/**
     * Function to resolve BoolExpr recursively, returning all arguments of the given
     * expression in the form of reg-value pairs
     * @return HashMap of [Register | constraint_value] pairs
     * */
    public HashMap getRegisterConstraintPairs(BoolExpr expr){
        HashMap constraintArgs=new HashMap();
        getInvdividualConsArgsHelper(expr,constraintArgs);
        return  constraintArgs;

    }

    private void getInvdividualConsArgsHelper(Expr expr, HashMap constraintArgs){
        try {

            if(expr.getNumArgs()<=1) return;
                //if this expression has less than 2 arguments then it must be a part of reg-value pair,
                //meaning we have gone deeper than we should, so we return to add its super expression

            if(expr.getArgs()[0].getNumArgs()<2)
                //if this expression is in the form of [register | value] pair, we add it as a key-value pair
            {
                constraintArgs.put(expr.getArgs()[0], expr.getArgs()[1]);
                return;
            }

            for(int i=0 ; i<expr.getArgs().length; ++i){

                //for all sub expressions in this argument, apply same rule
                getInvdividualConsArgsHelper(expr.getArgs()[i],constraintArgs);
            }

        }catch (Z3Exception e){

            e.printStackTrace();
        }

    }