mirror of
https://github.com/rust-lang/rust.git
synced 2026-06-01 14:10:03 +03:00
Manish Goregaokar
1979fa86f9
Optimize is_ascii for str and [u8]. This optimizes the `is_ascii` function for `[u8]` and `str`. I've been surprised this wasn't done for a while, so I just did it. Benchmarks comparing before/after look like: ``` test ascii::long_readonly::is_ascii_slice_iter_all ... bench: 174 ns/iter (+/- 79) = 40172 MB/s test ascii::long_readonly::is_ascii_slice_libcore ... bench: 16 ns/iter (+/- 5) = 436875 MB/s test ascii::medium_readonly::is_ascii_slice_iter_all ... bench: 12 ns/iter (+/- 3) = 2666 MB/s test ascii::medium_readonly::is_ascii_slice_libcore ... bench: 2 ns/iter (+/- 0) = 16000 MB/s test ascii::short_readonly::is_ascii_slice_iter_all ... bench: 3 ns/iter (+/- 0) = 2333 MB/s test ascii::short_readonly::is_ascii_slice_libcore ... bench: 4 ns/iter (+/- 0) = 1750 MB/s ``` (Taken on a x86_64 macbook 2.9 GHz Intel Core i9 with 6 cores) Where `is_ascii_slice_iter_all` is the old version, and `is_ascii_slice_libcore` is the new. I tried to document the code well, so hopefully it's understandable. It has fairly exhaustive tests ensuring size/align doesn't get violated -- because `miri` doesn't really help a lot for this sort of code right now, I tried to `debug_assert` all the safety invariants I'm depending on. (Of course, none of them are required for correctness or soundness -- just allows us to test that this sort of pointer manipulation is sound and such). Anyway, thanks. Let me know if you have questions/desired changes.