<i18n dev> RFR: 8302871: Speed up StringLatin1.regionMatchesCI [v14]

[Alan Bateman]

On Wed, 22 Feb 2023 20:01:52 GMT, Eirik Bjorsnos <duke at openjdk.org> wrote:

>> This PR suggests we can speed up `StringLatin1.regionMatchesCI` by applying 'the oldest ASCII trick in the book'.
>> 
>> The new static method `CharacterDataLatin1.equalsIgnoreCase` compares two latin1 bytes for equality ignoring case. `StringLatin1.regionMatchesCI` is updated to use `equalsIgnoreCase`
>> 
>> To verify the correctness of `equalsIgnoreCase`, a new test is added  to `EqualsIgnoreCase` with an exhaustive verification that all 256x256 latin1 code point pairs have an `equalsIgnoreCase` consistent with Character.toUpperCase, Character.toLowerCase.
>> 
>> Performance is tested for matching and mismatching cases of code point pairs picked from the ASCII letter, ASCII number and latin1 letter ranges. Results in the first comment below.
>
> Eirik Bjorsnos has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 21 additional commits since the last revision:
> 
>  - Merge branch 'master' into regionmatches-latin1-speedup
>  - Merge branch 'master' into regionmatches-latin1-speedup
>  - Make the loop variables chars to avoid casting
>  - Use improved case-twiddling comment as suggested by Martin
>  - Replace 'oldest ASCII trick in the book' use in toUpperCase, toLowerCase with "by removing (setting) a single bit"
>  - Align local variable naming in toLowerCase, toUpperCase with equalsIgnoreCase by using 'lower' and 'upper'
>  - Rename unconventionally named local variable 'U' to 'upper'
>  - Merge remote-tracking branch 'origin/master' into regionmatches-latin1-speedup
>  - Add whitespace between methods
>  - Merge branch 'master' into regionmatches-latin1-speedup
>  - ... and 11 more: https://git.openjdk.org/jdk/compare/6e269b24...597b346a

Marked as reviewed by alanb (Reviewer).

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PR: https://git.openjdk.org/jdk/pull/12632