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Re: [PATCH, 4.9/4.10] Profile based option tuning
- From: Richard Biener <richard dot guenther at gmail dot com>
- To: Pengfei Yuan <0xcoolypf at gmail dot com>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Wed, 23 Jul 2014 13:32:32 +0200
- Subject: Re: [PATCH, 4.9/4.10] Profile based option tuning
- Authentication-results: sourceware.org; auth=none
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On Wed, Jul 23, 2014 at 1:04 PM, Pengfei Yuan <firstname.lastname@example.org> wrote:
> I guess some optimizations are controlled only by "optimize_size", not
> by the profile.
I only see tree-inline.c:estimate_move_cost which we should indeed fix,
it could make a significant difference.
One other use in tree-ssa-phiopt.c, but probably doesn't really matter.
> 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 <email@example.com>:
>> On Wed, Jul 23, 2014 at 2:39 AM, Pengfei Yuan <firstname.lastname@example.org> 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 <email@example.com>:
>>>> On Mon, Jul 21, 2014 at 7:13 AM, Pengfei Yuan <firstname.lastname@example.org> 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?