RFR: 8368722: RISC-V: Several vector load/store tests fail due to lack of support for misaligned vector access [v3]

[Hamlin Li]

On Thu, 9 Oct 2025 18:43:59 GMT, Hamlin Li <mli at openjdk.org> wrote:

>> Dingli Zhang 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 three additional commits since the last revision:
>> 
>>  - Merge remote-tracking branch 'upstream/master' into JDK-8368722-20251009
>>  - Add supports_misaligned_vector_accesses
>>  - 8368722: RISC-V: Several vector load/store tests fail without support for misaligned vector access
>
> src/hotspot/cpu/riscv/vm_version_riscv.cpp line 184:
> 
>> 182:     FLAG_SET_DEFAULT(AlignVector,
>> 183:       unaligned_vector.value() != MISALIGNED_VECTOR_FAST);
>> 184:   } else if (AlignVector == false) {
> 
> Seems these code is not necessary, as when `unaligned_vector` is not retrieved from kernel for any reason, user might want to pass `-XX:-AlignVector`.
> Your change disable this behaviour.

It seems my advice is the opposite of @iwanowww's, let's see what others think.

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PR Review Comment: https://git.openjdk.org/jdk/pull/27506#discussion_r2417687886