/rustc_feature/src/accepted.rs b/compiler/rustc_feature/src/accepted.rs
index 6af4cfb0e56..364a1202b05 100644
--- a/compiler/rustc_feature/src/accepted.rs
+++ b/compiler/rustc_feature/src/accepted.rs
@@ -205,7 +205,7 @@ declare_features! (
     (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)),
+    (accepted, extended_varargs_abi_support, "1.91.0", 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.
@@ -400,7 +400,7 @@ declare_features! (
     /// Allows use of `&foo[a..b]` as a slicing syntax.
     (accepted, slicing_syntax, "1.0.0", None),
     /// Allows use of `sse4a` target feature.
-    (accepted, sse4a_target_feature, "CURRENT_RUSTC_VERSION", Some(44839)),
+    (accepted, sse4a_target_feature, "1.91.0", Some(44839)),
     /// Allows elision of `'static` lifetimes in `static`s and `const`s.
     (accepted, static_in_const, "1.17.0", Some(35897)),
     /// Allows the definition recursive static items.
@@ -414,7 +414,7 @@ declare_features! (
     /// Allows the use of `#[target_feature]` on safe functions.
     (accepted, target_feature_11, "1.86.0", Some(69098)),
     /// Allows use of `tbm` target feature.
-    (accepted, tbm_target_feature, "CURRENT_RUSTC_VERSION", Some(44839)),
+    (accepted, tbm_target_feature, "1.91.0", Some(44839)),
     /// Allows `fn main()` with return types which implements `Termination` (RFC 1937).
     (accepted, termination_trait, "1.26.0", Some(43301)),
     /// Allows `#[test]` functions where the return type implements `Termination` (RFC 1937).
diff --git a/compiler/rustc_feature/src/removed.rs b/compiler/rustc_feature/src/removed.rs
index e37fc6b7bfc..539d67e0b6b 100644
--- a/compiler/rustc_feature/src/removed.rs
+++ b/compiler/rustc_feature/src/removed.rs
@@ -101,6 +101,10 @@ declare_features! (
      Some("never properly implemented; requires significant design work"), 127655),
     /// Allows deriving traits as per `SmartPointer` specification
     (removed, derive_smart_pointer, "1.84.0", Some(123430), Some("replaced by `CoercePointee`"), 131284),
+    /// Tells rustdoc to automatically generate `#[doc(cfg(...))]`.
+    (removed, doc_auto_cfg, "CURRENT_RUSTC_VERSION", Some(43781), Some("merged into `doc_cfg`"), 138907),
+    /// Allows `#[doc(cfg_hide(...))]`.
+    (removed, doc_cfg_hide, "CURRENT_RUSTC_VERSION", Some(43781), Some("merged into `doc_cfg`"), 138907),
     /// Allows using `#[doc(keyword = "...")]`.
     (removed, doc_keyword, "1.58.0", Some(51315),
      Some("merged into `#![feature(rustdoc_internals)]`"), 90420),
@@ -192,7 +196,7 @@ declare_features! (
     (removed, no_debug, "1.43.0", Some(29721), Some("removed due to lack of demand"), 69667),
     // Allows the use of `no_sanitize` attribute.
     /// The feature was renamed to `sanitize` and the attribute to `#[sanitize(xyz = "on|off")]`
-    (removed, no_sanitize, "CURRENT_RUSTC_VERSION", Some(39699), Some(r#"renamed to sanitize(xyz = "on|off")"#), 142681),
+    (removed, no_sanitize, "1.91.0", Some(39699), Some(r#"renamed to sanitize(xyz = "on|off")"#), 142681),
     /// Note: this feature was previously recorded in a separate
     /// `STABLE_REMOVED` list because it, uniquely, was once stable but was
     /// then removed. But there was no utility storing it separately, so now
@@ -203,7 +207,7 @@ declare_features! (
     (removed, object_safe_for_dispatch, "1.83.0", Some(43561),
      Some("renamed to `dyn_compatible_for_dispatch`"), 131511),
     /// Allows using `#[omit_gdb_pretty_printer_section]`.
-    (removed, omit_gdb_pretty_printer_section, "CURRENT_RUSTC_VERSION", None, None, 144738),
+    (removed, omit_gdb_pretty_printer_section, "1.91.0", None, None, 144738),
     /// Allows using `#[on_unimplemented(..)]` on traits.
     /// (Moved to `rustc_attrs`.)
     (removed, on_unimplemented, "1.40.0", None, None, 65794),
diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs
index 93e5588146e..e63f29a9570 100644
--- a/compiler/rustc_feature/src/unstable.rs
+++ b/compiler/rustc_feature/src/unstable.rs
@@ -327,7 +327,7 @@ declare_features! (
     (unstable, m68k_target_feature, "1.85.0", Some(134328)),
     (unstable, mips_target_feature, "1.27.0", Some(44839)),
     (unstable, movrs_target_feature, "1.88.0", Some(137976)),
-    (unstable, nvptx_target_feature, "CURRENT_RUSTC_VERSION", Some(44839)),
+    (unstable, nvptx_target_feature, "1.91.0", Some(44839)),
     (unstable, powerpc_target_feature, "1.27.0", Some(44839)),
     (unstable, prfchw_target_feature, "1.78.0", Some(44839)),
     (unstable, riscv_target_feature, "1.45.0", Some(44839)),
@@ -471,17 +471,13 @@ declare_features! (
     /// Allows deref patterns.
     (incomplete, deref_patterns, "1.79.0", Some(87121)),
     /// Allows deriving the From trait on single-field structs.
-    (unstable, derive_from, "CURRENT_RUSTC_VERSION", Some(144889)),
-    /// Tells rustdoc to automatically generate `#[doc(cfg(...))]`.
-    (unstable, doc_auto_cfg, "1.58.0", Some(43781)),
+    (unstable, derive_from, "1.91.0", Some(144889)),
     /// Allows `#[doc(cfg(...))]`.
     (unstable, doc_cfg, "1.21.0", Some(43781)),
-    /// Allows `#[doc(cfg_hide(...))]`.
-    (unstable, doc_cfg_hide, "1.57.0", Some(43781)),
     /// Allows `#[doc(masked)]`.
     (unstable, doc_masked, "1.21.0", Some(44027)),
     /// Allows features to allow target_feature to better interact with traits.
-    (incomplete, effective_target_features, "CURRENT_RUSTC_VERSION", Some(143352)),
+    (incomplete, effective_target_features, "1.91.0", Some(143352)),
     /// Allows the .use postfix syntax `x.use` and use closures `use |x| { ... }`
     (incomplete, ergonomic_clones, "1.87.0", Some(132290)),
     /// Allows exhaustive pattern matching on types that contain uninhabited types.
@@ -554,9 +550,9 @@ declare_features! (
     /// Allows fused `loop`/`match` for direct intraprocedural jumps.
     (incomplete, loop_match, "1.90.0", Some(132306)),
     /// Allow `macro_rules!` attribute rules
-    (unstable, macro_attr, "CURRENT_RUSTC_VERSION", Some(83527)),
+    (unstable, macro_attr, "1.91.0", Some(143547)),
     /// Allow `macro_rules!` derive rules
-    (unstable, macro_derive, "CURRENT_RUSTC_VERSION", Some(143549)),
+    (unstable, macro_derive, "1.91.0", Some(143549)),
     /// Give access to additional metadata about declarative macro meta-variables.
     (unstable, macro_metavar_expr, "1.61.0", Some(83527)),
     /// Provides a way to concatenate identifiers using metavariable expressions.
@@ -613,7 +609,7 @@ declare_features! (
     (unstable, proc_macro_hygiene, "1.30.0", Some(54727)),
     /// Allows the use of raw-dylibs on ELF platforms
     (incomplete, raw_dylib_elf, "1.87.0", Some(135694)),
-    (unstable, reborrow, "CURRENT_RUSTC_VERSION", Some(145612)),
+    (unstable, reborrow, "1.91.0", Some(145612)),
     /// Makes `&` and `&mut` patterns eat only one layer of references in Rust 2024.
     (incomplete, ref_pat_eat_one_layer_2024, "1.79.0", Some(123076)),
     /// Makes `&` and `&mut` patterns eat only one layer of references in Rust 2024—structural variant
@@ -627,13 +623,13 @@ declare_features! (
     /// Allows `extern "rust-cold"`.
     (unstable, rust_cold_cc, "1.63.0", Some(97544)),
     /// Allows the use of the `sanitize` attribute.
-    (unstable, sanitize, "CURRENT_RUSTC_VERSION", Some(39699)),
+    (unstable, sanitize, "1.91.0", Some(39699)),
     /// Allows the use of SIMD types in functions declared in `extern` blocks.
     (unstable, simd_ffi, "1.0.0", Some(27731)),
     /// Allows specialization of implementations (RFC 1210).
     (incomplete, specialization, "1.7.0", Some(31844)),
     /// Allows using `#[rustc_align_static(...)]` on static items.
-    (unstable, static_align, "CURRENT_RUSTC_VERSION", Some(146177)),
+    (unstable, static_align, "1.91.0", Some(146177)),
     /// Allows attributes on expressions and non-item statements.
     (unstable, stmt_expr_attributes, "1.6.0", Some(15701)),
     /// Allows lints part of the strict provenance effort.
@@ -645,7 +641,7 @@ declare_features! (
     /// 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)),
+    (unstable, target_feature_inline_always, "1.91.0", 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_hir/src/attrs/data_structures.rs b/compiler/rustc_hir/src/attrs/data_structures.rs
index 5481c9debc1..ddcbaeaad88 100644
--- a/compiler/rustc_hir/src/attrs/data_structures.rs
+++ b/compiler/rustc_hir/src/attrs/data_structures.rs
@@ -363,6 +363,20 @@ pub struct LinkEntry {
     pub import_name_type: Option<(PeImportNameType, Span)>,
 }
 
+#[derive(HashStable_Generic, PrintAttribute)]
+#[derive(Copy, PartialEq, PartialOrd, Clone, Ord, Eq, Hash, Debug, Encodable, Decodable)]
+pub enum DebuggerVisualizerType {
+    Natvis,
+    GdbPrettyPrinter,
+}
+
+#[derive(Debug, Encodable, Decodable, Clone, HashStable_Generic, PrintAttribute)]
+pub struct DebugVisualizer {
+    pub span: Span,
+    pub visualizer_type: DebuggerVisualizerType,
+    pub path: Symbol,
+}
+
 /// Represents parsed *built-in* inert attributes.
 ///
 /// ## Overview
@@ -485,7 +499,10 @@ pub enum AttributeKind {
     /// Represents `#[custom_mir]`.
     CustomMir(Option<(MirDialect, Span)>, Option<(MirPhase, Span)>, Span),
 
-    ///Represents `#[rustc_deny_explicit_impl]`.
+    /// Represents `#[debugger_visualizer]`.
+    DebuggerVisualizer(ThinVec<DebugVisualizer>),
+
+    /// Represents `#[rustc_deny_explicit_impl]`.
     DenyExplicitImpl(Span),
 
     /// Represents [`#[deprecated]`](https://doc.rust-lang.org/stable/reference/attributes/diagnostics.html#the-deprecated-attribute).
diff --git a/compiler/rustc_hir/src/attrs/encode_cross_crate.rs b/compiler/rustc_hir/src/attrs/encode_cross_crate.rs
index e0a37f50f45..1611b865c77 100644
--- a/compiler/rustc_hir/src/attrs/encode_cross_crate.rs
+++ b/compiler/rustc_hir/src/attrs/encode_cross_crate.rs
@@ -37,6 +37,7 @@ impl AttributeKind {
             Coverage(..) => No,
             CrateName { .. } => No,
             CustomMir(_, _, _) => Yes,
+            DebuggerVisualizer(..) => No,
             DenyExplicitImpl(..) => No,
             Deprecation { .. } => Yes,
             DoNotImplementViaObject(..) => No,
diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs
index 493236718a8..bc1c47e95c3 100644
--- a/compiler/rustc_hir/src/hir.rs
+++ b/compiler/rustc_hir/src/hir.rs
@@ -1298,10 +1298,7 @@ impl AttributeExt for Attribute {
     #[inline]
     fn path_matches(&self, name: &[Symbol]) -> bool {
         match &self {
-            Attribute::Unparsed(n) => {
-                n.path.segments.len() == name.len()
-                    && n.path.segments.iter().zip(name).all(|(s, n)| s.name == *n)
-            }
+            Attribute::Unparsed(n) => n.path.segments.iter().map(|ident| &ident.name).eq(name),
             _ => false,
         }
     }
diff --git a/compiler/rustc_hir/src/lang_items.rs b/compiler/rustc_hir/src/lang_items.rs
index 2e099a97b65..311cf8f995c 100644
--- a/compiler/rustc_hir/src/lang_items.rs
+++ b/compiler/rustc_hir/src/lang_items.rs
@@ -440,6 +440,7 @@ language_item_table! {
 
     // Reborrowing related lang-items
     Reborrow,                sym::reborrow,            reborrow,                   Target::Trait,          GenericRequirement::Exact(0);
+    CoerceShared,            sym::coerce_shared,       coerce_shared,              Target::Trait,          GenericRequirement::Exact(0);
 }
 
 /// The requirement imposed on the generics of a lang item
diff --git a/compiler/rustc_hir/src/lints.rs b/compiler/rustc_hir/src/lints.rs
index b7a0a6a0c19..c9de6f6b5d5 100644
--- a/compiler/rustc_hir/src/lints.rs
+++ b/compiler/rustc_hir/src/lints.rs
@@ -31,6 +31,12 @@ pub struct AttributeLint<Id> {
 
 #[derive(Clone, Debug, HashStable_Generic)]
 pub enum AttributeLintKind {
+    /// Copy of `IllFormedAttributeInput`
+    /// specifically for the `invalid_macro_export_arguments` lint until that is removed,
+    /// see <https://github.com/rust-lang/rust/pull/143857#issuecomment-3079175663>
+    InvalidMacroExportArguments {
+        suggestions: Vec<String>,
+    },
     UnusedDuplicate {
         this: Span,
         other: Span,
@@ -41,13 +47,8 @@ pub enum AttributeLintKind {
     },
     EmptyAttribute {
         first_span: Span,
-    },
-
-    /// Copy of `IllFormedAttributeInput`
-    /// specifically for the `invalid_macro_export_arguments` lint until that is removed,
-    /// see <https://github.com/rust-lang/rust/pull/143857#issuecomment-3079175663>
-    InvalidMacroExportArguments {
-        suggestions: Vec<String>,
+        attr_path: AttrPath,
+        valid_without_list: bool,
     },
     InvalidTarget {
         name: AttrPath,
diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index 886ebddc75c..e1e6860e430 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -219,7 +219,7 @@ fn check_opaque(tcx: TyCtxt<'_>, def_id: LocalDefId) {
 
     // HACK(jynelson): trying to infer the type of `impl trait` breaks documenting
     // `async-std` (and `pub async fn` in general).
-    // Since rustdoc doesn't care about the concrete type behind `impl Trait`, just don't look at it!
+    // Since rustdoc doesn't care about the hidden type behind `impl Trait`, just don't look at it!
     // See https://github.com/rust-lang/rust/issues/75100
     if tcx.sess.opts.actually_rustdoc {
         return;
@@ -252,7 +252,7 @@ pub(super) fn check_opaque_for_cycles<'tcx>(
     Ok(())
 }
 
-/// Check that the concrete type behind `impl Trait` actually implements `Trait`.
+/// Check that the hidden type behind `impl Trait` actually implements `Trait`.
 ///
 /// This is mostly checked at the places that specify the opaque type, but we
 /// check those cases in the `param_env` of that function, which may have
diff --git a/compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs b/compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs
index 38ae7852ca9..b069a74bf5a 100644
--- a/compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs
@@ -195,11 +195,10 @@ impl<'tcx> InherentCollect<'tcx> {
             | ty::Closure(..)
             | ty::CoroutineClosure(..)
             | ty::Coroutine(..)
-            | ty::CoroutineWitness(..)
-            | ty::Alias(ty::Free, _)
-            | ty::Bound(..)
-            | ty::Placeholder(_)
-            | ty::Infer(_) => {
+            | ty::CoroutineWitness(..) => {
+                Err(self.tcx.dcx().delayed_bug("cannot define inherent `impl` for closure types"))
+            }
+            ty::Alias(ty::Free, _) | ty::Bound(..) | ty::Placeholder(_) | ty::Infer(_) => {
                 bug!("unexpected impl self type of impl: {:?} {:?}", id, self_ty);
             }
             // We could bail out here, but that will silence other useful errors.
diff --git a/compiler/rustc_hir_analysis/src/coherence/orphan.rs b/compiler/rustc_hir_analysis/src/coherence/orphan.rs
index 621431ae234..5a61248cab8 100644
--- a/compiler/rustc_hir_analysis/src/coherence/orphan.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/orphan.rs
@@ -230,10 +230,12 @@ pub(crate) fn orphan_check_impl(
             ty::Closure(..)
             | ty::CoroutineClosure(..)
             | ty::Coroutine(..)
-            | ty::CoroutineWitness(..)
-            | ty::Bound(..)
-            | ty::Placeholder(..)
-            | ty::Infer(..) => {
+            | ty::CoroutineWitness(..) => {
+                return Err(tcx
+                    .dcx()
+                    .delayed_bug("cannot define inherent `impl` for closure types"));
+            }
+            ty::Bound(..) | ty::Placeholder(..) | ty::Infer(..) => {
                 let sp = tcx.def_span(impl_def_id);
                 span_bug!(sp, "weird self type for autotrait impl")
             }
diff --git a/compiler/rustc_hir_analysis/src/collect.rs b/compiler/rustc_hir_analysis/src/collect.rs
index b72e743f95b..02baaec3713 100644
--- a/compiler/rustc_hir_analysis/src/collect.rs
+++ b/compiler/rustc_hir_analysis/src/collect.rs
@@ -1140,7 +1140,7 @@ fn recover_infer_ret_ty<'tcx>(
     // recursive function definition to leak out into the fn sig.
     let mut recovered_ret_ty = None;
     if let Some(suggestable_ret_ty) = ret_ty.make_suggestable(tcx, false, None) {
-        diag.span_suggestion(
+        diag.span_suggestion_verbose(
             infer_ret_ty.span,
             "replace with the correct return type",
             suggestable_ret_ty,
@@ -1152,7 +1152,7 @@ fn recover_infer_ret_ty<'tcx>(
         tcx.param_env(def_id),
         ret_ty,
     ) {
-        diag.span_suggestion(
+        diag.span_suggestion_verbose(
             infer_ret_ty.span,
             "replace with an appropriate return type",
             sugg,
diff --git a/compiler/rustc_hir_analysis/src/collect/item_bounds.rs b/compiler/rustc_hir_analysis/src/collect/item_bounds.rs
index ba54fa8cc0d..9841fafc82c 100644
--- a/compiler/rustc_hir_analysis/src/collect/item_bounds.rs
+++ b/compiler/rustc_hir_analysis/src/collect/item_bounds.rs
@@ -12,7 +12,7 @@ use tracing::{debug, instrument};
 
 use super::ItemCtxt;
 use super::predicates_of::assert_only_contains_predicates_from;
-use crate::hir_ty_lowering::{HirTyLowerer, PredicateFilter};
+use crate::hir_ty_lowering::{HirTyLowerer, OverlappingAsssocItemConstraints, PredicateFilter};
 
 /// For associated types we include both bounds written on the type
 /// (`type X: Trait`) and predicates from the trait: `where Self::X: Trait`.
@@ -37,7 +37,14 @@ fn associated_type_bounds<'tcx>(
 
         let icx = ItemCtxt::new(tcx, assoc_item_def_id);
         let mut bounds = Vec::new();
-        icx.lowerer().lower_bounds(item_ty, hir_bounds, &mut bounds, ty::List::empty(), filter);
+        icx.lowerer().lower_bounds(
+            item_ty,
+            hir_bounds,
+            &mut bounds,
+            ty::List::empty(),
+            filter,
+            OverlappingAsssocItemConstraints::Allowed,
+        );
 
         match filter {
             PredicateFilter::All
@@ -347,7 +354,14 @@ fn opaque_type_bounds<'tcx>(
     ty::print::with_reduced_queries!({
         let icx = ItemCtxt::new(tcx, opaque_def_id);
         let mut bounds = Vec::new();
-        icx.lowerer().lower_bounds(item_ty, hir_bounds, &mut bounds, ty::List::empty(), filter);
+        icx.lowerer().lower_bounds(
+            item_ty,
+            hir_bounds,
+            &mut bounds,
+            ty::List::empty(),
+            filter,
+            OverlappingAsssocItemConstraints::Allowed,
+        );
         // Implicit bounds are added to opaque types unless a `?Trait` bound is found
         match filter {
             PredicateFilter::All
diff --git a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
index dd3590f9ac5..ffdf2a2f4c0 100644
--- a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
@@ -18,7 +18,9 @@ use super::item_bounds::explicit_item_bounds_with_filter;
 use crate::collect::ItemCtxt;
 use crate::constrained_generic_params as cgp;
 use crate::delegation::inherit_predicates_for_delegation_item;
-use crate::hir_ty_lowering::{HirTyLowerer, PredicateFilter, RegionInferReason};
+use crate::hir_ty_lowering::{
+    HirTyLowerer, OverlappingAsssocItemConstraints, PredicateFilter, RegionInferReason,
+};
 
 /// Returns a list of all type predicates (explicit and implicit) for the definition with
 /// ID `def_id`. This includes all predicates returned by `explicit_predicates_of`, plus
@@ -187,6 +189,7 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
             &mut bounds,
             ty::List::empty(),
             PredicateFilter::All,
+            OverlappingAsssocItemConstraints::Allowed,
         );
         icx.lowerer().add_sizedness_bounds(
             &mut bounds,
@@ -289,6 +292,7 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
                     &mut bounds,
                     bound_vars,
                     PredicateFilter::All,
+                    OverlappingAsssocItemConstraints::Allowed,
                 );
                 predicates.extend(bounds);
             }
@@ -659,7 +663,14 @@ pub(super) fn implied_predicates_with_filter<'tcx>(
 
     let self_param_ty = tcx.types.self_param;
     let mut bounds = Vec::new();
-    icx.lowerer().lower_bounds(self_param_ty, superbounds, &mut bounds, ty::List::empty(), filter);
+    icx.lowerer().lower_bounds(
+        self_param_ty,
+        superbounds,
+        &mut bounds,
+        ty::List::empty(),
+        filter,
+        OverlappingAsssocItemConstraints::Allowed,
+    );
     match filter {
         PredicateFilter::All
         | PredicateFilter::SelfOnly
@@ -984,6 +995,7 @@ impl<'tcx> ItemCtxt<'tcx> {
                 &mut bounds,
                 bound_vars,
                 filter,
+                OverlappingAsssocItemConstraints::Allowed,
             );
         }
 
@@ -1063,6 +1075,7 @@ pub(super) fn const_conditions<'tcx>(
                     &mut bounds,
                     bound_vars,
                     PredicateFilter::ConstIfConst,
+                    OverlappingAsssocItemConstraints::Allowed,
                 );
             }
             _ => {}
@@ -1083,6 +1096,7 @@ pub(super) fn const_conditions<'tcx>(
             &mut bounds,
             ty::List::empty(),
             PredicateFilter::ConstIfConst,
+            OverlappingAsssocItemConstraints::Allowed,
         );
     }
 
diff --git a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
index b6d898886ac..a02990fe4ab 100644
--- a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
+++ b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
@@ -177,7 +177,7 @@ impl<'tcx> TaitConstraintLocator<'tcx> {
                 let tables = tcx.typeck(item_def_id);
                 if let Some(guar) = tables.tainted_by_errors {
                     self.insert_found(ty::OpaqueHiddenType::new_error(tcx, guar));
-                } else if let Some(&hidden_type) = tables.concrete_opaque_types.get(&self.def_id) {
+                } else if let Some(&hidden_type) = tables.hidden_types.get(&self.def_id) {
                     self.insert_found(hidden_type);
                 } else {
                     self.non_defining_use_in_defining_scope(item_def_id);
@@ -185,8 +185,8 @@ impl<'tcx> TaitConstraintLocator<'tcx> {
             }
             DefiningScopeKind::MirBorrowck => match tcx.mir_borrowck(item_def_id) {
                 Err(guar) => self.insert_found(ty::OpaqueHiddenType::new_error(tcx, guar)),
-                Ok(concrete_opaque_types) => {
-                    if let Some(&hidden_type) = concrete_opaque_types.0.get(&self.def_id) {
+                Ok(hidden_types) => {
+                    if let Some(&hidden_type) = hidden_types.0.get(&self.def_id) {
                         debug!(?hidden_type, "found constraint");
                         self.insert_found(hidden_type);
                     } else if let Err(guar) = tcx
@@ -247,7 +247,7 @@ pub(super) fn find_opaque_ty_constraints_for_rpit<'tcx>(
             let tables = tcx.typeck(owner_def_id);
             if let Some(guar) = tables.tainted_by_errors {
                 Ty::new_error(tcx, guar)
-            } else if let Some(hidden_ty) = tables.concrete_opaque_types.get(&def_id) {
+            } else if let Some(hidden_ty) = tables.hidden_types.get(&def_id) {
                 hidden_ty.ty
             } else {
                 assert!(!tcx.next_trait_solver_globally());
@@ -261,8 +261,8 @@ pub(super) fn find_opaque_ty_constraints_for_rpit<'tcx>(
             }
         }
         DefiningScopeKind::MirBorrowck => match tcx.mir_borrowck(owner_def_id) {
-            Ok(concrete_opaque_types) => {
-                if let Some(hidden_ty) = concrete_opaque_types.0.get(&def_id) {
+            Ok(hidden_types) => {
+                if let Some(hidden_ty) = hidden_types.0.get(&def_id) {
                     hidden_ty.ty
                 } else {
                     let hir_ty = tcx.type_of_opaque_hir_typeck(def_id).instantiate_identity();
diff --git a/compiler/rustc_hir_analysis/src/constrained_generic_params.rs b/compiler/rustc_hir_analysis/src/constrained_generic_params.rs
index 366b3943a05..f8d0ea3e7bf 100644
--- a/compiler/rustc_hir_analysis/src/constrained_generic_params.rs
+++ b/compiler/rustc_hir_analysis/src/constrained_generic_params.rs
@@ -4,7 +4,7 @@ use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable, TypeSuperVisitable, TypeV
 use rustc_span::Span;
 use tracing::debug;
 
-#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+#[derive(Clone, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
 pub(crate) struct Parameter(pub u32);
 
 impl From<ty::ParamTy> for Parameter {
@@ -167,15 +167,20 @@ pub(crate) fn setup_constraining_predicates<'tcx>(
     // which is `O(nt)` where `t` is the depth of type-parameter constraints,
     // remembering that `t` should be less than 7 in practice.
     //
+    // FIXME(hkBst): the big-O bound above would be accurate for the number
+    // of calls to `parameters_for`, which itself is some O(complexity of type).
+    // That would make this potentially cubic instead of merely quadratic...
+    // ...unless we cache those `parameters_for` calls.
+    //
     // Basically, I iterate over all projections and swap every
     // "ready" projection to the start of the list, such that
     // all of the projections before `i` are topologically sorted
     // and constrain all the parameters in `input_parameters`.
     //
-    // In the example, `input_parameters` starts by containing `U` - which
-    // is constrained by the trait-ref - and so on the first pass we
+    // In the first example, `input_parameters` starts by containing `U`,
+    // which is constrained by the self type `U`. Then, on the first pass we
     // observe that `<U as Iterator>::Item = T` is a "ready" projection that
-    // constrains `T` and swap it to front. As it is the sole projection,
+    // constrains `T` and swap it to the front. As it is the sole projection,
     // no more swaps can take place afterwards, with the result being
     //   * <U as Iterator>::Item = T
     //   * T: Debug
@@ -193,33 +198,25 @@ pub(crate) fn setup_constraining_predicates<'tcx>(
         for j in i..predicates.len() {
             // Note that we don't have to care about binders here,
             // as the impl trait ref never contains any late-bound regions.
-            if let ty::ClauseKind::Projection(projection) = predicates[j].0.kind().skip_binder() {
-                // Special case: watch out for some kind of sneaky attempt
-                // to project out an associated type defined by this very
-                // trait.
-                let unbound_trait_ref = projection.projection_term.trait_ref(tcx);
-                if Some(unbound_trait_ref) == impl_trait_ref {
-                    continue;
-                }
-
-                // A projection depends on its input types and determines its output
-                // type. For example, if we have
-                //     `<<T as Bar>::Baz as Iterator>::Output = <U as Iterator>::Output`
-                // Then the projection only applies if `T` is known, but it still
-                // does not determine `U`.
-                let inputs = parameters_for(tcx, projection.projection_term, true);
-                let relies_only_on_inputs = inputs.iter().all(|p| input_parameters.contains(p));
-                if !relies_only_on_inputs {
-                    continue;
-                }
+            if let ty::ClauseKind::Projection(projection) = predicates[j].0.kind().skip_binder() &&
+
+            // Special case: watch out for some kind of sneaky attempt to
+            // project out an associated type defined by this very trait.
+            !impl_trait_ref.is_some_and(|t| t == projection.projection_term.trait_ref(tcx)) &&
+
+            // A projection depends on its input types and determines its output
+            // type. For example, if we have
+            //     `<<T as Bar>::Baz as Iterator>::Output = <U as Iterator>::Output`
+            // then the projection only applies if `T` is known, but it still
+            // does not determine `U`.
+                parameters_for(tcx, projection.projection_term, true).iter().all(|p| input_parameters.contains(p))
+            {
                 input_parameters.extend(parameters_for(tcx, projection.term, false));
-            } else {
-                continue;
+
+                predicates.swap(i, j);
+                i += 1;
+                changed = true;
             }
-            // fancy control flow to bypass borrow checker
-            predicates.swap(i, j);
-            i += 1;
-            changed = true;
         }
         debug!(
             "setup_constraining_predicates: predicates={:?} \
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
index 99dc8e6e522..8682fdc5494 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
@@ -21,7 +21,8 @@ use tracing::{debug, instrument};
 use super::errors::GenericsArgsErrExtend;
 use crate::errors;
 use crate::hir_ty_lowering::{
-    AssocItemQSelf, FeedConstTy, HirTyLowerer, PredicateFilter, RegionInferReason,
+    AssocItemQSelf, FeedConstTy, HirTyLowerer, OverlappingAsssocItemConstraints, PredicateFilter,
+    RegionInferReason,
 };
 
 #[derive(Debug, Default)]
@@ -338,6 +339,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         bounds: &mut Vec<(ty::Clause<'tcx>, Span)>,
         bound_vars: &'tcx ty::List<ty::BoundVariableKind>,
         predicate_filter: PredicateFilter,
+        overlapping_assoc_constraints: OverlappingAsssocItemConstraints,
     ) where
         'tcx: 'hir,
     {
@@ -362,6 +364,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                         param_ty,
                         bounds,
                         predicate_filter,
+                        overlapping_assoc_constraints,
                     );
                 }
                 hir::GenericBound::Outlives(lifetime) => {
@@ -402,7 +405,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         trait_ref: ty::PolyTraitRef<'tcx>,
         constraint: &hir::AssocItemConstraint<'tcx>,
         bounds: &mut Vec<(ty::Clause<'tcx>, Span)>,
-        duplicates: &mut FxIndexMap<DefId, Span>,
+        duplicates: Option<&mut FxIndexMap<DefId, Span>>,
         path_span: Span,
         predicate_filter: PredicateFilter,
     ) -> Result<(), ErrorGuaranteed> {
@@ -458,17 +461,19 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             )
             .expect("failed to find associated item");
 
-        duplicates
-            .entry(assoc_item.def_id)
-            .and_modify(|prev_span| {
-                self.dcx().emit_err(errors::ValueOfAssociatedStructAlreadySpecified {
-                    span: constraint.span,
-                    prev_span: *prev_span,
-                    item_name: constraint.ident,
-                    def_path: tcx.def_path_str(assoc_item.container_id(tcx)),
-                });
-            })
-            .or_insert(constraint.span);
+        if let Some(duplicates) = duplicates {
+            duplicates
+                .entry(assoc_item.def_id)
+                .and_modify(|prev_span| {
+                    self.dcx().emit_err(errors::ValueOfAssociatedStructAlreadySpecified {
+                        span: constraint.span,
+                        prev_span: *prev_span,
+                        item_name: constraint.ident,
+                        def_path: tcx.def_path_str(assoc_item.container_id(tcx)),
+                    });
+                })
+                .or_insert(constraint.span);
+        }
 
         let projection_term = if let ty::AssocTag::Fn = assoc_tag {
             let bound_vars = tcx.late_bound_vars(constraint.hir_id);
@@ -600,6 +605,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                             bounds,
                             projection_ty.bound_vars(),
                             predicate_filter,
+                            OverlappingAsssocItemConstraints::Allowed,
                         );
                     }
                     PredicateFilter::SelfOnly
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/cmse.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/cmse.rs
index 81deb35920a..0a41659ec66 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/cmse.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/cmse.rs
@@ -134,11 +134,12 @@ fn is_valid_cmse_inputs<'tcx>(
 
     // this type is only used for layout computation, which does not rely on regions
     let fn_sig = tcx.instantiate_bound_regions_with_erased(fn_sig);
+    let fn_sig = tcx.erase_and_anonymize_regions(fn_sig);
 
     for (index, ty) in fn_sig.inputs().iter().enumerate() {
         let layout = tcx.layout_of(ty::TypingEnv::fully_monomorphized().as_query_input(*ty))?;
 
-        let align = layout.layout.align().abi.bytes();
+        let align = layout.layout.align().bytes();
         let size = layout.layout.size().bytes();
 
         accum += size;
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_trait.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_trait.rs
index c248cd7fec2..c0b13773089 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_trait.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_trait.rs
@@ -23,7 +23,9 @@ use tracing::{debug, instrument};
 
 use super::HirTyLowerer;
 use crate::errors::SelfInTypeAlias;
-use crate::hir_ty_lowering::{GenericArgCountMismatch, PredicateFilter, RegionInferReason};
+use crate::hir_ty_lowering::{
+    GenericArgCountMismatch, OverlappingAsssocItemConstraints, PredicateFilter, RegionInferReason,
+};
 
 impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     /// Lower a trait object type from the HIR to our internal notion of a type.
@@ -60,6 +62,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 dummy_self,
                 &mut user_written_bounds,
                 PredicateFilter::SelfOnly,
+                OverlappingAsssocItemConstraints::Forbidden,
             );
             if let Err(GenericArgCountMismatch { invalid_args, .. }) = result.correct {
                 potential_assoc_types.extend(invalid_args);
@@ -157,10 +160,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 self.dcx()
                     .struct_span_err(
                         span,
-                        format!(
-                            "conflicting associated type bounds for `{item}` when \
-                            expanding trait alias"
-                        ),
+                        format!("conflicting associated type bounds for `{item}`"),
                     )
                     .with_span_label(
                         old_proj_span,
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 9b198d04454..eb660804c2b 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
@@ -332,6 +332,15 @@ pub(crate) enum GenericArgPosition {
     MethodCall,
 }
 
