Merge ref 'c96a69059ecc' from rust-lang/rust

Pull recent changes from https://github.com/rust-lang/rust via Josh.

Upstream ref: c96a69059ecc618b519da385a6ccd03155aa0237
Filtered ref: 7b9552d4c39c31aabf6749629da2d4a7e6e1cd60

This merge was created using https://github.com/rust-lang/josh-sync.

15 files changed, 264 insertions, 447 deletions

diff --git a/compiler/rustc_codegen_ssa/src/back/link.rs b/compiler/rustc_codegen_ssa/src/back/link.rs
index 4a2425967e4..343cb0eeca9 100644
--- a/compiler/rustc_codegen_ssa/src/back/link.rs
+++ b/compiler/rustc_codegen_ssa/src/back/link.rs
@@ -2767,7 +2767,7 @@ fn add_upstream_rust_crates(
 
     if sess.target.is_like_aix {
         // Unlike ELF linkers, AIX doesn't feature `DT_SONAME` to override
-        // the dependency name when outputing a shared library. Thus, `ld` will
+        // the dependency name when outputting a shared library. Thus, `ld` will
         // use the full path to shared libraries as the dependency if passed it
         // by default unless `noipath` is passed.
         // https://www.ibm.com/docs/en/aix/7.3?topic=l-ld-command.
@@ -3051,7 +3051,7 @@ fn add_apple_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavo
     // Supported architecture names can be found in the source:
     // https://github.com/apple-oss-distributions/ld64/blob/ld64-951.9/src/abstraction/MachOFileAbstraction.hpp#L578-L648
     //
-    // Intentially verbose to ensure that the list always matches correctly
+    // Intentionally verbose to ensure that the list always matches correctly
     // with the list in the source above.
     let ld64_arch = match llvm_arch {
         "armv7k" => "armv7k",
@@ -3118,7 +3118,7 @@ fn add_apple_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavo
         // We do not currently know the actual SDK version though, so we have a few options:
         // 1. Use the minimum version supported by rustc.
         // 2. Use the same as the deployment target.
-        // 3. Use an arbitary recent version.
+        // 3. Use an arbitrary recent version.
         // 4. Omit the version.
         //
         // The first option is too low / too conservative, and means that users will not get the
diff --git a/compiler/rustc_codegen_ssa/src/back/linker.rs b/compiler/rustc_codegen_ssa/src/back/linker.rs
index cd08c0fc30f..1896f63bd2d 100644
--- a/compiler/rustc_codegen_ssa/src/back/linker.rs
+++ b/compiler/rustc_codegen_ssa/src/back/linker.rs
@@ -1794,7 +1794,10 @@ fn for_each_exported_symbols_include_dep<'tcx>(
     for (cnum, dep_format) in deps.iter_enumerated() {
         // For each dependency that we are linking to statically ...
         if *dep_format == Linkage::Static {
-            for &(symbol, info) in tcx.exported_symbols(cnum).iter() {
+            for &(symbol, info) in tcx.exported_non_generic_symbols(cnum).iter() {
+                callback(symbol, info, cnum);
+            }
+            for &(symbol, info) in tcx.exported_generic_symbols(cnum).iter() {
                 callback(symbol, info, cnum);
             }
         }
@@ -1870,8 +1873,28 @@ pub(crate) fn linked_symbols(
     crate_type: CrateType,
 ) -> Vec<(String, SymbolExportKind)> {
     match crate_type {
-        CrateType::Executable | CrateType::Cdylib | CrateType::Dylib | CrateType::Sdylib => (),
-        CrateType::Staticlib | CrateType::ProcMacro | CrateType::Rlib => {
+        CrateType::Executable
+        | CrateType::ProcMacro
+        | CrateType::Cdylib
+        | CrateType::Dylib
+        | CrateType::Sdylib => (),
+        CrateType::Staticlib | CrateType::Rlib => {
+            // These are not linked, so no need to generate symbols.o for them.
+            return Vec::new();
+        }
+    }
+
+    match tcx.sess.lto() {
+        Lto::No | Lto::ThinLocal => {}
+        Lto::Thin | Lto::Fat => {
+            // We really only need symbols from upstream rlibs to end up in the linked symbols list.
+            // The rest are in separate object files which the linker will always link in and
+            // doesn't have rules around the order in which they need to appear.
+            // When doing LTO, some of the symbols in the linked symbols list happen to be
+            // internalized by LTO, which then prevents referencing them from symbols.o. When doing
+            // LTO, all object files that get linked in will be local object files rather than
+            // pulled in from rlibs, so an empty linked symbols list works fine to avoid referencing
+            // all those internalized symbols from symbols.o.
             return Vec::new();
         }
     }
@@ -1882,6 +1905,7 @@ pub(crate) fn linked_symbols(
     for_each_exported_symbols_include_dep(tcx, crate_type, |symbol, info, cnum| {
         if info.level.is_below_threshold(export_threshold) && !tcx.is_compiler_builtins(cnum)
             || info.used
+            || info.rustc_std_internal_symbol
         {
             symbols.push((
                 symbol_export::linking_symbol_name_for_instance_in_crate(
diff --git a/compiler/rustc_codegen_ssa/src/back/metadata.rs b/compiler/rustc_codegen_ssa/src/back/metadata.rs
index d091c46d9c1..bf38c02e908 100644
--- a/compiler/rustc_codegen_ssa/src/back/metadata.rs
+++ b/compiler/rustc_codegen_ssa/src/back/metadata.rs
@@ -301,7 +301,7 @@ pub(super) fn elf_e_flags(architecture: Architecture, sess: &Session) -> u32 {
                 "n32" if !is_32bit => e_flags |= elf::EF_MIPS_ABI2,
                 "n64" if !is_32bit => {}
                 "" if is_32bit => e_flags |= elf::EF_MIPS_ABI_O32,
-                "" => sess.dcx().fatal("LLVM ABI must be specifed for 64-bit MIPS targets"),
+                "" => sess.dcx().fatal("LLVM ABI must be specified for 64-bit MIPS targets"),
                 s if is_32bit => {
                     sess.dcx().fatal(format!("invalid LLVM ABI `{}` for 32-bit MIPS target", s))
                 }
diff --git a/compiler/rustc_codegen_ssa/src/back/symbol_export.rs b/compiler/rustc_codegen_ssa/src/back/symbol_export.rs
index 19c005d418e..2f5eca2d6b2 100644
--- a/compiler/rustc_codegen_ssa/src/back/symbol_export.rs
+++ b/compiler/rustc_codegen_ssa/src/back/symbol_export.rs
@@ -131,6 +131,9 @@ fn reachable_non_generics_provider(tcx: TyCtxt<'_>, _: LocalCrate) -> DefIdMap<S
                 used: codegen_attrs.flags.contains(CodegenFnAttrFlags::USED_COMPILER)
                     || codegen_attrs.flags.contains(CodegenFnAttrFlags::USED_LINKER)
                     || used,
+                rustc_std_internal_symbol: codegen_attrs
+                    .flags
+                    .contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL),
             };
             (def_id.to_def_id(), info)
         })
@@ -143,6 +146,7 @@ fn reachable_non_generics_provider(tcx: TyCtxt<'_>, _: LocalCrate) -> DefIdMap<S
                 level: SymbolExportLevel::C,
                 kind: SymbolExportKind::Data,
                 used: false,
+                rustc_std_internal_symbol: false,
             },
         );
     }
@@ -164,7 +168,7 @@ fn is_reachable_non_generic_provider_extern(tcx: TyCtxt<'_>, def_id: DefId) -> b
     tcx.reachable_non_generics(def_id.krate).contains_key(&def_id)
 }
 
