> I started with a clean slate in my build environment > and did not have any residual files hanging around. > Are the steps I have indicated in my earlier email > correct. Is there a way I can break down the problem > into a smaller sub-set of flags and eliminate the flag > causing the performance problem. What I mean is since > -fprofile-generate and -fprofile-use enable a bunch of > flags, would it make sense to avoid profiling and try > out some of the individual flags on a trial and error > basis. If so what would be the flags to start the It would be probably better to just turn off the individual optimizations with -fprofile-use (for optimizations that are implied by this flag there should be no need to re-profile each time). If you can find particular optimization that gets out of control, it would be lot easier to fix it...
Honza > trials with. > > -girish > > --- Jan Hubicka <[EMAIL PROTECTED]> wrote: > > > > On Wed, Jul 20, 2005 at 10:45:01AM -0700, girish > > vaitheeswaran wrote: > > > > > --- Steven Bosscher <[EMAIL PROTECTED]> wrote: > > > > > > > > > > > On Wednesday 20 July 2005 18:53, girish > > vaitheeswaran wrote: > > > > > > > I am seeing a 20% slowdown with feedback > > optimization. > > > > > > > Does anyone have any thoughts on this. > > > > > > > > > > > > My first thought is that you should probably > > first > > > > > > tell what compiler > > > > > > you are using. > > > > > > > > I am using gcc 3.4.3 > > > > -girish > > > > > > Which platform? I've seen slower code for > > profile-directed optimizations > > > on powerpc64-linux with GCC 4.0 and mainline. > > It's a bug, but I haven't > > > looked into it enough to provide a small test case > > for a problem report. > > > > Actually I would be very interested in seeing > > testcases such as those. > > (and the Girish' slowdown too if possible). In > > general some slowdowns > > in side corners are probably unavoidable but both > > 3.4.3 and 4.0 seems to > > have pretty consistent improvements with profiling > > at least for SPEC and > > i386 I am testing pretty regularly. > > Such slodowns usually indicate problems like > > incorrectly updated profile > > or incorrectly readed in profile because of > > missmatch in CFGs in between > > profile and feedback run that are rather dificult to > > notice and hunt > > down... > > > > Honza > > > > > > Janis > >
