[Bug rtl-optimization/80425] Extra inter-unit register move with zero-extension

[ubizjak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80425

--- Comment #3 from Uroš Bizjak <ubizjak at gmail dot com> ---
(In reply to Vladimir Makarov from comment #2)

> So I don't know how to fix it in IRA or in LRA.  I am pretty sure the
> old RA and reload would have had the same problem.
> 
> Probably the issue should be fixed in machine dependent code.  But the fix
> might create more problems.

It is possible to create a couple of peephole2 patterns to catch this, but
perhaps REE can be enhanced to optimize the above register propagation, so the
solution would apply to all targets.