Implement Branch Prediction in IonMonkey

by Wei Wu for Mozilla

Profile guided branch prediction is a known optimization in compiler. As of today, nobody tried to take advantage of this optimization on JavaScript. The goal of this GSoC project is to analyze the benefit of such approach on JavaScript by implementing one in SpiderMonkey (Firefox's JavaScript Engine). The first step is to instrument the code generated by the baseline compiler to profile branches which are executed. Then use this information to reduce and improve IonMonkey's compilation by filtering out branches which are infrequently used.