Re: Smaller embedded version of the Vector extension
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Allowing VLEN<128 would allow for smaller vector register files, bit it would also result in a profile that is not forward-compatible with the V spec. This would produce another fracture the software ecosystem.
To avoid such a fracture, there are two choices:
(1) go with P instead
(2) relax the V spec to allow smaller implementations
So the key question for this group is whether to relax the minimum VLEN to 32 or 64?
note: a possible justification for keeping 128 might be to recommend (1) instead. I don’t know anything about P, but it seems like it could be speced in a way that is competitive/comparable with Helium.
PS — I have started to design an “RVV-lite” profile which would be more amenable to embedded implementations. However, I have adopted a stance that it must remain forward compatible with the full V spec, so I have not considered VLEN below 128. I am happy to share my work on this and involve other contributors — email me if you would like to see a copy.
On Wed, Jun 2, 2021 at 3:15 AM Andrew Waterman <andrew@...> wrote: