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bpo-42927: Inline cache for attributes defined with '__slots__' (#24216)
This commit is contained in:
Guido van Rossum
GitHub
parent
ba7a99ddb5
commit
5c5a938573
2 changed files with 120 additions and 66 deletions
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@ -0,0 +1,2 @@
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The inline cache for ``LOAD_ATTR`` now also optimizes access to attributes defined by ``__slots__``.
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This makes reading such attribute up to 30% faster.
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184
Python/ceval.c
184
Python/ceval.c
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@ -29,6 +29,7 @@
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#include "opcode.h"
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#include "pydtrace.h"
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#include "setobject.h"
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#include "structmember.h" // struct PyMemberDef, T_OFFSET_EX
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#include <ctype.h>
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@ -3169,106 +3170,157 @@ main_loop:
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if (co_opcache != NULL && PyType_HasFeature(type, Py_TPFLAGS_VALID_VERSION_TAG))
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{
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if (co_opcache->optimized > 0) {
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/* Fast path -- cache hit makes LOAD_ATTR ~30% faster */
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// Fast path -- cache hit makes LOAD_ATTR ~30% faster.
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la = &co_opcache->u.la;
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if (la->type == type && la->tp_version_tag == type->tp_version_tag)
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{
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assert(type->tp_dict != NULL);
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assert(type->tp_dictoffset > 0);
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dictptr = (PyObject **) ((char *)owner + type->tp_dictoffset);
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dict = *dictptr;
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if (dict != NULL && PyDict_CheckExact(dict)) {
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Py_ssize_t hint = la->hint;
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Py_INCREF(dict);
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res = NULL;
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la->hint = _PyDict_GetItemHint((PyDictObject*)dict, name, hint, &res);
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// Hint >= 0 is a dict index; hint == -1 is a dict miss.
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// Hint < -1 is an inverted slot offset: offset is strictly > 0,
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// so ~offset is strictly < -1 (assuming 2's complement).
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if (la->hint < -1) {
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// Even faster path -- slot hint.
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Py_ssize_t offset = ~la->hint;
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// fprintf(stderr, "Using hint for offset %zd\n", offset);
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char *addr = (char *)owner + offset;
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res = *(PyObject **)addr;
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if (res != NULL) {
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if (la->hint == hint && hint >= 0) {
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/* Our hint has helped -- cache hit. */
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OPCACHE_STAT_ATTR_HIT();
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} else {
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/* The hint we provided didn't work.
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Maybe next time? */
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OPCACHE_MAYBE_DEOPT_LOAD_ATTR();
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}
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Py_INCREF(res);
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SET_TOP(res);
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Py_DECREF(owner);
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Py_DECREF(dict);
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DISPATCH();
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} else {
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// This attribute can be missing sometimes -- we
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// don't want to optimize this lookup.
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OPCACHE_DEOPT_LOAD_ATTR();
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Py_DECREF(dict);
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}
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// Else slot is NULL. Fall through to slow path to raise AttributeError(name).
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// Don't DEOPT, since the slot is still there.
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} else {
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// There is no dict, or __dict__ doesn't satisfy PyDict_CheckExact
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OPCACHE_DEOPT_LOAD_ATTR();
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// Fast path for dict.
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assert(type->tp_dict != NULL);
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assert(type->tp_dictoffset > 0);
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dictptr = (PyObject **) ((char *)owner + type->tp_dictoffset);
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dict = *dictptr;
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if (dict != NULL && PyDict_CheckExact(dict)) {
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Py_ssize_t hint = la->hint;
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Py_INCREF(dict);
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res = NULL;
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la->hint = _PyDict_GetItemHint((PyDictObject*)dict, name, hint, &res);
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if (res != NULL) {
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if (la->hint == hint && hint >= 0) {
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// Our hint has helped -- cache hit.
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OPCACHE_STAT_ATTR_HIT();
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} else {
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// The hint we provided didn't work.
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// Maybe next time?
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OPCACHE_MAYBE_DEOPT_LOAD_ATTR();
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}
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Py_INCREF(res);
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SET_TOP(res);
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Py_DECREF(owner);
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Py_DECREF(dict);
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DISPATCH();
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} else {
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// This attribute can be missing sometimes;
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// we don't want to optimize this lookup.
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OPCACHE_DEOPT_LOAD_ATTR();
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Py_DECREF(dict);
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}
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} else {
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// There is no dict, or __dict__ doesn't satisfy PyDict_CheckExact.
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OPCACHE_DEOPT_LOAD_ATTR();
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}
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}
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} else {
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// The type of the object has either been updated,
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// or is different. Maybe it will stabilize?
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OPCACHE_MAYBE_DEOPT_LOAD_ATTR();
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}
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OPCACHE_STAT_ATTR_MISS();
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}
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if (co_opcache != NULL && /* co_opcache can be NULL after a DEOPT() call. */
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if (co_opcache != NULL && // co_opcache can be NULL after a DEOPT() call.
