return UNCHANGED;
return DefUseEffect.UNCHANGED;
  private static byte mustImplementInterface(OPT_Instruction s) {    OPT_Operand ref = TypeCheck.getRef(s);    if (VM.VerifyAssertions) VM._assert(!ref.isNullConstant());           VM_TypeReference lhsType = TypeCheck.getType(s).getTypeRef(); // the interface that must be implemented    VM_TypeReference rhsType = ref.getType();                     // our type    byte ans = OPT_ClassLoaderProxy.includesType(lhsType, rhsType);    if (ans == OPT_Constants.YES) {      Empty.mutate(s, NOP);      return REDUCED;    } else if (ans == OPT_Constants.NO) {      VM_Type rType = rhsType.peekResolvedType();      if (rType != null && rType.isClassType() && rType.asClass().isFinal()) {        // only final (or precise) rhs types can be optimized since rhsType may be conservative        Trap.mutate(s, TRAP, null, OPT_TrapCodeOperand.MustImplement());        return TRAP_REDUCED;      }    }    return UNCHANGED;  }