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Re: Compilation performance of GCC 3.4.2 and GCC 4.0.0 (041021) on tramp3d-v3
- From: Richard Guenther <richard dot guenther at gmail dot com>
- To: Richard Guenther <rguenth at tat dot physik dot uni-tuebingen dot de>
- Cc: gcc at gcc dot gnu dot org
- Date: Wed, 3 Nov 2004 16:53:25 +0100
- Subject: Re: Compilation performance of GCC 3.4.2 and GCC 4.0.0 (041021) on tramp3d-v3
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- References: <Pine.LNX.4.44.0410251410110.10994-100000@alwazn.tat.physik.uni-tuebingen.de>
- Reply-to: Richard Guenther <richard dot guenther at gmail dot com>
On Mon, 25 Oct 2004 15:00:21 +0200 (CEST), Richard Guenther
<rguenth@tat.physik.uni-tuebingen.de> wrote:
> Just to have another datapoint besides Karels observations. I'm
> using the tramp3d-v3.cpp testcase in place for testing POOMA
> application performance. The testcase can be fetched from
>
> http://www.tat.physik.uni-tuebingen.de/~rguenth/gcc/tramp3d-v3.cpp.gz
>
> detailled logs (including time-report) can be provided on demand.
> Testing is done by
> g++-3.4 -S tramp3d-v3.cpp -Dleafify=fooblah -ftime-report ...
> Note that both compilers are built with checking disabled,
> and 3.4.2 is profilebootstrapped, for 4.0.0 profilebootstrap doesnt work.
>
> ... 3.4.2 4.0.0 Delta%
> -O0 24.18s 19.90s 21.5
> -O1 83.75s
> -O1 -funit-at-a-time 50.70s 66.38s -24
> -O2 65.88s 88.18s -25
> -O2 -funroll-loops 69.73s 93.12s -25
>
> These figures may be distorted because (again) code metrics for
> inlining changed between 3.4.2 and 4.0.0 (and we're using unit-at-a-time
> for 4.0.0 always), so with leafifying included we get the following
> numbers:
>
> ... 3.4.2 4.0.0 Delta%
> -O1 -funit-at-a-time 70.26s 117.08s -40
> -O2 92.77s 150.35s -38
> -O2 -funroll-loops 97.71s 153.48s -36
> -O2 -fno-exceptions 67.90s 110.28s -38
>
> So while 4.0.0 really shines on -O0, it looses on optimization, typically
> about 20%. Especially with large and a huge number of BBs as resulting
> from inlining (or heavy inlining caused from leafifying) where we loose
> up to 40% speed!
> Note how exceptions cause a huge slow-down (~30%) in compilation time.
Due to recent work speeding up mainline expand times have dropped by over
50% (which is more than 10s for this testcase) at -O and -O2 (-O0
didn't change)!
Thanks!
Richard.