Yes, except these are the devdocs for the current IR: https://docs.julialang.org/en/v1/devdocs/ssair/. I wrote that system about 10 years ago, but it was a bit of a rush job in the lead up to Julia 1.0 in order to be able to do some optimizations that we desperately needed to do. It's held up reasonably well, but it's definitely hit its limitations as Julia's popularity has continued to grow. There've been multiple downstream attempts to use it to do compiler-y things and they've all had middling success (including my own). I think the jankiness of the IR API played a role in that, so this is my attempt to try to start cleaning that up.