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bpo-44337: Improve LOAD_ATTR specialization #26759

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Merged
merged 5 commits into from
Jun 21, 2021
Merged

bpo-44337: Improve LOAD_ATTR specialization #26759

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d8e1017
Improve LOAD_ATTR specialization
markshannon Jun 16, 2021
65524d1
Add stat for how many times the unquickened instruction has executed.
markshannon Jun 16, 2021
d5e7d20
Turn stats off by default
markshannon Jun 16, 2021
3c0b409
Remove unused struct and enum
markshannon Jun 16, 2021
5d9eb10
Don't use reserved identifier.
markshannon Jun 21, 2021
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1 change: 1 addition & 0 deletions Include/internal/pycore_code.h
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Original file line number Diff line number Diff line change
Expand Up @@ -336,6 +336,7 @@ typedef struct _stats {
uint64_t deferred;
uint64_t miss;
uint64_t deopt;
uint64_t unquickened;
#if SPECIALIZATION_STATS_DETAILED
PyObject *miss_types;
#endif
Expand Down
2 changes: 2 additions & 0 deletions Python/ceval.c
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Expand Up @@ -2805,6 +2805,7 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, PyFrameObject *f, int throwflag)

case TARGET(LOAD_GLOBAL): {
PREDICTED(LOAD_GLOBAL);
STAT_INC(LOAD_GLOBAL, unquickened);
PyObject *name = GETITEM(names, oparg);
PyObject *v;
if (PyDict_CheckExact(GLOBALS())
Expand Down Expand Up @@ -3289,6 +3290,7 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, PyFrameObject *f, int throwflag)

case TARGET(LOAD_ATTR): {
PREDICTED(LOAD_ATTR);
STAT_INC(LOAD_ATTR, unquickened);
PyObject *name = GETITEM(names, oparg);
PyObject *owner = TOP();
PyObject *res = PyObject_GetAttr(owner, name);
Expand Down
248 changes: 176 additions & 72 deletions Python/specialize.c
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Original file line number Diff line number Diff line change
Expand Up @@ -47,6 +47,7 @@ print_stats(SpecializationStats *stats, const char *name)
PRINT_STAT(name, deferred);
PRINT_STAT(name, miss);
PRINT_STAT(name, deopt);
PRINT_STAT(name, unquickened);
#if SPECIALIZATION_STATS_DETAILED
if (stats->miss_types == NULL) {
return;
Expand Down Expand Up @@ -302,6 +303,8 @@ _Py_Quicken(PyCodeObject *code) {
return 0;
}



static int
specialize_module_load_attr(
PyObject *owner, _Py_CODEUNIT *instr, PyObject *name,
Expand Down Expand Up @@ -349,6 +352,68 @@ specialize_module_load_attr(
return 0;
}



/* Attribute specialization */

typedef enum {
OVERRIDING, /* Is an overriding descriptor, and will remain so. */
METHOD, /* Attribute has Py_TPFLAGS_METHOD_DESCRIPTOR set */
PROPERTY, /* Is a property */
OBJECT_SLOT, /* Is an object slot descriptor */
OTHER_SLOT, /* Is a slot descriptor of another type */
NON_OVERRIDING, /* Is another non-overriding descriptor, and is an instance of an immutable class*/
NON_DESCRIPTOR, /* Is not a descriptor, and is an instance of an immutable class */
MUTABLE, /* Instance of a mutable class; might, or might not, be a descriptor */
ABSENT, /* Attribute is not present on the class */
DUNDER_CLASS, /* __class__ attribute */
GETATTRIBUTE_OVERRIDDEN /* __getattribute__ has been overridden */
} DesciptorClassification;

static DesciptorClassification
analyze_descriptor(PyTypeObject *type, PyObject *name, PyObject **descr)
{
if (type->tp_getattro != PyObject_GenericGetAttr) {
*descr = NULL;
return GETATTRIBUTE_OVERRIDDEN;
}
PyObject *descriptor = _PyType_Lookup(type, name);
*descr = descriptor;
if (descriptor == NULL) {
return ABSENT;
}
PyTypeObject *desc_cls = Py_TYPE(descriptor);
if (!(desc_cls->tp_flags & Py_TPFLAGS_IMMUTABLETYPE)) {
return MUTABLE;
}
if (desc_cls->tp_descr_set) {
if (desc_cls == &PyMemberDescr_Type) {
PyMemberDescrObject *member = (PyMemberDescrObject *)descriptor;
struct PyMemberDef *dmem = member->d_member;
if (dmem->type == T_OBJECT_EX) {
return OBJECT_SLOT;
}
return OTHER_SLOT;
}
if (desc_cls == &PyProperty_Type) {
return PROPERTY;
}
if (PyUnicode_CompareWithASCIIString(name, "__class__") == 0) {
if (descriptor == _PyType_Lookup(&PyBaseObject_Type, name)) {
return DUNDER_CLASS;
}
}
return OVERRIDING;
}
if (desc_cls->tp_descr_get) {
if (desc_cls->tp_flags & Py_TPFLAGS_METHOD_DESCRIPTOR) {
return METHOD;
}
return NON_OVERRIDING;
}
return NON_DESCRIPTOR;
}

