Port #[target_feature] to the new attribute parsing infrastructure

Signed-off-by: Jonathan Brouwer <jonathantbrouwer@gmail.com>

Author: JonathanBrouwer

Cargo.lock

@@ -4629,6 +4629,7 @@ dependencies = [
  "itertools",
  "rustc_abi",
  "rustc_ast",
+ "rustc_attr_data_structures",
  "rustc_data_structures",
  "rustc_errors",
  "rustc_fluent_macro",

compiler/rustc_ast_lowering/src/item.rs

@@ -2,6 +2,7 @@ use rustc_abi::ExternAbi;
 use rustc_ast::ptr::P;
 use rustc_ast::visit::AssocCtxt;
 use rustc_ast::*;
+use rustc_attr_data_structures::{AttributeKind, find_attr};
 use rustc_errors::{E0570, ErrorGuaranteed, struct_span_code_err};
 use rustc_hir::def::{DefKind, PerNS, Res};
 use rustc_hir::def_id::{CRATE_DEF_ID, LocalDefId};
@@ -1621,7 +1622,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let safety = self.lower_safety(h.safety, default_safety);
 
         // Treat safe `#[target_feature]` functions as unsafe, but also remember that we did so.
-        let safety = if attrs.iter().any(|attr| attr.has_name(sym::target_feature))
+        let safety = if find_attr!(attrs, AttributeKind::TargetFeature { .. })
             && safety.is_safe()
             && !self.tcx.sess.target.is_like_wasm
         {

compiler/rustc_attr_data_structures/src/attributes.rs

@@ -198,10 +198,10 @@ pub enum AttributeKind {
     Align { align: Align, span: Span },
 
     /// Represents `#[rustc_allow_const_fn_unstable]`.
-    AllowConstFnUnstable(ThinVec<Symbol>),
+    AllowConstFnUnstable(ThinVec<Symbol>, Span),
 
     /// Represents `#[allow_internal_unstable]`.
-    AllowInternalUnstable(ThinVec<(Symbol, Span)>),
+    AllowInternalUnstable(ThinVec<(Symbol, Span)>, Span),
 
     /// Represents `#[rustc_as_ptr]` (used by the `dangling_pointers_from_temporaries` lint).
     AsPtr(Span),
@@ -309,6 +309,9 @@ pub enum AttributeKind {
         span: Span,
     },
 
+    /// Represents `#[target_feature(enable = "...")]`
+    TargetFeature(ThinVec<(Symbol, Span)>, Span),
+
     /// Represents `#[track_caller]`
     TrackCaller(Span),
 

compiler/rustc_attr_data_structures/src/encode_cross_crate.rs

@@ -42,6 +42,7 @@ impl AttributeKind {
             RustcLayoutScalarValidRangeStart(..) => Yes,
             RustcObjectLifetimeDefault => No,
             SkipDuringMethodDispatch { .. } => No,
+            TargetFeature(..) => No,
             TrackCaller(..) => Yes,
             Used { .. } => No,
         }

compiler/rustc_attr_parsing/src/attributes/allow_unstable.rs

@@ -13,7 +13,8 @@ pub(crate) struct AllowInternalUnstableParser;
 impl<S: Stage> CombineAttributeParser<S> for AllowInternalUnstableParser {
     const PATH: &[Symbol] = &[sym::allow_internal_unstable];
     type Item = (Symbol, Span);
-    const CONVERT: ConvertFn<Self::Item> = AttributeKind::AllowInternalUnstable;
+    const CONVERT: ConvertFn<Self::Item> =
+        |items, span| AttributeKind::AllowInternalUnstable(items, span);
     const TEMPLATE: AttributeTemplate = template!(Word, List: "feat1, feat2, ...");
 
     fn extend<'c>(
@@ -30,7 +31,7 @@ pub(crate) struct AllowConstFnUnstableParser;
 impl<S: Stage> CombineAttributeParser<S> for AllowConstFnUnstableParser {
     const PATH: &[Symbol] = &[sym::rustc_allow_const_fn_unstable];
     type Item = Symbol;
-    const CONVERT: ConvertFn<Self::Item> = AttributeKind::AllowConstFnUnstable;
+    const CONVERT: ConvertFn<Self::Item> = |items, first_span| AttributeKind::AllowConstFnUnstable(items, first_span);
     const TEMPLATE: AttributeTemplate = template!(Word, List: "feat1, feat2, ...");
 
     fn extend<'c>(

compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs

@@ -3,7 +3,10 @@ use rustc_feature::{AttributeTemplate, template};
 use rustc_session::parse::feature_err;
 use rustc_span::{Span, Symbol, sym};
 
