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Optimizations to narrow() - #414
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I appreciate the quick turnaround and also you being upfront about it 😅 But yeah, since this doesn't introduce any new APIs and the tests should catch any regressions, there's not much here to review |
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Yeah sorry, I think at this point I'm already too much out-of-context to provide meaningful reviews, and also time-constrained. But unlikely anyone else from Linebender will review, and I don't want to prevent you from landing improvements! |
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AVX-512 dedicated instructions for narrowing integers are actually slower than simply reusing the AVX2 approach. Lower latency but higher throughput, and SIMD cares mostly about throughput.
This fixes a large performance drop when enabling AVX-512 in my port of
jpeg-encoderto Fearless SIMD.Also optimizes the relaxed paths - they can be cheaper than either wrapping or saturation if the input is known to fit into the narrower type.