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[DAG] visitVECTOR_SHUFFLE - move shuffle legality check into MergeInnerShuffle lamda. NFCI. 

This is going to be necessary for a future reuse of MergeInnerShuffle
This commit is contained in:
Simon Pilgrim 2021-02-08 13:46:31 +00:00
parent eb8c27c60c
commit c5c690a835
1 changed files with 25 additions and 21 deletions
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46
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -20836,10 +20836,10 @@ SDValue DAGCombiner::visitVECTOR_SHUFFLE(SDNode *N) {
// Compute the combined shuffle mask for a shuffle with SV0 as the first
// operand, and SV1 as the second operand.
// i.e. Merge SVN(OtherSVN, N1) -> shuffle(SV0, SV1, Mask).
auto MergeInnerShuffle = [NumElts](ShuffleVectorSDNode *SVN,
ShuffleVectorSDNode *OtherSVN, SDValue N1,
SDValue &SV0, SDValue &SV1,
SmallVectorImpl<int> &Mask) -> bool {
auto MergeInnerShuffle =
[NumElts, &VT](ShuffleVectorSDNode *SVN, ShuffleVectorSDNode *OtherSVN,
SDValue N1, const TargetLowering &TLI, SDValue &SV0,
SDValue &SV1, SmallVectorImpl<int> &Mask) -> bool {
// Don't try to fold splats; they're likely to simplify somehow, or they
// might be free.
if (OtherSVN->isSplat())
@ -20926,7 +20926,23 @@ SDValue DAGCombiner::visitVECTOR_SHUFFLE(SDNode *N) {
// Bail out if we cannot convert the shuffle pair into a single shuffle.
return false;
}
return true;
if (llvm::all_of(Mask, [](int M) { return M < 0; }))
return true;
// Avoid introducing shuffles with illegal mask.
// shuffle(shuffle(A, B, M0), C, M1) -> shuffle(A, B, M2)
// shuffle(shuffle(A, B, M0), C, M1) -> shuffle(A, C, M2)
// shuffle(shuffle(A, B, M0), C, M1) -> shuffle(B, C, M2)
// shuffle(shuffle(A, B, M0), C, M1) -> shuffle(B, A, M2)
// shuffle(shuffle(A, B, M0), C, M1) -> shuffle(C, A, M2)
// shuffle(shuffle(A, B, M0), C, M1) -> shuffle(C, B, M2)
if (TLI.isShuffleMaskLegal(Mask, VT))
return true;
std::swap(SV0, SV1);
ShuffleVectorSDNode::commuteMask(Mask);
return TLI.isShuffleMaskLegal(Mask, VT);
};
// Try to fold according to rules:
@ -20937,33 +20953,21 @@ SDValue DAGCombiner::visitVECTOR_SHUFFLE(SDNode *N) {
// Only fold if this shuffle is the only user of the other shuffle.
if (N0.getOpcode() == ISD::VECTOR_SHUFFLE && N->isOnlyUserOf(N0.getNode()) &&
Level < AfterLegalizeDAG && TLI.isTypeLegal(VT)) {
ShuffleVectorSDNode *OtherSV = cast<ShuffleVectorSDNode>(N0);
// The incoming shuffle must be of the same type as the result of the
// current shuffle.
auto *OtherSV = cast<ShuffleVectorSDNode>(N0);
assert(OtherSV->getOperand(0).getValueType() == VT &&
"Shuffle types don't match");
SDValue SV0, SV1;
SmallVector<int, 4> Mask;
if (MergeInnerShuffle(SVN, OtherSV, N1, SV0, SV1, Mask)) {
if (MergeInnerShuffle(SVN, OtherSV, N1, TLI, SV0, SV1, Mask)) {
// Check if all indices in Mask are Undef. In case, propagate Undef.
if (llvm::all_of(Mask, [](int M) { return M < 0; }))
return DAG.getUNDEF(VT);
if (!SV0.getNode())
SV0 = DAG.getUNDEF(VT);
if (!SV1.getNode())
SV1 = DAG.getUNDEF(VT);
// Avoid introducing shuffles with illegal mask.
// shuffle(shuffle(A, B, M0), C, M1) -> shuffle(A, B, M2)
// shuffle(shuffle(A, B, M0), C, M1) -> shuffle(A, C, M2)
// shuffle(shuffle(A, B, M0), C, M1) -> shuffle(B, C, M2)
// shuffle(shuffle(A, B, M0), C, M1) -> shuffle(B, A, M2)
// shuffle(shuffle(A, B, M0), C, M1) -> shuffle(C, A, M2)
// shuffle(shuffle(A, B, M0), C, M1) -> shuffle(C, B, M2)
return TLI.buildLegalVectorShuffle(VT, SDLoc(N), SV0, SV1, Mask, DAG);
return DAG.getVectorShuffle(VT, SDLoc(N), SV0 ? SV0 : DAG.getUNDEF(VT),
SV1 ? SV1 : DAG.getUNDEF(VT), Mask);
}
}