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GH-95245: Store object values and dict pointers in single tagged poin…
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…ter. (GH-95278)
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@markshannon
markshannon authored Aug 1, 2022
1 parent fb75d01 commit de388c0
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Showing 10 changed files with 269 additions and 201 deletions.
3 changes: 0 additions & 3 deletions Include/cpython/dictobject.h
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Original file line number Diff line number Diff line change
Expand Up @@ -83,6 +83,3 @@ typedef struct {

PyAPI_FUNC(PyObject *) _PyDictView_New(PyObject *, PyTypeObject *);
PyAPI_FUNC(PyObject *) _PyDictView_Intersect(PyObject* self, PyObject *other);

PyAPI_FUNC(int) _PyObject_VisitManagedDict(PyObject *self, visitproc visit, void *arg);
PyAPI_FUNC(void) _PyObject_ClearManagedDict(PyObject *self);
4 changes: 4 additions & 0 deletions Include/cpython/object.h
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Original file line number Diff line number Diff line change
Expand Up @@ -510,3 +510,7 @@ Py_DEPRECATED(3.11) typedef int UsingDeprecatedTrashcanMacro;
#define Py_TRASHCAN_SAFE_END(op) \
Py_TRASHCAN_END; \
} while(0);


PyAPI_FUNC(int) _PyObject_VisitManagedDict(PyObject *obj, visitproc visit, void *arg);
PyAPI_FUNC(void) _PyObject_ClearManagedDict(PyObject *obj);
43 changes: 34 additions & 9 deletions Include/internal/pycore_object.h
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Original file line number Diff line number Diff line change
Expand Up @@ -274,24 +274,49 @@ extern int _PyObject_StoreInstanceAttribute(PyObject *obj, PyDictValues *values,
PyObject * _PyObject_GetInstanceAttribute(PyObject *obj, PyDictValues *values,
PyObject *name);

static inline PyDictValues **_PyObject_ValuesPointer(PyObject *obj)
typedef union {
PyObject *dict;
/* Use a char* to generate a warning if directly assigning a PyDictValues */
char *values;
} PyDictOrValues;

static inline PyDictOrValues *
_PyObject_DictOrValuesPointer(PyObject *obj)
{
assert(Py_TYPE(obj)->tp_flags & Py_TPFLAGS_MANAGED_DICT);
return ((PyDictValues **)obj)-4;
return ((PyDictOrValues *)obj)-3;
}

static inline PyObject **_PyObject_ManagedDictPointer(PyObject *obj)
static inline int
_PyDictOrValues_IsValues(PyDictOrValues dorv)
{
assert(Py_TYPE(obj)->tp_flags & Py_TPFLAGS_MANAGED_DICT);
return ((PyObject **)obj)-3;
return ((uintptr_t)dorv.values) & 1;
}

static inline PyDictValues *
_PyDictOrValues_GetValues(PyDictOrValues dorv)
{
assert(_PyDictOrValues_IsValues(dorv));
return (PyDictValues *)(dorv.values + 1);
}

static inline PyObject *
_PyDictOrValues_GetDict(PyDictOrValues dorv)
{
assert(!_PyDictOrValues_IsValues(dorv));
return dorv.dict;
}

static inline void
_PyDictOrValues_SetValues(PyDictOrValues *ptr, PyDictValues *values)
{
ptr->values = ((char *)values) - 1;
}

#define MANAGED_DICT_OFFSET (((int)sizeof(PyObject *))*-3)

extern PyObject ** _PyObject_DictPointer(PyObject *);
extern int _PyObject_VisitInstanceAttributes(PyObject *self, visitproc visit, void *arg);
extern void _PyObject_ClearInstanceAttributes(PyObject *self);
extern void _PyObject_FreeInstanceAttributes(PyObject *self);
extern PyObject ** _PyObject_ComputedDictPointer(PyObject *);
extern void _PyObject_FreeInstanceAttributes(PyObject *obj);
extern int _PyObject_IsInstanceDictEmpty(PyObject *);
extern PyObject* _PyType_GetSubclasses(PyTypeObject *);

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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2022-07-26-12-59-03.gh-issue-95245.GHWczn.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Merge managed dict and values pointer into a single tagged pointer to save
one word in the pre-header.
161 changes: 90 additions & 71 deletions Objects/dictobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -5368,7 +5368,7 @@ init_inline_values(PyObject *obj, PyTypeObject *tp)
for (int i = 0; i < size; i++) {
values->values[i] = NULL;
}
*_PyObject_ValuesPointer(obj) = values;
_PyDictOrValues_SetValues(_PyObject_DictOrValuesPointer(obj), values);
return 0;
}

