bpo-32403: Faster date and datetime constructors (#4993)

* Add tests for date subclass alternate constructors

* Switch over alternate date constructors to fast path

* Switch datetime constructors to fastpath, fix bpo-32404

* Add fast path for datetime in date subclass constructor

* Set fold in constructor in datetime.combine

* Add news entries.

1 files changed, 75 insertions, 45 deletions

diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c
index e68c7c0..d1f48e5 100644
--- a/Modules/_datetimemodule.c
+++ b/Modules/_datetimemodule.c
@@ -847,6 +847,27 @@ new_date_ex(int year, int month, int day, PyTypeObject *type)
 #define new_date(year, month, day) \
     new_date_ex(year, month, day, &PyDateTime_DateType)
 
+// Forward declaration
+static PyObject * new_datetime_ex(int, int, int, int, int, int, int,
+                                  PyObject*, PyTypeObject*);
+
+/* Create date instance with no range checking, or call subclass constructor */
+static PyObject *
+new_date_subclass_ex(int year, int month, int day, PyObject *cls) {
+    PyObject *result;
+    // We have "fast path" constructors for two subclasses: date and datetime
+    if ((PyTypeObject *)cls == &PyDateTime_DateType) {
+        result = new_date_ex(year, month, day, (PyTypeObject *)cls);
+    } else if ((PyTypeObject *)cls == &PyDateTime_DateTimeType) {
+        result = new_datetime_ex(year, month, day, 0, 0, 0, 0, Py_None,
+                                 (PyTypeObject *)cls);
+    } else {
+        result = PyObject_CallFunction(cls, "iii", year, month, day);
+    }
+
+    return result;
+}
+
 /* Create a datetime instance with no range checking. */
 static PyObject *
 new_datetime_ex2(int year, int month, int day, int hour, int minute,
@@ -894,6 +915,40 @@ new_datetime_ex(int year, int month, int day, int hour, int minute,
     new_datetime_ex2(y, m, d, hh, mm, ss, us, tzinfo, fold, \
                     &PyDateTime_DateTimeType)
 
+static PyObject *
+new_datetime_subclass_fold_ex(int year, int month, int day, int hour, int minute,
+                              int second, int usecond, PyObject *tzinfo,
+                              int fold, PyObject *cls) {
+    PyObject* dt;
+    if ((PyTypeObject*)cls == &PyDateTime_DateTimeType) {
+        // Use the fast path constructor
+        dt = new_datetime(year, month, day, hour, minute, second, usecond,
+                          tzinfo, fold);
+    } else {
+        // Subclass
+        dt = PyObject_CallFunction(cls, "iiiiiiiO",
+                                   year,
+                                   month,
+                                   day,
+                                   hour,
+                                   minute,
+                                   second,
+                                   usecond,
+                                   tzinfo);
+    }
+
+    return dt;
+}
+
+static PyObject *
+new_datetime_subclass_ex(int year, int month, int day, int hour, int minute,
+                              int second, int usecond, PyObject *tzinfo,
+                              PyObject *cls) {
+    return new_datetime_subclass_fold_ex(year, month, day, hour, minute,
+                                         second, usecond, tzinfo, 0,
+                                         cls);
+}
+
 /* Create a time instance with no range checking. */
 static PyObject *
 new_time_ex2(int hour, int minute, int second, int usecond,
@@ -2743,10 +2798,10 @@ date_local_from_object(PyObject *cls, PyObject *obj)
     if (_PyTime_localtime(t, &tm) != 0)
         return NULL;
 
-    return PyObject_CallFunction(cls, "iii",
-                                 tm.tm_year + 1900,
-                                 tm.tm_mon + 1,
-                                 tm.tm_mday);
+    return new_date_subclass_ex(tm.tm_year + 1900,
+                                tm.tm_mon + 1,
+                                tm.tm_mday,
+                                cls);
 }
 
 /* Return new date from current time.
@@ -2809,8 +2864,7 @@ date_fromordinal(PyObject *cls, PyObject *args)
                                               ">= 1");
         else {
             ord_to_ymd(ordinal, &year, &month, &day);
-            result = PyObject_CallFunction(cls, "iii",
-                                           year, month, day);
+            result = new_date_subclass_ex(year, month, day, cls);
         }
     }
     return result;
@@ -2845,14 +2899,7 @@ date_fromisoformat(PyObject *cls, PyObject *dtstr) {
         return NULL;
     }
 
-    PyObject *result;
-    if ( (PyTypeObject*)cls == &PyDateTime_DateType ) {
-        result = new_date_ex(year, month, day, (PyTypeObject*)cls);
-    } else {
-        result = PyObject_CallFunction(cls, "iii", year, month, day);
-    }
-
-    return result;
+    return new_date_subclass_ex(year, month, day, cls);
 }
 
 
@@ -4596,9 +4643,8 @@ datetime_from_timet_and_us(PyObject *cls, TM_FUNC f, time_t timet, int us,
                 fold = 1;
         }
     }
-    return new_datetime_ex2(year, month, day, hour,
-                            minute, second, us, tzinfo, fold,
-                            (PyTypeObject *)cls);
+    return new_datetime_subclass_fold_ex(year, month, day, hour, minute,
+                                         second, us, tzinfo, fold, cls);
 }
 
 /* Internal helper.
@@ -4764,17 +4810,16 @@ datetime_combine(PyObject *cls, PyObject *args, PyObject *kw)
             else
                 tzinfo = Py_None;
         }
-        result = PyObject_CallFunction(cls, "iiiiiiiO",
-                                       GET_YEAR(date),
-                                       GET_MONTH(date),
-                                       GET_DAY(date),
-                                       TIME_GET_HOUR(time),
-                                       TIME_GET_MINUTE(time),
-                                       TIME_GET_SECOND(time),
-                                       TIME_GET_MICROSECOND(time),
-                                       tzinfo);
-        if (result)
-            DATE_SET_FOLD(result, TIME_GET_FOLD(time));
+        result = new_datetime_subclass_fold_ex(GET_YEAR(date),
+                                               GET_MONTH(date),
+                                               GET_DAY(date),
+                                               TIME_GET_HOUR(time),
+                                               TIME_GET_MINUTE(time),
+                                               TIME_GET_SECOND(time),
+                                               TIME_GET_MICROSECOND(time),
+                                               tzinfo,
+                                               TIME_GET_FOLD(time),
+                                               cls);
     }
     return result;
 }
@@ -4832,23 +4877,8 @@ datetime_fromisoformat(PyObject* cls, PyObject *dtstr) {
         return NULL;
     }
 
-    PyObject* dt;
-    if ( (PyTypeObject*)cls == &PyDateTime_DateTimeType ) {
-        // Use the fast path constructor
-        dt = new_datetime(year, month, day, hour, minute, second, microsecond,
-                          tzinfo, 0);
-    } else {
-        // Subclass
-        dt = PyObject_CallFunction(cls, "iiiiiiiO",
-                                       year,
-                                       month,
-                                       day,
-                                       hour,
-                                       minute,
-                                       second,
-                                       microsecond,
-                                       tzinfo);
-    }
+    PyObject *dt = new_datetime_subclass_ex(year, month, day, hour, minute,
+                                            second, microsecond, tzinfo, cls);
 
     Py_DECREF(tzinfo);
     return dt;