Implement struct_target_features.

compiler/rustc_codegen_gcc/src/attributes.rs

@@ -6,7 +6,7 @@ use rustc_attr::InlineAttr;
 use rustc_attr::InstructionSetAttr;
 #[cfg(feature = "master")]
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
-use rustc_middle::ty;
+use rustc_middle::ty::{self, ParamEnv};
 
 use crate::context::CodegenCx;
 use crate::gcc_util::to_gcc_features;
@@ -70,8 +70,9 @@ pub fn from_fn_attrs<'gcc, 'tcx>(
         }
     }
 
-    let mut function_features = codegen_fn_attrs
-        .target_features
+    let function_features =
+        codegen_fn_attrs.target_features_for_instance(cx.tcx, ParamEnv::reveal_all(), instance);
+    let mut function_features = function_features
         .iter()
         .map(|features| features.name.as_str())
         .flat_map(|feat| to_gcc_features(cx.tcx.sess, feat).into_iter())

compiler/rustc_codegen_llvm/src/attributes.rs

@@ -4,7 +4,7 @@ use rustc_attr::{InlineAttr, InstructionSetAttr, OptimizeAttr};
 use rustc_codegen_ssa::traits::*;
 use rustc_hir::def_id::DefId;
 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, PatchableFunctionEntry};
-use rustc_middle::ty::{self, TyCtxt};
+use rustc_middle::ty::{self, ParamEnv, TyCtxt};
 use rustc_session::config::{BranchProtection, FunctionReturn, OptLevel, PAuthKey, PacRet};
 use rustc_target::spec::{FramePointer, SanitizerSet, StackProbeType, StackProtector};
 use smallvec::SmallVec;
@@ -499,7 +499,9 @@ pub(crate) fn llfn_attrs_from_instance<'ll, 'tcx>(
     to_add.extend(tune_cpu_attr(cx));
 
     let function_features =
-        codegen_fn_attrs.target_features.iter().map(|f| f.name.as_str()).collect::<Vec<&str>>();
+        codegen_fn_attrs.target_features_for_instance(cx.tcx, ParamEnv::reveal_all(), instance);
+    let function_features =
+        function_features.iter().map(|f| f.name.as_str()).collect::<Vec<&str>>();
 
     let function_features = function_features
         .iter()

compiler/rustc_codegen_ssa/messages.ftl

@@ -243,7 +243,7 @@ codegen_ssa_symbol_file_write_failure = failed to write symbols file: {$error}
 codegen_ssa_target_feature_disable_or_enable =
     the target features {$features} must all be either enabled or disabled together
 
-codegen_ssa_target_feature_safe_trait = `#[target_feature(..)]` cannot be applied to safe trait method
+codegen_ssa_target_feature_safe_trait = `#[target_feature(enable = ..)]` cannot be applied to safe trait method
     .label = cannot be applied to safe trait method
     .label_def = not an `unsafe` function
 

compiler/rustc_codegen_ssa/src/codegen_attrs.rs

@@ -9,7 +9,8 @@ use rustc_hir::def_id::{DefId, LOCAL_CRATE, LocalDefId};
 use rustc_hir::weak_lang_items::WEAK_LANG_ITEMS;
 use rustc_hir::{LangItem, lang_items};
 use rustc_middle::middle::codegen_fn_attrs::{
-    CodegenFnAttrFlags, CodegenFnAttrs, PatchableFunctionEntry,
+    CodegenFnAttrFlags, CodegenFnAttrs, PatchableFunctionEntry, TargetFeature,
+    extend_with_struct_target_features,
 };
 use rustc_middle::mir::mono::Linkage;
 use rustc_middle::query::Providers;
@@ -79,23 +80,26 @@ 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.
         // In these cases, we bail from performing further checks that are only meaningful for
         // 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 {
@@ -247,7 +251,12 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                     && let Some(fn_sig) = fn_sig()
                     && fn_sig.skip_binder().safety() == hir::Safety::Safe
                 {
-                    if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
+                    if attr.meta_item_list().is_some_and(|list| {
+                        list.len() == 1 && list[0].ident().is_some_and(|x| x.name == sym::from_args)
+                    }) {
+                        // #[target_feature(from_args)] can be applied to safe functions and safe
+                        // trait methods.
+                    } else if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
                         // The `#[target_feature]` attribute is allowed on
                         // WebAssembly targets on all functions, including safe
                         // ones. Other targets require that `#[target_feature]` is
@@ -285,7 +294,8 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                     tcx,
                     attr,
                     supported_target_features,
-                    &mut codegen_fn_attrs.target_features,
+                    &mut codegen_fn_attrs.def_target_features,
+                    Some(&mut codegen_fn_attrs.target_features_from_args),
                 );
             }
             sym::linkage => {
@@ -591,16 +601,39 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
         let owner_id = tcx.parent(did.to_def_id());
         if tcx.def_kind(owner_id).has_codegen_attrs() {
             codegen_fn_attrs
-                .target_features
-                .extend(tcx.codegen_fn_attrs(owner_id).target_features.iter().copied());
+                .def_target_features
+                .extend(tcx.codegen_fn_attrs(owner_id).def_target_features.iter().copied());
         }
     }
 
