May 19, 2025 · Apr 26, 2025 · Apr 26, 2025 · Apr 29, 2025 · May 8, 2025 · May 8, 2025
diff --git a/Lib/test/test_capi/test_opt.py b/Lib/test/test_capi/test_opt.py
        self.assertNotIn("_GUARD_THIRD_NULL", uops)
        self.assertNotIn("_GUARD_CALLABLE_ISINSTANCE", uops)

    def test_call_isinstance_is_true(self):
        def testfunc(n):
            x = 0
            for _ in range(n):
                y = isinstance(42, int)
                if y:
                    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("_CALL_ISINSTANCE", uops)
        self.assertNotIn("_TO_BOOL_BOOL", uops)
        self.assertNotIn("_GUARD_IS_TRUE_POP", uops)

    def test_call_isinstance_is_false(self):
        def testfunc(n):
            x = 0
            for _ in range(n):
                y = isinstance(42, str)
                if not y:
                    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("_CALL_ISINSTANCE", uops)
        self.assertNotIn("_TO_BOOL_BOOL", uops)
        self.assertNotIn("_GUARD_IS_FALSE_POP", uops)

    def test_call_isinstance_subclass(self):
        def testfunc(n):
            x = 0
            for _ in range(n):
                y = isinstance(True, int)
                if y:
                    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("_CALL_ISINSTANCE", uops)
        self.assertNotIn("_TO_BOOL_BOOL", uops)
        self.assertNotIn("_GUARD_IS_TRUE_POP", uops)

    def test_call_isinstance_unknown_object(self):
        def testfunc(n):
            x = 0
            for _ in range(n):
                # The optimizer doesn't know the return type here:
                bar = eval("42")
                # This will only narrow to bool:
                y = isinstance(bar, int)
                if y:
                    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("_CALL_ISINSTANCE", uops)
        self.assertNotIn("_TO_BOOL_BOOL", uops)
        self.assertIn("_GUARD_IS_TRUE_POP", uops)

    def test_call_isinstance_tuple_of_classes(self):
        def testfunc(n):
            x = 0
            for _ in range(n):
                # A tuple of classes is currently not optimized,
                # so this is only narrowed to bool:
                y = isinstance(42, (int, str))
                if y:
                    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("_CALL_ISINSTANCE", uops)
        self.assertNotIn("_TO_BOOL_BOOL", uops)
        self.assertIn("_GUARD_IS_TRUE_POP", uops)

    def test_call_isinstance_metaclass(self):
        class EvenNumberMeta(type):
            def __instancecheck__(self, number):
                return number % 2 == 0

        class EvenNumber(metaclass=EvenNumberMeta):
            pass

        def testfunc(n):
            x = 0
            for _ in range(n):
                # Only narrowed to bool
                y = isinstance(42, EvenNumber)
                if y:
                    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("_CALL_ISINSTANCE", uops)
        self.assertNotIn("_TO_BOOL_BOOL", uops)
        self.assertIn("_GUARD_IS_TRUE_POP", uops)


 def global_identity(x):
    return x
diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-04-26-17-50-01.gh-issue-131798.XiOgw5.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-04-26-17-50-01.gh-issue-131798.XiOgw5.rst
 Narrow the return type and constant-evaluate ``CALL_ISINSTANCE`` for a
 subset of known values in the JIT. Patch by Tomas Roun
diff --git a/Python/optimizer_bytecodes.c b/Python/optimizer_bytecodes.c
        }
    }

    op(_CALL_ISINSTANCE, (unused, unused, instance, cls -- res)) {
        // the result is always a bool, but sometimes we can
        // narrow it down to True or False
        res = sym_new_type(ctx, &PyBool_Type);
        PyTypeObject *inst_type = sym_get_type(instance);
        PyTypeObject *cls_o = (PyTypeObject *)sym_get_const(ctx, cls);
        if (inst_type && cls_o && sym_matches_type(cls, &PyType_Type)) {
            // isinstance(inst, cls) where both inst and cls have
            // known types, meaning we can deduce either True or False

