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Optimize SplObjectStorage native read/write/isset dimension handlers #7695

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13f46bf
Optimize SplObjectStorage native read/write/has/unset dimension handlers
TysonAndre Nov 26, 2021
9f69bf3
Check for ref in SplObjectStorage->__unserialize, check for ref.
TysonAndre Nov 29, 2021
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179 changes: 164 additions & 15 deletions ext/spl/spl_observer.c
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Original file line number Diff line number Diff line change
Expand Up @@ -44,10 +44,17 @@ PHPAPI zend_class_entry *spl_ce_MultipleIterator;

PHPAPI zend_object_handlers spl_handler_SplObjectStorage;

/* Bit flags for marking internal functionality overridden by SplObjectStorage subclasses. */
#define SOS_OVERRIDDEN_READ_DIMENSION 1
#define SOS_OVERRIDDEN_WRITE_DIMENSION 2
#define SOS_OVERRIDDEN_UNSET_DIMENSION 4

typedef struct _spl_SplObjectStorage { /* {{{ */
HashTable storage;
zend_long index;
HashPosition pos;
/* In SplObjectStorage, flags is a hidden implementation detail to optimize ArrayAccess handlers.
* In MultipleIterator on a different class hierarchy, flags is a user settable value controlling iteration behavior. */
zend_long flags;
zend_function *fptr_get_hash;
zend_object std;
Expand Down Expand Up @@ -76,7 +83,7 @@ void spl_SplObjectStorage_free_storage(zend_object *object) /* {{{ */
} /* }}} */

static int spl_object_storage_get_hash(zend_hash_key *key, spl_SplObjectStorage *intern, zend_object *obj) {
if (intern->fptr_get_hash) {
if (UNEXPECTED(intern->fptr_get_hash)) {
zval param;
zval rv;
ZVAL_OBJ(&param, obj);
Expand Down Expand Up @@ -125,8 +132,55 @@ static spl_SplObjectStorageElement* spl_object_storage_get(spl_SplObjectStorage
}
} /* }}} */

static spl_SplObjectStorageElement *spl_object_storage_create_element(zend_object *obj, zval *inf) /* {{{ */
{
spl_SplObjectStorageElement *pelement = emalloc(sizeof(spl_SplObjectStorageElement));
pelement->obj = obj;
GC_ADDREF(obj);
if (inf) {
ZVAL_COPY(&pelement->inf, inf);
} else {
ZVAL_NULL(&pelement->inf);
}
return pelement;
} /* }}} */

/* A faster version of spl_object_storage_attach used when neither SplObjectStorage->getHash nor SplObjectStorage->offsetSet is overridden. */
static spl_SplObjectStorageElement *spl_object_storage_attach_handle(spl_SplObjectStorage *intern, zend_object *obj, zval *inf) /* {{{ */
{
uint32_t handle = obj->handle;
zval *entry_zv = zend_hash_index_lookup(&intern->storage, handle);
spl_SplObjectStorageElement *pelement;
ZEND_ASSERT(!(intern->flags & SOS_OVERRIDDEN_WRITE_DIMENSION));

if (Z_TYPE_P(entry_zv) != IS_NULL) {
zval zv_inf;
ZEND_ASSERT(Z_TYPE_P(entry_zv) == IS_PTR);
pelement = Z_PTR_P(entry_zv);
ZVAL_COPY_VALUE(&zv_inf, &pelement->inf);
ZEND_ASSERT(Z_TYPE(zv_inf) != IS_REFERENCE);
if (inf) {
ZVAL_COPY(&pelement->inf, inf);
} else {
ZVAL_NULL(&pelement->inf);
}
/* Call the old value's destructor last, in case it moves the entry */
zval_ptr_dtor(&zv_inf);
return pelement;
}

pelement = spl_object_storage_create_element(obj, inf);
ZVAL_PTR(entry_zv, pelement);
return pelement;
} /* }}} */

spl_SplObjectStorageElement *spl_object_storage_attach(spl_SplObjectStorage *intern, zend_object *obj, zval *inf) /* {{{ */
{
if (EXPECTED(!(intern->flags & SOS_OVERRIDDEN_WRITE_DIMENSION))) {
return spl_object_storage_attach_handle(intern, obj, inf);
}
/* getHash or offsetSet is overridden. */

spl_SplObjectStorageElement *pelement, element;
zend_hash_key key;
if (spl_object_storage_get_hash(&key, intern, obj) == FAILURE) {
Expand All @@ -136,13 +190,17 @@ spl_SplObjectStorageElement *spl_object_storage_attach(spl_SplObjectStorage *int
pelement = spl_object_storage_get(intern, &key);

if (pelement) {
zval_ptr_dtor(&pelement->inf);
zval zv_inf;
ZVAL_COPY_VALUE(&zv_inf, &pelement->inf);
ZEND_ASSERT(Z_TYPE(zv_inf) != IS_REFERENCE);
if (inf) {
ZVAL_COPY(&pelement->inf, inf);
} else {
ZVAL_NULL(&pelement->inf);
}
spl_object_storage_free_hash(intern, &key);
/* Call the old value's destructor last, in case it moves the entry */
zval_ptr_dtor(&zv_inf);
return pelement;
}

