[clang][FMV] Allow declaration of function versions in namespaces. (#93044)

Fixes the following bug:

namespace Name {
int __attribute((target_version("default"))) foo() { return 0; }
}

namespace Name {
int __attribute((target_version("sve"))) foo() { return 1; }
}

int bar() { return Name::foo(); }

error: redefinition of 'foo'
  int __attribute((target_version("sve"))) foo() { return 1; }

note: previous definition is here
  int __attribute((target_version("default"))) foo() { return 0; }

While fixing this I also found that in the absence of default version
declaration, the one we implicitly create has incorrect mangling if
we are in a namespace:

namespace OtherName {
int __attribute((target_version("sve"))) foo() { return 2; }
}

int baz() { return OtherName::foo(); }

In this example instead of creating a declaration for the symbol
@_ZN9OtherName3fooEv.default we are creating one for the symbol
@_Z3foov.default (the namespace mangling prefix is omitted).
This has now been fixed.

1 files changed, 1 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 60ef28a..e4774a5 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -4150,7 +4150,7 @@ llvm::GlobalValue::LinkageTypes getMultiversionLinkage(CodeGenModule &CGM,
 }
 
 static FunctionDecl *createDefaultTargetVersionFrom(const FunctionDecl *FD) {
-  DeclContext *DeclCtx = FD->getASTContext().getTranslationUnitDecl();
+  auto *DeclCtx = const_cast<DeclContext *>(FD->getDeclContext());
   TypeSourceInfo *TInfo = FD->getTypeSourceInfo();
   StorageClass SC = FD->getStorageClass();
   DeclarationName Name = FD->getNameInfo().getName();