10000 GH-133231: Add JIT utilities in sys._jit (GH-133233) · python/cpython@b1aa515 · GitHub
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GH-133231: Add JIT utilities in sys._jit (GH-133233)
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‎Doc/library/sys.rst

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@@ -1282,6 +1282,64 @@ always available. Unless explicitly noted otherwise, all variables are read-only
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.. versionadded:: 3.5
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.. data:: _jit
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Utilities for observing just-in-time compilation.
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.. impl-detail::
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JIT compilation is an *experimental implementation detail* of CPython.
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``sys._jit`` is not guaranteed to exist or behave the same way in all
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Python implementations, versions, or build configurations.
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.. versionadded:: next
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.. function:: _jit.is_available()
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Return ``True`` if the current Python executable supports JIT compilation,
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and ``False`` otherwise. This can be controlled by building CPython with
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the ``--experimental-jit`` option on Windows, and the
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:option:`--enable-experimental-jit` option on all other platforms.
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.. function:: _jit.is_enabled()
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Return ``True`` if JIT compilation is enabled for the current Python
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process (implies :func:`sys._jit.is_available`), and ``False`` otherwise.
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If JIT compilation is available, this can be controlled by setting the
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:envvar:`PYTHON_JIT` environment variable to ``0`` (disabled) or ``1``
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(enabled) at interpreter startup.
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.. function:: _jit.is_active()
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Return ``True`` if the topmost Python frame is currently executing JIT
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code (implies :func:`sys._jit.is_enabled`), and ``False`` otherwise.
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.. note::
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This function is intended for testing and debugging the JIT itself.
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It should be avoided for any other purpose.
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.. note::
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Due to the nature of tracing JIT compilers, repeated calls to this
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function may give surprising results. For example, branching on its
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return value will likely lead to unexpected behavior (if doing so
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causes JIT code to be entered or exited):
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.. code-block:: pycon
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>>> for warmup in range(BIG_NUMBER):
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... # This line is "hot", and is eventually JIT-compiled:
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... if sys._jit.is_active():
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... # This line is "cold", and is run in the interpreter:
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... assert sys._jit.is_active()
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...
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Traceback (most recent call last):
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File "<stdin>", line 5, in <module>
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assert sys._jit.is_active()
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~~~~~~~~~~~~~~~~~~^^
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AssertionError
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.. data:: last_exc
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This variable is not always defined; it is set to the exception instance

‎Doc/using/cmdline.rst

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@@ -1279,6 +1279,14 @@ conflict.
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.. versionadded:: 3.14
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.. envvar:: PYTHON_JIT
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On builds where experimental just-in-time compilation is available, this
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variable can force the JIT to be disabled (``0``) or enabled (``1``) at
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interpreter startup.
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.. versionadded:: 3.13
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Debug-mode variables
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~~~~~~~~~~~~~~~~~~~~
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‎Lib/test/libregrtest/utils.py

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@@ -335,43 +335,11 @@ def get_build_info():
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build.append('with_assert')
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# --enable-experimental-jit
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tier2 = re.search('-D_Py_TIER2=([0-9]+)', cflags)
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if tier2:
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tier2 = int(tier2.group(1))
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if not sys.flags.ignore_environment:
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PYTHON_JIT = os.environ.get('PYTHON_JIT', None)
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if PYTHON_JIT:
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PYTHON_JIT = (PYTHON_JIT != '0')
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else:
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PYTHON_JIT = None
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if tier2 == 1: # =yes
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if PYTHON_JIT == False:
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jit = 'JIT=off'
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else:
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jit = 'JIT'
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elif tier2 == 3: # =yes-off
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if PYTHON_JIT:
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jit = 'JIT'
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if sys._jit.is_available():
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if sys._jit.is_enabled():
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build.append("JIT")
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else:
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jit = 'JIT=off'
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elif tier2 == 4: # =interpreter
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if PYTHON_JIT == False:
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jit = 'JIT-interpreter=off'
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else:
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jit = 'JIT-interpreter'
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elif tier2 == 6: # =interpreter-off (Secret option!)
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if PYTHON_JIT:
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jit = 'JIT-interpreter'
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else:
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jit = 'JIT-interpreter=off'
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elif '-D_Py_JIT' in cflags:
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jit = 'JIT'
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else:
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jit = None
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if jit:
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build.append(jit)
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build.append("JIT (disabled)")
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# --enable-framework=name
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framework = sysconfig.get_config_var('PYTHONFRAMEWORK')

‎Lib/test/support/__init__.py

Lines changed: 3 additions & 7 deletions
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@@ -2648,13 +2648,9 @@ def exceeds_recursion_limit():
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Py_TRACE_REFS = hasattr(sys, 'getobjects')
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try:
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from _testinternalcapi import jit_enabled
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except ImportError:
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requires_jit_enabled = requires_jit_disabled = unittest.skip("requires _testinternalcapi")
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else:
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requires_jit_enabled = unittest.skipUnless(jit_enabled(), "requires JIT enabled")
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requires_jit_disabled = unittest.skipIf(jit_enabled(), "requires JIT disabled")
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_JIT_ENABLED = sys._jit.is_enabled()
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requires_jit_enabled = unittest.skipUnless(_JIT_ENABLED, "requires JIT enabled")
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requires_jit_disabled = unittest.skipIf(_JIT_ENABLED, "requires JIT disabled")
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_BASE_COPY_SRC_DIR_IGNORED_NAMES = frozenset({

‎Lib/test/test_capi/test_misc.py

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@@ -306,7 +306,7 @@ def test_getitem_with_error(self):
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CURRENT_THREAD_REGEX +
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r' File .*, line 6 in <module>\n'
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r'\n'
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r'Extension modules: _testcapi, _testinternalcapi \(total: 2\)\n')
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r'Extension modules: _testcapi \(total: 1\)\n')
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else:
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# Python built with NDEBUG macro defined:
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# test _Py_CheckFunctionResult() instead.

