Index: lib/CodeGen/MicrosoftCXXABI.cpp
===================================================================
--- lib/CodeGen/MicrosoftCXXABI.cpp
+++ lib/CodeGen/MicrosoftCXXABI.cpp
@@ -1196,15 +1196,15 @@
   unsigned AS = getThisAddress(CGF).getAddressSpace();
   llvm::Value *Int8This = nullptr;  // Initialize lazily.
 
-  for (VBOffsets::const_iterator I = VBaseMap.begin(), E = VBaseMap.end();
-        I != E; ++I) {
-    if (!I->second.hasVtorDisp())
+  for (const CXXBaseSpecifier &S : RD->vbases()) {
+    const CXXRecordDecl *VBase = S.getType()->getAsCXXRecordDecl();
+    if (!VBaseMap.find(VBase)->second.hasVtorDisp())
       continue;
 
     llvm::Value *VBaseOffset =
-        GetVirtualBaseClassOffset(CGF, getThisAddress(CGF), RD, I->first);
+        GetVirtualBaseClassOffset(CGF, getThisAddress(CGF), RD, VBase);
     uint64_t ConstantVBaseOffset =
-        Layout.getVBaseClassOffset(I->first).getQuantity();
+        Layout.getVBaseClassOffset(VBase).getQuantity();
 
     // vtorDisp_for_vbase = vbptr[vbase_idx] - offsetof(RD, vbase).
     llvm::Value *VtorDispValue = Builder.CreateSub(