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bpo-45219: Factor dictkey indexing #28389

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Merged
merged 5 commits into from
Sep 17, 2021
Merged

bpo-45219: Factor dictkey indexing #28389

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1bc75e4
Add _PyDictKeys_StringLookup() function to assist in specialization.
markshannon Sep 16, 2021
5d3dfc2
Change _PyDictKeys_GetVersionForCurrentState to take dict keys, not d…
markshannon Sep 16, 2021
0e9caf6
Use _PyDictKeys_StringLookup when specializing.
markshannon Sep 16, 2021
3e7f3f2
Refactor string lookup for dictkeys.
markshannon Sep 17, 2021
878e458
Merge branch 'main' into factor-dictkey-indexing
markshannon Sep 17, 2021
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4 changes: 3 additions & 1 deletion Include/cpython/dictobject.h
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Original file line number Diff line number Diff line change
Expand Up @@ -85,4 +85,6 @@ PyAPI_FUNC(PyObject *) _PyDictView_Intersect(PyObject* self, PyObject *other);

/* Gets a version number unique to the current state of the keys of dict, if possible.
* Returns the version number, or zero if it was not possible to get a version number. */
uint32_t _PyDictKeys_GetVersionForCurrentState(PyDictObject *dict);
uint32_t _PyDictKeys_GetVersionForCurrentState(PyDictKeysObject *dictkeys);

Py_ssize_t _PyDictKeys_StringLookup(PyDictKeysObject* dictkeys, PyObject *key);
126 changes: 84 additions & 42 deletions Objects/dictobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -734,6 +734,73 @@ lookdict_index(PyDictKeysObject *k, Py_hash_t hash, Py_ssize_t index)
Py_UNREACHABLE();
}

static Py_ssize_t
dictkeys_stringlookup(PyDictKeysObject* dk, PyObject *key, Py_hash_t hash)
{
PyDictKeyEntry *ep0 = DK_ENTRIES(dk);
size_t mask = DK_MASK(dk);
size_t perturb = hash;
size_t i = (size_t)hash & mask;
Py_ssize_t ix;
for (;;) {
ix = dictkeys_get_index(dk, i);
if (ix >= 0) {
PyDictKeyEntry *ep = &ep0[ix];
assert(ep->me_key != NULL);
assert(PyUnicode_CheckExact(ep->me_key));
if (ep->me_key == key ||
(ep->me_hash == hash && unicode_eq(ep->me_key, key))) {
return ix;
}
}
else if (ix == DKIX_EMPTY) {
return DKIX_EMPTY;
}
perturb >>= PERTURB_SHIFT;
i = mask & (i*5 + perturb + 1);
ix = dictkeys_get_index(dk, i);
if (ix >= 0) {
PyDictKeyEntry *ep = &ep0[ix];
assert(ep->me_key != NULL);
assert(PyUnicode_CheckExact(ep->me_key));
if (ep->me_key == key ||
(ep->me_hash == hash && unicode_eq(ep->me_key, key))) {
return ix;
}
}
else if (ix == DKIX_EMPTY) {
return DKIX_EMPTY;
}
perturb >>= PERTURB_SHIFT;
i = mask & (i*5 + perturb + 1);
}
Py_UNREACHABLE();
}

/* Lookup a string in a (all unicode) dict keys.
* Returns DKIX_ERROR if key is not a string,
* or if the dict keys is not all strings.
* If the keys is present then return the index of key.
* If the key is not present then return DKIX_EMPTY.
*/
Py_ssize_t
_PyDictKeys_StringLookup(PyDictKeysObject* dk, PyObject *key)
{
DictKeysKind kind = dk->dk_kind;
if (!PyUnicode_CheckExact(key) || kind == DICT_KEYS_GENERAL) {
return DKIX_ERROR;
}
Py_hash_t hash = ((PyASCIIObject *)key)->hash;
if (hash == -1) {
hash = PyUnicode_Type.tp_hash(key);
if (hash == -1) {
PyErr_Clear();
return DKIX_ERROR;
}
}
return dictkeys_stringlookup(dk, key, hash);
}

