> I don't quite see how it can be architecture independent if it doesn't do register allocation. Does it use a small fixed amount of virtual registers which work on every target? Or does it spill virtual registers to memory if required?

If it's low level and platform independent, that probably means more that it provides the tools to the user to work on many platforms, rather than it does the work for many platforms for the user.

Jit libraries like this are building blocks, not a turnkey interpreter to native execution pipeline.