RFR: 8349582: APX NDD code generation for OpenJDK [v12]

[Jatin Bhateja]

On Wed, 12 Mar 2025 20:52:07 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:
> 
>   undo changes to testing implementation

We also need to create a follow-up PR for Extended EVEX to REX2/REX demotions, this will require changes in the assembler layer and the compiler. I have already created one JBS for the RA side of the work. https://bugs.openjdk.org/browse/JDK-8351016

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PR Comment: https://git.openjdk.org/jdk/pull/23501#issuecomment-2720863576