-fn exported_symbols_provider_local<'tcx>(
+fn exported_non_generic_symbols_provider_local<'tcx>(
     tcx: TyCtxt<'tcx>,
     _: LocalCrate,
 ) -> &'tcx [(ExportedSymbol<'tcx>, SymbolExportInfo)] {
@@ -191,6 +195,7 @@ fn exported_symbols_provider_local<'tcx>(
                         level: info.level,
                         kind: SymbolExportKind::Text,
                         used: info.used,
+                        rustc_std_internal_symbol: info.rustc_std_internal_symbol,
                     },
                 )
             })
@@ -207,6 +212,7 @@ fn exported_symbols_provider_local<'tcx>(
                 level: SymbolExportLevel::C,
                 kind: SymbolExportKind::Text,
                 used: false,
+                rustc_std_internal_symbol: false,
             },
         ));
     }
@@ -230,6 +236,7 @@ fn exported_symbols_provider_local<'tcx>(
                     level: SymbolExportLevel::Rust,
                     kind: SymbolExportKind::Text,
                     used: false,
+                    rustc_std_internal_symbol: true,
                 },
             ));
         }
@@ -250,6 +257,7 @@ fn exported_symbols_provider_local<'tcx>(
                     level: SymbolExportLevel::C,
                     kind: SymbolExportKind::Data,
                     used: false,
+                    rustc_std_internal_symbol: false,
                 },
             )
         }));
@@ -275,6 +283,7 @@ fn exported_symbols_provider_local<'tcx>(
                     level: SymbolExportLevel::C,
                     kind: SymbolExportKind::Data,
                     used: false,
+                    rustc_std_internal_symbol: false,
                 },
             )
         }));
@@ -292,10 +301,27 @@ fn exported_symbols_provider_local<'tcx>(
                 level: SymbolExportLevel::C,
                 kind: SymbolExportKind::Data,
                 used: true,
+                rustc_std_internal_symbol: false,
             },
         ));
     }
 
+    // Sort so we get a stable incr. comp. hash.
+    symbols.sort_by_cached_key(|s| s.0.symbol_name_for_local_instance(tcx));
+
+    tcx.arena.alloc_from_iter(symbols)
+}
+
+fn exported_generic_symbols_provider_local<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    _: LocalCrate,
+) -> &'tcx [(ExportedSymbol<'tcx>, SymbolExportInfo)] {
+    if !tcx.sess.opts.output_types.should_codegen() && !tcx.is_sdylib_interface_build() {
+        return &[];
+    }
+
+    let mut symbols: Vec<_> = vec![];
+
     if tcx.local_crate_exports_generics() {
         use rustc_middle::mir::mono::{Linkage, MonoItem, Visibility};
         use rustc_middle::ty::InstanceKind;
@@ -367,6 +393,8 @@ fn exported_symbols_provider_local<'tcx>(
                 }
             }
 
+            // Note: These all set rustc_std_internal_symbol to false as generic functions must not
+            // be marked with this attribute and we are only handling generic functions here.
             match *mono_item {
                 MonoItem::Fn(Instance { def: InstanceKind::Item(def), args }) => {
                     let has_generics = args.non_erasable_generics().next().is_some();
@@ -382,6 +410,7 @@ fn exported_symbols_provider_local<'tcx>(
                                 level: SymbolExportLevel::Rust,
                                 kind: SymbolExportKind::Text,
                                 used: false,
+                                rustc_std_internal_symbol: false,
                             },
                         ));
                     }
@@ -404,6 +433,7 @@ fn exported_symbols_provider_local<'tcx>(
                                 level: SymbolExportLevel::Rust,
                                 kind: SymbolExportKind::Text,
                                 used: false,
+                                rustc_std_internal_symbol: false,
                             },
                         ));
                     }
@@ -420,6 +450,7 @@ fn exported_symbols_provider_local<'tcx>(
                             level: SymbolExportLevel::Rust,
                             kind: SymbolExportKind::Text,
                             used: false,
+                            rustc_std_internal_symbol: false,
                         },
                     ));
                 }
@@ -430,6 +461,7 @@ fn exported_symbols_provider_local<'tcx>(
                             level: SymbolExportLevel::Rust,
                             kind: SymbolExportKind::Text,
                             used: false,
+                            rustc_std_internal_symbol: false,
                         },
                     ));
                 }
@@ -458,7 +490,7 @@ fn upstream_monomorphizations_provider(
     let async_drop_in_place_fn_def_id = tcx.lang_items().async_drop_in_place_fn();
 
     for &cnum in cnums.iter() {
-        for (exported_symbol, _) in tcx.exported_symbols(cnum).iter() {
+        for (exported_symbol, _) in tcx.exported_generic_symbols(cnum).iter() {
             let (def_id, args) = match *exported_symbol {
                 ExportedSymbol::Generic(def_id, args) => (def_id, args),
                 ExportedSymbol::DropGlue(ty) => {
@@ -480,10 +512,7 @@ fn upstream_monomorphizations_provider(
                 ExportedSymbol::AsyncDropGlue(def_id, ty) => (def_id, tcx.mk_args(&[ty.into()])),
                 ExportedSymbol::NonGeneric(..)
                 | ExportedSymbol::ThreadLocalShim(..)
-                | ExportedSymbol::NoDefId(..) => {
-                    // These are no monomorphizations
-                    continue;
-                }
+                | ExportedSymbol::NoDefId(..) => unreachable!("{exported_symbol:?}"),
             };
 
