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Implement VECTOR_SHUFFLE canonicalizations during DAG combine. 

llvm-svn: 147525
This commit is contained in:
Craig Topper 2012-01-04 08:07:43 +00:00
parent 8d76cca3a2
commit 279c77b677
1 changed files with 50 additions and 2 deletions
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52
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -7254,15 +7254,63 @@ SDValue DAGCombiner::visitVECTOR_SHUFFLE(SDNode *N) {
unsigned NumElts = VT.getVectorNumElements();
SDValue N0 = N->getOperand(0);
SDValue N1 = N->getOperand(1);
assert(N0.getValueType().getVectorNumElements() == NumElts &&
"Vector shuffle must be normalized in DAG");
// FIXME: implement canonicalizations from DAG.getVectorShuffle()
// Canonicalize shuffle undef, undef -> undef
if (N0.getOpcode() == ISD::UNDEF && N1.getOpcode() == ISD::UNDEF)
return DAG.getUNDEF(VT);
ShuffleVectorSDNode *SVN = cast<ShuffleVectorSDNode>(N);
// Canonicalize shuffle v, v -> v, undef
if (N0 == N1) {
SmallVector<int, 8> NewMask;
for (unsigned i = 0; i != NumElts; ++i) {
int Idx = SVN->getMaskElt(i);
if (Idx >= (int)NumElts) Idx -= NumElts;
NewMask.push_back(Idx);
}
return DAG.getVectorShuffle(VT, N->getDebugLoc(), N0, DAG.getUNDEF(VT),
&NewMask[0]);
}
// Canonicalize shuffle undef, v -> v, undef. Commute the shuffle mask.
if (N0.getOpcode() == ISD::UNDEF) {
SmallVector<int, 8> NewMask;
for (unsigned i = 0; i != NumElts; ++i) {
int Idx = SVN->getMaskElt(i);
if (Idx < 0)
NewMask.push_back(Idx);
else if (Idx < (int)NumElts)
NewMask.push_back(Idx + NumElts);
else
NewMask.push_back(Idx - NumElts);
}
return DAG.getVectorShuffle(VT, N->getDebugLoc(), N1, DAG.getUNDEF(VT),
&NewMask[0]);
}
// Remove references to rhs if it is undef
if (N1.getOpcode() == ISD::UNDEF) {
bool Changed = false;
SmallVector<int, 8> NewMask;
for (unsigned i = 0; i != NumElts; ++i) {
int Idx = SVN->getMaskElt(i);
if (Idx >= (int)NumElts) {
Idx = -1;
Changed = true;
}
NewMask.push_back(Idx);
}
if (Changed)
return DAG.getVectorShuffle(VT, N->getDebugLoc(), N0, N1, &NewMask[0]);
}
// If it is a splat, check if the argument vector is another splat or a
// build_vector with all scalar elements the same.
ShuffleVectorSDNode *SVN = cast<ShuffleVectorSDNode>(N);
if (SVN->isSplat() && SVN->getSplatIndex() < (int)NumElts) {
SDNode *V = N0.getNode();