RFR: 8327652: S390x: Implements SLP support [v2]

[Martin Doerr]

On Mon, 18 Mar 2024 08:37:36 GMT, Sidraya Jayagond <sjayagond at openjdk.org> wrote:

>> In s390, 1st 16 VRs are aliases for the FPRs same as PPC. I will add proper explanation for this.
>
> Since f0-f15 overlap with v0-v15, does register allocate takes care of not to allocate same float register to corresponding live vector register or vice-versa? e.g f1 and v1 registers.

You use `ALLOC_IN_RC(z_v_reg)` in `vecX(),` so FP and VR are disjoint. That looks correct. Only the comments are missing.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18162#discussion_r1528140708