             let args_map = instances.entry(def_id).or_default();
@@ -538,7 +567,8 @@ fn is_unreachable_local_definition_provider(tcx: TyCtxt<'_>, def_id: LocalDefId)
 pub(crate) fn provide(providers: &mut Providers) {
     providers.reachable_non_generics = reachable_non_generics_provider;
     providers.is_reachable_non_generic = is_reachable_non_generic_provider_local;
-    providers.exported_symbols = exported_symbols_provider_local;
+    providers.exported_non_generic_symbols = exported_non_generic_symbols_provider_local;
+    providers.exported_generic_symbols = exported_generic_symbols_provider_local;
     providers.upstream_monomorphizations = upstream_monomorphizations_provider;
     providers.is_unreachable_local_definition = is_unreachable_local_definition_provider;
     providers.upstream_drop_glue_for = upstream_drop_glue_for_provider;
diff --git a/compiler/rustc_codegen_ssa/src/back/write.rs b/compiler/rustc_codegen_ssa/src/back/write.rs
index c3bfe4c13cd..8330e4f7af0 100644
--- a/compiler/rustc_codegen_ssa/src/back/write.rs
+++ b/compiler/rustc_codegen_ssa/src/back/write.rs
@@ -1124,8 +1124,9 @@ fn start_executing_work<B: ExtraBackendMethods>(
 
         let copy_symbols = |cnum| {
             let symbols = tcx
-                .exported_symbols(cnum)
+                .exported_non_generic_symbols(cnum)
                 .iter()
+                .chain(tcx.exported_generic_symbols(cnum))
                 .map(|&(s, lvl)| (symbol_name_for_instance_in_crate(tcx, s, cnum), lvl))
                 .collect();
             Arc::new(symbols)
diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs
index cc90271cd0c..102d4ea2fa6 100644
--- a/compiler/rustc_codegen_ssa/src/base.rs
+++ b/compiler/rustc_codegen_ssa/src/base.rs
@@ -6,7 +6,7 @@ use std::time::{Duration, Instant};
 use itertools::Itertools;
 use rustc_abi::FIRST_VARIANT;
 use rustc_ast as ast;
-use rustc_ast::expand::allocator::{ALLOCATOR_METHODS, AllocatorKind, global_fn_name};
+use rustc_ast::expand::allocator::AllocatorKind;
 use rustc_attr_data_structures::OptimizeAttr;
 use rustc_data_structures::fx::{FxHashMap, FxIndexSet};
 use rustc_data_structures::profiling::{get_resident_set_size, print_time_passes_entry};
@@ -262,28 +262,6 @@ pub(crate) fn unsize_ptr<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     }
 }
 
-/// Coerces `src` to `dst_ty` which is guaranteed to be a `dyn*` type.
-pub(crate) fn cast_to_dyn_star<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
-    bx: &mut Bx,
-    src: Bx::Value,
-    src_ty_and_layout: TyAndLayout<'tcx>,
-    dst_ty: Ty<'tcx>,
-    old_info: Option<Bx::Value>,
-) -> (Bx::Value, Bx::Value) {
-    debug!("cast_to_dyn_star: {:?} => {:?}", src_ty_and_layout.ty, dst_ty);
-    assert!(
-        matches!(dst_ty.kind(), ty::Dynamic(_, _, ty::DynStar)),
-        "destination type must be a dyn*"
-    );
-    let src = match bx.cx().type_kind(bx.cx().backend_type(src_ty_and_layout)) {
-        TypeKind::Pointer => src,
-        TypeKind::Integer => bx.inttoptr(src, bx.type_ptr()),
-        // FIXME(dyn-star): We probably have to do a bitcast first, then inttoptr.
-        kind => bug!("unexpected TypeKind for left-hand side of `dyn*` cast: {kind:?}"),
-    };
-    (src, unsized_info(bx, src_ty_and_layout.ty, dst_ty, old_info))
-}
-
 /// Coerces `src`, which is a reference to a value of type `src_ty`,
 /// to a value of type `dst_ty`, and stores the result in `dst`.
 pub(crate) fn coerce_unsized_into<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
@@ -1056,26 +1034,6 @@ impl CrateInfo {
                         .collect::<Vec<_>>();
                     symbols.sort_unstable_by(|a, b| a.0.cmp(&b.0));
                     linked_symbols.extend(symbols);
-                    if tcx.allocator_kind(()).is_some() {
-                        // At least one crate needs a global allocator. This crate may be placed
-                        // after the crate that defines it in the linker order, in which case some
-                        // linkers return an error. By adding the global allocator shim methods to
-                        // the linked_symbols list, linking the generated symbols.o will ensure that
-                        // circular dependencies involving the global allocator don't lead to linker
-                        // errors.
-                        linked_symbols.extend(ALLOCATOR_METHODS.iter().map(|method| {
-                            (
-                                add_prefix(
-                                    mangle_internal_symbol(
-                                        tcx,
-                                        global_fn_name(method.name).as_str(),
-                                    ),
-                                    SymbolExportKind::Text,
-                                ),
-                                SymbolExportKind::Text,
-                            )
-                        }));
-                    }
                 });
         }
 
diff --git a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
index 7bd27eb3ef1..2713ec07f97 100644
--- a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
+++ b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
@@ -1,15 +1,15 @@
 use std::str::FromStr;
 
-use rustc_abi::ExternAbi;
+use rustc_abi::{Align, ExternAbi};
 use rustc_ast::expand::autodiff_attrs::{AutoDiffAttrs, DiffActivity, DiffMode};
 use rustc_ast::{LitKind, MetaItem, MetaItemInner, attr};
 use rustc_attr_data_structures::{
-    AttributeKind, InlineAttr, InstructionSetAttr, OptimizeAttr, ReprAttr, find_attr,
+    AttributeKind, InlineAttr, InstructionSetAttr, OptimizeAttr, ReprAttr, UsedBy, find_attr,
 };
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LOCAL_CRATE, LocalDefId};
 use rustc_hir::weak_lang_items::WEAK_LANG_ITEMS;
-use rustc_hir::{self as hir, HirId, LangItem, lang_items};
+use rustc_hir::{self as hir, LangItem, lang_items};
 use rustc_middle::middle::codegen_fn_attrs::{
     CodegenFnAttrFlags, CodegenFnAttrs, PatchableFunctionEntry,
 };
@@ -87,7 +87,6 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
 
     let mut link_ordinal_span = None;
     let mut no_sanitize_span = None;
-    let mut mixed_export_name_no_mangle_lint_state = MixedExportNameAndNoMangleState::default();
 
