Optimize away compare256 for short matches #284
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I'm posting this for discussion because it produces mixed results on my test system:
Whether it helps is probably dependent on the CPU and the input data. |
brian-pane
commented
Jan 11, 2025
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| if best_len < core::mem::size_of::<u64>() { | ||
| let scan_val = u64::from_ne_bytes( |
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I also tried if best_len < 32 { followed by the equivalent AVX2 implementation (similar to how compare32 processes each 32=byte chunk), but it was slower overall.
folkertdev
approved these changes
Jan 14, 2025
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I think a slightly higher instruction count (correctly predicted branches?) is totally acceptable if we get a performance boost, especially because levels 3,4, 7 and 8 are rarely used in practice.
And the gains at level 2 and 9 are very real, so I think this is OK. Thanks!
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