/*
The basic lookup function used by all operations.
This is based on Algorithm D from Knuth Vol. 3, Sec. 6.4.
Expand All @@ -756,49 +823,24 @@ _Py_dict_lookup(PyDictObject *mp, PyObject *key, Py_hash_t hash, PyObject **valu
start:
dk = mp->ma_keys;
DictKeysKind kind = dk->dk_kind;
if (PyUnicode_CheckExact(key) && kind != DICT_KEYS_GENERAL) {
Py_ssize_t ix = dictkeys_stringlookup(dk, key, hash);
if (ix == DKIX_EMPTY) {
*value_addr = NULL;
}
else if (kind == DICT_KEYS_SPLIT) {
*value_addr = mp->ma_values[ix];
}
else {
*value_addr = DK_ENTRIES(dk)[ix].me_value;
}
return ix;
}
PyDictKeyEntry *ep0 = DK_ENTRIES(dk);
size_t mask = DK_MASK(dk);
size_t perturb = hash;
size_t i = (size_t)hash & mask;
Py_ssize_t ix;
if (PyUnicode_CheckExact(key) && kind != DICT_KEYS_GENERAL) {
/* Strings only */
for (;;) {
ix = dictkeys_get_index(mp->ma_keys, i);
if (ix >= 0) {
PyDictKeyEntry *ep = &ep0[ix];
assert(ep->me_key != NULL);
assert(PyUnicode_CheckExact(ep->me_key));
if (ep->me_key == key ||
(ep->me_hash == hash && unicode_eq(ep->me_key, key))) {
goto found;
}
}
else if (ix == DKIX_EMPTY) {
*value_addr = NULL;
return DKIX_EMPTY;
}
perturb >>= PERTURB_SHIFT;
i = mask & (i*5 + perturb + 1);
ix = dictkeys_get_index(mp->ma_keys, i);
if (ix >= 0) {
PyDictKeyEntry *ep = &ep0[ix];
assert(ep->me_key != NULL);
assert(PyUnicode_CheckExact(ep->me_key));
if (ep->me_key == key ||
(ep->me_hash == hash && unicode_eq(ep->me_key, key))) {
goto found;
}
}
else if (ix == DKIX_EMPTY) {
*value_addr = NULL;
return DKIX_EMPTY;
}
perturb >>= PERTURB_SHIFT;
i = mask & (i*5 + perturb + 1);
}
Py_UNREACHABLE();
}
for (;;) {
ix = dictkeys_get_index(dk, i);
if (ix == DKIX_EMPTY) {
Expand Down Expand Up @@ -4997,15 +5039,15 @@ _PyDictKeys_DecRef(PyDictKeysObject *keys)

static uint32_t next_dict_keys_version = 2;

