The change for PR9190 wasn't quite right. We need to avoid making the

transformation if we can't legally create a build vector of the correct
type. Check that we can make the transformation first, and add a TODO to
refactor this code with similar cases.

Fixes: PR9223 and rdar://9000350


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@125631 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 12 insertions, 2 deletions

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index f452d6a842..e213d722eb 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -1532,8 +1532,18 @@ SDValue DAGCombiner::visitSUB(SDNode *N) {
   }
 
   // fold (sub x, x) -> 0
-  if (N0 == N1)
-    return DAG.getConstant(0, N->getValueType(0), LegalTypes);
+  // FIXME: Refactor this and xor and other similar operations together.
+  if (N0 == N1) {
+    if (!VT.isVector()) {
+      return DAG.getConstant(0, VT);
+    } else if (!LegalOperations || TLI.isOperationLegal(ISD::BUILD_VECTOR, VT)){
+      // Produce a vector of zeros.
+      SDValue El = DAG.getConstant(0, VT.getVectorElementType());
+      std::vector<SDValue> Ops(VT.getVectorNumElements(), El);
+      return DAG.getNode(ISD::BUILD_VECTOR, N->getDebugLoc(), VT,
+                         &Ops[0], Ops.size());
+    }
+  }
   // fold (sub c1, c2) -> c1-c2
   if (N0C && N1C)
     return DAG.FoldConstantArithmetic(ISD::SUB, VT, N0C, N1C);