            // The below check is equivalent to PyObject_TypeCheck(inst, cls)
            if (inst_type == cls_o || PyType_IsSubtype(inst_type, cls_o)) {
                sym_set_const(res, Py_True);
            }
            else {
                sym_set_const(res, Py_False);
            }
        }
    }

    op(_GUARD_IS_TRUE_POP, (flag -- )) {
        if (sym_is_const(ctx, flag)) {
            PyObject *value = sym_get_const(ctx, flag);
diff --git a/Python/optimizer_cases.c.h b/Python/optimizer_cases.c.h
Original file line number	Diff line number	Diff line change
Expand Up		@@ -1959,6 +1959,121 @@ def testfunc(n):
		self.assertNotIn("_GUARD_THIRD_NULL", uops)
		self.assertNotIn("_GUARD_CALLABLE_ISINSTANCE", uops)

		def test_call_isinstance_is_true(self):
		def testfunc(n):
		x = 0
		for _ in range(n):
		y = isinstance(42, int)
		if y:
		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("_CALL_ISINSTANCE", uops)
		self.assertNotIn("_TO_BOOL_BOOL", uops)
		self.assertNotIn("_GUARD_IS_TRUE_POP", uops)

		def test_call_isinstance_is_false(self):
		def testfunc(n):
		x = 0
		for _ in range(n):
		y = isinstance(42, str)
		if not y:
		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("_CALL_ISINSTANCE", uops)
		self.assertNotIn("_TO_BOOL_BOOL", uops)
		self.assertNotIn("_GUARD_IS_FALSE_POP", uops)

		def test_call_isinstance_subclass(self):
		def testfunc(n):
		x = 0
		for _ in range(n):
		y = isinstance(True, int)
		if y:
		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("_CALL_ISINSTANCE", uops)
		self.assertNotIn("_TO_BOOL_BOOL", uops)
		self.assertNotIn("_GUARD_IS_TRUE_POP", uops)

		def test_call_isinstance_unknown_object(self):
		def testfunc(n):
		x = 0
		for _ in range(n):
		# The optimizer doesn't know the return type here:
		bar = eval("42")
		# This will only narrow to bool:
		y = isinstance(bar, int)
		if y:
		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("_CALL_ISINSTANCE", uops)
		self.assertNotIn("_TO_BOOL_BOOL", uops)
		self.assertIn("_GUARD_IS_TRUE_POP", uops)

		def test_call_isinstance_tuple_of_classes(self):
		def testfunc(n):
		x = 0
		for _ in range(n):
		# A tuple of classes is currently not optimized,
		# so this is only narrowed to bool:
		y = isinstance(42, (int, str))
		if y:
		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("_CALL_ISINSTANCE", uops)
		self.assertNotIn("_TO_BOOL_BOOL", uops)
		self.assertIn("_GUARD_IS_TRUE_POP", uops)

		def test_call_isinstance_metaclass(self):
		class EvenNumberMeta(type):
		def __instancecheck__(self, number):
		return number % 2 == 0

		class EvenNumber(metaclass=EvenNumberMeta):
		pass

		def testfunc(n):
		x = 0
		for _ in range(n):
		# Only narrowed to bool
		y = isinstance(42, EvenNumber)
		if y:
		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("_CALL_ISINSTANCE", uops)
		self.assertNotIn("_TO_BOOL_BOOL", uops)
		self.assertIn("_GUARD_IS_TRUE_POP", uops)


		def global_identity(x):
		return x
Expand Down
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		Narrow the return type and constant-evaluate ``CALL_ISINSTANCE`` for a
		subset of known values in the JIT. Patch by Tomas Roun
Original file line number	Diff line number	Diff line change
Expand Up		@@ -890,6 +890,26 @@ dummy_func(void) {
		}
		}

		op(_CALL_ISINSTANCE, (unused, unused, instance, cls -- res)) {
		// the result is always a bool, but sometimes we can
		// narrow it down to True or False
		res = sym_new_type(ctx, &PyBool_Type);
		PyTypeObject *inst_type = sym_get_type(instance);
		PyTypeObject cls_o = (PyTypeObject )sym_get_const(ctx, cls);
		if (inst_type && cls_o && sym_matches_type(cls, &PyType_Type)) {
		// isinstance(inst, cls) where both inst and cls have
		// known types, meaning we can deduce either True or False

		// The below check is equivalent to PyObject_TypeCheck(inst, cls)
		if (inst_type == cls_o \|\| PyType_IsSubtype(inst_type, cls_o)) {
		sym_set_const(res, Py_True);
		}
		else {
		sym_set_const(res, Py_False);
		}
		}
		}

		op(_GUARD_IS_TRUE_POP, (flag -- )) {
		if (sym_is_const(ctx, flag)) {
		PyObject *value = sym_get_const(ctx, flag);
Expand Down