Index: tools/clang/lib/CodeGen/ItaniumCXXABI.cpp
===================================================================
--- tools/clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ tools/clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -2837,9 +2837,6 @@
       new llvm::GlobalVariable(M, Init->getType(),
                                /*Constant=*/true, Linkage, Init, Name);
 
-  if (CGM.supportsCOMDAT() && GV->isWeakForLinker())
-    GV->setComdat(M.getOrInsertComdat(GV->getName()));
-
   // If there's already an old global variable, replace it with the new one.
   if (OldGV) {
     GV->takeName(OldGV);
@@ -2849,6 +2846,9 @@
     OldGV->eraseFromParent();
   }
 
+  if (CGM.supportsCOMDAT() && GV->isWeakForLinker())
+    GV->setComdat(M.getOrInsertComdat(GV->getName()));
+
   // The Itanium ABI specifies that type_info objects must be globally
   // unique, with one exception: if the type is an incomplete class
   // type or a (possibly indirect) pointer to one.  That exception
Index: tools/clang/test/CodeGenCXX/vtable-key-function-win-comdat.cpp
===================================================================
--- tools/clang/test/CodeGenCXX/vtable-key-function-win-comdat.cpp
+++ tools/clang/test/CodeGenCXX/vtable-key-function-win-comdat.cpp
@@ -0,0 +1,18 @@
+// RUN: %clang_cc1 %s -triple=x86_64-pc-windows-gnu -emit-llvm -o - | FileCheck %s
+
+namespace std { class type_info; }
+extern void use(const std::type_info &rtti);
+
+struct Test1a {
+  Test1a();
+  virtual void foo();
+  virtual void bar();
+};
+
+// V-table needs to be defined weakly.
+Test1a::Test1a() { use(typeid(Test1a)); }
+// This defines the key function.
+inline void Test1a::foo() {}
+
+// CHECK:     $_ZTS6Test1a = comdat any
+// CHECK-NOT: $_ZTI6Test1a.1 = comdat any