RFR: 8356159: RISC-V: Add Zabha [v2]

[Robbin Ehn]

On Mon, 19 May 2025 14:43:19 GMT, Fei Yang <fyang at openjdk.org> wrote:

>> Robbin Ehn has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:
>> 
>>  - Revert back to default relaxed
>>  - Merge branch 'master' into 8356159
>>  - Fixed ws
>>  - Initial draft
>
> src/hotspot/cpu/riscv/assembler_riscv.hpp line 1066:
> 
>> 1064: 
>> 1065:   void lr_w(Register Rd, Register Rs1, Aqrl memory_order = relaxed) {
>> 1066:     amo_base<AMO_LR, AMO_WIDTH_WORD>(Rd, Rs1, 0, aqrl);
> 
> I see you always use `aqrl` here as the last param, which doesn't seem correct to me. But we should pass `memory_order` instead as that's the param? This seems to explain the bad performance impact.

Great find! Thanks!

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PR Review Comment: https://git.openjdk.org/jdk/pull/25252#discussion_r2095895768