gh-115419: Change default sym to not_null (GH-116562)

Author: Fidget-Spinner

Lib/test/test_generated_cases.py

@@ -908,7 +908,7 @@ def test_overridden_abstract_args(self):
 
         case OP2: {
             _Py_UopsSymbol *out;
-            out = sym_new_unknown(ctx);
+            out = sym_new_not_null(ctx);
             if (out == NULL) goto out_of_space;
             stack_pointer[-1] = out;
             break;
@@ -933,7 +933,7 @@ def test_no_overridden_case(self):
         output = """
         case OP: {
             _Py_UopsSymbol *out;
-            out = sym_new_unknown(ctx);
+            out = sym_new_not_null(ctx);
             if (out == NULL) goto out_of_space;
             stack_pointer[-1] = out;
             break;

Python/optimizer_bytecodes.c

@@ -449,6 +449,14 @@ dummy_func(void) {
         }
     }
 
+    op(_LOAD_ATTR, (owner -- attr, self_or_null if (oparg & 1))) {
+        (void)owner;
+        OUT_OF_SPACE_IF_NULL(attr = sym_new_not_null(ctx));
+        if (oparg & 1) {
+            OUT_OF_SPACE_IF_NULL(self_or_null = sym_new_unknown(ctx));
+        }
+    }
+
     op(_LOAD_ATTR_MODULE, (index/1, owner -- attr, null if (oparg & 1))) {
         (void)index;
         OUT_OF_SPACE_IF_NULL(null = sym_new_null(ctx));
@@ -513,7 +521,6 @@ dummy_func(void) {
         OUT_OF_SPACE_IF_NULL(self = sym_new_not_null(ctx));
     }
 
-
     op(_CHECK_FUNCTION_EXACT_ARGS, (func_version/2, callable, self_or_null, unused[oparg] -- callable, self_or_null, unused[oparg])) {
         if (!sym_set_type(callable, &PyFunction_Type)) {
             goto hit_bottom;