uint32_t _PyDictKeys_GetVersionForCurrentState(PyDictObject *dict)
uint32_t _PyDictKeys_GetVersionForCurrentState(PyDictKeysObject *dictkeys)
{
if (dict->ma_keys->dk_version != 0) {
return dict->ma_keys->dk_version;
if (dictkeys->dk_version != 0) {
return dictkeys->dk_version;
}
if (next_dict_keys_version == 0) {
return 0;
}
uint32_t v = next_dict_keys_version++;
dict->ma_keys->dk_version = v;
dictkeys->dk_version = v;
return v;
}
39 changes: 19 additions & 20 deletions Python/specialize.c
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Original file line number Diff line number Diff line change
Expand Up @@ -489,7 +489,7 @@ specialize_module_load_attr(
SPECIALIZATION_FAIL(opcode, SPEC_FAIL_OUT_OF_RANGE);
return -1;
}
uint32_t keys_version = _PyDictKeys_GetVersionForCurrentState(dict);
uint32_t keys_version = _PyDictKeys_GetVersionForCurrentState(dict->ma_keys);
if (keys_version == 0) {
SPECIALIZATION_FAIL(opcode, SPEC_FAIL_OUT_OF_VERSIONS);
return -1;
Expand Down Expand Up @@ -601,23 +601,19 @@ specialize_dict_access(
}
// We found an instance with a __dict__.
PyDictObject *dict = (PyDictObject *)*dictptr;
PyDictKeysObject *keys = dict->ma_keys;
if ((type->tp_flags & Py_TPFLAGS_HEAPTYPE)
&& dict->ma_keys == ((PyHeapTypeObject*)type)->ht_cached_keys
&& 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);
Py_ssize_t index = _PyDictKeys_StringLookup(keys, name);
assert (index != DKIX_ERROR);
if (index != (uint16_t)index) {
SPECIALIZATION_FAIL(base_op, SPEC_FAIL_OUT_OF_RANGE);
return 0;
}
uint32_t keys_version = _PyDictKeys_GetVersionForCurrentState(dict);
uint32_t keys_version = _PyDictKeys_GetVersionForCurrentState(keys);
if (keys_version == 0) {
SPECIALIZATION_FAIL(base_op, SPEC_FAIL_OUT_OF_VERSIONS);
return 0;
Expand Down Expand Up @@ -966,7 +962,7 @@ _Py_Specialize_LoadMethod(PyObject *owner, _Py_CODEUNIT *instr, PyObject *name,
goto fail;
}
}
keys_version = _PyDictKeys_GetVersionForCurrentState(owner_dict);
keys_version = _PyDictKeys_GetVersionForCurrentState(owner_dict->ma_keys);
if (keys_version == 0) {
SPECIALIZATION_FAIL(LOAD_ATTR, SPEC_FAIL_OUT_OF_VERSIONS);
goto fail;
Expand Down Expand Up @@ -1021,17 +1017,17 @@ _Py_Specialize_LoadGlobal(
if (!PyDict_CheckExact(globals)) {
goto fail;
}
if (((PyDictObject *)globals)->ma_keys->dk_kind != DICT_KEYS_UNICODE) {
PyDictKeysObject * globals_keys = ((PyDictObject *)globals)->ma_keys;
Py_ssize_t index = _PyDictKeys_StringLookup(globals_keys, name);
if (index == DKIX_ERROR) {
SPECIALIZATION_FAIL(LOAD_GLOBAL, SPEC_FAIL_NON_STRING_OR_SPLIT);
goto fail;
}
PyObject *value = NULL;
Py_ssize_t index = _PyDict_GetItemHint((PyDictObject *)globals, name, -1, &value);
assert (index != DKIX_ERROR);
if (index != DKIX_EMPTY) {
if (index != (uint16_t)index) {
goto fail;
}
uint32_t keys_version = _PyDictKeys_GetVersionForCurrentState((PyDictObject *)globals);
uint32_t keys_version = _PyDictKeys_GetVersionForCurrentState(globals_keys);
if (keys_version == 0) {
goto fail;
}
Expand All @@ -1043,20 +1039,23 @@ _Py_Specialize_LoadGlobal(
if (!PyDict_CheckExact(builtins)) {
goto fail;
}
if (((PyDictObject *)builtins)->ma_keys->dk_kind != DICT_KEYS_UNICODE) {
PyDictKeysObject * builtin_keys = ((PyDictObject *)builtins)->ma_keys;
index = _PyDictKeys_StringLookup(builtin_keys, name);
if (index == DKIX_ERROR) {
SPECIALIZATION_FAIL(LOAD_GLOBAL, SPEC_FAIL_NON_STRING_OR_SPLIT);
goto fail;
}
index = _PyDict_GetItemHint((PyDictObject *)builtins, name, -1, &value);
assert (index != DKIX_ERROR);
if (index != (uint16_t)index) {
goto fail;
}
uint32_t globals_version = _PyDictKeys_GetVersionForCurrentState((PyDictObject *)globals);
uint32_t globals_version = _PyDictKeys_GetVersionForCurrentState(globals_keys);
if (globals_version == 0) {
SPECIALIZATION_FAIL(LOAD_GLOBAL, SPEC_FAIL_OUT_OF_VERSIONS);
goto fail;
}
uint32_t builtins_version = _PyDictKeys_GetVersionForCurrentState((PyDictObject *)builtins);
uint32_t builtins_version = _PyDictKeys_GetVersionForCurrentState(builtin_keys);
if (builtins_version == 0) {
SPECIALIZATION_FAIL(LOAD_GLOBAL, SPEC_FAIL_OUT_OF_VERSIONS);
goto fail;
}
cache1->module_keys_version = globals_version;
Expand Down