When performing return slot optimization, remember to inform memdep when we're removing the memcpy.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47364 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Scalar/GVN.cpp

@@ -1139,6 +1139,7 @@ bool GVN::performReturnSlotOptzn(MemCpyInst* cpy, CallInst* C,
   MD.dropInstruction(C);
   
   // Remove the memcpy
+  MD.removeInstruction(cpy);
   toErase.push_back(cpy);
   
   return true;