RFR: 8356159: RISC-V: Add Zabha [v10]

[Robbin Ehn]

On Thu, 29 May 2025 02:30:37 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 18 additional commits since the last revision:
>> 
>>  - Merge branch 'master' into 8356159
>>  - ins cost fixes, print fixes
>>  - Merge branch 'master' into 8356159
>>  - Reg limits fixed
>>  - Merge branch 'master' into 8356159
>>  - Fixed reg selection
>>  - More indention
>>  - Indention
>>  - Merge branch 'master' into 8356159
>>  - Review comments
>>  - ... and 8 more: https://git.openjdk.org/jdk/compare/5dabe204...4e572ee2
>
> src/hotspot/cpu/riscv/riscv.ad line 5315:
> 
>> 5313:   match(Set res (CompareAndSwapI mem (Binary oldval newval)));
>> 5314: 
>> 5315:   // TODO: If UseZacas use "2 * VOLATILE_REF_COST"
> 
> I see the aarch64 counterpart always use a cost of `2 * VOLATILE_REF_COST` [1][2][3], thus does not depend on `UseLSE`. I think maybe we can ignore `UseZacas` and alway use `2 * VOLATILE_REF_COST` to simply the case as well.
> 
> [1] https://github.com/openjdk/jdk/blob/master/src/hotspot/cpu/aarch64/aarch64.ad#L8360
> [2] https://github.com/openjdk/jdk/blob/master/src/hotspot/cpu/aarch64/aarch64.ad#L3311
> [3] https://github.com/openjdk/jdk/blob/master/src/hotspot/cpu/aarch64/macroAssembler_aarch64.cpp#L3466

Yes, sure, I'll update in this PR.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25252#discussion_r2115168582