How does the PyPy JIT compare to the JIT in the upcoming CPython 3.13?
The CPython JIT is a newer and less invasive technique called copy-and-patch[1]. It's a lot less powerful, but a lot easier to plug into an existing language implementation: known sequences of python bytecode are mapped to templates of machine code
I understand people at IBM were doing it industrially for Java bytecode in the late 90s under the name quasi-static compilation, and the DyC/Tempo folks were doing similar things over in C land under different names. There were some minor differences due to the technology of the day, but it was broadly similar. For example, explicitly building to IR was uncommon outside Java land and register scheduling didn't have a lot of choices to make. The Java stuff even allowed the template specializations to exist on other computers and be dynamically loaded and validated over the network, for thin-client reasons. Very cool for the early 2000s.