Merge from rustc

37 files changed, 448 insertions, 205 deletions

diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/ffi.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/ffi.rs
index cabdd310d1f..d7a4f105f3c 100644
--- a/compiler/rustc_codegen_llvm/src/coverageinfo/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/ffi.rs
@@ -1,5 +1,5 @@
 use rustc_middle::mir::coverage::{
-    CodeRegion, ConditionInfo, CounterId, CovTerm, DecisionInfo, ExpressionId, MappingKind,
+    ConditionInfo, CounterId, CovTerm, DecisionInfo, ExpressionId, MappingKind, SourceRegion,
 };
 
 /// Must match the layout of `LLVMRustCounterKind`.
@@ -236,9 +236,10 @@ impl CounterMappingRegion {
     pub(crate) fn from_mapping(
         mapping_kind: &MappingKind,
         local_file_id: u32,
-        code_region: &CodeRegion,
+        source_region: &SourceRegion,
     ) -> Self {
-        let &CodeRegion { file_name: _, start_line, start_col, end_line, end_col } = code_region;
+        let &SourceRegion { file_name: _, start_line, start_col, end_line, end_col } =
+            source_region;
         match *mapping_kind {
             MappingKind::Code(term) => Self::code_region(
                 Counter::from_term(term),
diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/map_data.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/map_data.rs
index 44eafab6060..5ed640b840e 100644
--- a/compiler/rustc_codegen_llvm/src/coverageinfo/map_data.rs
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/map_data.rs
@@ -2,8 +2,8 @@ use rustc_data_structures::captures::Captures;
 use rustc_data_structures::fx::FxIndexSet;
 use rustc_index::bit_set::BitSet;
 use rustc_middle::mir::coverage::{
-    CodeRegion, CounterId, CovTerm, Expression, ExpressionId, FunctionCoverageInfo, Mapping,
-    MappingKind, Op,
+    CounterId, CovTerm, Expression, ExpressionId, FunctionCoverageInfo, Mapping, MappingKind, Op,
+    SourceRegion,
 };
 use rustc_middle::ty::Instance;
 use rustc_span::Symbol;
@@ -201,7 +201,7 @@ impl<'tcx> FunctionCoverage<'tcx> {
 
     /// Returns an iterator over all filenames used by this function's mappings.
     pub(crate) fn all_file_names(&self) -> impl Iterator<Item = Symbol> + Captures<'_> {
-        self.function_coverage_info.mappings.iter().map(|mapping| mapping.code_region.file_name)
+        self.function_coverage_info.mappings.iter().map(|mapping| mapping.source_region.file_name)
     }
 
     /// Convert this function's coverage expression data into a form that can be
@@ -230,12 +230,12 @@ impl<'tcx> FunctionCoverage<'tcx> {
     /// that will be used by `mapgen` when preparing for FFI.
     pub(crate) fn counter_regions(
         &self,
-    ) -> impl Iterator<Item = (MappingKind, &CodeRegion)> + ExactSizeIterator {
+    ) -> impl Iterator<Item = (MappingKind, &SourceRegion)> + ExactSizeIterator {
         self.function_coverage_info.mappings.iter().map(move |mapping| {
-            let Mapping { kind, code_region } = mapping;
+            let Mapping { kind, source_region } = mapping;
             let kind =
                 kind.map_terms(|term| if self.is_zero_term(term) { CovTerm::Zero } else { term });
-            (kind, code_region)
+            (kind, source_region)
         })
     }
 
diff --git a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
index 4ab20c154cc..209750d6ba6 100644
--- a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
+++ b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
@@ -1,5 +1,6 @@
 use rustc_ast::{ast, attr, MetaItemKind, NestedMetaItem};
 use rustc_attr::{list_contains_name, InlineAttr, InstructionSetAttr, OptimizeAttr};
+use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::codes::*;
 use rustc_errors::{struct_span_code_err, DiagMessage, SubdiagMessage};
 use rustc_hir as hir;
@@ -8,7 +9,7 @@ use rustc_hir::def_id::{DefId, LocalDefId, LOCAL_CRATE};
 use rustc_hir::weak_lang_items::WEAK_LANG_ITEMS;
 use rustc_hir::{lang_items, LangItem};
 use rustc_middle::middle::codegen_fn_attrs::{
-    CodegenFnAttrFlags, CodegenFnAttrs, PatchableFunctionEntry,
+    CodegenFnAttrFlags, CodegenFnAttrs, PatchableFunctionEntry, TargetFeature,
 };
 use rustc_middle::mir::mono::Linkage;
 use rustc_middle::query::Providers;
@@ -17,6 +18,7 @@ use rustc_session::lint;
 use rustc_session::parse::feature_err;
 use rustc_span::symbol::Ident;
 use rustc_span::{sym, Span};
+use rustc_target::abi::VariantIdx;
 use rustc_target::spec::{abi, SanitizerSet};
 
 use crate::errors;
@@ -78,6 +80,13 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
     let mut link_ordinal_span = None;
     let mut no_sanitize_span = None;
 
+    let fn_sig_outer = || {
+        use DefKind::*;
+
+        let def_kind = tcx.def_kind(did);
+        if let Fn | AssocFn | Variant | Ctor(..) = def_kind { Some(tcx.fn_sig(did)) } else { None }
+    };
+
     for attr in attrs.iter() {
         // In some cases, attribute are only valid on functions, but it's the `check_attr`
         // pass that check that they aren't used anywhere else, rather this module.
@@ -85,16 +94,12 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
         // functions (such as calling `fn_sig`, which ICEs if given a non-function). We also
         // report a delayed bug, just in case `check_attr` isn't doing its job.
         let fn_sig = || {
-            use DefKind::*;
-
-            let def_kind = tcx.def_kind(did);
-            if let Fn | AssocFn | Variant | Ctor(..) = def_kind {
-                Some(tcx.fn_sig(did))
-            } else {
+            let sig = fn_sig_outer();
+            if sig.is_none() {
                 tcx.dcx()
                     .span_delayed_bug(attr.span, "this attribute can only be applied to functions");
-                None
             }
+            sig
         };
 
         let Some(Ident { name, .. }) = attr.ident() else {
@@ -613,7 +618,93 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
         }
     }
 
-    // If a function uses #[target_feature] it can't be inlined into general
+    if let Some(sig) = fn_sig_outer() {
+        // Collect target features from types reachable from arguments.
+        // We define a type as "reachable" if:
+        //  - it is a function argument
+        //  - it is a field of a reachable struct
+        //  - there is a reachable reference to it
+        // FIXME(struct_target_features): we may want to cache the result of this computation.
+        let mut visited_types = FxHashSet::default();
+        let mut reachable_types: Vec<_> = sig.skip_binder().inputs().skip_binder().to_owned();
+        let mut additional_tf = vec![];
+
+        while let Some(ty) = reachable_types.pop() {
+            if visited_types.contains(&ty) {
+                continue;
+            }
+            visited_types.insert(ty);
+            match ty.kind() {
+                ty::Alias(..) => {
+                    if let Ok(t) =
+                        tcx.try_normalize_erasing_regions(tcx.param_env(did.to_def_id()), ty)
+                    {
+                        reachable_types.push(t)
+                    }
+                }
+
+                ty::Ref(_, inner, _) => reachable_types.push(*inner),
+                ty::Tuple(tys) => reachable_types.extend(tys.iter()),
+                ty::Adt(adt_def, args) => {
+                    additional_tf.extend_from_slice(tcx.struct_target_features(adt_def.did()));
+                    // This only recurses into structs as i.e. an Option<TargetFeature> is an ADT
+                    // that doesn't actually always contain a TargetFeature.
+                    if adt_def.is_struct() {
+                        reachable_types.extend(
+                            adt_def
+                                .variant(VariantIdx::from_usize(0))
+                                .fields
+                                .iter()
+                                .map(|field| field.ty(tcx, args)),
+                        );
+                    }
+                }
+                ty::Bool
+                | ty::Char
+                | ty::Int(..)
+                | ty::Uint(..)
+                | ty::Float(..)
+                | ty::Foreign(..)
+                | ty::Str
+                | ty::Array(..)
+                | ty::Pat(..)
+                | ty::Slice(..)
+                | ty::RawPtr(..)
+                | ty::FnDef(..)
+                | ty::FnPtr(..)
+                | ty::Dynamic(..)
+                | ty::Closure(..)
+                | ty::CoroutineClosure(..)
+                | ty::Coroutine(..)
+                | ty::CoroutineWitness(..)
+                | ty::Never
+                | ty::Param(..)
+                | ty::Bound(..)
+                | ty::Placeholder(..)
+                | ty::Infer(..)
+                | ty::Error(..) => (),
+            }
+        }
+
+        // FIXME(struct_target_features): is this really necessary?
+        if !additional_tf.is_empty() && sig.skip_binder().abi() != abi::Abi::Rust {
+            tcx.dcx().span_err(
+                tcx.hir().span(tcx.local_def_id_to_hir_id(did)),
+                "cannot use a struct with target features in a function with non-Rust ABI",
+            );
+        }
+        if !additional_tf.is_empty() && codegen_fn_attrs.inline == InlineAttr::Always {
+            tcx.dcx().span_err(
+                tcx.hir().span(tcx.local_def_id_to_hir_id(did)),
+                "cannot use a struct with target features in a #[inline(always)] function",
+            );
+        }
+        codegen_fn_attrs
+            .target_features
+            .extend(additional_tf.iter().map(|tf| TargetFeature { implied: true, ..*tf }));
+    }
+
+    // If a function uses non-default target_features it can't be inlined into general
     // purpose functions as they wouldn't have the right target features
     // enabled. For that reason we also forbid #[inline(always)] as it can't be
     // respected.
@@ -758,6 +849,20 @@ fn check_link_name_xor_ordinal(
     }
 }
 
