Drop 'immortal' bit. Only use 'counted' bit.

Author: markshannon

Include/internal/pycore_stackref.h

@@ -187,16 +187,6 @@ _PyStackRef_FromPyObjectStealMortal(PyObject *obj, const char *filename, int lin
 }
 #define PyStackRef_FromPyObjectStealMortal(obj) _PyStackRef_FromPyObjectStealMortal(_PyObject_CAST(obj), __FILE__, __LINE__)
 
-static inline bool
-PyStackRef_IsMortal(_PyStackRef ref)
-{
-    PyObject *obj = _Py_stackref_get_object(ref);
-    if (obj == NULL) {
-        return false;
-    }
-    return _Py_IsImmortal(obj);
-}
-
 static inline bool
 PyStackRef_IsHeapSafe(_PyStackRef ref)
 {
@@ -377,8 +367,12 @@ PyStackRef_AsStrongReference(_PyStackRef stackref)
 // With GIL
 
 #define Py_TAG_BITS 3
-#define Py_TAG_IMMORTAL _Py_IMMORTAL_FLAGS
 #define Py_TAG_REFCNT 1
+#if _Py_IMMORTAL_FLAGS != Py_TAG_REFCNT
+#  error "_Py_IMMORTAL_FLAGS != Py_TAG_REFCNT"
+#endif
+#define Py_TAG_IMMORTAL _Py_IMMORTAL_FLAGS
+
 #define BITS_TO_PTR(REF) ((PyObject *)((REF).bits))
 #define BITS_TO_PTR_MASKED(REF) ((PyObject *)(((REF).bits) & (~Py_TAG_BITS)))
 
@@ -402,7 +396,6 @@ static inline void PyStackRef_CheckValid(_PyStackRef ref) {
     PyObject *obj = BITS_TO_PTR_MASKED(ref);
     switch (tag) {
         case 0:
-        case Py_TAG_REFCNT:
             /* Can be immortal if object was made immortal after reference came into existence */
             assert(!_Py_IsStaticImmortal(obj));
             break;
@@ -422,8 +415,6 @@ static inline void PyStackRef_CheckValid(_PyStackRef ref) {
 
 #ifdef _WIN32
 #define PyStackRef_IsUncountedMortal(REF) (((REF).bits & Py_TAG_BITS) == 0)
-#define PyStackRef_IsCountedMortal(REF) (((REF).bits & Py_TAG_BITS) == Py_TAG_REFCNT)
-#define PyStackRef_IsMortal(REF) (((REF).bits & Py_TAG_BITS) != Py_TAG_IMMORTAL)
 #define PyStackRef_AsPyObjectBorrow BITS_TO_PTR_MASKED
 #else
 /* Does this ref not have an embedded refcount and refer to a mortal object? */
@@ -433,20 +424,6 @@ PyStackRef_IsUncountedMortal(_PyStackRef ref)
     return (ref.bits & Py_TAG_BITS) == 0;
 }
 
-/* Does this ref have an embedded refcount and refer to a mortal object (NULL is not mortal)? */
-static inline bool
-PyStackRef_IsCountedMortal(_PyStackRef ref)
-{
-    return (ref.bits & Py_TAG_BITS) == Py_TAG_REFCNT;
-}
-
-/* Does this ref refer to a mortal object (NULL is not mortal) */
-static inline bool
-PyStackRef_IsMortal(_PyStackRef ref)
-{
-    return (ref.bits & Py_TAG_BITS) != Py_TAG_IMMORTAL;
-}
-
 static inline PyObject *
 PyStackRef_AsPyObjectBorrow(_PyStackRef ref)
 {
@@ -547,13 +524,13 @@ PyStackRef_DUP(_PyStackRef ref)
 static inline bool
 PyStackRef_IsHeapSafe(_PyStackRef ref)
 {
-    return !PyStackRef_IsCountedMortal(ref);
+    return (ref.bits & Py_TAG_BITS) == 0 || ref.bits == PyStackRef_NULL_BITS ||  _Py_IsImmortal(BITS_TO_PTR_MASKED(ref));
 }
 
 static inline _PyStackRef
 PyStackRef_MakeHeapSafe(_PyStackRef ref)
 {
-    if (!PyStackRef_IsCountedMortal(ref)) {
+    if (PyStackRef_IsHeapSafe(ref)) {
         return ref;
     }
     PyObject *obj = BITS_TO_PTR_MASKED(ref);

Include/refcount.h

@@ -19,9 +19,8 @@ immortal. The latter should be the only instances that require
 cleanup during runtime finalization.
 */
 
-/* Leave the low bits for refcount overflow for old stable ABI code */
 #define _Py_STATICALLY_ALLOCATED_FLAG 4
-#define _Py_IMMORTAL_FLAGS 3
+#define _Py_IMMORTAL_FLAGS 1
 
 #if SIZEOF_VOID_P > 4
 /*

Python/gc.c

@@ -1488,10 +1488,10 @@ mark_stacks(PyInterpreterState *interp, PyGC_Head *visited, int visited_space, b
             objects_marked += move_to_reachable(func, &reachable, visited_space);
             while (sp > locals) {
                 sp--;
-                if (!PyStackRef_IsMortal(*sp)) {
+                PyObject *op = PyStackRef_AsPyObjectBorrow(*sp);
+                if (op == NULL || _Py_IsImmortal(op)) {
                     continue;
                 }
-                PyObject *op = PyStackRef_AsPyObjectBorrow(*sp);
                 if (_PyObject_IS_GC(op)) {
                     PyGC_Head *gc = AS_GC(op);
                     if (_PyObject_GC_IS_TRACKED(op) &&