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Re: [PATCH x86] Increase PARAM_MAX_COMPLETELY_PEELED_INSNS when branch is costly
- From: Evgeny Stupachenko <evstupac at gmail dot com>
- To: Eric Botcazou <ebotcazou at adacore dot com>
- Cc: Jan Hubicka <hubicka at ucw dot cz>, GCC Patches <gcc-patches at gcc dot gnu dot org>, Richard Biener <richard dot guenther at gmail dot com>, Uros Bizjak <ubizjak at gmail dot com>
- Date: Tue, 11 Nov 2014 18:28:21 +0300
- Subject: Re: [PATCH x86] Increase PARAM_MAX_COMPLETELY_PEELED_INSNS when branch is costly
- Authentication-results: sourceware.org; auth=none
- References: <CAOvf_xwBqY++PGRC_+1=rzHO18jvc+TP5mmR=PjYvGgm=63NuA at mail dot gmail dot com> <CAFiYyc1YjAYk8M8QMp=2Uo11SoQmZtcj-Eb=L-gxLyQ=6GTXmA at mail dot gmail dot com> <20141013122332 dot GA9404 at atrey dot karlin dot mff dot cuni dot cz> <9628485 dot KUeEEWl299 at polaris> <CAOvf_xxWJbREoYxGa4s0g5tQPhot4QTbnBfoW_ZKuSyirc5hWA at mail dot gmail dot com> <CAOvf_xzFR+x+FvUh7dXvvRC3K7=s2Mb3MzjofLnMzoHGNZmKTA at mail dot gmail dot com>
150 and 200 make Silvermont performance better on 173.applu (+8%) and
183.equake (+3%); Haswell spec2006 performance stays almost unchanged.
Higher value of 300 leave the performance of mentioned tests
unchanged, but add some regressions on other benchmarks.
So I like 200 as well as 120 and 150, but can confirm performance
gains only for x86.
On Fri, Nov 7, 2014 at 6:37 PM, Evgeny Stupachenko <evstupac@gmail.com> wrote:
> So are there any objections to enable this
> (PARAM_MAX_COMPLETELY_PEELED_INSNS increase from 100 to 120) for x86?
>
> On Fri, Oct 31, 2014 at 7:52 PM, Evgeny Stupachenko <evstupac@gmail.com> wrote:
>> I've measured spec2000, spec2006 as well and EEMBC for Silvermont in addition.
>> 100->120 change gives gain for Silvermont, the results on Haswell are flat.
>>
>> On Fri, Oct 31, 2014 at 3:14 PM, Eric Botcazou <ebotcazou@adacore.com> wrote:
>>>> Agreed, I think the value of 100 was set decade ago by Zdenek and me
>>>> completely artifically. I do not recall any serious tuning of this flag.
>>>
>>> Are you talking bout PARAM_MAX_COMPLETELY_PEELED_INSNS here? If so, see:
>>> https://gcc.gnu.org/ml/gcc-patches/2012-11/msg01193.html
>>>
>>> We have experienced performance regressions because of this arbitrary change
>>> and bumped it back to 200 unconditionally.
>>>
>>> --
>>> Eric Botcazou