gh-126204: Add a sys._jit_enabled helper

Doc/using/configure.rst

@@ -297,6 +297,25 @@ General Options
 
    .. versionadded:: 3.13
 
+.. option:: --enable-experimental-jit
+
+   Enables :ref:`JIT compiler <whatsnew313-jit-compiler>`.
+
+   Possible values:
+      * ``no`` - build interpreter without JIT.
+      * ``yes`` - build interpreter with JIT.
+      * ``yes-off`` - build interpreter with JIT but disable it by default.
+      * ``interpreter`` - build interpreter without JIT, but with enabled tier 2 interpreter.
+
+   Defines the ``Py_JIT_ENABLED`` macro, with possible values:
+      * ``0`` - interpreter was built without JIT.
+      * ``1`` - interpreter was built with JIT.
+      * ``2`` - interpreter was built without JIT, but with enabled tier 2 interpreter.
+
+      .. versionadded:: next
+
+   .. versionadded:: 3.13
+
 .. option:: PKG_CONFIG
 
    Path to ``pkg-config`` utility.

Misc/NEWS.d/next/Core_and_Builtins/2024-10-31-17-44-32.gh-issue-126204.ASJLDK.rst

@@ -0,0 +1,2 @@
+Add a ``Py_JIT_ENABLED`` variable to ``pyconfig.h`` to help determine if CPython was built
+with JIT or not.

Modules/_sysconfig.c

@@ -66,7 +66,20 @@ _sysconfig_config_vars_impl(PyObject *module)
         Py_DECREF(config);
         return NULL;
     }
-
+#ifdef Py_JIT_ENABLED
+    PyObject *py_jit_enabled;
+    if (Py_JIT_ENABLED == 1) {
+        py_jit_enabled = _PyLong_GetOne();
+    } else {
+        py_jit_enabled = PyLong_FromLong(2);
+    }
+#else
+    PyObject *py_jit_enabled = _PyLong_GetZero();
+#endif
+    if (PyDict_SetItemString(config, "Py_JIT_ENABLED", py_jit_enabled) < 0) {
+        Py_DECREF(config);
+        return NULL;
+    }
     return config;
 }
 

PC/pyconfig.h.in

@@ -102,6 +102,12 @@ WIN32 is still required for the locale module.
 /* #define Py_GIL_DISABLED 1 */
 #endif
 
+/* Define to 1 if you want to build an interpreter with JIT, or define to 2 if
+   you want to enable tier 2 interpreter */
+#ifndef Py_JIT_ENABLED
+/* #define Py_JIT_ENABLED 1 */
+#endif
+
 /* Compiler specific defines */
 
 /* ------------------------------------------------------------------------*/

PCbuild/_freeze_module.vcxproj

@@ -449,6 +449,12 @@
     <PropertyGroup Condition="$(DisableGil) == 'true'">
       <PyConfigHText>$(PyConfigHText.Replace('#undef Py_GIL_DISABLED', '#define Py_GIL_DISABLED 1'))</PyConfigHText>
     </PropertyGroup>
+    <PropertyGroup Condition="$(UseJIT) == 'true'">
+      <PyConfigHText>$(PyConfigHText.Replace('/* #define Py_JIT_ENABLED 1 */', '#define Py_JIT_ENABLED 1'))</PyConfigHText>
+    </PropertyGroup>
+    <PropertyGroup Condition="$(UseTIER2) == '4' Or $(UseTIER2) == '6'">
+      <PyConfigHText>$(PyConfigHText.Replace('/* #define Py_JIT_ENABLED 1 */', '#define Py_JIT_ENABLED 2'))</PyConfigHText>
+    </PropertyGroup>
     <Message Text="Updating pyconfig.h" Condition="$(PyConfigHText.TrimEnd()) != $(OldPyConfigH.TrimEnd())" />
     <WriteLinesToFile File="$(IntDir)pyconfig.h"
                       Lines="$(PyConfigHText)"

