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Re: scheduling cc0
- From: Paul Schlie <schlie at comcast dot net>
- To: Miles Bader <miles at lsi dot nec dot co dot jp>,Steven Bosscher <stevenb at suse dot de>
- Cc: <gcc at gcc dot gnu dot org>
- Date: Wed, 02 Feb 2005 11:49:52 -0500
- Subject: Re: scheduling cc0
> Miles Bader writes
>> Steven Bosscher writes:
>> ...
>> The "recommended practice" of today is to use a fake hard register
>> for the CC reg, always, instead of cc0.
>> See e.g. "http://gcc.gnu.org/wiki/general backend cleanup", under
>> "Convert md files that use CC0 so they don't anymore." ...
>
> Hmmm, so that's basically the same method, but defined by the backend.
> Does this mean that any instruction that affects the cpu-flags (e.g.,
> addition) on such a processor has a (clobber (reg:SI CPU_FLAGS)) added
> to it? ...
It given Mile's observations, it seems that it may be quite reasonable
to enable GCC to more optimally interpret CC0 based machine descriptions,
rather than require natural CC0 based machines be described otherwise?