I'm not sure, haven't looked at the codebases of old compilers in a long time. Definitely a lot of the language is pretty amenable to it, especially if you have unstructured jumps for e.g. the for advancement statement. I had a distinct feeling while writing the compiler every time I added a new feature that "wow, the semantics work exactly how I'd like them to for ease of implementation."

Compare that to, say, Rust, which would be pretty painful to single-pass compile with all the non-local behavior around traits.