RFR: 8351994: Enable Extended EVEX to REX2/REX demotion when src and dst are the same [v21]

[Srinivas Vamsi Parasa]

On Wed, 14 May 2025 15:46:48 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:
>> 
>>   eimull revert fully to original version
>
> src/hotspot/cpu/x86/assembler_x86.cpp line 4068:
> 
>> 4066: void Assembler::enegl(Register dst, Register src, bool no_flags) {
>> 4067:   InstructionAttr attributes(AVX_128bit, /* vex_w */ false, /* legacy_mode */ false, /* no_mask_reg */ true, /* uses_vl */ false);
>> 4068:   int encode = evex_prefix_and_encode_ndd(dst->encoding(), src->encoding(), VEX_SIMD_NONE, VEX_OPCODE_0F_3C, &attributes, no_flags);
> 
> Since VEX_OPCODE_OF_3C is not a standard MAP4 encoding please add /* MAP4 */ after it in the places.

Please see the update code with the change `VEX_OPCODE_OF_3C /* MAP4 */`

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PR Review Comment: https://git.openjdk.org/jdk/pull/24431#discussion_r2091696322