+fn struct_target_features(tcx: TyCtxt<'_>, def_id: LocalDefId) -> &[TargetFeature] {
+    let mut features = vec![];
+    let supported_features = tcx.supported_target_features(LOCAL_CRATE);
+    for attr in tcx.get_attrs(def_id, sym::target_feature) {
+        from_target_feature(tcx, attr, supported_features, &mut features);
+    }
+    tcx.arena.alloc_slice(&features)
+}
+
 pub fn provide(providers: &mut Providers) {
-    *providers = Providers { codegen_fn_attrs, should_inherit_track_caller, ..*providers };
+    *providers = Providers {
+        codegen_fn_attrs,
+        should_inherit_track_caller,
+        struct_target_features,
+        ..*providers
+    };
 }
diff --git a/compiler/rustc_const_eval/messages.ftl b/compiler/rustc_const_eval/messages.ftl
index d7d64180ec9..db788b6b151 100644
--- a/compiler/rustc_const_eval/messages.ftl
+++ b/compiler/rustc_const_eval/messages.ftl
@@ -402,9 +402,6 @@ const_eval_unallowed_mutable_refs =
 const_eval_unallowed_op_in_const_context =
     {$msg}
 
-const_eval_unavailable_target_features_for_fn =
-    calling a function that requires unavailable target features: {$unavailable_feats}
-
 const_eval_uninhabited_enum_variant_read =
     read discriminant of an uninhabited enum variant
 const_eval_uninhabited_enum_variant_written =
diff --git a/compiler/rustc_const_eval/src/interpret/call.rs b/compiler/rustc_const_eval/src/interpret/call.rs
index f99283c49f5..61e8007e10e 100644
--- a/compiler/rustc_const_eval/src/interpret/call.rs
+++ b/compiler/rustc_const_eval/src/interpret/call.rs
@@ -311,34 +311,6 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         Ok(())
     }
 
-    fn check_fn_target_features(&self, instance: ty::Instance<'tcx>) -> InterpResult<'tcx, ()> {
-        // Calling functions with `#[target_feature]` is not unsafe on WASM, see #84988
-        let attrs = self.tcx.codegen_fn_attrs(instance.def_id());
-        if !self.tcx.sess.target.is_like_wasm
-            && attrs
-                .target_features
-                .iter()
-                .any(|feature| !self.tcx.sess.target_features.contains(&feature.name))
-        {
-            throw_ub_custom!(
-                fluent::const_eval_unavailable_target_features_for_fn,
-                unavailable_feats = attrs
-                    .target_features
-                    .iter()
-                    .filter(|&feature| !feature.implied
-                        && !self.tcx.sess.target_features.contains(&feature.name))
-                    .fold(String::new(), |mut s, feature| {
-                        if !s.is_empty() {
-                            s.push_str(", ");
-                        }
-                        s.push_str(feature.name.as_str());
-                        s
-                    }),
-            );
-        }
-        Ok(())
-    }
-
     /// The main entry point for creating a new stack frame: performs ABI checks and initializes
     /// arguments.
     #[instrument(skip(self), level = "trace")]
@@ -360,20 +332,18 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
             throw_unsup_format!("calling a c-variadic function is not supported");
         }
 
-        if M::enforce_abi(self) {
-            if caller_fn_abi.conv != callee_fn_abi.conv {
-                throw_ub_custom!(
-                    fluent::const_eval_incompatible_calling_conventions,
-                    callee_conv = format!("{:?}", callee_fn_abi.conv),
-                    caller_conv = format!("{:?}", caller_fn_abi.conv),
-                )
-            }
+        if caller_fn_abi.conv != callee_fn_abi.conv {
+            throw_ub_custom!(
+                fluent::const_eval_incompatible_calling_conventions,
+                callee_conv = format!("{:?}", callee_fn_abi.conv),
+                caller_conv = format!("{:?}", caller_fn_abi.conv),
+            )
         }
 
         // Check that all target features required by the callee (i.e., from
         // the attribute `#[target_feature(enable = ...)]`) are enabled at
         // compile time.
-        self.check_fn_target_features(instance)?;
+        M::check_fn_target_features(self, instance)?;
 
         if !callee_fn_abi.can_unwind {
             // The callee cannot unwind, so force the `Unreachable` unwind handling.
diff --git a/compiler/rustc_const_eval/src/interpret/intrinsics.rs b/compiler/rustc_const_eval/src/interpret/intrinsics.rs
index aef39b9af2f..bedc56de0da 100644
--- a/compiler/rustc_const_eval/src/interpret/intrinsics.rs
+++ b/compiler/rustc_const_eval/src/interpret/intrinsics.rs
@@ -684,19 +684,19 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         assert!(layout.is_sized());
 
         let get_bytes = |this: &InterpCx<'tcx, M>,
-                         op: &OpTy<'tcx, <M as Machine<'tcx>>::Provenance>,
-                         size|
+                         op: &OpTy<'tcx, <M as Machine<'tcx>>::Provenance>|
          -> InterpResult<'tcx, &[u8]> {
             let ptr = this.read_pointer(op)?;
-            let Some(alloc_ref) = self.get_ptr_alloc(ptr, size)? else {
+            this.check_ptr_align(ptr, layout.align.abi)?;
+            let Some(alloc_ref) = self.get_ptr_alloc(ptr, layout.size)? else {
                 // zero-sized access
                 return Ok(&[]);
             };
             alloc_ref.get_bytes_strip_provenance()
         };
 
-        let lhs_bytes = get_bytes(self, lhs, layout.size)?;
-        let rhs_bytes = get_bytes(self, rhs, layout.size)?;
+        let lhs_bytes = get_bytes(self, lhs)?;
+        let rhs_bytes = get_bytes(self, rhs)?;
         Ok(Scalar::from_bool(lhs_bytes == rhs_bytes))
     }
 }
diff --git a/compiler/rustc_const_eval/src/interpret/machine.rs b/compiler/rustc_const_eval/src/interpret/machine.rs
index 761ab81e228..88453245b84 100644
--- a/compiler/rustc_const_eval/src/interpret/machine.rs
+++ b/compiler/rustc_const_eval/src/interpret/machine.rs
@@ -173,11 +173,6 @@ pub trait Machine<'tcx>: Sized {
         false
     }
 
