What do the “Not optimized” warnings in the Chrome Profiler mean?

Question

When I use the Developer Tools in Chrome to collect JavaScript CPU Profiles, I am getting two mysterious warnings on functions:

• Not optimized: optimized too many t

Answer 1

The first one is likely because the engine has optimised it, but then found the optimisation no good for some reason (maybe the return type varies over time, etc).

Enabling the flags --trace-opt and --trace-deopt should help you pinpoint.

My excuses if the links provided in the comments already pointed you there.