-    // If a function uses #[target_feature] it can't be inlined into general
+    if let Some(sig) = fn_sig_outer()
+        && codegen_fn_attrs.target_features_from_args
+    {
+        let mut additional_tf = vec![];
+        for ty in sig.skip_binder().inputs().skip_binder() {
+            extend_with_struct_target_features(
+                tcx,
+                tcx.param_env(did.to_def_id()).and(*ty),
+                &mut additional_tf,
+            )
+        }
+        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
+            .def_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.
-    if !codegen_fn_attrs.target_features.is_empty() && codegen_fn_attrs.inline == InlineAttr::Always
+    if !codegen_fn_attrs.def_target_features.is_empty()
+        && codegen_fn_attrs.inline == InlineAttr::Always
     {
         if let Some(span) = inline_span {
             tcx.dcx().span_err(
@@ -666,7 +699,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
     if let Some(features) = check_tied_features(
         tcx.sess,
         &codegen_fn_attrs
-            .target_features
+            .def_target_features
             .iter()
             .map(|features| (features.name.as_str(), true))
             .collect(),
@@ -779,6 +812,20 @@ 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, None);
+    }
+    tcx.arena.alloc_slice(&features)
+}
+
 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,
+        struct_target_features,
+        ..*providers
+    };
 }

compiler/rustc_codegen_ssa/src/target_features.rs

@@ -20,6 +20,7 @@ pub(crate) fn from_target_feature(
     attr: &ast::Attribute,
     supported_target_features: &UnordMap<String, Option<Symbol>>,
     target_features: &mut Vec<TargetFeature>,
+    mut features_from_args: Option<&mut bool>,
 ) {
     let Some(list) = attr.meta_item_list() else { return };
     let bad_item = |span| {
@@ -33,6 +34,14 @@ pub(crate) fn from_target_feature(
     let rust_features = tcx.features();
     let mut added_target_features = Vec::new();
     for item in list {
+        if let Some(ref mut from_args) = features_from_args
+            && item.ident().is_some_and(|x| x.name == sym::from_args)
+            && tcx.features().struct_target_features
+        {
+            **from_args = true;
+            continue;
+        }
+
         // Only `enable = ...` is accepted in the meta-item list.
         if !item.has_name(sym::enable) {
             bad_item(item.span());
@@ -128,7 +137,7 @@ fn asm_target_features(tcx: TyCtxt<'_>, did: DefId) -> &FxIndexSet<Symbol> {
     let mut target_features = tcx.sess.unstable_target_features.clone();
     if tcx.def_kind(did).has_codegen_attrs() {
         let attrs = tcx.codegen_fn_attrs(did);
-        target_features.extend(attrs.target_features.iter().map(|feature| feature.name));
+        target_features.extend(attrs.def_target_features.iter().map(|feature| feature.name));
         match attrs.instruction_set {
             None => {}
             Some(InstructionSetAttr::ArmA32) => {
@@ -144,7 +153,7 @@ fn asm_target_features(tcx: TyCtxt<'_>, did: DefId) -> &FxIndexSet<Symbol> {
     tcx.arena.alloc(target_features)
 }
 
-/// Checks the function annotated with `#[target_feature]` is not a safe
+/// Checks the function annotated with `#[target_feature(enable = ...)]` is not a safe
 /// trait method implementation, reporting an error if it is.
 pub(crate) fn check_target_feature_trait_unsafe(tcx: TyCtxt<'_>, id: LocalDefId, attr_span: Span) {
     if let DefKind::AssocFn = tcx.def_kind(id) {

compiler/rustc_feature/src/unstable.rs

@@ -601,6 +601,8 @@ 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.

compiler/rustc_hir/src/def.rs

@@ -329,6 +329,43 @@ 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 => true,
+            DefKind::Fn
+            | DefKind::Union
+            | DefKind::Enum
+            | 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.

compiler/rustc_hir_analysis/src/check/entry.rs

@@ -105,7 +105,7 @@ fn check_main_fn_ty(tcx: TyCtxt<'_>, main_def_id: DefId) {
         error = true;
     }
 
-    if !tcx.codegen_fn_attrs(main_def_id).target_features.is_empty()
+    if !tcx.codegen_fn_attrs(main_def_id).def_target_features.is_empty()
         // Calling functions with `#[target_feature]` is not unsafe on WASM, see #84988
         && !tcx.sess.target.is_like_wasm
         && !tcx.sess.opts.actually_rustdoc

compiler/rustc_hir_typeck/src/coercion.rs

@@ -920,10 +920,15 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
                         return Err(TypeError::IntrinsicCast);
                     }
 
-                    // Safe `#[target_feature]` functions are not assignable to safe fn pointers (RFC 2396).
-
+                    // Safe functions with explicit `#[target_feature]` attributes are not
+                    // assignable to safe fn pointers (RFC 2396).
                     if b_hdr.safety == hir::Safety::Safe
-                        && !self.tcx.codegen_fn_attrs(def_id).target_features.is_empty()
+                        && self
+                            .tcx
+                            .codegen_fn_attrs(def_id)
+                            .def_target_features
+                            .iter()
+                            .any(|x| !x.implied)
                     {
                         return Err(TypeError::TargetFeatureCast(def_id));
                     }

compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs

@@ -254,6 +254,7 @@ provide! { tcx, def_id, other, cdata,
     variances_of => { table }
     fn_sig => { table }
     codegen_fn_attrs => { table }
+    struct_target_features => { table_defaulted_array }
     impl_trait_header => { table }
     const_param_default => { table }
     object_lifetime_default => { table }

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -1401,6 +1401,9 @@ 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_defaulted_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);

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;
@@ -404,6 +404,7 @@ define_tables! {
     // individually instead of `DefId`s.
     module_children_reexports: Table<DefIndex, LazyArray<ModChild>>,
     cross_crate_inlinable: Table<DefIndex, bool>,
+    struct_target_features: Table<DefIndex, LazyArray<TargetFeature>>,
 
 - optional:
     attributes: Table<DefIndex, LazyArray<ast::Attribute>>,