Skip to content

[RISCV][TTI] Implement vector costs for llvm.fpto{u|s}i.sat(). #143655

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 4 commits into
base: main
Choose a base branch
from
Open

[RISCV][TTI] Implement vector costs for llvm.fpto{u|s}i.sat(). #143655

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
9916a5c
Precommit test case.
ElvisWang123 Jun 11, 2025
5a500d9
[RISCV][TTI] Implement cost for llvm.fpto{u|s}i.sat.
ElvisWang123 Jun 11, 2025
18ab4ca
!fixup, using poison
ElvisWang123 Jun 11, 2025
c96dbe2
!Fixup, skip cases with scalar type.
ElvisWang123 Jun 12, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
30 changes: 30 additions & 0 deletions llvm/lib/Target/RISCV/RISCVTargetTransformInfo.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1497,6 +1497,36 @@ RISCVTTIImpl::getIntrinsicInstrCost(const IntrinsicCostAttributes &ICA,
cast<VectorType>(ICA.getArgTypes()[0]), {}, CostKind,
0, cast<VectorType>(ICA.getReturnType()));
}
case Intrinsic::fptoui_sat:
Copy link
Collaborator

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Can we do this in target independent code? The missing scalarization for the source type isn't just a RISC-V bug.

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I think it is not only missing the scalarization for the source type, the cost of fptoui_sat is much lower than expect.

This can be implemented in BasicTTI::getIntrinsicInstrCost(). But when using type-based query it will try to get cost from BasicTTI::getTypeBasedIntrinsicInstrCost() which will return the cost different from the value-based query.

IIUC #97463 make the precedent that cost of intrinsics in getTypeBasedIntrinsicInstrCost() and not implemented before

llvm-project/llvm/include/llvm/CodeGen/BasicTTIImpl.h

Line 2511 in a3201ce

if (TLI->isOperationLegalOrPromote(ISD, LT.second)) {
should be handled by target.

case Intrinsic::fptosi_sat: {
InstructionCost Cost = 0;
bool IsSigned = ICA.getID() == Intrinsic::fptosi_sat;
Type *SrcTy = ICA.getArgTypes()[0];

auto SrcLT = getTypeLegalizationCost(SrcTy);
auto DstLT = getTypeLegalizationCost(RetTy);
if (!SrcTy->isVectorTy())
break;

if (!SrcLT.first.isValid() || !DstLT.first.isValid())
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Do we need to skip scalar type here as well?

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Yes, added. Thanks!

return InstructionCost::getInvalid();

IntrinsicCostAttributes Attrs1(Intrinsic::minnum, SrcTy, {SrcTy, SrcTy});
Cost += getIntrinsicInstrCost(Attrs1, CostKind);
IntrinsicCostAttributes Attrs2(Intrinsic::maxnum, SrcTy, {SrcTy, SrcTy});
Cost += getIntrinsicInstrCost(Attrs2, CostKind);
Cost +=
getCastInstrCost(IsSigned ? Instruction::FPToSI : Instruction::FPToUI,
RetTy, SrcTy, TTI::CastContextHint::None, CostKind);
if (IsSigned) {
Type *CondTy = RetTy->getWithNewBitWidth(1);
Cost += getCmpSelInstrCost(BinaryOperator::FCmp, SrcTy, CondTy,
CmpInst::FCMP_UNO, CostKind);
Cost += getCmpSelInstrCost(BinaryOperator::Select, RetTy, CondTy,
CmpInst::FCMP_UNO, CostKind);
}
return Cost;
Copy link
Collaborator

@topperc topperc Jun 11, 2025 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Don't we need to scale by the maximum of SrcLT.first and DstLT.first?

Copy link
Collaborator

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Oh, I guess each function does its own costing and scaling?

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Yes.

}
}

if (ST->hasVInstructions() && RetTy->isVectorTy()) {
Expand Down
Loading