Sayonara, V8
The V8 team's anti-documentation culture is kind of problematic. As a compiler author targeting JS, it's been consistently difficult to figure out what kind of patterns V8 optimizes for, what patterns cause problems, and what the hell is going on inside their runtime. The rapid pace of changes to V8 - both new feature additions and system overhauls - means that if you're maintaining a complex project that interacts with V8, you're going to have a really hard time.They barely document their engine internals or debugging tools, things change randomly making the existing documentation incorrect, and they frequently break the user-facing development tools like Chrome's JS debugger.The only good things I can really say are that when V8 works, it works marvelously, and that if you can somehow track down a V8 developer they're usually incredibly helpful. Regardless, having to head over to the Google campus and buy a dev coffee isn't a scalable solution to these kinds of problems.I've basically given up on delivering good performance in V8 as a result. The cost is too high. If I see obvious bottlenecks in their profiler (when it works at all), I tune them, but that's about it. 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. Not worth it.P.S. When I say 'anti-documentation culture', I mean it. V8 devs have personally told me they dislike documenting certain aspects of V8 and its internals because they fear that end-users and developers will rely on those internals. They lean towards occasional blog posts and Google IO presentation videos to pick up the slack.