‎Lib/test/test_dis.py

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@@ -1336,7 +1336,7 @@ def test_loop_quicken(self):
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# Loop can trigger a quicken where the loop is located
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self.code_quicken(loop_test)
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got = self.get_disassembly(loop_test, adaptive=True)
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jit = import_helper.import_module("_testinternalcapi").jit_enabled()
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jit = sys._jit.is_enabled()
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expected = dis_loop_test_quickened_code.format("JIT" if jit else "NO_JIT")
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self.do_disassembly_compare(got, expected)
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‎Lib/test/test_sys.py

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@@ -2196,6 +2196,64 @@ def test_remote_exec_in_process_without_debug_fails_xoption(self):
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self.assertIn(b"Remote debugging is not enabled", err)
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self.assertEqual(out, b"")
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class TestSysJIT(unittest.TestCase):
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def test_jit_is_available(self):
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available = sys._jit.is_available()
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script = f"import sys; assert sys._jit.is_available() is {available}"
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assert_python_ok("-c", script, PYTHON_JIT="0")
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assert_python_ok("-c", script, PYTHON_JIT="1")
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def test_jit_is_enabled(self):
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available = sys._jit.is_available()
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script = "import sys; assert sys._jit.is_enabled() is {enabled}"
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assert_python_ok("-c", script.format(enabled=False), PYTHON_JIT="0")
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assert_python_ok("-c", script.format(enabled=available), PYTHON_JIT="1")
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def test_jit_is_active(self):
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available = sys._jit.is_available()
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script = textwrap.dedent(
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"""
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import _testcapi
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import _testinternalcapi
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import sys
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def frame_0_interpreter() -> None:
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assert sys._jit.is_active() is False
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def frame_1_interpreter() -> None:
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assert sys._jit.is_active() is False
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frame_0_interpreter()
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assert sys._jit.is_active() is False
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def frame_2_jit(expected: bool) -> None:
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# Inlined into the last loop of frame_3_jit:
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assert sys._jit.is_active() is expected
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# Insert C frame:
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_testcapi.pyobject_vectorcall(frame_1_interpreter, None, None)
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assert sys._jit.is_active() is expected
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def frame_3_jit() -> None:
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# JITs just before the last loop:
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for i in range(_testinternalcapi.TIER2_THRESHOLD + 1):
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# Careful, doing this in the reverse order breaks tracing:
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expected = {enabled} and i == _testinternalcapi.TIER2_THRESHOLD
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assert sys._jit.is_active() is expected
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frame_2_jit(expected)
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assert sys._jit.is_active() is expected
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def frame_4_interpreter() -> None:
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assert sys._jit.is_active() is False
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frame_3_jit()
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assert sys._jit.is_active() is False
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assert sys._jit.is_active() is False
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frame_4_interpreter()
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assert sys._jit.is_active() is False
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"""
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)
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assert_python_ F438 ok("-c", script.format(enabled=False), PYTHON_JIT="0")
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assert_python_ok("-c", script.format(enabled=available), PYTHON_JIT="1")
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22012259
if __name__ == "__main__":

‎Misc/NEWS.d/next/Core_and_Builtins/2025-04-30-19-07-11.gh-issue-133231.H9T8g_.rst

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@@ -0,0 +1,3 @@
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Add new utilities of observing JIT compilation:
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:func:`sys._jit.is_available`, :func:`sys._jit.is_enabled`, and
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:func:`sys._jit.is_active`.

‎Modules/_testinternalcapi.c

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@@ -1206,13 +1206,6 @@ verify_stateless_code(PyObject *self, PyObject *args, PyObject *kwargs)
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Py_RETURN_NONE;
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}
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1209-
1210-
static PyObject *
1211-
jit_enabled(PyObject *self, PyObject *arg)
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{
1213-
return PyBool_FromLong(_PyInterpreterState_GET()->jit);
1214-
}
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#ifdef _Py_TIER2
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static PyObject *
@@ -2337,7 +2330,6 @@ static PyMethodDef module_functions[] = {
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METH_VARARGS | METH_KEYWORDS, NULL},
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{"verify_stateless_code", _PyCFunction_CAST(verify_stateless_code),
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METH_VARARGS | METH_KEYWORDS, NULL},
2340-
{"jit_enabled", jit_enabled, METH_NOARGS, NULL},
23412333
#ifdef _Py_TIER2
23422334
{"add_executor_dependency", add_executor_dependency, METH_VARARGS, NULL},
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{"invalidate_executors", invalidate_executors, METH_O, NULL},

‎Python/clinic/sysmodule.c.h

Lines changed: 85 additions & 1 deletion
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