return false;
return op.isStringConstant() || op.isClassConstant();
  public static boolean isNonNull(OPT_Operand op) {    if (op instanceof OPT_RegisterOperand) {      OPT_RegisterOperand rop = (OPT_RegisterOperand)op;      if (VM.VerifyAssertions)        VM._assert((rop.scratchObject == null) ||                   (rop.scratchObject instanceof OPT_RegisterOperand) ||                   (rop.scratchObject instanceof OPT_TrueGuardOperand));      return rop.scratchObject != null;    } else if (op instanceof OPT_StringConstantOperand) {      return true;    } else {      return false;    }  }