Use Identifier by value and don't new them anymore

Change-Id: Ib25c08027013217657beb2675dafa9a8c85cbaf9
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

14 files changed, 108 insertions, 103 deletions

diff --git a/src/qml/jsruntime/qv4context.cpp b/src/qml/jsruntime/qv4context.cpp
index bd2e0faebf..c81af767fa 100644
--- a/src/qml/jsruntime/qv4context.cpp
+++ b/src/qml/jsruntime/qv4context.cpp
@@ -175,7 +175,7 @@ void ExecutionContext::createMutableBinding(String *name, bool deletable)
 bool ExecutionContext::deleteProperty(String *name)
 {
     name->makeIdentifier();
-    Identifier *id = name->identifier();
+    Identifier id = name->identifier();
 
     Heap::ExecutionContext *ctx = d();
     for (; ctx; ctx = ctx->outer) {
@@ -211,7 +211,7 @@ bool ExecutionContext::deleteProperty(String *name)
 ExecutionContext::Error ExecutionContext::setProperty(String *name, const Value &value)
 {
     name->makeIdentifier();
-    Identifier *id = name->identifier();
+    Identifier id = name->identifier();
 
     QV4::ExecutionEngine *v4 = engine();
     Heap::ExecutionContext *ctx = d();
@@ -274,7 +274,7 @@ ReturnedValue ExecutionContext::getProperty(String *name)
         case Heap::ExecutionContext::Type_BlockContext:
         case Heap::ExecutionContext::Type_CallContext: {
             Heap::CallContext *c = static_cast<Heap::CallContext *>(ctx);
-            Identifier *id = name->identifier();
+            Identifier id = name->identifier();
 
             uint index = c->internalClass->find(id);
             if (index < UINT_MAX)
@@ -311,7 +311,7 @@ ReturnedValue ExecutionContext::getPropertyAndBase(String *name, Value *base)
         case Heap::ExecutionContext::Type_CallContext: {
             Heap::CallContext *c = static_cast<Heap::CallContext *>(ctx);
             name->makeIdentifier();
-            Identifier *id = name->identifier();
+            Identifier id = name->identifier();
 
             uint index = c->internalClass->find(id);
             if (index < UINT_MAX)
diff --git a/src/qml/jsruntime/qv4engine_p.h b/src/qml/jsruntime/qv4engine_p.h
index 8e5108b399..69c62261d2 100644
--- a/src/qml/jsruntime/qv4engine_p.h
+++ b/src/qml/jsruntime/qv4engine_p.h
@@ -158,9 +158,9 @@ public:
     QJSEngine *publicEngine;
 
 private:
-    int stringOrSymbolId = 0;
+    quintptr currentIdentifier = 0;
 public:
-    int nextStringOrSymbolId() { return ++stringOrSymbolId; }
+    Identifier nextIdentifier() { return Identifier{ ++currentIdentifier }; }
 
     enum JSObjects {
         RootContext,
diff --git a/src/qml/jsruntime/qv4identifier.cpp b/src/qml/jsruntime/qv4identifier.cpp
index 69d44f89c4..0bde74b718 100644
--- a/src/qml/jsruntime/qv4identifier.cpp
+++ b/src/qml/jsruntime/qv4identifier.cpp
@@ -93,7 +93,7 @@ void IdentifierHash::detach()
 }
 
 
-IdentifierHashEntry *IdentifierHash::addEntry(const Identifier *identifier)
+IdentifierHashEntry *IdentifierHash::addEntry(Identifier identifier)
 {
     // fill up to max 50%
     bool grow = (d->alloc <= d->size*2);
@@ -107,8 +107,8 @@ IdentifierHashEntry *IdentifierHash::addEntry(const Identifier *identifier)
             const IdentifierHashEntry &e = d->entries[i];
             if (!e.identifier)
                 continue;
-            uint idx = e.identifier->id % newAlloc;
-            while (newEntries[idx].identifier) {
+            uint idx = e.identifier.id % newAlloc;
+            while (newEntries[idx].identifier.isValid()) {
                 ++idx;
                 idx %= newAlloc;
             }
@@ -119,8 +119,8 @@ IdentifierHashEntry *IdentifierHash::addEntry(const Identifier *identifier)
         d->alloc = newAlloc;
     }
 
