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Re: Help w/ CFG/loop optimization problem?
- From: Dale Johannesen <dalej at apple dot com>
- To: Roger Sayle <roger at eyesopen dot com>
- Cc: Dale Johannesen <dalej at apple dot com>, gcc-patches at gcc dot gnu dot org
- Date: Tue, 10 Sep 2002 16:04:58 -0700
- Subject: Re: Help w/ CFG/loop optimization problem?
On Tuesday, September 10, 2002, at 03:39 PM, Roger Sayle wrote:
Spooky! I posted to patch to gcc-patches to fix a similar problem
(CFG vs LOOP) less than an hour after your question.
I saw. Unfortunately your fix didn't fix my case, but I was looking
forward to hearing from you:)
Thanks, I'll look at that. I think it would be more general to have
I think I know a possible fix. I believe that the "conditional branch
over an unconditional branch" idiom that GCC's initial RTL generation
uses is a historical artifact. I suspect that GCC now handles long
conditional branches perfectly well, so creating jumps over jumps
does nothing but confuse CFG, which in turn confuses LOOP.
done in the optimization phases if possible, though; users can write
recognizable doloop-able loops in other ways than the usual C idioms.
Of course, some would argue they should be penalized for this.:)