Overwhelmed by GCC frustration

[Eric Botcazou]

> Just the fact that the backends that get most attention and attract
> most developers don't use cc0 doesn't mean cc0 is a useless device.

Everything that can be done with cc0 can be done with the new representation, 
at least theoritically, although this can require more work.

> As far as cc0 is concerned, transforming avr BE is not trivial.
> It would need rewriting almost all of its md files entirely.
> It would need rewriting great deal of avr.c that handle
> insn output and provide input to NOTICE_UPDATE_CC.

I recently converted the Visium port, which is an architecture where every 
integer instruction, including a simple move, clobber the flags, so it's 
doable even for such an annoying target (but Visium is otherwise regular).
See for example https://gcc.gnu.org/wiki/CC0Transition for some guidelines.

> But my feeling is that opposing deprecation of cc0 is futile,
> the voices that support cc0 deprecation are more and usefulness
> of cc0 is not recognized.

cc0 is just obsolete and inferior compared to the new representation.

-- 
Eric Botcazou