Vector extension: Rotation

[ben-marshall]

From a mailing list discussion.

• There's no rotation instruction in the base vector spec at the moment, so I'd suggest adding:

vror.vv  vd, vs2, vs1 , vm   # Vector-vector
vror.vx  vd, vs2, rs1 , vm   # Vector-scalar
vrol.vv  vd, vs2, vs1 , vm   # Vector-vector
vrol.vx  vd, vs2, rs1 , vm   # Vector-scalar
vrori.vi vd, vs2, uimm, vm   # Vector-immediate

• These mirror the format of the existing Vector Single-Width Bit Shift Instructions, and replicate the same set of functionalities that the scalar Bitmanip instructions provide.

• For the vector Crypto extension, SEW=64 is the critical case for SHA3. I'm not sure about other element widths?

• It might make sense for the base vector spec to define this instruction, and then for the vector crypto extension to require only the SEW values that it needs. Arguably, crypto might only need the vector-vector variants?

[ben-marshall]

Andy's proposals can be found here. These will be transcribed into the draft spec.