3 files changed, 42 insertions, 18 deletions
diff --git a/clang/lib/CodeGen/CGCXX.cpp b/clang/lib/CodeGen/CGCXX.cpp
index 31134be810d..15686f7ff6e 100644
--- a/clang/lib/CodeGen/CGCXX.cpp
+++ b/clang/lib/CodeGen/CGCXX.cpp
@@ -112,33 +112,20 @@ bool CodeGenModule::TryEmitDefinitionAsAlias(GlobalDecl AliasDecl,
   // support aliases with that linkage, fail.
   llvm::GlobalValue::LinkageTypes Linkage = getFunctionLinkage(AliasDecl);
 
-  llvm::GlobalValue::LinkageTypes TargetLinkage
-    = getFunctionLinkage(TargetDecl);
-
-  // Don't create an alias to a linker weak symbol unless we know we can do
-  // that in every TU. This avoids producing different COMDATs in different
-  // TUs.
-  if (llvm::GlobalValue::isWeakForLinker(TargetLinkage)) {
-    if (!InEveryTU)
-      return true;
-
-    // In addition to making sure we produce it in every TU, we have to make
-    // sure llvm keeps it.
-    // FIXME: Instead of outputting an alias we could just replace every use of
-    // AliasDecl with TargetDecl.
-    assert(Linkage == TargetLinkage);
-    Linkage = llvm::GlobalValue::WeakODRLinkage;
-  }
-
   // We can't use an alias if the linkage is not valid for one.
   if (!llvm::GlobalAlias::isValidLinkage(Linkage))
     return true;
 
+  llvm::GlobalValue::LinkageTypes TargetLinkage =
+      getFunctionLinkage(TargetDecl);
+
   // Check if we have it already.
   StringRef MangledName = getMangledName(AliasDecl);
   llvm::GlobalValue *Entry = GetGlobalValue(MangledName);
   if (Entry && !Entry->isDeclaration())
     return false;
+  if (Replacements.count(MangledName))
+    return false;
 
   // Derive the type for the alias.
   llvm::PointerType *AliasType
@@ -152,6 +139,22 @@ bool CodeGenModule::TryEmitDefinitionAsAlias(GlobalDecl AliasDecl,
   if (Ref->getType() != AliasType)
     Aliasee = llvm::ConstantExpr::getBitCast(Ref, AliasType);
 
+  // Don't create an alias to a linker weak symbol unless we know we can do
+  // that in every TU. This avoids producing different COMDATs in different
+  // TUs.
+  if (llvm::GlobalValue::isWeakForLinker(TargetLinkage)) {
+    if (!InEveryTU)
+      return true;
+
+    assert(Linkage == TargetLinkage);
+    // Instead of creating as alias to a linkonce_odr, replace all of the uses
+    // of the aliassee.
+    if (TargetLinkage == llvm::GlobalValue::LinkOnceODRLinkage) {
+      Replacements[MangledName] = Aliasee;
+      return false;
+    }
+  }
+
   // Create the alias with no name.
   llvm::GlobalAlias *Alias = 
     new llvm::GlobalAlias(AliasType, Linkage, "", Aliasee, &getModule());
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index c34f8332699..d7f33c9f1e5 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -172,6 +172,20 @@ void CodeGenModule::createCUDARuntime() {
   CUDARuntime = CreateNVCUDARuntime(*this);
 }
 
+void CodeGenModule::applyReplacements() {
+  for (ReplacementsTy::iterator I = Replacements.begin(),
+                                E = Replacements.end();
+       I != E; ++I) {
+    StringRef MangledName = I->first();
+    llvm::Constant *Replacement = I->second;
+    llvm::GlobalValue *Entry = GetGlobalValue(MangledName);
+    if (!Entry)
+      continue;
+    Entry->replaceAllUsesWith(Replacement);
+    Entry->eraseFromParent();
+  }
+}
+
 void CodeGenModule::checkAliases() {
   bool Error = false;
   for (std::vector<GlobalDecl>::iterator I = Aliases.begin(),
@@ -207,6 +221,7 @@ void CodeGenModule::checkAliases() {
 
 void CodeGenModule::Release() {
   EmitDeferred();
+  applyReplacements();
   checkAliases();
   EmitCXXGlobalInitFunc();
   EmitCXXGlobalDtorFunc();
diff --git a/clang/lib/CodeGen/CodeGenModule.h b/clang/lib/CodeGen/CodeGenModule.h
index 45a9e20a510..02b9ce6471b 100644
--- a/clang/lib/CodeGen/CodeGenModule.h
+++ b/clang/lib/CodeGen/CodeGenModule.h
@@ -279,6 +279,9 @@ class CodeGenModule : public CodeGenTypeCache {
   /// is defined once we get to the end of the of the translation unit.
   std::vector<GlobalDecl> Aliases;
 
+  typedef llvm::StringMap<llvm::TrackingVH<llvm::Constant> > ReplacementsTy;
+  ReplacementsTy Replacements;
+
   /// DeferredVTables - A queue of (optional) vtables to consider emitting.
   std::vector<const CXXRecordDecl*> DeferredVTables;
 
@@ -1082,6 +1085,9 @@ private:
   /// was deferred.
   void EmitDeferred();
 
+  /// Call replaceAllUsesWith on all pairs in Replacements.
+  void applyReplacements();
+
   void checkAliases();
 
   /// EmitDeferredVTables - Emit any vtables which we deferred and