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[RISCV][TTI] Scale the cost of the sext/zext with LMUL #86617

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Merged
merged 1 commit into from
Mar 27, 2024
Merged

[RISCV][TTI] Scale the cost of the sext/zext with LMUL #86617

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20 changes: 15 additions & 5 deletions llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -906,23 +906,33 @@ InstructionCost RISCVTTIImpl::getCastInstrCost(unsigned Opcode, Type *Dst,
if (!IsVectorType || !IsTypeLegal)
return BaseT::getCastInstrCost(Opcode, Dst, Src, CCH, CostKind, I);

std::pair<InstructionCost, MVT> DstLT = getTypeLegalizationCost(Dst);

int ISD = TLI->InstructionOpcodeToISD(Opcode);
assert(ISD && "Invalid opcode");

// FIXME: Need to consider vsetvli and lmul.
int PowDiff = (int)Log2_32(Dst->getScalarSizeInBits()) -
(int)Log2_32(Src->getScalarSizeInBits());
switch (ISD) {
case ISD::SIGN_EXTEND:
case ISD::ZERO_EXTEND:
if (Src->getScalarSizeInBits() == 1) {
case ISD::ZERO_EXTEND: {
const unsigned SrcEltSize = Src->getScalarSizeInBits();
if (SrcEltSize == 1) {
// We do not use vsext/vzext to extend from mask vector.
// Instead we use the following instructions to extend from mask vector:
// vmv.v.i v8, 0
// vmerge.vim v8, v8, -1, v0
return 2;
return getRISCVInstructionCost({RISCV::VMV_V_I, RISCV::VMERGE_VIM},
DstLT.second, CostKind);
}
return 1;
if (PowDiff > 3)
return BaseT::getCastInstrCost(Opcode, Dst, Src, CCH, CostKind, I);
unsigned SExtOp[] = {RISCV::VSEXT_VF2, RISCV::VSEXT_VF4, RISCV::VSEXT_VF8};
unsigned ZExtOp[] = {RISCV::VZEXT_VF2, RISCV::VZEXT_VF4, RISCV::VZEXT_VF8};
unsigned Op =
(ISD == ISD::SIGN_EXTEND) ? SExtOp[PowDiff - 1] : ZExtOp[PowDiff - 1];
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I guess something is calling this with a sign/zero extend to the same type, i.e. PowDiff == 0? Probably best just to defensively check for it then

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@arcbbb arcbbb Mar 27, 2024 •
edited
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Yes, this failure showed that loop vectorizer getReductionPatternCost would call this with extend to the same type.
Will recommit with an additional check on this.

return getRISCVInstructionCost(Op, DstLT.second, CostKind);
}
case ISD::TRUNCATE:
if (Dst->getScalarSizeInBits() == 1) {
// We do not use several vncvt to truncate to mask vector. So we could
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