<i18n dev> RFR: 8302877: Speed up latin1 case conversions [v3]

[Eirik Bjorsnos]

On Tue, 21 Feb 2023 11:12:18 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.
>
> Eirik Bjorsnos has updated the pull request incrementally with three additional commits since the last revision:
> 
>  - Allow any integer codePoint by defaulting to Integer.parseInt
>  - Rename Latin1CaseConversions to just CaseConversions
>  - Remove a whitespace following 'if ('

Thanks, #12701 is ready for review.

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