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[AArch64] Sub, add, and icmp should have the fact they can be negated in the cost #142844

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[AArch64] Sub, add, and icmp should have the fact they can be negated in the cost #142844

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35 changes: 28 additions & 7 deletions llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -413,6 +413,20 @@ AArch64TTIImpl::getIntImmCost(const APInt &Imm, Type *Ty,
return std::max<InstructionCost>(1, Cost);
}

static bool isLegalArithImmed(uint64_t C) {
// Matches AArch64DAGToDAGISel::SelectArithImmed().
bool IsLegal = (C >> 12 == 0) || ((C & 0xFFFULL) == 0 && C >> 24 == 0);
LLVM_DEBUG(dbgs() << "Is imm " << C
<< " legal: " << (IsLegal ? "yes\n" : "no\n"));
return IsLegal;
}

static bool isLegalCmpImmed(APInt C) {
// Works for negative immediates too, as it can be written as an ADDS
// instruction with a negated immediate.
return isLegalArithImmed(C.abs().getZExtValue());
}

InstructionCost AArch64TTIImpl::getIntImmCostInst(unsigned Opcode, unsigned Idx,
const APInt &Imm, Type *Ty,
TTI::TargetCostKind CostKind,
Expand Down Expand Up @@ -473,10 +487,19 @@ InstructionCost AArch64TTIImpl::getIntImmCostInst(unsigned Opcode, unsigned Idx,

if (Idx == ImmIdx) {
int NumConstants = (BitSize + 63) / 64;
InstructionCost Cost = AArch64TTIImpl::getIntImmCost(Imm, Ty, CostKind);
return (Cost <= NumConstants * TTI::TCC_Basic)
? static_cast<int>(TTI::TCC_Free)
: Cost;
InstructionCost Cost;
if ((Opcode == Instruction::Add || Opcode == Instruction::Sub ||
Opcode == Instruction::ICmp) &&
BitSize <= 64) {
// Add/Sub/ICmp immediates can be flipped.
// Also they have different requirements as to fitting in an immediate
// than others.
if (isLegalCmpImmed(Imm))
return TTI::TCC_Free;
Cost = AArch64TTIImpl::getIntImmCost(Imm.abs(), Ty, CostKind);
} else
Cost = AArch64TTIImpl::getIntImmCost(Imm, Ty, CostKind);
return (Cost <= NumConstants * TTI::TCC_Basic) ? TTI::TCC_Free : Cost;
}
return AArch64TTIImpl::getIntImmCost(Imm, Ty, CostKind);
}
Expand Down Expand Up @@ -511,9 +534,7 @@ AArch64TTIImpl::getIntImmCostIntrin(Intrinsic::ID IID, unsigned Idx,
if (Idx == 1) {
int NumConstants = (BitSize + 63) / 64;
InstructionCost Cost = AArch64TTIImpl::getIntImmCost(Imm, Ty, CostKind);
return (Cost <= NumConstants * TTI::TCC_Basic)
? static_cast<int>(TTI::TCC_Free)
: Cost;
return (Cost <= NumConstants * TTI::TCC_Basic) ? TTI::TCC_Free : Cost;
}
break;
case Intrinsic::experimental_stackmap:
Expand Down