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[GISel][SDAG] Avoid push_back in loops for some shuffle mask handling. #119434

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Merged
merged 2 commits into from
Dec 11, 2024
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[GISel][SDAG] Avoid push_back in loops for some shuffle mask handling. #119434

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[GISel][SDAG] Avoid push_back in loops for some shuffle mask handling.
topperc Dec 10, 2024
2c9d19f
fixup! Address review comments.
topperc Dec 10, 2024
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11 changes: 4 additions & 7 deletions llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -6173,8 +6173,7 @@ LegalizerHelper::equalizeVectorShuffleLengths(MachineInstr &MI) {
// Extend mask to match new destination vector size with
// undef values.
SmallVector<int, 16> NewMask(Mask);
for (unsigned I = MaskNumElts; I < SrcNumElts; ++I)
NewMask.push_back(-1);
NewMask.resize(SrcNumElts, -1);
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@aemerson aemerson Dec 10, 2024

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Use the constructor variant as you did in moreElementsVectorShuffle()?

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@topperc topperc Dec 10, 2024

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We're already using the constructor to copy the first part of the Mask. We could do

SmallVector<int, 16> NewMask(SrcNumElts, -1);
std::copy(NewMask.begin(), Mask.begin(), Mask.end())

Then we'd have the correct size at the start.


moreElementsVectorDst(MI, SrcTy, 0);
MIRBuilder.setInstrAndDebugLoc(MI);
Expand Down Expand Up @@ -6254,16 +6253,14 @@ LegalizerHelper::moreElementsVectorShuffle(MachineInstr &MI,
moreElementsVectorSrc(MI, MoreTy, 2);

// Adjust mask based on new input vector length.
SmallVector<int, 16> NewMask;
SmallVector<int, 16> NewMask(WidenNumElts, -1);
for (unsigned I = 0; I != NumElts; ++I) {
int Idx = Mask[I];
if (Idx < static_cast<int>(NumElts))
NewMask.push_back(Idx);
NewMask[I] = Idx;
else
NewMask.push_back(Idx - NumElts + WidenNumElts);
NewMask[I] = Idx - NumElts + WidenNumElts;
}
for (unsigned I = NumElts; I != WidenNumElts; ++I)
NewMask.push_back(-1);
moreElementsVectorDst(MI, MoreTy, 0);
MIRBuilder.setInstrAndDebugLoc(MI);
MIRBuilder.buildShuffleVector(MI.getOperand(0).getReg(),
Expand Down
17 changes: 6 additions & 11 deletions llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
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Expand Up @@ -6421,16 +6421,14 @@ SDValue DAGTypeLegalizer::WidenVecRes_VECTOR_SHUFFLE(ShuffleVectorSDNode *N) {
SDValue InOp2 = GetWidenedVector(N->getOperand(1));

// Adjust mask based on new input vector length.
SmallVector<int, 16> NewMask;
SmallVector<int, 16> NewMask(WidenNumElts, -1);
for (unsigned i = 0; i != NumElts; ++i) {
int Idx = N->getMaskElt(i);
if (Idx < (int)NumElts)
NewMask.push_back(Idx);
NewMask[i] = Idx;
else
NewMask.push_back(Idx - NumElts + WidenNumElts);
NewMask[i] = Idx - NumElts + WidenNumElts;
}
for (unsigned i = NumElts; i != WidenNumElts; ++i)
NewMask.push_back(-1);
return DAG.getVectorShuffle(WidenVT, dl, InOp1, InOp2, NewMask);
}

Expand Down Expand Up @@ -6478,12 +6476,9 @@ SDValue DAGTypeLegalizer::WidenVecRes_VECTOR_REVERSE(SDNode *N) {

// Use VECTOR_SHUFFLE to combine new vector from 'ReverseVal' for
// fixed-vectors.
SmallVector<int, 16> Mask;
for (unsigned i = 0; i != VTNumElts; ++i) {
Mask.push_back(IdxVal + i);
}
for (unsigned i = VTNumElts; i != WidenNumElts; ++i)
Mask.push_back(-1);
SmallVector<int, 16> Mask(VTNumElts, -1);
for (unsigned i = 0; i != VTNumElts; ++i)
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@RKSimon RKSimon Dec 10, 2024

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Use std::iota?

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@topperc topperc Dec 10, 2024

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Thanks.

I messed up the size here. I should have used WidenNumElts in the constructor. Need to see why nothing failed.

Mask[i] = IdxVal + i;

return DAG.getVectorShuffle(WidenVT, dl, ReverseVal, DAG.getUNDEF(WidenVT),
Mask);
Expand Down
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