RFR: 8339790: Support Intel APX setzucc instruction [v3]

[Vladimir Kozlov]

On Fri, 13 Sep 2024 19:20:07 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> src/hotspot/cpu/x86/gc/x/x_x86_64.ad line 129:
>> 
>>> 127:   format %{ "lock\n\t"
>>> 128:             "cmpxchgq $newval, $mem\n\t"
>>> 129:             "sete_with_zextl  $res\n\t" %}
>> 
>> Please, use `setcc` in format to match `ins_encode`.  `sete_with_zextl` isused only when it is supported.
>
> Hi @vnkozlov ,
> setcc used in inst_encoding block is a macro assembly routine which emits either setcc + movzbl or setzucc for APX supported targets, I wanted to use one opto instruction to correctly depict semantics of both the cases.

Yes, I see `setcc` definition and using it in `format` is fine since it will match to `inst_encoding`.
On other hand, there is no macro or assembler instruction `sete_with_zextl` and it will be confusing.

If you want you can add comment to format (and you should not use `\n` in last line):

   "setcc    $res\t#  emits sete + movzbl or setzucc for APX" %}

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PR Review Comment: https://git.openjdk.org/jdk/pull/20920#discussion_r1759397114