     for attr in attrs.iter() {
         // In some cases, attribute are only valid on functions, but it's the `check_attr`
@@ -119,16 +118,18 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                         .max();
                 }
                 AttributeKind::Cold(_) => codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD,
+                AttributeKind::ExportName { name, .. } => {
+                    codegen_fn_attrs.export_name = Some(*name);
+                }
                 AttributeKind::Naked(_) => codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED,
                 AttributeKind::Align { align, .. } => codegen_fn_attrs.alignment = Some(*align),
+                AttributeKind::LinkName { name, .. } => codegen_fn_attrs.link_name = Some(*name),
+                AttributeKind::LinkSection { name, .. } => {
+                    codegen_fn_attrs.link_section = Some(*name)
+                }
                 AttributeKind::NoMangle(attr_span) => {
                     if tcx.opt_item_name(did.to_def_id()).is_some() {
                         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
-                        mixed_export_name_no_mangle_lint_state.track_no_mangle(
-                            *attr_span,
-                            tcx.local_def_id_to_hir_id(did),
-                            attr,
-                        );
                     } else {
                         tcx.dcx().emit_err(NoMangleNameless {
                             span: *attr_span,
@@ -140,6 +141,49 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                         });
                     }
                 }
+                AttributeKind::TargetFeature(features, attr_span) => {
+                    let Some(sig) = tcx.hir_node_by_def_id(did).fn_sig() else {
+                        tcx.dcx().span_delayed_bug(*attr_span, "target_feature applied to non-fn");
+                        continue;
+                    };
+                    let safe_target_features =
+                        matches!(sig.header.safety, hir::HeaderSafety::SafeTargetFeatures);
+                    codegen_fn_attrs.safe_target_features = safe_target_features;
+                    if safe_target_features {
+                        if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
+                            // The `#[target_feature]` attribute is allowed on
+                            // WebAssembly targets on all functions. Prior to stabilizing
+                            // the `target_feature_11` feature, `#[target_feature]` was
+                            // only permitted on unsafe functions because on most targets
+                            // execution of instructions that are not supported is
+                            // considered undefined behavior. For WebAssembly which is a
+                            // 100% safe target at execution time it's not possible to
+                            // execute undefined instructions, and even if a future
+                            // feature was added in some form for this it would be a
+                            // deterministic trap. There is no undefined behavior when
+                            // executing WebAssembly so `#[target_feature]` is allowed
+                            // on safe functions (but again, only for WebAssembly)
+                            //
+                            // Note that this is also allowed if `actually_rustdoc` so
+                            // if a target is documenting some wasm-specific code then
+                            // it's not spuriously denied.
+                            //
+                            // Now that `#[target_feature]` is permitted on safe functions,
+                            // this exception must still exist for allowing the attribute on
+                            // `main`, `start`, and other functions that are not usually
+                            // allowed.
+                        } else {
+                            check_target_feature_trait_unsafe(tcx, did, *attr_span);
+                        }
+                    }
+                    from_target_feature_attr(
+                        tcx,
+                        did,
+                        features,
+                        rust_target_features,
+                        &mut codegen_fn_attrs.target_features,
+                    );
+                }
                 AttributeKind::TrackCaller(attr_span) => {
                     let is_closure = tcx.is_closure_like(did.to_def_id());
 
@@ -163,6 +207,10 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                     }
                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER
                 }
+                AttributeKind::Used { used_by, .. } => match used_by {
+                    UsedBy::Compiler => codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED_COMPILER,
+                    UsedBy::Linker => codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED_LINKER,
+                },
                 _ => {}
             }
         }
@@ -184,99 +232,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
             sym::rustc_std_internal_symbol => {
                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL
             }
-            sym::used => {
-                let inner = attr.meta_item_list();
-                match inner.as_deref() {
-                    Some([item]) if item.has_name(sym::linker) => {
-                        if !tcx.features().used_with_arg() {
-                            feature_err(
-                                &tcx.sess,
-                                sym::used_with_arg,
-                                attr.span(),
-                                "`#[used(linker)]` is currently unstable",
-                            )
-                            .emit();
-                        }
-                        codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED_LINKER;
-                    }
-                    Some([item]) if item.has_name(sym::compiler) => {
-                        if !tcx.features().used_with_arg() {
-                            feature_err(
-                                &tcx.sess,
-                                sym::used_with_arg,
-                                attr.span(),
-                                "`#[used(compiler)]` is currently unstable",
-                            )
-                            .emit();
-                        }
-                        codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED_COMPILER;
-                    }
-                    Some(_) => {
-                        tcx.dcx().emit_err(errors::ExpectedUsedSymbol { span: attr.span() });
-                    }
-                    None => {
-                        // Unconditionally using `llvm.used` causes issues in handling
-                        // `.init_array` with the gold linker. Luckily gold has been
-                        // deprecated with GCC 15 and rustc now warns about using gold.
-                        codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED_LINKER
-                    }
-                }
-            }
             sym::thread_local => codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL,
-            sym::export_name => {
-                if let Some(s) = attr.value_str() {
-                    if s.as_str().contains('\0') {
-                        // `#[export_name = ...]` will be converted to a null-terminated string,
-                        // so it may not contain any null characters.
-                        tcx.dcx().emit_err(errors::NullOnExport { span: attr.span() });
-                    }
-                    codegen_fn_attrs.export_name = Some(s);
-                    mixed_export_name_no_mangle_lint_state.track_export_name(attr.span());
-                }
-            }
-            sym::target_feature => {
-                let Some(sig) = tcx.hir_node_by_def_id(did).fn_sig() else {
-                    tcx.dcx().span_delayed_bug(attr.span(), "target_feature applied to non-fn");
-                    continue;
-                };
-                let safe_target_features =
-                    matches!(sig.header.safety, hir::HeaderSafety::SafeTargetFeatures);
-                codegen_fn_attrs.safe_target_features = safe_target_features;
-                if safe_target_features {
-                    if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
-                        // The `#[target_feature]` attribute is allowed on
-                        // WebAssembly targets on all functions. Prior to stabilizing
-                        // the `target_feature_11` feature, `#[target_feature]` was
-                        // only permitted on unsafe functions because on most targets
-                        // execution of instructions that are not supported is
-                        // considered undefined behavior. For WebAssembly which is a
-                        // 100% safe target at execution time it's not possible to
-                        // execute undefined instructions, and even if a future
-                        // feature was added in some form for this it would be a
-                        // deterministic trap. There is no undefined behavior when
-                        // executing WebAssembly so `#[target_feature]` is allowed
-                        // on safe functions (but again, only for WebAssembly)
-                        //
-                        // Note that this is also allowed if `actually_rustdoc` so
-                        // if a target is documenting some wasm-specific code then
-                        // it's not spuriously denied.
-                        //
-                        // Now that `#[target_feature]` is permitted on safe functions,
-                        // this exception must still exist for allowing the attribute on
-                        // `main`, `start`, and other functions that are not usually
-                        // allowed.
-                    } else {
-                        check_target_feature_trait_unsafe(tcx, did, attr.span());
-                    }
-                }
-                from_target_feature_attr(
-                    tcx,
-                    did,
-                    attr,
-                    rust_target_features,
-                    &mut codegen_fn_attrs.target_features,
-                );
-            }
             sym::linkage => {
                 if let Some(val) = attr.value_str() {
                     let linkage = Some(linkage_by_name(tcx, did, val.as_str()));
@@ -300,17 +256,6 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                     }
                 }
             }
-            sym::link_section => {
-                if let Some(val) = attr.value_str() {
-                    if val.as_str().bytes().any(|b| b == 0) {
-                        let msg = format!("illegal null byte in link_section value: `{val}`");
-                        tcx.dcx().span_err(attr.span(), msg);
-                    } else {
-                        codegen_fn_attrs.link_section = Some(val);
-                    }
-                }
-            }
-            sym::link_name => codegen_fn_attrs.link_name = attr.value_str(),
             sym::link_ordinal => {
                 link_ordinal_span = Some(attr.span());
                 if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
@@ -444,12 +389,15 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
         }
     }
 
