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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.

llvm-svn: 27472
This commit is contained in:
Evan Cheng 2006-04-06 23:20:43 +00:00
parent 1596a1b276
commit 613996c55e
1 changed files with 6 additions and 3 deletions
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9
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -2673,16 +2673,19 @@ SDOperand DAGCombiner::visitVECTOR_SHUFFLE(SDNode *N) {
// 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(),