Mark naked functions as never inline in codegen_fn_attrs

Use code generation attributes to ensure that naked functions are never
inline, replacing separate checks in MIR inliner and LLVM code
generation.

Author: tmiasko

compiler/rustc_codegen_llvm/src/attributes.rs

@@ -258,13 +258,12 @@ pub fn from_fn_attrs<'ll, 'tcx>(
         OptimizeAttr::Speed => {}
     }
 
-    let inline = if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::NAKED) {
-        InlineAttr::Never
-    } else if codegen_fn_attrs.inline == InlineAttr::None && instance.def.requires_inline(cx.tcx) {
-        InlineAttr::Hint
-    } else {
-        codegen_fn_attrs.inline
-    };
+    let inline =
+        if codegen_fn_attrs.inline == InlineAttr::None && instance.def.requires_inline(cx.tcx) {
+            InlineAttr::Hint
+        } else {
+            codegen_fn_attrs.inline
+        };
     to_add.extend(inline_attr(cx, inline));
 
     // The `uwtable` attribute according to LLVM is:

compiler/rustc_hir_analysis/src/collect.rs

@@ -2075,6 +2075,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: DefId) -> CodegenFnAttrs {
 
     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::NAKED) {
         codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_COVERAGE;
+        codegen_fn_attrs.inline = InlineAttr::Never;
     }
 
     // Weak lang items have the same semantics as "std internal" symbols in the

compiler/rustc_mir_transform/src/inline.rs

@@ -363,10 +363,6 @@ impl<'tcx> Inliner<'tcx> {
             return Err("C variadic");
         }
 
-        if callee_attrs.flags.contains(CodegenFnAttrFlags::NAKED) {
-            return Err("naked");
-        }
-
         if callee_attrs.flags.contains(CodegenFnAttrFlags::COLD) {
             return Err("cold");
         }