[Bug fortran/69368] [6 Regression] spec2006 test case 416.gamess fails with the g++ 6.0 compiler starting with r232508

["rguenther at suse dot de" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69368

--- Comment #48 from rguenther at suse dot de <rguenther at suse dot de> ---
On Thu, 18 Feb 2016, rguenther at suse dot de wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69368
> 
> --- Comment #46 from rguenther at suse dot de <rguenther at suse dot de> ---
> On Thu, 18 Feb 2016, jakub at gcc dot gnu.org wrote:
> 
> > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69368
> > 
> > --- Comment #45 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
> > Consider e.g. one source file
> >       INTEGER FOO
> >       COMMON /BLK/ K(64)
> >       DO I=1,64
> >       K(I)=1
> >       END DO
> >       IF (FOO(5,12).NE.51) CALL ABORT
> >       END
> > and another one:
> >       FUNCTION FOO(I, J)
> >       COMMON /BLK/ K(1)
> >       FOO = K(I) + K(J) + K(2*I) + K(2*J)
> >       END FUNCTION
> > If the second source file is compiled with -O2, it will return "wrong" value,
> > as if all accesses to K were using the same index (because the only valid index
> > is 1).  If you compile with -O2 -fno-tree-dominator-opts, then it "works".
> 
> Which is odd since FRE already should optimize it that way.

Ok, it does not.  Supposedly more complicated situations are needed to
trigger sth wrong in FRE.