compiler: Apply target features to the entry function

Fixes #146143

Author: heiher

compiler/rustc_codegen_gcc/src/context.rs

@@ -483,6 +483,10 @@ impl<'gcc, 'tcx> MiscCodegenMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
         // TODO(antoyo)
     }
 
+    fn apply_target_features(&self, _llfn: Function<'gcc>) {
+        // TODO(antoyo)
+    }
+
     fn declare_c_main(&self, fn_type: Self::Type) -> Option<Self::Function> {
         let entry_name = self.sess().target.entry_name.as_ref();
         if !self.functions.borrow().contains_key(entry_name) {

compiler/rustc_codegen_llvm/src/context.rs

@@ -846,6 +846,16 @@ impl<'ll, 'tcx> MiscCodegenMethods<'tcx> for CodegenCx<'ll, 'tcx> {
         attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &attrs);
     }
 
+    fn apply_target_features(&self, llfn: &'ll Value) {
+        let mut attrs = SmallVec::<[_; 2]>::new();
+        let global_features = self.tcx.global_backend_features(()).iter().map(|s| s.as_str());
+        let target_features: String = global_features.intersperse(",").collect();
+        if !target_features.is_empty() {
+            attrs.push(llvm::CreateAttrStringValue(self.llcx, "target-features", &target_features));
+        }
+        attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &attrs);
+    }
+
     fn declare_c_main(&self, fn_type: Self::Type) -> Option<Self::Function> {
         let entry_name = self.sess().target.entry_name.as_ref();
         if self.get_declared_value(entry_name).is_none() {

compiler/rustc_codegen_ssa/src/base.rs

@@ -524,6 +524,7 @@ pub fn maybe_create_entry_wrapper<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
         // `main` should respect same config for frame pointer elimination as rest of code
         cx.set_frame_pointer_type(llfn);
         cx.apply_target_cpu_attr(llfn);
+        cx.apply_target_features(llfn);
 
         let llbb = Bx::append_block(cx, llfn, "top");
         let mut bx = Bx::build(cx, llbb);

compiler/rustc_codegen_ssa/src/traits/misc.rs

@@ -23,6 +23,7 @@ pub trait MiscCodegenMethods<'tcx>: BackendTypes {
     fn sess(&self) -> &Session;
     fn set_frame_pointer_type(&self, llfn: Self::Function);
     fn apply_target_cpu_attr(&self, llfn: Self::Function);
+    fn apply_target_features(&self, llfn: Self::Function);
     /// Declares the extern "C" main function for the entry point. Returns None if the symbol
     /// already exists.
     fn declare_c_main(&self, fn_type: Self::Type) -> Option<Self::Function>;