RFR: 8351994: Enable Extended EVEX to REX2/REX demotion when src and dst are the same [v2]

[Srinivas Vamsi Parasa]

On Fri, 4 Apr 2025 03:04:56 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> Srinivas Vamsi Parasa has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Disable demotion for esetzucc and cleanup code
>
> src/hotspot/cpu/x86/assembler_x86.cpp line 13825:
> 
>> 13823:   return (!no_flags && dst_enc == nds_enc);
>> 13824: }
>> 13825: 
> 
> @vamsi-parasa , We are missing a case where dst_enc can be equal to src_enc; in that case, we can still demote EVEX to REX/REX2 encoding, along with a change in primary opcode if needed.
> 
> This will apply to all the commutative operations (ADD/ AND / OR / XOR)

Thanks for the proposal. This feature will be enabled in another PR using the JBS entry https://bugs.openjdk.org/browse/JDK-8354348.

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PR Review Comment: https://git.openjdk.org/jdk/pull/24431#discussion_r2038539820