Removing checks in dynamically typed languages through efficient profiling

Dynamically typed languages increase programmer's productivity at the expense of some runtime overheads to manage the types of variables, since they are not declared at compile time and can change at runtime. One of the most important overheads is due to very frequent checks that are introduced in the specialized code to identify the type of the variables. In this paper, we present a HW/SW hybrid mechanism that allows the removal of checks executed in the optimized code by performing a HW profiling of the types of object variables. To demonstrate the benefits of the proposed technique, we implement it in a JavaScript engine and show that it produces 7.1% speedup on average for optimized JavaScript code (up to 34% for some applications) and 6.5% energy reduction.