Backporting METH_FASTCALL from Python 3.7 (#317)

* dict copy speedup

refer to bpo-31179 or python/cpython@boa7a037b8fde

* __build_class__() uses METH_FASTCALL

refer python/cpython@69de71b255
refer python/cpython@773dc6dd06

a single test related to __prepare__ fails.

* type_prepare uses METH_FASTCALL

refer python/cpython@d526cfe546
refer python/cpython@80ab22fa2c

the prepare-related test still fails.  It's just related to the error
message format though.

* separate into ParseStack and ParseStackAndKeywords

refer python/cpython@6518a93cb1
refer python/cpython@3e1fad6913
refer python/cpython@c0083fc47d

* Add _PyArg_NoStackKeywords

refer python/cpython@29d39cc8f5

* _PyStack_UnpackDict now returns int

refer python/cpython@998c20962c

* METH_FASTCALL changes to .inc files

done via python's Argument Clinic tool,
refer python/cpython@259f0e4437

* Added _PyArg_UnpackStack

refer python/cpython@fe54dda08

* Argument Clinic FASTCALL again

refer python/cpython@0c4a828ca

* Argument Clinic for ordered dictionary object

refer python/cpython@b05cbac052

* speed up getargs

refer python/cpython@1741441649

* FASTCALL for sorted, next, and getattr

refer python/cpython@5a60ecaa7a
refer python/cpython@fda6d0acf0
refer python/cpython@84b388bb80

* Optimize methoddescr_call

refer python/cpython@2a1b676d1f
refer python/cpython@c52572319c
refer python/cpython@35ecebe165
refer python/cpython@8128d5a491

* cleanup _PyMethodDef_RawFastCallDict

refer python/cpython@0a2e46835d
refer python/cpython@98ccba8344
refer python/cpython@c89ef828cf
refer python/cpython@250e4b0063

* print now uses METH_FASTCALL

refer python/cpython@c3858bd7c6
refer python/cpython@bd584f169f
refer python/cpython@06d34393c2

* _struct module now uses Argument Clinic

refer python/cpython@3f2d10132d

* make deque methods faster

refer python/cpython@dd407d5006

* recursive calls in PyObject_Call

refer python/cpython@7399a05965

only partially ported, because RawFastCallKeywords hasn't been ported

* add macros

refer python/cpython@68a001dd59

* all tests pass in MODE=dbg

* convert some internal functions to FASTCALL

__import__ might need to be changed later, if it is possible to backport
the METH_FASTCALL | METH_KEYWORDS flag distinction later.

* speed up unpickling

refer python/cpython@bee09aecc2

* added _PyMethodDef_RawFastCallKeywords

refer python/cpython@7399a05965

* PyCFunction_Call performance

refer python/cpython@12c5838dae

* avoid PyMethodObject in slots

main change in python/cpython@516b98161a
test_exceptions changed in python/cpython@331bbe6aaa
type_settattro changed in python/cpython@193f7e094f
_PyObject_CallFunctionVa changed in python/cpython@fe4ff83049

* fix refcount error found in MODE=dbg

all tests now pass in MODE=dbg

third_party/python/Modules/_pickle.c

@@ -5946,6 +5946,8 @@ static int
 do_append(UnpicklerObject *self, Py_ssize_t x)
 {
     PyObject *value;
+    PyObject *slice;
+    PyObject *result;
     PyObject *list;
     Py_ssize_t len, i;
 
@@ -5957,8 +5959,7 @@ do_append(UnpicklerObject *self, Py_ssize_t x)
 
     list = self->stack->data[x - 1];
 
-    if (PyList_Check(list)) {
-        PyObject *slice;
+    if (PyList_CheckExact(list)) {
         Py_ssize_t list_len;
         int ret;
 
@@ -5971,27 +5972,47 @@ do_append(UnpicklerObject *self, Py_ssize_t x)
         return ret;
     }
     else {
-        PyObject *append_func;
-        _Py_IDENTIFIER(append);
+        PyObject *extend_func;
+        _Py_IDENTIFIER(extend);
 
-        append_func = _PyObject_GetAttrId(list, &PyId_append);
-        if (append_func == NULL)
-            return -1;
-        for (i = x; i < len; i++) {
-            PyObject *result;
-
-            value = self->stack->data[i];
-            result = _Pickle_FastCall(append_func, value);
-            if (result == NULL) {
-                Pdata_clear(self->stack, i + 1);
-                Py_SIZE(self->stack) = x;
-                Py_DECREF(append_func);
+        extend_func = _PyObject_GetAttrId(list, &PyId_extend);
+        if (extend_func != NULL) {
+            slice = Pdata_poplist(self->stack, x);
+            if (!slice) {
+                Py_DECREF(extend_func);
                 return -1;
             }
+            result = _Pickle_FastCall(extend_func, slice);
+            Py_DECREF(extend_func);
+            if (result == NULL)
+                return -1;
             Py_DECREF(result);
         }
-        Py_SIZE(self->stack) = x;
-        Py_DECREF(append_func);
+        else {
+            PyObject *append_func;
+            _Py_IDENTIFIER(append);
+
+            /* Even if the PEP 307 requires extend() and append() methods,
+               fall back on append() if the object has no extend() method
+               for backward compatibility. */
+            PyErr_Clear();
+            append_func = _PyObject_GetAttrId(list, &PyId_append);
+            if (append_func == NULL)
+                return -1;
+            for (i = x; i < len; i++) {
+                value = self->stack->data[i];
+                result = _Pickle_FastCall(append_func, value);
+                if (result == NULL) {
+                    Pdata_clear(self->stack, i + 1);
+                    Py_SIZE(self->stack) = x;
+                    Py_DECREF(append_func);
+                    return -1;
+                }
+                Py_DECREF(result);
+            }
+            Py_SIZE(self->stack) = x;
+            Py_DECREF(append_func);
+        }
     }
 
     return 0;