[hwpythonner]

Thanks — really appreciate your insights.

You're absolutely right that CPython bytecode changes over time and isn’t perfectly documented — I’ve also had to read the CPython source directly at times because of unclear docs.

That said, I intentionally chose to target bytecode instead of AST at this stage. Adhering to the AST would actually make me more vulnerable to changes in the Python language itself (new syntax, new constructs), whereas bytecode changes are usually contained to VM-level behavior. It also made it much easier early on, because the PyXL compiler behaves more like a simple transpiler — taking known bytecode and mapping it directly to PySM instructions — which made validation and iteration faster.

Either way, some adaptation will always be needed when Python evolves — but my goal is to eventually get to a point where only the compiler (the software part of PyXL) needs updates, while keeping the hardware stable.

[cchianel]

CPython bytecode changes behaviour for no reason and very suddenly, so you will be vulnerable to changes in Python language versions. A few from the top of my head:

- In Python 3.10, jumps changed from absolute indices to relative indices

- In Python 3.11, cell variables index is calculated differently for cell variables corresponding to parameters and cell variables corresponding to local variables

- In Python 3.11, MAKE_FUNCTION has the code object at the TOS instead of the qualified name of the function

For what it's worth, I created a detailed behaviour of each opcode (along with example Python sources) here: https://github.com/TimefoldAI/timefold-solver/blob/main/pyth... (for up to Python 3.11).