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

[Andrew Haley]

On Fri, 27 Sep 2024 13:36:06 GMT, Mikhail Ablakatov <duke at openjdk.org> wrote:

>> 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.

I have no problem at all with what class Assembler provides. However, when the result looks like this, even a "normal" assembler programmer would suggest macros rather than copy-and-paste:


     assert(is_subword_type(eltype), "subword type expected");
      if (is_signed_subword_type(eltype)) {
        __ saddwv(vmul3, vmul3, Assembler::T4S, vdata3, Assembler::T4H);
        __ saddwv(vmul2, vmul2, Assembler::T4S, vdata2, Assembler::T4H);
        __ saddwv(vmul1, vmul1, Assembler::T4S, vdata1, Assembler::T4H);
        __ saddwv(vmul0, vmul0, Assembler::T4S, vdata0, Assembler::T4H);
      } else {
        __ uaddwv(vmul3, vmul3, Assembler::T4S, vdata3, Assembler::T4H);
        __ uaddwv(vmul2, vmul2, Assembler::T4S, vdata2, Assembler::T4H);
        __ uaddwv(vmul1, vmul1, Assembler::T4S, vdata1, Assembler::T4H);
        __ uaddwv(vmul0, vmul0, Assembler::T4S, vdata0, Assembler::T4H);
      }

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PR Review Comment: https://git.openjdk.org/jdk/pull/18487#discussion_r1778746689