diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 963a1fe..1b00855 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -1103,6 +1103,10 @@
   
   // fold (sub x, x) -> 0
   if (N0 == N1)
+    if (ISD::isBuildVectorAllZeros(N0.Val))
+      // Zero vectors might be normalized to a particular vector type to ensure
+      // they are CSE'd. Return it as it is.
+      return N0;
     return DAG.getConstant(0, N->getValueType(0));
   // fold (sub c1, c2) -> c1-c2
   if (N0C && N1C)