RFR: 8349582: APX NDD code generation for OpenJDK [v14]

[Emanuel Peter]

On Thu, 13 Mar 2025 17:50:20 GMT, Srinivas Vamsi Parasa <sparasa at openjdk.org> wrote:

>> The goal of this PR is to generate x86 code using Intel Advanced Performance Extensions (APX) instructions which doubles the number of general-purpose registers, from 16 to 32. Intel APX adds nondestructive destination (NDD) and no flags (NF) flavor for the scalar instructions through EVEX encoding.
>> 
>> For more information about APX, see https://www.intel.com/content/www/us/en/developer/articles/technical/advanced-performance-extensions-apx.html.
>
> Srinivas Vamsi Parasa has updated the pull request incrementally with one additional commit since the last revision:
> 
>   add comments for encoding and UCF

I cannot really review he content, nor can I really test the APX features.
But I also cannot directly see any issues with it.

Therefore, I'll approve.
Once the hardware is available, we will probably discover some issues and have to fix them then.

Thanks @vamsi-parasa for the work!

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Marked as reviewed by epeter (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/23501#pullrequestreview-2709875746