RFR: 8351623: VectorAPI: Add SVE implementation of subword gather load operation [v3]

[Emanuel Peter]

On Fri, 1 Aug 2025 01:48:51 GMT, Xiaohong Gong <xgong at openjdk.org> wrote:

>> src/hotspot/cpu/arm/matcher_arm.hpp line 160:
>> 
>>> 158:   static const bool supports_encode_ascii_array = false;
>>> 159: 
>>> 160:   // Return true if vector gather-load/scatter-store needs vector index as input.
>> 
>> If the function returns `false`, does it indicate one of the following cases?
>> - Vector gather-load or scatter-store does not accept a vector index for the current use case on this platform.
>> - The current platform does not support vector gather-load or scatter-store at all.
>
> Yes, I think so.

To me a `false` means this:
If we support gater/scalter, then we do not need a vector index, we can do without it.

Is that correct?

But that would contradict @fg1417 's statement:
If we support gater/scalter, then we do not permit a vector index.

Can you clarify?

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PR Review Comment: https://git.openjdk.org/jdk/pull/26236#discussion_r2324726476