+/// Whether to allow duplicate associated iten constraints in a trait ref, e.g.
+/// `Trait<Assoc = Ty, Assoc = Ty>`. This is forbidden in `dyn Trait<...>`
+/// but allowed everywhere else.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub(crate) enum OverlappingAsssocItemConstraints {
+    Allowed,
+    Forbidden,
+}
+
 /// A marker denoting that the generic arguments that were
 /// provided did not match the respective generic parameters.
 #[derive(Clone, Debug)]
@@ -752,6 +761,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         self_ty: Ty<'tcx>,
         bounds: &mut Vec<(ty::Clause<'tcx>, Span)>,
         predicate_filter: PredicateFilter,
+        overlapping_assoc_item_constraints: OverlappingAsssocItemConstraints,
     ) -> GenericArgCountResult {
         let tcx = self.tcx();
 
@@ -908,7 +918,10 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             }
         }
 
-        let mut dup_constraints = FxIndexMap::default();
+        let mut dup_constraints = (overlapping_assoc_item_constraints
+            == OverlappingAsssocItemConstraints::Forbidden)
+            .then_some(FxIndexMap::default());
+
         for constraint in trait_segment.args().constraints {
             // Don't register any associated item constraints for negative bounds,
             // since we should have emitted an error for them earlier, and they
@@ -927,7 +940,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                 poly_trait_ref,
                 constraint,
                 bounds,
-                &mut dup_constraints,
+                dup_constraints.as_mut(),
                 constraint.span,
                 predicate_filter,
             );
@@ -2484,6 +2497,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                     &mut bounds,
                     ty::List::empty(),
                     PredicateFilter::All,
+                    OverlappingAsssocItemConstraints::Allowed,
                 );
                 self.add_sizedness_bounds(
                     &mut bounds,
diff --git a/compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs b/compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs
index b38639ed8c6..13c744ab461 100644
--- a/compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs
+++ b/compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs
@@ -275,7 +275,7 @@ fn check_duplicate_params<'tcx>(
     span: Span,
 ) -> Result<(), ErrorGuaranteed> {
     let mut base_params = cgp::parameters_for(tcx, parent_args, true);
-    base_params.sort_by_key(|param| param.0);
+    base_params.sort_unstable();
     if let (_, [duplicate, ..]) = base_params.partition_dedup() {
         let param = impl1_args[duplicate.0 as usize];
         return Err(tcx
diff --git a/compiler/rustc_hir_typeck/src/expr.rs b/compiler/rustc_hir_typeck/src/expr.rs
index 7adbee7ff28..d1ce0afddf9 100644
--- a/compiler/rustc_hir_typeck/src/expr.rs
+++ b/compiler/rustc_hir_typeck/src/expr.rs
@@ -1633,8 +1633,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         expected: Expectation<'tcx>,
     ) -> Ty<'tcx> {
         let rcvr_t = self.check_expr(rcvr);
-        // no need to check for bot/err -- callee does that
-        let rcvr_t = self.structurally_resolve_type(rcvr.span, rcvr_t);
+        let rcvr_t = self.try_structurally_resolve_type(rcvr.span, rcvr_t);
 
         match self.lookup_method(rcvr_t, segment, segment.ident.span, expr, rcvr, args) {
             Ok(method) => {
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
index 833ce433d56..35253e4c291 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
@@ -611,19 +611,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         typeck_results.rvalue_scopes = rvalue_scopes;
     }
 
-    /// Unify the inference variables corresponding to coroutine witnesses, and save all the
-    /// predicates that were stalled on those inference variables.
-    ///
-    /// This process allows to conservatively save all predicates that do depend on the coroutine
-    /// interior types, for later processing by `check_coroutine_obligations`.
-    ///
-    /// We must not attempt to select obligations after this method has run, or risk query cycle
-    /// ICE.
+    /// Drain all obligations that are stalled on coroutines defined in this body.
     #[instrument(level = "debug", skip(self))]
-    pub(crate) fn resolve_coroutine_interiors(&self) {
-        // Try selecting all obligations that are not blocked on inference variables.
-        // Once we start unifying coroutine witnesses, trying to select obligations on them will
-        // trigger query cycle ICEs, as doing so requires MIR.
+    pub(crate) fn drain_stalled_coroutine_obligations(&self) {
+        // Make as much inference progress as possible before
+        // draining the stalled coroutine obligations as this may
+        // change obligations from being stalled on infer vars to
+        // being stalled on a coroutine.
         self.select_obligations_where_possible(|_| {});
 
         let ty::TypingMode::Analysis { defining_opaque_types_and_generators } = self.typing_mode()
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
index 7ca8580e098..c8943d4634e 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
@@ -2803,9 +2803,7 @@ impl<'a, 'b, 'tcx> ArgMatchingCtxt<'a, 'b, 'tcx> {
         if let Some((assoc, fn_sig)) = self.similar_assoc(call_name)
             && fn_sig.inputs()[1..]
                 .iter()
-                .zip(input_types.iter())
-                .all(|(expected, found)| self.may_coerce(*expected, *found))
-            && fn_sig.inputs()[1..].len() == input_types.len()
+                .eq_by(input_types, |expected, found| self.may_coerce(*expected, found))
         {
             let assoc_name = assoc.name();
             err.span_suggestion_verbose(
diff --git a/compiler/rustc_hir_typeck/src/lib.rs b/compiler/rustc_hir_typeck/src/lib.rs
index 43a23822fd1..9f5a85b6926 100644
--- a/compiler/rustc_hir_typeck/src/lib.rs
+++ b/compiler/rustc_hir_typeck/src/lib.rs
@@ -5,6 +5,7 @@
 #![feature(box_patterns)]
 #![feature(if_let_guard)]
 #![feature(iter_intersperse)]
+#![feature(iter_order_by)]
 #![feature(never_type)]
 // tidy-alphabetical-end
 
@@ -242,18 +243,15 @@ fn typeck_with_inspect<'tcx>(
 
     debug!(pending_obligations = ?fcx.fulfillment_cx.borrow().pending_obligations());
 
-    // This must be the last thing before `report_ambiguity_errors`.
-    fcx.resolve_coroutine_interiors();
-
-    debug!(pending_obligations = ?fcx.fulfillment_cx.borrow().pending_obligations());
-
     // We need to handle opaque types before emitting ambiguity errors as applying
     // defining uses may guide type inference.
     if fcx.next_trait_solver() {
         fcx.handle_opaque_type_uses_next();
     }
 
-    fcx.select_obligations_where_possible(|_| {});
+    // This must be the last thing before `report_ambiguity_errors` below except `select_obligations_where_possible`.
+    // So don't put anything after this.
+    fcx.drain_stalled_coroutine_obligations();
     if fcx.infcx.tainted_by_errors().is_none() {
         fcx.report_ambiguity_errors();
     }
diff --git a/compiler/rustc_hir_typeck/src/method/confirm.rs b/compiler/rustc_hir_typeck/src/method/confirm.rs
index a23910a2006..b23e7ae8e77 100644
--- a/compiler/rustc_hir_typeck/src/method/confirm.rs
+++ b/compiler/rustc_hir_typeck/src/method/confirm.rs
@@ -172,7 +172,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
         // Commit the autoderefs by calling `autoderef` again, but this
         // time writing the results into the various typeck results.
         let mut autoderef = self.autoderef(self.call_expr.span, unadjusted_self_ty);
-        let Some((ty, n)) = autoderef.nth(pick.autoderefs) else {
+        let Some((mut target, n)) = autoderef.nth(pick.autoderefs) else {
             return Ty::new_error_with_message(
                 self.tcx,
                 DUMMY_SP,
@@ -182,8 +182,6 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
         assert_eq!(n, pick.autoderefs);
 
         let mut adjustments = self.adjust_steps(&autoderef);
-        let mut target = self.structurally_resolve_type(autoderef.span(), ty);
-
         match pick.autoref_or_ptr_adjustment {
             Some(probe::AutorefOrPtrAdjustment::Autoref { mutbl, unsize }) => {
                 let region = self.next_region_var(RegionVariableOrigin::Autoref(self.span));
diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs
index 4185f7f6996..12f80a197b1 100644
--- a/compiler/rustc_hir_typeck/src/method/probe.rs
+++ b/compiler/rustc_hir_typeck/src/method/probe.rs
@@ -13,7 +13,7 @@ use rustc_hir::def::DefKind;
 use rustc_hir_analysis::autoderef::{self, Autoderef};
 use rustc_infer::infer::canonical::{Canonical, OriginalQueryValues, QueryResponse};
 use rustc_infer::infer::{BoundRegionConversionTime, DefineOpaqueTypes, InferOk, TyCtxtInferExt};
-use rustc_infer::traits::ObligationCauseCode;
+use rustc_infer::traits::{ObligationCauseCode, PredicateObligation, query};
 use rustc_middle::middle::stability;
 use rustc_middle::ty::elaborate::supertrait_def_ids;
 use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams, simplify_type};
@@ -30,7 +30,8 @@ use rustc_span::edit_distance::{
 use rustc_span::{DUMMY_SP, Ident, Span, Symbol, sym};
 use rustc_trait_selection::error_reporting::infer::need_type_info::TypeAnnotationNeeded;
 use rustc_trait_selection::infer::InferCtxtExt as _;
-use rustc_trait_selection::traits::query::CanonicalTyGoal;
+use rustc_trait_selection::solve::Goal;
+use rustc_trait_selection::traits::query::CanonicalMethodAutoderefStepsGoal;
 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
 use rustc_trait_selection::traits::query::method_autoderef::{
     CandidateStep, MethodAutoderefBadTy, MethodAutoderefStepsResult,
@@ -389,10 +390,16 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         OP: FnOnce(ProbeContext<'_, 'tcx>) -> Result<R, MethodError<'tcx>>,
     {
         let mut orig_values = OriginalQueryValues::default();
-        let query_input = self.canonicalize_query(
-            ParamEnvAnd { param_env: self.param_env, value: self_ty },
-            &mut orig_values,
-        );
+        let predefined_opaques_in_body = if self.next_trait_solver() {
+            self.tcx.mk_predefined_opaques_in_body_from_iter(
+                self.inner.borrow_mut().opaque_types().iter_opaque_types().map(|(k, v)| (k, v.ty)),
+            )
+        } else {
+            ty::List::empty()
+        };
+        let value = query::MethodAutoderefSteps { predefined_opaques_in_body, self_ty };
+        let query_input = self
+            .canonicalize_query(ParamEnvAnd { param_env: self.param_env, value }, &mut orig_values);
 
         let steps = match mode {
             Mode::MethodCall => self.tcx.method_autoderef_steps(query_input),
@@ -403,13 +410,15 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // special handling for this "trivial case" is a good idea.
 
                 let infcx = &self.infcx;
-                let (ParamEnvAnd { param_env: _, value: self_ty }, var_values) =
+                let (ParamEnvAnd { param_env: _, value }, var_values) =
                     infcx.instantiate_canonical(span, &query_input.canonical);
+                let query::MethodAutoderefSteps { predefined_opaques_in_body: _, self_ty } = value;
                 debug!(?self_ty, ?query_input, "probe_op: Mode::Path");
                 MethodAutoderefStepsResult {
                     steps: infcx.tcx.arena.alloc_from_iter([CandidateStep {
                         self_ty: self
                             .make_query_response_ignoring_pending_obligations(var_values, self_ty),
+                        self_ty_is_opaque: false,
                         autoderefs: 0,
                         from_unsafe_deref: false,
                         unsize: false,
@@ -479,6 +488,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     ty::Infer(ty::TyVar(_)) => {
                         let raw_ptr_call = bad_ty.reached_raw_pointer
                             && !self.tcx.features().arbitrary_self_types();
+                        // FIXME: Ideally we'd use the span of the self-expr here,
+                        // not of the method path.
                         let mut err = self.err_ctxt().emit_inference_failure_err(
                             self.body_id,
                             span,
@@ -553,12 +564,44 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
 pub(crate) fn method_autoderef_steps<'tcx>(
     tcx: TyCtxt<'tcx>,
-    goal: CanonicalTyGoal<'tcx>,
+    goal: CanonicalMethodAutoderefStepsGoal<'tcx>,
 ) -> MethodAutoderefStepsResult<'tcx> {
     debug!("method_autoderef_steps({:?})", goal);
 
     let (ref infcx, goal, inference_vars) = tcx.infer_ctxt().build_with_canonical(DUMMY_SP, &goal);
-    let ParamEnvAnd { param_env, value: self_ty } = goal;
+    let ParamEnvAnd {
+        param_env,
+        value: query::MethodAutoderefSteps { predefined_opaques_in_body, self_ty },
+    } = goal;
+    for (key, ty) in predefined_opaques_in_body {
+        let prev =
+            infcx.register_hidden_type_in_storage(key, ty::OpaqueHiddenType { span: DUMMY_SP, ty });
+        // It may be possible that two entries in the opaque type storage end up
+        // with the same key after resolving contained inference variables.
+        //
+        // We could put them in the duplicate list but don't have to. The opaques we
+        // encounter here are already tracked in the caller, so there's no need to
+        // also store them here. We'd take them out when computing the query response
+        // and then discard them, as they're already present in the input.
+        //
+        // Ideally we'd drop duplicate opaque type definitions when computing
+        // the canonical input. This is more annoying to implement and may cause a
+        // perf regression, so we do it inside of the query for now.
+        if let Some(prev) = prev {
+            debug!(?key, ?ty, ?prev, "ignore duplicate in `opaque_types_storage`");
+        }
+    }
+
+    // We accept not-yet-defined opaque types in the autoderef
+    // chain to support recursive calls. We do error if the final
+    // infer var is not an opaque.
+    let self_ty_is_opaque = |ty: Ty<'_>| {
+        if let &ty::Infer(ty::TyVar(vid)) = ty.kind() {
+            infcx.has_opaques_with_sub_unified_hidden_type(vid)
+        } else {
+            false
+        }
+    };
 
     // If arbitrary self types is not enabled, we follow the chain of
     // `Deref<Target=T>`. If arbitrary self types is enabled, we instead
@@ -593,6 +636,7 @@ pub(crate) fn method_autoderef_steps<'tcx>(
                 let step = CandidateStep {
                     self_ty: infcx
                         .make_query_response_ignoring_pending_obligations(inference_vars, ty),
+                    self_ty_is_opaque: self_ty_is_opaque(ty),
                     autoderefs: d,
                     from_unsafe_deref: reached_raw_pointer,
                     unsize: false,
@@ -613,6 +657,7 @@ pub(crate) fn method_autoderef_steps<'tcx>(
                 let step = CandidateStep {
                     self_ty: infcx
                         .make_query_response_ignoring_pending_obligations(inference_vars, ty),
+                    self_ty_is_opaque: self_ty_is_opaque(ty),
                     autoderefs: d,
                     from_unsafe_deref: reached_raw_pointer,
                     unsize: false,
@@ -629,7 +674,11 @@ pub(crate) fn method_autoderef_steps<'tcx>(
     };
     let final_ty = autoderef_via_deref.final_ty();
     let opt_bad_ty = match final_ty.kind() {
-        ty::Infer(ty::TyVar(_)) | ty::Error(_) => Some(MethodAutoderefBadTy {
+        ty::Infer(ty::TyVar(_)) if !self_ty_is_opaque(final_ty) => Some(MethodAutoderefBadTy {
+            reached_raw_pointer,
+            ty: infcx.make_query_response_ignoring_pending_obligations(inference_vars, final_ty),
+        }),
+        ty::Error(_) => Some(MethodAutoderefBadTy {
             reached_raw_pointer,
             ty: infcx.make_query_response_ignoring_pending_obligations(inference_vars, final_ty),
         }),
@@ -640,6 +689,7 @@ pub(crate) fn method_autoderef_steps<'tcx>(
                     inference_vars,
                     Ty::new_slice(infcx.tcx, *elem_ty),
                 ),
+                self_ty_is_opaque: false,
                 autoderefs,
                 // this could be from an unsafe deref if we had
                 // a *mut/const [T; N]
@@ -655,7 +705,8 @@ pub(crate) fn method_autoderef_steps<'tcx>(
     };
 
     debug!("method_autoderef_steps: steps={:?} opt_bad_ty={:?}", steps, opt_bad_ty);
-
+    // Need to empty the opaque types storage before it gets dropped.
+    let _ = infcx.take_opaque_types();
     MethodAutoderefStepsResult {
         steps: tcx.arena.alloc_from_iter(steps),
         opt_bad_ty: opt_bad_ty.map(|ty| &*tcx.arena.alloc(ty)),
@@ -1203,7 +1254,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                 !step.self_ty.value.references_error() && !step.from_unsafe_deref
             })
             .find_map(|step| {
-                let InferOk { value: self_ty, obligations: _ } = self
+                let InferOk { value: self_ty, obligations: instantiate_self_ty_obligations } = self
                     .fcx
                     .probe_instantiate_query_response(
                         self.span,
@@ -1214,7 +1265,12 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                         span_bug!(self.span, "{:?} was applicable but now isn't?", step.self_ty)
                     });
 
-                let by_value_pick = self.pick_by_value_method(step, self_ty, pick_diag_hints);
+                let by_value_pick = self.pick_by_value_method(
+                    step,
+                    self_ty,
+                    &instantiate_self_ty_obligations,
+                    pick_diag_hints,
+                );
 
                 // Check for shadowing of a by-reference method by a by-value method (see comments on check_for_shadowing)
                 if let Some(by_value_pick) = by_value_pick {
@@ -1225,6 +1281,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                                     by_value_pick,
                                     step,
                                     self_ty,
+                                    &instantiate_self_ty_obligations,
                                     mutbl,
                                     track_unstable_candidates,
                                 ) {
@@ -1239,6 +1296,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                 let autoref_pick = self.pick_autorefd_method(
                     step,
                     self_ty,
+                    &instantiate_self_ty_obligations,
                     hir::Mutability::Not,
                     pick_diag_hints,
                     None,
@@ -1252,6 +1310,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                                 autoref_pick,
                                 step,
                                 self_ty,
+                                &instantiate_self_ty_obligations,
                                 hir::Mutability::Mut,
                                 track_unstable_candidates,
                             ) {
@@ -1288,12 +1347,27 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                 self.pick_autorefd_method(
                     step,
                     self_ty,
+                    &instantiate_self_ty_obligations,
                     hir::Mutability::Mut,
                     pick_diag_hints,
                     None,
                 )
-                .or_else(|| self.pick_const_ptr_method(step, self_ty, pick_diag_hints))
-                .or_else(|| self.pick_reborrow_pin_method(step, self_ty, pick_diag_hints))
+                .or_else(|| {
+                    self.pick_const_ptr_method(
+                        step,
+                        self_ty,
+                        &instantiate_self_ty_obligations,
+                        pick_diag_hints,
+                    )
+                })
+                .or_else(|| {
+                    self.pick_reborrow_pin_method(
+                        step,
+                        self_ty,
+                        &instantiate_self_ty_obligations,
+                        pick_diag_hints,
+                    )
+                })
             })
     }
 
@@ -1317,6 +1391,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         possible_shadower: &Pick<'tcx>,
         step: &CandidateStep<'tcx>,
         self_ty: Ty<'tcx>,
+        instantiate_self_ty_obligations: &[PredicateObligation<'tcx>],
         mutbl: hir::Mutability,
         track_unstable_candidates: bool,
     ) -> Result<(), MethodError<'tcx>> {
@@ -1381,6 +1456,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         let potentially_shadowed_pick = self.pick_autorefd_method(
             step,
             self_ty,
+            instantiate_self_ty_obligations,
             mutbl,
             &mut pick_diag_hints,
             Some(&pick_constraints),
@@ -1407,13 +1483,14 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         &self,
         step: &CandidateStep<'tcx>,
         self_ty: Ty<'tcx>,
+        instantiate_self_ty_obligations: &[PredicateObligation<'tcx>],
         pick_diag_hints: &mut PickDiagHints<'_, 'tcx>,
     ) -> Option<PickResult<'tcx>> {
         if step.unsize {
             return None;
         }
 
-        self.pick_method(self_ty, pick_diag_hints, None).map(|r| {
+        self.pick_method(self_ty, instantiate_self_ty_obligations, pick_diag_hints, None).map(|r| {
             r.map(|mut pick| {
                 pick.autoderefs = step.autoderefs;
 
@@ -1450,6 +1527,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         &self,
         step: &CandidateStep<'tcx>,
         self_ty: Ty<'tcx>,
+        instantiate_self_ty_obligations: &[PredicateObligation<'tcx>],
         mutbl: hir::Mutability,
         pick_diag_hints: &mut PickDiagHints<'_, 'tcx>,
         pick_constraints: Option<&PickConstraintsForShadowed>,
@@ -1466,7 +1544,13 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         let region = tcx.lifetimes.re_erased;
 
         let autoref_ty = Ty::new_ref(tcx, region, self_ty, mutbl);
-        self.pick_method(autoref_ty, pick_diag_hints, pick_constraints).map(|r| {
+        self.pick_method(
+            autoref_ty,
+            instantiate_self_ty_obligations,
+            pick_diag_hints,
+            pick_constraints,
+        )
+        .map(|r| {
             r.map(|mut pick| {
                 pick.autoderefs = step.autoderefs;
                 pick.autoref_or_ptr_adjustment =
@@ -1482,6 +1566,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         &self,
         step: &CandidateStep<'tcx>,
         self_ty: Ty<'tcx>,
+        instantiate_self_ty_obligations: &[PredicateObligation<'tcx>],
         pick_diag_hints: &mut PickDiagHints<'_, 'tcx>,
     ) -> Option<PickResult<'tcx>> {
         if !self.tcx.features().pin_ergonomics() {
@@ -1503,14 +1588,16 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
 
         let region = self.tcx.lifetimes.re_erased;
         let autopin_ty = Ty::new_pinned_ref(self.tcx, region, inner_ty, hir::Mutability::Not);
-        self.pick_method(autopin_ty, pick_diag_hints, None).map(|r| {
-            r.map(|mut pick| {
-                pick.autoderefs = step.autoderefs;
-                pick.autoref_or_ptr_adjustment =
-                    Some(AutorefOrPtrAdjustment::ReborrowPin(hir::Mutability::Not));
-                pick
-            })
-        })
+        self.pick_method(autopin_ty, instantiate_self_ty_obligations, pick_diag_hints, None).map(
+            |r| {
+                r.map(|mut pick| {
+                    pick.autoderefs = step.autoderefs;
+                    pick.autoref_or_ptr_adjustment =
+                        Some(AutorefOrPtrAdjustment::ReborrowPin(hir::Mutability::Not));
+                    pick
+                })
+            },
+        )
     }
 
     /// If `self_ty` is `*mut T` then this picks `*const T` methods. The reason why we have a
@@ -1520,6 +1607,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         &self,
         step: &CandidateStep<'tcx>,
         self_ty: Ty<'tcx>,
+        instantiate_self_ty_obligations: &[PredicateObligation<'tcx>],
         pick_diag_hints: &mut PickDiagHints<'_, 'tcx>,
     ) -> Option<PickResult<'tcx>> {
         // Don't convert an unsized reference to ptr
@@ -1532,18 +1620,21 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         };
 
         let const_ptr_ty = Ty::new_imm_ptr(self.tcx, ty);
-        self.pick_method(const_ptr_ty, pick_diag_hints, None).map(|r| {
-            r.map(|mut pick| {
-                pick.autoderefs = step.autoderefs;
-                pick.autoref_or_ptr_adjustment = Some(AutorefOrPtrAdjustment::ToConstPtr);
-                pick
-            })
-        })
+        self.pick_method(const_ptr_ty, instantiate_self_ty_obligations, pick_diag_hints, None).map(
+            |r| {
+                r.map(|mut pick| {
+                    pick.autoderefs = step.autoderefs;
+                    pick.autoref_or_ptr_adjustment = Some(AutorefOrPtrAdjustment::ToConstPtr);
+                    pick
+                })
+            },
+        )
     }
 
     fn pick_method(
         &self,
         self_ty: Ty<'tcx>,
+        instantiate_self_ty_obligations: &[PredicateObligation<'tcx>],
         pick_diag_hints: &mut PickDiagHints<'_, 'tcx>,
         pick_constraints: Option<&PickConstraintsForShadowed>,
     ) -> Option<PickResult<'tcx>> {
@@ -1553,8 +1644,13 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
             [("inherent", &self.inherent_candidates), ("extension", &self.extension_candidates)]
         {
             debug!("searching {} candidates", kind);
-            let res =
-                self.consider_candidates(self_ty, candidates, pick_diag_hints, pick_constraints);
+            let res = self.consider_candidates(
+                self_ty,
+                instantiate_self_ty_obligations,
+                candidates,
+                pick_diag_hints,
+                pick_constraints,
+            );
             if let Some(pick) = res {
                 return Some(pick);
             }
@@ -1563,6 +1659,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         if self.private_candidate.get().is_none() {
             if let Some(Ok(pick)) = self.consider_candidates(
                 self_ty,
+                instantiate_self_ty_obligations,
                 &self.private_candidates,
                 &mut PickDiagHints {
                     unstable_candidates: None,
@@ -1579,6 +1676,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
     fn consider_candidates(
         &self,
         self_ty: Ty<'tcx>,
+        instantiate_self_ty_obligations: &[PredicateObligation<'tcx>],
         candidates: &[Candidate<'tcx>],
         pick_diag_hints: &mut PickDiagHints<'_, 'tcx>,
         pick_constraints: Option<&PickConstraintsForShadowed>,
@@ -1595,6 +1693,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                     probe,
                     self.consider_probe(
                         self_ty,
+                        instantiate_self_ty_obligations,
                         probe,
                         &mut pick_diag_hints.unsatisfied_predicates,
                     ),
@@ -1779,10 +1878,11 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         }
     }
 
-    #[instrument(level = "trace", skip(self, possibly_unsatisfied_predicates), ret)]
+    #[instrument(level = "debug", skip(self, possibly_unsatisfied_predicates), ret)]
     fn consider_probe(
         &self,
         self_ty: Ty<'tcx>,
+        instantiate_self_ty_obligations: &[PredicateObligation<'tcx>],
         probe: &Candidate<'tcx>,
         possibly_unsatisfied_predicates: &mut Vec<(
             ty::Predicate<'tcx>,
@@ -1790,8 +1890,6 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
             Option<ObligationCause<'tcx>>,
         )>,
     ) -> ProbeResult {
-        debug!("consider_probe: self_ty={:?} probe={:?}", self_ty, probe);
-
         self.probe(|snapshot| {
             let outer_universe = self.universe();
 
@@ -1799,6 +1897,21 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
             let cause = &self.misc(self.span);
             let ocx = ObligationCtxt::new_with_diagnostics(self);
 
+            // Subtle: we're not *really* instantiating the current self type while
+            // probing, but instead fully recompute the autoderef steps once we've got
+            // a final `Pick`. We can't nicely handle these obligations outside of a probe.
+            //
+            // We simply handle them for each candidate here for now. That's kinda scuffed
+            // and ideally we just put them into the `FnCtxt` right away. We need to consider
+            // them to deal with defining uses in `method_autoderef_steps`.
+            if self.next_trait_solver() {
+                ocx.register_obligations(instantiate_self_ty_obligations.iter().cloned());
+                let errors = ocx.select_where_possible();
+                if !errors.is_empty() {
+                    unreachable!("unexpected autoderef error {errors:?}");
+                }
+            }
+
             let mut trait_predicate = None;
             let (mut xform_self_ty, mut xform_ret_ty);
 
@@ -2041,6 +2154,12 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                 }
             }
 
+            if self.infcx.next_trait_solver() {
+                if self.should_reject_candidate_due_to_opaque_treated_as_rigid(trait_predicate) {
+                    result = ProbeResult::NoMatch;
+                }
+            }
+
             // Previously, method probe used `evaluate_predicate` to determine if a predicate
             // was impossible to satisfy. This did a leak check, so we must also do a leak
             // check here to prevent backwards-incompatible ambiguity being introduced. See
@@ -2054,6 +2173,80 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         })
     }
 
+    /// Trait candidates for not-yet-defined opaque types are a somewhat hacky.
+    ///
+    /// We want to only accept trait methods if they were hold even if the
+    /// opaque types were rigid. To handle this, we both check that for trait
+    /// candidates the goal were to hold even when treating opaques as rigid,
+    /// see [OpaqueTypesJank](rustc_trait_selection::solve::OpaqueTypesJank).
+    ///
+    /// We also check that all opaque types encountered as self types in the
+    /// autoderef chain don't get constrained when applying the candidate.
+    /// Importantly, this also handles calling methods taking `&self` on
+    /// `impl Trait` to reject the "by-self" candidate.
+    ///
+    /// This needs to happen at the end of `consider_probe` as we need to take
+    /// all the constraints from that into account.
+    #[instrument(level = "debug", skip(self), ret)]
+    fn should_reject_candidate_due_to_opaque_treated_as_rigid(
+        &self,
+        trait_predicate: Option<ty::Predicate<'tcx>>,
+    ) -> bool {
+        // This function is what hacky and doesn't perfectly do what we want it to.
+        // It's not soundness critical and we should be able to freely improve this
+        // in the future.
+        //
+        // Some concrete edge cases include the fact that `goal_may_hold_opaque_types_jank`
+        // also fails if there are any constraints opaques which are never used as a self
+        // type. We also allow where-bounds which are currently ambiguous but end up
+        // constraining an opaque later on.
+
+        // Check whether the trait candidate would not be applicable if the
+        // opaque type were rigid.
+        if let Some(predicate) = trait_predicate {
+            let goal = Goal { param_env: self.param_env, predicate };
+            if !self.infcx.goal_may_hold_opaque_types_jank(goal) {
+                return true;
+            }
+        }
+
+        // Check whether any opaque types in the autoderef chain have been
+        // constrained.
+        for step in self.steps {
+            if step.self_ty_is_opaque {
+                debug!(?step.autoderefs, ?step.self_ty, "self_type_is_opaque");
+                let constrained_opaque = self.probe(|_| {
+                    // If we fail to instantiate the self type of this
+                    // step, this part of the deref-chain is no longer
+                    // reachable. In this case we don't care about opaque
+                    // types there.
+                    let Ok(ok) = self.fcx.probe_instantiate_query_response(
+                        self.span,
+                        self.orig_steps_var_values,
+                        &step.self_ty,
+                    ) else {
+                        debug!("failed to instantiate self_ty");
+                        return false;
+                    };
+                    let ocx = ObligationCtxt::new(self);
+                    let self_ty = ocx.register_infer_ok_obligations(ok);
+                    if !ocx.select_where_possible().is_empty() {
+                        debug!("failed to prove instantiate self_ty obligations");
+                        return false;
+                    }
+
+                    !self.resolve_vars_if_possible(self_ty).is_ty_var()
+                });
+                if constrained_opaque {
+                    debug!("opaque type has been constrained");
+                    return true;
+                }
+            }
+        }
+
+        false
+    }
+
     /// Sometimes we get in a situation where we have multiple probes that are all impls of the
     /// same trait, but we don't know which impl to use. In this case, since in all cases the
     /// external interface of the method can be determined from the trait, it's ok not to decide.
diff --git a/compiler/rustc_hir_typeck/src/method/suggest.rs b/compiler/rustc_hir_typeck/src/method/suggest.rs
index 024b9ee08c2..44602e62899 100644
--- a/compiler/rustc_hir_typeck/src/method/suggest.rs
+++ b/compiler/rustc_hir_typeck/src/method/suggest.rs
@@ -1914,9 +1914,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         if let Some(ref args) = call_args
                             && fn_sig.inputs()[1..]
                                 .iter()
-                                .zip(args.into_iter())
-                                .all(|(expected, found)| self.may_coerce(*expected, *found))
-                            && fn_sig.inputs()[1..].len() == args.len()
+                                .eq_by(args, |expected, found| self.may_coerce(*expected, *found))
                         {
                             err.span_suggestion_verbose(
                                 item_name.span,
diff --git a/compiler/rustc_hir_typeck/src/opaque_types.rs b/compiler/rustc_hir_typeck/src/opaque_types.rs
index 5cefa506b5a..4c1fe69405e 100644
--- a/compiler/rustc_hir_typeck/src/opaque_types.rs
+++ b/compiler/rustc_hir_typeck/src/opaque_types.rs
@@ -15,7 +15,7 @@ use crate::FnCtxt;
 
 impl<'tcx> FnCtxt<'_, 'tcx> {
     /// This takes all the opaque type uses during HIR typeck. It first computes
-    /// the concrete hidden type by iterating over all defining uses.
+    /// the hidden type by iterating over all defining uses.
     ///
     /// A use during HIR typeck is defining if all non-lifetime arguments are
     /// unique generic parameters and the hidden type does not reference any
@@ -35,8 +35,8 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
         }
         debug!(?opaque_types);
 
-        self.compute_concrete_opaque_types(&opaque_types);
-        self.apply_computed_concrete_opaque_types(&opaque_types);
+        self.compute_definition_site_hidden_types(&opaque_types);
+        self.apply_definition_site_hidden_types(&opaque_types);
     }
 }
 
@@ -71,7 +71,7 @@ impl<'tcx> UsageKind<'tcx> {
 }
 
 impl<'tcx> FnCtxt<'_, 'tcx> {
-    fn compute_concrete_opaque_types(
+    fn compute_definition_site_hidden_types(
         &mut self,
         opaque_types: &[(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>)],
     ) {
@@ -142,7 +142,7 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
 
             self.typeck_results
                 .borrow_mut()
-                .concrete_opaque_types
+                .hidden_types
                 .insert(def_id, OpaqueHiddenType::new_error(tcx, guar));
             self.set_tainted_by_errors(guar);
         }
@@ -161,7 +161,7 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
         ) {
             match err {
                 NonDefiningUseReason::Tainted(guar) => {
-                    self.typeck_results.borrow_mut().concrete_opaque_types.insert(
+                    self.typeck_results.borrow_mut().hidden_types.insert(
                         opaque_type_key.def_id,
                         OpaqueHiddenType::new_error(self.tcx, guar),
                     );
@@ -197,20 +197,19 @@ impl<'tcx> FnCtxt<'_, 'tcx> {
         let prev = self
             .typeck_results
             .borrow_mut()
-            .concrete_opaque_types
+            .hidden_types
             .insert(opaque_type_key.def_id, hidden_type);
         assert!(prev.is_none());
         UsageKind::HasDefiningUse
     }
 