-    /// Whether function calls should be [ABI](CallAbi)-checked.
-    fn enforce_abi(_ecx: &InterpCx<'tcx, Self>) -> bool {
-        true
-    }
-
     /// Whether Assert(OverflowNeg) and Assert(Overflow) MIR terminators should actually
     /// check for overflow.
     fn ignore_optional_overflow_checks(_ecx: &InterpCx<'tcx, Self>) -> bool;
@@ -238,6 +233,13 @@ pub trait Machine<'tcx>: Sized {
         unwind: mir::UnwindAction,
     ) -> InterpResult<'tcx, Option<ty::Instance<'tcx>>>;
 
+    /// Check whether the given function may be executed on the current machine, in terms of the
+    /// target features is requires.
+    fn check_fn_target_features(
+        _ecx: &InterpCx<'tcx, Self>,
+        _instance: ty::Instance<'tcx>,
+    ) -> InterpResult<'tcx>;
+
     /// Called to evaluate `Assert` MIR terminators that trigger a panic.
     fn assert_panic(
         ecx: &mut InterpCx<'tcx, Self>,
@@ -280,6 +282,9 @@ pub trait Machine<'tcx>: Sized {
         Ok(())
     }
 
+    /// Determines the result of a `NullaryOp::UbChecks` invocation.
+    fn ub_checks(_ecx: &InterpCx<'tcx, Self>) -> InterpResult<'tcx, bool>;
+
     /// Called when the interpreter encounters a `StatementKind::ConstEvalCounter` instruction.
     /// You can use this to detect long or endlessly running programs.
     #[inline]
@@ -615,6 +620,16 @@ pub macro compile_time_machine(<$tcx: lifetime>) {
     }
 
     #[inline(always)]
+    fn check_fn_target_features(
+        _ecx: &InterpCx<$tcx, Self>,
+        _instance: ty::Instance<$tcx>,
+    ) -> InterpResult<$tcx> {
+        // For now we don't do any checking here. We can't use `tcx.sess` because that can differ
+        // between crates, and we need to ensure that const-eval always behaves the same.
+        Ok(())
+    }
+
+    #[inline(always)]
     fn call_extra_fn(
         _ecx: &mut InterpCx<$tcx, Self>,
         fn_val: !,
@@ -628,6 +643,13 @@ pub macro compile_time_machine(<$tcx: lifetime>) {
     }
 
     #[inline(always)]
+    fn ub_checks(_ecx: &InterpCx<$tcx, Self>) -> InterpResult<$tcx, bool> {
+        // We can't look at `tcx.sess` here as that can differ across crates, which can lead to
+        // unsound differences in evaluating the same constant at different instantiation sites.
+        Ok(true)
+    }
+
+    #[inline(always)]
     fn adjust_global_allocation<'b>(
         _ecx: &InterpCx<$tcx, Self>,
         _id: AllocId,
diff --git a/compiler/rustc_const_eval/src/interpret/operator.rs b/compiler/rustc_const_eval/src/interpret/operator.rs
index 2f860f9f942..e9ba12dbcc4 100644
--- a/compiler/rustc_const_eval/src/interpret/operator.rs
+++ b/compiler/rustc_const_eval/src/interpret/operator.rs
@@ -512,7 +512,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                     self.tcx.offset_of_subfield(self.param_env, layout, fields.iter()).bytes();
                 ImmTy::from_uint(val, usize_layout())
             }
-            UbChecks => ImmTy::from_bool(self.tcx.sess.ub_checks(), *self.tcx),
+            UbChecks => ImmTy::from_bool(M::ub_checks(self)?, *self.tcx),
         })
     }
 }
diff --git a/compiler/rustc_driver_impl/src/lib.rs b/compiler/rustc_driver_impl/src/lib.rs
index 820ba96b100..e49ae60e890 100644
--- a/compiler/rustc_driver_impl/src/lib.rs
+++ b/compiler/rustc_driver_impl/src/lib.rs
@@ -393,13 +393,17 @@ fn run_compiler(
 
         let linker = compiler.enter(|queries| {
             let early_exit = || early_exit().map(|_| None);
+
+            // Parse the crate root source code (doesn't parse submodules yet)
+            // Everything else is parsed during macro expansion.
             queries.parse()?;
 
-            if let Some(ppm) = &sess.opts.pretty {
-                if ppm.needs_ast_map() {
+            // If pretty printing is requested: Figure out the representation, print it and exit
+            if let Some(pp_mode) = sess.opts.pretty {
+                if pp_mode.needs_ast_map() {
                     queries.global_ctxt()?.enter(|tcx| {
                         tcx.ensure().early_lint_checks(());
-                        pretty::print(sess, *ppm, pretty::PrintExtra::NeedsAstMap { tcx });
+                        pretty::print(sess, pp_mode, pretty::PrintExtra::NeedsAstMap { tcx });
                         Ok(())
                     })?;
 
@@ -410,7 +414,7 @@ fn run_compiler(
                     let krate = queries.parse()?;
                     pretty::print(
                         sess,
-                        *ppm,
+                        pp_mode,
                         pretty::PrintExtra::AfterParsing { krate: &*krate.borrow() },
                     );
                 }
@@ -465,12 +469,8 @@ fn run_compiler(
             linker.link(sess, codegen_backend)?
         }
 
-        if sess.opts.unstable_opts.print_fuel.is_some() {
-            eprintln!(
-                "Fuel used by {}: {}",
-                sess.opts.unstable_opts.print_fuel.as_ref().unwrap(),
-                sess.print_fuel.load(Ordering::SeqCst)
-            );
+        if let Some(fuel) = sess.opts.unstable_opts.print_fuel.as_deref() {
+            eprintln!("Fuel used by {}: {}", fuel, sess.print_fuel.load(Ordering::SeqCst));
         }
 
         Ok(())
@@ -487,36 +487,43 @@ fn make_output(matches: &getopts::Matches) -> (Option<PathBuf>, Option<OutFileNa
     (odir, ofile)
 }
 
-// Extract input (string or file and optional path) from matches.
+/// Extract input (string or file and optional path) from matches.
+/// This handles reading from stdin if `-` is provided.
 fn make_input(
     early_dcx: &EarlyDiagCtxt,
     free_matches: &[String],
 ) -> Result<Option<Input>, ErrorGuaranteed> {
-    let [ifile] = free_matches else { return Ok(None) };
-    if ifile == "-" {
-        let mut src = String::new();
-        if io::stdin().read_to_string(&mut src).is_err() {
-            // Immediately stop compilation if there was an issue reading
-            // the input (for example if the input stream is not UTF-8).
-            let reported =
-                early_dcx.early_err("couldn't read from stdin, as it did not contain valid UTF-8");
-            return Err(reported);
-        }
-        if let Ok(path) = env::var("UNSTABLE_RUSTDOC_TEST_PATH") {
+    let [input_file] = free_matches else { return Ok(None) };
+
+    if input_file != "-" {
+        // Normal `Input::File`
+        return Ok(Some(Input::File(PathBuf::from(input_file))));
+    }
+
+    // read from stdin as `Input::Str`
+    let mut input = String::new();
+    if io::stdin().read_to_string(&mut input).is_err() {
+        // Immediately stop compilation if there was an issue reading
+        // the input (for example if the input stream is not UTF-8).
+        let reported =
+            early_dcx.early_err("couldn't read from stdin, as it did not contain valid UTF-8");
+        return Err(reported);
+    }
+
+    let name = match env::var("UNSTABLE_RUSTDOC_TEST_PATH") {
+        Ok(path) => {
             let line = env::var("UNSTABLE_RUSTDOC_TEST_LINE").expect(
                 "when UNSTABLE_RUSTDOC_TEST_PATH is set \
                                     UNSTABLE_RUSTDOC_TEST_LINE also needs to be set",
             );
             let line = isize::from_str_radix(&line, 10)
                 .expect("UNSTABLE_RUSTDOC_TEST_LINE needs to be an number");
-            let file_name = FileName::doc_test_source_code(PathBuf::from(path), line);
-            Ok(Some(Input::Str { name: file_name, input: src }))
-        } else {
-            Ok(Some(Input::Str { name: FileName::anon_source_code(&src), input: src }))
+            FileName::doc_test_source_code(PathBuf::from(path), line)
         }
-    } else {
-        Ok(Some(Input::File(PathBuf::from(ifile))))
-    }
+        Err(_) => FileName::anon_source_code(&input),
+    };
+
+    Ok(Some(Input::Str { name, input }))
 }
 
