1  /* { dg-do compile } */
       2  /* { dg-options "-O -fdump-tree-fre1" } */
       3  
       4  int x;
       5  int foo (void)
       6  {
       7    x = 1;
       8    return __builtin_ffs (x);
       9  }
      10  
      11  /* { dg-final { scan-tree-dump-not "ffs" "fre1" } } */