return UNCHANGED;
return DefUseEffect.UNCHANGED;
  private static byte refAnd(OPT_Instruction s) {   if (CF_ADDR) {      canonicalizeCommutativeOperator(s);      OPT_Operand op1 = Binary.getVal1(s);      OPT_Operand op2 = Binary.getVal2(s);      if (op1.similar(op2)) {        // THE SAME OPERAND: x & x == x        Move.mutate(s, REF_MOVE, Binary.getClearResult(s),                     Binary.getClearVal1(s));        return op1.isConstant() ? MOVE_FOLDED : MOVE_REDUCED;      }      if (op2.isAddressConstant()) {        Word val2 = op2.asAddressConstant().value.toWord();        if (op1.isAddressConstant()) {          // BOTH CONSTANTS: FOLD          Word val1 = op1.asAddressConstant().value.toWord();          Move.mutate(s, REF_MOVE, Binary.getClearResult(s), AC(val1.and(val2).toAddress()));          return MOVE_FOLDED;        } else {          // ONLY OP2 IS CONSTANT: ATTEMPT TO APPLY AXIOMS          if (val2.isZero()) {                  // x & 0 == 0            Move.mutate(s, REF_MOVE, Binary.getClearResult(s), AC(Address.zero()));            return MOVE_FOLDED;          }          if (val2.isMax()) {                 // x & -1 == x & 0xffffffff == x            Move.mutate(s, REF_MOVE, Binary.getClearResult(s),                         Binary.getClearVal1(s));            return MOVE_REDUCED;          }        }      }    }    return UNCHANGED;  }