Port #[target_feature] to the new attribute parsing infrastructure

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

Author: JonathanBrouwer

Cargo.lock

@@ -4555,6 +4555,7 @@ 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

@@ -190,7 +190,7 @@ pub enum AttributeKind {
     AllowConstFnUnstable(ThinVec<Symbol>),
 
     /// 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),
@@ -283,6 +283,9 @@ pub enum AttributeKind {
         span: Span,
     },
 
+    /// Represents `#[target_feature(enable = "...")]`
+    TargetFeature(ThinVec<(Symbol, Span)>, Span),
+
     /// Represents `#[track_caller]`
     TrackCaller(Span),
     // tidy-alphabetical-end

compiler/rustc_attr_data_structures/src/encode_cross_crate.rs

@@ -37,6 +37,7 @@ impl AttributeKind {
             Optimize(..) => No,
             PubTransparent(..) => Yes,
             SkipDuringMethodDispatch { .. } => No,
+            TargetFeature(..) => No,
             TrackCaller(..) => Yes,
         }
     }

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> =
+        ConvertFn::WithFirstAttributeSpan(AttributeKind::AllowInternalUnstable);
     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> = ConvertFn::Simple(AttributeKind::AllowConstFnUnstable);
     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};
@@ -228,3 +231,54 @@ impl<S: Stage> SingleAttributeParser<S> for NoMangleParser {
         Some(AttributeKind::NoMangle(cx.attr_span))
     }
 }
+
+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> =
+        ConvertFn::WithFirstAttributeSpan(AttributeKind::TargetFeature);
+    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

@@ -227,7 +227,10 @@ pub(crate) enum AttributeOrder {
     KeepLast,
 }
 
-type ConvertFn<E> = fn(ThinVec<E>) -> AttributeKind;
+pub(crate) enum ConvertFn<E> {
+    Simple(fn(ThinVec<E>) -> AttributeKind),
+    WithFirstAttributeSpan(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
@@ -261,22 +264,36 @@ pub(crate) trait CombineAttributeParser<S: Stage>: 'static {
 pub(crate) struct Combine<T: CombineAttributeParser<S>, S: Stage>(
     PhantomData<(S, T)>,
     ThinVec<<T as CombineAttributeParser<S>>::Item>,
+    Option<Span>,
 );
 
 impl<T: CombineAttributeParser<S>, S: Stage> Default for Combine<T, S> {
     fn default() -> Self {
-        Self(Default::default(), Default::default())
+        Self(Default::default(), Default::default(), 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
+            if group.2.is_none() {
+                group.2 = Some(cx.attr_span);
+            }
+            group.1.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.2 {
+            Some(match T::CONVERT {
+                ConvertFn::Simple(f) => f(self.1),
+                ConvertFn::WithFirstAttributeSpan(f) => f(self.1, 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> = ConvertFn::Simple(AttributeKind::Repr);
     // FIXME(jdonszelmann): never used
     const TEMPLATE: AttributeTemplate =
         template!(List: "C | Rust | align(...) | packed(...) | <integer type> | transparent");

compiler/rustc_attr_parsing/src/context.rs

@@ -16,7 +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,
+    ColdParser, ExportNameParser, NakedParser, NoMangleParser, OptimizeParser, TargetFeatureParser,
+    TrackCallerParser,
 };
 use crate::attributes::confusables::ConfusablesParser;
 use crate::attributes::deprecation::DeprecationParser;
@@ -109,6 +110,7 @@ attribute_parsers!(
         Combine<AllowConstFnUnstableParser>,
         Combine<AllowInternalUnstableParser>,
         Combine<ReprParser>,
+        Combine<TargetFeatureParser>,
         // tidy-alphabetical-end
 
         // tidy-alphabetical-start

compiler/rustc_codegen_ssa/messages.ftl

@@ -64,6 +64,10 @@ 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 =