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Re: [PATCH, committed] Function specific option changes (IA-64, hot/cold, scheduling)

From: "Daniel Berlin" <dberlin at dberlin dot org>
To: "Andrew Pinski" <pinskia at gmail dot com>
Cc: "H.J. Lu" <hjl dot tools at gmail dot com>, "Michael Meissner" <gnu at the-meissners dot org>, "Jan Hubicka" <hubicka at ucw dot cz>, gcc-patches at gcc dot gnu dot org, karthikkumar at gmail dot com
Date: Sun, 27 Jul 2008 20:10:17 -0400
Subject: Re: [PATCH, committed] Function specific option changes (IA-64, hot/cold, scheduling)
References: <20080725235800.GA4363@tiktok.the-meissners.org> <20080726113829.GA26692@atrey.karlin.mff.cuni.cz> <20080726135539.GA25488@tiktok.the-meissners.org> <20080727175057.GA30776@lucon.org> <20080727232819.GA27730@tiktok.the-meissners.org> <de8d50360807271636v4f2bda43pa35668219f90d5bc@mail.gmail.com> <6dc9ffc80807271655i4a4c92bu83d84c7879e676d5@mail.gmail.com> <de8d50360807271701k1ea193b4r83bf4ecf74d48a56@mail.gmail.com>

On Sun, Jul 27, 2008 at 8:01 PM, Andrew Pinski <pinskia@gmail.com> wrote:
> On Sun, Jul 27, 2008 at 4:55 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> How about a switch to apply a specific set of optimization to all cold
>> functions,  like -Os -mpreferred-stack-boundary=2? Of cause, it should
>> be off by default.
>
> Why not just better tune the compiler?  Seriously what is happening is
> that are marking functions which are not really cold.

I would agree with this.

At Google we have seen some serious performance regressions because
the definition of cold function seems mildly broken in some way
(haven't analyzed yet) and marked *some of the hottest functions we
have* as cold.

Follow-Ups:
- Re: [PATCH, committed] Function specific option changes (IA-64, hot/cold, scheduling)
  - From: Michael Meissner

References:
- [PATCH, committed] Function specific option changes (IA-64, hot/cold, scheduling)
  - From: Michael Meissner
- Re: [PATCH, committed] Function specific option changes (IA-64, hot/cold, scheduling)
  - From: Jan Hubicka
- Re: [PATCH, committed] Function specific option changes (IA-64, hot/cold, scheduling)
  - From: Michael Meissner
- Re: [PATCH, committed] Function specific option changes (IA-64, hot/cold, scheduling)
  - From: H.J. Lu
- Re: [PATCH, committed] Function specific option changes (IA-64, hot/cold, scheduling)
  - From: Michael Meissner
- Re: [PATCH, committed] Function specific option changes (IA-64, hot/cold, scheduling)
  - From: Andrew Pinski
- Re: [PATCH, committed] Function specific option changes (IA-64, hot/cold, scheduling)
  - From: H.J. Lu
- Re: [PATCH, committed] Function specific option changes (IA-64, hot/cold, scheduling)
  - From: Andrew Pinski

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