Expand All @@ -164,6 +222,9 @@ spl_SplObjectStorageElement *spl_object_storage_attach(spl_SplObjectStorage *int

static int spl_object_storage_detach(spl_SplObjectStorage *intern, zend_object *obj) /* {{{ */
{
if (EXPECTED(!(intern->flags & SOS_OVERRIDDEN_UNSET_DIMENSION))) {
return zend_hash_index_del(&intern->storage, obj->handle);
}
int ret = FAILURE;
zend_hash_key key;
if (spl_object_storage_get_hash(&key, intern, obj) == FAILURE) {
Expand All @@ -189,6 +250,9 @@ void spl_object_storage_addall(spl_SplObjectStorage *intern, spl_SplObjectStorag
intern->index = 0;
} /* }}} */

#define SPL_OBJECT_STORAGE_CLASS_HAS_OVERRIDE(class_type, zstr_method) \
(((zend_function *)zend_hash_find_ptr(&(class_type)->function_table, ZSTR_KNOWN(zstr_method)))->common.scope != spl_ce_SplObjectStorage)

static zend_object *spl_object_storage_new_ex(zend_class_entry *class_type, zend_object *orig) /* {{{ */
{
spl_SplObjectStorage *intern;
Expand All @@ -207,10 +271,27 @@ static zend_object *spl_object_storage_new_ex(zend_class_entry *class_type, zend

while (parent) {
if (parent == spl_ce_SplObjectStorage) {
/* Possible optimization: Cache these results with a map from class entry to IS_NULL/IS_PTR.
* Or maybe just a single item with the result for the most recently loaded subclass. */
if (class_type != spl_ce_SplObjectStorage) {
intern->fptr_get_hash = zend_hash_str_find_ptr(&class_type->function_table, "gethash", sizeof("gethash") - 1);
if (intern->fptr_get_hash->common.scope == spl_ce_SplObjectStorage) {
intern->fptr_get_hash = NULL;
zend_function *get_hash = zend_hash_str_find_ptr(&class_type->function_table, "gethash", sizeof("gethash") - 1);
if (get_hash->common.scope != spl_ce_SplObjectStorage) {
intern->fptr_get_hash = get_hash;
}
if (intern->fptr_get_hash != NULL ||
SPL_OBJECT_STORAGE_CLASS_HAS_OVERRIDE(class_type, ZEND_STR_OFFSETGET) ||
SPL_OBJECT_STORAGE_CLASS_HAS_OVERRIDE(class_type, ZEND_STR_OFFSETEXISTS)) {
intern->flags |= SOS_OVERRIDDEN_READ_DIMENSION;
}

if (intern->fptr_get_hash != NULL ||
SPL_OBJECT_STORAGE_CLASS_HAS_OVERRIDE(class_type, ZEND_STR_OFFSETSET)) {
intern->flags |= SOS_OVERRIDDEN_WRITE_DIMENSION;
}

if (intern->fptr_get_hash != NULL ||
SPL_OBJECT_STORAGE_CLASS_HAS_OVERRIDE(class_type, ZEND_STR_OFFSETUNSET)) {
intern->flags |= SOS_OVERRIDDEN_UNSET_DIMENSION;
}
}
break;
Expand Down Expand Up @@ -328,20 +409,21 @@ static zend_object *spl_SplObjectStorage_new(zend_class_entry *class_type)
}
/* }}} */

int spl_object_storage_contains(spl_SplObjectStorage *intern, zend_object *obj) /* {{{ */
/* Returns true if the SplObjectStorage contains an entry for getHash(obj), even if the corresponding value is null. */
bool spl_object_storage_contains(spl_SplObjectStorage *intern, zend_object *obj) /* {{{ */
{
int found;
if (EXPECTED(!intern->fptr_get_hash)) {
return zend_hash_index_find(&intern->storage, obj->handle) != NULL;
}
zend_hash_key key;
if (spl_object_storage_get_hash(&key, intern, obj) == FAILURE) {
return 0;
return true;
}

if (key.key) {
found = zend_hash_exists(&intern->storage, key.key);
} else {
found = zend_hash_index_exists(&intern->storage, key.h);
}
spl_object_storage_free_hash(intern, &key);
ZEND_ASSERT(key.key);
bool found = zend_hash_exists(&intern->storage, key.key);
zend_string_release_ex(key.key, 0);
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@morrisonlevi morrisonlevi Nov 29, 2021 •
edited
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Just in case any other reviewers wonder: the spl_object_storage_free_hash goes away because we know that we have key.key, so we can release the string directly.


