RFR: 8320999: RISC-V: C2 RotateLeftV [v2]

[Hamlin Li]

On Fri, 24 May 2024 14:57:36 GMT, Fei Yang <fyang at openjdk.org> wrote:

>> I would also favor using `.vi` or `.vx` variants over `.vv` variants where possible. This would reduce the vector register pressure and remove an unnecessary instruction.
>> 
>> @Hamlin-Li  in your example, we could instead have:
>> 
>>   ... ...
>>   0x00002aaac560c594:   vle32.v v2,(a4)
>>   0x00002aaac560c598:   vsetivli        t0,8,e32,m1,tu,mu
>>   0x00002aaac560c59c:   vror.vx v2,v2,a3
>
> And for your case, this would help save the `vmv.v.x v1,a3` instruction if you do `vror.vv v2,v2,a3` instead of `vror.vv v2,v2,v1`. Right?

Thanks for clarification, I misunderstood.
Added vector-scalar rotate variants.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19325#discussion_r1616867157