[DAG] add splat vector support for 'xor' in SimplifyDemandedBits

This allows forming more 'not' ops, so we get improvements for ISAs that have and-not.

Follow-up to:
https://reviews.llvm.org/rL300725

llvm-svn: 300763

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index c9b438edabf..91230b93423 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -715,7 +715,7 @@ bool TargetLowering::SimplifyDemandedBits(SDValue Op,
     // If the RHS is a constant, see if we can simplify it.
     // for XOR, we prefer to force bits to 1 if they will make a -1.
     // If we can't force bits, try to shrink the constant.
-    if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
+    if (ConstantSDNode *C = isConstOrConstSplat(Op.getOperand(1))) {
       APInt Expanded = C->getAPIntValue() | (~NewMask);
       // If we can expand it to have all bits set, do it.
       if (Expanded.isAllOnesValue()) {