[Bug tree-optimization/36439] [4.3 Regression] very long compile-time in PRE building gimp-plugin-registry
------- Comment #15 from rguenth at gcc dot gnu dot org 2010-03-19 10:15 -------
(In reply to comment #14)
> Subject: Re: [4.3 Regression] very long
> compile-time in PRE building gimp-plugin-registry
>
> On Fri, 19 Mar 2010, kurt at garloff dot de wrote:
>
> > ------- Comment #11 from kurt at garloff dot de 2010-03-19 00:34 -------
> > (In reply to comment #10)
> > > GCC 4.3.4 is being released, adjusting target milestone.
> >
> > Very non-scientific benchmark:
> > Did compile latest gmic-1.3.4.0 on a 2xL5540 system (plenty of RAM) with make
> > -j8 and compile flags:
> > -O3 --param max-inline-insns-auto=200 -ffast-math -funroll-loops
> > -ftree-vectorize
> > Times (in seconds, user, elapsed):
> > 4.3.5: 1263u, 377e
> > w/ -fno-tree-pre: 755u, 202e
> > 4.4.4: 1022u, 311e
> > w/ -fno-tree-pre: 996u, 284e
> > 4.5.0: 2325u, 615e
> > w/ -fno-tree-pre: 1974u, 543e
> >
> > Note that this is in contrast to earlier observations that 4.4/4.5 did do much
> > better than 4.3. Don't know whether that's caused by changed gmic code or
> > whether we have regressed in 4.5. Let me know if you want me to pick one file
> > that takes particularly long to compile and investigate further.
>
> This bug was about PRE causing compile-time issues at -O2 which is
> what was investigated and fixed for the testcases attached to this PR.
>
> I see, for -O2 and the CImg.C testcase (just using openSUSE packages
> from devel:gcc):
>
> 4.3.4 (r152973): stopped after 4min
> 4.4.2 (r155966): 68s
> 4.5.0 (r157384): 74s
>
> also see PR43415 for a similar problem where I am about to commit a
> patch.
>
> If you can provide a testcase for plain -O3 [-ffast-math -funroll-loops]
> being slow it would be appropriate to open a new bugreport for it.
Oh, and btw check if you build with debuginfo enabled. With GCC 4.5 we
can spend quite some extra time producing "good" debug information.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36439
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