 /// Whether to stop or continue compilation.
diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs
index 4524458023d..279d02e8777 100644
--- a/compiler/rustc_feature/src/unstable.rs
+++ b/compiler/rustc_feature/src/unstable.rs
@@ -594,6 +594,8 @@ declare_features! (
     (unstable, strict_provenance, "1.61.0", Some(95228)),
     /// Allows string patterns to dereference values to match them.
     (unstable, string_deref_patterns, "1.67.0", Some(87121)),
+    /// Allows structs to carry target_feature information.
+    (incomplete, struct_target_features, "CURRENT_RUSTC_VERSION", Some(129107)),
     /// Allows the use of `#[target_feature]` on safe functions.
     (unstable, target_feature_11, "1.45.0", Some(69098)),
     /// Allows using `#[thread_local]` on `static` items.
diff --git a/compiler/rustc_hir/src/def.rs b/compiler/rustc_hir/src/def.rs
index b329432d1e1..36e29d2dcb2 100644
--- a/compiler/rustc_hir/src/def.rs
+++ b/compiler/rustc_hir/src/def.rs
@@ -326,6 +326,41 @@ impl DefKind {
             | DefKind::ExternCrate => false,
         }
     }
+
+    /// Whether `query struct_target_features` should be used with this definition.
+    pub fn has_struct_target_features(self) -> bool {
+        match self {
+            DefKind::Struct | DefKind::Union | DefKind::Enum => true,
+            DefKind::Fn
+            | DefKind::AssocFn
+            | DefKind::Ctor(..)
+            | DefKind::Closure
+            | DefKind::Static { .. }
+            | DefKind::Mod
+            | DefKind::Variant
+            | DefKind::Trait
+            | DefKind::TyAlias
+            | DefKind::ForeignTy
+            | DefKind::TraitAlias
+            | DefKind::AssocTy
+            | DefKind::Const
+            | DefKind::AssocConst
+            | DefKind::Macro(..)
+            | DefKind::Use
+            | DefKind::ForeignMod
+            | DefKind::OpaqueTy
+            | DefKind::Impl { .. }
+            | DefKind::Field
+            | DefKind::TyParam
+            | DefKind::ConstParam
+            | DefKind::LifetimeParam
+            | DefKind::AnonConst
+            | DefKind::InlineConst
+            | DefKind::SyntheticCoroutineBody
+            | DefKind::GlobalAsm
+            | DefKind::ExternCrate => false,
+        }
+    }
 }
 
 /// The resolution of a path or export.
diff --git a/compiler/rustc_hir_analysis/src/collect.rs b/compiler/rustc_hir_analysis/src/collect.rs
index 9e6c431a6e6..3acf2c63145 100644
--- a/compiler/rustc_hir_analysis/src/collect.rs
+++ b/compiler/rustc_hir_analysis/src/collect.rs
@@ -34,7 +34,7 @@ use rustc_infer::traits::ObligationCause;
 use rustc_middle::hir::nested_filter;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::util::{Discr, IntTypeExt};
-use rustc_middle::ty::{self, AdtKind, Const, IsSuggestable, Ty, TyCtxt, Upcast};
+use rustc_middle::ty::{self, AdtKind, Const, IsSuggestable, Ty, TyCtxt};
 use rustc_middle::{bug, span_bug};
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{Span, DUMMY_SP};
@@ -70,7 +70,6 @@ pub fn provide(providers: &mut Providers) {
         impl_super_outlives: item_bounds::impl_super_outlives,
         generics_of: generics_of::generics_of,
         predicates_of: predicates_of::predicates_of,
-        predicates_defined_on,
         explicit_predicates_of: predicates_of::explicit_predicates_of,
         explicit_super_predicates_of: predicates_of::explicit_super_predicates_of,
         explicit_implied_predicates_of: predicates_of::explicit_implied_predicates_of,
@@ -1775,34 +1774,6 @@ fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
     })
 }
 
-/// Returns a list of type predicates for the definition with ID `def_id`, including inferred
-/// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
-/// inferred constraints concerning which regions outlive other regions.
-#[instrument(level = "debug", skip(tcx))]
-fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
-    let mut result = tcx.explicit_predicates_of(def_id);
-    debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result);
-    let inferred_outlives = tcx.inferred_outlives_of(def_id);
-    if !inferred_outlives.is_empty() {
-        debug!(
-            "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
-            def_id, inferred_outlives,
-        );
-        let inferred_outlives_iter =
-            inferred_outlives.iter().map(|(clause, span)| ((*clause).upcast(tcx), *span));
-        if result.predicates.is_empty() {
-            result.predicates = tcx.arena.alloc_from_iter(inferred_outlives_iter);
-        } else {
-            result.predicates = tcx.arena.alloc_from_iter(
-                result.predicates.into_iter().copied().chain(inferred_outlives_iter),
-            );
-        }
-    }
-
-    debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
-    result
-}
-
 fn compute_sig_of_foreign_fn_decl<'tcx>(
     tcx: TyCtxt<'tcx>,
     def_id: LocalDefId,
diff --git a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
index 6ac4802b195..bba8b0497be 100644
--- a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
@@ -18,10 +18,26 @@ use crate::delegation::inherit_predicates_for_delegation_item;
 use crate::hir_ty_lowering::{HirTyLowerer, OnlySelfBounds, 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 `predicates_defined_on`, plus
-/// `Self: Trait` predicates for traits.
+/// ID `def_id`. This includes all predicates returned by `explicit_predicates_of`, plus
+/// inferred constraints concerning which regions outlive other regions.
+#[instrument(level = "debug", skip(tcx))]
 pub(super) fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
-    let mut result = tcx.predicates_defined_on(def_id);
+    let mut result = tcx.explicit_predicates_of(def_id);
+    debug!("predicates_of: explicit_predicates_of({:?}) = {:?}", def_id, result);
+
+    let inferred_outlives = tcx.inferred_outlives_of(def_id);
+    if !inferred_outlives.is_empty() {
+        debug!("predicates_of: inferred_outlives_of({:?}) = {:?}", def_id, inferred_outlives,);
+        let inferred_outlives_iter =
+            inferred_outlives.iter().map(|(clause, span)| ((*clause).upcast(tcx), *span));
+        if result.predicates.is_empty() {
+            result.predicates = tcx.arena.alloc_from_iter(inferred_outlives_iter);
+        } else {
+            result.predicates = tcx.arena.alloc_from_iter(
+                result.predicates.into_iter().copied().chain(inferred_outlives_iter),
+            );
+        }
+    }
 
     if tcx.is_trait(def_id) {
         // For traits, add `Self: Trait` predicate. This is
@@ -51,7 +67,8 @@ pub(super) fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredic
                 .chain(std::iter::once((ty::TraitRef::identity(tcx, def_id).upcast(tcx), span))),
         );
     }
-    debug!("predicates_of(def_id={:?}) = {:?}", def_id, result);
+
+    debug!("predicates_of({:?}) = {:?}", def_id, result);
     result
 }
 
diff --git a/compiler/rustc_hir_typeck/src/coercion.rs b/compiler/rustc_hir_typeck/src/coercion.rs
index dabc5a89397..54ddff98869 100644
--- a/compiler/rustc_hir_typeck/src/coercion.rs
+++ b/compiler/rustc_hir_typeck/src/coercion.rs
@@ -850,6 +850,8 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
                     }
 
                     // Safe `#[target_feature]` functions are not assignable to safe fn pointers (RFC 2396).
+                    // FIXME(struct_target_features): should this be true also for functions that inherit
+                    // target features from structs?
 
