When an internal-linkage function or variable is declared within an extern "C"

linkage specification, and is marked as __attribute__((used)), try to also give
it the unmangled name (by emitting an internal linkage alias) if nothing else
within the translation unit would use that name. This allows inline asm in that
translation unit to use the entity via its unmangled name, which people
apparently rely on.

llvm-svn: 178950

1 files changed, 16 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.h b/clang/lib/CodeGen/CodeGenModule.h
index 5b2153e5ff3..ccac4371c49 100644
--- a/clang/lib/CodeGen/CodeGenModule.h
+++ b/clang/lib/CodeGen/CodeGenModule.h
@@ -305,6 +305,12 @@ class CodeGenModule : public CodeGenTypeCache {
   llvm::DenseMap<QualType, llvm::Constant *> AtomicSetterHelperFnMap;
   llvm::DenseMap<QualType, llvm::Constant *> AtomicGetterHelperFnMap;
 
+  /// Map used to track internal linkage functions declared within
+  /// extern "C" regions.
+  typedef llvm::DenseMap<IdentifierInfo *,
+                         llvm::GlobalValue *> StaticExternCMap;
+  StaticExternCMap StaticExternCValues;
+
   /// CXXGlobalInits - Global variables with initializers that need to run
   /// before main.
   std::vector<llvm::Constant*> CXXGlobalInits;
@@ -736,6 +742,12 @@ public:
   // variable has been instantiated.
   void HandleCXXStaticMemberVarInstantiation(VarDecl *VD);
 
+  /// \brief If the declaration has internal linkage but is inside an
+  /// extern "C" linkage specification, prepare to emit an alias for it
+  /// to the expected name.
+  template<typename SomeDecl>
+  void MaybeHandleStaticInExternC(const SomeDecl *D, llvm::GlobalValue *GV);
+
   /// AddUsedGlobal - Add a global which should be forced to be
   /// present in the object file; these are emitted to the llvm.used
   /// metadata global.
@@ -1048,6 +1060,10 @@ private:
   /// \brief Emit the link options introduced by imported modules.
   void EmitModuleLinkOptions();
 
+  /// \brief Emit aliases for internal-linkage declarations inside "C" language
+  /// linkage specifications, giving them the "expected" name where possible.
+  void EmitStaticExternCAliases();
+
   void EmitDeclMetadata();
 
   /// EmitCoverageFile - Emit the llvm.gcov metadata used to tell LLVM where