Predictive commoning miscompiles 482.sphinx3 in SPEC CPU 2006

[Andrew Pinski]

On 6/1/07, H. J. Lu <hjl@lucon.org> wrote:
> On Fri, Jun 01, 2007 at 09:37:54AM -0700, H. J. Lu wrote:
> > The predictive commoning patch:
> >
> > http://gcc.gnu.org/ml/gcc-patches/2007-05/msg01061.html
> >
> > miscompiles 482.sphinx3 in SPEC CPU 2006 with -O2 -ffast-math on
> > Linux/x86-64.  Zdenek, do you have any ideas?
> >
>
> Something is wrong. Predictive commoning is supposed to be turned
> on at -O3. But it definitely afffects -O2. Why?

Because the patch had other effects like adding a DCE after Copyprop
in the loop optimizer section.

This actually speed up a couple of benchmarks in SPEC 2k too (mgrid
and apsi comes to mind).

Thanks,
Andrew Pinski