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[RISCV] Use DAG.getElementCount in lowerEXTRACT_SUBVECTOR. NFCI #81698

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Merged
merged 1 commit into from
Feb 19, 2024
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[RISCV] Use DAG.getElementCount in lowerEXTRACT_SUBVECTOR. NFCI #81698

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25 changes: 12 additions & 13 deletions llvm/lib/Target/RISCV/RISCVISelLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -9776,27 +9776,32 @@ SDValue RISCVTargetLowering::lowerEXTRACT_SUBVECTOR(SDValue Op,
if (SubVecVT.isFixedLengthVector())
ContainerSubVecVT = getContainerForFixedLengthVector(SubVecVT);

unsigned SubRegIdx, RemIdx;
// extract_subvector scales the index by vscale is the subvector is scalable,
unsigned SubRegIdx;
ElementCount RemIdx;
// extract_subvector scales the index by vscale if the subvector is scalable,
// and decomposeSubvectorInsertExtractToSubRegs takes this into account. So if
// we have a fixed length subvector, we need to adjust the index by 1/vscale.
if (SubVecVT.isFixedLengthVector()) {
assert(MinVLen == MaxVLen);
unsigned Vscale = MinVLen / RISCV::RVVBitsPerBlock;
std::tie(SubRegIdx, RemIdx) =
auto Decompose =
RISCVTargetLowering::decomposeSubvectorInsertExtractToSubRegs(
VecVT, ContainerSubVecVT, OrigIdx / Vscale, TRI);
RemIdx = (RemIdx * Vscale) + (OrigIdx % Vscale);
SubRegIdx = Decompose.first;
RemIdx = ElementCount::getFixed((Decompose.second * Vscale) +
(OrigIdx % Vscale));
} else {
std::tie(SubRegIdx, RemIdx) =
auto Decompose =
RISCVTargetLowering::decomposeSubvectorInsertExtractToSubRegs(
VecVT, ContainerSubVecVT, OrigIdx, TRI);
SubRegIdx = Decompose.first;
RemIdx = ElementCount::getScalable(Decompose.second);
}

// If the Idx has been completely eliminated then this is a subvector extract
// which naturally aligns to a vector register. These can easily be handled
// using subregister manipulation.
if (RemIdx == 0) {
if (RemIdx.isZero()) {
if (SubVecVT.isFixedLengthVector()) {
Vec = DAG.getTargetExtractSubreg(SubRegIdx, DL, ContainerSubVecVT, Vec);
return convertFromScalableVector(SubVecVT, Vec, DAG, Subtarget);
Expand All @@ -9823,13 +9828,7 @@ SDValue RISCVTargetLowering::lowerEXTRACT_SUBVECTOR(SDValue Op,

// Slide this vector register down by the desired number of elements in order
// to place the desired subvector starting at element 0.
SDValue SlidedownAmt;
if (SubVecVT.isFixedLengthVector())
SlidedownAmt = DAG.getConstant(RemIdx, DL, Subtarget.getXLenVT());
else
SlidedownAmt =
DAG.getVScale(DL, XLenVT, APInt(XLenVT.getSizeInBits(), RemIdx));

SDValue SlidedownAmt = DAG.getElementCount(DL, XLenVT, RemIdx);
auto [Mask, VL] = getDefaultScalableVLOps(InterSubVT, DL, DAG, Subtarget);
if (SubVecVT.isFixedLengthVector())
VL = getVLOp(SubVecVT.getVectorNumElements(), InterSubVT, DL, DAG,
Expand Down