gcc/testsuite/gcc.dg/tree-ssa/ssa-ccp-38.c

/* { dg-do compile } */
/* { dg-options "-O -fdump-tree-ccp1" } */

int foo (_Bool x)
{
  _Bool t = 1;
  _Bool xx = !x;
  _Bool y = xx == t;
  _Bool z = y == x;
  return z ? 1 : 0;
}

/* { dg-final { scan-tree-dump "return 0;" "ccp1" } } */