-    fn apply_computed_concrete_opaque_types(
+    fn apply_definition_site_hidden_types(
         &mut self,
         opaque_types: &[(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>)],
     ) {
         let tcx = self.tcx;
         for &(key, hidden_type) in opaque_types {
-            let expected =
-                *self.typeck_results.borrow_mut().concrete_opaque_types.get(&key.def_id).unwrap();
+            let expected = *self.typeck_results.borrow_mut().hidden_types.get(&key.def_id).unwrap();
 
             let expected = EarlyBinder::bind(expected.ty).instantiate(tcx, key.args);
             self.demand_eqtype(hidden_type.span, expected, hidden_type.ty);
diff --git a/compiler/rustc_hir_typeck/src/writeback.rs b/compiler/rustc_hir_typeck/src/writeback.rs
index d01eeb9a4b6..697029e55f7 100644
--- a/compiler/rustc_hir_typeck/src/writeback.rs
+++ b/compiler/rustc_hir_typeck/src/writeback.rs
@@ -550,13 +550,12 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
     fn visit_opaque_types_next(&mut self) {
         let mut fcx_typeck_results = self.fcx.typeck_results.borrow_mut();
         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
-        for hidden_ty in fcx_typeck_results.concrete_opaque_types.values() {
+        for hidden_ty in fcx_typeck_results.hidden_types.values() {
             assert!(!hidden_ty.has_infer());
         }
 
-        assert_eq!(self.typeck_results.concrete_opaque_types.len(), 0);
-        self.typeck_results.concrete_opaque_types =
-            mem::take(&mut fcx_typeck_results.concrete_opaque_types);
+        assert_eq!(self.typeck_results.hidden_types.len(), 0);
+        self.typeck_results.hidden_types = mem::take(&mut fcx_typeck_results.hidden_types);
     }
 
     #[instrument(skip(self), level = "debug")]
@@ -588,7 +587,7 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
                 hidden_type.span,
                 DefiningScopeKind::HirTypeck,
             ) {
-                self.typeck_results.concrete_opaque_types.insert(
+                self.typeck_results.hidden_types.insert(
                     opaque_type_key.def_id,
                     ty::OpaqueHiddenType::new_error(tcx, err.report(self.fcx)),
                 );
@@ -600,16 +599,11 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
                 DefiningScopeKind::HirTypeck,
             );
 
-            if let Some(prev) = self
-                .typeck_results
-                .concrete_opaque_types
-                .insert(opaque_type_key.def_id, hidden_type)
+            if let Some(prev) =
+                self.typeck_results.hidden_types.insert(opaque_type_key.def_id, hidden_type)
             {
-                let entry = &mut self
-                    .typeck_results
-                    .concrete_opaque_types
-                    .get_mut(&opaque_type_key.def_id)
-                    .unwrap();
+                let entry =
+                    &mut self.typeck_results.hidden_types.get_mut(&opaque_type_key.def_id).unwrap();
                 if prev.ty != hidden_type.ty {
                     if let Some(guar) = self.typeck_results.tainted_by_errors {
                         entry.ty = Ty::new_error(tcx, guar);
@@ -628,7 +622,7 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
 
         let recursive_opaques: Vec<_> = self
             .typeck_results
-            .concrete_opaque_types
+            .hidden_types
             .iter()
             .filter(|&(&def_id, hidden_ty)| {
                 hidden_ty
@@ -636,7 +630,7 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
                     .visit_with(&mut HasRecursiveOpaque {
                         def_id,
                         seen: Default::default(),
-                        opaques: &self.typeck_results.concrete_opaque_types,
+                        opaques: &self.typeck_results.hidden_types,
                         tcx,
                     })
                     .is_break()
@@ -651,7 +645,7 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
                 .with_code(E0720)
                 .emit();
             self.typeck_results
-                .concrete_opaque_types
+                .hidden_types
                 .insert(def_id, OpaqueHiddenType { span, ty: Ty::new_error(tcx, guar) });
         }
     }
diff --git a/compiler/rustc_index/src/idx.rs b/compiler/rustc_index/src/idx.rs
index 9cd7134659c..2fb2008f9a3 100644
--- a/compiler/rustc_index/src/idx.rs
+++ b/compiler/rustc_index/src/idx.rs
@@ -130,12 +130,6 @@ impl<I: Idx, T> IntoSliceIdx<I, [T]> for core::range::RangeFrom<I> {
 impl<I: Idx, T> IntoSliceIdx<I, [T]> for core::range::RangeInclusive<I> {
     type Output = core::range::RangeInclusive<usize>;
     #[inline]
-    #[cfg(bootstrap)]
-    fn into_slice_idx(self) -> Self::Output {
-        core::range::RangeInclusive { start: self.start.index(), end: self.end.index() }
-    }
-    #[inline]
-    #[cfg(not(bootstrap))]
     fn into_slice_idx(self) -> Self::Output {
         core::range::RangeInclusive { start: self.start.index(), last: self.last.index() }
     }
diff --git a/compiler/rustc_infer/src/infer/canonical/query_response.rs b/compiler/rustc_infer/src/infer/canonical/query_response.rs
index 5d1b4be9e57..b3959113d5d 100644
--- a/compiler/rustc_infer/src/infer/canonical/query_response.rs
+++ b/compiler/rustc_infer/src/infer/canonical/query_response.rs
@@ -85,11 +85,29 @@ impl<'tcx> InferCtxt<'tcx> {
     where
         T: Debug + TypeFoldable<TyCtxt<'tcx>>,
     {
+        // While we ignore region constraints and pending obligations,
+        // we do return constrained opaque types to avoid unconstrained
+        // inference variables in the response. This is important as we want
+        // to check that opaques in deref steps stay unconstrained.
+        //
+        // This doesn't handle the more general case for non-opaques as
+        // ambiguous `Projection` obligations have same the issue.
+        let opaque_types = if self.next_trait_solver() {
+            self.inner
+                .borrow_mut()
+                .opaque_type_storage
+                .iter_opaque_types()
+                .map(|(k, v)| (k, v.ty))
+                .collect()
+        } else {
+            vec![]
+        };
+
         self.canonicalize_response(QueryResponse {
             var_values: inference_vars,
             region_constraints: QueryRegionConstraints::default(),
             certainty: Certainty::Proven, // Ambiguities are OK!
-            opaque_types: vec![],
+            opaque_types,
             value: answer,
         })
     }
diff --git a/compiler/rustc_infer/src/infer/mod.rs b/compiler/rustc_infer/src/infer/mod.rs
index c9fc124d3bf..f3ebfde06ab 100644
--- a/compiler/rustc_infer/src/infer/mod.rs
+++ b/compiler/rustc_infer/src/infer/mod.rs
@@ -131,23 +131,6 @@ pub struct InferCtxtInner<'tcx> {
     /// `$0: 'static`. This will get checked later by regionck. (We
     /// can't generally check these things right away because we have
     /// to wait until types are resolved.)
-    ///
-    /// These are stored in a map keyed to the id of the innermost
-    /// enclosing fn body / static initializer expression. This is
-    /// because the location where the obligation was incurred can be
-    /// relevant with respect to which sublifetime assumptions are in
-    /// place. The reason that we store under the fn-id, and not
-    /// something more fine-grained, is so that it is easier for
-    /// regionck to be sure that it has found *all* the region
-    /// obligations (otherwise, it's easy to fail to walk to a
-    /// particular node-id).
-    ///
-    /// Before running `resolve_regions_and_report_errors`, the creator
-    /// of the inference context is expected to invoke
-    /// [`InferCtxt::process_registered_region_obligations`]
-    /// for each body-id in this map, which will process the
-    /// obligations within. This is expected to be done 'late enough'
-    /// that all type inference variables have been bound and so forth.
     region_obligations: Vec<TypeOutlivesConstraint<'tcx>>,
 
     /// The outlives bounds that we assume must hold about placeholders that
diff --git a/compiler/rustc_infer/src/infer/outlives/obligations.rs b/compiler/rustc_infer/src/infer/outlives/obligations.rs
index b989d419057..a640dcb1b4e 100644
--- a/compiler/rustc_infer/src/infer/outlives/obligations.rs
+++ b/compiler/rustc_infer/src/infer/outlives/obligations.rs
@@ -170,6 +170,10 @@ impl<'tcx> InferCtxt<'tcx> {
         std::mem::take(&mut self.inner.borrow_mut().region_obligations)
     }
 
+    pub fn clone_registered_region_obligations(&self) -> Vec<TypeOutlivesConstraint<'tcx>> {
+        self.inner.borrow().region_obligations.clone()
+    }
+
     pub fn register_region_assumption(&self, assumption: ty::ArgOutlivesPredicate<'tcx>) {
         let mut inner = self.inner.borrow_mut();
         inner.undo_log.push(UndoLog::PushRegionAssumption);
diff --git a/compiler/rustc_interface/src/passes.rs b/compiler/rustc_interface/src/passes.rs
index 761a5c80918..c1bba0b0197 100644
--- a/compiler/rustc_interface/src/passes.rs
+++ b/compiler/rustc_interface/src/passes.rs
@@ -1122,18 +1122,6 @@ fn run_required_analyses(tcx: TyCtxt<'_>) {
 
     sess.time("layout_testing", || layout_test::test_layout(tcx));
     sess.time("abi_testing", || abi_test::test_abi(tcx));
-
-    // If `-Zvalidate-mir` is set, we also want to compute the final MIR for each item
-    // (either its `mir_for_ctfe` or `optimized_mir`) since that helps uncover any bugs
-    // in MIR optimizations that may only be reachable through codegen, or other codepaths
-    // that requires the optimized/ctfe MIR, coroutine bodies, or evaluating consts.
-    if tcx.sess.opts.unstable_opts.validate_mir {
-        sess.time("ensuring_final_MIR_is_computable", || {
-            tcx.par_hir_body_owners(|def_id| {
-                tcx.instance_mir(ty::InstanceKind::Item(def_id.into()));
-            });
-        });
-    }
 }
 
 /// Runs the type-checking, region checking and other miscellaneous analysis
@@ -1199,6 +1187,20 @@ fn analysis(tcx: TyCtxt<'_>, (): ()) {
         // we will fail to emit overlap diagnostics. Thus we invoke it here unconditionally.
         let _ = tcx.all_diagnostic_items(());
     });
+
+    // If `-Zvalidate-mir` is set, we also want to compute the final MIR for each item
+    // (either its `mir_for_ctfe` or `optimized_mir`) since that helps uncover any bugs
+    // in MIR optimizations that may only be reachable through codegen, or other codepaths
+    // that requires the optimized/ctfe MIR, coroutine bodies, or evaluating consts.
+    // Nevertheless, wait after type checking is finished, as optimizing code that does not
+    // type-check is very prone to ICEs.
+    if tcx.sess.opts.unstable_opts.validate_mir {
+        sess.time("ensuring_final_MIR_is_computable", || {
+            tcx.par_hir_body_owners(|def_id| {
+                tcx.instance_mir(ty::InstanceKind::Item(def_id.into()));
+            });
+        });
+    }
 }
 
 /// Runs the codegen backend, after which the AST and analysis can
diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs
index 800f5efee41..7e5186db4ea 100644
--- a/compiler/rustc_interface/src/tests.rs
+++ b/compiler/rustc_interface/src/tests.rs
@@ -765,7 +765,7 @@ fn test_unstable_options_tracking_hash() {
     tracked!(allow_features, Some(vec![String::from("lang_items")]));
     tracked!(always_encode_mir, true);
     tracked!(assume_incomplete_release, true);
-    tracked!(autodiff, vec![AutoDiff::Enable]);
+    tracked!(autodiff, vec![AutoDiff::Enable, AutoDiff::NoTT]);
     tracked!(binary_dep_depinfo, true);
     tracked!(box_noalias, false);
     tracked!(
diff --git a/compiler/rustc_interface/src/util.rs b/compiler/rustc_interface/src/util.rs
index 76ccd12797e..be2fd0787b9 100644
--- a/compiler/rustc_interface/src/util.rs
+++ b/compiler/rustc_interface/src/util.rs
@@ -1,3 +1,4 @@
+use std::any::Any;
 use std::env::consts::{DLL_PREFIX, DLL_SUFFIX};
 use std::path::{Path, PathBuf};
 use std::sync::atomic::{AtomicBool, Ordering};
@@ -6,13 +7,20 @@ use std::{env, thread};
 
 use rustc_ast as ast;
 use rustc_attr_parsing::{ShouldEmit, validate_attr};
+use rustc_codegen_ssa::back::archive::ArArchiveBuilderBuilder;
+use rustc_codegen_ssa::back::link::link_binary;
 use rustc_codegen_ssa::traits::CodegenBackend;
+use rustc_codegen_ssa::{CodegenResults, CrateInfo};
+use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::jobserver::Proxy;
 use rustc_data_structures::sync;
 use rustc_errors::LintBuffer;
-use rustc_metadata::{DylibError, load_symbol_from_dylib};
-use rustc_middle::ty::CurrentGcx;
-use rustc_session::config::{Cfg, OutFileName, OutputFilenames, OutputTypes, Sysroot, host_tuple};
+use rustc_metadata::{DylibError, EncodedMetadata, load_symbol_from_dylib};
+use rustc_middle::dep_graph::{WorkProduct, WorkProductId};
+use rustc_middle::ty::{CurrentGcx, TyCtxt};
+use rustc_session::config::{
+    Cfg, CrateType, OutFileName, OutputFilenames, OutputTypes, Sysroot, host_tuple,
+};
 use rustc_session::output::{CRATE_TYPES, categorize_crate_type};
 use rustc_session::{EarlyDiagCtxt, Session, filesearch, lint};
 use rustc_span::edit_distance::find_best_match_for_name;
@@ -316,12 +324,13 @@ pub fn get_codegen_backend(
         let backend = backend_name
             .or(target.default_codegen_backend.as_deref())
             .or(option_env!("CFG_DEFAULT_CODEGEN_BACKEND"))
-            .unwrap_or("llvm");
+            .unwrap_or("dummy");
 
         match backend {
             filename if filename.contains('.') => {
                 load_backend_from_dylib(early_dcx, filename.as_ref())
             }
+            "dummy" => || Box::new(DummyCodegenBackend),
             #[cfg(feature = "llvm")]
             "llvm" => rustc_codegen_llvm::LlvmCodegenBackend::new,
             backend_name => get_codegen_sysroot(early_dcx, sysroot, backend_name),
@@ -334,6 +343,63 @@ pub fn get_codegen_backend(
     unsafe { load() }
 }
 
+struct DummyCodegenBackend;
+
+impl CodegenBackend for DummyCodegenBackend {
+    fn locale_resource(&self) -> &'static str {
+        ""
+    }
+
+    fn name(&self) -> &'static str {
+        "dummy"
+    }
+
+    fn codegen_crate<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Box<dyn Any> {
+        Box::new(CodegenResults {
+            modules: vec![],
+            allocator_module: None,
+            crate_info: CrateInfo::new(tcx, String::new()),
+        })
+    }
+
+    fn join_codegen(
+        &self,
+        ongoing_codegen: Box<dyn Any>,
+        _sess: &Session,
+        _outputs: &OutputFilenames,
+    ) -> (CodegenResults, FxIndexMap<WorkProductId, WorkProduct>) {
+        (*ongoing_codegen.downcast().unwrap(), FxIndexMap::default())
+    }
+
+    fn link(
+        &self,
+        sess: &Session,
+        codegen_results: CodegenResults,
+        metadata: EncodedMetadata,
+        outputs: &OutputFilenames,
+    ) {
+        // JUSTIFICATION: TyCtxt no longer available here
+        #[allow(rustc::bad_opt_access)]
+        if sess.opts.crate_types.iter().any(|&crate_type| crate_type != CrateType::Rlib) {
+            #[allow(rustc::untranslatable_diagnostic)]
+            #[allow(rustc::diagnostic_outside_of_impl)]
+            sess.dcx().fatal(format!(
+                "crate type {} not supported by the dummy codegen backend",
+                sess.opts.crate_types[0],
+            ));
+        }
+
+        link_binary(
+            sess,
+            &ArArchiveBuilderBuilder,
+            codegen_results,
+            metadata,
+            outputs,
+            self.name(),
+        );
+    }
+}
+
 // This is used for rustdoc, but it uses similar machinery to codegen backend
 // loading, so we leave the code here. It is potentially useful for other tools
 // that want to invoke the rustc binary while linking to rustc as well.
@@ -542,6 +608,7 @@ pub fn build_output_filenames(attrs: &[ast::Attribute], sess: &Session) -> Outpu
                 stem,
                 None,
                 sess.io.temps_dir.clone(),
+                sess.opts.unstable_opts.split_dwarf_out_dir.clone(),
                 sess.opts.cg.extra_filename.clone(),
                 sess.opts.output_types.clone(),
             )
@@ -571,6 +638,7 @@ pub fn build_output_filenames(attrs: &[ast::Attribute], sess: &Session) -> Outpu
                 out_filestem,
                 ofile,
                 sess.io.temps_dir.clone(),
+                sess.opts.unstable_opts.split_dwarf_out_dir.clone(),
                 sess.opts.cg.extra_filename.clone(),
                 sess.opts.output_types.clone(),
             )
diff --git a/compiler/rustc_lint_defs/src/builtin.rs b/compiler/rustc_lint_defs/src/builtin.rs
index 3d0974d5d28..939f3d088b1 100644
--- a/compiler/rustc_lint_defs/src/builtin.rs
+++ b/compiler/rustc_lint_defs/src/builtin.rs
@@ -2309,10 +2309,10 @@ declare_lint! {
     /// ### Example
     ///
     /// ```rust
-    /// #![cfg_attr(not(bootstrap), feature(sanitize))]
+    /// #![feature(sanitize)]
     ///
     /// #[inline(always)]
-    /// #[cfg_attr(not(bootstrap), sanitize(address = "off"))]
+    /// #[sanitize(address = "off")]
     /// fn x() {}
     ///
     /// fn main() {
@@ -4837,16 +4837,13 @@ declare_lint! {
     ///
     /// ### Example
     ///
-    #[cfg_attr(not(bootstrap), doc = "```rust,compile_fail")]
-    #[cfg_attr(bootstrap, doc = "```rust")]
+    /// ```rust,compile_fail
     /// #![doc = in_root!()]
     ///
     /// macro_rules! in_root { () => { "" } }
     ///
     /// fn main() {}
-    #[cfg_attr(not(bootstrap), doc = "```")]
-    #[cfg_attr(bootstrap, doc = "```")]
-    // ^ Needed to avoid tidy warning about odd number of backticks
+    /// ```
     ///
     /// {{produces}}
     ///
diff --git a/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp
index 013d68fa3e4..2e9fd6754f1 100644
--- a/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp
@@ -569,25 +569,43 @@ extern "C" LLVMRustResult LLVMRustOptimize(
   }
 
   std::optional<PGOOptions> PGOOpt;
+#if LLVM_VERSION_LT(22, 0)
   auto FS = vfs::getRealFileSystem();
+#endif
   if (PGOGenPath) {
     assert(!PGOUsePath && !PGOSampleUsePath);
     PGOOpt = PGOOptions(
+#if LLVM_VERSION_GE(22, 0)
+        PGOGenPath, "", "", "", PGOOptions::IRInstr, PGOOptions::NoCSAction,
+#else
         PGOGenPath, "", "", "", FS, PGOOptions::IRInstr, PGOOptions::NoCSAction,
+#endif
         PGOOptions::ColdFuncOpt::Default, DebugInfoForProfiling);
   } else if (PGOUsePath) {
     assert(!PGOSampleUsePath);
     PGOOpt = PGOOptions(
+#if LLVM_VERSION_GE(22, 0)
+        PGOUsePath, "", "", "", PGOOptions::IRUse, PGOOptions::NoCSAction,
+#else
         PGOUsePath, "", "", "", FS, PGOOptions::IRUse, PGOOptions::NoCSAction,
+#endif
         PGOOptions::ColdFuncOpt::Default, DebugInfoForProfiling);
   } else if (PGOSampleUsePath) {
     PGOOpt =
+#if LLVM_VERSION_GE(22, 0)
+        PGOOptions(PGOSampleUsePath, "", "", "", PGOOptions::SampleUse,
+#else
         PGOOptions(PGOSampleUsePath, "", "", "", FS, PGOOptions::SampleUse,
+#endif
                    PGOOptions::NoCSAction, PGOOptions::ColdFuncOpt::Default,
                    DebugInfoForProfiling);
   } else if (DebugInfoForProfiling) {
     PGOOpt = PGOOptions(
+#if LLVM_VERSION_GE(22, 0)
+        "", "", "", "", PGOOptions::NoAction, PGOOptions::NoCSAction,
+#else
         "", "", "", "", FS, PGOOptions::NoAction, PGOOptions::NoCSAction,
+#endif
         PGOOptions::ColdFuncOpt::Default, DebugInfoForProfiling);
   }
 
diff --git a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
index 9953f5e1731..2b83ea24ac6 100644
--- a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
@@ -990,14 +990,6 @@ extern "C" void LLVMRustGlobalAddMetadata(LLVMValueRef Global, unsigned Kind,
   unwrap<GlobalObject>(Global)->addMetadata(Kind, *unwrap<MDNode>(MD));
 }
 
-extern "C" LLVMDIBuilderRef LLVMRustDIBuilderCreate(LLVMModuleRef M) {
-  return wrap(new DIBuilder(*unwrap(M)));
-}
-
-extern "C" void LLVMRustDIBuilderDispose(LLVMDIBuilderRef Builder) {
-  delete unwrap(Builder);
-}
-
 extern "C" LLVMMetadataRef LLVMRustDIBuilderCreateCompileUnit(
     LLVMDIBuilderRef Builder, unsigned Lang, LLVMMetadataRef FileRef,
     const char *Producer, size_t ProducerLen, bool isOptimized,
@@ -1129,51 +1121,6 @@ extern "C" LLVMMetadataRef LLVMRustDIBuilderCreateStaticVariable(
   return wrap(VarExpr);
 }
 
-extern "C" LLVMMetadataRef LLVMRustDIBuilderCreateVariable(
-    LLVMDIBuilderRef Builder, unsigned Tag, LLVMMetadataRef Scope,
-    const char *Name, size_t NameLen, LLVMMetadataRef File, unsigned LineNo,
-    LLVMMetadataRef Ty, bool AlwaysPreserve, LLVMDIFlags Flags, unsigned ArgNo,
-    uint32_t AlignInBits) {
-  if (Tag == 0x100) { // DW_TAG_auto_variable
-    return wrap(unwrap(Builder)->createAutoVariable(
-        unwrapDI<DIDescriptor>(Scope), StringRef(Name, NameLen),
-        unwrapDI<DIFile>(File), LineNo, unwrapDI<DIType>(Ty), AlwaysPreserve,
-        fromRust(Flags), AlignInBits));
-  } else {
-    return wrap(unwrap(Builder)->createParameterVariable(
-        unwrapDI<DIDescriptor>(Scope), StringRef(Name, NameLen), ArgNo,
-        unwrapDI<DIFile>(File), LineNo, unwrapDI<DIType>(Ty), AlwaysPreserve,
-        fromRust(Flags)));
-  }
-}
-
-extern "C" LLVMMetadataRef
-LLVMRustDIBuilderGetOrCreateSubrange(LLVMDIBuilderRef Builder, int64_t Lo,
-                                     int64_t Count) {
-  return wrap(unwrap(Builder)->getOrCreateSubrange(Lo, Count));
-}
-
-extern "C" LLVMMetadataRef
-LLVMRustDIBuilderGetOrCreateArray(LLVMDIBuilderRef Builder,
-                                  LLVMMetadataRef *Ptr, unsigned Count) {
-  Metadata **DataValue = unwrap(Ptr);
-  return wrap(unwrap(Builder)
-                  ->getOrCreateArray(ArrayRef<Metadata *>(DataValue, Count))
-                  .get());
-}
-
-extern "C" void
-LLVMRustDIBuilderInsertDeclareAtEnd(LLVMDIBuilderRef Builder, LLVMValueRef V,
-                                    LLVMMetadataRef VarInfo, uint64_t *AddrOps,
-                                    unsigned AddrOpsCount, LLVMMetadataRef DL,
-                                    LLVMBasicBlockRef InsertAtEnd) {
-  unwrap(Builder)->insertDeclare(
-      unwrap(V), unwrap<DILocalVariable>(VarInfo),
-      unwrap(Builder)->createExpression(
-          llvm::ArrayRef<uint64_t>(AddrOps, AddrOpsCount)),
-      DebugLoc(cast<MDNode>(unwrap(DL))), unwrap(InsertAtEnd));
-}
-
 extern "C" LLVMMetadataRef
 LLVMRustDIBuilderCreateEnumerator(LLVMDIBuilderRef Builder, const char *Name,
                                   size_t NameLen, const uint64_t Value[2],
@@ -1865,3 +1812,67 @@ extern "C" void LLVMRustSetNoSanitizeHWAddress(LLVMValueRef Global) {
   MD.NoHWAddress = true;
   GV.setSanitizerMetadata(MD);
 }
+
+#ifdef ENZYME
+extern "C" {
+extern llvm::cl::opt<unsigned> EnzymeMaxTypeDepth;
+}
+
+extern "C" size_t LLVMRustEnzymeGetMaxTypeDepth() { return EnzymeMaxTypeDepth; }
+#else
+extern "C" size_t LLVMRustEnzymeGetMaxTypeDepth() {
+  return 6; // Default fallback depth
+}
+#endif
+
+// Statically assert that the fixed metadata kind IDs declared in
+// `metadata_kind.rs` match the ones actually used by LLVM.
+#define FIXED_MD_KIND(VARIANT, VALUE)                                          \
+  static_assert(::llvm::LLVMContext::VARIANT == VALUE);
+// Must be kept in sync with the corresponding list in `metadata_kind.rs`.
+FIXED_MD_KIND(MD_dbg, 0)
+FIXED_MD_KIND(MD_tbaa, 1)
+FIXED_MD_KIND(MD_prof, 2)
+FIXED_MD_KIND(MD_fpmath, 3)
+FIXED_MD_KIND(MD_range, 4)
+FIXED_MD_KIND(MD_tbaa_struct, 5)
+FIXED_MD_KIND(MD_invariant_load, 6)
+FIXED_MD_KIND(MD_alias_scope, 7)
+FIXED_MD_KIND(MD_noalias, 8)
+FIXED_MD_KIND(MD_nontemporal, 9)
+FIXED_MD_KIND(MD_mem_parallel_loop_access, 10)
+FIXED_MD_KIND(MD_nonnull, 11)
+FIXED_MD_KIND(MD_dereferenceable, 12)
+FIXED_MD_KIND(MD_dereferenceable_or_null, 13)
+FIXED_MD_KIND(MD_make_implicit, 14)
+FIXED_MD_KIND(MD_unpredictable, 15)
+FIXED_MD_KIND(MD_invariant_group, 16)
+FIXED_MD_KIND(MD_align, 17)
+FIXED_MD_KIND(MD_loop, 18)
+FIXED_MD_KIND(MD_type, 19)
+FIXED_MD_KIND(MD_section_prefix, 20)
+FIXED_MD_KIND(MD_absolute_symbol, 21)
+FIXED_MD_KIND(MD_associated, 22)
+FIXED_MD_KIND(MD_callees, 23)
+FIXED_MD_KIND(MD_irr_loop, 24)
+FIXED_MD_KIND(MD_access_group, 25)
+FIXED_MD_KIND(MD_callback, 26)
+FIXED_MD_KIND(MD_preserve_access_index, 27)
+FIXED_MD_KIND(MD_vcall_visibility, 28)
+FIXED_MD_KIND(MD_noundef, 29)
+FIXED_MD_KIND(MD_annotation, 30)
+FIXED_MD_KIND(MD_nosanitize, 31)
+FIXED_MD_KIND(MD_func_sanitize, 32)
+FIXED_MD_KIND(MD_exclude, 33)
+FIXED_MD_KIND(MD_memprof, 34)
+FIXED_MD_KIND(MD_callsite, 35)
+FIXED_MD_KIND(MD_kcfi_type, 36)
+FIXED_MD_KIND(MD_pcsections, 37)
+FIXED_MD_KIND(MD_DIAssignID, 38)
+FIXED_MD_KIND(MD_coro_outside_frame, 39)
+FIXED_MD_KIND(MD_mmra, 40)
+FIXED_MD_KIND(MD_noalias_addrspace, 41)
+// If some fixed metadata kinds are not present and consistent in all supported
+// LLVM versions, it's fine to omit them from this list; in that case Rust-side
+// code cannot declare them as fixed IDs and must look them up by name instead.
+#undef FIXED_MD_KIND
diff --git a/compiler/rustc_macros/src/query.rs b/compiler/rustc_macros/src/query.rs
index 5821ffa3a30..5d32950875a 100644
--- a/compiler/rustc_macros/src/query.rs
+++ b/compiler/rustc_macros/src/query.rs
@@ -5,7 +5,7 @@ use syn::punctuated::Punctuated;
 use syn::spanned::Spanned;
 use syn::{
     AttrStyle, Attribute, Block, Error, Expr, Ident, Pat, ReturnType, Token, Type, braced,
-    parenthesized, parse_macro_input, parse_quote, token,
+    parenthesized, parse_macro_input, token,
 };
 
 mod kw {
diff --git a/compiler/rustc_metadata/src/rmeta/decoder.rs b/compiler/rustc_metadata/src/rmeta/decoder.rs
index 0c8d1f32e99..b895feb9062 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder.rs
@@ -1555,7 +1555,7 @@ impl<'a> CrateMetadataRef<'a> {
     }
 
     #[inline]
-    fn def_path_hash_to_def_index(self, hash: DefPathHash) -> DefIndex {
+    fn def_path_hash_to_def_index(self, hash: DefPathHash) -> Option<DefIndex> {
         self.def_path_hash_map.def_path_hash_to_def_index(&hash)
     }
 
diff --git a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
index 11fef3be5d0..df3add316ec 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
@@ -691,8 +691,8 @@ fn provide_cstore_hooks(providers: &mut Providers) {
             .get(&stable_crate_id)
             .unwrap_or_else(|| bug!("uninterned StableCrateId: {stable_crate_id:?}"));
         assert_ne!(cnum, LOCAL_CRATE);
-        let def_index = cstore.get_crate_data(cnum).def_path_hash_to_def_index(hash);
-        DefId { krate: cnum, index: def_index }
+        let def_index = cstore.get_crate_data(cnum).def_path_hash_to_def_index(hash)?;
+        Some(DefId { krate: cnum, index: def_index })
     };
 
     providers.hooks.expn_hash_to_expn_id = |tcx, cnum, index_guess, hash| {
diff --git a/compiler/rustc_metadata/src/rmeta/def_path_hash_map.rs b/compiler/rustc_metadata/src/rmeta/def_path_hash_map.rs
index f3917b55782..a17b3e1047d 100644
--- a/compiler/rustc_metadata/src/rmeta/def_path_hash_map.rs
+++ b/compiler/rustc_metadata/src/rmeta/def_path_hash_map.rs
@@ -12,11 +12,12 @@ pub(crate) enum DefPathHashMapRef<'tcx> {
 
 impl DefPathHashMapRef<'_> {
     #[inline]
-    pub(crate) fn def_path_hash_to_def_index(&self, def_path_hash: &DefPathHash) -> DefIndex {
+    pub(crate) fn def_path_hash_to_def_index(
+        &self,
+        def_path_hash: &DefPathHash,
+    ) -> Option<DefIndex> {
         match *self {
-            DefPathHashMapRef::OwnedFromMetadata(ref map) => {
-                map.get(&def_path_hash.local_hash()).unwrap()
-            }
+            DefPathHashMapRef::OwnedFromMetadata(ref map) => map.get(&def_path_hash.local_hash()),
             DefPathHashMapRef::BorrowedFromTcx(_) => {
                 panic!("DefPathHashMap::BorrowedFromTcx variant only exists for serialization")
             }
diff --git a/compiler/rustc_middle/src/arena.rs b/compiler/rustc_middle/src/arena.rs
index 52fbe19c9f2..feaad5bb96e 100644
--- a/compiler/rustc_middle/src/arena.rs
+++ b/compiler/rustc_middle/src/arena.rs
@@ -27,7 +27,7 @@ macro_rules! arena_types {
                     rustc_middle::mir::Body<'tcx>
                 >,
             [decode] typeck_results: rustc_middle::ty::TypeckResults<'tcx>,
-            [decode] borrowck_result: rustc_middle::mir::ConcreteOpaqueTypes<'tcx>,
+            [decode] borrowck_result: rustc_middle::mir::DefinitionSiteHiddenTypes<'tcx>,
             [] resolver: rustc_data_structures::steal::Steal<(
                 rustc_middle::ty::ResolverAstLowering,
                 std::sync::Arc<rustc_ast::Crate>,
@@ -109,7 +109,6 @@ macro_rules! arena_types {
                     rustc_middle::ty::EarlyBinder<'tcx, rustc_middle::ty::Ty<'tcx>>
                 >,
             [] external_constraints: rustc_middle::traits::solve::ExternalConstraintsData<rustc_middle::ty::TyCtxt<'tcx>>,
-            [] predefined_opaques_in_body: rustc_middle::traits::solve::PredefinedOpaquesData<rustc_middle::ty::TyCtxt<'tcx>>,
             [decode] doc_link_resolutions: rustc_hir::def::DocLinkResMap,
             [] stripped_cfg_items: rustc_hir::attrs::StrippedCfgItem,
             [] mod_child: rustc_middle::metadata::ModChild,
diff --git a/compiler/rustc_middle/src/error.rs b/compiler/rustc_middle/src/error.rs
index 0be26712b9c..3ff9eea8cc4 100644
--- a/compiler/rustc_middle/src/error.rs
+++ b/compiler/rustc_middle/src/error.rs
@@ -37,7 +37,6 @@ pub(crate) struct OpaqueHiddenTypeMismatch<'tcx> {
     pub sub: TypeMismatchReason,
 }
 
-// FIXME(autodiff): I should get used somewhere
 #[derive(Diagnostic)]
 #[diag(middle_unsupported_union)]
 pub struct UnsupportedUnion {
diff --git a/compiler/rustc_middle/src/hooks/mod.rs b/compiler/rustc_middle/src/hooks/mod.rs
index 9d2f0a45237..dc6a3334a4c 100644
--- a/compiler/rustc_middle/src/hooks/mod.rs
+++ b/compiler/rustc_middle/src/hooks/mod.rs
@@ -77,7 +77,7 @@ declare_hooks! {
     /// session, if it still exists. This is used during incremental compilation to
     /// turn a deserialized `DefPathHash` into its current `DefId`.
     /// Will fetch a DefId from a DefPathHash for a foreign crate.
-    hook def_path_hash_to_def_id_extern(hash: DefPathHash, stable_crate_id: StableCrateId) -> DefId;
+    hook def_path_hash_to_def_id_extern(hash: DefPathHash, stable_crate_id: StableCrateId) -> Option<DefId>;
 
