Re: Some thoughts about steerring commitee work

["Vladimir N. Makarov" <vmakarov at redhat dot com>]

H. J. Lu wrote:

> On Fri, Jun 15, 2007 at 06:21:53PM -0700, Ian Lance Taylor wrote:
>  
>
> > This is hardly a new thought, but I believe that for the i386 gcc is
> > handicapped by reload.  No matter how smart we are before reload, it
> > just take one poor decision by reload in an inner loop and we've lost
> > all the gains.  Reload has enormous complexities which are mostly
> > irrelevant for the i386.  And I think that the idea of doing register
> > allocation separately from spill code generation does not make sense
> > on the i386.
> >
> >    
>
> Why don't we turn on vectorizer at -O3 or even -O2, depending on
> ISA? I added -ftree-vectorize to BOOT_CFLAGS on x86-64. According to
> -ftree-vectorizer-verbose=1, there are 82 loops vectorized in
> gcc source. There are no regressions. There are not much changes
> in bootstrap time as well as "make check" time.
>
>  
A mount ago I did some measurements of the effect of the vectorizer for 
Core2 in 64-bit mode.  Unfortunately, I saw small improvement (as I 
remember less than 1% for SPECInt2000).

Vectorizer is a big a project and may be we will see more improvements 
in future. They promissed implement SLP two years ago and now I see it 
happens.  It would be nice  to see it not only in loops.

Vlad