Polyhedron performance regression

[Richard Guenther]

On 11/13/06, Paul Richard Thomas <paul.richard.thomas@gmail.com> wrote:
> FX,
> >
> >
> > I'm ashamed that revision 118492
> > (http://gcc.gnu.org/viewcvs?view=rev&revision=118492), which
> > introduced this performance regression, is the MOD/MODULO patch by
> > Paul Thomas and myself.
>
> I realised from looking at the code for ac.f90, whilst on the plane last
> night, that this must be the case.  ac.f90 hinges on the random number
> generator, which uses MOD.
>
> I don't think that we should be ashamed about it.  32bit systems are
> fine; I checked the Polyhedron suite before submitting and was
> disappointed that it seemed to have little or no effect, other than
> correcting the original PR!
>
> Evidently there is something not very clever with the 64bit library.
> Can Uros advise, please?  In fact, is there a -ffast-math version
> available or is it resorting to the ordinary library version?  Detecting
> the presence or not of the fast version, was what stopped me from
> implementing this patch for so long.

I bet we are missing an inline x86_64 variant.  But it should be not too
hard to implement.

Richard.