                     if b_hdr.safety == hir::Safety::Safe
                         && !self.tcx.codegen_fn_attrs(def_id).target_features.is_empty()
diff --git a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
index 46039f6e5f6..27625f79108 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
@@ -224,6 +224,7 @@ provide! { tcx, def_id, other, cdata,
     variances_of => { table }
     fn_sig => { table }
     codegen_fn_attrs => { table }
+    struct_target_features => { table }
     impl_trait_header => { table }
     const_param_default => { table }
     object_lifetime_default => { table }
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index 9c93726ca37..fbcfbd3befa 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -1392,6 +1392,9 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             if def_kind.has_codegen_attrs() {
                 record!(self.tables.codegen_fn_attrs[def_id] <- self.tcx.codegen_fn_attrs(def_id));
             }
+            if def_kind.has_struct_target_features() {
+                record_array!(self.tables.struct_target_features[def_id] <- self.tcx.struct_target_features(def_id));
+            }
             if should_encode_visibility(def_kind) {
                 let vis =
                     self.tcx.local_visibility(local_id).map_id(|def_id| def_id.local_def_index);
diff --git a/compiler/rustc_metadata/src/rmeta/mod.rs b/compiler/rustc_metadata/src/rmeta/mod.rs
index c1b77172983..aec728d4262 100644
--- a/compiler/rustc_metadata/src/rmeta/mod.rs
+++ b/compiler/rustc_metadata/src/rmeta/mod.rs
@@ -19,7 +19,7 @@ use rustc_macros::{
     Decodable, Encodable, MetadataDecodable, MetadataEncodable, TyDecodable, TyEncodable,
 };
 use rustc_middle::metadata::ModChild;
-use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrs;
+use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrs, TargetFeature};
 use rustc_middle::middle::debugger_visualizer::DebuggerVisualizerFile;
 use rustc_middle::middle::exported_symbols::{ExportedSymbol, SymbolExportInfo};
 use rustc_middle::middle::lib_features::FeatureStability;
@@ -427,6 +427,7 @@ define_tables! {
     variances_of: Table<DefIndex, LazyArray<ty::Variance>>,
     fn_sig: Table<DefIndex, LazyValue<ty::EarlyBinder<'static, ty::PolyFnSig<'static>>>>,
     codegen_fn_attrs: Table<DefIndex, LazyValue<CodegenFnAttrs>>,
+    struct_target_features: Table<DefIndex, LazyArray<TargetFeature>>,
     impl_trait_header: Table<DefIndex, LazyValue<ty::ImplTraitHeader<'static>>>,
     const_param_default: Table<DefIndex, LazyValue<ty::EarlyBinder<'static, rustc_middle::ty::Const<'static>>>>,
     object_lifetime_default: Table<DefIndex, LazyValue<ObjectLifetimeDefault>>,
diff --git a/compiler/rustc_middle/src/arena.rs b/compiler/rustc_middle/src/arena.rs
index 37c10b14054..7050a06b8dc 100644
--- a/compiler/rustc_middle/src/arena.rs
+++ b/compiler/rustc_middle/src/arena.rs
@@ -35,7 +35,6 @@ macro_rules! arena_types {
             )>,
             [] crate_for_resolver: rustc_data_structures::steal::Steal<(rustc_ast::Crate, rustc_ast::AttrVec)>,
             [] resolutions: rustc_middle::ty::ResolverGlobalCtxt,
-            [decode] code_region: rustc_middle::mir::coverage::CodeRegion,
             [] const_allocs: rustc_middle::mir::interpret::Allocation,
             [] region_scope_tree: rustc_middle::middle::region::ScopeTree,
             // Required for the incremental on-disk cache
diff --git a/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs b/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
index b7d290e58d2..c098a739592 100644
--- a/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
+++ b/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
@@ -26,8 +26,8 @@ pub struct CodegenFnAttrs {
     /// be set when `link_name` is set. This is for foreign items with the
     /// "raw-dylib" kind.
     pub link_ordinal: Option<u16>,
-    /// The `#[target_feature(enable = "...")]` attribute and the enabled
-    /// features (only enabled features are supported right now).
+    /// All the target features that are enabled for this function. Some features might be enabled
+    /// implicitly.
     pub target_features: Vec<TargetFeature>,
     /// The `#[linkage = "..."]` attribute on Rust-defined items and the value we found.
     pub linkage: Option<Linkage>,
@@ -55,8 +55,8 @@ pub struct CodegenFnAttrs {
 pub struct TargetFeature {
     /// The name of the target feature (e.g. "avx")
     pub name: Symbol,
-    /// The feature is implied by another feature, rather than explicitly added by the
-    /// `#[target_feature]` attribute
+    /// The feature is implied by another feature or by an argument, rather than explicitly
+    /// added by the `#[target_feature]` attribute
     pub implied: bool,
 }
 
diff --git a/compiler/rustc_middle/src/mir/coverage.rs b/compiler/rustc_middle/src/mir/coverage.rs
index b11c523cfe9..bfe2a2c2cb3 100644
--- a/compiler/rustc_middle/src/mir/coverage.rs
+++ b/compiler/rustc_middle/src/mir/coverage.rs
@@ -163,7 +163,7 @@ impl Debug for CoverageKind {
 
 #[derive(Clone, TyEncodable, TyDecodable, Hash, HashStable, PartialEq, Eq, PartialOrd, Ord)]
 #[derive(TypeFoldable, TypeVisitable)]
-pub struct CodeRegion {
+pub struct SourceRegion {
     pub file_name: Symbol,
     pub start_line: u32,
     pub start_col: u32,
@@ -171,7 +171,7 @@ pub struct CodeRegion {
     pub end_col: u32,
 }
 
-impl Debug for CodeRegion {
+impl Debug for SourceRegion {
     fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
         write!(
             fmt,
@@ -242,7 +242,7 @@ impl MappingKind {
 #[derive(TyEncodable, TyDecodable, Hash, HashStable, TypeFoldable, TypeVisitable)]
 pub struct Mapping {
     pub kind: MappingKind,
-    pub code_region: CodeRegion,
+    pub source_region: SourceRegion,
 }
 
 /// Stores per-function coverage information attached to a `mir::Body`,
diff --git a/compiler/rustc_middle/src/mir/pretty.rs b/compiler/rustc_middle/src/mir/pretty.rs
index efdc0c710ba..6785805c27d 100644
--- a/compiler/rustc_middle/src/mir/pretty.rs
+++ b/compiler/rustc_middle/src/mir/pretty.rs
@@ -547,8 +547,8 @@ fn write_function_coverage_info(
     for (id, expression) in expressions.iter_enumerated() {
         writeln!(w, "{INDENT}coverage {id:?} => {expression:?};")?;
     }
-    for coverage::Mapping { kind, code_region } in mappings {
-        writeln!(w, "{INDENT}coverage {kind:?} => {code_region:?};")?;
+    for coverage::Mapping { kind, source_region } in mappings {
+        writeln!(w, "{INDENT}coverage {kind:?} => {source_region:?};")?;
     }
     writeln!(w)?;
 
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index b748f85253f..6434bd0d7bf 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -47,7 +47,7 @@ use {rustc_ast as ast, rustc_attr as attr, rustc_hir as hir};
 use crate::infer::canonical::{self, Canonical};
 use crate::lint::LintExpectation;
 use crate::metadata::ModChild;
-use crate::middle::codegen_fn_attrs::CodegenFnAttrs;
+use crate::middle::codegen_fn_attrs::{CodegenFnAttrs, TargetFeature};
 use crate::middle::debugger_visualizer::DebuggerVisualizerFile;
 use crate::middle::exported_symbols::{ExportedSymbol, SymbolExportInfo};
 use crate::middle::lib_features::LibFeatures;
@@ -312,17 +312,6 @@ rustc_queries! {
     /// predicates (where-clauses) that must be proven true in order
     /// to reference it. This is almost always the "predicates query"
     /// that you want.
-    ///
-    /// `predicates_of` builds on `predicates_defined_on` -- in fact,
-    /// it is almost always the same as that query, except for the
-    /// case of traits. For traits, `predicates_of` contains
-    /// an additional `Self: Trait<...>` predicate that users don't
-    /// actually write. This reflects the fact that to invoke the
-    /// trait (e.g., via `Default::default`) you must supply types
-    /// that actually implement the trait. (However, this extra
-    /// predicate gets in the way of some checks, which are intended
-    /// to operate over only the actual where-clauses written by the
-    /// user.)
     query predicates_of(key: DefId) -> ty::GenericPredicates<'tcx> {
         desc { |tcx| "computing predicates of `{}`", tcx.def_path_str(key) }
         cache_on_disk_if { key.is_local() }
@@ -619,14 +608,6 @@ rustc_queries! {
         desc { "getting wasm import module map" }
     }
 