-    uint idx = identifier->id % d->alloc;
-    while (d->entries[idx].identifier) {
+    uint idx = identifier.id % d->alloc;
+    while (d->entries[idx].identifier.isValid()) {
         Q_ASSERT(d->entries[idx].identifier != identifier);
         ++idx;
         idx %= d->alloc;
@@ -130,13 +130,13 @@ IdentifierHashEntry *IdentifierHash::addEntry(const Identifier *identifier)
     return d->entries + idx;
 }
 
-const IdentifierHashEntry *IdentifierHash::lookup(const Identifier *identifier) const
+const IdentifierHashEntry *IdentifierHash::lookup(Identifier identifier) const
 {
     if (!d)
         return nullptr;
     Q_ASSERT(d->entries);
 
-    uint idx = identifier->id % d->alloc;
+    uint idx = identifier.id % d->alloc;
     while (1) {
         if (!d->entries[idx].identifier)
             return nullptr;
@@ -152,7 +152,7 @@ const IdentifierHashEntry *IdentifierHash::lookup(const QString &str) const
     if (!d)
         return nullptr;
 
-    Identifier *id = d->identifierTable->identifier(str);
+    Identifier id = d->identifierTable->identifier(str);
     return lookup(id);
 }
 
@@ -160,18 +160,18 @@ const IdentifierHashEntry *IdentifierHash::lookup(String *str) const
 {
     if (!d)
         return nullptr;
-    if (str->d()->identifier)
+    if (str->d()->identifier.isValid())
         return lookup(str->d()->identifier);
     return lookup(str->toQString());
 }
 
-const Identifier *IdentifierHash::toIdentifier(const QString &str) const
+const Identifier IdentifierHash::toIdentifier(const QString &str) const
 {
     Q_ASSERT(d);
     return d->identifierTable->identifier(str);
 }
 
-const Identifier *IdentifierHash::toIdentifier(Heap::String *str) const
+const Identifier IdentifierHash::toIdentifier(Heap::String *str) const
 {
     Q_ASSERT(d);
     return d->identifierTable->identifier(str);
@@ -182,8 +182,8 @@ QString QV4::IdentifierHash::findId(int value) const
     IdentifierHashEntry *e = d->entries;
     IdentifierHashEntry *end = e + d->alloc;
     while (e < end) {
-        if (e->identifier && e->value == value)
-            return d->identifierTable->stringFromIdentifier(e->identifier)->toQString();
+        if (e->identifier.isValid() && e->value == value)
+            return d->identifierTable->stringForId(e->identifier)->toQString();
         ++e;
     }
     return QString();
diff --git a/src/qml/jsruntime/qv4identifier_p.h b/src/qml/jsruntime/qv4identifier_p.h
index f3935950c8..660cc2db05 100644
--- a/src/qml/jsruntime/qv4identifier_p.h
+++ b/src/qml/jsruntime/qv4identifier_p.h
@@ -66,12 +66,19 @@ struct ExecutionEngine;
 
 struct Identifier
 {
-    uint id;
+    quintptr id;
+
+    static Identifier invalid() { return Identifier{0}; }
+    bool isValid() const { return id != 0; }
+    bool operator !() const { return id == 0; }
+    bool operator ==(const Identifier &other) const { return id == other.id; }
+    bool operator !=(const Identifier &other) const { return id != other.id; }
+    bool operator <(const Identifier &other) const { return id < other.id; }
 };
 
 
 struct IdentifierHashEntry {
-    const Identifier *identifier;
+    Identifier identifier;
     int value;
 };
 
