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[KeyInstr] MDNodeKeyImpl<DILocation> skip zero values for hash #143357

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Merged
merged 1 commit into from
Jun 9, 2025
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[KeyInstr] MDNodeKeyImpl<DILocation> skip zero values for hash #143357

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16 changes: 11 additions & 5 deletions llvm/lib/IR/LLVMContextImpl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -355,13 +355,19 @@ template <> struct MDNodeKeyImpl<DILocation> {
}

unsigned getHashValue() const {
return hash_combine(Line, Column, Scope, InlinedAt, ImplicitCode
#ifdef EXPERIMENTAL_KEY_INSTRUCTIONS
,
AtomGroup, (uint8_t)AtomRank);
#else
);
// Hashing AtomGroup and AtomRank substantially impacts performance whether
// Key Instructions is enabled or not. We can't detect whether it's enabled
// here cheaply; avoiding hashing zero values is a good approximation. This
// affects Key Instruction builds too, but any potential costs incurred by
// messing with the hash distribution* appear to still be massively
// outweighed by the overall compile time savings by performing this check.
// * (hash_combine(x) != hash_combine(x, 0))
if (AtomGroup || AtomRank)
return hash_combine(Line, Column, Scope, InlinedAt, ImplicitCode,
AtomGroup, (uint8_t)AtomRank);
#endif
return hash_combine(Line, Column, Scope, InlinedAt, ImplicitCode);
}
};

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