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[DAGCombiner] Do a better job of ensuring we don't split elements when combining an extract_subvector of a bitcasted build_vector. 

llvm-svn: 312253
This commit is contained in:
Craig Topper 2017-08-31 17:02:22 +00:00
parent 8ac8df03c1
commit 7081f029f3
1 changed files with 7 additions and 4 deletions
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11
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -15173,14 +15173,17 @@ SDValue DAGCombiner::visitEXTRACT_SUBVECTOR(SDNode* N) {
if (V->getOpcode() == ISD::BUILD_VECTOR) {
if (auto *Idx = dyn_cast<ConstantSDNode>(N->getOperand(1))) {
EVT InVT = V->getValueType(0);
unsigned NumElems = NVT.getSizeInBits() / InVT.getScalarSizeInBits();
if (NumElems > 0) {
unsigned ExtractSize = NVT.getSizeInBits();
unsigned EltSize = InVT.getScalarSizeInBits();
// Only do this if we won't split any elements.
if (ExtractSize % EltSize == 0) {
unsigned NumElems = ExtractSize / EltSize;
EVT ExtractVT = EVT::getVectorVT(*DAG.getContext(),
InVT.getVectorElementType(), NumElems);
if (!LegalOperations ||
TLI.isOperationLegal(ISD::BUILD_VECTOR, ExtractVT)) {
unsigned IdxVal = Idx->getZExtValue() * NVT.getScalarSizeInBits() /
InVT.getScalarSizeInBits();
unsigned IdxVal = (Idx->getZExtValue() * NVT.getScalarSizeInBits()) /
EltSize;
// Extract the pieces from the original build_vector.
SDValue BuildVec = DAG.getBuildVector(ExtractVT, SDLoc(N),