I don't know a lot about the Java JIT. But my guess is that the scenario you observed is the result of profile-guided optimisations done at runtime. Hopefully

I don't know a lot about the Java JIT. But my guess is that the scenario you observed is the result of profile-guided optimisations done at runtime. Hopefully this is a feature that can be disabled when you want deterministic behaviour. There's no reason to make it mandatory in a well-engineered VM.