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GH-100288: Skip extra work when failing to specialize LOAD_ATTR #101354

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Merged
merged 2 commits into from
Jan 31, 2023
Merged

GH-100288: Skip extra work when failing to specialize LOAD_ATTR #101354

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d6dcb34
Remove old branch
brandtbucher Jan 17, 2023
b1845b6
Simplify method load specialization
brandtbucher Jan 18, 2023
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84 changes: 24 additions & 60 deletions Python/specialize.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1039,14 +1039,6 @@ specialize_class_load_attr(PyObject *owner, _Py_CODEUNIT *instr,
}
}

typedef enum {
MANAGED_VALUES = 1,
MANAGED_DICT = 2,
OFFSET_DICT = 3,
NO_DICT = 4,
LAZY_DICT = 5,
} ObjectDictKind;

// Please collect stats carefully before and after modifying. A subtle change
// can cause a significant drop in cache hits. A possible test is
// python.exe -m test_typing test_re test_dis test_zlib.
Expand All @@ -1058,71 +1050,45 @@ PyObject *descr, DescriptorClassification kind)
PyTypeObject *owner_cls = Py_TYPE(owner);

assert(kind == METHOD && descr != NULL);
ObjectDictKind dictkind;
PyDictKeysObject *keys;
if (owner_cls->tp_flags & Py_TPFLAGS_MANAGED_DICT) {
PyDictOrValues dorv = *_PyObject_DictOrValuesPointer(owner);
keys = ((PyHeapTypeObject *)owner_cls)->ht_cached_keys;
if (_PyDictOrValues_IsValues(dorv)) {
dictkind = MANAGED_VALUES;
}
else {
dictkind = MANAGED_DICT;
}
}
else {
Py_ssize_t dictoffset = owner_cls->tp_dictoffset;
if (dictoffset < 0 || dictoffset > INT16_MAX) {
SPECIALIZATION_FAIL(LOAD_ATTR, SPEC_FAIL_OUT_OF_RANGE);
goto fail;
}
if (dictoffset == 0) {
dictkind = NO_DICT;
keys = NULL;
}
else {
PyObject *dict = *(PyObject **) ((char *)owner + dictoffset);
if (dict == NULL) {
// This object will have a dict if user access __dict__
dictkind = LAZY_DICT;
keys = NULL;
}
else {
keys = ((PyDictObject *)dict)->ma_keys;
dictkind = OFFSET_DICT;
}
PyDictKeysObject *keys = ((PyHeapTypeObject *)owner_cls)->ht_cached_keys;
if (!_PyDictOrValues_IsValues(dorv)) {
SPECIALIZATION_FAIL(LOAD_ATTR, SPEC_FAIL_ATTR_HAS_MANAGED_DICT);
return 0;
}
}
if (dictkind == MANAGED_VALUES || dictkind == OFFSET_DICT) {
Py_ssize_t index = _PyDictKeys_StringLookup(keys, name);
if (index != DKIX_EMPTY) {
SPECIALIZATION_FAIL(LOAD_ATTR, SPEC_FAIL_ATTR_SHADOWED);
goto fail;
return 0;
}
uint32_t keys_version = _PyDictKeys_GetVersionForCurrentState(keys);
if (keys_version == 0) {
SPECIALIZATION_FAIL(LOAD_ATTR, SPEC_FAIL_OUT_OF_VERSIONS);
goto fail;
return 0;
}
write_u32(cache->keys_version, keys_version);
_py_set_opcode(instr, LOAD_ATTR_METHOD_WITH_VALUES);
}
switch(dictkind) {
case NO_DICT:
else {
Py_ssize_t dictoffset = owner_cls->tp_dictoffset;
if (dictoffset < 0 || dictoffset > INT16_MAX) {
SPECIALIZATION_FAIL(LOAD_ATTR, SPEC_FAIL_OUT_OF_RANGE);
return 0;
}
if (dictoffset == 0) {
_py_set_opcode(instr, LOAD_ATTR_METHOD_NO_DICT);
break;
case MANAGED_VALUES:
_py_set_opcode(instr, LOAD_ATTR_METHOD_WITH_VALUES);
break;
case MANAGED_DICT:
SPECIALIZATION_FAIL(LOAD_ATTR, SPEC_FAIL_ATTR_HAS_MANAGED_DICT);
goto fail;
case OFFSET_DICT:
SPECIALIZATION_FAIL(LOAD_ATTR, SPEC_FAIL_ATTR_NOT_MANAGED_DICT);
goto fail;
case LAZY_DICT:
assert(owner_cls->tp_dictoffset > 0 && owner_cls->tp_dictoffset <= INT16_MAX);
}
else {
PyObject *dict = *(PyObject **) ((char *)owner + dictoffset);
if (dict) {
SPECIALIZATION_FAIL(LOAD_ATTR, SPEC_FAIL_ATTR_NOT_MANAGED_DICT);
return 0;
}
assert(owner_cls->tp_dictoffset > 0);
assert(owner_cls->tp_dictoffset <= INT16_MAX);
_py_set_opcode(instr, LOAD_ATTR_METHOD_LAZY_DICT);
break;
}
}
/* `descr` is borrowed. This is safe for methods (even inherited ones from
* super classes!) as long as tp_version_tag is validated for two main reasons:
Expand All @@ -1141,8 +1107,6 @@ PyObject *descr, DescriptorClassification kind)
write_u32(cache->type_version, owner_cls->tp_version_tag);
write_obj(cache->descr, descr);
return 1;
fail:
return 0;
}

void
Expand Down