>I wasted a handful of weeks digging around in debug builds looking at bailout log entries and trying to decipher their IR using the broken log viewer they reco

>I wasted a handful of weeks digging around in debug builds looking at bailout log entries and trying to decipher their IR using the broken log viewer they recommend, and the net result was that my code ended up faster for a few weeks until V8 changed again. You have the same problem with any other modern JavaScript VM. There is always lots of magic and some heuristics which can easily break. As a result, performance is hard to predict. For what it's worth, Dart fixed that. Predictable performance was one of its main goals/constrains.