RFR: 8322770: Implement C2 VectorizedHashCode on AArch64 [v20]

[Mikhail Ablakatov]

On Fri, 27 Sep 2024 12:48:37 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> Mikhail Ablakatov has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   fixup: use xaddwv2 where required in unit tests
>
> src/hotspot/cpu/aarch64/stubGenerator_aarch64.cpp line 5456:
> 
>> 5454:       } else {
>> 5455:         __ uaddwv2(vmul0, vmul0, Assembler::T4S, vdata0, Assembler::T8H);
>> 5456:       }
> 
> Maybe define `addwv2` and `addwv` in MacroAssembler.
> Suggestion:
> 
>         __ addwv2(is_signed_subword_type(eltype), vmul0, vmul0, Assembler::T4S, vdata0, Assembler::T8H);

I believe that an interface should be explicit and map 1:1 to real instructions when it comes to assembly whereas possible.

Anyway, regardless of my preferences, as far as I can see, currently `Assembler` provides all other signed/unsigned versions of arithmetic instructions separately. Adding a single method like this would make the whole API inconsistent. Therefore, I suggest leaving it as is.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18487#discussion_r1778644417