I believe the Bit Estimator example could be better:

  int test(unsigned char a) {
    short b = a;    // b: 00000000________, a: ________ 
    b <<= 4;        // b: 0000________0000 
    b |= 3;         // b: 0000________0011
    return b != 0;  // -> return true   
  }

The analyzer doesn't need any information about the two low bits of b to know b != 0. Had it been b ^= 3 instead of b |= 3, it would be a different matter.