[Bug tree-optimization/23821] New: Dom creating harder to optimize code

["rakdver at gcc dot gnu dot org"]

Dom transforms the following testcase:

static int a[199];

int
main ()
{
  int i, x;
  for (i = 0; i < 199; i++)
    {
      x = a[i];
      if (x != i)
        abort ();
    }
  return 0;
}

to

int
main ()
{
  int i;
  for (i = 0; i < 199; i = x + 1)
    {
      x = a[i];
      if (x != i)
        abort ();
    }
  return 0;
}

Now we are not able to determine that i is an induction variable.

-- 
           Summary: Dom creating harder to optimize code
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rakdver at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23821