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

When writing or using templates, you may end up with (const int &) because the template writer can't know what the type actually is. If the object is heavyweight, passing a reference is the right thing to do; if it's an int or something, the compiler may be able to optimize it away.

In the absence of some kind of external requirement, there is generally no reason to do something like this for a one-off function -- it's just extra typing, plus throwing around references actually tends to inhibit optimization. Copying small data in registers is much cheaper than reloading it from memory in case it's changed!