-    /// Maps from the `DefId` of an item (trait/struct/enum/fn) to the
-    /// predicates (where-clauses) directly defined on it. This is
-    /// equal to the `explicit_predicates_of` predicates plus the
-    /// `inferred_outlives_of` predicates.
-    query predicates_defined_on(key: DefId) -> ty::GenericPredicates<'tcx> {
-        desc { |tcx| "computing predicates of `{}`", tcx.def_path_str(key) }
-    }
-
     /// Returns everything that looks like a predicate written explicitly
     /// by the user on a trait item.
     ///
@@ -1264,6 +1245,11 @@ rustc_queries! {
         feedable
     }
 
+    query struct_target_features(def_id: DefId) -> &'tcx [TargetFeature] {
+        separate_provide_extern
+        desc { |tcx| "computing target features for struct `{}`", tcx.def_path_str(def_id) }
+    }
+
     query asm_target_features(def_id: DefId) -> &'tcx FxIndexSet<Symbol> {
         desc { |tcx| "computing target features for inline asm of `{}`", tcx.def_path_str(def_id) }
     }
diff --git a/compiler/rustc_middle/src/ty/codec.rs b/compiler/rustc_middle/src/ty/codec.rs
index 401f6da6526..46203ee150f 100644
--- a/compiler/rustc_middle/src/ty/codec.rs
+++ b/compiler/rustc_middle/src/ty/codec.rs
@@ -462,7 +462,6 @@ impl_decodable_via_ref! {
     &'tcx traits::ImplSource<'tcx, ()>,
     &'tcx mir::Body<'tcx>,
     &'tcx mir::BorrowCheckResult<'tcx>,
-    &'tcx mir::coverage::CodeRegion,
     &'tcx ty::List<ty::BoundVariableKind>,
     &'tcx ty::ListWithCachedTypeInfo<ty::Clause<'tcx>>,
     &'tcx ty::List<FieldIdx>,
diff --git a/compiler/rustc_middle/src/ty/parameterized.rs b/compiler/rustc_middle/src/ty/parameterized.rs
index 7e1255f606c..be611e19b49 100644
--- a/compiler/rustc_middle/src/ty/parameterized.rs
+++ b/compiler/rustc_middle/src/ty/parameterized.rs
@@ -59,6 +59,7 @@ trivially_parameterized_over_tcx! {
     std::string::String,
     crate::metadata::ModChild,
     crate::middle::codegen_fn_attrs::CodegenFnAttrs,
+    crate::middle::codegen_fn_attrs::TargetFeature,
     crate::middle::debugger_visualizer::DebuggerVisualizerFile,
     crate::middle::exported_symbols::SymbolExportInfo,
     crate::middle::lib_features::FeatureStability,
diff --git a/compiler/rustc_mir_build/messages.ftl b/compiler/rustc_mir_build/messages.ftl
index 7a10e627ccd..a42e8ff0168 100644
--- a/compiler/rustc_mir_build/messages.ftl
+++ b/compiler/rustc_mir_build/messages.ftl
@@ -125,6 +125,17 @@ mir_build_initializing_type_with_requires_unsafe_unsafe_op_in_unsafe_fn_allowed
     .note = initializing a layout restricted type's field with a value outside the valid range is undefined behavior
     .label = initializing type with `rustc_layout_scalar_valid_range` attr
 
+mir_build_initializing_type_with_target_feature_requires_unsafe =
+    initializing type with `target_feature` attr is unsafe and requires unsafe block
+    .note = this struct can only be constructed if the corresponding `target_feature`s are available
+    .label = initializing type with `target_feature` attr
+
+mir_build_initializing_type_with_target_feature_requires_unsafe_unsafe_op_in_unsafe_fn_allowed =
+    initializing type with `target_feature` attr is unsafe and requires unsafe function or block
+    .note = this struct can only be constructed if the corresponding `target_feature`s are available
+    .label = initializing type with `target_feature` attr
+
+
 mir_build_inline_assembly_requires_unsafe =
     use of inline assembly is unsafe and requires unsafe block
     .note = inline assembly is entirely unchecked and can cause undefined behavior
@@ -387,6 +398,11 @@ mir_build_unsafe_op_in_unsafe_fn_initializing_type_with_requires_unsafe =
     .note = initializing a layout restricted type's field with a value outside the valid range is undefined behavior
     .label = initializing type with `rustc_layout_scalar_valid_range` attr
 
+mir_build_unsafe_op_in_unsafe_fn_initializing_type_with_target_feature_requires_unsafe =
+    initializing type with `target_feature` attr is unsafe and requires unsafe block
+    .note = this struct can only be constructed if the corresponding `target_feature`s are available
+    .label = initializing type with `target_feature` attr
+
 mir_build_unsafe_op_in_unsafe_fn_inline_assembly_requires_unsafe =
     use of inline assembly is unsafe and requires unsafe block
     .note = inline assembly is entirely unchecked and can cause undefined behavior
diff --git a/compiler/rustc_mir_build/src/check_unsafety.rs b/compiler/rustc_mir_build/src/check_unsafety.rs
index b6cf7a40ecd..60cd49b88b4 100644
--- a/compiler/rustc_mir_build/src/check_unsafety.rs
+++ b/compiler/rustc_mir_build/src/check_unsafety.rs
@@ -461,14 +461,18 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
                     };
                     self.requires_unsafe(expr.span, CallToUnsafeFunction(func_id));
                 } else if let &ty::FnDef(func_did, _) = self.thir[fun].ty.kind() {
-                    // If the called function has target features the calling function hasn't,
+                    // If the called function has explicit target features the calling function hasn't,
                     // the call requires `unsafe`. Don't check this on wasm
                     // targets, though. For more information on wasm see the
                     // is_like_wasm check in hir_analysis/src/collect.rs
+                    // Implicit target features are OK because they are either a consequence of some
+                    // explicit target feature (which is checked to be present in the caller) or
+                    // come from a witness argument.
                     let callee_features = &self.tcx.codegen_fn_attrs(func_did).target_features;
                     if !self.tcx.sess.target.options.is_like_wasm
                         && !callee_features.iter().all(|feature| {
-                            self.body_target_features.iter().any(|f| f.name == feature.name)
+                            feature.implied
+                                || self.body_target_features.iter().any(|f| f.name == feature.name)
                         })
                     {
                         let missing: Vec<_> = callee_features
@@ -542,10 +546,16 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
                 user_ty: _,
                 fields: _,
                 base: _,
-            }) => match self.tcx.layout_scalar_valid_range(adt_def.did()) {
-                (Bound::Unbounded, Bound::Unbounded) => {}
-                _ => self.requires_unsafe(expr.span, InitializingTypeWith),
-            },
+            }) => {
+                match self.tcx.layout_scalar_valid_range(adt_def.did()) {
+                    (Bound::Unbounded, Bound::Unbounded) => {}
+                    _ => self.requires_unsafe(expr.span, InitializingTypeWith),
+                }
+                if !self.tcx.struct_target_features(adt_def.did()).is_empty() {
+                    self.requires_unsafe(expr.span, ConstructingTargetFeaturesType)
+                }
+            }
+
             ExprKind::Closure(box ClosureExpr {
                 closure_id,
                 args: _,
@@ -647,6 +657,7 @@ enum UnsafeOpKind {
     CallToUnsafeFunction(Option<DefId>),
     UseOfInlineAssembly,
     InitializingTypeWith,
+    ConstructingTargetFeaturesType,
     UseOfMutableStatic,
     UseOfExternStatic,
     DerefOfRawPointer,
@@ -728,6 +739,15 @@ impl UnsafeOpKind {
                     unsafe_not_inherited_note,
                 },
             ),
+            ConstructingTargetFeaturesType => tcx.emit_node_span_lint(
+                UNSAFE_OP_IN_UNSAFE_FN,
+                hir_id,
+                span,
+                UnsafeOpInUnsafeFnInitializingTypeWithTargetFeatureRequiresUnsafe {
+                    span,
+                    unsafe_not_inherited_note,
+                },
+            ),
             UseOfMutableStatic => tcx.emit_node_span_lint(
                 UNSAFE_OP_IN_UNSAFE_FN,
                 hir_id,
@@ -885,6 +905,20 @@ impl UnsafeOpKind {
                     unsafe_not_inherited_note,
                 });
             }
+            ConstructingTargetFeaturesType if unsafe_op_in_unsafe_fn_allowed => {
+                dcx.emit_err(
+                    InitializingTypeWithTargetFeatureRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
+                        span,
+                        unsafe_not_inherited_note,
+                    },
+                );
+            }
+            ConstructingTargetFeaturesType => {
+                dcx.emit_err(InitializingTypeWithTargetFeatureRequiresUnsafe {
+                    span,
+                    unsafe_not_inherited_note,
+                });
+            }
             UseOfMutableStatic if unsafe_op_in_unsafe_fn_allowed => {
                 dcx.emit_err(UseOfMutableStaticRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
                     span,
diff --git a/compiler/rustc_mir_build/src/errors.rs b/compiler/rustc_mir_build/src/errors.rs
index 7f9eefd1d52..e7d6239aa9b 100644
--- a/compiler/rustc_mir_build/src/errors.rs
+++ b/compiler/rustc_mir_build/src/errors.rs
@@ -87,6 +87,16 @@ pub(crate) struct UnsafeOpInUnsafeFnInitializingTypeWithRequiresUnsafe {
 }
 
