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Re: [PATCH, 4.9/4.10] Profile based option tuning
- From: Pengfei Yuan <0xcoolypf at gmail dot com>
- To: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Wed, 23 Jul 2014 19:04:46 +0800
- Subject: Re: [PATCH, 4.9/4.10] Profile based option tuning
- Authentication-results: sourceware.org; auth=none
- References: <CACmZjJL=PPKMuCspMPfS82zud_rgshLM7VLzbMMkTQNs2DbupA at mail dot gmail dot com> <CAFiYyc0G33aJk95wr8vyHKJRwiciX4xTWjW4faz1_aLb7FdR_Q at mail dot gmail dot com> <CACmZjJLBf0xiKUxiYTOk7k110+HqRraLSfD-2iGeAHGbD+8g2g at mail dot gmail dot com> <CAFiYyc3P9pbx1Sj77Zy92us=ZF_D113Se6=pgkb4TSB-uAf0EA at mail dot gmail dot com>
I guess some optimizations are controlled only by "optimize_size", not
by the profile.
Other optimizations are controlled by the profile.
So this patch does not have very much effectiveness (only 0.9% size reduction).
2014-07-23 17:26 GMT+08:00 Richard Biener <firstname.lastname@example.org>:
> On Wed, Jul 23, 2014 at 2:39 AM, Pengfei Yuan <email@example.com> 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.
>> 2014-07-22 21:39 GMT+08:00 Richard Biener <firstname.lastname@example.org>:
>>> On Mon, Jul 21, 2014 at 7:13 AM, Pengfei Yuan <email@example.com> wrote:
>>>> 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?