Comment by gopalv

> but it claims to be a tutorial.

This is, but only for someone who wants to do JIT work without writing assembly code, but can read assembly code back into C (or can automate that part).

Instead of doing all manual register allocations in the JIT, you get to fill in the blanks with the actual inputs after a more (maybe) diligent compiler has allocated the registers, pushed them and all that.

There's a similar set of implementation techniques in Apache Impala, where the JIT only invokes the library functions when generating JIT code, instead of writing inline JIT operations, so that they can rely on shorter compile times for the JIT and deeper optimization passes for the called functions.