3 files changed, 20 insertions, 25 deletions

diff --git a/lib/CodeGen/CodeGenModule.cpp b/lib/CodeGen/CodeGenModule.cpp
index 0526e7845c..9ae93599df 100644
--- a/lib/CodeGen/CodeGenModule.cpp
+++ b/lib/CodeGen/CodeGenModule.cpp
@@ -424,13 +424,6 @@ void CodeGenModule::EmitDeferred() {
     // Otherwise, emit the definition and move on to the next one.
     EmitGlobalDefinition(D);
   }
-
-  // Emit any tentative definitions, in reverse order so the most
-  // important (merged) decl will be seen and emitted first.
-  for (std::vector<const VarDecl*>::reverse_iterator 
-         it = TentativeDefinitions.rbegin(), ie = TentativeDefinitions.rend(); 
-       it != ie; ++it)
-    EmitTentativeDefinition(*it);
 }
 
 /// EmitAnnotateAttr - Generate the llvm::ConstantStruct which contains the 
@@ -502,6 +495,7 @@ bool CodeGenModule::MayDeferGeneration(const ValueDecl *Global) {
   
   const VarDecl *VD = cast<VarDecl>(Global);
   assert(VD->isFileVarDecl() && "Invalid decl");
+
   return VD->getStorageClass() == VarDecl::Static;
 }
 
@@ -520,16 +514,14 @@ void CodeGenModule::EmitGlobal(const ValueDecl *Global) {
     const VarDecl *VD = cast<VarDecl>(Global);
     assert(VD->isFileVarDecl() && "Cannot emit local var decl as global.");
 
-    // If this isn't a definition, defer code generation.
-    if (!VD->getInit()) {
-      // If this is a tentative definition, remember it so that we can
-      // emit the common definition if needed. It is important to
-      // defer tentative definitions, since they may have incomplete
-      // type.
-      if (!VD->hasExternalStorage())
-        TentativeDefinitions.push_back(VD);
+    // In C++, if this is marked "extern", defer code generation.
+    if (getLangOptions().CPlusPlus && 
+        VD->getStorageClass() == VarDecl::Extern && !VD->getInit())
+      return;
+
+    // In C, if this isn't a definition, defer code generation.
+    if (!getLangOptions().CPlusPlus && !VD->getInit())
       return;
-    }
   }
 
   // Defer code generation when possible if this is a static definition, inline
@@ -727,6 +719,9 @@ void CodeGenModule::EmitTentativeDefinition(const VarDecl *D) {
   // See if we have already defined this (as a variable), if so we do
   // not need to do anything.
   llvm::GlobalValue *GV = GlobalDeclMap[getMangledName(D)];
+  if (!GV && MayDeferGeneration(D)) // this variable was never referenced
+    return;
+
   if (llvm::GlobalVariable *Var = dyn_cast_or_null<llvm::GlobalVariable>(GV))
     if (Var->hasInitializer())
       return;
diff --git a/lib/CodeGen/CodeGenModule.h b/lib/CodeGen/CodeGenModule.h
index e7924fade5..21ef8da863 100644
--- a/lib/CodeGen/CodeGenModule.h
+++ b/lib/CodeGen/CodeGenModule.h
@@ -119,14 +119,6 @@ class CodeGenModule : public BlockModule {
   /// is done.
   std::vector<const ValueDecl*> DeferredDeclsToEmit;
 
-  /// TentativeDefinitions - A list of declarations which are
-  /// tentative definitions. Code generation for these must be
-  /// deferred because they are allowed to have incomplete type when
-  /// they are seen. This also allows us to avoid generating an extra
-  /// common definiton in situations where the tentative definition is
-  /// followed by an actual definition.
-  std::vector<const VarDecl*> TentativeDefinitions;
-  
   /// LLVMUsed - List of global values which are required to be
   /// present in the object file; bitcast to i8*. This is used for
   /// forcing visibility of symbols which may otherwise be optimized
@@ -339,6 +331,8 @@ public:
                                     CXXCtorType Type);
   const char *getMangledCXXDtorName(const CXXDestructorDecl *D, 
                                     CXXDtorType Type);
+
+  void EmitTentativeDefinition(const VarDecl *D);
   
   enum GVALinkage {
     GVA_Internal,
@@ -382,7 +376,6 @@ private:
   void EmitGlobalDefinition(const ValueDecl *D);
 
   void EmitGlobalFunctionDefinition(const FunctionDecl *D);
-  void EmitTentativeDefinition(const VarDecl *D);
   void EmitGlobalVarDefinition(const VarDecl *D);
   void EmitAliasDefinition(const ValueDecl *D);
   void EmitObjCPropertyImplementations(const ObjCImplementationDecl *D);
diff --git a/lib/CodeGen/ModuleBuilder.cpp b/lib/CodeGen/ModuleBuilder.cpp
index 896464ed5a..9b85df61da 100644
--- a/lib/CodeGen/ModuleBuilder.cpp
+++ b/lib/CodeGen/ModuleBuilder.cpp
@@ -83,6 +83,13 @@ namespace {
       if (Builder)
         Builder->Release();
     };
+
+    virtual void CompleteTentativeDefinition(VarDecl *D) {
+      if (Diags.hasErrorOccurred())
+        return;
+
+      Builder->EmitTentativeDefinition(D);
+    }
   };
 }