[Bug tree-optimization/36439] [4.3 Regression] very long compile-time in PRE building gimp-plugin-registry

["rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>]

------- Comment #14 from rguenther at suse dot de  2010-03-19 10:09 -------
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.

Thanks,
Richard.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36439