[Bug target/92729] [avr] Convert the backend to MODE_CC so it can be kept in future releases

[abebeos at lazaridis dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92729

--- Comment #23 from abebeos at lazaridis dot com ---
(In reply to Senthil Kumar Selvaraj from comment #21)
> (https://github.com/saaadhu/gcc-avr-cc0/tree/avr-cc0-squashed)

I can still do a test-run, to see if it produces less fails than pip's one.
Though it seems pip's work "last 2%" should be manageable. But in any case,
having a 2nd solution-path (based on your work) is nice, as I really want to
avoid to start from scratch (after those weeks of mostly integration work).

> I don't have the spare time now to start full fledged work on this, but I
> can help with any issues you run into.

Very nice, I can isolate the errors like:

=> "sorry, unimplemented: '-fzero-call-used-regs' not supported on this target"

so you folks can take a look with minimum effort. I'll file issues within the
github repo when I cannot solve something myself.