bpo-36127: Argument Clinic: inline parsing code for keyword parameters. (GH-12058)

Author: serhiy-storchaka

Doc/whatsnew/3.8.rst

@@ -442,6 +442,11 @@ Optimizations
   (Contributed by Stefan Behnel, Pablo Galindo Salgado, Raymond Hettinger,
   Neil Schemenauer, and Serhiy Storchaka in :issue:`36012`.)
 
+* Reduced an overhead of converting arguments passed to many builtin functions
+  and methods.  This sped up calling some simple builtin functions and
+  methods up to 20--50%.  (Contributed by Serhiy Storchaka in :issue:`23867`,
+  :issue:`35582` and :issue:`36127`.)
+
 
 Build and C API Changes
 =======================

Include/modsupport.h

@@ -118,6 +118,18 @@ PyAPI_FUNC(int) _PyArg_ParseStackAndKeywords(
     ...);
 PyAPI_FUNC(int) _PyArg_VaParseTupleAndKeywordsFast(PyObject *, PyObject *,
                                                    struct _PyArg_Parser *, va_list);
+PyAPI_FUNC(PyObject * const *) _PyArg_UnpackKeywords(
+        PyObject *const *args, Py_ssize_t nargs,
+        PyObject *kwargs, PyObject *kwnames,
+        struct _PyArg_Parser *parser,
+        int minpos, int maxpos, int minkw,
+        PyObject **buf);
+#define _PyArg_UnpackKeywords(args, nargs, kwargs, kwnames, parser, minpos, maxpos, minkw, buf) \
+    (((minkw) == 0 && (kwargs) == NULL && (kwnames) == NULL && \
+      (minpos) <= (nargs) && (nargs) <= (maxpos) && args != NULL) ? (args) : \
+     _PyArg_UnpackKeywords((args), (nargs), (kwargs), (kwnames), (parser), \
+                           (minpos), (maxpos), (minkw), (buf)))
+
 void _PyArg_Fini(void);
 #endif   /* Py_LIMITED_API */