RFR: 8370863: VectorAPI: Optimize the VectorMaskCast chain in specific patterns [v6]

[Eric Fang]

On Mon, 15 Dec 2025 07:37:42 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> My main concern here is that the requirement for `VectorMaskCastNode` to have the same length for both input and output might have been removed in the future. I'm not sure, but we do require the lengths to be the same here, so I added this assertion. @eme64  has a similar comment; see https://github.com/openjdk/jdk/pull/28313/changes#r2614577536. So, if you all think that the requirement for lane length in `VectorMaskCastNode` won't be removed, then we can delete this assertion and the condition below.
>
> I think assertion here is redundant.

Yeah, I think deleting this assertion is also reasonable. After all, if the input and output lengths of `VectorMaskCastNode` are inconsistent, it will cause more problems. I will consider how to handle these two places in conjunction with @eme64's comment. Thanks!

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PR Review Comment: https://git.openjdk.org/jdk/pull/28313#discussion_r2621517632