RFR: 8354242: VectorAPI: combine vector not operation with compare [v5]

[Xiaohong Gong]

On Wed, 7 May 2025 11:02:43 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> Hi @jatin-bhateja It is feasible. But I was thinking about whether another solution would be better, which is to turn  `VectorMask.fromLong(SPECIES, -1L)` into `MaskAll(true)` in the mid-end. In this way, we don't need to check this pattern in this optimization. What do you think ?
>
> Yes, that's the right approach. For this PR, I think you can mix some test points covering compare, xor(maskAll(true)).

Yes, converting `VectorMask.fromLong(SPECIES, -1L)` to `MaskAll()` would be better, and that will benefit AArch64 as well, since `MaskAll()` is much more cheaper than `fromLong()` on AArch64. We can add such a transformation with another PR.

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PR Review Comment: https://git.openjdk.org/jdk/pull/24674#discussion_r2078760074