Optimize SplObjectStorage native read/write/has/unset dimension handlers

This makes reading/writing with `$splObjectStorage[$offset]` shorthand twice as
fast as it was previously, and a bit faster than offsetGet/offsetSet instead of
(previously) much slower.

Call destructor after overriding old SplObjectStorage entry.
Previously, it was called before, which was possibly unsafe
if the destructor had side effects.

Add tests.

Related to phpGH-7690

Author: TysonAndre

ext/spl/spl_observer.c

@@ -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;
@@ -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);
@@ -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) {
@@ -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;
 	}
 
@@ -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) {
@@ -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;
@@ -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;
@@ -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);
+
 	return found;
 } /* }}} */
 
@@ -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);
+		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)
 {
@@ -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);
 	}
 } /* }}} */
 
@@ -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;

ext/spl/tests/SplObjectStorage_coalesce.phpt

@@ -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)
+    }
+  }
+}