[Bug rtl-optimization/50904] [4.7 regression] pessimization when -fno-protect-parens is enabled by -Ofast

[rguenther at suse dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50904

--- Comment #31 from rguenther at suse dot de <rguenther at suse dot de> 2011-12-02 16:32:52 UTC ---
On Fri, 2 Dec 2011, burnus at gcc dot gnu.org wrote:

> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50904
> 
> --- Comment #30 from Tobias Burnus <burnus at gcc dot gnu.org> 2011-12-02 16:29:46 UTC ---
> (In reply to comment #29)
> > And for the sake of completeness the evaluation of sub above and
> >      x = (x + 2.d0**52) - 2.d0**52
> > should behave consistently if I read your Fortran standard
> > quotations correctly.
> 
> Well, it kind of does, only when mixing (in GCC) -funsafe-math-optimizations
> with -fprotect-parens or (in ifort) "-assume protect_parens" with a non-strict
> -fp-model, you get a different results: 1.0 with the () version and 1.3 with
> the 'tmp' version.

Ok, which is, I suppose, a bug in both compilers.

Richard.