     /// Returns `true` if we should codegen an instance in the local crate, or returns `false` if we
     /// can just link to the upstream crate and therefore don't need a mono item.
diff --git a/compiler/rustc_middle/src/lib.rs b/compiler/rustc_middle/src/lib.rs
index 5023b2740ef..754a258eef9 100644
--- a/compiler/rustc_middle/src/lib.rs
+++ b/compiler/rustc_middle/src/lib.rs
@@ -29,7 +29,6 @@
 #![allow(rustc::diagnostic_outside_of_impl)]
 #![allow(rustc::direct_use_of_rustc_type_ir)]
 #![allow(rustc::untranslatable_diagnostic)]
-#![cfg_attr(bootstrap, feature(round_char_boundary))]
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![doc(rust_logo)]
 #![feature(allocator_api)]
diff --git a/compiler/rustc_middle/src/middle/debugger_visualizer.rs b/compiler/rustc_middle/src/middle/debugger_visualizer.rs
index 5a811321f58..a7f0095dcdf 100644
--- a/compiler/rustc_middle/src/middle/debugger_visualizer.rs
+++ b/compiler/rustc_middle/src/middle/debugger_visualizer.rs
@@ -1,15 +1,9 @@
 use std::path::PathBuf;
 use std::sync::Arc;
 
+use rustc_hir::attrs::DebuggerVisualizerType;
 use rustc_macros::{Decodable, Encodable, HashStable};
 
-#[derive(HashStable)]
-#[derive(Copy, PartialEq, PartialOrd, Clone, Ord, Eq, Hash, Debug, Encodable, Decodable)]
-pub enum DebuggerVisualizerType {
-    Natvis,
-    GdbPrettyPrinter,
-}
-
 /// A single debugger visualizer file.
 #[derive(HashStable)]
 #[derive(Clone, Debug, Hash, PartialEq, Eq, PartialOrd, Ord, Encodable, Decodable)]
diff --git a/compiler/rustc_middle/src/mir/query.rs b/compiler/rustc_middle/src/mir/query.rs
index a509c40c89c..2e6c9f207e2 100644
--- a/compiler/rustc_middle/src/mir/query.rs
+++ b/compiler/rustc_middle/src/mir/query.rs
@@ -84,11 +84,10 @@ impl Debug for CoroutineLayout<'_> {
     }
 }
 
-/// All the opaque types that are restricted to concrete types
-/// by this function. Unlike the value in `TypeckResults`, this has
-/// unerased regions.
+/// All the opaque types that have had their hidden type fully computed.
+/// Unlike the value in `TypeckResults`, this has unerased regions.
 #[derive(Default, Debug, TyEncodable, TyDecodable, HashStable)]
-pub struct ConcreteOpaqueTypes<'tcx>(pub FxIndexMap<LocalDefId, OpaqueHiddenType<'tcx>>);
+pub struct DefinitionSiteHiddenTypes<'tcx>(pub FxIndexMap<LocalDefId, OpaqueHiddenType<'tcx>>);
 
 /// The result of the `mir_const_qualif` query.
 ///
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index 0e645a3aae4..895c8c0295a 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -124,7 +124,7 @@ use crate::query::plumbing::{
 };
 use crate::traits::query::{
     CanonicalAliasGoal, CanonicalDropckOutlivesGoal, CanonicalImpliedOutlivesBoundsGoal,
-    CanonicalPredicateGoal, CanonicalTyGoal, CanonicalTypeOpAscribeUserTypeGoal,
+    CanonicalMethodAutoderefStepsGoal, CanonicalPredicateGoal, CanonicalTypeOpAscribeUserTypeGoal,
     CanonicalTypeOpNormalizeGoal, CanonicalTypeOpProvePredicateGoal, DropckConstraint,
     DropckOutlivesResult, MethodAutoderefStepsResult, NoSolution, NormalizationResult,
     OutlivesBound,
@@ -1244,7 +1244,7 @@ rustc_queries! {
 
     /// Borrow-checks the given typeck root, e.g. functions, const/static items,
     /// and its children, e.g. closures, inline consts.
-    query mir_borrowck(key: LocalDefId) -> Result<&'tcx mir::ConcreteOpaqueTypes<'tcx>, ErrorGuaranteed> {
+    query mir_borrowck(key: LocalDefId) -> Result<&'tcx mir::DefinitionSiteHiddenTypes<'tcx>, ErrorGuaranteed> {
         desc { |tcx| "borrow-checking `{}`", tcx.def_path_str(key) }
     }
 
@@ -2559,9 +2559,9 @@ rustc_queries! {
     }
 
     query method_autoderef_steps(
-        goal: CanonicalTyGoal<'tcx>
+        goal: CanonicalMethodAutoderefStepsGoal<'tcx>
     ) -> MethodAutoderefStepsResult<'tcx> {
-        desc { "computing autoderef types for `{}`", goal.canonical.value.value }
+        desc { "computing autoderef types for `{}`", goal.canonical.value.value.self_ty }
     }
 
     /// Used by `-Znext-solver` to compute proof trees.
diff --git a/compiler/rustc_middle/src/traits/query.rs b/compiler/rustc_middle/src/traits/query.rs
index 3f6faa1a572..c5cd7c54e4e 100644
--- a/compiler/rustc_middle/src/traits/query.rs
+++ b/compiler/rustc_middle/src/traits/query.rs
@@ -10,6 +10,7 @@ use rustc_span::Span;
 
 use crate::error::DropCheckOverflow;
 use crate::infer::canonical::{Canonical, CanonicalQueryInput, QueryResponse};
+use crate::traits::solve;
 pub use crate::traits::solve::NoSolution;
 use crate::ty::{self, GenericArg, Ty, TyCtxt};
 
@@ -67,7 +68,16 @@ pub mod type_op {
 pub type CanonicalAliasGoal<'tcx> =
     CanonicalQueryInput<'tcx, ty::ParamEnvAnd<'tcx, ty::AliasTy<'tcx>>>;
 
-pub type CanonicalTyGoal<'tcx> = CanonicalQueryInput<'tcx, ty::ParamEnvAnd<'tcx, Ty<'tcx>>>;
+pub type CanonicalMethodAutoderefStepsGoal<'tcx> =
+    CanonicalQueryInput<'tcx, ty::ParamEnvAnd<'tcx, MethodAutoderefSteps<'tcx>>>;
+#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, HashStable, TypeFoldable, TypeVisitable)]
+pub struct MethodAutoderefSteps<'tcx> {
+    /// The list of opaque types currently in the storage.
+    ///
+    /// Only used by the new solver for now.
+    pub predefined_opaques_in_body: solve::PredefinedOpaques<'tcx>,
+    pub self_ty: Ty<'tcx>,
+}
 
 pub type CanonicalPredicateGoal<'tcx> =
     CanonicalQueryInput<'tcx, ty::ParamEnvAnd<'tcx, ty::Predicate<'tcx>>>;
@@ -144,6 +154,7 @@ impl<'tcx> FromIterator<DropckConstraint<'tcx>> for DropckConstraint<'tcx> {
 #[derive(Debug, HashStable)]
 pub struct CandidateStep<'tcx> {
     pub self_ty: Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>,
+    pub self_ty_is_opaque: bool,
     pub autoderefs: usize,
     /// `true` if the type results from a dereference of a raw pointer.
     /// when assembling candidates, we include these steps, but not when
diff --git a/compiler/rustc_middle/src/traits/solve.rs b/compiler/rustc_middle/src/traits/solve.rs
index ef5223de0e8..3343f270333 100644
--- a/compiler/rustc_middle/src/traits/solve.rs
+++ b/compiler/rustc_middle/src/traits/solve.rs
@@ -4,7 +4,7 @@ use rustc_type_ir as ir;
 pub use rustc_type_ir::solve::*;
 
 use crate::ty::{
-    self, FallibleTypeFolder, TyCtxt, TypeFoldable, TypeFolder, TypeVisitable, TypeVisitor,
+    self, FallibleTypeFolder, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeVisitable, TypeVisitor,
     try_visit,
 };
 
@@ -15,16 +15,7 @@ pub type CandidateSource<'tcx> = ir::solve::CandidateSource<TyCtxt<'tcx>>;
 pub type CanonicalInput<'tcx, P = ty::Predicate<'tcx>> = ir::solve::CanonicalInput<TyCtxt<'tcx>, P>;
 pub type CanonicalResponse<'tcx> = ir::solve::CanonicalResponse<TyCtxt<'tcx>>;
 
-#[derive(Debug, PartialEq, Eq, Copy, Clone, Hash, HashStable)]
-pub struct PredefinedOpaques<'tcx>(pub(crate) Interned<'tcx, PredefinedOpaquesData<TyCtxt<'tcx>>>);
-
-impl<'tcx> std::ops::Deref for PredefinedOpaques<'tcx> {
-    type Target = PredefinedOpaquesData<TyCtxt<'tcx>>;
-
-    fn deref(&self) -> &Self::Target {
-        &self.0
-    }
-}
+pub type PredefinedOpaques<'tcx> = &'tcx ty::List<(ty::OpaqueTypeKey<'tcx>, Ty<'tcx>)>;
 
 #[derive(Debug, PartialEq, Eq, Copy, Clone, Hash, HashStable)]
 pub struct ExternalConstraints<'tcx>(
@@ -93,35 +84,3 @@ impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for ExternalConstraints<'tcx> {
         self.normalization_nested_goals.visit_with(visitor)
     }
 }
-
-// FIXME: Having to clone `region_constraints` for folding feels bad and
-// probably isn't great wrt performance.
-//
-// Not sure how to fix this, maybe we should also intern `opaque_types` and
-// `region_constraints` here or something.
-impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for PredefinedOpaques<'tcx> {
-    fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
-        self,
-        folder: &mut F,
-    ) -> Result<Self, F::Error> {
-        Ok(FallibleTypeFolder::cx(folder).mk_predefined_opaques_in_body(PredefinedOpaquesData {
-            opaque_types: self
-                .opaque_types
-                .iter()
-                .map(|opaque| opaque.try_fold_with(folder))
-                .collect::<Result<_, F::Error>>()?,
-        }))
-    }
-
-    fn fold_with<F: TypeFolder<TyCtxt<'tcx>>>(self, folder: &mut F) -> Self {
-        TypeFolder::cx(folder).mk_predefined_opaques_in_body(PredefinedOpaquesData {
-            opaque_types: self.opaque_types.iter().map(|opaque| opaque.fold_with(folder)).collect(),
-        })
-    }
-}
-
-impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for PredefinedOpaques<'tcx> {
-    fn visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(&self, visitor: &mut V) -> V::Result {
-        self.opaque_types.visit_with(visitor)
-    }
-}
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 7d3e2c9965d..fe3fa024cd5 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -75,7 +75,7 @@ use crate::thir::Thir;
 use crate::traits;
 use crate::traits::solve::{
     self, CanonicalInput, ExternalConstraints, ExternalConstraintsData, PredefinedOpaques,
-    PredefinedOpaquesData, QueryResult, inspect,
+    QueryResult, inspect,
 };
 use crate::ty::predicate::ExistentialPredicateStableCmpExt as _;
 use crate::ty::{
@@ -116,7 +116,7 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
 
     fn mk_predefined_opaques_in_body(
         self,
-        data: PredefinedOpaquesData<Self>,
+        data: &[(ty::OpaqueTypeKey<'tcx>, Ty<'tcx>)],
     ) -> Self::PredefinedOpaques {
         self.mk_predefined_opaques_in_body(data)
     }
@@ -941,7 +941,7 @@ pub struct CtxtInterners<'tcx> {
     layout: InternedSet<'tcx, LayoutData<FieldIdx, VariantIdx>>,
     adt_def: InternedSet<'tcx, AdtDefData>,
     external_constraints: InternedSet<'tcx, ExternalConstraintsData<TyCtxt<'tcx>>>,
-    predefined_opaques_in_body: InternedSet<'tcx, PredefinedOpaquesData<TyCtxt<'tcx>>>,
+    predefined_opaques_in_body: InternedSet<'tcx, List<(ty::OpaqueTypeKey<'tcx>, Ty<'tcx>)>>,
     fields: InternedSet<'tcx, List<FieldIdx>>,
     local_def_ids: InternedSet<'tcx, List<LocalDefId>>,
     captures: InternedSet<'tcx, List<&'tcx ty::CapturedPlace<'tcx>>>,
@@ -2012,7 +2012,7 @@ impl<'tcx> TyCtxt<'tcx> {
         if stable_crate_id == self.stable_crate_id(LOCAL_CRATE) {
             Some(self.untracked.definitions.read().local_def_path_hash_to_def_id(hash)?.to_def_id())
         } else {
-            Some(self.def_path_hash_to_def_id_extern(hash, stable_crate_id))
+            self.def_path_hash_to_def_id_extern(hash, stable_crate_id)
         }
     }
 
@@ -2748,8 +2748,6 @@ direct_interners! {
     adt_def: pub mk_adt_def_from_data(AdtDefData): AdtDef -> AdtDef<'tcx>,
     external_constraints: pub mk_external_constraints(ExternalConstraintsData<TyCtxt<'tcx>>):
         ExternalConstraints -> ExternalConstraints<'tcx>,
-    predefined_opaques_in_body: pub mk_predefined_opaques_in_body(PredefinedOpaquesData<TyCtxt<'tcx>>):
-        PredefinedOpaques -> PredefinedOpaques<'tcx>,
 }
 
 macro_rules! slice_interners {
@@ -2786,6 +2784,7 @@ slice_interners!(
     offset_of: pub mk_offset_of((VariantIdx, FieldIdx)),
     patterns: pub mk_patterns(Pattern<'tcx>),
     outlives: pub mk_outlives(ty::ArgOutlivesPredicate<'tcx>),
+    predefined_opaques_in_body: pub mk_predefined_opaques_in_body((ty::OpaqueTypeKey<'tcx>, Ty<'tcx>)),
 );
 
 impl<'tcx> TyCtxt<'tcx> {
@@ -3129,6 +3128,14 @@ impl<'tcx> TyCtxt<'tcx> {
         T::collect_and_apply(iter, |xs| self.mk_poly_existential_predicates(xs))
     }
 
+    pub fn mk_predefined_opaques_in_body_from_iter<I, T>(self, iter: I) -> T::Output
+    where
+        I: Iterator<Item = T>,
+        T: CollectAndApply<(ty::OpaqueTypeKey<'tcx>, Ty<'tcx>), PredefinedOpaques<'tcx>>,
+    {
+        T::collect_and_apply(iter, |xs| self.mk_predefined_opaques_in_body(xs))
+    }
+
     pub fn mk_clauses_from_iter<I, T>(self, iter: I) -> T::Output
     where
         I: Iterator<Item = T>,
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index 0ffef393a33..ce4de6b95e0 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -25,6 +25,7 @@ pub use generic_args::{GenericArgKind, TermKind, *};
 pub use generics::*;
 pub use intrinsic::IntrinsicDef;
 use rustc_abi::{Align, FieldIdx, Integer, IntegerType, ReprFlags, ReprOptions, VariantIdx};
+use rustc_ast::expand::typetree::{FncTree, Kind, Type, TypeTree};
 use rustc_ast::node_id::NodeMap;
 pub use rustc_ast_ir::{Movability, Mutability, try_visit};
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, FxIndexSet};
@@ -62,7 +63,7 @@ pub use rustc_type_ir::solve::SizedTraitKind;
 pub use rustc_type_ir::*;
 #[allow(hidden_glob_reexports, unused_imports)]
 use rustc_type_ir::{InferCtxtLike, Interner};
-use tracing::{debug, instrument};
+use tracing::{debug, instrument, trace};
 pub use vtable::*;
 use {rustc_ast as ast, rustc_hir as hir};
 
@@ -2216,3 +2217,225 @@ pub struct DestructuredConst<'tcx> {
     pub variant: Option<VariantIdx>,
     pub fields: &'tcx [ty::Const<'tcx>],
 }
+
+/// Generate TypeTree information for autodiff.
+/// This function creates TypeTree metadata that describes the memory layout
+/// of function parameters and return types for Enzyme autodiff.
+pub fn fnc_typetrees<'tcx>(tcx: TyCtxt<'tcx>, fn_ty: Ty<'tcx>) -> FncTree {
+    // Check if TypeTrees are disabled via NoTT flag
+    if tcx.sess.opts.unstable_opts.autodiff.contains(&rustc_session::config::AutoDiff::NoTT) {
+        return FncTree { args: vec![], ret: TypeTree::new() };
+    }
+
+    // Check if this is actually a function type
+    if !fn_ty.is_fn() {
+        return FncTree { args: vec![], ret: TypeTree::new() };
+    }
+
+    // Get the function signature
+    let fn_sig = fn_ty.fn_sig(tcx);
+    let sig = tcx.instantiate_bound_regions_with_erased(fn_sig);
+
+    // Create TypeTrees for each input parameter
+    let mut args = vec![];
+    for ty in sig.inputs().iter() {
+        let type_tree = typetree_from_ty(tcx, *ty);
+        args.push(type_tree);
+    }
+
+    // Create TypeTree for return type
+    let ret = typetree_from_ty(tcx, sig.output());
+
+    FncTree { args, ret }
+}
+
+/// Generate TypeTree for a specific type.
+/// This function analyzes a Rust type and creates appropriate TypeTree metadata.
+pub fn typetree_from_ty<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> TypeTree {
+    let mut visited = Vec::new();
+    typetree_from_ty_inner(tcx, ty, 0, &mut visited)
+}
+
+/// Maximum recursion depth for TypeTree generation to prevent stack overflow
+/// from pathological deeply nested types. Combined with cycle detection.
+const MAX_TYPETREE_DEPTH: usize = 6;
+
+/// Internal recursive function for TypeTree generation with cycle detection and depth limiting.
+fn typetree_from_ty_inner<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    ty: Ty<'tcx>,
+    depth: usize,
+    visited: &mut Vec<Ty<'tcx>>,
+) -> TypeTree {
+    if depth >= MAX_TYPETREE_DEPTH {
+        trace!("typetree depth limit {} reached for type: {}", MAX_TYPETREE_DEPTH, ty);
+        return TypeTree::new();
+    }
+
+    if visited.contains(&ty) {
+        return TypeTree::new();
+    }
+
+    visited.push(ty);
+    let result = typetree_from_ty_impl(tcx, ty, depth, visited);
+    visited.pop();
+    result
+}
+
+/// Implementation of TypeTree generation logic.
+fn typetree_from_ty_impl<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    ty: Ty<'tcx>,
+    depth: usize,
+    visited: &mut Vec<Ty<'tcx>>,
+) -> TypeTree {
+    typetree_from_ty_impl_inner(tcx, ty, depth, visited, false)
+}
+
+/// Internal implementation with context about whether this is for a reference target.
+fn typetree_from_ty_impl_inner<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    ty: Ty<'tcx>,
+    depth: usize,
+    visited: &mut Vec<Ty<'tcx>>,
+    is_reference_target: bool,
+) -> TypeTree {
+    if ty.is_scalar() {
+        let (kind, size) = if ty.is_integral() || ty.is_char() || ty.is_bool() {
+            (Kind::Integer, ty.primitive_size(tcx).bytes_usize())
+        } else if ty.is_floating_point() {
+            match ty {
+                x if x == tcx.types.f16 => (Kind::Half, 2),
+                x if x == tcx.types.f32 => (Kind::Float, 4),
+                x if x == tcx.types.f64 => (Kind::Double, 8),
+                x if x == tcx.types.f128 => (Kind::F128, 16),
+                _ => (Kind::Integer, 0),
+            }
+        } else {
+            (Kind::Integer, 0)
+        };
+
+        // Use offset 0 for scalars that are direct targets of references (like &f64)
+        // Use offset -1 for scalars used directly (like function return types)
+        let offset = if is_reference_target && !ty.is_array() { 0 } else { -1 };
+        return TypeTree(vec![Type { offset, size, kind, child: TypeTree::new() }]);
+    }
+
+    if ty.is_ref() || ty.is_raw_ptr() || ty.is_box() {
+        let inner_ty = if let Some(inner) = ty.builtin_deref(true) {
+            inner
+        } else {
+            return TypeTree::new();
+        };
+
+        let child = typetree_from_ty_impl_inner(tcx, inner_ty, depth + 1, visited, true);
+        return TypeTree(vec![Type {
+            offset: -1,
+            size: tcx.data_layout.pointer_size().bytes_usize(),
+            kind: Kind::Pointer,
+            child,
+        }]);
+    }
+
+    if ty.is_array() {
+        if let ty::Array(element_ty, len_const) = ty.kind() {
+            let len = len_const.try_to_target_usize(tcx).unwrap_or(0);
+            if len == 0 {
+                return TypeTree::new();
+            }
+            let element_tree =
+                typetree_from_ty_impl_inner(tcx, *element_ty, depth + 1, visited, false);
+            let mut types = Vec::new();
+            for elem_type in &element_tree.0 {
+                types.push(Type {
+                    offset: -1,
+                    size: elem_type.size,
+                    kind: elem_type.kind,
+                    child: elem_type.child.clone(),
+                });
+            }
+
+            return TypeTree(types);
+        }
+    }
+
+    if ty.is_slice() {
+        if let ty::Slice(element_ty) = ty.kind() {
+            let element_tree =
+                typetree_from_ty_impl_inner(tcx, *element_ty, depth + 1, visited, false);
+            return element_tree;
+        }
+    }
+
+    if let ty::Tuple(tuple_types) = ty.kind() {
+        if tuple_types.is_empty() {
+            return TypeTree::new();
+        }
+
+        let mut types = Vec::new();
+        let mut current_offset = 0;
+
+        for tuple_ty in tuple_types.iter() {
+            let element_tree =
+                typetree_from_ty_impl_inner(tcx, tuple_ty, depth + 1, visited, false);
+
+            let element_layout = tcx
+                .layout_of(ty::TypingEnv::fully_monomorphized().as_query_input(tuple_ty))
+                .ok()
+                .map(|layout| layout.size.bytes_usize())
+                .unwrap_or(0);
+
+            for elem_type in &element_tree.0 {
+                types.push(Type {
+                    offset: if elem_type.offset == -1 {
+                        current_offset as isize
+                    } else {
+                        current_offset as isize + elem_type.offset
+                    },
+                    size: elem_type.size,
+                    kind: elem_type.kind,
+                    child: elem_type.child.clone(),
+                });
+            }
+
+            current_offset += element_layout;
+        }
+
+        return TypeTree(types);
+    }
+
+    if let ty::Adt(adt_def, args) = ty.kind() {
+        if adt_def.is_struct() {
+            let struct_layout =
+                tcx.layout_of(ty::TypingEnv::fully_monomorphized().as_query_input(ty));
+            if let Ok(layout) = struct_layout {
+                let mut types = Vec::new();
+
+                for (field_idx, field_def) in adt_def.all_fields().enumerate() {
+                    let field_ty = field_def.ty(tcx, args);
+                    let field_tree =
+                        typetree_from_ty_impl_inner(tcx, field_ty, depth + 1, visited, false);
+
+                    let field_offset = layout.fields.offset(field_idx).bytes_usize();
+
+                    for elem_type in &field_tree.0 {
+                        types.push(Type {
+                            offset: if elem_type.offset == -1 {
+                                field_offset as isize
+                            } else {
+                                field_offset as isize + elem_type.offset
+                            },
+                            size: elem_type.size,
+                            kind: elem_type.kind,
+                            child: elem_type.child.clone(),
+                        });
+                    }
+                }
+
+                return TypeTree(types);
+            }
+        }
+    }
+
+    TypeTree::new()
+}
diff --git a/compiler/rustc_middle/src/ty/structural_impls.rs b/compiler/rustc_middle/src/ty/structural_impls.rs
index 11d109b463d..8dc4dfd677b 100644
--- a/compiler/rustc_middle/src/ty/structural_impls.rs
+++ b/compiler/rustc_middle/src/ty/structural_impls.rs
@@ -796,6 +796,7 @@ macro_rules! list_fold {
 
 list_fold! {
     &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>> : mk_poly_existential_predicates,
+    &'tcx ty::List<(ty::OpaqueTypeKey<'tcx>, Ty<'tcx>)>: mk_predefined_opaques_in_body,
     &'tcx ty::List<PlaceElem<'tcx>> : mk_place_elems,
     &'tcx ty::List<ty::Pattern<'tcx>> : mk_patterns,
     &'tcx ty::List<ty::ArgOutlivesPredicate<'tcx>> : mk_outlives,
diff --git a/compiler/rustc_middle/src/ty/typeck_results.rs b/compiler/rustc_middle/src/ty/typeck_results.rs
index 8dd80aab946..944bd9756a9 100644
--- a/compiler/rustc_middle/src/ty/typeck_results.rs
+++ b/compiler/rustc_middle/src/ty/typeck_results.rs
@@ -167,7 +167,7 @@ pub struct TypeckResults<'tcx> {
     /// We also store the type here, so that the compiler can use it as a hint
     /// for figuring out hidden types, even if they are only set in dead code
     /// (which doesn't show up in MIR).
-    pub concrete_opaque_types: FxIndexMap<LocalDefId, ty::OpaqueHiddenType<'tcx>>,
+    pub hidden_types: FxIndexMap<LocalDefId, ty::OpaqueHiddenType<'tcx>>,
 
     /// Tracks the minimum captures required for a closure;
     /// see `MinCaptureInformationMap` for more details.
@@ -250,7 +250,7 @@ impl<'tcx> TypeckResults<'tcx> {
             coercion_casts: Default::default(),
             used_trait_imports: Default::default(),
             tainted_by_errors: None,
-            concrete_opaque_types: Default::default(),
+            hidden_types: Default::default(),
             closure_min_captures: Default::default(),
             closure_fake_reads: Default::default(),
             rvalue_scopes: Default::default(),
diff --git a/compiler/rustc_middle/src/ty/vtable.rs b/compiler/rustc_middle/src/ty/vtable.rs
index e2f09fdcb4b..a3e9054fdcb 100644
--- a/compiler/rustc_middle/src/ty/vtable.rs
+++ b/compiler/rustc_middle/src/ty/vtable.rs
@@ -104,7 +104,7 @@ pub(super) fn vtable_allocation_provider<'tcx>(
         .expect("failed to build vtable representation");
     assert!(layout.is_sized(), "can't create a vtable for an unsized type");
     let size = layout.size.bytes();
-    let align = layout.align.abi.bytes();
+    let align = layout.align.bytes();
 
     let ptr_size = tcx.data_layout.pointer_size();
     let ptr_align = tcx.data_layout.pointer_align().abi;
diff --git a/compiler/rustc_mir_build/src/builder/mod.rs b/compiler/rustc_mir_build/src/builder/mod.rs
index cdb2c5561ce..7ca94e655fb 100644
--- a/compiler/rustc_mir_build/src/builder/mod.rs
+++ b/compiler/rustc_mir_build/src/builder/mod.rs
@@ -395,12 +395,10 @@ enum NeedsTemporary {
     Maybe,
 }
 
-///////////////////////////////////////////////////////////////////////////
 /// The `BlockAnd` "monad" packages up the new basic block along with a
 /// produced value (sometimes just unit, of course). The `unpack!`
 /// macro (and methods below) makes working with `BlockAnd` much more
 /// convenient.
-
 #[must_use = "if you don't use one of these results, you're leaving a dangling edge"]
 struct BlockAnd<T>(BasicBlock, T);
 
@@ -438,9 +436,7 @@ macro_rules! unpack {
     }};
 }
 
-///////////////////////////////////////////////////////////////////////////
-/// the main entry point for building MIR for a function
-
+/// The main entry point for building MIR for a function.
 fn construct_fn<'tcx>(
     tcx: TyCtxt<'tcx>,
     fn_def: LocalDefId,
diff --git a/compiler/rustc_mir_build/src/check_unsafety.rs b/compiler/rustc_mir_build/src/check_unsafety.rs
index b5e165c7517..195d45c2c4c 100644
--- a/compiler/rustc_mir_build/src/check_unsafety.rs
+++ b/compiler/rustc_mir_build/src/check_unsafety.rs
@@ -554,6 +554,21 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
                     visit::walk_expr(self, &self.thir[arg]);
                     return;
                 }
+
+                // Secondly, we allow raw borrows of union field accesses. Peel
+                // any of those off, and recurse normally on the LHS, which should
+                // reject any unsafe operations within.
+                let mut peeled = arg;
+                while let ExprKind::Scope { value: arg, .. } = self.thir[peeled].kind
+                    && let ExprKind::Field { lhs, name: _, variant_index: _ } = self.thir[arg].kind
+                    && let ty::Adt(def, _) = &self.thir[lhs].ty.kind()
+                    && def.is_union()
+                {
+                    peeled = lhs;
+                }
+                visit::walk_expr(self, &self.thir[peeled]);
+                // And return so we don't recurse directly onto the union field access(es).
+                return;
             }
             ExprKind::Deref { arg } => {
                 if let ExprKind::StaticRef { def_id, .. } | ExprKind::ThreadLocalRef(def_id) =
diff --git a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
index ae67bb5075e..3929a97eed8 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
@@ -1275,13 +1275,13 @@ fn report_non_exhaustive_match<'p, 'tcx>(
             if ty.is_ptr_sized_integral() {
                 if ty.inner() == cx.tcx.types.usize {
                     err.note(format!(
-                        "`{ty}` does not have a fixed maximum value, so half-open ranges are \
-                         necessary to match exhaustively",
+                        "`{ty}::MAX` is not treated as exhaustive, \
+                        so half-open ranges are necessary to match exhaustively",
                     ));
                 } else if ty.inner() == cx.tcx.types.isize {
                     err.note(format!(
-                        "`{ty}` does not have fixed minimum and maximum values, so half-open \
-                         ranges are necessary to match exhaustively",
+                        "`{ty}::MIN` and `{ty}::MAX` are not treated as exhaustive, \
+                        so half-open ranges are necessary to match exhaustively",
                     ));
                 }
             } else if ty.inner() == cx.tcx.types.str_ {
diff --git a/compiler/rustc_mir_transform/src/abort_unwinding_calls.rs b/compiler/rustc_mir_transform/src/abort_unwinding_calls.rs
index 5bd6fdcf485..35a21a2a834 100644
--- a/compiler/rustc_mir_transform/src/abort_unwinding_calls.rs
+++ b/compiler/rustc_mir_transform/src/abort_unwinding_calls.rs
@@ -3,6 +3,7 @@ use rustc_ast::InlineAsmOptions;
 use rustc_middle::mir::*;
 use rustc_middle::span_bug;
 use rustc_middle::ty::{self, TyCtxt, layout};
+use rustc_span::sym;
 use rustc_target::spec::PanicStrategy;
 
 /// A pass that runs which is targeted at ensuring that codegen guarantees about
@@ -33,6 +34,19 @@ impl<'tcx> crate::MirPass<'tcx> for AbortUnwindingCalls {
             return;
         }
 
+        // Represent whether this compilation target fundamentally doesn't
+        // support unwinding at all at an ABI level. If this the target has no
+        // support for unwinding then cleanup actions, for example, are all
+        // unnecessary and can be considered unreachable.
+        //
+        // Currently this is only true for wasm targets on panic=abort when the
+        // `exception-handling` target feature is disabled. In such a
+        // configuration it's illegal to emit exception-related instructions so
+        // it's not possible to unwind.
+        let target_supports_unwinding = !(tcx.sess.target.is_like_wasm
+            && tcx.sess.panic_strategy() == PanicStrategy::Abort
+            && !tcx.asm_target_features(def_id).contains(&sym::exception_handling));
+
         // Here we test for this function itself whether its ABI allows
         // unwinding or not.
         let body_ty = tcx.type_of(def_id).skip_binder();
@@ -54,12 +68,18 @@ impl<'tcx> crate::MirPass<'tcx> for AbortUnwindingCalls {
             let Some(terminator) = &mut block.terminator else { continue };
             let span = terminator.source_info.span;
 
-            // If we see an `UnwindResume` terminator inside a function that cannot unwind, we need
-            // to replace it with `UnwindTerminate`.
-            if let TerminatorKind::UnwindResume = &terminator.kind
-                && !body_can_unwind
-            {
-                terminator.kind = TerminatorKind::UnwindTerminate(UnwindTerminateReason::Abi);
+            // If we see an `UnwindResume` terminator inside a function then:
+            //
+            // * If the target doesn't support unwinding at all, then this is an
+            //   unreachable block.
+            // * If the body cannot unwind, we need to replace it with
+            //   `UnwindTerminate`.
+            if let TerminatorKind::UnwindResume = &terminator.kind {
+                if !target_supports_unwinding {
+                    terminator.kind = TerminatorKind::Unreachable;
+                } else if !body_can_unwind {
+                    terminator.kind = TerminatorKind::UnwindTerminate(UnwindTerminateReason::Abi);
+                }
             }
 
             if block.is_cleanup {
@@ -93,8 +113,9 @@ impl<'tcx> crate::MirPass<'tcx> for AbortUnwindingCalls {
                 _ => continue,
             };
 
-            if !call_can_unwind {
-                // If this function call can't unwind, then there's no need for it
+            if !call_can_unwind || !target_supports_unwinding {
+                // If this function call can't unwind, or if the target doesn't
+                // support unwinding at all, then there's no need for it
                 // to have a landing pad. This means that we can remove any cleanup
                 // registered for it (and turn it into `UnwindAction::Unreachable`).
                 let cleanup = block.terminator_mut().unwind_mut().unwrap();
diff --git a/compiler/rustc_mir_transform/src/dataflow_const_prop.rs b/compiler/rustc_mir_transform/src/dataflow_const_prop.rs
index d250cdea7e8..e970f7ff81a 100644
--- a/compiler/rustc_mir_transform/src/dataflow_const_prop.rs
+++ b/compiler/rustc_mir_transform/src/dataflow_const_prop.rs
@@ -476,7 +476,7 @@ impl<'a, 'tcx> ConstAnalysis<'a, 'tcx> {
                 };
                 let val = match null_op {
                     NullOp::SizeOf if layout.is_sized() => layout.size.bytes(),
-                    NullOp::AlignOf if layout.is_sized() => layout.align.abi.bytes(),
+                    NullOp::AlignOf if layout.is_sized() => layout.align.bytes(),
                     NullOp::OffsetOf(fields) => self
                         .ecx
                         .tcx
diff --git a/compiler/rustc_mir_transform/src/gvn.rs b/compiler/rustc_mir_transform/src/gvn.rs
index eb59ae830ae..99691d9e045 100644
--- a/compiler/rustc_mir_transform/src/gvn.rs
+++ b/compiler/rustc_mir_transform/src/gvn.rs
@@ -618,7 +618,7 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
                 }
                 let val = match null_op {
                     NullOp::SizeOf => arg_layout.size.bytes(),
-                    NullOp::AlignOf => arg_layout.align.abi.bytes(),
+                    NullOp::AlignOf => arg_layout.align.bytes(),
                     NullOp::OffsetOf(fields) => self
                         .ecx
                         .tcx
diff --git a/compiler/rustc_mir_transform/src/jump_threading.rs b/compiler/rustc_mir_transform/src/jump_threading.rs
index f9e642e28eb..68298767e7f 100644
--- a/compiler/rustc_mir_transform/src/jump_threading.rs
+++ b/compiler/rustc_mir_transform/src/jump_threading.rs
@@ -84,7 +84,7 @@ impl<'tcx> crate::MirPass<'tcx> for JumpThreading {
             body,
             arena,
             map: Map::new(tcx, body, Some(MAX_PLACES)),
-            loop_headers: loop_headers(body),
+            maybe_loop_headers: maybe_loop_headers(body),
             opportunities: Vec::new(),
         };
 
