[ATsch]

Last I heard, the biggest source of compile time in rustc is emitting absolutely enormous amounts of LLVM IR and leaning on aggressive low-level LLVM optimisation passes to clean things up. There are efforts to make most of these optimisations earlier that have been landing in recent releases, but I'm not sure what the overall state of it is.

[swsieber]

I they have started doing work on that? I can't recall what it was exactly, but there was one constant or number (I'm so good at being specific) related one that did the optimization on the rust side instead of on LLVM's side.

[steveklabnik]

https://blog.rust-lang.org/inside-rust/2019/12/02/const-prop...