[Bug tree-optimization/25643] VRP does not remove -fbounds-check for Fortran

["rguenth at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #12 from rguenth at gcc dot gnu dot org  2008-01-12 14:23 -------
Simplified C testcase (omitting the parts that are optimized).  We cannot
figure out the number of iterations of this loop:

void f(int n, float *v)
{
  int i;
  if (n <= 0)
    return;
  else
    {
      i = 1;
      do {
        if (i > n)  __builtin_abort ();

        v[i] = 0.;

        i++;
      } while (i <= n);
    }
}

Note that for this simplified testcase DOM figures out the redundant test,
but not if you use i != n as the exit test, as for n == 1 the assert
will trigger.  If you look at the fortran IL, it does instead

   } while (i++ != n);

which would be ok again, but is still not optimized.

Testcase:

extern void link_error (void);
int i, n;
int main()
{
  if (i > n)
    return;
  if (i != n)
    if (i >= n)
        link_error ();
}


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25643