I've been updating a small codegen since the 3.x days. There have been many API changes with major versions. That said, I always found it pretty easy to impleme

I've been updating a small codegen since the 3.x days. There have been many API changes with major versions. That said, I always found it pretty easy to implement the changes (something like a workday for my ~10k LLVM-interfacing LoC), and the changes tend to be such that once you get it to compile again, it just works as before. I think LLVM is an excellent demonstration of how to design and implement big systems well in C++, and as a part of that, they also do breaking changes pretty well.