Re: RFA: patch for PR37397

[Vladimir Makarov <vmakarov at redhat dot com>]

H.J. Lu wrote:
> On Wed, Nov 12, 2008 at 9:17 AM, Jeff Law <law@redhat.com> wrote:
>   
> > Vladimir Makarov wrote:
> >     
> > > This patch improves SPEC benchmarks.  I saw stable improvements on
> > > x86/x86_64 and ppc.  This patch implements a small trick mentioned in one
> > > classical article by Chaitin etc (Register allocation and spilling via graph
> > > coloring).  There is no sense to spill pseudo in whose live range nothing is
> > > dying because the spill will not make other allocnos colorable and
> > > additional reloads for the corresponding pseudo will be generated in reload
> > > pass for each insn it occurs.
> > >
> > > Is it ok to commit?
> > >       
> > OK.  Good find.
> >
> >     
>
> Hi Vladimir,
>
> This caused 30% slowdown on 454.calculix in SPEC CPU 2006
> with -O2 -ffast-math on Linux/Intel64.
>
>
>   
H.J., thanks for reporting this.  I'll submit a patch today to fix it.