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Re: Missed optimization in m68k
- From: Peter Barada <pbarada at mail dot wm dot sps dot mot dot com>
- To: law at redhat dot com
- Cc: apl at alum dot mit dot edu, Peter dot Barada at motorola dot com, gcc at gcc dot gnu dot org
- Date: Fri, 14 Jun 2002 19:34:41 -0400
- Subject: Re: Missed optimization in m68k
- References: <20671.1024092433@porcupine.cygnus.com>
> > > > In this case, I suspect that a DEFINE_PEEPHOLE is probably better!
> > >I don't think so -- the whole point behind NOTICE_UPDATE_CC is to be
> > >able to eliminate useless tst insns because the cc value happens to
> > >be lying around due to an earlier load/store or arithmetic instruction.
> > >
> >
> > But the TST isn't useless - it has a side-effect of
> > postincrementing the pointer.
>Ahhh. Silly me. You're right. This is kind-of a pain to fix right;
>peepholes may be the answer.
I'll assume that this is a regression from a previous version(how far
back I don't have a clue). I'll look at a peephole2 to see if it
solves the problem, and at that point submit a patch relative to 3.0.4
for gcc/config/m68k/m68k.md
Since you've got my attention, what's the real solution that you're
thinking about instead of the peephole I'll implement for the moment
to get around it....
--
Peter Barada Peter.Barada@motorola.com
Wizard 781-852-2768 (direct)
WaveMark Solutions(wholly owned by Motorola) 781-270-0193 (fax)