When can the C++ compiler devirtualize a call?

Modern C++ compilers can devirtualize virtual function calls in two main scenarios: when they can prove the exact dynamic type of an object instance through dataflow analysis, or when they can prove "leafness" by determining that no class in the program can override a method (such as through final declarations or internal linkage). However, different compilers handle these optimizations inconsistently, with even simple cases sometimes fooling certain compilers like MSVC and ICC, while GCC and Clang tend to catch more corner cases.