-    mixed_export_name_no_mangle_lint_state.lint_if_mixed(tcx);
-
-    // Apply the minimum function alignment here, so that individual backends don't have to.
+    // Apply the minimum function alignment here. This ensures that a function's alignment is
+    // determined by the `-C` flags of the crate it is defined in, not the `-C` flags of the crate
+    // it happens to be codegen'd (or const-eval'd) in.
     codegen_fn_attrs.alignment =
         Ord::max(codegen_fn_attrs.alignment, tcx.sess.opts.unstable_opts.min_function_alignment);
 
+    // On trait methods, inherit the `#[align]` of the trait's method prototype.
+    codegen_fn_attrs.alignment = Ord::max(codegen_fn_attrs.alignment, tcx.inherited_align(did));
+
     let inline_span;
     (codegen_fn_attrs.inline, inline_span) = if let Some((inline_attr, span)) =
         find_attr!(attrs, AttributeKind::Inline(i, span) => (*i, *span))
@@ -588,10 +536,10 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
             .map(|features| (features.name.as_str(), true))
             .collect(),
     ) {
-        let span = tcx
-            .get_attrs(did, sym::target_feature)
-            .next()
-            .map_or_else(|| tcx.def_span(did), |a| a.span());
+        let span =
+            find_attr!(tcx.get_all_attrs(did), AttributeKind::TargetFeature(_, span) => *span)
+                .unwrap_or_else(|| tcx.def_span(did));
+
         tcx.dcx()
             .create_err(errors::TargetFeatureDisableOrEnable {
                 features,
@@ -604,17 +552,26 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
     codegen_fn_attrs
 }
 
+/// If the provided DefId is a method in a trait impl, return the DefId of the method prototype.
+fn opt_trait_item(tcx: TyCtxt<'_>, def_id: DefId) -> Option<DefId> {
+    let impl_item = tcx.opt_associated_item(def_id)?;
+    match impl_item.container {
+        ty::AssocItemContainer::Impl => impl_item.trait_item_def_id,
+        _ => None,
+    }
+}
+
 /// Checks if the provided DefId is a method in a trait impl for a trait which has track_caller
 /// applied to the method prototype.
 fn should_inherit_track_caller(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
-    if let Some(impl_item) = tcx.opt_associated_item(def_id)
-        && let ty::AssocItemContainer::Impl = impl_item.container
-        && let Some(trait_item) = impl_item.trait_item_def_id
-    {
-        return tcx.codegen_fn_attrs(trait_item).flags.intersects(CodegenFnAttrFlags::TRACK_CALLER);
-    }
+    let Some(trait_item) = opt_trait_item(tcx, def_id) else { return false };
+    tcx.codegen_fn_attrs(trait_item).flags.intersects(CodegenFnAttrFlags::TRACK_CALLER)
+}
 
-    false
+/// If the provided DefId is a method in a trait impl, return the value of the `#[align]`
+/// attribute on the method prototype (if any).
+fn inherited_align<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> Option<Align> {
+    tcx.codegen_fn_attrs(opt_trait_item(tcx, def_id)?).alignment
 }
 
 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &hir::Attribute) -> Option<u16> {
@@ -672,49 +629,6 @@ fn check_link_name_xor_ordinal(
     }
 }
 
-#[derive(Default)]
-struct MixedExportNameAndNoMangleState<'a> {
-    export_name: Option<Span>,
-    hir_id: Option<HirId>,
-    no_mangle: Option<Span>,
-    no_mangle_attr: Option<&'a hir::Attribute>,
-}
-
-impl<'a> MixedExportNameAndNoMangleState<'a> {
-    fn track_export_name(&mut self, span: Span) {
-        self.export_name = Some(span);
-    }
-
-    fn track_no_mangle(&mut self, span: Span, hir_id: HirId, attr_name: &'a hir::Attribute) {
-        self.no_mangle = Some(span);
-        self.hir_id = Some(hir_id);
-        self.no_mangle_attr = Some(attr_name);
-    }
-
-    /// Emit diagnostics if the lint condition is met.
-    fn lint_if_mixed(self, tcx: TyCtxt<'_>) {
-        if let Self {
-            export_name: Some(export_name),
-            no_mangle: Some(no_mangle),
-            hir_id: Some(hir_id),
-            no_mangle_attr: Some(_),
-        } = self
-        {
-            tcx.emit_node_span_lint(
-                lint::builtin::UNUSED_ATTRIBUTES,
-                hir_id,
-                no_mangle,
-                errors::MixedExportNameAndNoMangle {
-                    no_mangle,
-                    no_mangle_attr: "#[unsafe(no_mangle)]".to_string(),
-                    export_name,
-                    removal_span: no_mangle,
-                },
-            );
-        }
-    }
-}
-
 /// We now check the #\[rustc_autodiff\] attributes which we generated from the #[autodiff(...)]
 /// macros. There are two forms. The pure one without args to mark primal functions (the functions
 /// being differentiated). The other form is #[rustc_autodiff(Mode, ActivityList)] on top of the
@@ -825,5 +739,6 @@ fn autodiff_attrs(tcx: TyCtxt<'_>, id: DefId) -> Option<AutoDiffAttrs> {
 }
 
 pub(crate) fn provide(providers: &mut Providers) {
-    *providers = Providers { codegen_fn_attrs, should_inherit_track_caller, ..*providers };
+    *providers =
+        Providers { codegen_fn_attrs, should_inherit_track_caller, inherited_align, ..*providers };
 }
diff --git a/compiler/rustc_codegen_ssa/src/errors.rs b/compiler/rustc_codegen_ssa/src/errors.rs
index caac0f83f9d..086c069745c 100644
--- a/compiler/rustc_codegen_ssa/src/errors.rs
+++ b/compiler/rustc_codegen_ssa/src/errors.rs
@@ -141,13 +141,6 @@ pub(crate) struct RequiresRustAbi {
 }
 
 #[derive(Diagnostic)]
-#[diag(codegen_ssa_null_on_export, code = E0648)]
-pub(crate) struct NullOnExport {
-    #[primary_span]
-    pub span: Span,
-}
-
-#[derive(Diagnostic)]
 #[diag(codegen_ssa_unsupported_instruction_set, code = E0779)]
 pub(crate) struct UnsupportedInstructionSet {
     #[primary_span]
@@ -734,13 +727,6 @@ pub struct UnknownArchiveKind<'a> {
 }
 