PCbuild/pythoncore.vcxproj

@@ -705,6 +705,12 @@
     <PropertyGroup Condition="$(DisableGil) == 'true'">
       <PyConfigHText>$(PyConfigHText.Replace('/* #define Py_GIL_DISABLED 1 */', '#define Py_GIL_DISABLED 1'))</PyConfigHText>
     </PropertyGroup>
+    <PropertyGroup Condition="$(UseJIT) == 'true'">
+      <PyConfigHText>$(PyConfigHText.Replace('/* #define Py_JIT_ENABLED 1 */', '#define Py_JIT_ENABLED 1'))</PyConfigHText>
+    </PropertyGroup>
+    <PropertyGroup Condition="$(UseTIER2) == '4' Or $(UseTIER2) == '6'">
+      <PyConfigHText>$(PyConfigHText.Replace('/* #define Py_JIT_ENABLED 1 */', '#define Py_JIT_ENABLED 2'))</PyConfigHText>
+    </PropertyGroup>
     <Message Text="Updating pyconfig.h" Condition="$(PyConfigHText.TrimEnd()) != $(OldPyConfigH.TrimEnd())" />
     <WriteLinesToFile File="$(IntDir)pyconfig.h"
                       Lines="$(PyConfigHText)"

configure.ac

@@ -1820,11 +1820,30 @@ AC_ARG_ENABLE([experimental-jit],
               [],
               [enable_experimental_jit=no])
 case $enable_experimental_jit in
-  no)              jit_flags="";          tier2_flags="" ;;
-  yes)             jit_flags="-D_Py_JIT"; tier2_flags="-D_Py_TIER2=1" ;;
-  yes-off)         jit_flags="-D_Py_JIT"; tier2_flags="-D_Py_TIER2=3" ;;
-  interpreter)     jit_flags="";          tier2_flags="-D_Py_TIER2=4" ;;
-  interpreter-off) jit_flags="";          tier2_flags="-D_Py_TIER2=6" ;;  # Secret option
+  no)
+    jit_flags="";
+    tier2_flags="";
+    ;;
+  yes)
+    jit_flags="-D_Py_JIT";
+    tier2_flags="-D_Py_TIER2=1";
+    AC_DEFINE([Py_JIT_ENABLED], [1], [Define to 1 if you want to build an interpreter with JIT, or define to 2 if you want to enable tier 2 interpreter])
+    ;;
+  yes-off)
+    jit_flags="-D_Py_JIT";
+    tier2_flags="-D_Py_TIER2=3";
+    AC_DEFINE([Py_JIT_ENABLED], [1], [Define to 1 if you want to build an interpreter with JIT, or define to 2 if you want to enable tier 2 interpreter])
+    ;;
+  interpreter)
+    jit_flags="";
+    tier2_flags="-D_Py_TIER2=4";
+    AC_DEFINE([Py_JIT_ENABLED], [2], [Define to 1 if you want to build an interpreter with JIT, or define to 2 if you want to enable tier 2 interpreter])
+    ;;
+  interpreter-off)
+    jit_flags="";
+    tier2_flags="-D_Py_TIER2=6";
+    AC_DEFINE([Py_JIT_ENABLED], [2], [Define to 1 if you want to build an interpreter with JIT, or define to 2 if you want to enable tier 2 interpreter])  # Secret option
+    ;;
   *) AC_MSG_ERROR(
       [invalid argument: --enable-experimental-jit=$enable_experimental_jit; expected no|yes|yes-off|interpreter]) ;;
 esac

pyconfig.h.in

@@ -1695,6 +1695,10 @@
 /* Defined if _Complex C type is available. */
 #undef Py_HAVE_C_COMPLEX
 
+/* Define to 1 if you want to build an interpreter with JIT, or define to 2 if
+   you want to enable tier 2 interpreter */
+#undef Py_JIT_ENABLED
+
 /* Define if year with century should be normalized for strftime. */
 #undef Py_NORMALIZE_CENTURY