[Bug tree-optimization/37449] [4.4 Regression] calculix gets wrong answer for -O1 -ffast-math

[rguenther at suse dot de]

------- Comment #19 from rguenther at suse dot de  2008-10-15 13:18 -------
Subject: Re:  [4.4 Regression] calculix gets
 wrong answer for -O1 -ffast-math

On Wed, 15 Oct 2008, dberlin at dberlin dot org wrote:

> 
> 
> ------- Comment #18 from dberlin at gcc dot gnu dot org  2008-10-15 13:06 -------
> Subject: Re:  [4.4 Regression] calculix gets wrong answer for -O1 -ffast-math
> 
> Making PRE do this is somewhat trivial.
> Just extend fully_constant_expression to fold builtins, like it used
> to, and it should just DTRT.

It already does (I fixed that recently), but we only phi-translate during 
insertion and we
don't insert for that case, as obviously there is no partial redundancy.

Richard.

> On Wed, Oct 15, 2008 at 5:38 AM, jakub at gcc dot gnu dot org
> <gcc-bugzilla@gcc.gnu.org> wrote:
> >
> >
> > ------- Comment #16 from jakub at gcc dot gnu dot org  2008-10-15 09:38 -------
> > After discussion with richi, I'd like to turn this into an enhancement request
> > for 4.5 to extend PRE/SCCVN to be able to optimize that:
> >  # cn_43 = PHI <-1.0e+0(4), 1.0e+0(3)>
> >  D.1267_44 = __builtin_pow (cn_43, 2.0e+0);
> > into a constant.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37449