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Re: [PATCH] Fix the LOOP_BRANCH prediction


> On Tue, Jul 31, 2012 at 6:56 PM, Jan Hubicka <hubicka@ucw.cz> wrote:
> >> >
> >> > Yeah, this may also work.  The reason it is not done is that
> >> >  1) it seemed expensive to force CFG changes just to compute profile decade ago
> >> >  2) cfgcleanup afterwards will anyway remove the headers again.
> >> >     So I originally hoped to do the right thing without normalization.
> >>
> >> Ok ... then you should pass AVOID_CFG_MODIFICATIONS instead.  And be
> >> prepared for odd situations like this ;)
> >
> > Well, I guess we could do the extra work to avoid strange side cases like this.
> > Does normalization fix the testcase, too?
> 
> Normalization indeed fixed this issue too. So what shall we do about
> this patch? Shall we simply change to use normalization instead?

Yes, I think it is not _that_ expensive and we do some relatively tricky CFG
analysis there these days that should also get bit better.
(the code was written at a time CFG was new citizen to GCC and changes in CFG
was hard and considered harmful :)

Honza
> 
> Thanks,
> Dehao
> 
> >
> > Honza
> >>
> >> > Honza


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