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gh-139922: Add tail call for MSVC for whats new in 3.15 #143087

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Fidget-Spinner merged 3 commits into from
Dec 22, 2025
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gh-139922: Add tail call for MSVC for whats new in 3.15 #143087

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Add tail call for MSVC for whats new in 3.15
Fidget-Spinner Dec 22, 2025
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Fidget-Spinner Dec 22, 2025
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Fidget-Spinner Dec 22, 2025
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10 changes: 10 additions & 0 deletions Doc/whatsnew/3.15.rst
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Expand Up @@ -849,6 +849,16 @@ zlib
Optimizations
=============

* Builds using Visual Studio 2026 (MSVC 18) may now use the new
:ref:`tail-calling interpreter <whatsnew314-tail-call-interpreter>`.
Results on an early experimental MSVC compiler reported roughly 15% speedup
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@pablogsal pablogsal Dec 22, 2025

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is there a way to clarify the experimental version this was measured in (i.e. put the version or whatever in parens)

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@Fidget-Spinner Fidget-Spinner Dec 22, 2025

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Good point. As far as I understand, it was an internal MSVC build in MS, which I can't access, so we will never know :(.

on the geometric mean of pyperformance on Windows x86-64 over
the switch-case interpreter. We have
observed speedups ranging from 15% for large pure-Python libraries
to 40% for long-running small pure-Python scripts on Windows.
(Contributed by Chris Eibl, Ken Jin, and Brandt Bucher in :gh:`143068`.
Special thanks to the MSVC team including Hulon Jenkins.)

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