Compilation performance of GCC 3.4.2 and GCC 4.0.0 (041021) on tramp3d-v3

[Richard Guenther]

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.