VAlue/Purpose of __attribute((const)) in gcc c++

Is there any value in using __attribute((const)) in gcc for c++ programs when declaring functions or static members that the compiler can see do not access global memory?

For example,

int Add( int x , int y ) __attribute((const))
{
    return x+y;
}

The compiler knows that this function is limited in its scope of memory access. Does the attribute add anything? If so, what?

Thanks,

Josh