Feb 4, 2026 · Feb 4, 2026 · Feb 4, 2026 · Feb 4, 2026 · Feb 4, 2026 · Feb 4, 2026
diff --git a/Lib/test/test_capi/test_opt.py b/Lib/test/test_capi/test_opt.py
        self.assertNotIn("_GUARD_NOS_TUPLE", uops)
        self.assertIn("_BINARY_OP_SUBSCR_TUPLE_INT", uops)

    def test_remove_guard_for_known_type_slice(self):
        def f(n):
            x = 0
            for _ in range(n):
                l = [1, 2, 3]
                slice_obj = slice(0, 1)
                x += l[slice_obj][0] # guarded
                x += l[slice_obj][0] # unguarded
            return x
        res, ex = self._run_with_optimizer(f, TIER2_THRESHOLD)
        self.assertEqual(res, TIER2_THRESHOLD * 2)
        uops = get_opnames(ex)

        count = count_ops(ex, "_GUARD_TOS_SLICE")
        self.assertEqual(count, 1)
        self.assertIn("_BINARY_OP_SUBSCR_LIST_INT", uops)

    def test_remove_guard_for_tuple_bounds_check(self):
        def f(n):
            x = 0
diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-02-04-12-19-48.gh-issue-131798.My5jLy.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-02-04-12-19-48.gh-issue-131798.My5jLy.rst
 Optimise ``_GUARD_TOS_SLICE`` in the JIT.
diff --git a/Python/optimizer_bytecodes.c b/Python/optimizer_bytecodes.c
        }
    }

 op(_GUARD_TOS_SLICE, (tos--tos)){
 if (sym_matches_type(tos,&PySlice_Type)){
 ADD_OP(_NOP,0,0);
        }
 sym_set_type(tos,&PySlice_Type);
    }

 op(_GUARD_NOS_NULL, (null,unused--null,unused)) {
 if (sym_is_null(null)) {
 ADD_OP(_NOP,0,0);
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		@@ -2030,6 +2030,23 @@ def f(n):
		self.assertNotIn("_GUARD_NOS_TUPLE", uops)
		self.assertIn("_BINARY_OP_SUBSCR_TUPLE_INT", uops)

		def test_remove_guard_for_known_type_slice(self):
		def f(n):
		x = 0
		for _ in range(n):
		l = [1, 2, 3]
		slice_obj = slice(0, 1)
		x += l[slice_obj][0] # guarded
		x += l[slice_obj][0] # unguarded
		return x
		res, ex = self._run_with_optimizer(f, TIER2_THRESHOLD)
		self.assertEqual(res, TIER2_THRESHOLD * 2)
		uops = get_opnames(ex)

		count = count_ops(ex, "_GUARD_TOS_SLICE")
		self.assertEqual(count, 1)
		self.assertIn("_BINARY_OP_SUBSCR_LIST_INT", uops)

		def test_remove_guard_for_tuple_bounds_check(self):
		def f(n):
		x = 0
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -1417,6 +1417,13 @@ dummy_func(void) {
		}
		}

		op(_GUARD_TOS_SLICE, (tos--tos)){
		if (sym_matches_type(tos,&PySlice_Type)){
		ADD_OP(_NOP,0,0);
		}
		sym_set_type(tos,&PySlice_Type);
		}

		op(_GUARD_NOS_NULL, (null,unused--null,unused)) {
		if (sym_is_null(null)) {
		ADD_OP(_NOP,0,0);
Expand Down