-use super::{AcceptMapping, AttributeOrder, AttributeParser, OnDuplicate, SingleAttributeParser};
+use super::{
+    AcceptMapping, AttributeOrder, AttributeParser, CombineAttributeParser, ConvertFn, OnDuplicate,
+    SingleAttributeParser,
+};
 use crate::context::{AcceptContext, FinalizeContext, Stage};
 use crate::parser::ArgParser;
 use crate::session_diagnostics::{NakedFunctionIncompatibleAttribute, NullOnExport};
@@ -309,3 +312,53 @@ impl<S: Stage> AttributeParser<S> for UsedParser {
         })
     }
 }
+
+pub(crate) struct TargetFeatureParser;
+
+impl<S: Stage> CombineAttributeParser<S> for TargetFeatureParser {
+    type Item = (Symbol, Span);
+    const PATH: &[Symbol] = &[sym::target_feature];
+    const CONVERT: ConvertFn<Self::Item> = |items, span| AttributeKind::TargetFeature(items, span);
+    const TEMPLATE: AttributeTemplate = template!(List: "enable = \"feat1, feat2\"");
+
+    fn extend<'c>(
+        cx: &'c mut AcceptContext<'_, '_, S>,
+        args: &'c ArgParser<'_>,
+    ) -> impl IntoIterator<Item = Self::Item> + 'c {
+        let mut features = Vec::new();
+        let ArgParser::List(list) = args else {
+            cx.expected_list(cx.attr_span);
+            return features;
+        };
+        for item in list.mixed() {
+            let Some(name_value) = item.meta_item() else {
+                cx.expected_name_value(item.span(), Some(sym::enable));
+                return features;
+            };
+
+            // Validate name
+            let Some(name) = name_value.path().word_sym() else {
+                cx.expected_name_value(name_value.path().span(), Some(sym::enable));
+                return features;
+            };
+            if name != sym::enable {
+                cx.expected_name_value(name_value.path().span(), Some(sym::enable));
+                return features;
+            }
+
+            // Use value
+            let Some(name_value) = name_value.args().name_value() else {
+                cx.expected_name_value(item.span(), Some(sym::enable));
+                return features;
+            };
+            let Some(value_str) = name_value.value_as_str() else {
+                cx.expected_string_literal(name_value.value_span, Some(name_value.value_as_lit()));
+                return features;
+            };
+            for feature in value_str.as_str().split(",") {
+                features.push((Symbol::intern(feature), item.span()));
+            }
+        }
+        features
+    }
+}

compiler/rustc_attr_parsing/src/attributes/mod.rs

@@ -229,7 +229,7 @@ pub(crate) enum AttributeOrder {
     KeepLast,
 }
 
-type ConvertFn<E> = fn(ThinVec<E>) -> AttributeKind;
+type ConvertFn<E> = fn(ThinVec<E>, Span) -> AttributeKind;
 
 /// Alternative to [`AttributeParser`] that automatically handles state management.
 /// If multiple attributes appear on an element, combines the values of each into a
@@ -260,25 +260,40 @@ pub(crate) trait CombineAttributeParser<S: Stage>: 'static {
 
 /// Use in combination with [`CombineAttributeParser`].
 /// `Combine<T: CombineAttributeParser>` implements [`AttributeParser`].
-pub(crate) struct Combine<T: CombineAttributeParser<S>, S: Stage>(
-    PhantomData<(S, T)>,
-    ThinVec<<T as CombineAttributeParser<S>>::Item>,
-);
+pub(crate) struct Combine<T: CombineAttributeParser<S>, S: Stage> {
+    phantom: PhantomData<(S, T)>,
+    /// A list of all items produced by parsing attributes so far. One attribute can produce any amount of items.
+    items: ThinVec<<T as CombineAttributeParser<S>>::Item>,
+    /// The full span of the first attribute that was encountered.
+    first_span: Option<Span>,
+}
 
