What are the benefits to passing integral types by const ref

Question

The question: Is there benefit to passing an integral type by const reference as opposed to simply by value.

ie.

void foo(const int& n); // case #1
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Answer 1

It's not only performance. A true story: this week I noticed that a colleague tried to improve upon the Numerical Recipes and replaced the macro

    #define SHFT(a,b,c,d) do { (a)=(b); (b)=(c); (c)=(d); } while (0)

by this function

    inline void Rotate(double& dFirst, double& dSecond, double& dThird, const double dNewValue)
    {
        dFirst = dSecond;
        dSecond = dThird;
        dThird = dNewValue;
    }   // Function Rotate

This would have worked, if he had passed the last parameter by reference, but as it is, this code

 
        Rotate(dum,*fb,*fa,dum);

which was supposed to swap *fa and *fb no longer works. Passing it by reference without const is not possible, as in other places non-l-values are passed to the last parameter.