: Object-oriented programs are difficult to optimize because they execute many dynamically-dispatched calls. These calls cannot easily be eliminated because the compiler does not know which callee will be invoked at runtime. We have developed a simple technique that feeds back type information from the runtime system to the compiler. With this type feedback, the compiler can inline any dynamically-dispatched call. Our compiler drastically reduces the call frequency of a suite of large SELF applications (by a factor of 3.6) and improves performance by a factor