Re: [RFC] Contributing tree-ssa to mainline

[Jan Hubicka <jh at suse dot cz>]

> 
> On Sat, 17 Jan 2004, Jan Hubicka wrote:
> > > My greatest disappointment working on GCC's optimizations, is that
> > > try as I might I've only ever been able to push Andreas' SPECcpu2000
> > > benchmarks perhaps a percentage point or two higher.  This on a platform
> > > where Microsoft's compilers score about 20% higher.  Intel similarly
> > > claims about 20% better performance than GCC on average.
> >
> > How did you got to this number?
> > This is definitly not the case of SPECint scpres I saw.  My experience
> > is that we are about 2-3% behind AMD published results in 32bit mode.
> 
> The published figures are on Andreas' site for the world to see.
> http://www.suse.de/~aj/SPEC/
> 
> If you click on "SPECint2000 results (permanent runs, non-reportable)"
> you get mainline's current performance, which from the graph at the
> bottom is just about 400 as of January 17th 2004.
> 
> If you then go to the section entitled "Comparisons with Other Compilers"
> and click on the "SPECint200 in 1.2GHZ AMD Athlon", which is described
> as "these results should give an indication of how good/bad GCC is",
> you'll see a SPEC report with SPECint2000 of 496.  And that was with
> the Intel 5.0 compiler!
> 
> The difference between 400 and 500 is about 20%.

You missed the fact that published results are on 1.2Ghz athlon with
more modern core, compared to our testers running 1.33.
There are unforutnately no published results for 1.33 Athlons
Additionally the settings are more comparable with our peak results as
ICC does profile feedback, unrolling, inlining, frame pointer omitting
and other stuff in the baseline results.

Finally there is noticeable difference caused by runtime library that
contains optimized malloc and few other tricks.
> 
> 
> Perhaps you could provide details of where you 2 or 3% comes from?

I did ICC runs with same config options myself on same hardware as
periodic testers use.  I am not sure I still have the numbers, but I
will try to dig out.

You can look at http://www.suse.de/~aj/SPEC/amd64 that contains bars for
ICC and 32bit compilers.
If I compute geometric average myself, i get 878 ICC score.  Compare it
to 820 produced by GCC peak in 32bit compilation and you get 7%
difference and take into account that profile feedback.
Then look at my GCC summit paper.  It contains tests with similar set of
opotimizations and it claims that 7.87% can be gained if Andreas used
PDO.

I need to produce true runs instead of such a hints, but it is clear
that we are not 20% behind at all.

Honza
> 
> Roger
> --