RFR: 8338023: Support two vector selectFrom API [v13]

[Sandhya Viswanathan]

On Thu, 3 Oct 2024 05:04:35 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> I see the problem with float/double vectors. Let us do the rearrange form only for Integral (byte, short, int, long) vectors then. For float/double vector we could keep the code that you have currently.
>
> You will also need additional handling for NPOT vector sizes which is handled by existing fallback implementation.

The intrinsic is limited to power of two. We can safely do src1.rearrange(this.lanewise(VectorOperators.AND, 2 * VLENGTH - 1).toShuffle(), src2) for integral types.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20508#discussion_r1786637638