@@ -100,7 +100,7 @@ impl<'tcx> crate::MirPass<'tcx> for JumpThreading {
 
         // Verify that we do not thread through a loop header.
         for to in opportunities.iter() {
-            assert!(to.chain.iter().all(|&block| !finder.loop_headers.contains(block)));
+            assert!(to.chain.iter().all(|&block| !finder.maybe_loop_headers.contains(block)));
         }
         OpportunitySet::new(body, opportunities).apply(body);
     }
@@ -124,7 +124,7 @@ struct TOFinder<'a, 'tcx> {
     ecx: InterpCx<'tcx, DummyMachine>,
     body: &'a Body<'tcx>,
     map: Map<'tcx>,
-    loop_headers: DenseBitSet<BasicBlock>,
+    maybe_loop_headers: DenseBitSet<BasicBlock>,
     /// We use an arena to avoid cloning the slices when cloning `state`.
     arena: &'a DroplessArena,
     opportunities: Vec<ThreadingOpportunity>,
@@ -190,7 +190,7 @@ impl<'a, 'tcx> TOFinder<'a, 'tcx> {
     #[instrument(level = "trace", skip(self))]
     fn start_from_switch(&mut self, bb: BasicBlock) {
         let bbdata = &self.body[bb];
-        if bbdata.is_cleanup || self.loop_headers.contains(bb) {
+        if bbdata.is_cleanup || self.maybe_loop_headers.contains(bb) {
             return;
         }
         let Some((discr, targets)) = bbdata.terminator().kind.as_switch() else { return };
@@ -235,7 +235,7 @@ impl<'a, 'tcx> TOFinder<'a, 'tcx> {
         depth: usize,
     ) {
         // Do not thread through loop headers.
-        if self.loop_headers.contains(bb) {
+        if self.maybe_loop_headers.contains(bb) {
             return;
         }
 
@@ -833,20 +833,28 @@ enum Update {
     Decr,
 }
 
-/// Compute the set of loop headers in the given body. We define a loop header as a block which has
-/// at least a predecessor which it dominates. This definition is only correct for reducible CFGs.
-/// But if the CFG is already irreducible, there is no point in trying much harder.
-/// is already irreducible.
-fn loop_headers(body: &Body<'_>) -> DenseBitSet<BasicBlock> {
-    let mut loop_headers = DenseBitSet::new_empty(body.basic_blocks.len());
-    let dominators = body.basic_blocks.dominators();
-    // Only visit reachable blocks.
-    for (bb, bbdata) in traversal::preorder(body) {
+/// Compute the set of loop headers in the given body. A loop header is usually defined as a block
+/// which dominates one of its predecessors. This definition is only correct for reducible CFGs.
+/// However, computing dominators is expensive, so we approximate according to the post-order
+/// traversal order. A loop header for us is a block which is visited after its predecessor in
+/// post-order. This is ok as we mostly need a heuristic.
+fn maybe_loop_headers(body: &Body<'_>) -> DenseBitSet<BasicBlock> {
+    let mut maybe_loop_headers = DenseBitSet::new_empty(body.basic_blocks.len());
+    let mut visited = DenseBitSet::new_empty(body.basic_blocks.len());
+    for (bb, bbdata) in traversal::postorder(body) {
+        // Post-order means we visit successors before the block for acyclic CFGs.
+        // If the successor is not visited yet, consider it a loop header.
         for succ in bbdata.terminator().successors() {
-            if dominators.dominates(succ, bb) {
-                loop_headers.insert(succ);
+            if !visited.contains(succ) {
+                maybe_loop_headers.insert(succ);
             }
         }
+
+        // Only mark `bb` as visited after we checked the successors, in case we have a self-loop.
+        //     bb1: goto -> bb1;
+        let _new = visited.insert(bb);
+        debug_assert!(_new);
     }
-    loop_headers
+
+    maybe_loop_headers
 }
diff --git a/compiler/rustc_mir_transform/src/known_panics_lint.rs b/compiler/rustc_mir_transform/src/known_panics_lint.rs
index 0686dca9962..93abc0f8860 100644
--- a/compiler/rustc_mir_transform/src/known_panics_lint.rs
+++ b/compiler/rustc_mir_transform/src/known_panics_lint.rs
@@ -609,7 +609,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                 let op_layout = self.ecx.layout_of(ty).ok()?;
                 let val = match null_op {
                     NullOp::SizeOf => op_layout.size.bytes(),
-                    NullOp::AlignOf => op_layout.align.abi.bytes(),
+                    NullOp::AlignOf => op_layout.align.bytes(),
                     NullOp::OffsetOf(fields) => self
                         .tcx
                         .offset_of_subfield(self.typing_env, op_layout, fields.iter())
diff --git a/compiler/rustc_mir_transform/src/patch.rs b/compiler/rustc_mir_transform/src/patch.rs
index d831ab50b1a..cc8ea76011b 100644
--- a/compiler/rustc_mir_transform/src/patch.rs
+++ b/compiler/rustc_mir_transform/src/patch.rs
@@ -11,6 +11,8 @@ use tracing::debug;
 /// once with `apply`. This is useful for MIR transformation passes.
 pub(crate) struct MirPatch<'tcx> {
     term_patch_map: FxHashMap<BasicBlock, TerminatorKind<'tcx>>,
+    /// Set of statements that should be replaced by `Nop`.
+    nop_statements: Vec<Location>,
     new_blocks: Vec<BasicBlockData<'tcx>>,
     new_statements: Vec<(Location, StatementKind<'tcx>)>,
     new_locals: Vec<LocalDecl<'tcx>>,
@@ -33,6 +35,7 @@ impl<'tcx> MirPatch<'tcx> {
     pub(crate) fn new(body: &Body<'tcx>) -> Self {
         let mut result = MirPatch {
             term_patch_map: Default::default(),
+            nop_statements: vec![],
             new_blocks: vec![],
             new_statements: vec![],
             new_locals: vec![],
@@ -212,6 +215,15 @@ impl<'tcx> MirPatch<'tcx> {
         self.term_patch_map.insert(block, new);
     }
 
+    /// Mark given statement to be replaced by a `Nop`.
+    ///
+    /// This method only works on statements from the initial body, and cannot be used to remove
+    /// statements from `add_statement` or `add_assign`.
+    #[tracing::instrument(level = "debug", skip(self))]
+    pub(crate) fn nop_statement(&mut self, loc: Location) {
+        self.nop_statements.push(loc);
+    }
+
     /// Queues the insertion of a statement at a given location. The statement
     /// currently at that location, and all statements that follow, are shifted
     /// down. If multiple statements are queued for addition at the same
@@ -257,11 +269,8 @@ impl<'tcx> MirPatch<'tcx> {
         bbs.extend(self.new_blocks);
         body.local_decls.extend(self.new_locals);
 
-        // The order in which we patch terminators does not change the result.
-        #[allow(rustc::potential_query_instability)]
-        for (src, patch) in self.term_patch_map {
-            debug!("MirPatch: patching block {:?}", src);
-            bbs[src].terminator_mut().kind = patch;
+        for loc in self.nop_statements {
+            bbs[loc.block].statements[loc.statement_index].make_nop();
         }
 
         let mut new_statements = self.new_statements;
@@ -285,6 +294,17 @@ impl<'tcx> MirPatch<'tcx> {
                 .insert(loc.statement_index, Statement::new(source_info, stmt));
             delta += 1;
         }
+
+        // The order in which we patch terminators does not change the result.
+        #[allow(rustc::potential_query_instability)]
+        for (src, patch) in self.term_patch_map {
+            debug!("MirPatch: patching block {:?}", src);
+            let bb = &mut bbs[src];
+            if let TerminatorKind::Unreachable = patch {
+                bb.statements.clear();
+            }
+            bb.terminator_mut().kind = patch;
+        }
     }
 
     fn source_info_for_index(data: &BasicBlockData<'_>, loc: Location) -> SourceInfo {
diff --git a/compiler/rustc_mir_transform/src/simplify_branches.rs b/compiler/rustc_mir_transform/src/simplify_branches.rs
index 886f4d6e509..ed94a058ec6 100644
--- a/compiler/rustc_mir_transform/src/simplify_branches.rs
+++ b/compiler/rustc_mir_transform/src/simplify_branches.rs
@@ -2,6 +2,8 @@ use rustc_middle::mir::*;
 use rustc_middle::ty::TyCtxt;
 use tracing::trace;
 
+use crate::patch::MirPatch;
+
 pub(super) enum SimplifyConstCondition {
     AfterConstProp,
     Final,
@@ -19,8 +21,10 @@ impl<'tcx> crate::MirPass<'tcx> for SimplifyConstCondition {
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         trace!("Running SimplifyConstCondition on {:?}", body.source);
         let typing_env = body.typing_env(tcx);
-        'blocks: for block in body.basic_blocks_mut() {
-            for stmt in block.statements.iter_mut() {
+        let mut patch = MirPatch::new(body);
+
+        'blocks: for (bb, block) in body.basic_blocks.iter_enumerated() {
+            for (statement_index, stmt) in block.statements.iter().enumerate() {
                 // Simplify `assume` of a known value: either a NOP or unreachable.
                 if let StatementKind::Intrinsic(box ref intrinsic) = stmt.kind
                     && let NonDivergingIntrinsic::Assume(discr) = intrinsic
@@ -28,17 +32,16 @@ impl<'tcx> crate::MirPass<'tcx> for SimplifyConstCondition {
                     && let Some(constant) = c.const_.try_eval_bool(tcx, typing_env)
                 {
                     if constant {
-                        stmt.make_nop();
+                        patch.nop_statement(Location { block: bb, statement_index });
                     } else {
-                        block.statements.clear();
-                        block.terminator_mut().kind = TerminatorKind::Unreachable;
+                        patch.patch_terminator(bb, TerminatorKind::Unreachable);
                         continue 'blocks;
                     }
                 }
             }
 
-            let terminator = block.terminator_mut();
-            terminator.kind = match terminator.kind {
+            let terminator = block.terminator();
+            let terminator = match terminator.kind {
                 TerminatorKind::SwitchInt {
                     discr: Operand::Constant(ref c), ref targets, ..
                 } => {
@@ -58,7 +61,9 @@ impl<'tcx> crate::MirPass<'tcx> for SimplifyConstCondition {
                 },
                 _ => continue,
             };
+            patch.patch_terminator(bb, terminator);
         }
+        patch.apply(body);
     }
 
     fn is_required(&self) -> bool {
diff --git a/compiler/rustc_next_trait_solver/src/canonical/mod.rs b/compiler/rustc_next_trait_solver/src/canonical/mod.rs
index e3520e238ed..b036ee6df7e 100644
--- a/compiler/rustc_next_trait_solver/src/canonical/mod.rs
+++ b/compiler/rustc_next_trait_solver/src/canonical/mod.rs
@@ -25,7 +25,7 @@ use crate::delegate::SolverDelegate;
 use crate::resolve::eager_resolve_vars;
 use crate::solve::{
     CanonicalInput, CanonicalResponse, Certainty, ExternalConstraintsData, Goal,
-    NestedNormalizationGoals, PredefinedOpaquesData, QueryInput, Response, inspect,
+    NestedNormalizationGoals, QueryInput, Response, inspect,
 };
 
 pub mod canonicalizer;
@@ -53,7 +53,7 @@ impl<I: Interner, T> ResponseT<I> for inspect::State<I, T> {
 pub(super) fn canonicalize_goal<D, I>(
     delegate: &D,
     goal: Goal<I, I::Predicate>,
-    opaque_types: Vec<(ty::OpaqueTypeKey<I>, I::Ty)>,
+    opaque_types: &[(ty::OpaqueTypeKey<I>, I::Ty)],
 ) -> (Vec<I::GenericArg>, CanonicalInput<I, I::Predicate>)
 where
     D: SolverDelegate<Interner = I>,
@@ -65,9 +65,7 @@ where
         &mut orig_values,
         QueryInput {
             goal,
-            predefined_opaques_in_body: delegate
-                .cx()
-                .mk_predefined_opaques_in_body(PredefinedOpaquesData { opaque_types }),
+            predefined_opaques_in_body: delegate.cx().mk_predefined_opaques_in_body(opaque_types),
         },
     );
     let query_input = ty::CanonicalQueryInput { canonical, typing_mode: delegate.typing_mode() };
diff --git a/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs b/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs
index a2e6ef6f0fe..d58c264841c 100644
--- a/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs
@@ -473,7 +473,10 @@ where
         // fails to reach a fixpoint but ends up getting an error after
         // running for some additional step.
         //
-        // cc trait-system-refactor-initiative#105
+        // FIXME(@lcnr): While I believe an error here to be possible, we
+        // currently don't have any test which actually triggers it. @lqd
+        // created a minimization for an ICE in typenum, but that one no
+        // longer fails here. cc trait-system-refactor-initiative#105.
         let source = CandidateSource::BuiltinImpl(BuiltinImplSource::Misc);
         let certainty = Certainty::Maybe { cause, opaque_types_jank: OpaqueTypesJank::AllGood };
         self.probe_trait_candidate(source)
diff --git a/compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs b/compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs
index c40739d12e6..9b3dc1f691f 100644
--- a/compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs
@@ -664,7 +664,7 @@ fn coroutine_closure_to_ambiguous_coroutine<I: Interner>(
 pub(in crate::solve) fn extract_fn_def_from_const_callable<I: Interner>(
     cx: I,
     self_ty: I::Ty,
-) -> Result<(ty::Binder<I, (I::FnInputTys, I::Ty)>, I::FunctionId, I::GenericArgs), NoSolution> {
+) -> Result<(ty::Binder<I, (I::Ty, I::Ty)>, I::FunctionId, I::GenericArgs), NoSolution> {
     match self_ty.kind() {
         ty::FnDef(def_id, args) => {
             let sig = cx.fn_sig(def_id);
@@ -673,7 +673,8 @@ pub(in crate::solve) fn extract_fn_def_from_const_callable<I: Interner>(
                 && cx.fn_is_const(def_id)
             {
                 Ok((
-                    sig.instantiate(cx, args).map_bound(|sig| (sig.inputs(), sig.output())),
+                    sig.instantiate(cx, args)
+                        .map_bound(|sig| (Ty::new_tup(cx, sig.inputs().as_slice()), sig.output())),
                     def_id,
                     args,
                 ))
diff --git a/compiler/rustc_next_trait_solver/src/solve/effect_goals.rs b/compiler/rustc_next_trait_solver/src/solve/effect_goals.rs
index cb72c1cd92b..65a5edf6b72 100644
--- a/compiler/rustc_next_trait_solver/src/solve/effect_goals.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/effect_goals.rs
@@ -234,12 +234,12 @@ where
         let self_ty = goal.predicate.self_ty();
         let (inputs_and_output, def_id, args) =
             structural_traits::extract_fn_def_from_const_callable(cx, self_ty)?;
+        let (inputs, output) = ecx.instantiate_binder_with_infer(inputs_and_output);
 
         // A built-in `Fn` impl only holds if the output is sized.
         // (FIXME: technically we only need to check this if the type is a fn ptr...)
-        let output_is_sized_pred = inputs_and_output.map_bound(|(_, output)| {
-            ty::TraitRef::new(cx, cx.require_trait_lang_item(SolverTraitLangItem::Sized), [output])
-        });
+        let output_is_sized_pred =
+            ty::TraitRef::new(cx, cx.require_trait_lang_item(SolverTraitLangItem::Sized), [output]);
         let requirements = cx
             .const_conditions(def_id.into())
             .iter_instantiated(cx, args)
@@ -251,15 +251,12 @@ where
             })
             .chain([(GoalSource::ImplWhereBound, goal.with(cx, output_is_sized_pred))]);
 
-        let pred = inputs_and_output
-            .map_bound(|(inputs, _)| {
-                ty::TraitRef::new(
-                    cx,
-                    goal.predicate.def_id(),
-                    [goal.predicate.self_ty(), Ty::new_tup(cx, inputs.as_slice())],
-                )
-            })
-            .to_host_effect_clause(cx, goal.predicate.constness);
+        let pred = ty::Binder::dummy(ty::TraitRef::new(
+            cx,
+            goal.predicate.def_id(),
+            [goal.predicate.self_ty(), inputs],
+        ))
+        .to_host_effect_clause(cx, goal.predicate.constness);
 
         Self::probe_and_consider_implied_clause(
             ecx,
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 bb86357a85f..f25003bbfe9 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
@@ -194,7 +194,7 @@ where
     D: SolverDelegate<Interner = I>,
     I: Interner,
 {
-    #[instrument(level = "debug", skip(self))]
+    #[instrument(level = "debug", skip(self), ret)]
     fn evaluate_root_goal(
         &self,
         goal: Goal<I, I::Predicate>,
@@ -206,6 +206,7 @@ where
         })
     }
 
+    #[instrument(level = "debug", skip(self), ret)]
     fn root_goal_may_hold_opaque_types_jank(
         &self,
         goal: Goal<Self::Interner, <Self::Interner as Interner>::Predicate>,
@@ -357,7 +358,7 @@ where
         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 {
+        for (key, ty) in input.predefined_opaques_in_body.iter() {
             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
             // with the same key after resolving contained inference variables.
@@ -467,7 +468,7 @@ 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) = canonicalize_goal(self.delegate, goal, opaque_types);
+        let (orig_values, canonical_goal) = canonicalize_goal(self.delegate, goal, &opaque_types);
         let canonical_result = self.search_graph.evaluate_goal(
             self.cx(),
             canonical_goal,
@@ -548,7 +549,6 @@ where
                             .canonical
                             .value
                             .predefined_opaques_in_body
-                            .opaque_types
                             .len(),
                         stalled_vars,
                         sub_roots,
@@ -633,28 +633,19 @@ where
     // the certainty of all the goals.
     #[instrument(level = "trace", skip(self))]
     pub(super) fn try_evaluate_added_goals(&mut self) -> Result<Certainty, NoSolution> {
-        let mut response = Ok(Certainty::overflow(false));
         for _ in 0..FIXPOINT_STEP_LIMIT {
-            // FIXME: This match is a bit ugly, it might be nice to change the inspect
-            // stuff to use a closure instead. which should hopefully simplify this a bit.
             match self.evaluate_added_goals_step() {
-                Ok(Some(cert)) => {
-                    response = Ok(cert);
-                    break;
-                }
                 Ok(None) => {}
+                Ok(Some(cert)) => return Ok(cert),
                 Err(NoSolution) => {
-                    response = Err(NoSolution);
-                    break;
+                    self.tainted = Err(NoSolution);
+                    return Err(NoSolution);
                 }
             }
         }
 
-        if response.is_err() {
-            self.tainted = Err(NoSolution);
-        }
-
-        response
+        debug!("try_evaluate_added_goals: encountered overflow");
+        Ok(Certainty::overflow(false))
     }
 
     /// Iterate over all added goals: returning `Ok(Some(_))` in case we can stop rerunning.
@@ -1557,7 +1548,7 @@ pub(super) fn evaluate_root_goal_for_proof_tree<D: SolverDelegate<Interner = 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) = canonicalize_goal(delegate, goal, opaque_types);
+    let (orig_values, canonical_goal) = canonicalize_goal(delegate, goal, &opaque_types);
 
     let (canonical_result, final_revision) =
         delegate.cx().evaluate_root_goal_for_proof_tree_raw(canonical_goal);
diff --git a/compiler/rustc_next_trait_solver/src/solve/mod.rs b/compiler/rustc_next_trait_solver/src/solve/mod.rs
index afb86aaf8ab..a58caeecc33 100644
--- a/compiler/rustc_next_trait_solver/src/solve/mod.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/mod.rs
@@ -381,6 +381,7 @@ where
 }
 
 /// The result of evaluating a goal.
+#[derive_where(Debug; I: Interner)]
 pub struct GoalEvaluation<I: Interner> {
     /// The goal we've evaluated. This is the input goal, but potentially with its
     /// inference variables resolved. This never applies any inference constraints
diff --git a/compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs b/compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs
index 653c59c5d42..0674b3d42ab 100644
--- a/compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs
@@ -451,23 +451,22 @@ where
                     return ecx.forced_ambiguity(MaybeCause::Ambiguity);
                 }
             };
+        let (inputs, output) = ecx.instantiate_binder_with_infer(tupled_inputs_and_output);
 
         // A built-in `Fn` impl only holds if the output is sized.
         // (FIXME: technically we only need to check this if the type is a fn ptr...)
-        let output_is_sized_pred = tupled_inputs_and_output.map_bound(|(_, output)| {
-            ty::TraitRef::new(cx, cx.require_trait_lang_item(SolverTraitLangItem::Sized), [output])
-        });
+        let output_is_sized_pred =
+            ty::TraitRef::new(cx, cx.require_trait_lang_item(SolverTraitLangItem::Sized), [output]);
 
-        let pred = tupled_inputs_and_output
-            .map_bound(|(inputs, output)| ty::ProjectionPredicate {
-                projection_term: ty::AliasTerm::new(
-                    cx,
-                    goal.predicate.def_id(),
-                    [goal.predicate.self_ty(), inputs],
-                ),
-                term: output.into(),
-            })
-            .upcast(cx);
+        let pred = ty::ProjectionPredicate {
+            projection_term: ty::AliasTerm::new(
+                cx,
+                goal.predicate.def_id(),
+                [goal.predicate.self_ty(), inputs],
+            ),
+            term: output.into(),
+        }
+        .upcast(cx);
 
         Self::probe_and_consider_implied_clause(
             ecx,
@@ -497,76 +496,56 @@ where
                 goal_kind,
                 env_region,
             )?;
+        let AsyncCallableRelevantTypes {
+            tupled_inputs_ty,
+            output_coroutine_ty,
+            coroutine_return_ty,
+        } = ecx.instantiate_binder_with_infer(tupled_inputs_and_output_and_coroutine);
 
         // A built-in `AsyncFn` impl only holds if the output is sized.
         // (FIXME: technically we only need to check this if the type is a fn ptr...)
-        let output_is_sized_pred = tupled_inputs_and_output_and_coroutine.map_bound(
-            |AsyncCallableRelevantTypes { output_coroutine_ty: output_ty, .. }| {
-                ty::TraitRef::new(
-                    cx,
-                    cx.require_trait_lang_item(SolverTraitLangItem::Sized),
-                    [output_ty],
-                )
-            },
+        let output_is_sized_pred = ty::TraitRef::new(
+            cx,
+            cx.require_trait_lang_item(SolverTraitLangItem::Sized),
+            [output_coroutine_ty],
         );
 
-        let pred = tupled_inputs_and_output_and_coroutine
-            .map_bound(
-                |AsyncCallableRelevantTypes {
-                     tupled_inputs_ty,
-                     output_coroutine_ty,
-                     coroutine_return_ty,
-                 }| {
-                    let (projection_term, term) = if cx
-                        .is_lang_item(goal.predicate.def_id(), SolverLangItem::CallOnceFuture)
-                    {
-                        (
-                            ty::AliasTerm::new(
-                                cx,
-                                goal.predicate.def_id(),
-                                [goal.predicate.self_ty(), tupled_inputs_ty],
-                            ),
-                            output_coroutine_ty.into(),
-                        )
-                    } else if cx
-                        .is_lang_item(goal.predicate.def_id(), SolverLangItem::CallRefFuture)
-                    {
-                        (
-                            ty::AliasTerm::new(
-                                cx,
-                                goal.predicate.def_id(),
-                                [
-                                    I::GenericArg::from(goal.predicate.self_ty()),
-                                    tupled_inputs_ty.into(),
-                                    env_region.into(),
-                                ],
-                            ),
-                            output_coroutine_ty.into(),
-                        )
-                    } else if cx
-                        .is_lang_item(goal.predicate.def_id(), SolverLangItem::AsyncFnOnceOutput)
-                    {
-                        (
-                            ty::AliasTerm::new(
-                                cx,
-                                goal.predicate.def_id(),
-                                [
-                                    I::GenericArg::from(goal.predicate.self_ty()),
-                                    tupled_inputs_ty.into(),
-                                ],
-                            ),
-                            coroutine_return_ty.into(),
-                        )
-                    } else {
-                        panic!(
-                            "no such associated type in `AsyncFn*`: {:?}",
-                            goal.predicate.def_id()
-                        )
-                    };
-                    ty::ProjectionPredicate { projection_term, term }
-                },
-            )
-            .upcast(cx);
+        let (projection_term, term) =
+            if cx.is_lang_item(goal.predicate.def_id(), SolverLangItem::CallOnceFuture) {
+                (
+                    ty::AliasTerm::new(
+                        cx,
+                        goal.predicate.def_id(),
+                        [goal.predicate.self_ty(), tupled_inputs_ty],
+                    ),
+                    output_coroutine_ty.into(),
+                )
+            } else if cx.is_lang_item(goal.predicate.def_id(), SolverLangItem::CallRefFuture) {
+                (
+                    ty::AliasTerm::new(
+                        cx,
+                        goal.predicate.def_id(),
+                        [
+                            I::GenericArg::from(goal.predicate.self_ty()),
+                            tupled_inputs_ty.into(),
+                            env_region.into(),
+                        ],
+                    ),
+                    output_coroutine_ty.into(),
+                )
+            } else if cx.is_lang_item(goal.predicate.def_id(), SolverLangItem::AsyncFnOnceOutput) {
+                (
+                    ty::AliasTerm::new(
+                        cx,
+                        goal.predicate.def_id(),
+                        [goal.predicate.self_ty(), tupled_inputs_ty],
+                    ),
+                    coroutine_return_ty.into(),
+                )
+            } else {
+                panic!("no such associated type in `AsyncFn*`: {:?}", goal.predicate.def_id())
+            };
+        let pred = ty::ProjectionPredicate { projection_term, term }.upcast(cx);
 
         Self::probe_and_consider_implied_clause(
             ecx,
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 aa9dfc9a9a2..109c8476ccb 100644
--- a/compiler/rustc_next_trait_solver/src/solve/search_graph.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/search_graph.rs
@@ -74,20 +74,28 @@ where
         }
     }
 
-    fn is_initial_provisional_result(
-        cx: Self::Cx,
-        kind: PathKind,
-        input: CanonicalInput<I>,
-        result: QueryResult<I>,
-    ) -> bool {
-        Self::initial_provisional_result(cx, kind, input) == result
+    fn is_initial_provisional_result(result: QueryResult<I>) -> Option<PathKind> {
+        match result {
+            Ok(response) => {
+                if has_no_inference_or_external_constraints(response) {
+                    if response.value.certainty == Certainty::Yes {
+                        return Some(PathKind::Coinductive);
+                    } else if response.value.certainty == Certainty::overflow(false) {
+                        return Some(PathKind::Unknown);
+                    }
+                }
+
+                None
+            }
+            Err(NoSolution) => Some(PathKind::Inductive),
+        }
     }
 
-    fn on_stack_overflow(cx: I, input: CanonicalInput<I>) -> QueryResult<I> {
+    fn stack_overflow_result(cx: I, input: CanonicalInput<I>) -> QueryResult<I> {
         response_no_constraints(cx, input, Certainty::overflow(true))
     }
 
-    fn on_fixpoint_overflow(cx: I, input: CanonicalInput<I>) -> QueryResult<I> {
+    fn fixpoint_overflow_result(cx: I, input: CanonicalInput<I>) -> QueryResult<I> {
         response_no_constraints(cx, input, Certainty::overflow(false))
     }
 
diff --git a/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs b/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
index 3974114e9b4..e790ecd595b 100644
--- a/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
+++ b/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
@@ -369,18 +369,16 @@ where
                     return ecx.forced_ambiguity(MaybeCause::Ambiguity);
                 }
             };
+        let (inputs, output) = ecx.instantiate_binder_with_infer(tupled_inputs_and_output);
 
         // A built-in `Fn` impl only holds if the output is sized.
         // (FIXME: technically we only need to check this if the type is a fn ptr...)
-        let output_is_sized_pred = tupled_inputs_and_output.map_bound(|(_, output)| {
-            ty::TraitRef::new(cx, cx.require_trait_lang_item(SolverTraitLangItem::Sized), [output])
-        });
+        let output_is_sized_pred =
+            ty::TraitRef::new(cx, cx.require_trait_lang_item(SolverTraitLangItem::Sized), [output]);
 
-        let pred = tupled_inputs_and_output
-            .map_bound(|(inputs, _)| {
-                ty::TraitRef::new(cx, goal.predicate.def_id(), [goal.predicate.self_ty(), inputs])
-            })
-            .upcast(cx);
+        let pred =
+            ty::TraitRef::new(cx, goal.predicate.def_id(), [goal.predicate.self_ty(), inputs])
+                .upcast(cx);
         Self::probe_and_consider_implied_clause(
             ecx,
             CandidateSource::BuiltinImpl(BuiltinImplSource::Misc),
@@ -408,28 +406,26 @@ where
                 // This region doesn't matter because we're throwing away the coroutine type
                 Region::new_static(cx),
             )?;
+        let AsyncCallableRelevantTypes {
+            tupled_inputs_ty,
+            output_coroutine_ty,
+            coroutine_return_ty: _,
+        } = ecx.instantiate_binder_with_infer(tupled_inputs_and_output_and_coroutine);
 
         // A built-in `AsyncFn` impl only holds if the output is sized.
         // (FIXME: technically we only need to check this if the type is a fn ptr...)
-        let output_is_sized_pred = tupled_inputs_and_output_and_coroutine.map_bound(
-            |AsyncCallableRelevantTypes { output_coroutine_ty, .. }| {
-                ty::TraitRef::new(
-                    cx,
-                    cx.require_trait_lang_item(SolverTraitLangItem::Sized),
-                    [output_coroutine_ty],
-                )
-            },
+        let output_is_sized_pred = ty::TraitRef::new(
+            cx,
+            cx.require_trait_lang_item(SolverTraitLangItem::Sized),
+            [output_coroutine_ty],
         );
 
-        let pred = tupled_inputs_and_output_and_coroutine
-            .map_bound(|AsyncCallableRelevantTypes { tupled_inputs_ty, .. }| {
-                ty::TraitRef::new(
-                    cx,
-                    goal.predicate.def_id(),
-                    [goal.predicate.self_ty(), tupled_inputs_ty],
-                )
-            })
-            .upcast(cx);
+        let pred = ty::TraitRef::new(
+            cx,
+            goal.predicate.def_id(),
+            [goal.predicate.self_ty(), tupled_inputs_ty],
+        )
+        .upcast(cx);
         Self::probe_and_consider_implied_clause(
             ecx,
             CandidateSource::BuiltinImpl(BuiltinImplSource::Misc),
diff --git a/compiler/rustc_parse/src/lib.rs b/compiler/rustc_parse/src/lib.rs
index 88b67d792de..c26c7b9122a 100644
--- a/compiler/rustc_parse/src/lib.rs
+++ b/compiler/rustc_parse/src/lib.rs
@@ -9,6 +9,7 @@
 #![feature(default_field_values)]
 #![feature(if_let_guard)]
 #![feature(iter_intersperse)]
+#![feature(iter_order_by)]
 #![recursion_limit = "256"]
 // tidy-alphabetical-end
 
diff --git a/compiler/rustc_parse/src/parser/tokenstream/tests.rs b/compiler/rustc_parse/src/parser/tokenstream/tests.rs
index 19b2c98f5af..63177a72744 100644
--- a/compiler/rustc_parse/src/parser/tokenstream/tests.rs
+++ b/compiler/rustc_parse/src/parser/tokenstream/tests.rs
@@ -15,7 +15,7 @@ fn sp(a: u32, b: u32) -> Span {
 }
 
 fn cmp_token_stream(a: &TokenStream, b: &TokenStream) -> bool {
-    a.len() == b.len() && a.iter().zip(b.iter()).all(|(x, y)| x.eq_unspanned(y))
+    a.iter().eq_by(b.iter(), |x, y| x.eq_unspanned(y))
 }
 
 #[test]
diff --git a/compiler/rustc_passes/messages.ftl b/compiler/rustc_passes/messages.ftl
index 6cd68380e46..df4016dfa1b 100644
--- a/compiler/rustc_passes/messages.ftl
+++ b/compiler/rustc_passes/messages.ftl
@@ -93,15 +93,6 @@ passes_dead_codes =
        }
     } never {$participle}
 
-passes_debug_visualizer_invalid =
-    invalid argument
-    .note_1 = expected: `natvis_file = "..."`
-    .note_2 = OR
-    .note_3 = expected: `gdb_script_file = "..."`
-
-passes_debug_visualizer_placement =
-    attribute should be applied to a module
-
 passes_debug_visualizer_unreadable =
     couldn't read {$file}: {$error}
 
@@ -149,8 +140,17 @@ passes_doc_attribute_not_attribute =
     nonexistent builtin attribute `{$attribute}` used in `#[doc(attribute = "...")]`
     .help = only existing builtin attributes are allowed in core/std
 
