GH-133231: Add JIT utilities in sys._jit
#133233
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Doc/library/sys.rst
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| Return ``True`` if the topmost Python frame is currently executing JIT | ||
| code, and ``False`` otherwise. | ||
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| .. note:: | ||
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| Due to the nature of tracing JIT compilers, repeated calls to this | ||
| function may give surprising results. For example, branching on its | ||
| return value will likely lead to unexpected behavior (if doing so | ||
| causes JIT code to be entered or exited): |
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I think this section should have more emphasis that this is mainly for testing/debugging, per your rationale in Discourse:
- It seems useful for tests for the JIT itself.
- Lots of people have asked: “How do I know if the JIT is actually working?”
I would also suggest upgrading the 'note' about branching to a 'warning', if nothing else changes.
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I had thought that "warning" was reserved for security issues, or possible misuse of an API that could corrupt interpreter state or lead to crashes. This is just saying "the results may not be what you expect". Is a warning more appropriate than a note for calling out quirks like this?
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How's adding this to the top of the note:
This function is intended for testing and debugging the JIT itself. Beyond using it to confirm that the JIT is actually working, most users will never need to use it.
| .. envvar:: PYTHON_JIT | ||
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| On builds where experimental just-in-time compilation is available, this | ||
| variable can force the JIT to be disabled (``0``) or enabled (``1``) at | ||
| interpreter startup. | ||
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| .. versionadded:: 3.13 |
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We should backport this, should it be split out into a different PR for ease?
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We can just backport it separately, since I need the ref for this PR's changes.
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I just realized that my approach for |
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Okay, reworked to support tail-calling. |
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@markshannon, let me know what you think. The bots won't let us merge features without approving review, but I'd like to get something like this in before the freeze. |
sys._jit#133231📚 Documentation preview 📚: https://cpython-previews--133233.org.readthedocs.build/