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Re: [PATCH, 4.9/4.10] Profile based option tuning

> On Wed, Jul 23, 2014 at 2:39 AM, Pengfei Yuan <> wrote:
> > In the experiment, about 60% (1019/1699) profile data files are empty
> > (all counters are zero).
> Well, but you are globally overriding options even for the parts with
> profile.  The whole point of profile-feedback is to get at the interesting
> parts (those with non-zero counters).
> What you say is that not enough parts of the compiler care for
> the actual profiles and thus portions with all-zero counters are
> treated as if they were hot?  Then better fix that.

Most of the compiler should use the optimize_for_size/time predicates that should
get the case of empty profile right.  For missing profile I am not terribly decided
what to do - it may make sense to ignore all changes of -fprofile-use then, but it
seems users should just arrange profile when they want to use it (and we already
warn in that case)

What benefits you see from the patch?

> Richard.
> > 2014-07-22 21:39 GMT+08:00 Richard Biener <>:
> >> On Mon, Jul 21, 2014 at 7:13 AM, Pengfei Yuan <> wrote:
> >>> Hi,
> >>>
> >>> This patch tunes optimization options based on profile data:
> >>> * Disable PGO options if profile is not available or empty.
> >>> * Optimize for size if profile is available but empty.
> >>
> >> Err ... these don't seem interesting cases to "optimize" for?
> >>
> >> Richard.

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