@@ -116,12 +123,12 @@ struct IdentifierHash
     QString findId(int value) const;
 
 protected:
-    IdentifierHashEntry *addEntry(const Identifier *i);
-    const IdentifierHashEntry *lookup(const Identifier *identifier) const;
+    IdentifierHashEntry *addEntry(Identifier i);
+    const IdentifierHashEntry *lookup(Identifier identifier) const;
     const IdentifierHashEntry *lookup(const QString &str) const;
     const IdentifierHashEntry *lookup(String *str) const;
-    const Identifier *toIdentifier(const QString &str) const;
-    const Identifier *toIdentifier(Heap::String *str) const;
+    const Identifier toIdentifier(const QString &str) const;
+    const Identifier toIdentifier(Heap::String *str) const;
 };
 
 
diff --git a/src/qml/jsruntime/qv4identifiertable.cpp b/src/qml/jsruntime/qv4identifiertable.cpp
index cd5a7ebc3e..2cfdd81c87 100644
--- a/src/qml/jsruntime/qv4identifiertable.cpp
+++ b/src/qml/jsruntime/qv4identifiertable.cpp
@@ -67,9 +67,6 @@ IdentifierTable::IdentifierTable(ExecutionEngine *engine)
 
 IdentifierTable::~IdentifierTable()
 {
-    for (int i = 0; i < alloc; ++i)
-        if (entriesByHash[i])
-            delete entriesByHash[i]->identifier;
     free(entriesByHash);
     free(entriesById);
 }
@@ -81,8 +78,7 @@ void IdentifierTable::addEntry(Heap::String *str)
     if (str->subtype == Heap::String::StringType_ArrayIndex)
         return;
 
-    str->identifier = new Identifier;
-    str->identifier->id = engine->nextStringOrSymbolId();
+    str->identifier = engine->nextIdentifier();
 
     bool grow = (alloc <= size*2);
 
@@ -111,7 +107,7 @@ void IdentifierTable::addEntry(Heap::String *str)
             Heap::String *e = entriesById[i];
             if (!e)
                 continue;
-            uint idx = e->identifier->id % newAlloc;
+            uint idx = e->identifier.id % newAlloc;
             while (newEntries[idx]) {
                 ++idx;
                 idx %= newAlloc;
@@ -131,7 +127,7 @@ void IdentifierTable::addEntry(Heap::String *str)
     }
     entriesByHash[idx] = str;
 
-    idx = str->identifier->id % alloc;
+    idx = str->identifier.id % alloc;
     while (entriesById[idx]) {
         ++idx;
         idx %= alloc;
@@ -163,13 +159,13 @@ Heap::String *IdentifierTable::insertString(const QString &s)
 }
 
 
-Identifier *IdentifierTable::identifierImpl(const Heap::String *str)
+Identifier IdentifierTable::identifierImpl(const Heap::String *str)
 {
-    if (str->identifier)
+    if (str->identifier.isValid())
         return str->identifier;
     uint hash = str->hashValue();
     if (str->subtype == Heap::String::StringType_ArrayIndex)
-        return nullptr;
+        return Identifier::invalid();
 
     uint idx = hash % alloc;
     while (Heap::String *e = entriesByHash[idx]) {
@@ -185,12 +181,12 @@ Identifier *IdentifierTable::identifierImpl(const Heap::String *str)
     return str->identifier;
 }
 
-Heap::String *IdentifierTable::stringFromIdentifier(const Identifier *i) const
+Heap::String *IdentifierTable::stringForId(Identifier i) const
 {
     if (!i)
         return nullptr;
 
-    uint idx = i->id % alloc;
+    uint idx = i.id % alloc;
     while (1) {
         Heap::String *e = entriesById[idx];
         Q_ASSERT(e);
@@ -201,12 +197,12 @@ Heap::String *IdentifierTable::stringFromIdentifier(const Identifier *i) const
     }
 }
 
-Identifier *IdentifierTable::identifier(const QString &s)
+Identifier IdentifierTable::identifier(const QString &s)
 {
     return insertString(s)->identifier;
 }
 
