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Re: Overwhelmed by GCC frustration
- From: Eric Botcazou <ebotcazou at adacore dot com>
- To: Georg-Johann Lay <avr at gjlay dot de>
- Cc: gcc at gcc dot gnu dot org, Jeff Law <law at redhat dot com>, Segher Boessenkool <segher at kernel dot crashing dot org>, Oleg Endo <oleg dot endo at t-online dot de>
- Date: Wed, 16 Aug 2017 16:14:28 +0200
- Subject: Re: Overwhelmed by GCC frustration
- Authentication-results: sourceware.org; auth=none
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> 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.