Someone reported a scenario where compiling some code got slower from Erlang/OTP 21 to Erlang/OTP 23. I have isolated the code to the following Erlang file:
In my machine, it is about 7x faster to compile on Erlang/OTP 21 compared to Erlang/OTP 22. It is a bit faster on Erlang/OTP 23 (and even faster in master), but it is still 4x to 5x slower than what it was before.
Using the +time flag, we can see the majority of the time is spent on "ssa_opt_dead". I am not sure if there is something that could be done to speed it up but I thought I would open up a report in case it does reveal some pathological case. Feel free to close otherwise.