In my uninformed opinion it's like the SIMD discussion from yesterday. Without their fancy SIMD library, the optimization [`sqrt(x) * sqrt(x)` === x] gets lost

In my uninformed opinion it's like the SIMD discussion from yesterday. Without their fancy SIMD library, the optimization [`sqrt(x) * sqrt(x)` === x] gets lost in a sea of C++ template incantations when using that SIMD library. Similarly, perhaps, if there's some fancy observation of an invariant that can be made about `*.map(...)` that gets "lost in the sauce" once it's been lowered to the typical push/pop/loop mechanisms, then those higher level optimizations are better done in a language specific IR, not the "default" IR. It's actually IR's all the way down if you think about it...