 #[derive(Diagnostic)]
-#[diag(codegen_ssa_expected_used_symbol)]
-pub(crate) struct ExpectedUsedSymbol {
-    #[primary_span]
-    pub span: Span,
-}
-
-#[derive(Diagnostic)]
 #[diag(codegen_ssa_multiple_main_functions)]
 #[help]
 pub(crate) struct MultipleMainFunctions {
@@ -1207,18 +1193,6 @@ pub(crate) struct ErrorCreatingImportLibrary<'a> {
 #[diag(codegen_ssa_aix_strip_not_used)]
 pub(crate) struct AixStripNotUsed;
 
-#[derive(LintDiagnostic)]
-#[diag(codegen_ssa_mixed_export_name_and_no_mangle)]
-pub(crate) struct MixedExportNameAndNoMangle {
-    #[label]
-    pub no_mangle: Span,
-    pub no_mangle_attr: String,
-    #[note]
-    pub export_name: Span,
-    #[suggestion(style = "verbose", code = "", applicability = "machine-applicable")]
-    pub removal_span: Span,
-}
-
 #[derive(Diagnostic, Debug)]
 pub(crate) enum XcrunError {
     #[diag(codegen_ssa_xcrun_failed_invoking)]
@@ -1318,3 +1292,14 @@ pub(crate) struct NoMangleNameless {
     pub span: Span,
     pub definition: String,
 }
+
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_feature_not_valid)]
+pub(crate) struct FeatureNotValid<'a> {
+    pub feature: &'a str,
+    #[primary_span]
+    #[label]
+    pub span: Span,
+    #[help]
+    pub plus_hint: bool,
+}
diff --git a/compiler/rustc_codegen_ssa/src/mir/block.rs b/compiler/rustc_codegen_ssa/src/mir/block.rs
index 3df97429e09..bde63fd501a 100644
--- a/compiler/rustc_codegen_ssa/src/mir/block.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/block.rs
@@ -628,50 +628,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     virtual_drop,
                 )
             }
-            ty::Dynamic(_, _, ty::DynStar) => {
-                // IN THIS ARM, WE HAVE:
-                // ty = *mut (dyn* Trait)
-                // which is: *mut exists<T: sizeof(T) == sizeof(usize)> (T, Vtable<T: Trait>)
-                //
-                // args = [ * ]
-                //          |
-                //          v
-                //      ( Data, Vtable )
-                //                |
-                //                v
-                //              /-------\
-                //              | ...   |
-                //              \-------/
-                //
-                //
-                // WE CAN CONVERT THIS INTO THE ABOVE LOGIC BY DOING
-                //
-                // data = &(*args[0]).0    // gives a pointer to Data above (really the same pointer)
-                // vtable = (*args[0]).1   // loads the vtable out
-                // (data, vtable)          // an equivalent Rust `*mut dyn Trait`
-                //
-                // SO THEN WE CAN USE THE ABOVE CODE.
-                let virtual_drop = Instance {
-                    def: ty::InstanceKind::Virtual(drop_fn.def_id(), 0), // idx 0: the drop function
-                    args: drop_fn.args,
-                };
-                debug!("ty = {:?}", ty);
-                debug!("drop_fn = {:?}", drop_fn);
-                debug!("args = {:?}", args);
-                let fn_abi = bx.fn_abi_of_instance(virtual_drop, ty::List::empty());
-                let meta_ptr = place.project_field(bx, 1);
-                let meta = bx.load_operand(meta_ptr);
-                // Truncate vtable off of args list
-                args = &args[..1];
-                debug!("args' = {:?}", args);
-                (
-                    true,
-                    meth::VirtualIndex::from_index(ty::COMMON_VTABLE_ENTRIES_DROPINPLACE)
-                        .get_optional_fn(bx, meta.immediate(), ty, fn_abi),
-                    fn_abi,
-                    virtual_drop,
-                )
-            }
             _ => (
                 false,
                 bx.get_fn_addr(drop_fn),
@@ -776,6 +732,12 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 // `#[track_caller]` adds an implicit argument.
                 (LangItem::PanicNullPointerDereference, vec![location])
             }
+            AssertKind::InvalidEnumConstruction(source) => {
+                let source = self.codegen_operand(bx, source).immediate();
+                // It's `fn panic_invalid_enum_construction(source: u128)`,
+                // `#[track_caller]` adds an implicit argument.
+                (LangItem::PanicInvalidEnumConstruction, vec![source, location])
+            }
             _ => {
                 // It's `pub fn panic_...()` and `#[track_caller]` adds an implicit argument.
                 (msg.panic_function(), vec![location])
@@ -1102,33 +1064,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                         llargs.push(data_ptr);
                         continue;
                     }
-                    Immediate(_) => {
-                        // See comment above explaining why we peel these newtypes
-                        while !op.layout.ty.is_raw_ptr() && !op.layout.ty.is_ref() {
-                            let (idx, _) = op.layout.non_1zst_field(bx).expect(
-                                "not exactly one non-1-ZST field in a `DispatchFromDyn` type",
-                            );
-                            op = op.extract_field(self, bx, idx.as_usize());
-                        }
-
-                        // Make sure that we've actually unwrapped the rcvr down
-                        // to a pointer or ref to `dyn* Trait`.
-                        if !op.layout.ty.builtin_deref(true).unwrap().is_dyn_star() {
-                            span_bug!(fn_span, "can't codegen a virtual call on {:#?}", op);
-                        }
-                        let place = op.deref(bx.cx());
-                        let data_place = place.project_field(bx, 0);
-                        let meta_place = place.project_field(bx, 1);
-                        let meta = bx.load_operand(meta_place);
-                        llfn = Some(meth::VirtualIndex::from_index(idx).get_fn(
-                            bx,
-                            meta.immediate(),
-                            op.layout.ty,
-                            fn_abi,
-                        ));
-                        llargs.push(data_place.val.llval);
-                        continue;
-                    }
                     _ => {
                         span_bug!(fn_span, "can't codegen a virtual call on {:#?}", op);
                     }
diff --git a/compiler/rustc_codegen_ssa/src/mir/intrinsic.rs b/compiler/rustc_codegen_ssa/src/mir/intrinsic.rs
index 27fcab8ed2d..fc95f62b4a4 100644
--- a/compiler/rustc_codegen_ssa/src/mir/intrinsic.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/intrinsic.rs
@@ -1,7 +1,7 @@
 use rustc_abi::WrappingRange;
-use rustc_middle::bug;
 use rustc_middle::mir::SourceInfo;
 use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_middle::{bug, span_bug};
 use rustc_session::config::OptLevel;
 use rustc_span::sym;
 
@@ -98,6 +98,27 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             discr.to_atomic_ordering()
         };
 
