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Re: Warning regression with COMPARE fixes
- To: mark at codesourcery dot com (Mark Mitchell)
- Subject: Re: Warning regression with COMPARE fixes
- From: Joern Rennecke <amylaar at cambridge dot redhat dot com>
- Date: Tue, 20 Mar 2001 20:43:04 +0000 (GMT)
- Cc: gcc at gcc dot gnu dot org, geoffk at cygnus dot com (Geoff Keating)
> In any case, I'd like other people's opinion on the question of
> whether or not this warning regression needs fixing. I have no idea
> how we might go about doing that; the key step, of course, is making
> sure the compiler realizes that the while-condition will be true the
> first time it is encountered. I understand how to do that
> algorithmically, but I have no idea what it would take in the compiler
> to regain that knowledge.
We can reverse the sense of a compare, sort of, by using the result
an a different mode. However, a reversed condition code mode
(which would be among these listed in EXTRA_CC_MODES) depends on
machine-specific code. I suppose we would need a target macro to
say if we have such a mode, and if yes, what it is.
Or we could just drop cc0 support altogether ;-)