RFR: 8329538: Accelerate P256 on x86_64 using Montgomery intrinsic [v12]

[Tobias Hartmann]

On Wed, 22 May 2024 14:19:36 GMT, Volodymyr Paprotski <duke at openjdk.org> wrote:

>> Volodymyr Paprotski 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 17 additional commits since the last revision:
>> 
>>  - Merge remote-tracking branch 'origin/master' into ecc-montgomery
>>  - shenandoah verifier
>>  - comments from Sandhya
>>  - whitespace
>>  - add message back
>>  - whitespace
>>  - Use AffinePoint to exit Montgomery domain
>>    
>>    Style notes:
>>    Affine.equals()
>>        - Mismatched fields only appear to be used from testing, perhaps should be moved there instead
>>    Affine.getX(boolean)|getY(boolean)
>>        - "Passing flag is bad design" - cleanest/performant alternative to several instanceof checks
>>        - needed to convert Affine to Projective (need to stay in montgomery domain)
>>    ECOperations.PointMultiplier
>>       - changes could probably be restored to original (since ProjectivePoint handling no longer required)
>>       - consider these changes an improvement? (fewer nested classes)
>>       - was an inner-class but not using inner-class features (i.e. ecOps variable should be converted)
>>  - whitespace
>>  - Comments from Tony and Jatin
>>  - Comments from Jatin and Tony
>>  - ... and 7 more: https://git.openjdk.org/jdk/compare/1adfff34...b1a33004
>
> Thanks Tobi!

Unfortunately, this caused a performance regression, see [JDK-8333583](https://bugs.openjdk.org/browse/JDK-8333583). @vpaprotsk, please have a look.

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PR Comment: https://git.openjdk.org/jdk/pull/18583#issuecomment-2149576062