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Title: gh-99761: add invalid_index macro by eendebakpt · Pull Request #99762 · python/cpython · GitHub

Open Graph Title: gh-99761: add invalid_index macro by eendebakpt · Pull Request #99762 · python/cpython

X Title: gh-99761: add invalid_index macro by eendebakpt · Pull Request #99762 · python/cpython

Description: In listobject.c there is an optimization to check whether an index is valid (e.g. 0 <= index < N) using a single comparison. The cast-to-unsigned optimization is used in current main in 3 locations: tupleobject.c, _collectionsmodule.c and bytesobject.c. It is a micro optimization, but the code generated is different than the plain i < 0 || i >= Py_SIZE(a). This PR tries to: i) apply the optimization to more locations ii) make the code more consistent By replacing index checks with a single method _Py_is_valid_index that includes the optimization we have consistency in the code and have the optimized check for all index checks. Issue: gh-99761 Notes: The new method is private and is static inline (https://peps.python.org/pep-0670/) In bytecodes.c the optimized expression is used in three places. E.g. DEOPT_IF(((size_t)signed_magnitude) > 1, BINARY_SUBSCR); With the _Py_is_valid_index method it looks like DEOPT_IF(!_Py_is_valid_index(signed_magnitude, 2), BINARY_SUBSCR); which is in my opinion not very readable. For these cases a separate PR was created: #100064

Open Graph Description: In listobject.c there is an optimization to check whether an index is valid (e.g. 0 <= index < N) using a single comparison. The cast-to-unsigned optimization is used in current main in 3 loc...

X Description: In listobject.c there is an optimization to check whether an index is valid (e.g. 0 &lt;= index &lt; N) using a single comparison. The cast-to-unsigned optimization is used in current main ...

Opengraph URL: https://github.com/python/cpython/pull/99762

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