I don't know what was put in the 1.9.20 special sauce, but for one of my projects, benchmarks for all targets are running almost 2x faster than 1.9.10 🎉

Which target? JVM?

JVM was pretty much the same. Mac, JS, Linux, and Windows all had vastly improved numbers.

Maybe the new memory allocator? https://kotlinlang.org/docs/whatsnew-eap.html#custom-memory-allocator-enabled-by-default

Doesn't explain JS, but native was doing better than JS so it could be that

out of curiosity, what kind of benchmarks are you seeing these large improvements on? is this for things like interoping with platform frameworks or more straightforward Kotlin stdlib code?

All stdlib code

awesome!