Index: include/clang/AST/Type.h
===================================================================
--- include/clang/AST/Type.h
+++ include/clang/AST/Type.h
@@ -709,6 +709,8 @@
     return QualType::isConstant(*this, Ctx);
   }
 
+  bool isWriteOnce(ASTContext &Ctx);
+
   /// \brief Determine whether this is a Plain Old Data (POD) type (C++ 3.9p10).
   bool isPODType(ASTContext &Context) const;
 
Index: lib/AST/Type.cpp
===================================================================
--- lib/AST/Type.cpp
+++ lib/AST/Type.cpp
@@ -1919,6 +1919,19 @@
   }
 }
 
+bool QualType::isWriteOnce(ASTContext &Context) {
+
+	if (!Context.getLangOpts().CPlusPlus ||
+			!isConstant(Context) || getTypePtr()->isReferenceType())
+    return false;
+
+  if (const CXXRecordDecl *Record
+        = Context.getBaseElementType(*this)->getAsCXXRecordDecl())
+  	return !Record->hasMutableFields();
+
+  return true;
+}
+
 bool QualType::isPODType(ASTContext &Context) const {
   // C++11 has a more relaxed definition of POD.
   if (Context.getLangOpts().CPlusPlus11)
Index: lib/CodeGen/CGDecl.cpp
===================================================================
--- lib/CodeGen/CGDecl.cpp
+++ lib/CodeGen/CGDecl.cpp
@@ -949,7 +949,8 @@
           // to this variable. Set it to zero to indicate that NRVO was not
           // applied.
           llvm::Value *Zero = Builder.getFalse();
-          llvm::Value *NRVOFlag = CreateTempAlloca(Zero->getType(), "nrvo");
+          llvm::AllocaInst *NRVOFlag = CreateTempAlloca(Zero->getType(), "nrvo");
+          NRVOFlag->setWriteOnce(Ty.isWriteOnce(getContext()));
           EnsureInsertPoint();
           Builder.CreateStore(Zero, NRVOFlag);
 
@@ -964,6 +965,7 @@
 
       llvm::AllocaInst *Alloc = CreateTempAlloca(LTy);
       Alloc->setName(D.getName());
+      Alloc->setWriteOnce(Ty.isWriteOnce(getContext()));
 
       CharUnits allocaAlignment = alignment;
       if (isByRef)
@@ -986,7 +988,8 @@
 
     if (!DidCallStackSave) {
       // Save the stack.
-      llvm::Value *Stack = CreateTempAlloca(Int8PtrTy, "saved_stack");
+      llvm::AllocaInst *Stack = CreateTempAlloca(Int8PtrTy, "saved_stack");
+      Stack->setWriteOnce(Ty.isWriteOnce(getContext()));
 
       llvm::Value *F = CGM.getIntrinsic(llvm::Intrinsic::stacksave);
       llvm::Value *V = Builder.CreateCall(F);
@@ -1009,6 +1012,7 @@
     // Allocate memory for the array.
     llvm::AllocaInst *vla = Builder.CreateAlloca(llvmTy, elementCount, "vla");
     vla->setAlignment(alignment.getQuantity());
+    vla->setWriteOnce(Ty.isWriteOnce(getContext()));
 
     DeclPtr = vla;
   }
@@ -1678,6 +1682,7 @@
         llvm::AllocaInst *Alloc = CreateTempAlloca(ConvertTypeForMem(Ty),
                                                    D.getName() + ".addr");
         Alloc->setAlignment(getContext().getDeclAlign(&D).getQuantity());
+        Alloc->setWriteOnce(Ty.isWriteOnce(getContext()));
         LValue lv = MakeAddrLValue(Alloc, Ty, getContext().getDeclAlign(&D));
         EmitStoreOfScalar(Arg, lv, /* isInitialization */ true);
         LocalAddr = Builder.CreateLoad(Alloc);
@@ -1721,6 +1726,7 @@
     llvm::AllocaInst *Alloc = CreateTempAlloca(ConvertTypeForMem(Ty),
                                                D.getName() + ".addr");
     Alloc->setAlignment(Align.getQuantity());
+    Alloc->setWriteOnce(Ty.isWriteOnce(getContext()));
     DeclPtr = Alloc;
     DoStore = true;
   }
Index: lib/CodeGen/CodeGenModule.cpp
===================================================================
--- lib/CodeGen/CodeGenModule.cpp
+++ lib/CodeGen/CodeGenModule.cpp
@@ -1705,6 +1705,7 @@
 /// will not be considered. The caller will need to verify that the object is
 /// not written to during its construction.
 bool CodeGenModule::isTypeConstant(QualType Ty, bool ExcludeCtor) {
+
   if (!Ty.isConstant(Context) && !Ty->isReferenceType())
     return false;
 
@@ -2077,6 +2078,9 @@
   GV->setConstant(!NeedsGlobalCtor && !NeedsGlobalDtor &&
                   isTypeConstant(D->getType(), true));
 
+  // Mark const variables 'writeonce', if global is not 'constant'.
+  GV->setWriteOnce(!GV->isConstant() && D->getType().isWriteOnce(Context));
+
   // If it is in a read-only section, mark it 'constant'.
   if (const SectionAttr *SA = D->getAttr<SectionAttr>()) {
     const ASTContext::SectionInfo &SI = Context.SectionInfos[SA->getName()];