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bpo-45340: Don't create object dictionaries unless actually needed (GH-28802)

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* Never change types' cached keys. It could invalidate inline attribute objects.

* Lazily create object dictionaries.

* Update specialization of LOAD/STORE_ATTR.

* Don't update shared keys version for deletion of value.

* Update gdb support to handle instance values.

* Rename SPLIT_KEYS opcodes to INSTANCE_VALUE.
This commit is contained in:
Mark Shannon 2021-10-13 14:19:34 +01:00 • committed by GitHub
parent 97308dfcdc
commit a8b9350964
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GPG key ID: 4AEE18F83AFDEB23
18 changed files with 721 additions and 400 deletions
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72
Python/ceval.c
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@ -3618,7 +3618,7 @@ check_eval_breaker:
}
}
TARGET(LOAD_ATTR_SPLIT_KEYS) {
TARGET(LOAD_ATTR_INSTANCE_VALUE) {
assert(cframe.use_tracing == 0);
PyObject *owner = TOP();
PyObject *res;
@ -3629,11 +3629,10 @@ check_eval_breaker:
assert(cache1->tp_version != 0);
DEOPT_IF(tp->tp_version_tag != cache1->tp_version, LOAD_ATTR);
assert(tp->tp_dictoffset > 0);
PyDictObject *dict = *(PyDictObject **)(((char *)owner) + tp->tp_dictoffset);
DEOPT_IF(dict == NULL, LOAD_ATTR);
assert(PyDict_CheckExact((PyObject *)dict));
DEOPT_IF(dict->ma_keys->dk_version != cache1->dk_version_or_hint, LOAD_ATTR);
res = dict->ma_values->values[cache0->index];
assert(tp->tp_inline_values_offset > 0);
PyDictValues *values = *(PyDictValues **)(((char *)owner) + tp->tp_inline_values_offset);
DEOPT_IF(values == NULL, LOAD_ATTR);
res = values->values[cache0->index];
DEOPT_IF(res == NULL, LOAD_ATTR);
STAT_INC(LOAD_ATTR, hit);
record_cache_hit(cache0);
@ -3725,7 +3724,7 @@ check_eval_breaker:
}
}
TARGET(STORE_ATTR_SPLIT_KEYS) {
TARGET(STORE_ATTR_INSTANCE_VALUE) {
assert(cframe.use_tracing == 0);
PyObject *owner = TOP();
PyTypeObject *tp = Py_TYPE(owner);
@ -3735,31 +3734,23 @@ check_eval_breaker:
assert(cache1->tp_version != 0);
DEOPT_IF(tp->tp_version_tag != cache1->tp_version, STORE_ATTR);
assert(tp->tp_dictoffset > 0);
PyDictObject *dict = *(PyDictObject **)(((char *)owner) + tp->tp_dictoffset);
DEOPT_IF(dict == NULL, STORE_ATTR);
assert(PyDict_CheckExact((PyObject *)dict));
DEOPT_IF(dict->ma_keys->dk_version != cache1->dk_version_or_hint, STORE_ATTR);
assert(tp->tp_inline_values_offset > 0);
PyDictValues *values = *(PyDictValues **)(((char *)owner) + tp->tp_inline_values_offset);
DEOPT_IF(values == NULL, STORE_ATTR);
STAT_INC(STORE_ATTR, hit);
record_cache_hit(cache0);
int index = cache0->index;
STACK_SHRINK(1);
PyObject *value = POP();
PyObject *old_value = dict->ma_values->values[index];
dict->ma_values->values[index] = value;
PyObject *old_value = values->values[index];
values->values[index] = value;
if (old_value == NULL) {
assert(index < 16);
dict->ma_values->mv_order = (dict->ma_values->mv_order << 4) | index;
dict->ma_used++;
values->mv_order = (values->mv_order << 4) | index;
}
else {
Py_DECREF(old_value);
}
/* Ensure dict is GC tracked if it needs to be */
if (!_PyObject_GC_IS_TRACKED(dict) && _PyObject_GC_MAY_BE_TRACKED(value)) {
_PyObject_GC_TRACK(dict);
}
/* PEP 509 */
dict->ma_version_tag = DICT_NEXT_VERSION();
Py_DECREF(owner);
DISPATCH();
}
@ -4474,21 +4465,31 @@ check_eval_breaker:
_PyObjectCache *cache2 = &caches[-2].obj;
DEOPT_IF(self_cls->tp_version_tag != cache1->tp_version, LOAD_METHOD);
assert(cache1->dk_version_or_hint != 0);
assert(cache1->tp_version != 0);
assert(self_cls->tp_dictoffset >= 0);
assert(Py_TYPE(self_cls)->tp_dictoffset > 0);
// inline version of _PyObject_GetDictPtr for offset >= 0
PyObject *dict = self_cls->tp_dictoffset != 0 ?
*(PyObject **) ((char *)self + self_cls->tp_dictoffset) : NULL;
// Ensure self.__dict__ didn't modify keys.
// Don't care if self has no dict, it could be builtin or __slots__.
DEOPT_IF(dict != NULL &&
((PyDictObject *)dict)->ma_keys->dk_version !=
cache1->dk_version_or_hint, LOAD_METHOD);
assert(self_cls->tp_dictoffset > 0);
assert(self_cls->tp_inline_values_offset > 0);
PyDictObject *dict = *(PyDictObject **)(((char *)self) + self_cls->tp_dictoffset);
DEOPT_IF(dict != NULL, LOAD_METHOD);
DEOPT_IF(((PyHeapTypeObject *)self_cls)->ht_cached_keys->dk_version != cache1->dk_version_or_hint, LOAD_METHOD);
STAT_INC(LOAD_METHOD, hit);
record_cache_hit(cache0);
PyObject *res = cache2->obj;
assert(res != NULL);
assert(_PyType_HasFeature(Py_TYPE(res), Py_TPFLAGS_METHOD_DESCRIPTOR));
Py_INCREF(res);
SET_TOP(res);
PUSH(self);
DISPATCH();
}
TARGET(LOAD_METHOD_NO_DICT) {
PyObject *self = TOP();
PyTypeObject *self_cls = Py_TYPE(self);
SpecializedCacheEntry *caches = GET_CACHE();
_PyAdaptiveEntry *cache0 = &caches[0].adaptive;
_PyAttrCache *cache1 = &caches[-1].attr;
_PyObjectCache *cache2 = &caches[-2].obj;
DEOPT_IF(self_cls->tp_version_tag != cache1->tp_version, LOAD_METHOD);
assert(self_cls->tp_dictoffset == 0);
STAT_INC(LOAD_METHOD, hit);
record_cache_hit(cache0);
PyObject *res = cache2->obj;
@ -4530,7 +4531,6 @@ check_eval_breaker:
record_cache_hit(cache0);
PyObject *res = cache2->obj;
assert(res != NULL);
assert(_PyType_HasFeature(Py_TYPE(res), Py_TPFLAGS_METHOD_DESCRIPTOR));
Py_INCREF(res);
SET_TOP(NULL);
Py_DECREF(cls);