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

[Sidraya Jayagond]

On Mon, 18 Mar 2024 06:31:10 GMT, Sidraya Jayagond <sjayagond at openjdk.org> wrote:

>> src/hotspot/cpu/s390/s390.ad line 754:
>> 
>>> 752:  Z_VR31, Z_VR31_H, Z_VR31_J, Z_VR31_K,
>>> 753: );
>>> 754: 
>> 
>> Why do you use only VR16 to VR31? If there is a reason, it should be explained in a comment.
>> PPC64 has these explanations:
>> // 1st 32 VSRs are aliases for the FPRs which are already defined above.
>> // 2nd 32 VSRs are aliases for the VRs which are only defined here.
>> // VSR52-VSR63 // nv!
>> (s390 has no nv VRs which makes them easier to use.)
>
> 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.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18162#discussion_r1528072522