-Identifier *IdentifierTable::identifier(const char *s, int len)
+Identifier IdentifierTable::identifier(const char *s, int len)
 {
     uint subtype;
     uint hash = String::createHashValue(s, len, &subtype);
diff --git a/src/qml/jsruntime/qv4identifiertable_p.h b/src/qml/jsruntime/qv4identifiertable_p.h
index 0c8de01f71..dce270e337 100644
--- a/src/qml/jsruntime/qv4identifiertable_p.h
+++ b/src/qml/jsruntime/qv4identifiertable_p.h
@@ -78,21 +78,21 @@ public:
 
     Heap::String *insertString(const QString &s);
 
-    Identifier *identifier(const Heap::String *str) {
-        if (str->identifier)
+    Identifier identifier(const Heap::String *str) {
+        if (str->identifier.isValid())
             return str->identifier;
         return identifierImpl(str);
     }
-    Identifier *identifier(const QV4::String *str) {
+    Identifier identifier(const QV4::String *str) {
         return identifier(str->d());
     }
 
-    Identifier *identifier(const QString &s);
-    Identifier *identifier(const char *s, int len);
+    Identifier identifier(const QString &s);
+    Identifier identifier(const char *s, int len);
 
-    Identifier *identifierImpl(const Heap::String *str);
+    Identifier identifierImpl(const Heap::String *str);
 
-    Q_QML_PRIVATE_EXPORT Heap::String *stringFromIdentifier(const Identifier *i) const;
+    Q_QML_PRIVATE_EXPORT Heap::String *stringForId(Identifier i) const;
 
     void mark(MarkStack *markStack) {
         for (int i = 0; i < alloc; ++i) {
diff --git a/src/qml/jsruntime/qv4internalclass.cpp b/src/qml/jsruntime/qv4internalclass.cpp
index 532d35962c..de3f6e0ee6 100644
--- a/src/qml/jsruntime/qv4internalclass.cpp
+++ b/src/qml/jsruntime/qv4internalclass.cpp
@@ -77,8 +77,8 @@ void PropertyHash::addEntry(const PropertyHash::Entry &entry, int classSize)
     if (classSize < d->size || grow)
         detach(grow, classSize);
 
-    uint idx = entry.identifier->id % d->alloc;
-    while (d->entries[idx].identifier) {
+    uint idx = entry.identifier.id % d->alloc;
+    while (d->entries[idx].identifier.isValid()) {
         ++idx;
         idx %= d->alloc;
     }
@@ -86,20 +86,20 @@ void PropertyHash::addEntry(const PropertyHash::Entry &entry, int classSize)
     ++d->size;
 }
 
-int PropertyHash::removeIdentifier(Identifier *identifier, int classSize)
+int PropertyHash::removeIdentifier(Identifier identifier, int classSize)
 {
     int val = -1;
     PropertyHashData *dd = new PropertyHashData(d->numBits);
     for (int i = 0; i < d->alloc; ++i) {
         const Entry &e = d->entries[i];
-        if (!e.identifier || e.index >= static_cast<unsigned>(classSize))
+        if (!e.identifier.isValid() || e.index >= static_cast<unsigned>(classSize))
             continue;
         if (e.identifier == identifier) {
             val = e.index;
             continue;
         }
-        uint idx = e.identifier->id % dd->alloc;
-        while (dd->entries[idx].identifier) {
+        uint idx = e.identifier.id % dd->alloc;
+        while (dd->entries[idx].identifier.isValid()) {
             ++idx;
             idx %= dd->alloc;
         }
@@ -124,8 +124,8 @@ void PropertyHash::detach(bool grow, int classSize)
         const Entry &e = d->entries[i];
         if (!e.identifier || e.index >= static_cast<unsigned>(classSize))
             continue;
-        uint idx = e.identifier->id % dd->alloc;
-        while (dd->entries[idx].identifier) {
+        uint idx = e.identifier.id % dd->alloc;
+        while (dd->entries[idx].identifier.isValid()) {
             ++idx;
             idx %= dd->alloc;
         }
@@ -143,7 +143,7 @@ void InternalClass::init(ExecutionEngine *engine)
 {
     Base::init();
     new (&propertyTable) PropertyHash();
-    new (&nameMap) SharedInternalClassData<Identifier *>();
+    new (&nameMap) SharedInternalClassData<Identifier>();
     new (&propertyData) SharedInternalClassData<PropertyAttributes>();
     new (&transitions) std::vector<Transition>();
 
