commit | 8961f3ee758f18f3c5c707b76406afbe6238ef7e | [log] [tgz] |
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author | Simon Pilgrim <llvm-dev@redking.me.uk> | Tue Apr 29 10:35:15 2025 +0100 |
committer | GitHub <noreply@github.com> | Tue Apr 29 10:35:15 2025 +0100 |
tree | 9624bc31910070bb6012a6cdd0c9a60da40b89ca | |
parent | bb9fa77c8410e539d1eefdfe76c192db44bdc520 [diff] |
[X86] shouldReduceLoadWidth - don't split loads if we can freely reuse full width legal binop (#129695) Currently shouldReduceLoadWidth is very relaxed about when loads can be split to avoid extractions from the original full width load - resulting in many cases where the number of memory operations notably increases, replacing the cost of a extract_subvector for additional loads. This patch adjusts the 256/512-bit vector load splitting metric to detect cases where ANY use of the full width load is be used directly - in which case we will now reuse that load for smaller types, unless we'd need to extract an upper subvector / integer element - i.e. we now correctly treat (extract_subvector cst, 0) as free. We retain the existing logic of never splitting loads if all uses are extract+stores but we improve this by peeking through bitcasts while looking for extract_subvector/store chains. This required a number of fixes - shouldReduceLoadWidth now needs to peek through bitcasts UP the use-chain to find final users (limited to hasOneUse cases to reduce complexity). It also exposed an issue in isTargetCanonicalConstantNode which assumed that a load of vector constant data would always extract, which is no longer the case.
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