[Bug target/91753] Bad register allocation of multi-register types

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91753

--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #5)
> If we had a way to generate XImode directly from 4 V16QI, and only generate
> one move statement, then the register allocator would act better.

That or split the XI register move to do 4 V16QI/V4SI and only the final move
we generate the subreg.  I think this later one is the best option really, and
that lower-subreg.c pass should be doing but is not for some reason ....