+        if args.is_empty() {
+            match name {
+                sym::abort
+                | sym::unreachable
+                | sym::cold_path
+                | sym::breakpoint
+                | sym::assert_zero_valid
+                | sym::assert_mem_uninitialized_valid
+                | sym::assert_inhabited
+                | sym::ub_checks
+                | sym::contract_checks
+                | sym::atomic_fence
+                | sym::atomic_singlethreadfence
+                | sym::caller_location => {}
+                _ => {
+                    span_bug!(span, "nullary intrinsic {name} must either be in a const block or explicitly opted out because it is inherently a runtime intrinsic
+");
+                }
+            }
+        }
+
         let llval = match name {
             sym::abort => {
                 bx.abort();
@@ -150,10 +171,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 }
                 value
             }
-            sym::needs_drop | sym::type_id | sym::type_name | sym::variant_count => {
-                let value = bx.tcx().const_eval_instance(bx.typing_env(), instance, span).unwrap();
-                OperandRef::from_const(bx, value, result.layout.ty).immediate_or_packed_pair(bx)
-            }
             sym::arith_offset => {
                 let ty = fn_args.type_at(0);
                 let layout = bx.layout_of(ty);
diff --git a/compiler/rustc_codegen_ssa/src/mir/mod.rs b/compiler/rustc_codegen_ssa/src/mir/mod.rs
index 66c4af4c935..10b44a1faf0 100644
--- a/compiler/rustc_codegen_ssa/src/mir/mod.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/mod.rs
@@ -354,15 +354,15 @@ fn optimize_use_clone<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
 
             let destination_block = target.unwrap();
 
-            bb.statements.push(mir::Statement {
-                source_info: bb.terminator().source_info,
-                kind: mir::StatementKind::Assign(Box::new((
+            bb.statements.push(mir::Statement::new(
+                bb.terminator().source_info,
+                mir::StatementKind::Assign(Box::new((
                     *destination,
                     mir::Rvalue::Use(mir::Operand::Copy(
                         arg_place.project_deeper(&[mir::ProjectionElem::Deref], tcx),
                     )),
                 ))),
-            });
+            ));
 
             bb.terminator_mut().kind = mir::TerminatorKind::Goto { target: destination_block };
         }
diff --git a/compiler/rustc_codegen_ssa/src/mir/operand.rs b/compiler/rustc_codegen_ssa/src/mir/operand.rs
index 99957c67708..da615cc9a00 100644
--- a/compiler/rustc_codegen_ssa/src/mir/operand.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/operand.rs
@@ -479,17 +479,8 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> {
                     _ => (tag_imm, bx.cx().immediate_backend_type(tag_op.layout)),
                 };
 
-                // Layout ensures that we only get here for cases where the discriminant
+                // `layout_sanity_check` ensures that we only get here for cases where the discriminant
                 // value and the variant index match, since that's all `Niche` can encode.
-                // But for emphasis and debugging, let's double-check one anyway.
-                debug_assert_eq!(
-                    self.layout
-                        .ty
-                        .discriminant_for_variant(bx.tcx(), untagged_variant)
-                        .unwrap()
-                        .val,
-                    u128::from(untagged_variant.as_u32()),
-                );
 
                 let relative_max = niche_variants.end().as_u32() - niche_variants.start().as_u32();
 
diff --git a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
index db5ac6a514f..60cf4e28b5a 100644
--- a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
@@ -468,12 +468,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                             bug!("unexpected non-pair operand");
                         }
                     }
-                    mir::CastKind::PointerCoercion(PointerCoercion::DynStar, _) => {
-                        let (lldata, llextra) = operand.val.pointer_parts();
-                        let (lldata, llextra) =
-                            base::cast_to_dyn_star(bx, lldata, operand.layout, cast.ty, llextra);
-                        OperandValue::Pair(lldata, llextra)
-                    }
                     | mir::CastKind::IntToInt
                     | mir::CastKind::FloatToInt
                     | mir::CastKind::FloatToFloat
@@ -1123,7 +1117,7 @@ pub(super) fn transmute_immediate<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     // While optimizations will remove no-op transmutes, they might still be
     // there in debug or things that aren't no-op in MIR because they change
     // the Rust type but not the underlying layout/niche.
-    if from_scalar == to_scalar {
+    if from_scalar == to_scalar && from_backend_ty == to_backend_ty {
         return imm;
     }
 
@@ -1142,13 +1136,7 @@ pub(super) fn transmute_immediate<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     assume_scalar_range(bx, imm, from_scalar, from_backend_ty);
 
     imm = match (from_scalar.primitive(), to_scalar.primitive()) {
-        (Int(..) | Float(_), Int(..) | Float(_)) => {
-            if from_backend_ty == to_backend_ty {
-                imm
-            } else {
-                bx.bitcast(imm, to_backend_ty)
-            }
-        }
+        (Int(..) | Float(_), Int(..) | Float(_)) => bx.bitcast(imm, to_backend_ty),
         (Pointer(..), Pointer(..)) => bx.pointercast(imm, to_backend_ty),
         (Int(..), Pointer(..)) => bx.ptradd(bx.const_null(bx.type_ptr()), imm),
         (Pointer(..), Int(..)) => {
diff --git a/compiler/rustc_codegen_ssa/src/target_features.rs b/compiler/rustc_codegen_ssa/src/target_features.rs
index 67ac619091b..53df99993f0 100644
--- a/compiler/rustc_codegen_ssa/src/target_features.rs
+++ b/compiler/rustc_codegen_ssa/src/target_features.rs
@@ -1,8 +1,6 @@
 use rustc_attr_data_structures::InstructionSetAttr;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
 use rustc_data_structures::unord::{UnordMap, UnordSet};
-use rustc_errors::Applicability;
-use rustc_hir as hir;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LOCAL_CRATE, LocalDefId};
 use rustc_middle::middle::codegen_fn_attrs::TargetFeature;
@@ -12,110 +10,85 @@ use rustc_session::Session;
 use rustc_session::lint::builtin::AARCH64_SOFTFLOAT_NEON;
 use rustc_session::parse::feature_err;
 use rustc_span::{Span, Symbol, sym};
-use rustc_target::target_features::{self, RUSTC_SPECIFIC_FEATURES, Stability};
+use rustc_target::target_features::{RUSTC_SPECIFIC_FEATURES, Stability};
 use smallvec::SmallVec;
 
-use crate::errors;
+use crate::errors::FeatureNotValid;
+use crate::{errors, target_features};
 
