https://github.com/python/cpython/commit/3d3a4beefed46df7aa3a477f2e511459ce06c4b0
commit: 3d3a4beefed46df7aa3a477f2e511459ce06c4b0
branch: main
author: Ken Jin <ken...@python.org>
committer: Fidget-Spinner <kenjin4...@gmail.com>
date: 2025-02-07T20:18:15+08:00
summary:
gh-128563: Document the tail-calling interpreter (GH-129728)
Co-authored-by: Hugo van Kemenade <1324225+hug...@users.noreply.github.com>
files:
M Doc/using/configure.rst
M Doc/whatsnew/3.14.rst
diff --git a/Doc/using/configure.rst b/Doc/using/configure.rst
index 629859e36cb654..101c43576b0314 100644
--- a/Doc/using/configure.rst
+++ b/Doc/using/configure.rst
@@ -618,6 +618,16 @@ also be used to improve performance.
Enable computed gotos in evaluation loop (enabled by default on supported
compilers).
+.. option:: --with-tail-call-interp
+
+ Enable interpreters using tail calls in CPython. If enabled, enabling PGO
+ (:option:`--enable-optimizations`) is highly recommended. This option
specifically
+ requires a C compiler with proper tail call support, and the
+ `preserve_none
<https://clang.llvm.org/docs/AttributeReference.html#preserve-none>`_
+ calling convention. For example, Clang 19 and newer supports this feature.
+
+ .. versionadded:: next
+
.. option:: --without-mimalloc
Disable the fast :ref:`mimalloc <mimalloc>` allocator
diff --git a/Doc/whatsnew/3.14.rst b/Doc/whatsnew/3.14.rst
index a95fc7a4b6a9fa..c788db31fc27ed 100644
--- a/Doc/whatsnew/3.14.rst
+++ b/Doc/whatsnew/3.14.rst
@@ -68,6 +68,7 @@ Summary -- release highlights
* :ref:`PEP 649: deferred evaluation of annotations <whatsnew314-pep649>`
* :ref:`PEP 741: Python Configuration C API <whatsnew314-pep741>`
* :ref:`PEP 761: Discontinuation of PGP signatures <whatsnew314-pep761>`
+* :ref:`A new tail-calling interpreter <whatsnew314-tail-call>`
New features
@@ -208,6 +209,30 @@ configuration mechanisms).
.. seealso::
:pep:`741`.
+.. _whatsnew314-tail-call:
+
+A new tail-calling interpreter
+------------------------------
+
+A new type of interpreter based on tail calls has been added to CPython.
+For certain newer compilers, this interpreter provides
+significantly better performance. Preliminary numbers on our machines suggest
+anywhere from -3% to 30% faster Python code, and a geometric mean of 9-15%
+faster on ``pyperformance`` depending on platform and architecture.
+
+This interpreter currently only works with Clang 19 and newer
+on x86-64 and AArch64 architectures. However, we expect
+that a future release of GCC will support this as well.
+
+This feature is opt-in for now. We highly recommend enabling profile-guided
+optimization with the new interpreter as it is the only configuration we have
+tested and can validate its improved performance.
+For further information on how to build Python, see
+:option:`--with-tail-call-interp`.
+
+(Contributed by Ken Jin in :gh:`128718`, with ideas on how to implement this
+in CPython by Mark Shannon, Garret Gu, Haoran Xu, and Josh Haberman.)
+
Other language changes
======================
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