[Libre-soc-dev] mv.zip and mv.unzip (vector pack and unpack)

[Jacob Lifshay]

On Mon, Jun 13, 2022, 09:50 lkcl <luke.leighton at gmail.com> wrote:

> love the override meaning of Saturation signed/unsigned to give more
> constants. put it in the page.
>
> can't do 0 -max +max in the same instruction, annoyingly, unless using
> zeroing predication hmm i am getting brainmeltdown thinking of how that
> would work, urr there is both sz and dz.
>

-max isn't commonly used so can be left out.

>
> nornal mode: https://libre-soc.org/openpower/sv/normal/
>
> 10 N dz sz sat mode: N=0/1 u/s
>
> if dz is set then zeros would be inserted on swizzle-skipped elements, but
> the sat/u would remain... no, too complicated.
>
> two mv instructions it'll have to be, one for zeros, the other for sat/u.
>

we likely need skip and 0/1 in the same instruction, so they can be done
simultaneously. so, no, dz won't be what's needed.

>
> skipping is COMPLEX it basically means a static predicate mask built-in to
> the swizzle, but the implication is that the source subvec len is
> *different* from the dest,
>

source subvec len being different from the dest subvec len is a large part
of why mv.swizzle exists, it is very much needed.

Jacob

>