 /// Compute the enabled target features from the `#[target_feature]` function attribute.
 /// Enabled target features are added to `target_features`.
 pub(crate) fn from_target_feature_attr(
     tcx: TyCtxt<'_>,
     did: LocalDefId,
-    attr: &hir::Attribute,
+    features: &[(Symbol, Span)],
     rust_target_features: &UnordMap<String, target_features::Stability>,
     target_features: &mut Vec<TargetFeature>,
 ) {
-    let Some(list) = attr.meta_item_list() else { return };
-    let bad_item = |span| {
-        let msg = "malformed `target_feature` attribute input";
-        let code = "enable = \"..\"";
-        tcx.dcx()
-            .struct_span_err(span, msg)
-            .with_span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
-            .emit();
-    };
     let rust_features = tcx.features();
     let abi_feature_constraints = tcx.sess.target.abi_required_features();
-    for item in list {
-        // Only `enable = ...` is accepted in the meta-item list.
-        if !item.has_name(sym::enable) {
-            bad_item(item.span());
-            continue;
-        }
-
-        // Must be of the form `enable = "..."` (a string).
-        let Some(value) = item.value_str() else {
-            bad_item(item.span());
+    for &(feature, feature_span) in features {
+        let feature_str = feature.as_str();
+        let Some(stability) = rust_target_features.get(feature_str) else {
+            let plus_hint = feature_str
+                .strip_prefix('+')
+                .is_some_and(|stripped| rust_target_features.contains_key(stripped));
+            tcx.dcx().emit_err(FeatureNotValid {
+                feature: feature_str,
+                span: feature_span,
+                plus_hint,
+            });
             continue;
         };
 
-        // We allow comma separation to enable multiple features.
-        for feature in value.as_str().split(',') {
-            let Some(stability) = rust_target_features.get(feature) else {
-                let msg = format!("the feature named `{feature}` is not valid for this target");
-                let mut err = tcx.dcx().struct_span_err(item.span(), msg);
-                err.span_label(item.span(), format!("`{feature}` is not valid for this target"));
-                if let Some(stripped) = feature.strip_prefix('+') {
-                    let valid = rust_target_features.contains_key(stripped);
-                    if valid {
-                        err.help("consider removing the leading `+` in the feature name");
-                    }
-                }
-                err.emit();
-                continue;
-            };
-
-            // Only allow target features whose feature gates have been enabled
-            // and which are permitted to be toggled.
-            if let Err(reason) = stability.toggle_allowed() {
-                tcx.dcx().emit_err(errors::ForbiddenTargetFeatureAttr {
-                    span: item.span(),
-                    feature,
-                    reason,
-                });
-            } else if let Some(nightly_feature) = stability.requires_nightly()
-                && !rust_features.enabled(nightly_feature)
-            {
-                feature_err(
-                    &tcx.sess,
-                    nightly_feature,
-                    item.span(),
-                    format!("the target feature `{feature}` is currently unstable"),
-                )
-                .emit();
-            } else {
-                // Add this and the implied features.
-                let feature_sym = Symbol::intern(feature);
-                for &name in tcx.implied_target_features(feature_sym) {
-                    // But ensure the ABI does not forbid enabling this.
-                    // Here we do assume that the backend doesn't add even more implied features
-                    // we don't know about, at least no features that would have ABI effects!
-                    // We skip this logic in rustdoc, where we want to allow all target features of
-                    // all targets, so we can't check their ABI compatibility and anyway we are not
-                    // generating code so "it's fine".
-                    if !tcx.sess.opts.actually_rustdoc {
-                        if abi_feature_constraints.incompatible.contains(&name.as_str()) {
-                            // For "neon" specifically, we emit an FCW instead of a hard error.
-                            // See <https://github.com/rust-lang/rust/issues/134375>.
-                            if tcx.sess.target.arch == "aarch64" && name.as_str() == "neon" {
-                                tcx.emit_node_span_lint(
-                                    AARCH64_SOFTFLOAT_NEON,
-                                    tcx.local_def_id_to_hir_id(did),
-                                    item.span(),
-                                    errors::Aarch64SoftfloatNeon,
-                                );
-                            } else {
-                                tcx.dcx().emit_err(errors::ForbiddenTargetFeatureAttr {
-                                    span: item.span(),
-                                    feature: name.as_str(),
-                                    reason: "this feature is incompatible with the target ABI",
-                                });
-                            }
+        // Only allow target features whose feature gates have been enabled
+        // and which are permitted to be toggled.
+        if let Err(reason) = stability.toggle_allowed() {
+            tcx.dcx().emit_err(errors::ForbiddenTargetFeatureAttr {
+                span: feature_span,
+                feature: feature_str,
+                reason,
+            });
+        } else if let Some(nightly_feature) = stability.requires_nightly()
+            && !rust_features.enabled(nightly_feature)
+        {
+            feature_err(
+                &tcx.sess,
+                nightly_feature,
+                feature_span,
+                format!("the target feature `{feature}` is currently unstable"),
+            )
+            .emit();
+        } else {
+            // Add this and the implied features.
+            for &name in tcx.implied_target_features(feature) {
+                // But ensure the ABI does not forbid enabling this.
+                // Here we do assume that the backend doesn't add even more implied features
+                // we don't know about, at least no features that would have ABI effects!
+                // We skip this logic in rustdoc, where we want to allow all target features of
+                // all targets, so we can't check their ABI compatibility and anyway we are not
+                // generating code so "it's fine".
+                if !tcx.sess.opts.actually_rustdoc {
+                    if abi_feature_constraints.incompatible.contains(&name.as_str()) {
+                        // For "neon" specifically, we emit an FCW instead of a hard error.
+                        // See <https://github.com/rust-lang/rust/issues/134375>.
+                        if tcx.sess.target.arch == "aarch64" && name.as_str() == "neon" {
+                            tcx.emit_node_span_lint(
+                                AARCH64_SOFTFLOAT_NEON,
+                                tcx.local_def_id_to_hir_id(did),
+                                feature_span,
+                                errors::Aarch64SoftfloatNeon,
+                            );
+                        } else {
+                            tcx.dcx().emit_err(errors::ForbiddenTargetFeatureAttr {
+                                span: feature_span,
+                                feature: name.as_str(),
+                                reason: "this feature is incompatible with the target ABI",
+                            });
                         }
                     }
-                    target_features.push(TargetFeature { name, implied: name != feature_sym })
                 }
+                target_features.push(TargetFeature { name, implied: name != feature })
             }
         }
     }
@@ -457,7 +430,7 @@ pub(crate) fn provide(providers: &mut Providers) {
                                     // one, just keep it.
                                 }
                                 _ => {
-                                    // Overwrite stabilite.
+                                    // Overwrite stability.
                                     occupied_entry.insert(stability);
                                 }
                             }
diff --git a/compiler/rustc_codegen_ssa/src/traits/builder.rs b/compiler/rustc_codegen_ssa/src/traits/builder.rs
index d19de6f5d26..9d367748c2a 100644
--- a/compiler/rustc_codegen_ssa/src/traits/builder.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/builder.rs
@@ -87,7 +87,7 @@ pub trait BuilderMethods<'a, 'tcx>:
     //
     // This function is opt-in for back ends.
     //
-    // The default implementation calls `self.expect()` before emiting the branch
+    // The default implementation calls `self.expect()` before emitting the branch
     // by calling `self.cond_br()`
     fn cond_br_with_expect(
         &mut self,