public void setOperand(String var, String op){
        if(!Arrays.asList(inLables).contains(var)){
            return;
        }
        Operand pos = null;
        for( AbstractUnit unit : units){
            if(unit instanceof  InputPin){
                if(((InputPin)unit).name.equals(var)){
                    IInstructionUnit nextInst = ((IInstructionUnit)(((InputPin)unit).getNextUnit()));
                    nextInst.setOperand(var, unit.position.ordinal());
                    break;
                }
            }
        }

        ((IInstructionUnit)predUnits.get(var)).setOperand(var, pos.ordinal());
    }