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[ARM][MVE] Add shuffle costs for LDn and STn instructions. #145304

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Merged
davemgreen merged 1 commit into from
Aug 14, 2025
Merged

[ARM][MVE] Add shuffle costs for LDn and STn instructions. #145304

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33 changes: 33 additions & 0 deletions llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1335,6 +1335,39 @@ InstructionCost ARMTTIImpl::getShuffleCost(TTI::ShuffleKind Kind,

if (!Mask.empty()) {
std::pair<InstructionCost, MVT> LT = getTypeLegalizationCost(SrcTy);
// Check for LD2/LD4 instructions, which are represented in llvm IR as
// deinterleaving-shuffle(load). The shuffle cost could potentially be
// free, but we model it with a cost of LT.first so that LD2/LD4 have a
// higher cost than just the load.
if (Args.size() >= 1 && isa<LoadInst>(Args[0]) &&
(LT.second.getScalarSizeInBits() == 8 ||
LT.second.getScalarSizeInBits() == 16 ||
LT.second.getScalarSizeInBits() == 32) &&
LT.second.getSizeInBits() == 128 &&
((TLI->getMaxSupportedInterleaveFactor() >= 2 &&
ShuffleVectorInst::isDeInterleaveMaskOfFactor(Mask, 2)) ||
(TLI->getMaxSupportedInterleaveFactor() == 4 &&
ShuffleVectorInst::isDeInterleaveMaskOfFactor(Mask, 4))))
return ST->getMVEVectorCostFactor(CostKind) *
std::max<InstructionCost>(1, LT.first / 4);

// Check for ST2/ST4 instructions, which are represented in llvm IR as
// store(interleaving-shuffle). The shuffle cost could potentially be
// free, but we model it with a cost of LT.first so that ST2/ST4 have a
// higher cost than just the store.
if (CxtI && CxtI->hasOneUse() && isa<StoreInst>(*CxtI->user_begin()) &&
(LT.second.getScalarSizeInBits() == 8 ||
LT.second.getScalarSizeInBits() == 16 ||
LT.second.getScalarSizeInBits() == 32) &&
LT.second.getSizeInBits() == 128 &&
((TLI->getMaxSupportedInterleaveFactor() >= 2 &&
ShuffleVectorInst::isInterleaveMask(
Mask, 2, SrcTy->getElementCount().getKnownMinValue() * 2)) ||
(TLI->getMaxSupportedInterleaveFactor() == 4 &&
ShuffleVectorInst::isInterleaveMask(
Mask, 4, SrcTy->getElementCount().getKnownMinValue() * 2))))
return ST->getMVEVectorCostFactor(CostKind) * LT.first;

if (LT.second.isVector() &&
Mask.size() <= LT.second.getVectorNumElements() &&
(isVREVMask(Mask, LT.second, 16) || isVREVMask(Mask, LT.second, 32) ||
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