[issue45439] [C API] Move usage of tp_vectorcall_offset from public headers to the internal C API

[STINNER Victor]

STINNER Victor <vstinner at python.org> added the comment:

I decided to merge my PR to address https://bugs.python.org/issue45439 initial issue: "[C API] Move usage of **tp_vectorcall_offset** from public headers to the internal C API".

Last years, I added `tstate` parameters to internal C functions. The agreement was that only internal functions should use it, and indirectly that this `tstate` parameter should be hidden. I'm now sure exactly, but `tstate` started to pop up in `Include/cpython/abstract.h` around "call" functions. This PR fix this issue.

About the impact on performances: well, it's really hard to draw a clear conclusion. Inlining, LTO and PGO give different results on runtime performance and stack memory usage.

IMO the fact that public C API functions are now regular functions should not prevent us to continue (micro) optimizing Python. We can always add a variant to the internal C API using an API a little bit different (e.g. add `tstate` parameter) or defined as a static inline function, rather than a regular function.

The unclear part is if PyObject_CallOneArg() (regular function call) is faster than _PyObject_CallOneArg() (static inline function, inlined). The performance may depend if it's called in the Python executable or in a dynamic library (PLT indirection which may be avoided by `gcc -fno-semantic-interposition`).

Well, happy hacking and let's continue *continuous* benchmarking Python!

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue45439>
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