gh-141858: Speed up Objects/tupleobject.c richcompare with early identity and length checks

Lib/test/seq_tests.py

@@ -250,6 +250,35 @@ def __eq__(self, other):
         checklast = self.type2test([StopCompares(), 1])
         self.assertRaises(DoNotTestEq, checklast.__contains__, 1)
 
+    def check_compare_id(self, a, b):
+        self.assertTrue(a == a)
+        self.assertFalse(a != a)
+        self.assertTrue(a == b)
+        self.assertFalse(a != b)
+        self.assertFalse(a < a)
+        self.assertFalse(a < b)
+        self.assertFalse(a > b)
+
+    def test_compare_nan(self):
+        nan = float("nan")
+        a = self.type2test([nan])
+        b = self.type2test([nan])
+        self.check_compare_id(a, b)
+
+    def test_compare_decimal_nan(self):
+        import decimal
+        nan = decimal.Decimal("NaN")
+        a = self.type2test([nan])
+        b = self.type2test([nan])
+        self.check_compare_id(a, b)
+
+    def test_compare_signed_zero(self):
+        a = self.type2test([0.0])
+        b = self.type2test([-0.0])
+        self.check_compare_id(a, b)
+        self.assertTrue(b == b)
+        self.assertFalse(b != b)
+
     def test_len(self):
         self.assertEqual(len(self.type2test()), 0)
         self.assertEqual(len(self.type2test([])), 0)

Objects/tupleobject.c

@@ -666,18 +666,24 @@ tuple_richcompare(PyObject *v, PyObject *w, int op)
     if (!PyTuple_Check(v) || !PyTuple_Check(w))
         Py_RETURN_NOTIMPLEMENTED;
 
+    if (v == w) {
+        Py_RETURN_RICHCOMPARE(0, 0, op);
+    }
+
     vt = (PyTupleObject *)v;
     wt = (PyTupleObject *)w;
 
     vlen = Py_SIZE(vt);
     wlen = Py_SIZE(wt);
 
-    /* Note:  the corresponding code for lists has an "early out" test
-     * here when op is EQ or NE and the lengths differ.  That pays there,
-     * but Tim was unable to find any real code where EQ/NE tuple
-     * compares don't have the same length, so testing for it here would
-     * have cost without benefit.
-     */
+    if (vlen != wlen) {
+        switch (op) {
+        case Py_EQ:
+            Py_RETURN_FALSE;
+        case Py_NE:
+            Py_RETURN_TRUE;
+        }
+    }
 
     /* Search for the first index where items are different.
      * Note that because tuples are immutable, it's safe to reuse