It is almost possible to compile the RTS with the native code generator. What is missing is support for loops: code generated by GHC doesn't normally contain loops (or rather, loops are explicit as jumps to top-level labels), but the RTS code does contain some loops. The register allocator in particular will need some work. There's nothing fundamentally difficult here, and it doesn't need to do a fantastic job, just a half-decent one. The code to be compiled in the RTS isn't performance-critical.