The slowest part is the LLVM passes. typecheck isn't very fast either, but it can be parallelized and it's much faster than the LLVM part. We don't really do a

The slowest part is the LLVM passes. typecheck isn't very fast either, but it can be parallelized and it's much faster than the LLVM part. We don't really do any optimizations on the Rust side and just hand over IR to LLVM. This IR isn't of the type LLVM was built to deal with (pervasive noalias, lots of iterators, etc). It can optimize it, just that it's slow. We can work on giving better IR there. So type check is slow, but it isn't the reason we're slow. (Still, improvements to type check will help)