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GH-113464: Add the JIT to What's New (GH-133486)

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19
Doc/using/configure.rst
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@ -302,14 +302,21 @@ General Options
.. option:: --enable-experimental-jit=[no|yes|yes-off|interpreter]
Indicate how to integrate the :ref:`JIT compiler <whatsnew313-jit-compiler>`.
Indicate how to integrate the :ref:`experimental just-in-time compiler <whatsnew314-jit-compiler>`.
* ``no`` - build the interpreter without the JIT.
* ``yes`` - build the interpreter with the JIT.
* ``yes-off`` - build the interpreter with the JIT but disable it by default.
* ``interpreter`` - build the interpreter without the JIT, but with the tier 2 enabled interpreter.
* ``no``: Don't build the JIT.
* ``yes``: Enable the JIT. To disable it at runtime, set the environment
variable :envvar:`PYTHON_JIT=0 <PYTHON_JIT>`.
* ``yes-off``: Build the JIT, but disable it by default. To enable it at
runtime, set the environment variable :envvar:`PYTHON_JIT=1 <PYTHON_JIT>`.
* ``interpreter``: Enable the "JIT interpreter" (only useful for those
debugging the JIT itself). To disable it at runtime, set the environment
variable :envvar:`PYTHON_JIT=0 <PYTHON_JIT>`.
By convention, ``--enable-experimental-jit`` is a shorthand for ``--enable-experimental-jit=yes``.
``--enable-experimental-jit=no`` is the default behavior if the option is not
provided, and ``--enable-experimental-jit`` is shorthand for
``--enable-experimental-jit=yes``. See :file:`Tools/jit/README.md` for more
information, including how to install the necessary build-time dependencies.
.. note::

31
Doc/whatsnew/3.14.rst
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@ -77,6 +77,7 @@ Summary -- release highlights
:ref:`argparse <whatsnew314-color-argparse>`,
:ref:`json <whatsnew314-color-json>` and
:ref:`calendar <whatsnew314-color-calendar>` CLIs
* :ref:`Binary releases for the experimental just-in-time compiler <whatsnew314-jit-compiler>`
Incompatible changes
@ -715,6 +716,36 @@ in the :envvar:`PYTHONSTARTUP` script.
(Contributed by Łukasz Langa in :gh:`131507`.)
.. _whatsnew314-jit-compiler:
Binary releases for the experimental just-in-time compiler
----------------------------------------------------------
The official macOS and Windows release binaries now include an *experimental*
just-in-time (JIT) compiler. Although it is **not** recommended for production
use, it can be tested by setting :envvar:`PYTHON_JIT=1 <PYTHON_JIT>` as an
environment variable. Downstream source builds and redistributors can use the
:option:`--enable-experimental-jit=yes-off` configuration option for similar
behavior.
The JIT is at an early stage and still in active development. As such, the
typical performance impact of enabling it can range from 10% slower to 20%
faster, depending on workload. To aid in testing and evaluation, a set of
introspection functions has been provided in the :data:`sys._jit` namespace.
:func:`sys._jit.is_available` can be used to determine if the current executable
supports JIT compilation, while :func:`sys._jit.is_enabled` can be used to tell
if JIT compilation has been enabled for the current process.
Currently, the most significant missing functionality is that native debuggers
and profilers like ``gdb`` and ``perf`` are unable to unwind through JIT frames
(Python debuggers and profilers, like :mod:`pdb` or :mod:`profile`, continue to
work without modification). Free-threaded builds do not support JIT compilation.
Please report any bugs or major performance regressions that you encounter!
.. seealso:: :pep:`744`
Other language changes
======================

6
Tools/jit/README.md
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@ -54,13 +54,13 @@ choco install llvm --version=19.1.0
## Building
For `PCbuild`-based builds, pass the new `--experimental-jit` option to `build.bat`.
For `PCbuild`-based builds, pass the `--experimental-jit` option to `build.bat`.
For all other builds, pass the new `--enable-experimental-jit` option to `configure`.
For all other builds, pass the `--enable-experimental-jit` option to `configure`.
Otherwise, just configure and build as you normally would. Cross-compiling "just works", since the JIT is built for the host platform.
The JIT can also be enabled or disabled using the `PYTHON_JIT` environment variable, even on builds where it is enabled or disabled by default. More details about configuring CPython with the JIT and optional values for `--enable-experimental-jit` can be found [here](https://docs.python.org/dev/whatsnew/3.13.html#experimental-jit-compiler).
The JIT can also be enabled or disabled using the `PYTHON_JIT` environment variable, even on builds where it is enabled or disabled by default. More details about configuring CPython with the JIT and optional values for `--enable-experimental-jit` can be found [here](https://docs.python.org/dev/using/configure.html#cmdoption-enable-experimental-jit).
[^pep-744]: [PEP 744](https://peps.python.org/pep-0744/)