If you declare a C++ virtual function final the compiler can avoid the virtual call table for any invocations of that function in the future on that object or any of its derivatives. Of course, you then cannot override it in child classes anymore.
If you declare a virtual function inline, if it is invoked from a well defined object (ie, not through a reference or pointer) you also get a similar effect while still being able to override, except the code is not a static call but is just inlined with that one implementation of the function.