The following testcase fails at -O3.  It succeeds at -O3 -fno-tree-fre -fno-tree-dominator-opts -fno-tree-pre


extern void abort (void);

int i;

int f (int *) __attribute((noinline));
int
f (int *p)
{
  int a, b;

  a = i;
  *p = 1;
  b = i;
  return a + b;
}

int
main (void)
{
  if (f (&i) != 1)
    abort ();
  return 0;
}