@@ -168,7 +168,7 @@ void InternalClass::init(Heap::InternalClass *other)
     Base::init();
     Q_ASSERT(!other->isFrozen);
     new (&propertyTable) PropertyHash(other->propertyTable);
-    new (&nameMap) SharedInternalClassData<Identifier *>(other->nameMap);
+    new (&nameMap) SharedInternalClassData<Identifier>(other->nameMap);
     new (&propertyData) SharedInternalClassData<PropertyAttributes>(other->propertyData);
     new (&transitions) std::vector<Transition>();
 
@@ -197,7 +197,7 @@ void InternalClass::destroy()
         parent->removeChildEntry(this);
 
     propertyTable.~PropertyHash();
-    nameMap.~SharedInternalClassData<Identifier *>();
+    nameMap.~SharedInternalClassData<Identifier>();
     propertyData.~SharedInternalClassData<PropertyAttributes>();
     transitions.~vector<Transition>();
     engine = nullptr;
@@ -260,12 +260,12 @@ static void addDummyEntry(InternalClass *newClass, PropertyHash::Entry e)
 {
     // add a dummy entry, since we need two entries for accessors
     newClass->propertyTable.addEntry(e, newClass->size);
-    newClass->nameMap.add(newClass->size, nullptr);
+    newClass->nameMap.add(newClass->size, Identifier::invalid());
     newClass->propertyData.add(newClass->size, PropertyAttributes());
     ++newClass->size;
 }
 
-Heap::InternalClass *InternalClass::changeMember(Identifier *identifier, PropertyAttributes data, uint *index)
+Heap::InternalClass *InternalClass::changeMember(Identifier identifier, PropertyAttributes data, uint *index)
 {
     data.resolve();
     uint idx = find(identifier);
@@ -287,11 +287,11 @@ Heap::InternalClass *InternalClass::changeMember(Identifier *identifier, Propert
     if (data.isAccessor() != propertyData.at(idx).isAccessor()) {
         // this changes the layout of the class, so we need to rebuild the data
         newClass->propertyTable = PropertyHash();
-        newClass->nameMap = SharedInternalClassData<Identifier *>();
+        newClass->nameMap = SharedInternalClassData<Identifier>();
         newClass->propertyData = SharedInternalClassData<PropertyAttributes>();
         newClass->size = 0;
         for (uint i = 0; i < size; ++i) {
-            Identifier *identifier = nameMap.at(i);
+            Identifier identifier = nameMap.at(i);
             PropertyHash::Entry e = { identifier, newClass->size };
             if (!identifier)
                 e.identifier = nameMap.at(i - 1);
@@ -327,7 +327,7 @@ Heap::InternalClass *InternalClass::changePrototypeImpl(Heap::Object *proto)
     Q_ASSERT(prototype != proto);
     Q_ASSERT(!proto || proto->internalClass->isUsedAsProto);
 
-    Transition temp = { { nullptr }, nullptr, Transition::PrototypeChange };
+    Transition temp = { { Identifier::invalid() }, nullptr, Transition::PrototypeChange };
     temp.prototype = proto;
 
     Transition &t = lookupOrInsertTransition(temp);
@@ -347,7 +347,7 @@ Heap::InternalClass *InternalClass::changeVTableImpl(const VTable *vt)
 {
     Q_ASSERT(vtable != vt);
 
-    Transition temp = { { nullptr }, nullptr, Transition::VTableChange };
+    Transition temp = { { Identifier::invalid() }, nullptr, Transition::VTableChange };
     temp.vtable = vt;
 