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type->tp_getattro == PyObject_GenericGetAttr)
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{
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Py_ssize_t ret;
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if (type->tp_dictoffset > 0) {
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if (type->tp_dict == NULL) {
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if (PyType_Ready(type) < 0) {
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Py_DECREF(owner);
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SET_TOP(NULL);
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goto error;
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}
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if (type->tp_dict == NULL) {
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if (PyType_Ready(type) < 0) {
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Py_DECREF(owner);
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SET_TOP(NULL);
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goto error;
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}
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if (_PyType_Lookup(type, name) == NULL) {
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dictptr = (PyObject **) ((char *)owner + type->tp_dictoffset);
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dict = *dictptr;
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}
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PyObject *descr = _PyType_Lookup(type, name);
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if (descr != NULL) {
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// We found an attribute with a data-like descriptor.
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PyTypeObject *dtype = Py_TYPE(descr);
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if (dtype == &PyMemberDescr_Type) { // It's a slot
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PyMemberDescrObject *member = (PyMemberDescrObject *)descr;
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struct PyMemberDef *dmem = member->d_member;
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if (dmem->type == T_OBJECT_EX) {
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Py_ssize_t offset = dmem->offset;
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assert(offset > 0); // 0 would be confused with dict hint == -1 (miss).
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if (dict != NULL && PyDict_CheckExact(dict)) {
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Py_INCREF(dict);
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res = NULL;
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ret = _PyDict_GetItemHint((PyDictObject*)dict, name, -1, &res);
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if (co_opcache->optimized == 0) {
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// First time we optimize this opcode.
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OPCACHE_STAT_ATTR_OPT();
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co_opcache->optimized = OPCODE_CACHE_MAX_TRIES;
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// fprintf(stderr, "Setting hint for %s, offset %zd\n", dmem->name, offset);
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}
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la = &co_opcache->u.la;
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la->type = type;
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la->tp_version_tag = type->tp_version_tag;
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la->hint = ~offset;
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char *addr = (char *)owner + offset;
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res = *(PyObject **)addr;
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if (res != NULL) {
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Py_INCREF(res);
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Py_DECREF(dict);
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Py_DECREF(owner);
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SET_TOP(res);
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if (co_opcache->optimized == 0) {
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// First time we optimize this opcode. */
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OPCACHE_STAT_ATTR_OPT();
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co_opcache->optimized = OPCODE_CACHE_MAX_TRIES;
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}
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la = &co_opcache->u.la;
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la->type = type;
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la->tp_version_tag = type->tp_version_tag;
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la->hint = ret;
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DISPATCH();
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}
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Py_DECREF(dict);
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} else {
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// There is no dict, or __dict__ doesn't satisfy PyDict_CheckExact
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OPCACHE_DEOPT_LOAD_ATTR();
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// Else slot is NULL. Fall through to slow path to raise AttributeError(name).
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}
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// Else it's a slot of a different type. We don't handle those.
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}
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// Else it's some other kind of descriptor that we don't handle.
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OPCACHE_DEOPT_LOAD_ATTR();
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} else if (type->tp_dictoffset > 0) {
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// We found an instance with a __dict__.
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dictptr = (PyObject **) ((char *)owner + type->tp_dictoffset);
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dict = *dictptr;
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if (dict != NULL && PyDict_CheckExact(dict)) {
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Py_INCREF(dict);
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res = NULL;
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Py_ssize_t hint = _PyDict_GetItemHint((PyDictObject*)dict, name, -1, &res);
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if (res != NULL) {
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Py_INCREF(res);
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Py_DECREF(dict);
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Py_DECREF(owner);
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SET_TOP(res);
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if (co_opcache->optimized == 0) {
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// First time we optimize this opcode.
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OPCACHE_STAT_ATTR_OPT();
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co_opcache->optimized = OPCODE_CACHE_MAX_TRIES;
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}
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la = &co_opcache->u.la;
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la->type = type;
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la->tp_version_tag = type->tp_version_tag;
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la->hint = hint;
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DISPATCH();
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}
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Py_DECREF(dict);
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} else {
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// We failed to find an attribute without a data-like descriptor
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// There is no dict, or __dict__ doesn't satisfy PyDict_CheckExact.
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OPCACHE_DEOPT_LOAD_ATTR();
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}
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} else {
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// The object's class does not have a tp_dictoffset we can use
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// The object's class does not have a tp_dictoffset we can use.
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OPCACHE_DEOPT_LOAD_ATTR();
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}
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} else if (type->tp_getattro != PyObject_GenericGetAttr) {
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@ -3276,7 +3328,7 @@ main_loop:
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}
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}
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/* slow path */
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// Slow path.
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res = PyObject_GetAttr(owner, name);
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Py_DECREF(owner);
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SET_TOP(res);
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