RFR: 8351994: Enable Extended EVEX to REX2/REX demotion when src and dst are the same [v36]

[Sandhya Viswanathan]

On Thu, 22 May 2025 20:48:38 GMT, Srinivas Vamsi Parasa <sparasa at openjdk.org> wrote:

>> Intel APX NDD instructions are encoded using EVEX encoding. The goal of this PR is to enable optimized instruction encoding for Intel APX NDD instructions when the non-destructive destination is same as the first source.
>> 
>> For example:
>> 
>> `eaddl r18, r18, r25` can be encoded as `addl r18, r25` using APX REX2 encoding
>> `eaddl r2, r2, r7` can be encoded as `addl r2, r7` using non-APX legacy encoding
>
> Srinivas Vamsi Parasa has updated the pull request incrementally with one additional commit since the last revision:
> 
>   refactor is_P6_or_later and remove cpu_family==18

We plan to integrate this PR on Monday June 2nd so as to not get very close to the upcoming fork next Thursday.

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PR Comment: https://git.openjdk.org/jdk/pull/24431#issuecomment-2923060837