Make _BINARY_OP_SUBSCR_TUPLE_INT smarter

Author: tomasr8

Lib/test/test_capi/test_opt.py

@@ -1923,6 +1923,23 @@ def testfunc(n):
         self.assertNotIn("_GUARD_TOS_INT", uops)
         self.assertIn("_CALL_LEN", uops)
 
+    def test_binary_op_subscr_tuple_int(self):
+        def testfunc(n):
+            x = 0
+            for _ in range(n):
+                y = (1, 2)
+                if y[0] == 1:  # _COMPARE_OP_INT + _GUARD_IS_TRUE_POP are removed
+                    x += 1
+            return x
+
+        res, ex = self._run_with_optimizer(testfunc, TIER2_THRESHOLD)
+        self.assertEqual(res, TIER2_THRESHOLD)
+        self.assertIsNotNone(ex)
+        uops = get_opnames(ex)
+        self.assertIn("_BINARY_OP_SUBSCR_TUPLE_INT", uops)
+        self.assertNotIn("_COMPARE_OP_INT", uops)
+        self.assertNotIn("_GUARD_IS_TRUE_POP", uops)
+
 
 def global_identity(x):
     return x

Python/optimizer_bytecodes.c

@@ -370,6 +370,20 @@ dummy_func(void) {
         res = sym_new_type(ctx, &PyUnicode_Type);
     }
 
+    op(_BINARY_OP_SUBSCR_TUPLE_INT, (left, right -- res)) {
+        assert(sym_matches_type(left, &PyTuple_Type));
+        if (sym_is_const(ctx, right)) {
+            assert(PyLong_CheckExact(sym_get_const(ctx, right)));
+            long index = PyLong_AsLong(sym_get_const(ctx, right));
+            assert(index >= 0);
+            assert(index < sym_tuple_length(left));
+            res = sym_tuple_getitem(ctx, left, index);
+        }
+        else {
+            res = sym_new_not_null(ctx);
+        }
+    }
+
     op(_TO_BOOL, (value -- res)) {
         int already_bool = optimize_to_bool(this_instr, ctx, value, &res);
         if (!already_bool) {