http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46675
--- Comment #12 from Richard Guenther <rguenth at gcc dot gnu.org> 2010-11-27
22:20:13 UTC ---
(In reply to comment #11)
> (In reply to comment #9)
>
> >
> > Testcase:
> >
> > volatile int j;
> > int __attribute__((noinline))
> > foo(int n)
> > {
> > int i = 0, npairs;
> > npairs = n - (- __INT_MAX__ - 1);
> > if (npairs > 0)
> > {
> > do
> > {
> > ++j;
> > i = i + 1;
> > }
> > while (i < npairs);
> > }
> > return 0;
> > }
> > extern void abort (void);
> > int main()
> > {
> > j = 0;
> > foo (- __INT_MAX__ - 1 + 5);
> > if (j != 5)
> > abort ();
> > return 0;
> > }
> >
> > is optimized to an endless loop by the first VRP pass.
>
> It is caused by revision 163724:
>
> http://gcc.gnu.org/ml/gcc-cvs/2010-09/msg00015.html
It surely has exposed it - before that patch VRP didn't use number of
iteration analysis. Wheter that was correct at any point remains an
open question.
