YJIT has functionality to record the Ruby source of a compiled method and then dump it into a Marshal format (serialized Ruby object) to be consumed in https://github.com/tmm1/stackprof.

This could be very useful to port to ZJIT (or rewrite) in order to determine what kind of instructions are frequently causing side-exits. (Which slow down execution.)

Tentatively, I plan to read the source that defines --yjit-trace-exits and determine the design decisions made when implementing it, then mapping those over to the decisions made for ZJIT.

(This is a proposal in which I would love feedback as to whether this is a reasonable choice or not.)