int
_Py_Specialize_LoadAttr(PyObject *owner, _Py_CODEUNIT *instr, PyObject *name, SpecializedCacheEntry *cache)
{
Expand All @@ -362,94 +427,134 @@ _Py_Specialize_LoadAttr(PyObject *owner, _Py_CODEUNIT *instr, PyObject *name, Sp
goto success;
}
PyTypeObject *type = Py_TYPE(owner);
if (type->tp_getattro != PyObject_GenericGetAttr) {
SPECIALIZATION_FAIL(LOAD_ATTR, Py_TYPE(owner), name, "__getattribute__ overridden");
goto fail;
}
if (type->tp_dict == NULL) {
if (PyType_Ready(type) < 0) {
return -1;
}
}
PyObject *descr = _PyType_Lookup(type, name);
if (descr != NULL) {
// We found an attribute with a data-like descriptor.
PyTypeObject *dtype = Py_TYPE(descr);
if (dtype != &PyMemberDescr_Type) {
SPECIALIZATION_FAIL(LOAD_ATTR, Py_TYPE(owner), name, "not a member descriptor");
PyObject *descr;
DesciptorClassification kind = analyze_descriptor(type, name, &descr);
switch(kind) {
case OVERRIDING:
SPECIALIZATION_FAIL(LOAD_ATTR, type, name, "overriding descriptor");
goto fail;
}
// It's a slot
PyMemberDescrObject *member = (PyMemberDescrObject *)descr;
struct PyMemberDef *dmem = member->d_member;
if (dmem->type != T_OBJECT_EX) {
SPECIALIZATION_FAIL(LOAD_ATTR, Py_TYPE(owner), name, "non-object slot");
case METHOD:
SPECIALIZATION_FAIL(LOAD_ATTR, type, name, "method");
goto fail;
}
Py_ssize_t offset = dmem->offset;
if (offset != (uint16_t)offset) {
SPECIALIZATION_FAIL(LOAD_ATTR, Py_TYPE(owner), name, "offset out of range");
case PROPERTY:
SPECIALIZATION_FAIL(LOAD_ATTR, type, name, "property");
goto fail;
case OBJECT_SLOT:
{
PyMemberDescrObject *member = (PyMemberDescrObject *)descr;
struct PyMemberDef *dmem = member->d_member;
Py_ssize_t offset = dmem->offset;
if (offset != (uint16_t)offset) {
SPECIALIZATION_FAIL(LOAD_ATTR, type, name, "offset out of range");
goto fail;
}
assert(dmem->type == T_OBJECT_EX);
assert(offset > 0);
cache0->index = (uint16_t)offset;
cache1->tp_version = type->tp_version_tag;
*instr = _Py_MAKECODEUNIT(LOAD_ATTR_SLOT, _Py_OPARG(*instr));
goto success;
}
assert(offset > 0);
cache0->index = (uint16_t)offset;
cache1->tp_version = type->tp_version_tag;
*instr = _Py_MAKECODEUNIT(LOAD_ATTR_SLOT, _Py_OPARG(*instr));
goto success;
}
// No desciptor
if (type->tp_dictoffset <= 0) {
SPECIALIZATION_FAIL(LOAD_ATTR, Py_TYPE(owner), name, "no dict or negative offset");
goto fail;
}
PyObject **dictptr = (PyObject **) ((char *)owner + type->tp_dictoffset);
if (*dictptr == NULL || !PyDict_CheckExact(*dictptr)) {
SPECIALIZATION_FAIL(LOAD_ATTR, Py_TYPE(owner), name, "no dict or not a dict");
case DUNDER_CLASS:
{
Py_ssize_t offset = offsetof(PyObject, ob_type);
assert(offset == (uint16_t)offset);
cache0->index = (uint16_t)offset;
cache1->tp_version = type->tp_version_tag;
*instr = _Py_MAKECODEUNIT(LOAD_ATTR_SLOT, _Py_OPARG(*instr));
goto success;
}
case OTHER_SLOT:
SPECIALIZATION_FAIL(LOAD_ATTR, type, name, "non-object slot");
goto fail;
case MUTABLE:
SPECIALIZATION_FAIL(LOAD_ATTR, type, name, "mutable class attribute");
goto fail;
case GETATTRIBUTE_OVERRIDDEN:
SPECIALIZATION_FAIL(LOAD_ATTR, type, name, "__getattribute__ overridden");
goto fail;
case NON_OVERRIDING:
case NON_DESCRIPTOR:
case ABSENT:
break;
}
assert(kind == NON_OVERRIDING || kind == NON_DESCRIPTOR || kind == ABSENT);
// No desciptor, or non overriding.
if (type->tp_dictoffset < 0) {
SPECIALIZATION_FAIL(LOAD_ATTR, type, name, "negative offset");
goto fail;
}
// We found an instance with a __dict__.
PyDictObject *dict = (PyDictObject *)*dictptr;