 #[derive(LintDiagnostic)]
+#[diag(mir_build_unsafe_op_in_unsafe_fn_initializing_type_with_target_feature_requires_unsafe, code = E0133)]
+#[note]
+pub(crate) struct UnsafeOpInUnsafeFnInitializingTypeWithTargetFeatureRequiresUnsafe {
+    #[label]
+    pub(crate) span: Span,
+    #[subdiagnostic]
+    pub(crate) unsafe_not_inherited_note: Option<UnsafeNotInheritedLintNote>,
+}
+
+#[derive(LintDiagnostic)]
 #[diag(mir_build_unsafe_op_in_unsafe_fn_mutable_static_requires_unsafe, code = E0133)]
 #[note]
 pub(crate) struct UnsafeOpInUnsafeFnUseOfMutableStaticRequiresUnsafe {
@@ -251,6 +261,17 @@ pub(crate) struct InitializingTypeWithRequiresUnsafe {
 }
 
 #[derive(Diagnostic)]
+#[diag(mir_build_initializing_type_with_target_feature_requires_unsafe, code = E0133)]
+#[note]
+pub(crate) struct InitializingTypeWithTargetFeatureRequiresUnsafe {
+    #[primary_span]
+    #[label]
+    pub(crate) span: Span,
+    #[subdiagnostic]
+    pub(crate) unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
+}
+
+#[derive(Diagnostic)]
 #[diag(
     mir_build_initializing_type_with_requires_unsafe_unsafe_op_in_unsafe_fn_allowed,
     code = E0133
@@ -265,6 +286,20 @@ pub(crate) struct InitializingTypeWithRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
 }
 
 #[derive(Diagnostic)]
+#[diag(
+    mir_build_initializing_type_with_target_feature_requires_unsafe_unsafe_op_in_unsafe_fn_allowed,
+    code = E0133
+)]
+#[note]
+pub(crate) struct InitializingTypeWithTargetFeatureRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
+    #[primary_span]
+    #[label]
+    pub(crate) span: Span,
+    #[subdiagnostic]
+    pub(crate) unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
+}
+
+#[derive(Diagnostic)]
 #[diag(mir_build_mutable_static_requires_unsafe, code = E0133)]
 #[note]
 pub(crate) struct UseOfMutableStaticRequiresUnsafe {
diff --git a/compiler/rustc_mir_transform/src/coverage/mod.rs b/compiler/rustc_mir_transform/src/coverage/mod.rs
index 96ca3b43d5c..af0f1e38a75 100644
--- a/compiler/rustc_mir_transform/src/coverage/mod.rs
+++ b/compiler/rustc_mir_transform/src/coverage/mod.rs
@@ -13,7 +13,7 @@ use rustc_hir::intravisit::{walk_expr, Visitor};
 use rustc_middle::hir::map::Map;
 use rustc_middle::hir::nested_filter;
 use rustc_middle::mir::coverage::{
-    CodeRegion, CoverageKind, DecisionInfo, FunctionCoverageInfo, Mapping, MappingKind,
+    CoverageKind, DecisionInfo, FunctionCoverageInfo, Mapping, MappingKind, SourceRegion,
 };
 use rustc_middle::mir::{
     self, BasicBlock, BasicBlockData, SourceInfo, Statement, StatementKind, Terminator,
@@ -159,7 +159,7 @@ fn create_mappings<'tcx>(
             .expect("all BCBs with spans were given counters")
             .as_term()
     };
-    let region_for_span = |span: Span| make_code_region(source_map, file_name, span, body_span);
+    let region_for_span = |span: Span| make_source_region(source_map, file_name, span, body_span);
 
     // Fully destructure the mappings struct to make sure we don't miss any kinds.
     let ExtractedMappings {
@@ -175,9 +175,9 @@ fn create_mappings<'tcx>(
     mappings.extend(code_mappings.iter().filter_map(
         // Ordinary code mappings are the simplest kind.
         |&mappings::CodeMapping { span, bcb }| {
-            let code_region = region_for_span(span)?;
+            let source_region = region_for_span(span)?;
             let kind = MappingKind::Code(term_for_bcb(bcb));
-            Some(Mapping { kind, code_region })
+            Some(Mapping { kind, source_region })
         },
     ));
 
@@ -186,29 +186,29 @@ fn create_mappings<'tcx>(
             let true_term = term_for_bcb(true_bcb);
             let false_term = term_for_bcb(false_bcb);
             let kind = MappingKind::Branch { true_term, false_term };
-            let code_region = region_for_span(span)?;
-            Some(Mapping { kind, code_region })
+            let source_region = region_for_span(span)?;
+            Some(Mapping { kind, source_region })
         },
     ));
 
     mappings.extend(mcdc_branches.iter().filter_map(
         |&mappings::MCDCBranch { span, true_bcb, false_bcb, condition_info, decision_depth: _ }| {
-            let code_region = region_for_span(span)?;
+            let source_region = region_for_span(span)?;
             let true_term = term_for_bcb(true_bcb);
             let false_term = term_for_bcb(false_bcb);
             let kind = match condition_info {
                 Some(mcdc_params) => MappingKind::MCDCBranch { true_term, false_term, mcdc_params },
                 None => MappingKind::Branch { true_term, false_term },
             };
-            Some(Mapping { kind, code_region })
+            Some(Mapping { kind, source_region })
         },
     ));
 
     mappings.extend(mcdc_decisions.iter().filter_map(
         |&mappings::MCDCDecision { span, bitmap_idx, num_conditions, .. }| {
-            let code_region = region_for_span(span)?;
+            let source_region = region_for_span(span)?;
             let kind = MappingKind::MCDCDecision(DecisionInfo { bitmap_idx, num_conditions });
-            Some(Mapping { kind, code_region })
+            Some(Mapping { kind, source_region })
         },
     ));
 
@@ -362,19 +362,13 @@ fn inject_statement(mir_body: &mut mir::Body<'_>, counter_kind: CoverageKind, bb
 /// but it's hard to rule out entirely (especially in the presence of complex macros
 /// or other expansions), and if it does happen then skipping a span or function is
 /// better than an ICE or `llvm-cov` failure that the user might have no way to avoid.
-fn make_code_region(
+#[instrument(level = "debug", skip(source_map))]
+fn make_source_region(
     source_map: &SourceMap,
     file_name: Symbol,
     span: Span,
     body_span: Span,
-) -> Option<CodeRegion> {
-    debug!(
-        "Called make_code_region(file_name={}, span={}, body_span={})",
-        file_name,
-        source_map.span_to_diagnostic_string(span),
-        source_map.span_to_diagnostic_string(body_span)
-    );
-
+) -> Option<SourceRegion> {
     let lo = span.lo();
     let hi = span.hi();
 
