SpiderMonkey is Firefox’s JavaScript engine.  In Firefox 3.0 and earlier versions, it was just an interpreter.  In Firefox 3.5, a tracing JIT called TraceMonkey was added.  TraceMonkey was able to massively speed up certain parts of programs, such as tight loops;  parts of programs it couldn’t speed up continued to be interpreted.  TraceMonkey provided large … Continue reading You lose more when slow than you gain when fast