RFR: 8328998: Encoding support for Intel APX extended general-purpose registers [v15]

[Steve Dohrmann]

On Wed, 8 May 2024 10:12:29 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> Steve Dohrmann has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   parameter and local renames, update comment
>
> src/hotspot/cpu/x86/assembler_x86.cpp line 11902:
> 
>> 11900:     vex_x = (src_enc >= 16) && !src_is_gpr;
>> 11901:     attributes->set_is_evex_instruction();
>> 11902:     evex_prefix(vex_r, vex_b, vex_x, evex_r, evex_b, evex_v, false /*eevex_x*/, nds_enc, pre, opc);
> 
> Hi @steveatgh , UseAVX is set to level 3 only when target support AVX512F feature, entire encoding support for EVEX encoding is guarded by UseAVX > 2. Legacy map 2 and 3 instruction using EGPR register mandates Extended EVEX encoding and user may explicitly set UseAVX to level 2.
> What are your thoughts on extending the guarding check with UseAPX ?

Thanks @jatin-bhateja .  Do you mean a check such as:

`if ((UseAVX > 2 || UseAPX) && !attributes->is_legacy_mode())` ?

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PR Review Comment: https://git.openjdk.org/jdk/pull/18476#discussion_r1594587834