Expand All @@ -5394,7 +5394,7 @@ _PyObject_InitializeDict(PyObject *obj)
if (dict == NULL) {
return -1;
}
PyObject **dictptr = _PyObject_DictPointer(obj);
PyObject **dictptr = _PyObject_ComputedDictPointer(obj);
*dictptr = dict;
return 0;
}
Expand Down Expand Up @@ -5422,7 +5422,6 @@ make_dict_from_instance_attributes(PyDictKeysObject *keys, PyDictValues *values)
PyObject *
_PyObject_MakeDictFromInstanceAttributes(PyObject *obj, PyDictValues *values)
{
assert(Py_TYPE(obj)->tp_flags & Py_TPFLAGS_MANAGED_DICT);
PyDictKeysObject *keys = CACHED_KEYS(Py_TYPE(obj));
OBJECT_STAT_INC(dict_materialized_on_request);
return make_dict_from_instance_attributes(keys, values);
Expand Down Expand Up @@ -5458,8 +5457,7 @@ _PyObject_StoreInstanceAttribute(PyObject *obj, PyDictValues *values,
if (dict == NULL) {
return -1;
}
*_PyObject_ValuesPointer(obj) = NULL;
*_PyObject_ManagedDictPointer(obj) = dict;
_PyObject_DictOrValuesPointer(obj)->dict = dict;
if (value == NULL) {
return PyDict_DelItem(dict, name);
}
Expand Down Expand Up @@ -5488,6 +5486,37 @@ _PyObject_StoreInstanceAttribute(PyObject *obj, PyDictValues *values,
return 0;
}

/* Sanity check for managed dicts */
#if 0
#define CHECK(val) assert(val); if (!(val)) { return 0; }

int
_PyObject_ManagedDictValidityCheck(PyObject *obj)
{
PyTypeObject *tp = Py_TYPE(obj);
CHECK(tp->tp_flags & Py_TPFLAGS_MANAGED_DICT);
PyDictOrValues *dorv_ptr = _PyObject_DictOrValuesPointer(obj);
if (_PyDictOrValues_IsValues(*dorv_ptr)) {
PyDictValues *values = _PyDictOrValues_GetValues(*dorv_ptr);
int size = ((uint8_t *)values)[-2];
int count = 0;
PyDictKeysObject *keys = CACHED_KEYS(tp);
for (Py_ssize_t i = 0; i < keys->dk_nentries; i++) {
if (values->values[i] != NULL) {
count++;
}
}
CHECK(size == count);
}
else {
if (dorv_ptr->dict != NULL) {
CHECK(PyDict_Check(dorv_ptr->dict));
}
}
return 1;
}
#endif

PyObject *
_PyObject_GetInstanceAttribute(PyObject *obj, PyDictValues *values,
PyObject *name)
Expand All @@ -5511,105 +5540,94 @@ _PyObject_IsInstanceDictEmpty(PyObject *obj)
if (tp->tp_dictoffset == 0) {
return 1;
}
PyObject **dictptr;
PyObject *dict;
if (tp->tp_flags & Py_TPFLAGS_MANAGED_DICT) {
PyDictValues *values = *_PyObject_ValuesPointer(obj);
if (values) {
PyDictOrValues dorv = *_PyObject_DictOrValuesPointer(obj);
if (_PyDictOrValues_IsValues(dorv)) {
PyDictKeysObject *keys = CACHED_KEYS(tp);
for (Py_ssize_t i = 0; i < keys->dk_nentries; i++) {
if (values->values[i] != NULL) {
if (_PyDictOrValues_GetValues(dorv)->values[i] != NULL) {
return 0;
}
}
return 1;
}
dictptr = _PyObject_ManagedDictPointer(obj);
dict = _PyDictOrValues_GetDict(dorv);
}
else {
dictptr = _PyObject_DictPointer(obj);
PyObject **dictptr = _PyObject_ComputedDictPointer(obj);
dict = *dictptr;
}
PyObject *dict = *dictptr;
if (dict == NULL) {
return 1;
}
return ((PyDictObject *)dict)->ma_used == 0;
}


int
_PyObject_VisitInstanceAttributes(PyObject *self, visitproc visit, void *arg)
{
PyTypeObject *tp = Py_TYPE(self);
assert(Py_TYPE(self)->tp_flags & Py_TPFLAGS_MANAGED_DICT);
PyDictValues **values_ptr = _PyObject_ValuesPointer(self);
if (*values_ptr == NULL) {
return 0;
}
PyDictKeysObject *keys = CACHED_KEYS(tp);
for (Py_ssize_t i = 0; i < keys->dk_nentries; i++) {
Py_VISIT((*values_ptr)->values[i]);
}
return 0;
}

void
_PyObject_ClearInstanceAttributes(PyObject *self)
{
PyTypeObject *tp = Py_TYPE(self);
assert(Py_TYPE(self)->tp_flags & Py_TPFLAGS_MANAGED_DICT);
PyDictValues **values_ptr = _PyObject_ValuesPointer(self);
if (*values_ptr == NULL) {
return;
}
PyDictKeysObject *keys = CACHED_KEYS(tp);
for (Py_ssize_t i = 0; i < keys->dk_nentries; i++) {
Py_CLEAR((*values_ptr)->values[i]);
}
}