     Transition &t = lookupOrInsertTransition(temp);
@@ -369,7 +369,7 @@ Heap::InternalClass *InternalClass::nonExtensible()
     if (!extensible)
         return this;
 
-    Transition temp = { { nullptr }, nullptr, Transition::NotExtensible};
+    Transition temp = { { Identifier::invalid() }, nullptr, Transition::NotExtensible};
     Transition &t = lookupOrInsertTransition(temp);
     if (t.lookup)
         return t.lookup;
@@ -405,7 +405,7 @@ Heap::InternalClass *InternalClass::addMember(QV4::String *string, PropertyAttri
     return addMember(string->identifier(), data, index);
 }
 
-Heap::InternalClass *InternalClass::addMember(Identifier *identifier, PropertyAttributes data, uint *index)
+Heap::InternalClass *InternalClass::addMember(Identifier identifier, PropertyAttributes data, uint *index)
 {
     data.resolve();
 
@@ -415,7 +415,7 @@ Heap::InternalClass *InternalClass::addMember(Identifier *identifier, PropertyAt
     return addMemberImpl(identifier, data, index);
 }
 
-Heap::InternalClass *InternalClass::addMemberImpl(Identifier *identifier, PropertyAttributes data, uint *index)
+Heap::InternalClass *InternalClass::addMemberImpl(Identifier identifier, PropertyAttributes data, uint *index)
 {
     Transition temp = { { identifier }, nullptr, (int)data.flags() };
     Transition &t = lookupOrInsertTransition(temp);
@@ -455,7 +455,7 @@ void InternalClass::removeChildEntry(InternalClass *child)
 
 }
 
-void InternalClass::removeMember(QV4::Object *object, Identifier *identifier)
+void InternalClass::removeMember(QV4::Object *object, Identifier identifier)
 {
     Heap::InternalClass *oldClass = object->internalClass();
     Q_ASSERT(oldClass->propertyTable.lookup(identifier) < oldClass->size);
@@ -468,7 +468,7 @@ void InternalClass::removeMember(QV4::Object *object, Identifier *identifier)
         Heap::InternalClass *newClass = oldClass->engine->newClass(oldClass);
         // simply make the entry inaccessible
         int idx = newClass->propertyTable.removeIdentifier(identifier, oldClass->size);
-        newClass->nameMap.set(idx, nullptr);
+        newClass->nameMap.set(idx, Identifier::invalid());
         newClass->propertyData.set(idx, PropertyAttributes());
         t.lookup = newClass;
         Q_ASSERT(t.lookup);
@@ -482,7 +482,7 @@ void InternalClass::removeMember(QV4::Object *object, Identifier *identifier)
 uint InternalClass::find(const QV4::String *string)
 {
     engine->identifierTable->identifier(string);
-    const Identifier *id = string->d()->identifier;
+    const Identifier id = string->d()->identifier;
 
     uint index = propertyTable.lookup(id);
     if (index < size)
@@ -512,7 +512,7 @@ Heap::InternalClass *InternalClass::sealed()
         return this;
     }
 
-    Transition temp = { { nullptr }, nullptr, InternalClassTransition::Sealed };
+    Transition temp = { { Identifier::invalid() }, nullptr, InternalClassTransition::Sealed };
     Transition &t = lookupOrInsertTransition(temp);
 
     if (t.lookup) {
@@ -558,7 +558,7 @@ Heap::InternalClass *InternalClass::frozen()
         return this;
     }
 
-    Transition temp = { { nullptr }, nullptr, InternalClassTransition::Frozen };
+    Transition temp = { { Identifier::invalid() }, nullptr, InternalClassTransition::Frozen };
     Transition &t = lookupOrInsertTransition(temp);
 
     if (t.lookup) {
@@ -606,7 +606,7 @@ Heap::InternalClass *InternalClass::asProtoClass()
     if (isUsedAsProto)
         return this;
 
