Re: Compilation performance comparison of GCC 3.4.2 and GCC 4.0.0(20050127) on MICO sources

[Karel Gardas <kgardas at objectsecurity dot com>]

On Tue, 1 Feb 2005, Andrew Pinski wrote:

>
> On Jan 31, 2005, at 3:55 AM, Karel Gardas wrote:
>
> > Hello,
> >
> > last comparison is here:
> > http://gcc.gnu.org/ml/gcc/2004-12/msg01157.html
> >
> > Please note that for this comparison I've also redone 3.4.2 testing
> > and so
> > both 3.4.2 and 4.0.0 were run under same conditions. Last few
> > comparisons
> > were made with the same 3.4.2 results as you might noted. Overall
> > difference between old and new 3.4.2 results is about ~4% (for -O0
> > where I
> > noted it), with new results being better (faster). FYI: The hardware is
> > still the same, just kernel changed from 2.4.x to 2.6.x IIRC.
> >
> > Anyway, the results(regresssions), since overlall 4.0.0 seems to be
> > faster
> > for all -O0/1/2 than 3.4.2, are:
>
> Hmm, I notice you used a compiler from the 27th which the same day at
> which
> Steven applied a patch which should have sped up -O1.  I am thinking you
> were using a compiler before that because I got about a 3 seconds speed
> up
> at -O1 for ir.ii (or about a 5%) after his patch was applied.

No, I've waited and tested just after Steven's confirmation (thorough
bugzilla) that fix was commited. Anyway, gcc/ChangeLog contains:

$ head gcc-main/gcc/ChangeLog
2005-01-27  Steven Bosscher  <stevenb@suse.de>

        PR middle-end/17278
        * opts.c (decode_options): Move flag_thread_jumps from -O1 and
        higher to -O2 and higher.  Likewise for tree PRE.
        * tree-ssa-dom.c (tree_ssa_dominator_optimize): Only iterate at -O2
        and better.


Cheers,
Karel
--
Karel Gardas                  kgardas@objectsecurity.com
ObjectSecurity Ltd.           http://www.objectsecurity.com