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From: "rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug lto/54966] Does LTO requires a larger inline-unit-growth?
Date: Tue, 23 Oct 2012 14:02:00 -0000 [thread overview]
Message-ID: <bug-54966-4-5cx9YEshjg@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-54966-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54966
--- Comment #5 from rguenther at suse dot de <rguenther at suse dot de> 2012-10-23 14:02:05 UTC ---
On Tue, 23 Oct 2012, hubicka at ucw dot cz wrote:
>
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54966
>
> --- Comment #4 from Jan Hubicka <hubicka at ucw dot cz> 2012-10-23 13:59:38 UTC ---
> > I'm not sure how we count the initial unit size, given that when not using
> > LTO not merged comdats are probably counted here, so overall they add up
> > while the initial LTO unit size may be considerably smaller than the sum
> > of the non-LTO unit sizes.
>
> I do not realy see problem here. We simply count size of the unit by summing
> all the functions in the callgraph prior inlining (after merging). So in the
> case of LTO we count COMDATs once and if they are unused by non-LTO we promote
> them to static and get better inlining due removing offline copies (that we are
> acccounting as inline decisions are made). In the case of non-LTO we count
> COMDAT in every unit that has the COMDAT used + we have heuristic predicting
> that most likely the COMDAT will be eliminated in the other units, too, if it
> is eliminated in the current unit. So we inline them almost as aggressively as
> statics, but not quite.
>
> What kind of problem are you looking into?
I was just guessing why our overall unit-growth heuristics would
lead to different overall inlining with LTO vs. single TUs.
Richard.
next prev parent reply other threads:[~2012-10-23 14:02 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-18 6:29 [Bug lto/54966] New: " vincenzo.innocente at cern dot ch
2012-10-18 7:47 ` [Bug lto/54966] " dominiq at lps dot ens.fr
2012-10-18 9:44 ` rguenth at gcc dot gnu.org
2012-10-19 8:37 ` vincenzo.innocente at cern dot ch
2012-10-23 13:59 ` hubicka at ucw dot cz
2012-10-23 14:02 ` rguenther at suse dot de [this message]
2012-10-23 14:13 ` hubicka at ucw dot cz
2012-11-08 16:44 ` hubicka at gcc dot gnu.org
2012-11-09 6:39 ` vincenzo.innocente at cern dot ch
2012-11-09 6:52 ` vincenzo.innocente at cern dot ch
2012-11-09 11:33 ` vincenzo.innocente at cern dot ch
2012-11-12 13:20 ` vincenzo.innocente at cern dot ch
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