RFR: 8318650: Optimized subword gather for x86 targets. [v2]

[Xiaohong Gong]

On Sun, 29 Oct 2023 22:23:09 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

> Due to lane size differences b/w sub-word and integer it may never be possible to have compatible species.

That's true. So maybe we could just 1) make sure the index array is inside of the boundary (i.e. the length is at least the same with the vectors), and 2) generate the index vectors during intrinsification for some architectures that need it (i.e. ARM SVE). For now, since only x86 implement it, maybe the second one is not needed.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16354#discussion_r1376942116