return found;
} /* }}} */

Expand All @@ -361,6 +443,69 @@ PHP_METHOD(SplObjectStorage, attach)
spl_object_storage_attach(intern, obj, inf);
} /* }}} */

static int spl_object_storage_has_dimension(zend_object *object, zval *offset, int check_empty)
{
spl_SplObjectStorage *intern = spl_object_storage_from_obj(object);
if (UNEXPECTED(offset == NULL || Z_TYPE_P(offset) != IS_OBJECT || (intern->flags & SOS_OVERRIDDEN_READ_DIMENSION))) {
/* Can't optimize empty()/isset() check if getHash, offsetExists, or offsetGet is overridden */
return zend_std_has_dimension(object, offset, check_empty);
}
spl_SplObjectStorageElement *element = zend_hash_index_find_ptr(&intern->storage, Z_OBJ_HANDLE_P(offset));
if (!element) {
return 0;
}

if (check_empty) {
return i_zend_is_true(&element->inf);
}
/* NOTE: SplObjectStorage->offsetExists() is an alias of SplObjectStorage->contains(), so this returns true even if the value is null. */
return 1;
}

static zval *spl_object_storage_read_dimension(zend_object *object, zval *offset, int type, zval *rv)
{
spl_SplObjectStorage *intern = spl_object_storage_from_obj(object);
if (UNEXPECTED(offset == NULL || Z_TYPE_P(offset) != IS_OBJECT || (intern->flags & SOS_OVERRIDDEN_READ_DIMENSION))) {
/* Can't optimize it if getHash, offsetExists, or offsetGet is overridden */
return zend_std_read_dimension(object, offset, type, rv);
}
spl_SplObjectStorageElement *element = zend_hash_index_find_ptr(&intern->storage, Z_OBJ_HANDLE_P(offset));

if (!element) {
if (type == BP_VAR_IS) {
return &EG(uninitialized_zval);
}
zend_throw_exception_ex(spl_ce_UnexpectedValueException, 0, "Object not found");
return NULL;
} else {
/* This deliberately returns a non-reference, even for BP_VAR_W and BP_VAR_RW, to behave the same way as SplObjectStorage did when using the default zend_std_read_dimension behavior.
* i.e. This prevents taking a reference to an entry of SplObjectStorage because offsetGet would return a non-reference. */
ZEND_ASSERT(Z_TYPE(element->inf) != IS_REFERENCE);
ZVAL_COPY(rv, &element->inf);
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I'm not sure why element of the storage can't be a reference. May be this correct. May be it's safer to use ZVAL_COPY_DEREF()

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I don't believe it can be a reference - it's because you can't create a reference with offsetSet, offsetGet, and offsetExists in the zend_std_read_dimension code.

In many places it was using ZVAL_COPY.

Attempting to do so resulted in Notice: Indirect modification of overloaded element of SplObjectStorage has no effect in php shell code on line 1 before/after this change

Separately, I think there might be a bug in the __unserialize implementation when a value is a reference
The handlers I've added are based on zend_std_read_dimension and zend_std_write_dimension. #7695 (comment)

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@TysonAndre TysonAndre Nov 29, 2021 •
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php > echo PHP_VERSION;
7.4.19-dev
php > $s = new SplObjectStorage();
php > $y = 1;
php > $x = [new stdClass(), &$y];
php > var_dump($s->__unserialize([$x, []]));
NULL
php > var_dump($s);
object(SplObjectStorage)#1 (1) {
  ["storage":"SplObjectStorage":private]=>
  array(1) {
    ["000000001f5767c4000000002919f006"]=>
    array(2) {
      ["obj"]=>
      object(stdClass)#2 (0) {
      }
      ["inf"]=>
      &int(1)
    }
  }
}

The entry for inf is a reference

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Figuring out what to do for the legacy Serializable::unserialize interface is a different change - if something was serialized that referred to that index, subsequent objects being unserialized could refer back to it.

