1. If both vector operands of a vector_shuffle are undef, turn it into an undef.
2. A shuffle mask element can also be an undef.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@27472 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index a5925ad..d1dbd9a 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -2673,16 +2673,19 @@
// If the LHS and the RHS are the same node, turn the RHS into an undef.
if (N->getOperand(0) == N->getOperand(1)) {
+ if (N->getOperand(0).getOpcode() == ISD::UNDEF)
+ return DAG.getNode(ISD::UNDEF, N->getValueType(0));
// Check the SHUFFLE mask, mapping any inputs from the 2nd operand into the
// first operand.
std::vector<SDOperand> MappedOps;
for (unsigned i = 0, e = ShufMask.getNumOperands(); i != e; ++i) {
- if (cast<ConstantSDNode>(ShufMask.getOperand(i))->getValue() >= NumElts) {
+ if (ShufMask.getOperand(i).getOpcode() == ISD::UNDEF ||
+ cast<ConstantSDNode>(ShufMask.getOperand(i))->getValue() < NumElts) {
+ MappedOps.push_back(ShufMask.getOperand(i));
+ } else {
unsigned NewIdx =
cast<ConstantSDNode>(ShufMask.getOperand(i))->getValue() - NumElts;
MappedOps.push_back(DAG.getConstant(NewIdx, MVT::i32));
- } else {
- MappedOps.push_back(ShufMask.getOperand(i));
}
}
ShufMask = DAG.getNode(ISD::BUILD_VECTOR, ShufMask.getValueType(),