-passes_doc_cfg_hide_takes_list =
-    `#[doc(cfg_hide(...))]` takes a list of attributes
+passes_doc_auto_cfg_expects_hide_or_show =
+    only `hide` or `show` are allowed in `#[doc(auto_cfg(...))]`
+
+passes_doc_auto_cfg_hide_show_expects_list =
+    `#![doc(auto_cfg({$attr_name}(...)))]` expects a list of items
+
+passes_doc_auto_cfg_hide_show_unexpected_item =
+    `#![doc(auto_cfg({$attr_name}(...)))]` only accepts identifiers or key/value items
+
+passes_doc_auto_cfg_wrong_literal =
+    expected boolean for `#[doc(auto_cfg = ...)]`
 
 passes_doc_expect_str =
     doc {$attr_name} attribute expects a string: #[doc({$attr_name} = "a")]
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index aef123c3721..4ea237cfa03 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -10,7 +10,7 @@ use std::collections::hash_map::Entry;
 use std::slice;
 
 use rustc_abi::{Align, ExternAbi, Size};
-use rustc_ast::{AttrStyle, LitKind, MetaItemInner, MetaItemKind, ast};
+use rustc_ast::{AttrStyle, LitKind, MetaItem, MetaItemInner, MetaItemKind, ast};
 use rustc_attr_parsing::{AttributeParser, Late};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::{Applicability, DiagCtxtHandle, IntoDiagArg, MultiSpan, StashKey};
@@ -282,6 +282,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                     | AttributeKind::ObjcClass { .. }
                     | AttributeKind::ObjcSelector { .. }
                     | AttributeKind::RustcCoherenceIsCore(..)
+                    | AttributeKind::DebuggerVisualizer(..)
                 ) => { /* do nothing  */ }
                 Attribute::Unparsed(attr_item) => {
                     style = Some(attr_item.style);
@@ -302,7 +303,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                             &mut doc_aliases,
                         ),
                         [sym::no_link, ..] => self.check_no_link(hir_id, attr, span, target),
-                        [sym::debugger_visualizer, ..] => self.check_debugger_visualizer(attr, target),
                         [sym::rustc_no_implicit_autorefs, ..] => {
                             self.check_applied_to_fn_or_method(hir_id, attr.span(), span, target)
                         }
@@ -1160,16 +1160,59 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
         }
     }
 
-    /// Check that the `#![doc(cfg_hide(...))]` attribute only contains a list of attributes.
-    ///
-    fn check_doc_cfg_hide(&self, meta: &MetaItemInner, hir_id: HirId) {
-        if meta.meta_item_list().is_none() {
-            self.tcx.emit_node_span_lint(
-                INVALID_DOC_ATTRIBUTES,
-                hir_id,
-                meta.span(),
-                errors::DocCfgHideTakesList,
-            );
+    /// Check that the `#![doc(auto_cfg)]` attribute has the expected input.
+    fn check_doc_auto_cfg(&self, meta: &MetaItem, hir_id: HirId) {
+        match &meta.kind {
+            MetaItemKind::Word => {}
+            MetaItemKind::NameValue(lit) => {
+                if !matches!(lit.kind, LitKind::Bool(_)) {
+                    self.tcx.emit_node_span_lint(
+                        INVALID_DOC_ATTRIBUTES,
+                        hir_id,
+                        meta.span,
+                        errors::DocAutoCfgWrongLiteral,
+                    );
+                }
+            }
+            MetaItemKind::List(list) => {
+                for item in list {
+                    let Some(attr_name @ (sym::hide | sym::show)) = item.name() else {
+                        self.tcx.emit_node_span_lint(
+                            INVALID_DOC_ATTRIBUTES,
+                            hir_id,
+                            meta.span,
+                            errors::DocAutoCfgExpectsHideOrShow,
+                        );
+                        continue;
+                    };
+                    if let Some(list) = item.meta_item_list() {
+                        for item in list {
+                            let valid = item.meta_item().is_some_and(|meta| {
+                                meta.path.segments.len() == 1
+                                    && matches!(
+                                        &meta.kind,
+                                        MetaItemKind::Word | MetaItemKind::NameValue(_)
+                                    )
+                            });
+                            if !valid {
+                                self.tcx.emit_node_span_lint(
+                                    INVALID_DOC_ATTRIBUTES,
+                                    hir_id,
+                                    item.span(),
+                                    errors::DocAutoCfgHideShowUnexpectedItem { attr_name },
+                                );
+                            }
+                        }
+                    } else {
+                        self.tcx.emit_node_span_lint(
+                            INVALID_DOC_ATTRIBUTES,
+                            hir_id,
+                            meta.span,
+                            errors::DocAutoCfgHideShowExpectsList { attr_name },
+                        );
+                    }
+                }
+            }
         }
     }
 
@@ -1245,10 +1288,8 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                             self.check_attr_crate_level(attr, style, meta, hir_id);
                         }
 
-                        Some(sym::cfg_hide) => {
-                            if self.check_attr_crate_level(attr, style, meta, hir_id) {
-                                self.check_doc_cfg_hide(meta, hir_id);
-                            }
+                        Some(sym::auto_cfg) => {
+                            self.check_doc_auto_cfg(i_meta, hir_id);
                         }
 
                         Some(sym::inline | sym::no_inline) => {
@@ -1783,20 +1824,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
         }
     }
 
-    /// Checks if the items on the `#[debugger_visualizer]` attribute are valid.
-    fn check_debugger_visualizer(&self, attr: &Attribute, target: Target) {
-        // Here we only check that the #[debugger_visualizer] attribute is attached
-        // to nothing other than a module. All other checks are done in the
-        // `debugger_visualizer` query where they need to be done for decoding
-        // anyway.
-        match target {
-            Target::Mod => {}
-            _ => {
-                self.dcx().emit_err(errors::DebugVisualizerPlacement { span: attr.span() });
-            }
-        }
-    }
-
     /// Outputs an error for `#[allow_internal_unstable]` which can only be applied to macros.
     /// (Allows proc_macro functions)
     fn check_rustc_allow_const_fn_unstable(
diff --git a/compiler/rustc_passes/src/debugger_visualizer.rs b/compiler/rustc_passes/src/debugger_visualizer.rs
index 7a7a8175e55..7211f3cf85b 100644
--- a/compiler/rustc_passes/src/debugger_visualizer.rs
+++ b/compiler/rustc_passes/src/debugger_visualizer.rs
@@ -1,67 +1,60 @@
 //! Detecting usage of the `#[debugger_visualizer]` attribute.
 
-use rustc_ast::Attribute;
+use rustc_ast::ast::NodeId;
+use rustc_ast::{HasNodeId, ItemKind, ast};
+use rustc_attr_parsing::AttributeParser;
 use rustc_expand::base::resolve_path;
-use rustc_middle::middle::debugger_visualizer::{DebuggerVisualizerFile, DebuggerVisualizerType};
+use rustc_hir::Attribute;
+use rustc_hir::attrs::{AttributeKind, DebugVisualizer};
+use rustc_middle::middle::debugger_visualizer::DebuggerVisualizerFile;
 use rustc_middle::query::{LocalCrate, Providers};
 use rustc_middle::ty::TyCtxt;
 use rustc_session::Session;
-use rustc_span::sym;
+use rustc_span::{DUMMY_SP, Span, sym};
 
-use crate::errors::{DebugVisualizerInvalid, DebugVisualizerUnreadable};
+use crate::errors::DebugVisualizerUnreadable;
 
 impl DebuggerVisualizerCollector<'_> {
-    fn check_for_debugger_visualizer(&mut self, attr: &Attribute) {
-        if attr.has_name(sym::debugger_visualizer) {
-            let Some(hints) = attr.meta_item_list() else {
-                self.sess.dcx().emit_err(DebugVisualizerInvalid { span: attr.span });
-                return;
-            };
+    fn check_for_debugger_visualizer(
+        &mut self,
+        attrs: &[ast::Attribute],
+        span: Span,
+        node_id: NodeId,
+    ) {
+        if let Some(Attribute::Parsed(AttributeKind::DebuggerVisualizer(visualizers))) =
+            AttributeParser::parse_limited(
+                &self.sess,
+                attrs,
+                sym::debugger_visualizer,
+                span,
+                node_id,
+                None,
+            )
+        {
+            for DebugVisualizer { span, visualizer_type, path } in visualizers {
+                let file = match resolve_path(&self.sess, path.as_str(), span) {
+                    Ok(file) => file,
+                    Err(err) => {
+                        err.emit();
+                        return;
+                    }
+                };
 
-            let [hint] = hints.as_slice() else {
-                self.sess.dcx().emit_err(DebugVisualizerInvalid { span: attr.span });
-                return;
-            };
-
-            let Some(meta_item) = hint.meta_item() else {
-                self.sess.dcx().emit_err(DebugVisualizerInvalid { span: attr.span });
-                return;
-            };
-
-            let (visualizer_type, visualizer_path) = match (meta_item.name(), meta_item.value_str())
-            {
-                (Some(sym::natvis_file), Some(value)) => (DebuggerVisualizerType::Natvis, value),
-                (Some(sym::gdb_script_file), Some(value)) => {
-                    (DebuggerVisualizerType::GdbPrettyPrinter, value)
-                }
-                (_, _) => {
-                    self.sess.dcx().emit_err(DebugVisualizerInvalid { span: meta_item.span });
-                    return;
-                }
-            };
-
-            let file = match resolve_path(&self.sess, visualizer_path.as_str(), attr.span) {
-                Ok(file) => file,
-                Err(err) => {
-                    err.emit();
-                    return;
-                }
-            };
-
-            match self.sess.source_map().load_binary_file(&file) {
-                Ok((source, _)) => {
-                    self.visualizers.push(DebuggerVisualizerFile::new(
-                        source,
-                        visualizer_type,
-                        file,
-                    ));
-                }
-                Err(error) => {
-                    self.sess.dcx().emit_err(DebugVisualizerUnreadable {
-                        span: meta_item.span,
-                        file: &file,
-                        error,
-                    });
+                match self.sess.source_map().load_binary_file(&file) {
+                    Ok((source, _)) => {
+                        self.visualizers.push(DebuggerVisualizerFile::new(
+                            source,
+                            visualizer_type,
+                            file,
+                        ));
+                    }
+                    Err(error) => {
+                        self.sess.dcx().emit_err(DebugVisualizerUnreadable {
+                            span,
+                            file: &file,
+                            error,
+                        });
+                    }
                 }
             }
         }
@@ -74,9 +67,15 @@ struct DebuggerVisualizerCollector<'a> {
 }
 
 impl<'ast> rustc_ast::visit::Visitor<'ast> for DebuggerVisualizerCollector<'_> {
-    fn visit_attribute(&mut self, attr: &'ast Attribute) {
-        self.check_for_debugger_visualizer(attr);
-        rustc_ast::visit::walk_attribute(self, attr);
+    fn visit_item(&mut self, item: &'ast rustc_ast::Item) -> Self::Result {
+        if let ItemKind::Mod(..) = item.kind {
+            self.check_for_debugger_visualizer(&item.attrs, item.span, item.node_id());
+        }
+        rustc_ast::visit::walk_item(self, item);
+    }
+    fn visit_crate(&mut self, krate: &'ast ast::Crate) -> Self::Result {
+        self.check_for_debugger_visualizer(&krate.attrs, DUMMY_SP, krate.id);
+        rustc_ast::visit::walk_crate(self, krate);
     }
 }
 
diff --git a/compiler/rustc_passes/src/errors.rs b/compiler/rustc_passes/src/errors.rs
index cd8935f6b2f..f0726014e0a 100644
--- a/compiler/rustc_passes/src/errors.rs
+++ b/compiler/rustc_passes/src/errors.rs
@@ -309,8 +309,24 @@ pub(crate) struct DocTestLiteral;
 pub(crate) struct DocTestTakesList;
 
 #[derive(LintDiagnostic)]
-#[diag(passes_doc_cfg_hide_takes_list)]
-pub(crate) struct DocCfgHideTakesList;
+#[diag(passes_doc_auto_cfg_wrong_literal)]
+pub(crate) struct DocAutoCfgWrongLiteral;
+
+#[derive(LintDiagnostic)]
+#[diag(passes_doc_auto_cfg_expects_hide_or_show)]
+pub(crate) struct DocAutoCfgExpectsHideOrShow;
+
+#[derive(LintDiagnostic)]
+#[diag(passes_doc_auto_cfg_hide_show_expects_list)]
+pub(crate) struct DocAutoCfgHideShowExpectsList {
+    pub attr_name: Symbol,
+}
+
+#[derive(LintDiagnostic)]
+#[diag(passes_doc_auto_cfg_hide_show_unexpected_item)]
+pub(crate) struct DocAutoCfgHideShowUnexpectedItem {
+    pub attr_name: Symbol,
+}
 
 #[derive(LintDiagnostic)]
 #[diag(passes_doc_test_unknown_any)]
@@ -476,23 +492,6 @@ pub(crate) struct MacroOnlyAttribute {
 }
 
 #[derive(Diagnostic)]
-#[diag(passes_debug_visualizer_placement)]
-pub(crate) struct DebugVisualizerPlacement {
-    #[primary_span]
-    pub span: Span,
-}
-
-#[derive(Diagnostic)]
-#[diag(passes_debug_visualizer_invalid)]
-#[note(passes_note_1)]
-#[note(passes_note_2)]
-#[note(passes_note_3)]
-pub(crate) struct DebugVisualizerInvalid {
-    #[primary_span]
-    pub span: Span,
-}
-
-#[derive(Diagnostic)]
 #[diag(passes_debug_visualizer_unreadable)]
 pub(crate) struct DebugVisualizerUnreadable<'a> {
     #[primary_span]
diff --git a/compiler/rustc_pattern_analysis/src/rustc.rs b/compiler/rustc_pattern_analysis/src/rustc.rs
index d9f8085083e..0652461e975 100644
--- a/compiler/rustc_pattern_analysis/src/rustc.rs
+++ b/compiler/rustc_pattern_analysis/src/rustc.rs
@@ -120,7 +120,7 @@ impl<'p, 'tcx: 'p> fmt::Debug for RustcPatCtxt<'p, 'tcx> {
 impl<'p, 'tcx: 'p> RustcPatCtxt<'p, 'tcx> {
     /// Type inference occasionally gives us opaque types in places where corresponding patterns
     /// have more specific types. To avoid inconsistencies as well as detect opaque uninhabited
-    /// types, we use the corresponding concrete type if possible.
+    /// types, we use the corresponding hidden type if possible.
     // FIXME(#132279): This will be unnecessary once we have a TypingMode which supports revealing
     // opaque types defined in a body.
     #[inline]
@@ -146,7 +146,7 @@ impl<'p, 'tcx: 'p> RustcPatCtxt<'p, 'tcx> {
     /// know it.
     fn reveal_opaque_key(&self, key: OpaqueTypeKey<'tcx>) -> Option<Ty<'tcx>> {
         self.typeck_results
-            .concrete_opaque_types
+            .hidden_types
             .get(&key.def_id)
             .map(|x| ty::EarlyBinder::bind(x.ty).instantiate(self.tcx, key.args))
     }
diff --git a/compiler/rustc_privacy/src/lib.rs b/compiler/rustc_privacy/src/lib.rs
index 1bddbd03cc3..c9dbb204f61 100644
--- a/compiler/rustc_privacy/src/lib.rs
+++ b/compiler/rustc_privacy/src/lib.rs
@@ -45,7 +45,7 @@ use tracing::debug;
 rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
 
 ////////////////////////////////////////////////////////////////////////////////
-/// Generic infrastructure used to implement specific visitors below.
+// Generic infrastructure used to implement specific visitors below.
 ////////////////////////////////////////////////////////////////////////////////
 
 struct LazyDefPathStr<'tcx> {
@@ -309,10 +309,7 @@ fn min(vis1: ty::Visibility, vis2: ty::Visibility, tcx: TyCtxt<'_>) -> ty::Visib
     if vis1.is_at_least(vis2, tcx) { vis2 } else { vis1 }
 }
 
-////////////////////////////////////////////////////////////////////////////////
 /// Visitor used to determine impl visibility and reachability.
-////////////////////////////////////////////////////////////////////////////////
-
 struct FindMin<'a, 'tcx, VL: VisibilityLike, const SHALLOW: bool> {
     tcx: TyCtxt<'tcx>,
     effective_visibilities: &'a EffectiveVisibilities,
@@ -387,10 +384,7 @@ impl VisibilityLike for EffectiveVisibility {
     }
 }
 
-////////////////////////////////////////////////////////////////////////////////
 /// The embargo visitor, used to determine the exports of the AST.
-////////////////////////////////////////////////////////////////////////////////
-
 struct EmbargoVisitor<'tcx> {
     tcx: TyCtxt<'tcx>,
 
@@ -849,9 +843,7 @@ impl<'tcx> DefIdVisitor<'tcx> for ReachEverythingInTheInterfaceVisitor<'_, 'tcx>
     }
 }
 
-////////////////////////////////////////////////////////////////////////////////
 /// Visitor, used for EffectiveVisibilities table checking
-////////////////////////////////////////////////////////////////////////////////
 pub struct TestReachabilityVisitor<'a, 'tcx> {
     tcx: TyCtxt<'tcx>,
     effective_visibilities: &'a EffectiveVisibilities,
@@ -909,13 +901,11 @@ impl<'a, 'tcx> TestReachabilityVisitor<'a, 'tcx> {
     }
 }
 
-//////////////////////////////////////////////////////////////////////////////////////
 /// Name privacy visitor, checks privacy and reports violations.
+///
 /// Most of name privacy checks are performed during the main resolution phase,
 /// or later in type checking when field accesses and associated items are resolved.
 /// This pass performs remaining checks for fields in struct expressions and patterns.
-//////////////////////////////////////////////////////////////////////////////////////
-
 struct NamePrivacyVisitor<'tcx> {
     tcx: TyCtxt<'tcx>,
     maybe_typeck_results: Option<&'tcx ty::TypeckResults<'tcx>>,
@@ -1120,12 +1110,10 @@ impl<'tcx> Visitor<'tcx> for NamePrivacyVisitor<'tcx> {
     }
 }
 
-////////////////////////////////////////////////////////////////////////////////////////////
 /// Type privacy visitor, checks types for privacy and reports violations.
+///
 /// Both explicitly written types and inferred types of expressions and patterns are checked.
 /// Checks are performed on "semantic" types regardless of names and their hygiene.
-////////////////////////////////////////////////////////////////////////////////////////////
-
 struct TypePrivacyVisitor<'tcx> {
     tcx: TyCtxt<'tcx>,
     module_def_id: LocalModDefId,
@@ -1345,13 +1333,11 @@ impl<'tcx> DefIdVisitor<'tcx> for TypePrivacyVisitor<'tcx> {
     }
 }
 
-///////////////////////////////////////////////////////////////////////////////
 /// SearchInterfaceForPrivateItemsVisitor traverses an item's interface and
 /// finds any private components in it.
+///
 /// PrivateItemsInPublicInterfacesVisitor ensures there are no private types
 /// and traits in public interfaces.
-///////////////////////////////////////////////////////////////////////////////
-
 struct SearchInterfaceForPrivateItemsVisitor<'tcx> {
     tcx: TyCtxt<'tcx>,
     item_def_id: LocalDefId,
diff --git a/compiler/rustc_resolve/src/build_reduced_graph.rs b/compiler/rustc_resolve/src/build_reduced_graph.rs
index fa3c06059b3..c10b6ca7e71 100644
--- a/compiler/rustc_resolve/src/build_reduced_graph.rs
+++ b/compiler/rustc_resolve/src/build_reduced_graph.rs
@@ -5,7 +5,6 @@
 //! unexpanded macros in the fragment are visited and registered.
 //! Imports are also considered items and placed into modules here, but not resolved yet.
 
-use std::cell::Cell;
 use std::sync::Arc;
 
 use rustc_ast::visit::{self, AssocCtxt, Visitor, WalkItemKind};
@@ -35,6 +34,7 @@ use crate::Namespace::{MacroNS, TypeNS, ValueNS};
 use crate::def_collector::collect_definitions;
 use crate::imports::{ImportData, ImportKind};
 use crate::macros::{MacroRulesBinding, MacroRulesScope, MacroRulesScopeRef};
+use crate::ref_mut::CmCell;
 use crate::{
     BindingKey, ExternPreludeEntry, Finalize, MacroData, Module, ModuleKind, ModuleOrUniformRoot,
     NameBinding, ParentScope, PathResult, ResolutionError, Resolver, Segment, Used,
@@ -87,7 +87,8 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         // because they can be fetched by glob imports from those modules, and bring traits
         // into scope both directly and through glob imports.
         let key = BindingKey::new_disambiguated(ident, ns, || {
-            parent.underscore_disambiguator.update(|d| d + 1);
+            // FIXME(batched): Will be fixed in batched resolution.
+            parent.underscore_disambiguator.update_unchecked(|d| d + 1);
             parent.underscore_disambiguator.get()
         });
         if self
@@ -477,7 +478,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
             kind,
             parent_scope: self.parent_scope,
             module_path,
-            imported_module: Cell::new(None),
+            imported_module: CmCell::new(None),
             span,
             use_span: item.span,
             use_span_with_attributes: item.span_with_attributes(),
@@ -505,7 +506,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
                     });
                 }
             }
-            ImportKind::Glob { .. } => current_module.globs.borrow_mut().push(import),
+            ImportKind::Glob { .. } => current_module.globs.borrow_mut(self.r).push(import),
             _ => unreachable!(),
         }
     }
@@ -668,7 +669,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
             }
             ast::UseTreeKind::Glob => {
                 if !ast::attr::contains_name(&item.attrs, sym::prelude_import) {
-                    let kind = ImportKind::Glob { max_vis: Cell::new(None), id };
+                    let kind = ImportKind::Glob { max_vis: CmCell::new(None), id };
                     self.add_import(prefix, kind, use_tree.span, item, root_span, item.id, vis);
                 } else {
                     // Resolve the prelude import early.
@@ -971,7 +972,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
             kind: ImportKind::ExternCrate { source: orig_name, target: ident, id: item.id },
             root_id: item.id,
             parent_scope: self.parent_scope,
-            imported_module: Cell::new(module),
+            imported_module: CmCell::new(module),
             has_attributes: !item.attrs.is_empty(),
             use_span_with_attributes: item.span_with_attributes(),
             use_span: item.span,
@@ -1103,7 +1104,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
                 kind: ImportKind::MacroUse { warn_private },
                 root_id: item.id,
                 parent_scope: this.parent_scope,
-                imported_module: Cell::new(Some(ModuleOrUniformRoot::Module(module))),
+                imported_module: CmCell::new(Some(ModuleOrUniformRoot::Module(module))),
                 use_span_with_attributes: item.span_with_attributes(),
                 has_attributes: !item.attrs.is_empty(),
                 use_span: item.span,
@@ -1196,7 +1197,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
     /// directly into its parent scope's module.
     fn visit_invoc_in_module(&mut self, id: NodeId) -> MacroRulesScopeRef<'ra> {
         let invoc_id = self.visit_invoc(id);
-        self.parent_scope.module.unexpanded_invocations.borrow_mut().insert(invoc_id);
+        self.parent_scope.module.unexpanded_invocations.borrow_mut(self.r).insert(invoc_id);
         self.r.arenas.alloc_macro_rules_scope(MacroRulesScope::Invocation(invoc_id))
     }
 
@@ -1274,7 +1275,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
                     kind: ImportKind::MacroExport,
                     root_id: item.id,
                     parent_scope: self.parent_scope,
-                    imported_module: Cell::new(None),
+                    imported_module: CmCell::new(None),
                     has_attributes: false,
                     use_span_with_attributes: span,
                     use_span: span,
diff --git a/compiler/rustc_resolve/src/ident.rs b/compiler/rustc_resolve/src/ident.rs
index 35051675fd8..4415300777f 100644
--- a/compiler/rustc_resolve/src/ident.rs
+++ b/compiler/rustc_resolve/src/ident.rs
@@ -492,14 +492,13 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                         _ => Err(Determinacy::Determined),
                     },
                     Scope::Module(module, derive_fallback_lint_id) => {
-                        // FIXME: use `finalize_scope` here.
                         let (adjusted_parent_scope, adjusted_finalize) =
                             if matches!(scope_set, ScopeSet::ModuleAndExternPrelude(..)) {
-                                (parent_scope, finalize)
+                                (parent_scope, finalize_scope!())
                             } else {
                                 (
                                     &ParentScope { module, ..*parent_scope },
-                                    finalize.map(|f| Finalize { used: Used::Scope, ..f }),
+                                    finalize_scope!().map(|f| Finalize { used: Used::Scope, ..f }),
                                 )
                             };
                         let binding = this.reborrow().resolve_ident_in_module_unadjusted(
@@ -557,8 +556,10 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                         None => Err(Determinacy::Determined),
                     },
                     Scope::ExternPreludeItems => {
-                        // FIXME: use `finalize_scope` here.
-                        match this.reborrow().extern_prelude_get_item(ident, finalize.is_some()) {
+                        match this
+                            .reborrow()
+                            .extern_prelude_get_item(ident, finalize_scope!().is_some())
+                        {
                             Some(binding) => {
                                 extern_prelude_item_binding = Some(binding);
                                 Ok((binding, Flags::empty()))
@@ -900,6 +901,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 binding,
                 if resolution.non_glob_binding.is_some() { resolution.glob_binding } else { None },
                 parent_scope,
+                module,
                 finalize,
                 shadowing,
             );
@@ -1024,6 +1026,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         binding: Option<NameBinding<'ra>>,
         shadowed_glob: Option<NameBinding<'ra>>,
         parent_scope: &ParentScope<'ra>,
+        module: Module<'ra>,
         finalize: Finalize,
         shadowing: Shadowing,
     ) -> Result<NameBinding<'ra>, (Determinacy, Weak)> {
@@ -1075,6 +1078,37 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             self.macro_expanded_macro_export_errors.insert((path_span, binding.span));
         }
 
+        // If we encounter a re-export for a type with private fields, it will not be able to
+        // be constructed through this re-export. We track that case here to expand later
+        // privacy errors with appropriate information.
+        if let Res::Def(_, def_id) = binding.res() {
+            let struct_ctor = match def_id.as_local() {
+                Some(def_id) => self.struct_constructors.get(&def_id).cloned(),
+                None => {
+                    let ctor = self.cstore().ctor_untracked(def_id);
+                    ctor.map(|(ctor_kind, ctor_def_id)| {
+                        let ctor_res = Res::Def(
+                            DefKind::Ctor(rustc_hir::def::CtorOf::Struct, ctor_kind),
+                            ctor_def_id,
+                        );
+                        let ctor_vis = self.tcx.visibility(ctor_def_id);
+                        let field_visibilities = self
+                            .tcx
+                            .associated_item_def_ids(def_id)
+                            .iter()
+                            .map(|field_id| self.tcx.visibility(field_id))
+                            .collect();
+                        (ctor_res, ctor_vis, field_visibilities)
+                    })
+                }
+            };
+            if let Some((_, _, fields)) = struct_ctor
+                && fields.iter().any(|vis| !self.is_accessible_from(*vis, module))
+            {
+                self.inaccessible_ctor_reexport.insert(path_span, binding.span);
+            }
+        }
+
         self.record_use(ident, binding, used);
         return Ok(binding);
     }
diff --git a/compiler/rustc_resolve/src/imports.rs b/compiler/rustc_resolve/src/imports.rs
index 33c2c7436d1..ce90a1bcd31 100644
--- a/compiler/rustc_resolve/src/imports.rs
+++ b/compiler/rustc_resolve/src/imports.rs
@@ -1,6 +1,5 @@
 //! A bunch of methods and structures more or less related to resolving imports.
 
-use std::cell::Cell;
 use std::mem;
 
 use rustc_ast::NodeId;
@@ -32,6 +31,7 @@ use crate::errors::{
     CannotBeReexportedPrivateNS, CannotDetermineImportResolution, CannotGlobImportAllCrates,
     ConsiderAddingMacroExport, ConsiderMarkingAsPub, ConsiderMarkingAsPubCrate,
 };
+use crate::ref_mut::CmCell;
 use crate::{
     AmbiguityError, AmbiguityKind, BindingKey, CmResolver, Determinacy, Finalize, ImportSuggestion,
     Module, ModuleOrUniformRoot, NameBinding, NameBindingData, NameBindingKind, ParentScope,
@@ -68,7 +68,7 @@ pub(crate) enum ImportKind<'ra> {
         /// It will directly use `source` when the format is `use prefix::source`.
         target: Ident,
         /// Bindings introduced by the import.
-        bindings: PerNS<Cell<PendingBinding<'ra>>>,
+        bindings: PerNS<CmCell<PendingBinding<'ra>>>,
         /// `true` for `...::{self [as target]}` imports, `false` otherwise.
         type_ns_only: bool,
         /// Did this import result from a nested import? ie. `use foo::{bar, baz};`
@@ -89,7 +89,7 @@ pub(crate) enum ImportKind<'ra> {
     Glob {
         // The visibility of the greatest re-export.
         // n.b. `max_vis` is only used in `finalize_import` to check for re-export errors.
-        max_vis: Cell<Option<Visibility>>,
+        max_vis: CmCell<Option<Visibility>>,
         id: NodeId,
     },
     ExternCrate {
@@ -182,7 +182,7 @@ pub(crate) struct ImportData<'ra> {
     /// |`use ::foo`      | `ModuleOrUniformRoot::ExternPrelude`          | 2018+ editions |
     /// |`use ::foo`      | `ModuleOrUniformRoot::ModuleAndExternPrelude` | a special case in 2015 edition |
     /// |`use foo`        | `ModuleOrUniformRoot::CurrentScope`           | - |
-    pub imported_module: Cell<Option<ModuleOrUniformRoot<'ra>>>,
+    pub imported_module: CmCell<Option<ModuleOrUniformRoot<'ra>>>,
     pub vis: Visibility,
 
     /// Span of the visibility.
@@ -320,7 +320,8 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             && (vis == import_vis
                 || max_vis.get().is_none_or(|max_vis| vis.is_at_least(max_vis, self.tcx)))
         {
-            max_vis.set(Some(vis.expect_local()))
+            // FIXME(batched): Will be fixed in batched import resolution.
+            max_vis.set_unchecked(Some(vis.expect_local()))
         }
 
         self.arenas.alloc_name_binding(NameBindingData {
@@ -349,7 +350,8 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         // because they can be fetched by glob imports from those modules, and bring traits
         // into scope both directly and through glob imports.
         let key = BindingKey::new_disambiguated(ident, ns, || {
-            module.underscore_disambiguator.update(|d| d + 1);
+            // FIXME(batched): Will be fixed in batched resolution.
+            module.underscore_disambiguator.update_unchecked(|d| d + 1);
             module.underscore_disambiguator.get()
         });
         self.update_local_resolution(module, key, warn_ambiguity, |this, resolution| {
@@ -482,7 +484,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             }
         };
 
-        let Ok(glob_importers) = module.glob_importers.try_borrow_mut() else {
+        let Ok(glob_importers) = module.glob_importers.try_borrow_mut_unchecked() else {
             return t;
         };
 
@@ -862,7 +864,8 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             }
         };
 
-        import.imported_module.set(Some(module));
+        // FIXME(batched): Will be fixed in batched import resolution.
+        import.imported_module.set_unchecked(Some(module));
         let (source, target, bindings, type_ns_only) = match import.kind {
             ImportKind::Single { source, target, ref bindings, type_ns_only, .. } => {
                 (source, target, bindings, type_ns_only)
@@ -937,7 +940,8 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                         PendingBinding::Pending
                     }
                 };
-                bindings[ns].set(binding);
+                // FIXME(batched): Will be fixed in batched import resolution.
+                bindings[ns].set_unchecked(binding);
             }
         });
 
@@ -1508,7 +1512,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         }
 
         // Add to module's glob_importers
-        module.glob_importers.borrow_mut().push(import);
+        module.glob_importers.borrow_mut_unchecked().push(import);
 
         // Ensure that `resolutions` isn't borrowed during `try_define`,
         // since it might get updated via a glob cycle.
@@ -1550,7 +1554,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
     // reporting conflicts, and reporting unresolved imports.
     fn finalize_resolutions_in(&mut self, module: Module<'ra>) {
         // Since import resolution is finished, globs will not define any more names.
-        *module.globs.borrow_mut() = Vec::new();
+        *module.globs.borrow_mut(self) = Vec::new();
 
         let Some(def_id) = module.opt_def_id() else { return };
 
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
index 9e3c0938836..8c2ddda7f98 100644
--- a/compiler/rustc_resolve/src/late/diagnostics.rs
+++ b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -1942,44 +1942,77 @@ impl<'ast, 'ra, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                     return true;
                 };
 
+                let update_message =
+                    |this: &mut Self, err: &mut Diag<'_>, source: &PathSource<'_, '_, '_>| {
+                        match source {
+                            // e.g. `if let Enum::TupleVariant(field1, field2) = _`
+                            PathSource::TupleStruct(_, pattern_spans) => {
+                                err.primary_message(
+                                "cannot match against a tuple struct which contains private fields",
+                            );
+
+                                // Use spans of the tuple struct pattern.
+                                Some(Vec::from(*pattern_spans))
+                            }
+                            // e.g. `let _ = Enum::TupleVariant(field1, field2);`
+                            PathSource::Expr(Some(Expr {
+                                kind: ExprKind::Call(path, args),
+                                span: call_span,
+                                ..
+                            })) => {
+                                err.primary_message(
+                                "cannot initialize a tuple struct which contains private fields",
+                            );
+                                this.suggest_alternative_construction_methods(
+                                    def_id,
+                                    err,
+                                    path.span,
+                                    *call_span,
+                                    &args[..],
+                                );
+                                // Use spans of the tuple struct definition.
+                                this.r
+                                    .field_idents(def_id)
+                                    .map(|fields| fields.iter().map(|f| f.span).collect::<Vec<_>>())
+                            }
+                            _ => None,
+                        }
+                    };
                 let is_accessible = self.r.is_accessible_from(ctor_vis, self.parent_scope.module);
+                if let Some(use_span) = self.r.inaccessible_ctor_reexport.get(&span)
+                    && is_accessible
+                {
+                    err.span_note(
+                        *use_span,
+                        "the type is accessed through this re-export, but the type's constructor \
+                         is not visible in this import's scope due to private fields",
+                    );
+                    if is_accessible
+                        && fields
+                            .iter()
+                            .all(|vis| self.r.is_accessible_from(*vis, self.parent_scope.module))
+                    {
+                        err.span_suggestion_verbose(
+                            span,
+                            "the type can be constructed directly, because its fields are \
+                             available from the current scope",
+                            // Using `tcx.def_path_str` causes the compiler to hang.
+                            // We don't need to handle foreign crate types because in that case you
+                            // can't access the ctor either way.
+                            format!(
+                                "crate{}", // The method already has leading `::`.
+                                self.r.tcx.def_path(def_id).to_string_no_crate_verbose(),
+                            ),
+                            Applicability::MachineApplicable,
+                        );
+                    }
+                    update_message(self, err, &source);
+                }
                 if !is_expected(ctor_def) || is_accessible {
                     return true;
                 }
 
