Well, the optimizing pipeline has completely changed in V8 5.8 (if you use `--turbo --ignition`) and in 5.9+. It's been simplified and most importantly, does not deoptimize on quite so many common features (such as try/catch). More information at http://benediktmeurer.de/2017/03/01/v8-behind-the-scenes-feb... and some of his other articles.

In my testing it appears that TurboFan cannot optimize certain patterns as well as Crankshaft did, but there's no reason to believe those regressions will remain as TF evolves. Optimizing more code is much more important for real apps.