1  /* { dg-do compile } */
       2  /* { dg-options "-O -fdump-tree-ccp1" } */
       3  
       4  int foo (_Bool x)
       5  {
       6    _Bool t = 1;
       7    _Bool xx = !x;
       8    _Bool y = xx == t;
       9    _Bool z = y == x;
      10    return z ? 1 : 0;
      11  }
      12  
      13  /* { dg-final { scan-tree-dump "return 0;" "ccp1" } } */