private static byte call(OPT_Instruction s) {
private static DefUseEffect call(OPT_Instruction s) {
  private static byte call(OPT_Instruction s) {    if (CF_FIELDS) {      OPT_MethodOperand methOp = Call.getMethod(s);      if ((methOp != null) && methOp.isVirtual() && !methOp.hasPreciseTarget()) {        OPT_Operand calleeThis = Call.getParam(s, 0);        if (calleeThis.isNullConstant()) {          Trap.mutate(s, TRAP, NullCheck.getClearGuardResult(s),                      OPT_TrapCodeOperand.NullPtr());          return TRAP_REDUCED;        }        else if(calleeThis.isConstant() || calleeThis.asRegister().isPreciseType()) {          VM_TypeReference calleeClass = calleeThis.getType();          if (calleeClass.isResolved()) {            methOp.refine(calleeClass.peekResolvedType());            return REDUCED;          }        }      }    }    return UNCHANGED;  }