RFR: 8367292: VectorAPI: Optimize VectorMask.fromLong/toLong() for SVE [v3]

[Xiaohong Gong]

On Fri, 24 Oct 2025 07:25:55 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> Xiaohong Gong has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Rename the matcher function and fix comment issue
>
> src/hotspot/cpu/aarch64/aarch64_vector.ad line 402:
> 
>> 400:         // These ops are implemented with predicate instructions if input
>> 401:         // mask is a predciate.
>> 402:         return vt->isa_vectmask() == nullptr;
> 
> If we had an assert above, what else that `vt` could be other than `vectmask`, it would help in understanding this logic here ;)

`vt` is one of the normal `TypeVect` (i.e. `TypeVectA|S|D|X|Y|Z`) based on the vector length in bytes like other vector nodes. It is a a kind of `TypeVect` on architectures that do not support predicate feature. The mask is represented as the same with a vector on those platforms.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/27481#discussion_r2464287016