gh-131798: Use sym_new_type instead of sym_new_not_null for _BUILD_LIST, _BUILD_SLICE, and _BUILD_MAP (GH-132434)

---------

Signed-off-by: Manjusaka <[email protected]>

Author: Zheaoli

Lib/test/test_capi/test_opt.py

@@ -1678,15 +1678,15 @@ def f(n):
             x = 0
             for _ in range(n):
                 d = {}
-                d["Spam"] = 1  # Guarded...
+                d["Spam"] = 1  # unguarded!
                 x += d["Spam"]  # ...unguarded!
             return x
 
         res, ex = self._run_with_optimizer(f, TIER2_THRESHOLD)
         self.assertEqual(res, TIER2_THRESHOLD)
         self.assertIsNotNone(ex)
         uops = get_opnames(ex)
-        self.assertEqual(uops.count("_GUARD_NOS_DICT"), 1)
+        self.assertEqual(uops.count("_GUARD_NOS_DICT"), 0)
         self.assertEqual(uops.count("_STORE_SUBSCR_DICT"), 1)
         self.assertEqual(uops.count("_BINARY_OP_SUBSCR_DICT"), 1)
 
@@ -1695,7 +1695,7 @@ def f(n):
             x = 0
             for _ in range(n):
                 l = [0]
-                l[0] = 1  # Guarded...
+                l[0] = 1  # unguarded!
                 [a] = l  # ...unguarded!
                 b = l[0]  # ...unguarded!
                 if l:  # ...unguarded!
@@ -1706,7 +1706,7 @@ def f(n):
         self.assertEqual(res, 2 * TIER2_THRESHOLD)
         self.assertIsNotNone(ex)
         uops = get_opnames(ex)
-        self.assertEqual(uops.count("_GUARD_NOS_LIST"), 1)
+        self.assertEqual(uops.count("_GUARD_NOS_LIST"), 0)
         self.assertEqual(uops.count("_STORE_SUBSCR_LIST_INT"), 1)
         self.assertEqual(uops.count("_GUARD_TOS_LIST"), 0)
         self.assertEqual(uops.count("_UNPACK_SEQUENCE_LIST"), 1)

Misc/NEWS.d/next/Core_and_Builtins/2025-04-12-19-41-16.gh-issue-131798.JkSocg.rst

@@ -0,0 +1,2 @@
+Use ``sym_new_type`` instead of ``sym_new_not_null`` for _BUILD_LIST,
+_BUILD_SET, _BUILD_MAP

Python/optimizer_bytecodes.c

@@ -919,6 +919,18 @@ dummy_func(void) {
         tup = sym_new_tuple(ctx, oparg, values);
     }
 
+    op(_BUILD_LIST, (values[oparg] -- list)) {
+        list = sym_new_type(ctx, &PyList_Type);
+    }
+
+    op(_BUILD_SLICE, (values[oparg] -- slice)) {
+        slice = sym_new_type(ctx, &PySlice_Type);
+    }
+
+    op(_BUILD_MAP, (values[oparg*2] -- map)) {
+        map = sym_new_type(ctx, &PyDict_Type);
+    }
+
     op(_UNPACK_SEQUENCE_TWO_TUPLE, (seq -- val1, val0)) {
         val0 = sym_tuple_getitem(ctx, seq, 0);
         val1 = sym_tuple_getitem(ctx, seq, 1);