The only way I can think of to add a reference to a value of an entry of https://www.php.net/splobjectstorage is through manually constructed serializable data, so it's probably fine to convert references to non-references in __unserialize in this case

return rv;
}
}

static void spl_object_storage_write_dimension(zend_object *object, zval *offset, zval *inf)
{
spl_SplObjectStorage *intern = spl_object_storage_from_obj(object);
if (UNEXPECTED(offset == NULL || Z_TYPE_P(offset) != IS_OBJECT || (intern->flags & SOS_OVERRIDDEN_WRITE_DIMENSION))) {
zend_std_write_dimension(object, offset, inf);
return;
}
spl_object_storage_attach_handle(intern, Z_OBJ_P(offset), inf);
}

static void spl_object_storage_unset_dimension(zend_object *object, zval *offset)
{
spl_SplObjectStorage *intern = spl_object_storage_from_obj(object);
if (UNEXPECTED(Z_TYPE_P(offset) != IS_OBJECT || (intern->flags & SOS_OVERRIDDEN_UNSET_DIMENSION))) {
zend_std_unset_dimension(object, offset);
return;
}
zend_hash_index_del(&intern->storage, Z_OBJ_HANDLE_P(offset));
}

/* {{{ Detaches an object from the storage */
PHP_METHOD(SplObjectStorage, detach)
{
Expand Down Expand Up @@ -411,7 +556,7 @@ PHP_METHOD(SplObjectStorage, offsetGet)
if (!element) {
zend_throw_exception_ex(spl_ce_UnexpectedValueException, 0, "Object not found");
} else {
RETURN_COPY_DEREF(&element->inf);
RETURN_COPY(&element->inf);
}
} /* }}} */

Expand Down Expand Up @@ -1201,6 +1346,10 @@ PHP_MINIT_FUNCTION(spl_observer)
spl_handler_SplObjectStorage.clone_obj = spl_object_storage_clone;
spl_handler_SplObjectStorage.get_gc = spl_object_storage_get_gc;
spl_handler_SplObjectStorage.free_obj = spl_SplObjectStorage_free_storage;
spl_handler_SplObjectStorage.read_dimension = spl_object_storage_read_dimension;
spl_handler_SplObjectStorage.write_dimension = spl_object_storage_write_dimension;
spl_handler_SplObjectStorage.has_dimension = spl_object_storage_has_dimension;
spl_handler_SplObjectStorage.unset_dimension = spl_object_storage_unset_dimension;

spl_ce_MultipleIterator = register_class_MultipleIterator(zend_ce_iterator);
spl_ce_MultipleIterator->create_object = spl_SplObjectStorage_new;
Expand Down
91 changes: 91 additions & 0 deletions ext/spl/tests/SplObjectStorage_coalesce.phpt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,91 @@
--TEST--
SplObjectStorage magic operators
--FILE--
<?php
$i = 'dynamic';
$v = $i . '_';
$s = new SplObjectStorage();
$o1 = new Stdclass;
$o2 = new Stdclass;
var_dump($s[$o1] ?? 'default');
var_dump($s[$o1] ??= $i);
var_dump($s[$o1] ??= null);
var_dump($s[$o1] ??= false);
var_dump($s[$o1] ?? $i);
var_dump(isset($s[$o1]));
var_dump(empty($s[$o1]));
echo "o2\n";
var_dump(isset($s[$o2]));
var_dump(empty($s[$o2]));
$s[$o2] = null;
var_dump($s[$o2] ?? new stdClass());
echo "check isset/empty/contains for null. offsetExists returns true as long as the entry is there.\n";
var_dump(isset($s[$o2]));
var_dump(empty($s[$o2]));
var_dump($s->contains($o2));
echo "check isset/empty/contains for false.\n";
$s[$o2] = false;
var_dump(isset($s[$o2]));
var_dump(empty($s[$o2]));
var_dump($s->contains($o2));
try {
$s['invalid'] = 123;
} catch (Error $e) {
printf("%s: %s\n", $e::class, $e->getMessage());
}
try {
var_dump(isset($s['invalid']));
} catch (Error $e) {
printf("%s: %s\n", $e::class, $e->getMessage());
}
$a = &$s[$o1];

var_dump($s);

?>
--EXPECTF--
string(7) "default"
string(7) "dynamic"
string(7) "dynamic"
string(7) "dynamic"
string(7) "dynamic"
bool(true)
bool(false)
o2
bool(false)
bool(true)
object(stdClass)#4 (0) {
}
check isset/empty/contains for null. offsetExists returns true as long as the entry is there.
bool(true)
bool(true)
bool(true)
check isset/empty/contains for false.
bool(true)
bool(true)
bool(true)
TypeError: SplObjectStorage::offsetSet(): Argument #1 ($object) must be of type object, string given
TypeError: SplObjectStorage::offsetExists(): Argument #1 ($object) must be of type object, string given

Notice: Indirect modification of overloaded element of SplObjectStorage has no effect in %s on line 38
object(SplObjectStorage)#1 (1) {
["storage":"SplObjectStorage":private]=>
array(2) {
[0]=>
array(2) {
["obj"]=>
object(stdClass)#2 (0) {
}
["inf"]=>
string(7) "dynamic"
}
[1]=>
array(2) {
["obj"]=>
object(stdClass)#3 (0) {
}
["inf"]=>
bool(false)
}
}
}
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