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[LoongArch] Initial implementation for enableMemCmpExpansion hook #166526

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Merged
merged 4 commits into from
Nov 10, 2025
+4,255 −1,253
Merged

[LoongArch] Initial implementation for enableMemCmpExpansion hook #166526

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d62b0ad
[LoongArch] Initial implementation for `enableMemCmpExpansion` hook
zhaoqi5 Nov 5, 2025
3cc959d
enable tail expansion which will reduce branches like aarch64/riscv
zhaoqi5 Nov 6, 2025
25bbbf0
rebase && update tests
zhaoqi5 Nov 7, 2025
fd004e2
remove TODO
zhaoqi5 Nov 7, 2025
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23 changes: 22 additions & 1 deletion llvm/lib/Target/LoongArch/LoongArchTargetTransformInfo.cpp
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Expand Up @@ -111,4 +111,25 @@ bool LoongArchTTIImpl::shouldExpandReduction(const IntrinsicInst *II) const {
}
}

// TODO: Implement more hooks to provide TTI machinery for LoongArch.
LoongArchTTIImpl::TTI::MemCmpExpansionOptions
LoongArchTTIImpl::enableMemCmpExpansion(bool OptSize, bool IsZeroCmp) const {
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@SixWeining SixWeining Nov 7, 2025

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IsZeroCmp is not used currently?

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@zhaoqi5 zhaoqi5 Nov 7, 2025

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Yes. It is not been used for now. Whether it is ZeroCmp or not, enable memcmp expansion is beneficial.

TTI::MemCmpExpansionOptions Options;

if (!ST->hasUAL())
return Options;

Options.MaxNumLoads = TLI->getMaxExpandSizeMemcmp(OptSize);
Options.NumLoadsPerBlock = Options.MaxNumLoads;
Options.AllowOverlappingLoads = true;

// TODO: Support for vectors.
if (ST->is64Bit()) {
Options.LoadSizes = {8, 4, 2, 1};
Options.AllowedTailExpansions = {3, 5, 6};
} else {
Options.LoadSizes = {4, 2, 1};
Options.AllowedTailExpansions = {3};
}

return Options;
}
3 changes: 2 additions & 1 deletion llvm/lib/Target/LoongArch/LoongArchTargetTransformInfo.h
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Expand Up @@ -55,7 +55,8 @@ class LoongArchTTIImpl : public BasicTTIImplBase<LoongArchTTIImpl> {

bool shouldExpandReduction(const IntrinsicInst *II) const override;

// TODO: Implement more hooks to provide TTI machinery for LoongArch.
TTI::MemCmpExpansionOptions
enableMemCmpExpansion(bool OptSize, bool IsZeroCmp) const override;
};

} // end namespace llvm
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