From 4802173eba5108f1f4c950600322cd3f6b82850f Mon Sep 17 00:00:00 2001
From: ahgamut <41098605+ahgamut@users.noreply.github.com>
Date: Tue, 9 Nov 2021 00:49:52 +0530
Subject: [PATCH] speed up unpickling

refer python/cpython@bee09aecc2c31
---
 third_party/python/Lib/pickle.py     | 14 ++++---
 third_party/python/Modules/_pickle.c | 58 +++++++++++++++++++---------
 2 files changed, 49 insertions(+), 23 deletions(-)

diff --git a/third_party/python/Lib/pickle.py b/third_party/python/Lib/pickle.py
index 54411616d..c89a28e85 100644
--- a/third_party/python/Lib/pickle.py
+++ b/third_party/python/Lib/pickle.py
@@ -1465,12 +1465,16 @@ class _Unpickler:
     def load_appends(self):
         items = self.pop_mark()
         list_obj = self.stack[-1]
-        if isinstance(list_obj, list):
-            list_obj.extend(items)
+        try:
+            extend = list_obj.extend
+        except AttributeError:
+            pass
         else:
-            append = list_obj.append
-            for item in items:
-                append(item)
+            extend(items)
+            return
+        append = list_obj.append
+        for item in items:
+            append(item)
     dispatch[APPENDS[0]] = load_appends
 
     def load_setitem(self):
diff --git a/third_party/python/Modules/_pickle.c b/third_party/python/Modules/_pickle.c
index aa815047e..e0b2f32a8 100644
--- a/third_party/python/Modules/_pickle.c
+++ b/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 +5972,48 @@ 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(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;