-                let field_spans = match source {
-                    // e.g. `if let Enum::TupleVariant(field1, field2) = _`
-                    PathSource::TupleStruct(_, pattern_spans) => {
-                        err.primary_message(
-                            "cannot match against a tuple struct which contains private fields",
-                        );
-
-                        // Use spans of the tuple struct pattern.
-                        Some(Vec::from(pattern_spans))
-                    }
-                    // e.g. `let _ = Enum::TupleVariant(field1, field2);`
-                    PathSource::Expr(Some(Expr {
-                        kind: ExprKind::Call(path, args),
-                        span: call_span,
-                        ..
-                    })) => {
-                        err.primary_message(
-                            "cannot initialize a tuple struct which contains private fields",
-                        );
-                        self.suggest_alternative_construction_methods(
-                            def_id,
-                            err,
-                            path.span,
-                            *call_span,
-                            &args[..],
-                        );
-                        // Use spans of the tuple struct definition.
-                        self.r
-                            .field_idents(def_id)
-                            .map(|fields| fields.iter().map(|f| f.span).collect::<Vec<_>>())
-                    }
-                    _ => None,
-                };
+                let field_spans = update_message(self, err, &source);
 
                 if let Some(spans) =
                     field_spans.filter(|spans| spans.len() > 0 && fields.len() == spans.len())
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
index 8b185ce7ef2..b44b1c966a4 100644
--- a/compiler/rustc_resolve/src/lib.rs
+++ b/compiler/rustc_resolve/src/lib.rs
@@ -19,6 +19,7 @@
 #![feature(default_field_values)]
 #![feature(if_let_guard)]
 #![feature(iter_intersperse)]
+#![feature(ptr_as_ref_unchecked)]
 #![feature(rustc_attrs)]
 #![feature(rustdoc_internals)]
 #![recursion_limit = "256"]
@@ -26,7 +27,7 @@
 
 use std::cell::{Cell, Ref, RefCell};
 use std::collections::BTreeSet;
-use std::fmt;
+use std::fmt::{self};
 use std::sync::Arc;
 
 use diagnostics::{ImportSuggestion, LabelSuggestion, Suggestion};
@@ -95,6 +96,8 @@ pub mod rustdoc;
 
 pub use macros::registered_tools_ast;
 
+use crate::ref_mut::{CmCell, CmRefCell};
+
 rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
 
 #[derive(Debug)]
@@ -592,22 +595,22 @@ struct ModuleData<'ra> {
     /// Resolutions in modules from other crates are not populated until accessed.
     lazy_resolutions: Resolutions<'ra>,
     /// True if this is a module from other crate that needs to be populated on access.
-    populate_on_access: Cell<bool>,
+    populate_on_access: Cell<bool>, // FIXME(parallel): Use an atomic in parallel import resolution
     /// Used to disambiguate underscore items (`const _: T = ...`) in the module.
-    underscore_disambiguator: Cell<u32>,
+    underscore_disambiguator: CmCell<u32>,
 
     /// Macro invocations that can expand into items in this module.
-    unexpanded_invocations: RefCell<FxHashSet<LocalExpnId>>,
+    unexpanded_invocations: CmRefCell<FxHashSet<LocalExpnId>>,
 
     /// Whether `#[no_implicit_prelude]` is active.
     no_implicit_prelude: bool,
 
-    glob_importers: RefCell<Vec<Import<'ra>>>,
-    globs: RefCell<Vec<Import<'ra>>>,
+    glob_importers: CmRefCell<Vec<Import<'ra>>>,
+    globs: CmRefCell<Vec<Import<'ra>>>,
 
     /// Used to memoize the traits in this module for faster searches through all traits in scope.
     traits:
-        RefCell<Option<Box<[(Macros20NormalizedIdent, NameBinding<'ra>, Option<Module<'ra>>)]>>>,
+        CmRefCell<Option<Box<[(Macros20NormalizedIdent, NameBinding<'ra>, Option<Module<'ra>>)]>>>,
 
     /// Span of the module itself. Used for error reporting.
     span: Span,
@@ -656,12 +659,12 @@ impl<'ra> ModuleData<'ra> {
             kind,
             lazy_resolutions: Default::default(),
             populate_on_access: Cell::new(is_foreign),
-            underscore_disambiguator: Cell::new(0),
+            underscore_disambiguator: CmCell::new(0),
             unexpanded_invocations: Default::default(),
             no_implicit_prelude,
-            glob_importers: RefCell::new(Vec::new()),
-            globs: RefCell::new(Vec::new()),
-            traits: RefCell::new(None),
+            glob_importers: CmRefCell::new(Vec::new()),
+            globs: CmRefCell::new(Vec::new()),
+            traits: CmRefCell::new(None),
             span,
             expansion,
             self_binding,
@@ -696,7 +699,7 @@ impl<'ra> Module<'ra> {
 
     /// This modifies `self` in place. The traits will be stored in `self.traits`.
     fn ensure_traits<'tcx>(self, resolver: &impl AsRef<Resolver<'ra, 'tcx>>) {
-        let mut traits = self.traits.borrow_mut();
+        let mut traits = self.traits.borrow_mut(resolver.as_ref());
         if traits.is_none() {
             let mut collected_traits = Vec::new();
             self.for_each_child(resolver, |r, name, ns, binding| {
@@ -1164,6 +1167,11 @@ pub struct Resolver<'ra, 'tcx> {
     /// Crate-local macro expanded `macro_export` referred to by a module-relative path.
     macro_expanded_macro_export_errors: BTreeSet<(Span, Span)> = BTreeSet::new(),
 
+    /// When a type is re-exported that has an inaccessible constructor because it has fields that
+    /// are inaccessible from the import's scope, we mark that as the type won't be able to be built
+    /// through the re-export. We use this information to extend the existing diagnostic.
+    inaccessible_ctor_reexport: FxHashMap<Span, Span>,
+
     arenas: &'ra ResolverArenas<'ra>,
     dummy_binding: NameBinding<'ra>,
     builtin_types_bindings: FxHashMap<Symbol, NameBinding<'ra>>,
@@ -1592,6 +1600,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             glob_map: Default::default(),
             used_imports: FxHashSet::default(),
             maybe_unused_trait_imports: Default::default(),
+            inaccessible_ctor_reexport: Default::default(),
 
             arenas,
             dummy_binding: arenas.new_pub_res_binding(Res::Err, DUMMY_SP, LocalExpnId::ROOT),
@@ -1974,6 +1983,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
 
     fn resolutions(&self, module: Module<'ra>) -> &'ra Resolutions<'ra> {
         if module.populate_on_access.get() {
+            // FIXME(batched): Will be fixed in batched import resolution.
             module.populate_on_access.set(false);
             self.build_reduced_graph_external(module);
         }
@@ -2504,9 +2514,20 @@ pub fn provide(providers: &mut Providers) {
     providers.registered_tools = macros::registered_tools;
 }
 
+/// A wrapper around `&mut Resolver` that may be mutable or immutable, depending on a conditions.
+///
+/// `Cm` stands for "conditionally mutable".
+///
+/// Prefer constructing it through [`Resolver::cm`] to ensure correctness.
+type CmResolver<'r, 'ra, 'tcx> = ref_mut::RefOrMut<'r, Resolver<'ra, 'tcx>>;
+
 mod ref_mut {
+    use std::cell::{BorrowMutError, Cell, Ref, RefCell, RefMut};
+    use std::fmt;
     use std::ops::Deref;
 
+    use crate::Resolver;
+
     /// A wrapper around a mutable reference that conditionally allows mutable access.
     pub(crate) struct RefOrMut<'a, T> {
         p: &'a mut T,
@@ -2555,11 +2576,86 @@ mod ref_mut {
             self.p
         }
     }
-}
 
-/// A wrapper around `&mut Resolver` that may be mutable or immutable, depending on a conditions.
-///
-/// `Cm` stands for "conditionally mutable".
-///
-/// Prefer constructing it through [`Resolver::cm`] to ensure correctness.
-type CmResolver<'r, 'ra, 'tcx> = ref_mut::RefOrMut<'r, Resolver<'ra, 'tcx>>;
+    /// A wrapper around a [`Cell`] that only allows mutation based on a condition in the resolver.
+    #[derive(Default)]
+    pub(crate) struct CmCell<T>(Cell<T>);
+
+    impl<T: Copy + fmt::Debug> fmt::Debug for CmCell<T> {
+        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+            f.debug_tuple("CmCell").field(&self.get()).finish()
+        }
+    }
+
+    impl<T: Copy> Clone for CmCell<T> {
+        #[inline]
+        fn clone(&self) -> CmCell<T> {
+            CmCell::new(self.get())
+        }
+    }
+
+    impl<T: Copy> CmCell<T> {
+        pub(crate) const fn get(&self) -> T {
+            self.0.get()
+        }
+
+        pub(crate) fn update_unchecked(&self, f: impl FnOnce(T) -> T)
+        where
+            T: Copy,
+        {
+            let old = self.get();
+            self.set_unchecked(f(old));
+        }
+    }
+
+    impl<T> CmCell<T> {
+        pub(crate) const fn new(value: T) -> CmCell<T> {
+            CmCell(Cell::new(value))
+        }
+
+        pub(crate) fn set_unchecked(&self, val: T) {
+            self.0.set(val);
+        }
+
+        pub(crate) fn into_inner(self) -> T {
+            self.0.into_inner()
+        }
+    }
+
+    /// A wrapper around a [`RefCell`] that only allows mutable borrows based on a condition in the resolver.
+    #[derive(Default)]
+    pub(crate) struct CmRefCell<T>(RefCell<T>);
+
+    impl<T> CmRefCell<T> {
+        pub(crate) const fn new(value: T) -> CmRefCell<T> {
+            CmRefCell(RefCell::new(value))
+        }
+
+        #[inline]
+        #[track_caller]
+        pub(crate) fn borrow_mut_unchecked(&self) -> RefMut<'_, T> {
+            self.0.borrow_mut()
+        }
+
+        #[inline]
+        #[track_caller]
+        pub(crate) fn borrow_mut<'ra, 'tcx>(&self, r: &Resolver<'ra, 'tcx>) -> RefMut<'_, T> {
+            if r.assert_speculative {
+                panic!("Not allowed to mutably borrow a CmRefCell during speculative resolution");
+            }
+            self.borrow_mut_unchecked()
+        }
+
+        #[inline]
+        #[track_caller]
+        pub(crate) fn try_borrow_mut_unchecked(&self) -> Result<RefMut<'_, T>, BorrowMutError> {
+            self.0.try_borrow_mut()
+        }
+
+        #[inline]
+        #[track_caller]
+        pub(crate) fn borrow(&self) -> Ref<'_, T> {
+            self.0.borrow()
+        }
+    }
+}
diff --git a/compiler/rustc_resolve/src/macros.rs b/compiler/rustc_resolve/src/macros.rs
index d3e98ef839b..c50dfd41b51 100644
--- a/compiler/rustc_resolve/src/macros.rs
+++ b/compiler/rustc_resolve/src/macros.rs
@@ -189,7 +189,7 @@ impl<'ra, 'tcx> ResolverExpand for Resolver<'ra, 'tcx> {
         let output_macro_rules_scope = self.build_reduced_graph(fragment, parent_scope);
         self.output_macro_rules_scopes.insert(expansion, output_macro_rules_scope);
 
-        parent_scope.module.unexpanded_invocations.borrow_mut().remove(&expansion);
+        parent_scope.module.unexpanded_invocations.borrow_mut(self).remove(&expansion);
         if let Some(unexpanded_invocations) =
             self.impl_unexpanded_invocations.get_mut(&self.invocation_parent(expansion))
         {
diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
index ebb6a93b1dd..d1426ff55fb 100644
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@@ -258,6 +258,8 @@ pub enum AutoDiff {
     LooseTypes,
     /// Runs Enzyme's aggressive inlining
     Inline,
+    /// Disable Type Tree
+    NoTT,
 }
 
 /// Settings for `-Z instrument-xray` flag.
@@ -1193,6 +1195,7 @@ pub struct OutputFilenames {
     filestem: String,
     pub single_output_file: Option<OutFileName>,
     temps_directory: Option<PathBuf>,
+    explicit_dwo_out_directory: Option<PathBuf>,
     pub outputs: OutputTypes,
 }
 
@@ -1225,6 +1228,7 @@ impl OutputFilenames {
         out_filestem: String,
         single_output_file: Option<OutFileName>,
         temps_directory: Option<PathBuf>,
+        explicit_dwo_out_directory: Option<PathBuf>,
         extra: String,
         outputs: OutputTypes,
     ) -> Self {
@@ -1232,6 +1236,7 @@ impl OutputFilenames {
             out_directory,
             single_output_file,
             temps_directory,
+            explicit_dwo_out_directory,
             outputs,
             crate_stem: format!("{out_crate_name}{extra}"),
             filestem: format!("{out_filestem}{extra}"),
@@ -1281,7 +1286,14 @@ impl OutputFilenames {
         codegen_unit_name: &str,
         invocation_temp: Option<&str>,
     ) -> PathBuf {
-        self.temp_path_ext_for_cgu(DWARF_OBJECT_EXT, codegen_unit_name, invocation_temp)
+        let p = self.temp_path_ext_for_cgu(DWARF_OBJECT_EXT, codegen_unit_name, invocation_temp);
+        if let Some(dwo_out) = &self.explicit_dwo_out_directory {
+            let mut o = dwo_out.clone();
+            o.push(p.file_name().unwrap());
+            o
+        } else {
+            p
+        }
     }
 
     /// Like `temp_path`, but also supports things where there is no corresponding
diff --git a/compiler/rustc_session/src/config/cfg.rs b/compiler/rustc_session/src/config/cfg.rs
index f3d91ce4a5d..a72f6201dce 100644
--- a/compiler/rustc_session/src/config/cfg.rs
+++ b/compiler/rustc_session/src/config/cfg.rs
@@ -259,11 +259,11 @@ pub(crate) fn default_configuration(sess: &Session) -> Cfg {
     });
     let mut has_atomic = false;
     for (i, align) in [
-        (8, layout.i8_align.abi),
-        (16, layout.i16_align.abi),
-        (32, layout.i32_align.abi),
-        (64, layout.i64_align.abi),
-        (128, layout.i128_align.abi),
+        (8, layout.i8_align),
+        (16, layout.i16_align),
+        (32, layout.i32_align),
+        (64, layout.i64_align),
+        (128, layout.i128_align),
     ] {
         if i >= sess.target.min_atomic_width() && i <= sess.target.max_atomic_width() {
             if !has_atomic {
diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs
index b2cc169f12c..6dd90546de1 100644
--- a/compiler/rustc_session/src/options.rs
+++ b/compiler/rustc_session/src/options.rs
@@ -792,7 +792,7 @@ mod desc {
     pub(crate) const parse_list: &str = "a space-separated list of strings";
     pub(crate) const parse_list_with_polarity: &str =
         "a comma-separated list of strings, with elements beginning with + or -";
-    pub(crate) const parse_autodiff: &str = "a comma separated list of settings: `Enable`, `PrintSteps`, `PrintTA`, `PrintTAFn`, `PrintAA`, `PrintPerf`, `PrintModBefore`, `PrintModAfter`, `PrintModFinal`, `PrintPasses`, `NoPostopt`, `LooseTypes`, `Inline`";
+    pub(crate) const parse_autodiff: &str = "a comma separated list of settings: `Enable`, `PrintSteps`, `PrintTA`, `PrintTAFn`, `PrintAA`, `PrintPerf`, `PrintModBefore`, `PrintModAfter`, `PrintModFinal`, `PrintPasses`, `NoPostopt`, `LooseTypes`, `Inline`, `NoTT`";
     pub(crate) const parse_offload: &str = "a comma separated list of settings: `Enable`";
     pub(crate) const parse_comma_list: &str = "a comma-separated list of strings";
     pub(crate) const parse_opt_comma_list: &str = parse_comma_list;
@@ -1481,6 +1481,7 @@ pub mod parse {
                 "PrintPasses" => AutoDiff::PrintPasses,
                 "LooseTypes" => AutoDiff::LooseTypes,
                 "Inline" => AutoDiff::Inline,
+                "NoTT" => AutoDiff::NoTT,
                 _ => {
                     // FIXME(ZuseZ4): print an error saying which value is not recognized
                     return false;
@@ -2633,6 +2634,8 @@ written to standard error output)"),
                  file which is ignored by the linker
         `single`: sections which do not require relocation are written into object file but ignored
                   by the linker"),
+    split_dwarf_out_dir : Option<PathBuf> = (None, parse_opt_pathbuf, [TRACKED],
+        "location for writing split DWARF objects (`.dwo`) if enabled"),
     split_lto_unit: Option<bool> = (None, parse_opt_bool, [TRACKED],
         "enable LTO unit splitting (default: no)"),
     src_hash_algorithm: Option<SourceFileHashAlgorithm> = (None, parse_src_file_hash, [TRACKED],
diff --git a/compiler/rustc_span/src/analyze_source_file.rs b/compiler/rustc_span/src/analyze_source_file.rs
index c32593a6d95..bb2cda77dff 100644
--- a/compiler/rustc_span/src/analyze_source_file.rs
+++ b/compiler/rustc_span/src/analyze_source_file.rs
@@ -81,8 +81,8 @@ cfg_select! {
                 // use `loadu`, which supports unaligned loading.
                 let chunk = unsafe { _mm_loadu_si128(chunk.as_ptr() as *const __m128i) };
 
-                // For character in the chunk, see if its byte value is < 0, which
-                // indicates that it's part of a UTF-8 char.
+                // For each character in the chunk, see if its byte value is < 0,
+                // which indicates that it's part of a UTF-8 char.
                 let multibyte_test = _mm_cmplt_epi8(chunk, _mm_set1_epi8(0));
                 // Create a bit mask from the comparison results.
                 let multibyte_mask = _mm_movemask_epi8(multibyte_test);
@@ -132,8 +132,111 @@ cfg_select! {
             }
         }
     }
+    target_arch = "loongarch64" => {
+        fn analyze_source_file_dispatch(
+            src: &str,
+            lines: &mut Vec<RelativeBytePos>,
+            multi_byte_chars: &mut Vec<MultiByteChar>,
+        ) {
+            use std::arch::is_loongarch_feature_detected;
+
+            if is_loongarch_feature_detected!("lsx") {
+                unsafe {
+                    analyze_source_file_lsx(src, lines, multi_byte_chars);
+                }
+            } else {
+                analyze_source_file_generic(
+                    src,
+                    src.len(),
+                    RelativeBytePos::from_u32(0),
+                    lines,
+                    multi_byte_chars,
+                );
+            }
+        }
+
+        /// Checks 16 byte chunks of text at a time. If the chunk contains
+        /// something other than printable ASCII characters and newlines, the
+        /// function falls back to the generic implementation. Otherwise it uses
+        /// LSX intrinsics to quickly find all newlines.
+        #[target_feature(enable = "lsx")]
+        unsafe fn analyze_source_file_lsx(
+            src: &str,
+            lines: &mut Vec<RelativeBytePos>,
+            multi_byte_chars: &mut Vec<MultiByteChar>,
+        ) {
+            use std::arch::loongarch64::*;
+
+            const CHUNK_SIZE: usize = 16;
+
+            let (chunks, tail) = src.as_bytes().as_chunks::<CHUNK_SIZE>();
+
+            // This variable keeps track of where we should start decoding a
+            // chunk. If a multi-byte character spans across chunk boundaries,
+            // we need to skip that part in the next chunk because we already
+            // handled it.
+            let mut intra_chunk_offset = 0;
+
+            for (chunk_index, chunk) in chunks.iter().enumerate() {
+                // All LSX memory instructions support unaligned access, so using
+                // vld is fine.
+                let chunk = unsafe { lsx_vld::<0>(chunk.as_ptr() as *const i8) };
+
+                // For each character in the chunk, see if its byte value is < 0,
+                // which indicates that it's part of a UTF-8 char.
+                let multibyte_mask = lsx_vmskltz_b(chunk);
+                // Create a bit mask from the comparison results.
+                let multibyte_mask = lsx_vpickve2gr_w::<0>(multibyte_mask);
+
+                // If the bit mask is all zero, we only have ASCII chars here:
+                if multibyte_mask == 0 {
+                    assert!(intra_chunk_offset == 0);
+
+                    // Check for newlines in the chunk
+                    let newlines_test = lsx_vseqi_b::<{b'\n' as i32}>(chunk);
+                    let newlines_mask = lsx_vmskltz_b(newlines_test);
+                    let mut newlines_mask = lsx_vpickve2gr_w::<0>(newlines_mask);
+
+                    let output_offset = RelativeBytePos::from_usize(chunk_index * CHUNK_SIZE + 1);
+
+                    while newlines_mask != 0 {
+                        let index = newlines_mask.trailing_zeros();
+
+                        lines.push(RelativeBytePos(index) + output_offset);
+
+                        // Clear the bit, so we can find the next one.
+                        newlines_mask &= newlines_mask - 1;
+                    }
+                } else {
+                    // The slow path.
+                    // There are multibyte chars in here, fallback to generic decoding.
+                    let scan_start = chunk_index * CHUNK_SIZE + intra_chunk_offset;
+                    intra_chunk_offset = analyze_source_file_generic(
+                        &src[scan_start..],
+                        CHUNK_SIZE - intra_chunk_offset,
+                        RelativeBytePos::from_usize(scan_start),
+                        lines,
+                        multi_byte_chars,
+                    );
+                }
+            }
+
+            // There might still be a tail left to analyze
+            let tail_start = src.len() - tail.len() + intra_chunk_offset;
+            if tail_start < src.len() {
+                analyze_source_file_generic(
+                    &src[tail_start..],
+                    src.len() - tail_start,
+                    RelativeBytePos::from_usize(tail_start),
+                    lines,
+                    multi_byte_chars,
+                );
+            }
+        }
+    }
     _ => {
-        // The target (or compiler version) does not support SSE2 ...
+        // The target (or compiler version) does not support vector instructions
+        // our specialized implementations need (x86 SSE2, loongarch64 LSX)...
         fn analyze_source_file_dispatch(
             src: &str,
             lines: &mut Vec<RelativeBytePos>,
diff --git a/compiler/rustc_span/src/lib.rs b/compiler/rustc_span/src/lib.rs
index e95b743b1ce..ededbea57e9 100644
--- a/compiler/rustc_span/src/lib.rs
+++ b/compiler/rustc_span/src/lib.rs
@@ -17,7 +17,7 @@
 
 // tidy-alphabetical-start
 #![allow(internal_features)]
-#![cfg_attr(bootstrap, feature(round_char_boundary))]
+#![cfg_attr(target_arch = "loongarch64", feature(stdarch_loongarch))]
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![doc(rust_logo)]
 #![feature(array_windows)]
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index faf32523baa..b34a64108e3 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -545,6 +545,7 @@ symbols! {
         attributes,
         audit_that,
         augmented_assignments,
+        auto_cfg,
         auto_traits,
         autodiff,
         autodiff_forward,
@@ -628,7 +629,6 @@ symbols! {
         cfg_emscripten_wasm_eh,
         cfg_eval,
         cfg_fmt_debug,
-        cfg_hide,
         cfg_overflow_checks,
         cfg_panic,
         cfg_relocation_model,
@@ -679,6 +679,7 @@ symbols! {
         cmpxchg16b_target_feature,
         cmse_nonsecure_entry,
         coerce_pointee_validated,
+        coerce_shared,
         coerce_unsized,
         cold,
         cold_path,
@@ -939,6 +940,7 @@ symbols! {
         ermsb_target_feature,
         exact_div,
         except,
+        exception_handling: "exception-handling",
         exchange_malloc,
         exclusive_range_pattern,
         exhaustive_integer_patterns,
@@ -1149,6 +1151,7 @@ symbols! {
         hashset_iter_ty,
         hexagon_target_feature,
         hidden,
+        hide,
         hint,
         homogeneous_aggregate,
         host,
@@ -1987,6 +1990,7 @@ symbols! {
         shl_assign,
         shorter_tail_lifetimes,
         should_panic,
+        show,
         shr,
         shr_assign,
         sig_dfl,
diff --git a/compiler/rustc_target/src/callconv/arm.rs b/compiler/rustc_target/src/callconv/arm.rs
index 70830fa07b6..abc9a404e2e 100644
--- a/compiler/rustc_target/src/callconv/arm.rs
+++ b/compiler/rustc_target/src/callconv/arm.rs
@@ -77,7 +77,7 @@ where
         }
     }
 
-    let align = arg.layout.align.abi.bytes();
+    let align = arg.layout.align.bytes();
     let total = arg.layout.size;
     arg.cast_to(Uniform::consecutive(if align <= 4 { Reg::i32() } else { Reg::i64() }, total));
 }
diff --git a/compiler/rustc_target/src/callconv/loongarch.rs b/compiler/rustc_target/src/callconv/loongarch.rs
index 9213d73e24e..bc3c9601fa3 100644
--- a/compiler/rustc_target/src/callconv/loongarch.rs
+++ b/compiler/rustc_target/src/callconv/loongarch.rs
@@ -322,7 +322,7 @@ fn classify_arg<'a, Ty, C>(
     }
 
     let total = arg.layout.size;
-    let align = arg.layout.align.abi.bits();
+    let align = arg.layout.align.bits();
 
     // "Scalars wider than 2✕XLEN are passed by reference and are replaced in
     // the argument list with the address."
diff --git a/compiler/rustc_target/src/callconv/mips.rs b/compiler/rustc_target/src/callconv/mips.rs
index 48a01da865b..8ffd7bd1778 100644
--- a/compiler/rustc_target/src/callconv/mips.rs
+++ b/compiler/rustc_target/src/callconv/mips.rs
@@ -24,7 +24,7 @@ where
     }
     let dl = cx.data_layout();
     let size = arg.layout.size;
-    let align = arg.layout.align.max(dl.i32_align).min(dl.i64_align).abi;
+    let align = arg.layout.align.abi.max(dl.i32_align).min(dl.i64_align);
 
     if arg.layout.is_aggregate() {
         let pad_i32 = !offset.is_aligned(align);
diff --git a/compiler/rustc_target/src/callconv/mips64.rs b/compiler/rustc_target/src/callconv/mips64.rs
index 0209838bec1..8386a15933c 100644
--- a/compiler/rustc_target/src/callconv/mips64.rs
+++ b/compiler/rustc_target/src/callconv/mips64.rs
@@ -110,9 +110,9 @@ where
                 // We only care about aligned doubles
                 if let BackendRepr::Scalar(scalar) = field.backend_repr {
                     if scalar.primitive() == Primitive::Float(Float::F64) {
-                        if offset.is_aligned(dl.f64_align.abi) {
+                        if offset.is_aligned(dl.f64_align) {
                             // Insert enough integers to cover [last_offset, offset)
-                            assert!(last_offset.is_aligned(dl.f64_align.abi));
+                            assert!(last_offset.is_aligned(dl.f64_align));
                             for _ in 0..((offset - last_offset).bits() / 64)
                                 .min((prefix.len() - prefix_index) as u64)
                             {
diff --git a/compiler/rustc_target/src/callconv/mod.rs b/compiler/rustc_target/src/callconv/mod.rs
index 7a7c63c475b..c59af581a1f 100644
--- a/compiler/rustc_target/src/callconv/mod.rs
+++ b/compiler/rustc_target/src/callconv/mod.rs
@@ -332,7 +332,7 @@ impl CastTarget {
         self.prefix
             .iter()
             .filter_map(|x| x.map(|reg| reg.align(cx)))
-            .fold(cx.data_layout().aggregate_align.abi.max(self.rest.align(cx)), |acc, align| {
+            .fold(cx.data_layout().aggregate_align.max(self.rest.align(cx)), |acc, align| {
                 acc.max(align)
             })
     }
diff --git a/compiler/rustc_target/src/callconv/nvptx64.rs b/compiler/rustc_target/src/callconv/nvptx64.rs
index 44977de7fcb..dc32dd87a7e 100644
--- a/compiler/rustc_target/src/callconv/nvptx64.rs
+++ b/compiler/rustc_target/src/callconv/nvptx64.rs
@@ -21,7 +21,7 @@ fn classify_arg<Ty>(arg: &mut ArgAbi<'_, Ty>) {
 
 /// the pass mode used for aggregates in arg and ret position
 fn classify_aggregate<Ty>(arg: &mut ArgAbi<'_, Ty>) {
-    let align_bytes = arg.layout.align.abi.bytes();
+    let align_bytes = arg.layout.align.bytes();
     let size = arg.layout.size;
 
     let reg = match align_bytes {
@@ -60,7 +60,7 @@ where
     //     "`extern \"ptx-kernel\"` doesn't allow passing types other than primitives and structs"
     // );
 
-    let align_bytes = arg.layout.align.abi.bytes();
+    let align_bytes = arg.layout.align.bytes();
 
     let unit = match align_bytes {
         1 => Reg::i8(),
diff --git a/compiler/rustc_target/src/callconv/powerpc64.rs b/compiler/rustc_target/src/callconv/powerpc64.rs
index 89ec85e4b66..be1d13816ef 100644
--- a/compiler/rustc_target/src/callconv/powerpc64.rs
+++ b/compiler/rustc_target/src/callconv/powerpc64.rs
@@ -89,7 +89,7 @@ where
         // Aggregates larger than i64 should be padded at the tail to fill out a whole number
         // of i64s or i128s, depending on the aggregate alignment. Always use an array for
         // this, even if there is only a single element.
-        let reg = if arg.layout.align.abi.bytes() > 8 { Reg::i128() } else { Reg::i64() };
+        let reg = if arg.layout.align.bytes() > 8 { Reg::i128() } else { Reg::i64() };
         arg.cast_to(Uniform::consecutive(
             reg,
             size.align_to(Align::from_bytes(reg.size.bytes()).unwrap()),
diff --git a/compiler/rustc_target/src/callconv/riscv.rs b/compiler/rustc_target/src/callconv/riscv.rs
index 161e2c1645f..16de3fe070d 100644
--- a/compiler/rustc_target/src/callconv/riscv.rs
+++ b/compiler/rustc_target/src/callconv/riscv.rs
@@ -328,7 +328,7 @@ fn classify_arg<'a, Ty, C>(
     }
 
     let total = arg.layout.size;
-    let align = arg.layout.align.abi.bits();
+    let align = arg.layout.align.bits();
 
     // "Scalars wider than 2✕XLEN are passed by reference and are replaced in
     // the argument list with the address."
diff --git a/compiler/rustc_target/src/callconv/sparc.rs b/compiler/rustc_target/src/callconv/sparc.rs
index 48a01da865b..8ffd7bd1778 100644
--- a/compiler/rustc_target/src/callconv/sparc.rs
+++ b/compiler/rustc_target/src/callconv/sparc.rs
@@ -24,7 +24,7 @@ where
     }
     let dl = cx.data_layout();
     let size = arg.layout.size;
-    let align = arg.layout.align.max(dl.i32_align).min(dl.i64_align).abi;
+    let align = arg.layout.align.abi.max(dl.i32_align).min(dl.i64_align);
 
     if arg.layout.is_aggregate() {
         let pad_i32 = !offset.is_aligned(align);
diff --git a/compiler/rustc_target/src/callconv/sparc64.rs b/compiler/rustc_target/src/callconv/sparc64.rs
index ecc9067ced3..62c8ed1dc21 100644
--- a/compiler/rustc_target/src/callconv/sparc64.rs
+++ b/compiler/rustc_target/src/callconv/sparc64.rs
@@ -29,7 +29,7 @@ where
 
     data.has_float = true;
 
-    if !data.last_offset.is_aligned(dl.f64_align.abi) && data.last_offset < offset {
+    if !data.last_offset.is_aligned(dl.f64_align) && data.last_offset < offset {
         if data.prefix_index == data.prefix.len() {
             return data;
         }
diff --git a/compiler/rustc_target/src/callconv/xtensa.rs b/compiler/rustc_target/src/callconv/xtensa.rs
index a73a70a1a0c..561ee98787d 100644
--- a/compiler/rustc_target/src/callconv/xtensa.rs
+++ b/compiler/rustc_target/src/callconv/xtensa.rs
@@ -48,7 +48,7 @@ where
     }
 
     let size = arg.layout.size.bits();
-    let needed_align = arg.layout.align.abi.bits();
+    let needed_align = arg.layout.align.bits();
     let mut must_use_stack = false;
 
     // Determine the number of GPRs needed to pass the current argument
diff --git a/compiler/rustc_target/src/spec/base/apple/mod.rs b/compiler/rustc_target/src/spec/base/apple/mod.rs
index ecc74264160..39e604bcce7 100644
--- a/compiler/rustc_target/src/spec/base/apple/mod.rs
+++ b/compiler/rustc_target/src/spec/base/apple/mod.rs
@@ -158,12 +158,22 @@ pub(crate) fn base(
             SplitDebuginfo::Off,
         ]),
 
+        // Tell the linker that we would like it to avoid irreproducible binaries.
+        //
         // This environment variable is pretty magical but is intended for
         // producing deterministic builds. This was first discovered to be used
         // by the `ar` tool as a way to control whether or not mtime entries in
-        // the archive headers were set to zero or not. It appears that
-        // eventually the linker got updated to do the same thing and now reads
-        // this environment variable too in recent versions.
+        // the archive headers were set to zero or not.
+        //
+        // In `ld64-351.8`, shipped with Xcode 9.3, the linker was updated to
+        // read this flag too. Linker versions that don't support this flag
+        // may embed modification timestamps in binaries (especially in debug
+        // information).
+        //
+        // A cleaner alternative would be to pass the `-reproducible` flag,
+        // though that is only supported since `ld64-819.6` shipped with Xcode
+        // 14, which is too new for our minimum supported version:
+        // https://doc.rust-lang.org/rustc/platform-support/apple-darwin.html#host-tooling
         //
         // For some more info see the commentary on #47086
         link_env: Cow::Borrowed(&[(Cow::Borrowed("ZERO_AR_DATE"), Cow::Borrowed("1"))]),
diff --git a/compiler/rustc_target/src/spec/base/windows_gnu.rs b/compiler/rustc_target/src/spec/base/windows_gnu.rs
index 4ba11021988..2867428e42f 100644
--- a/compiler/rustc_target/src/spec/base/windows_gnu.rs
+++ b/compiler/rustc_target/src/spec/base/windows_gnu.rs
@@ -93,10 +93,7 @@ pub(crate) fn opts() -> TargetOptions {
         binary_format: BinaryFormat::Coff,
         allows_weak_linkage: false,
         pre_link_args,
-        pre_link_objects: crt_objects::pre_mingw(),
-        post_link_objects: crt_objects::post_mingw(),
         pre_link_objects_self_contained: crt_objects::pre_mingw_self_contained(),
-        post_link_objects_self_contained: crt_objects::post_mingw_self_contained(),
         link_self_contained: LinkSelfContainedDefault::InferredForMingw,
         late_link_args,
         late_link_args_dynamic,
diff --git a/compiler/rustc_target/src/spec/crt_objects.rs b/compiler/rustc_target/src/spec/crt_objects.rs
index e3b6430a463..2d84e78f255 100644
--- a/compiler/rustc_target/src/spec/crt_objects.rs
+++ b/compiler/rustc_target/src/spec/crt_objects.rs
@@ -86,6 +86,17 @@ pub(super) fn post_musl_self_contained() -> CrtObjects {
 
 pub(super) fn pre_mingw_self_contained() -> CrtObjects {
     new(&[
+        (LinkOutputKind::DynamicNoPicExe, &["crt2.o"]),
+        (LinkOutputKind::DynamicPicExe, &["crt2.o"]),
+        (LinkOutputKind::StaticNoPicExe, &["crt2.o"]),
+        (LinkOutputKind::StaticPicExe, &["crt2.o"]),
+        (LinkOutputKind::DynamicDylib, &["dllcrt2.o"]),
+        (LinkOutputKind::StaticDylib, &["dllcrt2.o"]),
+    ])
+}
+
+pub(super) fn pre_i686_mingw_self_contained() -> CrtObjects {
+    new(&[
         (LinkOutputKind::DynamicNoPicExe, &["crt2.o", "rsbegin.o"]),
         (LinkOutputKind::DynamicPicExe, &["crt2.o", "rsbegin.o"]),
         (LinkOutputKind::StaticNoPicExe, &["crt2.o", "rsbegin.o"]),
@@ -95,15 +106,15 @@ pub(super) fn pre_mingw_self_contained() -> CrtObjects {
     ])
 }
 
