RFR: JDK-8216437 : PPC64: Add intrinsic for GHASH algorithm [v29]

[Suchismith Roy]

On Wed, 19 Mar 2025 08:26:55 GMT, Suchismith Roy <sroy at openjdk.org> wrote:

>> JBS Issue : [JDK-8216437](https://bugs.openjdk.org/browse/JDK-8216437)
>> 
>> Currently acceleration code for GHASH is missing for PPC64. 
>> 
>> The current implementation utlilises SIMD instructions on Power and uses Karatsuba multiplication for obtaining the final result.
>
> Suchismith Roy has updated the pull request incrementally with three additional commits since the last revision:
> 
>  - comments
>  - comments
>  -  comments

Thank you all for the detailed reviews and for the approval.
I’ve noted the nits and fully agree they are valuable suggestions.
 To avoid additional commits at this stage, I’ll proceed with merging the current version, which is functionally correct. 
 
 I’ll make sure to incorporate the feedback in follow-up refinements as part of ongoing work, as there can be alternate implementations to pursue and better instructions to improve performance.

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PR Comment: https://git.openjdk.org/jdk/pull/20235#issuecomment-2827647069