diff --git a/llvm/include/llvm/CodeGen/DIE.h b/llvm/include/llvm/CodeGen/DIE.h
--- a/llvm/include/llvm/CodeGen/DIE.h
+++ b/llvm/include/llvm/CodeGen/DIE.h
@@ -464,6 +464,8 @@
   }
 
   DIEValue &operator=(const DIEValue &X) {
+    if (&Val == &X.Val)
+      return *this;
     destroyVal();
     Ty = X.Ty;
     Attribute = X.Attribute;