if ((type->tp_flags & Py_TPFLAGS_HEAPTYPE)
&& dict->ma_keys == ((PyHeapTypeObject*)type)->ht_cached_keys
) {
// Keys are shared
assert(PyUnicode_CheckExact(name));
Py_hash_t hash = PyObject_Hash(name);
if (hash == -1) {
return -1;
}
PyObject *value;
Py_ssize_t index = _Py_dict_lookup(dict, name, hash, &value);
assert (index != DKIX_ERROR);
if (index != (uint16_t)index) {
SPECIALIZATION_FAIL(LOAD_ATTR, Py_TYPE(owner), name, "index out of range");
if (type->tp_dictoffset > 0) {
PyObject **dictptr = (PyObject **) ((char *)owner + type->tp_dictoffset);
if (*dictptr == NULL || !PyDict_CheckExact(*dictptr)) {
SPECIALIZATION_FAIL(LOAD_ATTR, type, name, "no dict or not a dict");
goto fail;
}
uint32_t keys_version = _PyDictKeys_GetVersionForCurrentState(dict);
if (keys_version == 0) {
SPECIALIZATION_FAIL(LOAD_ATTR, Py_TYPE(owner), name, "no more key versions");
goto fail;
// We found an instance with a __dict__.
PyDictObject *dict = (PyDictObject *)*dictptr;
if ((type->tp_flags & Py_TPFLAGS_HEAPTYPE)
&& dict->ma_keys == ((PyHeapTypeObject*)type)->ht_cached_keys
) {
// Keys are shared
assert(PyUnicode_CheckExact(name));
Py_hash_t hash = PyObject_Hash(name);
if (hash == -1) {
return -1;
}
PyObject *value;
Py_ssize_t index = _Py_dict_lookup(dict, name, hash, &value);
assert (index != DKIX_ERROR);
if (index != (uint16_t)index) {
SPECIALIZATION_FAIL(LOAD_ATTR, type, name,
index < 0 ? "attribute not in dict" : "index out of range");
goto fail;
}
uint32_t keys_version = _PyDictKeys_GetVersionForCurrentState(dict);
if (keys_version == 0) {
SPECIALIZATION_FAIL(LOAD_ATTR, type, name, "no more key versions");
goto fail;
}
cache1->dk_version_or_hint = keys_version;
cache1->tp_version = type->tp_version_tag;
cache0->index = (uint16_t)index;
*instr = _Py_MAKECODEUNIT(LOAD_ATTR_SPLIT_KEYS, _Py_OPARG(*instr));
goto success;
}
else {
PyObject *value = NULL;
Py_ssize_t hint =
_PyDict_GetItemHint(dict, name, -1, &value);
if (hint != (uint32_t)hint) {
SPECIALIZATION_FAIL(LOAD_ATTR, type, name, "hint out of range");
goto fail;
}
cache1->dk_version_or_hint = (uint32_t)hint;
cache1->tp_version = type->tp_version_tag;
*instr = _Py_MAKECODEUNIT(LOAD_ATTR_WITH_HINT, _Py_OPARG(*instr));
goto success;
}
cache1->dk_version_or_hint = keys_version;
cache1->tp_version = type->tp_version_tag;
cache0->index = (uint16_t)index;
*instr = _Py_MAKECODEUNIT(LOAD_ATTR_SPLIT_KEYS, _Py_OPARG(*instr));
goto success;
}
else {
PyObject *value = NULL;
Py_ssize_t hint =
_PyDict_GetItemHint(dict, name, -1, &value);
if (hint != (uint32_t)hint) {
SPECIALIZATION_FAIL(LOAD_ATTR, Py_TYPE(owner), name, "hint out of range");
assert(type->tp_dictoffset == 0);
/* No attribute in instance dictionary */
switch(kind) {
case NON_OVERRIDING:
SPECIALIZATION_FAIL(LOAD_ATTR, type, name, "non-overriding descriptor");
goto fail;
}
cache1->dk_version_or_hint = (uint32_t)hint;
cache1->tp_version = type->tp_version_tag;
*instr = _Py_MAKECODEUNIT(LOAD_ATTR_WITH_HINT, _Py_OPARG(*instr));
goto success;
case NON_DESCRIPTOR:
/* To do -- Optimize this case */
SPECIALIZATION_FAIL(LOAD_ATTR, type, name, "non descriptor");
goto fail;
case ABSENT:
SPECIALIZATION_FAIL(LOAD_ATTR, type, name, "no attribute");
goto fail;
default:
Py_UNREACHABLE();
}

fail:
STAT_INC(LOAD_ATTR, specialization_failure);
assert(!PyErr_Occurred());
Expand All @@ -462,7 +567,6 @@ _Py_Specialize_LoadAttr(PyObject *owner, _Py_CODEUNIT *instr, PyObject *name, Sp
return 0;
}


int
_Py_Specialize_LoadGlobal(
PyObject *globals, PyObject *builtins,
Expand Down