2 files changed, 43 insertions, 0 deletions
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 96ae437ff46..d0f34dddca3 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -37,6 +37,7 @@
 #include "clang/Basic/TargetInfo.h"
 #include "clang/Basic/Version.h"
 #include "clang/Frontend/CodeGenOptions.h"
+#include "clang/Sema/SemaDiagnostic.h"
 #include "llvm/ADT/APSInt.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/IR/CallingConv.h"
@@ -171,8 +172,42 @@ void CodeGenModule::createCUDARuntime() {
   CUDARuntime = CreateNVCUDARuntime(*this);
 }
 
+void CodeGenModule::checkAliases() {
+  bool Error = false;
+  for (std::vector<GlobalDecl>::iterator I = Aliases.begin(),
+         E = Aliases.end(); I != E; ++I) {
+    const GlobalDecl &GD = *I;
+    const ValueDecl *D = cast<ValueDecl>(GD.getDecl());
+    const AliasAttr *AA = D->getAttr<AliasAttr>();
+    StringRef MangledName = getMangledName(GD);
+    llvm::GlobalValue *Entry = GetGlobalValue(MangledName);
+    llvm::GlobalAlias *Alias = cast<llvm::GlobalAlias>(Entry);
+    llvm::GlobalValue *GV = Alias->getAliasedGlobal();
+    if (GV->isDeclaration()) {
+      Error = true;
+      getDiags().Report(AA->getLocation(), diag::err_alias_to_undefined);
+    } else if (!Alias->resolveAliasedGlobal(/*stopOnWeak*/ false)) {
+      Error = true;
+      getDiags().Report(AA->getLocation(), diag::err_cyclic_alias);
+    }
+  }
+  if (!Error)
+    return;
+
+  for (std::vector<GlobalDecl>::iterator I = Aliases.begin(),
+         E = Aliases.end(); I != E; ++I) {
+    const GlobalDecl &GD = *I;
+    StringRef MangledName = getMangledName(GD);
+    llvm::GlobalValue *Entry = GetGlobalValue(MangledName);
+    llvm::GlobalAlias *Alias = cast<llvm::GlobalAlias>(Entry);
+    Alias->replaceAllUsesWith(llvm::UndefValue::get(Alias->getType()));
+    Alias->eraseFromParent();
+  }
+}
+
 void CodeGenModule::Release() {
   EmitDeferred();
+  checkAliases();
   EmitCXXGlobalInitFunc();
   EmitCXXGlobalDtorFunc();
   EmitCXXThreadLocalInitFunc();
@@ -2088,6 +2123,8 @@ void CodeGenModule::EmitAliasDefinition(GlobalDecl GD) {
   if (Entry && !Entry->isDeclaration())
     return;
 
+  Aliases.push_back(GD);
+
   llvm::Type *DeclTy = getTypes().ConvertTypeForMem(D->getType());
 
   // Create a reference to the named value.  This ensures that it is emitted
diff --git a/clang/lib/CodeGen/CodeGenModule.h b/clang/lib/CodeGen/CodeGenModule.h
index 066009ca7df..25aaae61e48 100644
--- a/clang/lib/CodeGen/CodeGenModule.h
+++ b/clang/lib/CodeGen/CodeGenModule.h
@@ -275,6 +275,10 @@ class CodeGenModule : public CodeGenTypeCache {
   /// is done.
   std::vector<GlobalDecl> DeferredDeclsToEmit;
 
+  /// List of alias we have emitted. Used to make sure that what they point to
+  /// is defined once we get to the end of the of the translation unit.
+  std::vector<GlobalDecl> Aliases;
+
   /// DeferredVTables - A queue of (optional) vtables to consider emitting.
   std::vector<const CXXRecordDecl*> DeferredVTables;
 
@@ -1077,6 +1081,8 @@ private:
   /// was deferred.
   void EmitDeferred();
 
+  void checkAliases();
+
   /// EmitDeferredVTables - Emit any vtables which we deferred and
   /// still have a use for.
   void EmitDeferredVTables();