void
_PyObject_FreeInstanceAttributes(PyObject *self)
{
PyTypeObject *tp = Py_TYPE(self);
assert(Py_TYPE(self)->tp_flags & Py_TPFLAGS_MANAGED_DICT);
PyDictValues **values_ptr = _PyObject_ValuesPointer(self);
if (*values_ptr == NULL) {
PyDictOrValues dorv = *_PyObject_DictOrValuesPointer(self);
if (!_PyDictOrValues_IsValues(dorv)) {
return;
}
PyDictValues *values = _PyDictOrValues_GetValues(dorv);
PyDictKeysObject *keys = CACHED_KEYS(tp);
for (Py_ssize_t i = 0; i < keys->dk_nentries; i++) {
Py_XDECREF((*values_ptr)->values[i]);
Py_XDECREF(values->values[i]);
}
free_values(*values_ptr);
free_values(values);
}

int
_PyObject_VisitManagedDict(PyObject *self, visitproc visit, void *arg)
_PyObject_VisitManagedDict(PyObject *obj, visitproc visit, void *arg)
{
PyTypeObject *tp = Py_TYPE(self);
PyTypeObject *tp = Py_TYPE(obj);
if((tp->tp_flags & Py_TPFLAGS_MANAGED_DICT) == 0) {
return 0;
}
assert(tp->tp_dictoffset);
int err = _PyObject_VisitInstanceAttributes(self, visit, arg);
if (err) {
return err;
PyDictOrValues dorv = *_PyObject_DictOrValuesPointer(obj);
if (_PyDictOrValues_IsValues(dorv)) {
PyDictValues *values = _PyDictOrValues_GetValues(dorv);
PyDictKeysObject *keys = CACHED_KEYS(tp);
for (Py_ssize_t i = 0; i < keys->dk_nentries; i++) {
Py_VISIT(values->values[i]);
}
}
else {
PyObject *dict = _PyDictOrValues_GetDict(dorv);
Py_VISIT(dict);
}
Py_VISIT(*_PyObject_ManagedDictPointer(self));
return 0;
}


void
_PyObject_ClearManagedDict(PyObject *self)
_PyObject_ClearManagedDict(PyObject *obj)
{
PyTypeObject *tp = Py_TYPE(self);
PyTypeObject *tp = Py_TYPE(obj);
if((tp->tp_flags & Py_TPFLAGS_MANAGED_DICT) == 0) {
return;
}
_PyObject_FreeInstanceAttributes(self);
*_PyObject_ValuesPointer(self) = NULL;
Py_CLEAR(*_PyObject_ManagedDictPointer(self));
PyDictOrValues *dorv_ptr = _PyObject_DictOrValuesPointer(obj);
if (_PyDictOrValues_IsValues(*dorv_ptr)) {
PyDictValues *values = _PyDictOrValues_GetValues(*dorv_ptr);
PyDictKeysObject *keys = CACHED_KEYS(tp);
for (Py_ssize_t i = 0; i < keys->dk_nentries; i++) {
Py_CLEAR(values->values[i]);
}
dorv_ptr->dict = NULL;
free_values(values);
}
else {
PyObject *dict = dorv_ptr->dict;
if (dict) {
dorv_ptr->dict = NULL;
Py_DECREF(dict);
}
}
}

PyObject *
Expand All @@ -5618,25 +5636,26 @@ PyObject_GenericGetDict(PyObject *obj, void *context)
PyObject *dict;
PyTypeObject *tp = Py_TYPE(obj);
if (_PyType_HasFeature(tp, Py_TPFLAGS_MANAGED_DICT)) {
PyDictValues **values_ptr = _PyObject_ValuesPointer(obj);
PyObject **dictptr = _PyObject_ManagedDictPointer(obj);
if (*values_ptr) {
assert(*dictptr == NULL);
PyDictOrValues *dorv_ptr = _PyObject_DictOrValuesPointer(obj);
if (_PyDictOrValues_IsValues(*dorv_ptr)) {
PyDictValues *values = _PyDictOrValues_GetValues(*dorv_ptr);
OBJECT_STAT_INC(dict_materialized_on_request);
*dictptr = dict = make_dict_from_instance_attributes(CACHED_KEYS(tp), *values_ptr);
dict = make_dict_from_instance_attributes(CACHED_KEYS(tp), values);
if (dict != NULL) {
*values_ptr = NULL;
dorv_ptr->dict = dict;
}
}
else if (*dictptr == NULL) {
*dictptr = dict = PyDict_New();
}
else {
dict = *dictptr;
dict = _PyDictOrValues_GetDict(*dorv_ptr);
if (dict == NULL) {
dictkeys_incref(CACHED_KEYS(tp));
dict = new_dict_with_shared_keys(CACHED_KEYS(tp));
dorv_ptr->dict = dict;
}
}
}
else {
PyObject **dictptr = _PyObject_DictPointer(obj);
PyObject **dictptr = _PyObject_ComputedDictPointer(obj);
if (dictptr == NULL) {
PyErr_SetString(PyExc_AttributeError,
"This object has no __dict__");
Expand Down
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