docs

Author: eendebakpt

Lib/test/test_capi/test_opt.py

@@ -1565,8 +1565,8 @@ def fn(a):
     def test_init_resolves_callable(self):
         """
         _CHECK_AND_ALLOCATE_OBJECT should resolve __init__ to a constant,
-        enabling the optimizer to trace into the init frame and eliminate
-        redundant function version and arg count checks.
+        enabling the optimizer to propagate type information through the frame
+        and eliminate redundant function version and arg count checks.
         """
         class MyPoint:
             def __init__(self, x, y):

Python/bytecodes.c

@@ -2721,6 +2721,11 @@ dummy_func(
         }
 
         op(_GUARD_TYPE_VERSION_LOCKED, (type_version/2, owner -- owner)) {
+            // Guard that type version matches expected value. Object is assumed to be
+            // locked on entry. If version matches, lock is retained for subsequent
+            // operations. If mismatch, unlock and exit (deopt). This allows the JIT
+            // optimizer to eliminate this guard entirely if type version is proven,
+            // in which case the lock is held for the entire trace duration.
             PyObject *owner_o = PyStackRef_AsPyObjectBorrow(owner);
             assert(type_version != 0);
             PyTypeObject *tp = Py_TYPE(owner_o);