RFR: 8359419: AArch64: Relax min vector length to 32-bit for short vectors [v2]

[Xiaohong Gong]

On Wed, 2 Jul 2025 08:15:34 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> Xiaohong Gong has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Refine comments based on review suggestion
>
> src/hotspot/cpu/aarch64/aarch64.ad line 2367:
> 
>> 2365:   // Theoretically, the minimal vector length supported by AArch64
>> 2366:   // ISA and Vector API species is 64-bit. However, 32-bit or 16-bit
>> 2367:   // vector length is also allowed for special Vector API usages.
> 
> Suggestion:
> 
>   // Usually, the shortest vector length supported by AArch64
>   // ISA and Vector API species is 64 bits. However, we allow
>   // 32-bit or 16-bit vectors in a few special cases.
> 
> 
> Reason for change: it wasn't clear what "supported" meant. Supported by the hardware, or by HotSpot. And why do we only support it in a few special cases? This comment raises more questions than it answers.

Thanks so much for your suggestion! Looks better to me. I will update soon.

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PR Review Comment: https://git.openjdk.org/jdk/pull/26057#discussion_r2179517582