-pub(super) fn post_mingw_self_contained() -> CrtObjects {
+pub(super) fn post_i686_mingw_self_contained() -> CrtObjects {
     all("rsend.o")
 }
 
-pub(super) fn pre_mingw() -> CrtObjects {
+pub(super) fn pre_i686_mingw() -> CrtObjects {
     all("rsbegin.o")
 }
 
-pub(super) fn post_mingw() -> CrtObjects {
+pub(super) fn post_i686_mingw() -> CrtObjects {
     all("rsend.o")
 }
 
diff --git a/compiler/rustc_target/src/spec/targets/armebv7r_none_eabi.rs b/compiler/rustc_target/src/spec/targets/armebv7r_none_eabi.rs
index d227d63c4a3..0ae7cd7a377 100644
--- a/compiler/rustc_target/src/spec/targets/armebv7r_none_eabi.rs
+++ b/compiler/rustc_target/src/spec/targets/armebv7r_none_eabi.rs
@@ -12,7 +12,7 @@ pub(crate) fn target() -> Target {
         llvm_target: "armebv7r-none-eabi".into(),
         metadata: TargetMetadata {
             description: Some("Bare Armv7-R, Big Endian".into()),
-            tier: Some(2),
+            tier: Some(3),
             host_tools: Some(false),
             std: Some(false),
         },
diff --git a/compiler/rustc_target/src/spec/targets/armebv7r_none_eabihf.rs b/compiler/rustc_target/src/spec/targets/armebv7r_none_eabihf.rs
index c373afb914e..71ffd8baed5 100644
--- a/compiler/rustc_target/src/spec/targets/armebv7r_none_eabihf.rs
+++ b/compiler/rustc_target/src/spec/targets/armebv7r_none_eabihf.rs
@@ -12,7 +12,7 @@ pub(crate) fn target() -> Target {
         llvm_target: "armebv7r-none-eabihf".into(),
         metadata: TargetMetadata {
             description: Some("Bare Armv7-R, Big Endian, hardfloat".into()),
-            tier: Some(2),
+            tier: Some(3),
             host_tools: Some(false),
             std: Some(false),
         },
diff --git a/compiler/rustc_target/src/spec/targets/i686_pc_windows_gnu.rs b/compiler/rustc_target/src/spec/targets/i686_pc_windows_gnu.rs
index e775c8fc524..a0d403bd05e 100644
--- a/compiler/rustc_target/src/spec/targets/i686_pc_windows_gnu.rs
+++ b/compiler/rustc_target/src/spec/targets/i686_pc_windows_gnu.rs
@@ -1,4 +1,6 @@
-use crate::spec::{Cc, FramePointer, LinkerFlavor, Lld, RustcAbi, Target, TargetMetadata, base};
+use crate::spec::{
+    Cc, FramePointer, LinkerFlavor, Lld, RustcAbi, Target, TargetMetadata, base, crt_objects,
+};
 
 pub(crate) fn target() -> Target {
     let mut base = base::windows_gnu::opts();
@@ -15,6 +17,10 @@ pub(crate) fn target() -> Target {
         &["-m", "i386pe", "--large-address-aware"],
     );
     base.add_pre_link_args(LinkerFlavor::Gnu(Cc::Yes, Lld::No), &["-Wl,--large-address-aware"]);
+    base.pre_link_objects = crt_objects::pre_i686_mingw();
+    base.post_link_objects = crt_objects::post_i686_mingw();
+    base.pre_link_objects_self_contained = crt_objects::pre_i686_mingw_self_contained();
+    base.post_link_objects_self_contained = crt_objects::post_i686_mingw_self_contained();
 
     Target {
         llvm_target: "i686-pc-windows-gnu".into(),
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs
index d485eb7266b..bec12750728 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs
@@ -1897,6 +1897,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         other: bool,
         param_env: ty::ParamEnv<'tcx>,
     ) -> bool {
+        let parent_map = self.tcx.visible_parent_map(());
         let alternative_candidates = |def_id: DefId| {
             let mut impl_candidates: Vec<_> = self
                 .tcx
@@ -1921,7 +1922,21 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                         // FIXME(compiler-errors): This could be generalized, both to
                         // be more granular, and probably look past other `#[fundamental]`
                         // types, too.
-                        self.tcx.visibility(def.did()).is_accessible_from(body_def_id, self.tcx)
+                        let mut did = def.did();
+                        if self.tcx.visibility(did).is_accessible_from(body_def_id, self.tcx) {
+                            // don't suggest foreign `#[doc(hidden)]` types
+                            if !did.is_local() {
+                                while let Some(parent) = parent_map.get(&did) {
+                                    if self.tcx.is_doc_hidden(did) {
+                                        return false;
+                                    }
+                                    did = *parent;
+                                }
+                            }
+                            true
+                        } else {
+                            false
+                        }
                     } else {
                         true
                     }
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/mod.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/mod.rs
index b3d1b8e3888..9052031ce4f 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/mod.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/mod.rs
@@ -21,7 +21,7 @@ use rustc_infer::traits::{
 };
 use rustc_middle::ty::print::{PrintTraitRefExt as _, with_no_trimmed_paths};
 use rustc_middle::ty::{self, Ty, TyCtxt};
-use rustc_span::{ErrorGuaranteed, ExpnKind, Span};
+use rustc_span::{DesugaringKind, ErrorGuaranteed, ExpnKind, Span};
 use tracing::{info, instrument};
 
 pub use self::overflow::*;
@@ -154,9 +154,20 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             })
             .collect();
 
-        // Ensure `T: Sized`, `T: MetaSized`, `T: PointeeSized` and `T: WF` obligations come last.
+        // Ensure `T: Sized`, `T: MetaSized`, `T: PointeeSized` and `T: WF` obligations come last,
+        // and `Subtype` obligations from `FormatLiteral` desugarings come first.
         // This lets us display diagnostics with more relevant type information and hide redundant
         // E0282 errors.
+        #[derive(Debug, PartialEq, Eq, PartialOrd, Ord)]
+        enum ErrorSortKey {
+            SubtypeFormat(usize, usize),
+            OtherKind,
+            SizedTrait,
+            MetaSizedTrait,
+            PointeeSizedTrait,
+            Coerce,
+            WellFormed,
+        }
         errors.sort_by_key(|e| {
             let maybe_sizedness_did = match e.obligation.predicate.kind().skip_binder() {
                 ty::PredicateKind::Clause(ty::ClauseKind::Trait(pred)) => Some(pred.def_id()),
@@ -165,12 +176,30 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             };
 
             match e.obligation.predicate.kind().skip_binder() {
-                _ if maybe_sizedness_did == self.tcx.lang_items().sized_trait() => 1,
-                _ if maybe_sizedness_did == self.tcx.lang_items().meta_sized_trait() => 2,
-                _ if maybe_sizedness_did == self.tcx.lang_items().pointee_sized_trait() => 3,
-                ty::PredicateKind::Coerce(_) => 4,
-                ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(_)) => 5,
-                _ => 0,
+                ty::PredicateKind::Subtype(_)
+                    if matches!(
+                        e.obligation.cause.span.desugaring_kind(),
+                        Some(DesugaringKind::FormatLiteral { .. })
+                    ) =>
+                {
+                    let (_, row, col, ..) =
+                        self.tcx.sess.source_map().span_to_location_info(e.obligation.cause.span);
+                    ErrorSortKey::SubtypeFormat(row, col)
+                }
+                _ if maybe_sizedness_did == self.tcx.lang_items().sized_trait() => {
+                    ErrorSortKey::SizedTrait
+                }
+                _ if maybe_sizedness_did == self.tcx.lang_items().meta_sized_trait() => {
+                    ErrorSortKey::MetaSizedTrait
+                }
+                _ if maybe_sizedness_did == self.tcx.lang_items().pointee_sized_trait() => {
+                    ErrorSortKey::PointeeSizedTrait
+                }
+                ty::PredicateKind::Coerce(_) => ErrorSortKey::Coerce,
+                ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(_)) => {
+                    ErrorSortKey::WellFormed
+                }
+                _ => ErrorSortKey::OtherKind,
             }
         });
 
diff --git a/compiler/rustc_trait_selection/src/infer.rs b/compiler/rustc_trait_selection/src/infer.rs
index 4c50c44b841..cd076d1cb69 100644
--- a/compiler/rustc_trait_selection/src/infer.rs
+++ b/compiler/rustc_trait_selection/src/infer.rs
@@ -9,7 +9,7 @@ use rustc_middle::infer::canonical::{
     Canonical, CanonicalQueryInput, CanonicalQueryResponse, QueryResponse,
 };
 use rustc_middle::traits::query::NoSolution;
-use rustc_middle::ty::{self, GenericArg, Ty, TyCtxt, TypeFoldable, TypeVisitableExt, Upcast};
+use rustc_middle::ty::{self, GenericArg, Ty, TyCtxt, TypeFoldable, Upcast};
 use rustc_span::DUMMY_SP;
 use tracing::instrument;
 
@@ -31,19 +31,7 @@ impl<'tcx> InferCtxt<'tcx> {
 
     fn type_is_copy_modulo_regions(&self, param_env: ty::ParamEnv<'tcx>, ty: Ty<'tcx>) -> bool {
         let ty = self.resolve_vars_if_possible(ty);
-
-        // FIXME(#132279): This should be removed as it causes us to incorrectly
-        // handle opaques in their defining scope, and stalled coroutines.
-        if !self.next_trait_solver() && !(param_env, ty).has_infer() && !ty.has_coroutines() {
-            return self.tcx.type_is_copy_modulo_regions(self.typing_env(param_env), ty);
-        }
-
         let copy_def_id = self.tcx.require_lang_item(LangItem::Copy, DUMMY_SP);
-
-        // This can get called from typeck (by euv), and `moves_by_default`
-        // rightly refuses to work with inference variables, but
-        // moves_by_default has a cache, which we want to use in other
-        // cases.
         traits::type_known_to_meet_bound_modulo_regions(self, param_env, ty, copy_def_id)
     }
 
diff --git a/compiler/rustc_trait_selection/src/regions.rs b/compiler/rustc_trait_selection/src/regions.rs
index 2b33b8ac9f8..debc4fda15a 100644
--- a/compiler/rustc_trait_selection/src/regions.rs
+++ b/compiler/rustc_trait_selection/src/regions.rs
@@ -77,6 +77,8 @@ impl<'tcx> InferCtxt<'tcx> {
     ///
     /// Prefer this method over `resolve_regions_with_normalize`, unless you are
     /// doing something specific for normalization.
+    ///
+    /// This function assumes that all infer variables are already constrained.
     fn resolve_regions(
         &self,
         body_id: LocalDefId,
diff --git a/compiler/rustc_trait_selection/src/traits/query/evaluate_obligation.rs b/compiler/rustc_trait_selection/src/traits/query/evaluate_obligation.rs
index ae731505abf..34e0176d213 100644
--- a/compiler/rustc_trait_selection/src/traits/query/evaluate_obligation.rs
+++ b/compiler/rustc_trait_selection/src/traits/query/evaluate_obligation.rs
@@ -1,6 +1,6 @@
 use rustc_infer::traits::solve::Goal;
 use rustc_macros::extension;
-use rustc_middle::span_bug;
+use rustc_middle::{span_bug, ty};
 use rustc_next_trait_solver::solve::SolverDelegateEvalExt;
 
 use crate::infer::InferCtxt;
@@ -22,7 +22,7 @@ impl<'tcx> InferCtxt<'tcx> {
     /// for more details.
     fn predicate_may_hold_opaque_types_jank(&self, obligation: &PredicateObligation<'tcx>) -> bool {
         if self.next_trait_solver() {
-            <&SolverDelegate<'tcx>>::from(self).root_goal_may_hold_opaque_types_jank(Goal::new(
+            self.goal_may_hold_opaque_types_jank(Goal::new(
                 self.tcx,
                 obligation.param_env,
                 obligation.predicate,
@@ -32,6 +32,13 @@ impl<'tcx> InferCtxt<'tcx> {
         }
     }
 
+    /// See the comment on [OpaqueTypesJank](crate::solve::OpaqueTypesJank)
+    /// for more details.
+    fn goal_may_hold_opaque_types_jank(&self, goal: Goal<'tcx, ty::Predicate<'tcx>>) -> bool {
+        assert!(self.next_trait_solver());
+        <&SolverDelegate<'tcx>>::from(self).root_goal_may_hold_opaque_types_jank(goal)
+    }
+
     /// Evaluates whether the predicate can be satisfied in the given
     /// `ParamEnv`, and returns `false` if not certain. However, this is
     /// not entirely accurate if inference variables are involved.
diff --git a/compiler/rustc_trait_selection/src/traits/query/type_op/implied_outlives_bounds.rs b/compiler/rustc_trait_selection/src/traits/query/type_op/implied_outlives_bounds.rs
index 7540cbe3fd1..e55ffb4d5fd 100644
--- a/compiler/rustc_trait_selection/src/traits/query/type_op/implied_outlives_bounds.rs
+++ b/compiler/rustc_trait_selection/src/traits/query/type_op/implied_outlives_bounds.rs
@@ -55,6 +55,12 @@ pub fn compute_implied_outlives_bounds_inner<'tcx>(
     span: Span,
     disable_implied_bounds_hack: bool,
 ) -> Result<Vec<OutlivesBound<'tcx>>, NoSolution> {
+    // Inside mir borrowck, each computation starts with an empty list.
+    assert!(
+        ocx.infcx.inner.borrow().region_obligations().is_empty(),
+        "compute_implied_outlives_bounds assumes region obligations are empty before starting"
+    );
+
     let normalize_ty = |ty| -> Result<_, NoSolution> {
         // We must normalize the type so we can compute the right outlives components.
         // for example, if we have some constrained param type like `T: Trait<Out = U>`,
@@ -143,7 +149,7 @@ pub fn compute_implied_outlives_bounds_inner<'tcx>(
         && ty.visit_with(&mut ContainsBevyParamSet { tcx: ocx.infcx.tcx }).is_break()
     {
         for TypeOutlivesConstraint { sup_type, sub_region, .. } in
-            ocx.infcx.take_registered_region_obligations()
+            ocx.infcx.clone_registered_region_obligations()
         {
             let mut components = smallvec![];
             push_outlives_components(ocx.infcx.tcx, sup_type, &mut components);
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index 1dd31990ab7..fb4f28412d4 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -2359,7 +2359,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                 if self.infcx.can_define_opaque_ty(def_id) {
                     unreachable!()
                 } else {
-                    // We can resolve the `impl Trait` to its concrete type,
+                    // We can resolve the opaque type to its hidden type,
                     // which enforces a DAG between the functions requiring
                     // the auto trait bounds in question.
                     match self.tcx().type_of_opaque(def_id) {
diff --git a/compiler/rustc_transmute/src/layout/tree.rs b/compiler/rustc_transmute/src/layout/tree.rs
index a02e8ecf613..7f626e8c4e8 100644
--- a/compiler/rustc_transmute/src/layout/tree.rs
+++ b/compiler/rustc_transmute/src/layout/tree.rs
@@ -361,7 +361,7 @@ pub(crate) mod rustc {
 
                 ty::Ref(region, ty, mutability) => {
                     let layout = layout_of(cx, *ty)?;
-                    let referent_align = layout.align.abi.bytes_usize();
+                    let referent_align = layout.align.bytes_usize();
                     let referent_size = layout.size.bytes_usize();
 
                     Ok(Tree::Ref(Reference {
diff --git a/compiler/rustc_ty_utils/src/layout.rs b/compiler/rustc_ty_utils/src/layout.rs
index f59bc2117d5..317d101dafe 100644
--- a/compiler/rustc_ty_utils/src/layout.rs
+++ b/compiler/rustc_ty_utils/src/layout.rs
@@ -795,7 +795,7 @@ fn variant_info_for_adt<'tcx>(
                     name,
                     offset: offset.bytes(),
                     size: field_layout.size.bytes(),
-                    align: field_layout.align.abi.bytes(),
+                    align: field_layout.align.bytes(),
                     type_name: None,
                 }
             })
@@ -804,7 +804,7 @@ fn variant_info_for_adt<'tcx>(
         VariantInfo {
             name: n,
             kind: if layout.is_unsized() { SizeKind::Min } else { SizeKind::Exact },
-            align: layout.align.abi.bytes(),
+            align: layout.align.bytes(),
             size: if min_size.bytes() == 0 { layout.size.bytes() } else { min_size.bytes() },
             fields: field_info,
         }
@@ -877,7 +877,7 @@ fn variant_info_for_coroutine<'tcx>(
                 name: *name,
                 offset: offset.bytes(),
                 size: field_layout.size.bytes(),
-                align: field_layout.align.abi.bytes(),
+                align: field_layout.align.bytes(),
                 type_name: None,
             }
         })
@@ -905,7 +905,7 @@ fn variant_info_for_coroutine<'tcx>(
                         }),
                         offset: offset.bytes(),
                         size: field_layout.size.bytes(),
-                        align: field_layout.align.abi.bytes(),
+                        align: field_layout.align.bytes(),
                         // Include the type name if there is no field name, or if the name is the
                         // __awaitee placeholder symbol which means a child future being `.await`ed.
                         type_name: (field_name.is_none() || field_name == Some(sym::__awaitee))
@@ -946,7 +946,7 @@ fn variant_info_for_coroutine<'tcx>(
                 name: Some(Symbol::intern(&ty::CoroutineArgs::variant_name(variant_idx))),
                 kind: SizeKind::Exact,
                 size: variant_size.bytes(),
-                align: variant_layout.align.abi.bytes(),
+                align: variant_layout.align.bytes(),
                 fields,
             }
         })
diff --git a/compiler/rustc_ty_utils/src/layout/invariant.rs b/compiler/rustc_ty_utils/src/layout/invariant.rs
index 1311ee31182..b768269215f 100644
--- a/compiler/rustc_ty_utils/src/layout/invariant.rs
+++ b/compiler/rustc_ty_utils/src/layout/invariant.rs
@@ -8,7 +8,7 @@ use rustc_middle::ty::layout::{HasTyCtxt, LayoutCx, TyAndLayout};
 pub(super) fn layout_sanity_check<'tcx>(cx: &LayoutCx<'tcx>, layout: &TyAndLayout<'tcx>) {
     let tcx = cx.tcx();
 
-    if !layout.size.bytes().is_multiple_of(layout.align.abi.bytes()) {
+    if !layout.size.bytes().is_multiple_of(layout.align.bytes()) {
         bug!("size is not a multiple of align, in the following layout:\n{layout:#?}");
     }
     if layout.size.bytes() >= tcx.data_layout.obj_size_bound() {
@@ -300,8 +300,8 @@ pub(super) fn layout_sanity_check<'tcx>(cx: &LayoutCx<'tcx>, layout: &TyAndLayou
                 if variant.align.abi > layout.align.abi {
                     bug!(
                         "Type with alignment {} bytes has variant with alignment {} bytes: {layout:#?}",
-                        layout.align.abi.bytes(),
-                        variant.align.abi.bytes(),
+                        layout.align.bytes(),
+                        variant.align.bytes(),
                     )
                 }
                 // Skip empty variants.
diff --git a/compiler/rustc_type_ir/src/flags.rs b/compiler/rustc_type_ir/src/flags.rs
index 24704c5bb53..ea3903d401e 100644
--- a/compiler/rustc_type_ir/src/flags.rs
+++ b/compiler/rustc_type_ir/src/flags.rs
@@ -347,6 +347,7 @@ impl<I: Interner> FlagComputation<I> {
 
     fn add_ty_pat(&mut self, pat: <I as Interner>::Pat) {
         self.add_flags(pat.flags());
+        self.add_exclusive_binder(pat.outer_exclusive_binder());
     }
 
     fn add_predicate(&mut self, binder: ty::Binder<I, ty::PredicateKind<I>>) {
diff --git a/compiler/rustc_type_ir/src/infer_ctxt.rs b/compiler/rustc_type_ir/src/infer_ctxt.rs
index f743b84bce6..feafcee7bad 100644
--- a/compiler/rustc_type_ir/src/infer_ctxt.rs
+++ b/compiler/rustc_type_ir/src/infer_ctxt.rs
@@ -80,7 +80,7 @@ pub enum TypingMode<I: Interner> {
     /// the old solver as well.
     PostBorrowckAnalysis { defined_opaque_types: I::LocalDefIds },
     /// After analysis, mostly during codegen and MIR optimizations, we're able to
-    /// reveal all opaque types. As the concrete type should *never* be observable
+    /// reveal all opaque types. As the hidden type should *never* be observable
     /// directly by the user, this should not be used by checks which may expose
     /// such details to the user.
     ///
diff --git a/compiler/rustc_type_ir/src/interner.rs b/compiler/rustc_type_ir/src/interner.rs
index cf58aec14a6..886d1a78bcb 100644
--- a/compiler/rustc_type_ir/src/interner.rs
+++ b/compiler/rustc_type_ir/src/interner.rs
@@ -11,9 +11,7 @@ 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, inspect,
-};
+use crate::solve::{CanonicalInput, ExternalConstraintsData, QueryResult, inspect};
 use crate::visit::{Flags, TypeVisitable};
 use crate::{self as ty, CanonicalParamEnvCacheEntry, search_graph};
 
@@ -70,10 +68,10 @@ pub trait Interner:
         + Hash
         + Eq
         + TypeFoldable<Self>
-        + Deref<Target = PredefinedOpaquesData<Self>>;
+        + SliceLike<Item = (ty::OpaqueTypeKey<Self>, Self::Ty)>;
     fn mk_predefined_opaques_in_body(
         self,
-        data: PredefinedOpaquesData<Self>,
+        data: &[(ty::OpaqueTypeKey<Self>, Self::Ty)],
     ) -> Self::PredefinedOpaques;
 
     type LocalDefIds: Copy
diff --git a/compiler/rustc_type_ir/src/search_graph/mod.rs b/compiler/rustc_type_ir/src/search_graph/mod.rs
index 8f8f019510f..7aa58d096d5 100644
--- a/compiler/rustc_type_ir/src/search_graph/mod.rs
+++ b/compiler/rustc_type_ir/src/search_graph/mod.rs
@@ -86,14 +86,12 @@ pub trait Delegate: Sized {
         kind: PathKind,
         input: <Self::Cx as Cx>::Input,
     ) -> <Self::Cx as Cx>::Result;
-    fn is_initial_provisional_result(
+    fn is_initial_provisional_result(result: <Self::Cx as Cx>::Result) -> Option<PathKind>;
+    fn stack_overflow_result(
         cx: Self::Cx,
-        kind: PathKind,
         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) -> <Self::Cx as Cx>::Result;
-    fn on_fixpoint_overflow(
+    ) -> <Self::Cx as Cx>::Result;
+    fn fixpoint_overflow_result(
         cx: Self::Cx,
         input: <Self::Cx as Cx>::Input,
     ) -> <Self::Cx as Cx>::Result;
@@ -215,6 +213,27 @@ impl HeadUsages {
         let HeadUsages { inductive, unknown, coinductive, forced_ambiguity } = self;
         inductive == 0 && unknown == 0 && coinductive == 0 && forced_ambiguity == 0
     }
+
+    fn is_single(self, path_kind: PathKind) -> bool {
+        match path_kind {
+            PathKind::Inductive => matches!(
+                self,
+                HeadUsages { inductive: _, unknown: 0, coinductive: 0, forced_ambiguity: 0 },
+            ),
+            PathKind::Unknown => matches!(
+                self,
+                HeadUsages { inductive: 0, unknown: _, coinductive: 0, forced_ambiguity: 0 },
+            ),
+            PathKind::Coinductive => matches!(
+                self,
+                HeadUsages { inductive: 0, unknown: 0, coinductive: _, forced_ambiguity: 0 },
+            ),
+            PathKind::ForcedAmbiguity => matches!(
+                self,
+                HeadUsages { inductive: 0, unknown: 0, coinductive: 0, forced_ambiguity: _ },
+            ),
+        }
+    }
 }
 
 #[derive(Debug, Default)]
@@ -869,7 +888,7 @@ impl<D: Delegate<Cx = X>, X: Cx> SearchGraph<D> {
         }
 
         debug!("encountered stack overflow");
-        D::on_stack_overflow(cx, input)
+        D::stack_overflow_result(cx, input)
     }
 
     /// When reevaluating a goal with a changed provisional result, all provisional cache entry
@@ -888,7 +907,29 @@ impl<D: Delegate<Cx = X>, X: Cx> SearchGraph<D> {
             !entries.is_empty()
         });
     }
+}
 
+/// We need to rebase provisional cache entries when popping one of their cycle
+/// heads from the stack. This may not necessarily mean that we've actually
+/// reached a fixpoint for that cycle head, which impacts the way we rebase
+/// provisional cache entries.
+enum RebaseReason {
+    NoCycleUsages,
+    Ambiguity,
+    Overflow,
+    /// We've actually reached a fixpoint.
+    ///
+    /// This either happens in the first evaluation step for the cycle head.
+    /// In this case the used provisional result depends on the cycle `PathKind`.
+    /// We store this path kind to check whether the the provisional cache entry
+    /// we're rebasing relied on the same cycles.
+    ///
+    /// In later iterations cycles always return `stack_entry.provisional_result`
+    /// so we no longer depend on the `PathKind`. We store `None` in that case.
+    ReachedFixpoint(Option<PathKind>),
+}
+
+impl<D: Delegate<Cx = X>, X: Cx> SearchGraph<D, X> {
     /// A necessary optimization to handle complex solver cycles. A provisional cache entry
     /// relies on a set of cycle heads and the path towards these heads. When popping a cycle
     /// head from the stack after we've finished computing it, we can't be sure that the
@@ -908,8 +949,9 @@ impl<D: Delegate<Cx = X>, X: Cx> SearchGraph<D> {
     /// to me.
     fn rebase_provisional_cache_entries(
         &mut self,
+        cx: X,
         stack_entry: &StackEntry<X>,
-        mut mutate_result: impl FnMut(X::Input, X::Result) -> X::Result,
+        rebase_reason: RebaseReason,
     ) {
         let popped_head_index = self.stack.next_index();
         #[allow(rustc::potential_query_instability)]
@@ -927,6 +969,10 @@ impl<D: Delegate<Cx = X>, X: Cx> SearchGraph<D> {
                     return true;
                 };
 
+                let Some(new_highest_head_index) = heads.opt_highest_cycle_head_index() else {
+                    return false;
+                };
+
                 // We're rebasing an entry `e` over a head `p`. This head
                 // has a number of own heads `h` it depends on.
                 //
@@ -977,22 +1023,37 @@ impl<D: Delegate<Cx = X>, X: Cx> SearchGraph<D> {
                         let eph = ep.extend_with_paths(ph);
                         heads.insert(head_index, eph, head.usages);
                     }
-                }
 
-                let Some(head_index) = heads.opt_highest_cycle_head_index() else {
-                    return false;
-                };
+                    // The provisional cache entry does depend on the provisional result
+                    // of the popped cycle head. We need to mutate the result of our
+                    // provisional cache entry in case we did not reach a fixpoint.
+                    match rebase_reason {
+                        // If the cycle head does not actually depend on itself, then
+                        // the provisional result used by the provisional cache entry
+                        // is not actually equal to the final provisional result. We
+                        // need to discard the provisional cache entry in this case.
+                        RebaseReason::NoCycleUsages => return false,
+                        RebaseReason::Ambiguity => {
+                            *result = D::propagate_ambiguity(cx, input, *result);
+                        }
+                        RebaseReason::Overflow => *result = D::fixpoint_overflow_result(cx, input),
+                        RebaseReason::ReachedFixpoint(None) => {}
+                        RebaseReason::ReachedFixpoint(Some(path_kind)) => {
+                            if !popped_head.usages.is_single(path_kind) {
+                                return false;
+                            }
+                        }
+                    };
+                }
 
                 // We now care about the path from the next highest cycle head to the
                 // provisional cache entry.
                 *path_from_head = path_from_head.extend(Self::cycle_path_kind(
                     &self.stack,
                     stack_entry.step_kind_from_parent,
-                    head_index,
+                    new_highest_head_index,
                 ));
-                // Mutate the result of the provisional cache entry in case we did
-                // not reach a fixpoint.
-                *result = mutate_result(input, *result);
+
                 true
             });
             !entries.is_empty()
@@ -1209,33 +1270,19 @@ impl<D: Delegate<Cx = X>, X: Cx> SearchGraph<D> {
     /// Whether we've reached a fixpoint when evaluating a cycle head.
     fn reached_fixpoint(
         &mut self,
-        cx: X,
         stack_entry: &StackEntry<X>,
         usages: HeadUsages,
         result: X::Result,
-    ) -> bool {
+    ) -> Result<Option<PathKind>, ()> {
         let provisional_result = stack_entry.provisional_result;
-        if usages.is_empty() {
-            true
-        } else if let Some(provisional_result) = provisional_result {
-            provisional_result == result
+        if let Some(provisional_result) = provisional_result {
+            if provisional_result == result { Ok(None) } else { Err(()) }
+        } else if let Some(path_kind) = D::is_initial_provisional_result(result)
+            .filter(|&path_kind| usages.is_single(path_kind))
+        {
+            Ok(Some(path_kind))
         } else {
-            let check = |k| D::is_initial_provisional_result(cx, k, stack_entry.input, result);
-            match usages {
-                HeadUsages { inductive: _, unknown: 0, coinductive: 0, forced_ambiguity: 0 } => {
-                    check(PathKind::Inductive)
-                }
-                HeadUsages { inductive: 0, unknown: _, coinductive: 0, forced_ambiguity: 0 } => {
-                    check(PathKind::Unknown)
-                }
-                HeadUsages { inductive: 0, unknown: 0, coinductive: _, forced_ambiguity: 0 } => {
-                    check(PathKind::Coinductive)
-                }
-                HeadUsages { inductive: 0, unknown: 0, coinductive: 0, forced_ambiguity: _ } => {
-                    check(PathKind::ForcedAmbiguity)
-                }
-                _ => false,
-            }
+            Err(())
         }
     }
 
@@ -1280,8 +1327,19 @@ impl<D: Delegate<Cx = X>, X: Cx> SearchGraph<D> {
             // is equal to the provisional result of the previous iteration, or because
             // this was only the head of either coinductive or inductive cycles, and the
             // final result is equal to the initial response for that case.
-            if self.reached_fixpoint(cx, &stack_entry, usages, result) {
-                self.rebase_provisional_cache_entries(&stack_entry, |_, result| result);
+            if let Ok(fixpoint) = self.reached_fixpoint(&stack_entry, usages, result) {
+                self.rebase_provisional_cache_entries(
+                    cx,
+                    &stack_entry,
+                    RebaseReason::ReachedFixpoint(fixpoint),
+                );
+                return EvaluationResult::finalize(stack_entry, encountered_overflow, result);
+            } else if usages.is_empty() {
+                self.rebase_provisional_cache_entries(
+                    cx,
+                    &stack_entry,
+                    RebaseReason::NoCycleUsages,
+                );
                 return EvaluationResult::finalize(stack_entry, encountered_overflow, result);
             }
 
@@ -1298,9 +1356,7 @@ impl<D: Delegate<Cx = X>, X: Cx> SearchGraph<D> {
             // we also taint all provisional cache entries which depend on the
             // current goal.
             if D::is_ambiguous_result(result) {
-                self.rebase_provisional_cache_entries(&stack_entry, |input, _| {
-                    D::propagate_ambiguity(cx, input, result)
-                });
+                self.rebase_provisional_cache_entries(cx, &stack_entry, RebaseReason::Ambiguity);
                 return EvaluationResult::finalize(stack_entry, encountered_overflow, result);
             };
 
@@ -1309,10 +1365,8 @@ impl<D: Delegate<Cx = X>, X: Cx> SearchGraph<D> {
             i += 1;
             if i >= D::FIXPOINT_STEP_LIMIT {
                 debug!("canonical cycle overflow");
-                let result = D::on_fixpoint_overflow(cx, input);
-                self.rebase_provisional_cache_entries(&stack_entry, |input, _| {
-                    D::on_fixpoint_overflow(cx, input)
-                });
+                let result = D::fixpoint_overflow_result(cx, input);
+                self.rebase_provisional_cache_entries(cx, &stack_entry, RebaseReason::Overflow);
                 return EvaluationResult::finalize(stack_entry, encountered_overflow, result);
             }
 
diff --git a/compiler/rustc_type_ir/src/solve/mod.rs b/compiler/rustc_type_ir/src/solve/mod.rs
index 1a1606d8268..9d9a8e49847 100644
--- a/compiler/rustc_type_ir/src/solve/mod.rs
+++ b/compiler/rustc_type_ir/src/solve/mod.rs
@@ -109,19 +109,6 @@ pub struct QueryInput<I: Interner, P> {
 
 impl<I: Interner, P: Eq> Eq for QueryInput<I, P> {}
 
-/// Opaques that are defined in the inference context before a query is called.
-#[derive_where(Clone, Hash, PartialEq, Debug, Default; I: Interner)]
-#[derive(TypeVisitable_Generic, TypeFoldable_Generic)]
-#[cfg_attr(
-    feature = "nightly",
-    derive(Decodable_NoContext, Encodable_NoContext, HashStable_NoContext)
-)]
-pub struct PredefinedOpaquesData<I: Interner> {
-    pub opaque_types: Vec<(ty::OpaqueTypeKey<I>, I::Ty)>,
-}
-
-impl<I: Interner> Eq for PredefinedOpaquesData<I> {}
-
 /// Possible ways the given goal can be proven.
 #[derive_where(Clone, Copy, Hash, PartialEq, Debug; I: Interner)]
 pub enum CandidateSource<I: Interner> {