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by cfbolztereick 700 days ago
PyPy has formally verified the integer abstract domain using Z3, a quite important part of our jit optimizer (will write about that in the coming weeks).

We also run a fuzzer regularly to find optimization bugs, using Z3 as a correctness check:

https://pypy.org/posts/2022/12/jit-bug-finding-smt-fuzzing.h...

The peephole optimizations aren't themselves formally verified completely yet. We've verified the very simplest rules, and some of the newer complicated ones, but not systematically all of them. I plan to work on fully and automatically verifying all integer optimizations in the next year or so. But we'll see, I'll need to find students and/or money.