Comment by Rochus

Several historical design choices within the IR itself have created immense complexity, leading to unsound optimizations and severe compile-time bloat. It's not high-level enough so you e.g. don't have to care about ABI details, and it's not low-level enought to actually take care of those ABI details in a decent way. And it's a continuous moving target. You cannot implement something which then continus to work.