8ec348afdd
Performs slightly better in short or medium bytes by eliminating the last branch check on `byte_pos == len` and always check the last byte as it is always at most one `usize`. Benchmark, before `libcore`, after `libcore_new`. It improves medium and short by 1ns but regresses unaligned_tail by 2ns, either way we can get unaligned_tail have a tiny chance of 1/8 on a 64 bit machine. I don't think we should bet on that, the probability is worse than dice. test long::case00_libcore ... bench: 38 ns/iter (+/- 1) = 183947 MB/s test long::case00_libcore_new ... bench: 38 ns/iter (+/- 1) = 183947 MB/s test long::case01_iter_all ... bench: 227 ns/iter (+/- 6) = 30792 MB/s test long::case02_align_to ... bench: 40 ns/iter (+/- 1) = 174750 MB/s test long::case03_align_to_unrolled ... bench: 19 ns/iter (+/- 1) = 367894 MB/s test medium::case00_libcore ... bench: 5 ns/iter (+/- 0) = 6400 MB/s test medium::case00_libcore_new ... bench: 4 ns/iter (+/- 0) = 8000 MB/s test medium::case01_iter_all ... bench: 20 ns/iter (+/- 1) = 1600 MB/s test medium::case02_align_to ... bench: 6 ns/iter (+/- 0) = 5333 MB/s test medium::case03_align_to_unrolled ... bench: 5 ns/iter (+/- 0) = 6400 MB/s test short::case00_libcore ... bench: 7 ns/iter (+/- 0) = 1000 MB/s test short::case00_libcore_new ... bench: 6 ns/iter (+/- 0) = 1166 MB/s test short::case01_iter_all ... bench: 5 ns/iter (+/- 0) = 1400 MB/s test short::case02_align_to ... bench: 5 ns/iter (+/- 0) = 1400 MB/s test short::case03_align_to_unrolled ... bench: 5 ns/iter (+/- 1) = 1400 MB/s test unaligned_both::case00_libcore ... bench: 4 ns/iter (+/- 0) = 7500 MB/s test unaligned_both::case00_libcore_new ... bench: 4 ns/iter (+/- 0) = 7500 MB/s test unaligned_both::case01_iter_all ... bench: 26 ns/iter (+/- 0) = 1153 MB/s test unaligned_both::case02_align_to ... bench: 13 ns/iter (+/- 2) = 2307 MB/s test unaligned_both::case03_align_to_unrolled ... bench: 11 ns/iter (+/- 0) = 2727 MB/s test unaligned_head::case00_libcore ... bench: 5 ns/iter (+/- 0) = 6200 MB/s test unaligned_head::case00_libcore_new ... bench: 5 ns/iter (+/- 0) = 6200 MB/s test unaligned_head::case01_iter_all ... bench: 19 ns/iter (+/- 1) = 1631 MB/s test unaligned_head::case02_align_to ... bench: 10 ns/iter (+/- 0) = 3100 MB/s test unaligned_head::case03_align_to_unrolled ... bench: 14 ns/iter (+/- 0) = 2214 MB/s test unaligned_tail::case00_libcore ... bench: 3 ns/iter (+/- 0) = 10333 MB/s test unaligned_tail::case00_libcore_new ... bench: 5 ns/iter (+/- 0) = 6200 MB/s test unaligned_tail::case01_iter_all ... bench: 19 ns/iter (+/- 0) = 1631 MB/s test unaligned_tail::case02_align_to ... bench: 10 ns/iter (+/- 0) = 3100 MB/s test unaligned_tail::case03_align_to_unrolled ... bench: 13 ns/iter (+/- 0) = 2384 MB/s Rough (unfair) maths on improvements for fun: 1ns * 7/8 - 2ns * 1/8 = 0.625ns Inspired by fish and zsh clever trick to highlight missing linefeeds (⏎) and branchless implementation of binary_search in rust. |
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| .. | ||
| alloc | ||
| backtrace@4083a90168 | ||
| core | ||
| panic_abort | ||
| panic_unwind | ||
| proc_macro | ||
| profiler_builtins | ||
| rtstartup | ||
| rustc-std-workspace-alloc | ||
| rustc-std-workspace-core | ||
| rustc-std-workspace-std | ||
| std | ||
| stdarch@78891cdf29 | ||
| term | ||
| test | ||
| unwind | ||