AVR: CC0 to CCmode conversion

[Paul Schlie]

> Denis wrote:
> I have converted the AVR port from CC0 to CCmode.
> But may be I have converted the port in wrong way.
> (It's because I was interested in *this* way.)
> 
> I have used CCmode register and havn't added the
> '(clobber (reg:QI CC_REGNUM))' to any insn that really clobber the
> CC_REGNUM just because AVR is'n needed in scheduling.
> I think that sequence of compare + cond-jump will exists in any
> compiler pass.
> The port was successfully tested without new regressions.
> What do you (MAINTAINERS) think about this ?

Interesting:

- might you be able to post the resulting port files for review?

- are you proposing that all conditional branches then required to be
  explicitly paired with a corresponding immediately previous compare
  instruction?

  (if so, how is this a good thing observing that it's fairly typical
  for most conditional branches to be naturally based on comparisons
  against 0 resulting from the immediately preceding operation, which
  would have otherwise not required an explicit compare?)

thanks