This is the mail archive of the
gcc@gcc.gnu.org
mailing list for the GCC project.
Re: -fprofile-generate and -fprofile-use
- From: girish vaitheeswaran <girish_vaithees at yahoo dot com>
- To: Jan Hubicka <jh at suse dot cz>, Peter Steinmetz <steinmtz at us dot ibm dot com>
- Cc: gcc at gcc dot gnu dot org, janis187 <janis187 at us dot ibm dot com>, girish_vaithees at yahoo dot com, hubicka at ucw dot cz
- Date: Tue, 30 Aug 2005 10:12:23 -0700 (PDT)
- Subject: Re: -fprofile-generate and -fprofile-use
I have tried with gcc 3.4.4 and still see the same
20%slowdown. If you folks are able to crack this, do
let me know. On my earlier attempts I had tried to
disable all of the flags that feedback optimization
turns on (except the ones that are turned on by
default) and still got the 20% slowdown.
Is there something that you would want me to try out
wrt to enabling/disabling certain flags, i'd be happy
to. The versions I have tried out so far are
2.95,3.4.3 and 3.4.4
-girish
--- Jan Hubicka <jh@suse.cz> wrote:
> >
> > There was some discussion a few weeks ago about
> some apps running slower
> > with FDO enabled.
> >
> > I've recently investigated a similar situation
> using mainline. In my case,
> > the fact that the loop_optimize pass is disabled
> during FDO was the cause
> > of the slowdown. It appears that was recently
> disabled as part of Jan
> > Hubicka's patch to eliminate RTL based profiling.
> The commentary indicates
> > that the old loop optimizer is incompatible with
> tree profiling.
> >
> > While this doesn't explain all of the degradations
> discussed (some were
> > showing up on older versions of the compiler), it
> may explain some.
>
> Do you have specific testcase? It would be
> interesting to see if new
> optimizer can catch up at least on kill-loop branch.
>
> Thanks for investigating!
> Honza
> >
> > Pete
>