<i18n dev> RFR: 8302877: Speed up latin1 case conversions

[Naoto Sato]

On Fri, 17 Feb 2023 17:31:09 GMT, Eirik Bjorsnos <duke at openjdk.org> wrote:

> This PR suggests we speed up Character.toUpperCase and Character.toLowerCase for latin1 code points by applying the 'oldest ASCII trick in the book'.
> 
> This takes advantage of the fact that latin1 uppercase code points are always 0x20 lower than their lowercase (with the exception of two code points which uppercase out of latin1).
> 
> To verify the correctness of the new implementation, the test `Latin1CaseConversion` is added with an exhaustive verification of toUpperCase/toLowerCase for all latin1 code points.
> 
> The implementation needs to balance the performance of the various ranges in latin1. An effort has been made to favour operations on ASCII code points, without causing excessive regression for higher code points.
> 
> Performance is benchmarked for 7 chosen sample code points, each representing a range or a special-case.  Results in the first comment.

Looks good to me. I'd rather not use "case folding", as to me it implies "normalizing" but this is simply lowercasing/uppercasing.

test/jdk/java/lang/Character/Latin1CaseFolding.java line 31:

> 29: /**
> 30:  * @test
> 31:  * @summary Provides exchaustive verification of Character.toUpperCase and Character.toLowerCase

typo: "exhaustive"?

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PR: https://git.openjdk.org/jdk/pull/12623