 impl<T: CombineAttributeParser<S>, S: Stage> Default for Combine<T, S> {
     fn default() -> Self {
-        Self(Default::default(), Default::default())
+        Self {
+            phantom: Default::default(),
+            items: Default::default(),
+            first_span: Default::default(),
+        }
     }
 }
 
 impl<T: CombineAttributeParser<S>, S: Stage> AttributeParser<S> for Combine<T, S> {
     const ATTRIBUTES: AcceptMapping<Self, S> = &[(
         T::PATH,
         <T as CombineAttributeParser<S>>::TEMPLATE,
-        |group: &mut Combine<T, S>, cx, args| group.1.extend(T::extend(cx, args)),
+        |group: &mut Combine<T, S>, cx, args| {
+            // Keep track of the span of the first attribute, for diagnostics
+            group.first_span.get_or_insert(cx.attr_span);
+            group.items.extend(T::extend(cx, args))
+        },
     )];
 
     fn finalize(self, _cx: &FinalizeContext<'_, '_, S>) -> Option<AttributeKind> {
-        if self.1.is_empty() { None } else { Some(T::CONVERT(self.1)) }
+        if let Some(first_span) = self.first_span {
+            Some(T::CONVERT(self.items, first_span))
+        } else {
+            None
+        }
     }
 }

compiler/rustc_attr_parsing/src/attributes/repr.rs

@@ -23,7 +23,7 @@ pub(crate) struct ReprParser;
 impl<S: Stage> CombineAttributeParser<S> for ReprParser {
     type Item = (ReprAttr, Span);
     const PATH: &[Symbol] = &[sym::repr];
-    const CONVERT: ConvertFn<Self::Item> = AttributeKind::Repr;
+    const CONVERT: ConvertFn<Self::Item> = |items, _| AttributeKind::Repr(items);
     // FIXME(jdonszelmann): never used
     const TEMPLATE: AttributeTemplate =
         template!(List: "C | Rust | align(...) | packed(...) | <integer type> | transparent");

compiler/rustc_attr_parsing/src/context.rs

@@ -16,8 +16,8 @@ use rustc_span::{DUMMY_SP, ErrorGuaranteed, Span, Symbol, sym};
 
 use crate::attributes::allow_unstable::{AllowConstFnUnstableParser, AllowInternalUnstableParser};
 use crate::attributes::codegen_attrs::{
-    ColdParser, ExportNameParser, NakedParser, NoMangleParser, OptimizeParser, TrackCallerParser,
-    UsedParser,
+    ColdParser, ExportNameParser, NakedParser, NoMangleParser, OptimizeParser, TargetFeatureParser,
+    TrackCallerParser, UsedParser,
 };
 use crate::attributes::confusables::ConfusablesParser;
 use crate::attributes::deprecation::DeprecationParser;
@@ -116,6 +116,7 @@ attribute_parsers!(
         Combine<AllowConstFnUnstableParser>,
         Combine<AllowInternalUnstableParser>,
         Combine<ReprParser>,
+        Combine<TargetFeatureParser>,
         // tidy-alphabetical-end
 
         // tidy-alphabetical-start

compiler/rustc_codegen_ssa/messages.ftl

@@ -62,6 +62,10 @@ codegen_ssa_failed_to_get_layout = failed to get layout for {$ty}: {$err}
 
 codegen_ssa_failed_to_write = failed to write {$path}: {$error}
 
+codegen_ssa_feature_not_valid = the feature named `{$feature}` is not valid for this target
+    .label = `{$feature}` is not valid for this target
+    .help = consider removing the leading `+` in the feature name
+
 codegen_ssa_field_associated_value_expected = associated value expected for `{$name}`
 
 codegen_ssa_forbidden_ctarget_feature =

compiler/rustc_codegen_ssa/src/codegen_attrs.rs

@@ -141,6 +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());
 
@@ -190,49 +233,6 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                 codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL
             }
             sym::thread_local => codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL,
-            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()));
@@ -536,10 +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,

compiler/rustc_codegen_ssa/src/errors.rs

@@ -1292,3 +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,
+}