RFR: 8327652: S390x: Implements SLP support [v3]

[Sidraya Jayagond]

On Mon, 18 Mar 2024 12:59:12 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

>> Sidraya Jayagond has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Add proper comments and cosmetic changes.
>
> src/hotspot/cpu/s390/globals_s390.hpp line 115:
> 
>> 113:           "Use Z15 Vector instructions for superword optimization.")          \
>> 114:   product(bool, UseSFPV, false,                                               \
>> 115:           "Use SFPV Vector instructions for superword optimization.")         \
> 
> I'd probably make `UseSFPV` a diagnostic flag. Or do you think it needs to be an official flag which customers should set in production?
> (I think making `SuperwordUseVX` a regular product switch is fine as it is the fundamental switch for turning vectorization on or off.)

I'll fix this. Basically `UseSFPV` is for restrict z13  not to use vector float constrictions as they are not available on it.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18162#discussion_r1529623099