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Slight perf improvement on char::to_ascii_lowercase #81837

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merged 5 commits into from
Feb 23, 2021
Merged

Slight perf improvement on char::to_ascii_lowercase #81837

merged 5 commits into from
Feb 23, 2021

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gilescope
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@gilescope gilescope commented Feb 6, 2021 •
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char::to_ascii_lowercase() was checking if it was ascii and then if it was in the right range. Instead propose to check once (I think removing a compare and a shift in the process: godbolt ).

before:

        test char::methods::bench_to_ascii_lowercase                    ... bench:      11,196 ns/iter (+/- 632)
        test char::methods::bench_to_ascii_uppercase                    ... bench:      11,656 ns/iter (+/- 671)

after:

         test char::methods::bench_to_ascii_lowercase                    ... bench:       9,612 ns/iter (+/- 979)
         test char::methods::bench_to_ascii_uppercase                    ... bench:       8,241 ns/iter (+/- 701)

(calling u8::to_ascii_lowercase and letting that flip the 5th bit is also an option, but it's more instructions. I'm thinking for things around ascii and char we want to be as efficient as possible.)

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r? @dtolnay

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@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Feb 6, 2021
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@gilescope gilescope mentioned this pull request Feb 7, 2021
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@jyn514 jyn514 added I-slow Issue: Problems and improvements with respect to performance of generated code. T-libs Relevant to the library team, which will review and decide on the PR/issue. A-unicode Area: Unicode labels Feb 7, 2021
dtolnay
dtolnay approved these changes Feb 8, 2021
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This lgtm but from the last comment it sounds like you are still working on it. Let me know when ready for review.

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dtolnay commented Feb 8, 2021

@rustbot modify labels: -S-waiting-on-review +S-waiting-on-author

@rustbot rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Feb 8, 2021
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@dtolnay I think the dust is setttled on this one and is ready for review.

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dtolnay commented Feb 19, 2021

@bors r+

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bors commented Feb 19, 2021

📌 Commit 33d8b04 has been approved by dtolnay

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Feb 19, 2021
Dylan-DPC-zz pushed a commit to Dylan-DPC-zz/rust that referenced this pull request Feb 20, 2021
@Dylan-DPC
Rollup merge of rust-lang#81837 - gilescope:to_ascii_speedups, r=dtolnay
6468333 
Slight perf improvement on char::to_ascii_lowercase

`char::to_ascii_lowercase()` was checking if it was ascii and then if it was in the right range. Instead propose to check once (I think removing a compare and a shift in the process: [godbolt](https://godbolt.org/z/e5Tora) ).

before:
```
        test char::methods::bench_to_ascii_lowercase                    ... bench:      11,196 ns/iter (+/- 632)
        test char::methods::bench_to_ascii_uppercase                    ... bench:      11,656 ns/iter (+/- 671)
```
after:
```
         test char::methods::bench_to_ascii_lowercase                    ... bench:       9,612 ns/iter (+/- 979)
         test char::methods::bench_to_ascii_uppercase                    ... bench:       8,241 ns/iter (+/- 701)
```

(calling u8::to_ascii_lowercase and letting that flip the 5th bit is also an option, but it's more instructions. I'm thinking for things around ascii and char we want to be as efficient as possible.)
@Dylan-DPC-zz Dylan-DPC-zz mentioned this pull request Feb 20, 2021
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Dylan-DPC-zz pushed a commit to Dylan-DPC-zz/rust that referenced this pull request Feb 23, 2021
@Dylan-DPC
Rollup merge of rust-lang#81837 - gilescope:to_ascii_speedups, r=dtolnay
39d841d 
Slight perf improvement on char::to_ascii_lowercase

`char::to_ascii_lowercase()` was checking if it was ascii and then if it was in the right range. Instead propose to check once (I think removing a compare and a shift in the process: [godbolt](https://godbolt.org/z/e5Tora) ).

before:
```
        test char::methods::bench_to_ascii_lowercase                    ... bench:      11,196 ns/iter (+/- 632)
        test char::methods::bench_to_ascii_uppercase                    ... bench:      11,656 ns/iter (+/- 671)
```
after:
```
         test char::methods::bench_to_ascii_lowercase                    ... bench:       9,612 ns/iter (+/- 979)
         test char::methods::bench_to_ascii_uppercase                    ... bench:       8,241 ns/iter (+/- 701)
```

(calling u8::to_ascii_lowercase and letting that flip the 5th bit is also an option, but it's more instructions. I'm thinking for things around ascii and char we want to be as efficient as possible.)
This was referenced Feb 23, 2021
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bors added a commit to rust-lang-ci/rust that referenced this pull request Feb 23, 2021
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Auto merge of rust-lang#82430 - Dylan-DPC:rollup-nu4kfyc, r=Dylan-DPC
a4e595d 
Rollup of 12 pull requests

Successful merges:

 - rust-lang#79423 (Enable smart punctuation)
 - rust-lang#81154 (Improve design of `assert_len`)
 - rust-lang#81235 (Improve suggestion for tuple struct pattern matching errors.)
 - rust-lang#81769 (Suggest `return`ing tail expressions that match return type)
 - rust-lang#81837 (Slight perf improvement on char::to_ascii_lowercase)
 - rust-lang#81969 (Avoid `cfg_if` in `std::os`)
 - rust-lang#81984 (Make WASI's `hard_link` behavior match other platforms.)
 - rust-lang#82091 (use PlaceRef abstractions more consistently)
 - rust-lang#82128 (add diagnostic items for OsString/PathBuf/Owned as well as to_vec on slice)
 - rust-lang#82166 (add s390x-unknown-linux-musl target)
 - rust-lang#82234 (Remove query parameters when skipping search results)
 - rust-lang#82255 (Make `treat_err_as_bug` Option<NonZeroUsize>)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit 4af965e into rust-lang:master Feb 23, 2021
@rustbot rustbot added this to the 1.52.0 milestone Feb 23, 2021
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Do we need not to do a perf run for this?

@lopopolo lopopolo mentioned this pull request Feb 23, 2021
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@illicitonion illicitonion mentioned this pull request May 5, 2021
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A-unicode Area: Unicode I-slow Issue: Problems and improvements with respect to performance of generated code. S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. T-libs Relevant to the library team, which will review and decide on the PR/issue.
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