add a flag to codegen fn attrs for foreign items

Author: jdonszelmann

compiler/rustc_codegen_ssa/src/back/symbol_export.rs

@@ -570,7 +570,7 @@ fn symbol_export_level(tcx: TyCtxt<'_>, sym_def_id: DefId) -> SymbolExportLevel
     // core/std/allocators/etc. For example symbols used to hook up allocation
     // are not considered for export
     let codegen_fn_attrs = tcx.codegen_fn_attrs(sym_def_id);
-    let is_extern = codegen_fn_attrs.contains_extern_indicator(tcx, sym_def_id);
+    let is_extern = codegen_fn_attrs.contains_extern_indicator();
     let std_internal =
         codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL);
 

compiler/rustc_codegen_ssa/src/codegen_attrs.rs

@@ -385,6 +385,8 @@ fn apply_overrides(tcx: TyCtxt<'_>, did: LocalDefId, codegen_fn_attrs: &mut Code
 
     // Foreign items by default use no mangling for their symbol name.
     if tcx.is_foreign_item(did) {
+        codegen_fn_attrs.flags |= CodegenFnAttrFlags::FOREIGN_ITEM;
+
         // There's a few exceptions to this rule though:
         if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
             // * `#[rustc_std_internal_symbol]` mangles the symbol name in a special way

compiler/rustc_middle/src/middle/codegen_fn_attrs.rs

@@ -2,7 +2,6 @@ use std::borrow::Cow;
 
 use rustc_abi::Align;
 use rustc_hir::attrs::{InlineAttr, InstructionSetAttr, Linkage, OptimizeAttr};
-use rustc_hir::def_id::DefId;
 use rustc_macros::{HashStable, TyDecodable, TyEncodable};
 use rustc_span::Symbol;
 use rustc_target::spec::SanitizerSet;
@@ -161,6 +160,8 @@ bitflags::bitflags! {
         const ALLOCATOR_ZEROED          = 1 << 14;
         /// `#[no_builtins]`: indicates that disable implicit builtin knowledge of functions for the function.
         const NO_BUILTINS               = 1 << 15;
+        /// Marks foreign items, to make `contains_extern_indicator` cheaper.
+        const FOREIGN_ITEM              = 1 << 16;
     }
 }
 rustc_data_structures::external_bitflags_debug! { CodegenFnAttrFlags }
@@ -194,8 +195,8 @@ impl CodegenFnAttrs {
     /// * `#[linkage]` is present
     ///
     /// Keep this in sync with the logic for the unused_attributes for `#[inline]` lint.
-    pub fn contains_extern_indicator(&self, tcx: TyCtxt<'_>, did: DefId) -> bool {
-        if tcx.is_foreign_item(did) {
+    pub fn contains_extern_indicator(&self) -> bool {
+        if self.flags.contains(CodegenFnAttrFlags::FOREIGN_ITEM) {
             return false;
         }
 

compiler/rustc_middle/src/mir/mono.rs

@@ -149,7 +149,7 @@ impl<'tcx> MonoItem<'tcx> {
         // instantiation:
         // We emit an unused_attributes lint for this case, which should be kept in sync if possible.
         let codegen_fn_attrs = tcx.codegen_instance_attrs(instance.def);
-        if codegen_fn_attrs.contains_extern_indicator(tcx, instance.def.def_id())
+        if codegen_fn_attrs.contains_extern_indicator()
             || codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::NAKED)
         {
             return InstantiationMode::GloballyShared { may_conflict: false };

compiler/rustc_mir_transform/src/cross_crate_inline.rs

@@ -18,7 +18,7 @@ fn cross_crate_inlinable(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
     let codegen_fn_attrs = tcx.codegen_fn_attrs(def_id);
     // If this has an extern indicator, then this function is globally shared and thus will not
     // generate cgu-internal copies which would make it cross-crate inlinable.
-    if codegen_fn_attrs.contains_extern_indicator(tcx, def_id.into()) {
+    if codegen_fn_attrs.contains_extern_indicator() {
         return false;
     }
 

compiler/rustc_passes/src/check_attr.rs

@@ -495,7 +495,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 {
                     let attrs = self.tcx.codegen_fn_attrs(did);
                     // Not checking naked as `#[inline]` is forbidden for naked functions anyways.
-                    if attrs.contains_extern_indicator(self.tcx, did.into()) {
+                    if attrs.contains_extern_indicator() {
                         self.tcx.emit_node_span_lint(
                             UNUSED_ATTRIBUTES,
                             hir_id,

compiler/rustc_passes/src/dead.rs

@@ -706,7 +706,7 @@ fn has_allow_dead_code_or_lang_attr(
 
             // #[used], #[no_mangle], #[export_name], etc also keeps the item alive
             // forcefully, e.g., for placing it in a specific section.
-            cg_attrs.contains_extern_indicator(tcx, def_id.into())
+            cg_attrs.contains_extern_indicator()
                 || cg_attrs.flags.contains(CodegenFnAttrFlags::USED_COMPILER)
                 || cg_attrs.flags.contains(CodegenFnAttrFlags::USED_LINKER)
         }

compiler/rustc_passes/src/reachable.rs

@@ -183,7 +183,7 @@ impl<'tcx> ReachableContext<'tcx> {
             } else {
                 CodegenFnAttrs::EMPTY
             };
-            let is_extern = codegen_attrs.contains_extern_indicator(self.tcx, search_item.into());
+            let is_extern = codegen_attrs.contains_extern_indicator();
             if is_extern {
                 self.reachable_symbols.insert(search_item);
             }
@@ -425,7 +425,7 @@ fn has_custom_linkage(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
     }
 
     let codegen_attrs = tcx.codegen_fn_attrs(def_id);
-    codegen_attrs.contains_extern_indicator(tcx, def_id.into())
+    codegen_attrs.contains_extern_indicator()
         // FIXME(nbdd0121): `#[used]` are marked as reachable here so it's picked up by
         // `linked_symbols` in cg_ssa. They won't be exported in binary or cdylib due to their
         // `SymbolExportLevel::Rust` export level but may end up being exported in dylibs.

src/tools/clippy/clippy_lints/src/missing_inline.rs

@@ -190,5 +190,5 @@ impl<'tcx> LateLintPass<'tcx> for MissingInline {
 /// and a rustc warning would be triggered, see #15301
 fn fn_is_externally_exported(cx: &LateContext<'_>, def_id: DefId) -> bool {
     let attrs = cx.tcx.codegen_fn_attrs(def_id);
-    attrs.contains_extern_indicator(cx.tcx, def_id)
+    attrs.contains_extern_indicator()
 }

src/tools/miri/src/bin/miri.rs

@@ -279,7 +279,7 @@ impl rustc_driver::Callbacks for MiriBeRustCompilerCalls {
                                 return None;
                             }
                             let codegen_fn_attrs = tcx.codegen_fn_attrs(local_def_id);
-                            if codegen_fn_attrs.contains_extern_indicator(tcx, local_def_id.into())
+                            if codegen_fn_attrs.contains_extern_indicator()
                                 || codegen_fn_attrs
                                     .flags
                                     .contains(CodegenFnAttrFlags::USED_COMPILER)