@@ -424,7 +418,7 @@ fn make_code_region(
     start_line = source_map.doctest_offset_line(&file.name, start_line);
     end_line = source_map.doctest_offset_line(&file.name, end_line);
 
-    check_code_region(CodeRegion {
+    check_source_region(SourceRegion {
         file_name,
         start_line: start_line as u32,
         start_col: start_col as u32,
@@ -433,12 +427,12 @@ fn make_code_region(
     })
 }
 
-/// If `llvm-cov` sees a code region that is improperly ordered (end < start),
+/// If `llvm-cov` sees a source region that is improperly ordered (end < start),
 /// it will immediately exit with a fatal error. To prevent that from happening,
 /// discard regions that are improperly ordered, or might be interpreted in a
 /// way that makes them improperly ordered.
-fn check_code_region(code_region: CodeRegion) -> Option<CodeRegion> {
-    let CodeRegion { file_name: _, start_line, start_col, end_line, end_col } = code_region;
+fn check_source_region(source_region: SourceRegion) -> Option<SourceRegion> {
+    let SourceRegion { file_name: _, start_line, start_col, end_line, end_col } = source_region;
 
     // Line/column coordinates are supposed to be 1-based. If we ever emit
     // coordinates of 0, `llvm-cov` might misinterpret them.
@@ -451,17 +445,17 @@ fn check_code_region(code_region: CodeRegion) -> Option<CodeRegion> {
     let is_ordered = (start_line, start_col) <= (end_line, end_col);
 
     if all_nonzero && end_col_has_high_bit_unset && is_ordered {
-        Some(code_region)
+        Some(source_region)
     } else {
         debug!(
-            ?code_region,
+            ?source_region,
             ?all_nonzero,
             ?end_col_has_high_bit_unset,
             ?is_ordered,
-            "Skipping code region that would be misinterpreted or rejected by LLVM"
+            "Skipping source region that would be misinterpreted or rejected by LLVM"
         );
         // If this happens in a debug build, ICE to make it easier to notice.
-        debug_assert!(false, "Improper code region: {code_region:?}");
+        debug_assert!(false, "Improper source region: {source_region:?}");
         None
     }
 }
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 5738173c7a8..c7a9846cd97 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
@@ -862,7 +862,7 @@ where
         _ecx: &mut EvalCtxt<'_, D>,
         goal: Goal<I, Self>,
     ) -> Result<Candidate<I>, NoSolution> {
-        panic!("`BikeshedIntrinsicFrom` does not have an associated type: {:?}", goal)
+        panic!("`TransmuteFrom` does not have an associated type: {:?}", goal)
     }
 
     fn consider_builtin_effects_intersection_candidate(
diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index 14da6c331f1..c6a5e1908f7 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -51,7 +51,9 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses the contents of a module (inner attributes followed by module items).
-    /// We exit once we hit `term`
+    /// We exit once we hit `term` which can be either
+    /// - EOF (for files)
+    /// - `}` for mod items
     pub fn parse_mod(
         &mut self,
         term: &TokenKind,
diff --git a/compiler/rustc_passes/messages.ftl b/compiler/rustc_passes/messages.ftl
index e7f208d5ad5..38450fc288a 100644
--- a/compiler/rustc_passes/messages.ftl
+++ b/compiler/rustc_passes/messages.ftl
@@ -672,6 +672,10 @@ passes_should_be_applied_to_fn =
         *[false] not a function definition
     }
 
+passes_should_be_applied_to_fn_or_unit_struct =
+    attribute should be applied to a function definition or unit struct
+    .label = not a function definition or a unit struct
+
 passes_should_be_applied_to_static =
     attribute should be applied to a static
     .label = not a static
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index d1dac9ca6da..5dbb3854c8f 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -517,6 +517,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
             sym::no_mangle,
             sym::naked,
             sym::instruction_set,
+            sym::repr,
             // code generation
             sym::cold,
             sym::target_feature,
@@ -746,12 +747,35 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
             Target::Field | Target::Arm | Target::MacroDef => {
                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "target_feature");
             }
+            Target::Struct if self.tcx.features().struct_target_features => {
+                let ty = self.tcx.hir_node(hir_id).expect_item();
+                match ty.kind {
+                    ItemKind::Struct(data, _) => {
+                        if data.fields().len() != 0 {
+                            self.dcx().emit_err(errors::AttrShouldBeAppliedToFnOrUnitStruct {
+                                attr_span: attr.span,
+                                defn_span: span,
+                            });
+                        }
+                    }
+                    _ => {
+                        panic!("Target::Struct for a non-struct");
+                    }
+                }
+            }
             _ => {
-                self.dcx().emit_err(errors::AttrShouldBeAppliedToFn {
-                    attr_span: attr.span,
-                    defn_span: span,
-                    on_crate: hir_id == CRATE_HIR_ID,
-                });
+                if self.tcx.features().struct_target_features {
+                    self.dcx().emit_err(errors::AttrShouldBeAppliedToFnOrUnitStruct {
+                        attr_span: attr.span,
+                        defn_span: span,
+                    });
+                } else {
+                    self.dcx().emit_err(errors::AttrShouldBeAppliedToFn {
+                        attr_span: attr.span,
+                        defn_span: span,
+                        on_crate: hir_id == CRATE_HIR_ID,
+                    });
+                }
             }
         }
     }
diff --git a/compiler/rustc_passes/src/errors.rs b/compiler/rustc_passes/src/errors.rs
index 1202351bdcd..32db0823cf7 100644
--- a/compiler/rustc_passes/src/errors.rs
+++ b/compiler/rustc_passes/src/errors.rs
@@ -83,6 +83,15 @@ pub struct AttrShouldBeAppliedToFn {
 }
 
 #[derive(Diagnostic)]
+#[diag(passes_should_be_applied_to_fn_or_unit_struct)]
+pub struct AttrShouldBeAppliedToFnOrUnitStruct {
+    #[primary_span]
+    pub attr_span: Span,
+    #[label]
+    pub defn_span: Span,
+}
+
+#[derive(Diagnostic)]
 #[diag(passes_should_be_applied_to_fn, code = E0739)]
 pub struct TrackedCallerWrongLocation {
     #[primary_span]
diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
index 95d171409d8..4fb3702b05d 100644
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@@ -2893,6 +2893,7 @@ pub enum PpHirMode {
 }
 
 #[derive(Copy, Clone, PartialEq, Debug)]
+/// Pretty print mode
 pub enum PpMode {
     /// Options that print the source code, i.e.
     /// `-Zunpretty=normal` and `-Zunpretty=expanded`
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 2957105288b..c64fefd457a 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -1852,6 +1852,7 @@ symbols! {
         stringify,
         struct_field_attributes,
         struct_inherit,
+        struct_target_features,
         struct_variant,
         structural_match,
         structural_peq,
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 9f0282319ec..def9d6e9a31 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
@@ -438,6 +438,8 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                         let is_target_feature_fn = if let ty::FnDef(def_id, _) =
                             *leaf_trait_ref.skip_binder().self_ty().kind()
                         {
+                            // FIXME(struct_target_features): should a function that inherits
+                            // target_features through arguments implement Fn traits?
                             !self.tcx.codegen_fn_attrs(def_id).target_features.is_empty()
                         } else {
                             false
diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
index cb8deeaedb6..a21feec4b1a 100644
--- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
@@ -545,6 +545,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             // Provide an impl for suitable functions, rejecting `#[target_feature]` functions (RFC 2396).
             ty::FnDef(def_id, args) => {
                 let tcx = self.tcx();
+                // FIXME(struct_target_features): should a function that inherits target_features
+                // through an argument implement Fn traits?
                 if tcx.fn_sig(def_id).skip_binder().is_fn_trait_compatible()
                     && tcx.codegen_fn_attrs(def_id).target_features.is_empty()
                 {