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

[Xiaohong Gong]

On Wed, 17 Sep 2025 06:18:30 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

> If I understood right, some platforms only support addr, some only index, right? Are there any that support both? 

Right. I don't think any arch support both the style. Either a vector index or an array address is enough.

Besides, C2 has the helper `Matcher::match_rule_supported_vector()` which can check whether an op is implemented yet or not.

> These are just some ideas. But from what you are telling me, it would really make sense to go with gather_scatter_requires_index_in_addr, since the addr case is indeed a corner-case.

Yes, I think this would be better. Thanks!

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PR Review Comment: https://git.openjdk.org/jdk/pull/26236#discussion_r2354434754