-    Transition temp = { { nullptr }, nullptr, Transition::ProtoClass };
+    Transition temp = { { Identifier::invalid() }, nullptr, Transition::ProtoClass };
     Transition &t = lookupOrInsertTransition(temp);
     if (t.lookup)
         return t.lookup;
diff --git a/src/qml/jsruntime/qv4internalclass_p.h b/src/qml/jsruntime/qv4internalclass_p.h
index 11c12d012c..04dfd4b654 100644
--- a/src/qml/jsruntime/qv4internalclass_p.h
+++ b/src/qml/jsruntime/qv4internalclass_p.h
@@ -70,7 +70,7 @@ struct PropertyHashData;
 struct PropertyHash
 {
     struct Entry {
-        const Identifier *identifier;
+        Identifier identifier;
         uint index;
     };
 
@@ -82,8 +82,8 @@ struct PropertyHash
     PropertyHash &operator=(const PropertyHash &other);
 
     void addEntry(const Entry &entry, int classSize);
-    uint lookup(const Identifier *identifier) const;
-    int removeIdentifier(Identifier *identifier, int classSize);
+    uint lookup(Identifier identifier) const;
+    int removeIdentifier(Identifier identifier, int classSize);
     void detach(bool grow, int classSize);
 };
 
@@ -129,11 +129,11 @@ inline PropertyHash &PropertyHash::operator=(const PropertyHash &other)
 
 
 
-inline uint PropertyHash::lookup(const Identifier *identifier) const
+inline uint PropertyHash::lookup(Identifier identifier) const
 {
     Q_ASSERT(d->entries);
 
-    uint idx = identifier->id % d->alloc;
+    uint idx = identifier.id % d->alloc;
     while (1) {
         if (d->entries[idx].identifier == identifier)
             return d->entries[idx].index;
@@ -237,7 +237,7 @@ struct SharedInternalClassData {
 struct InternalClassTransition
 {
     union {
-        Identifier *id;
+        Identifier id;
         const VTable *vtable;
         Heap::Object *prototype;
     };
@@ -261,6 +261,8 @@ struct InternalClassTransition
     { return id < other.id || (id == other.id && flags < other.flags); }
 };
 
+static_assert(sizeof(Identifier) == sizeof(VTable *), "Identifier needs to be one pointer large to map into the union above");
+
 namespace Heap {
 
 struct InternalClass : Base {
@@ -271,7 +273,7 @@ struct InternalClass : Base {
     InternalClass *parent;
 
     PropertyHash propertyTable; // id to valueIndex
-    SharedInternalClassData<Identifier *> nameMap;
+    SharedInternalClassData<Identifier> nameMap;
     SharedInternalClassData<PropertyAttributes> propertyData;
 
     typedef InternalClassTransition Transition;
@@ -292,12 +294,12 @@ struct InternalClass : Base {
 
     static void addMember(QV4::Object *object, QV4::String *string, PropertyAttributes data, uint *index);
     Q_REQUIRED_RESULT InternalClass *addMember(QV4::String *string, PropertyAttributes data, uint *index = nullptr);
-    Q_REQUIRED_RESULT InternalClass *addMember(Identifier *identifier, PropertyAttributes data, uint *index = nullptr);
-    Q_REQUIRED_RESULT InternalClass *changeMember(Identifier *identifier, PropertyAttributes data, uint *index = nullptr);
+    Q_REQUIRED_RESULT InternalClass *addMember(Identifier identifier, PropertyAttributes data, uint *index = nullptr);
+    Q_REQUIRED_RESULT InternalClass *changeMember(Identifier identifier, PropertyAttributes data, uint *index = nullptr);
     static void changeMember(QV4::Object *object, QV4::String *string, PropertyAttributes data, uint *index = nullptr);
-    static void removeMember(QV4::Object *object, Identifier *identifier);
+    static void removeMember(QV4::Object *object, Identifier identifier);
     uint find(const QV4::String *string);
-    uint find(const Identifier *id)
+    uint find(const Identifier id)
     {
         uint index = propertyTable.lookup(id);
         if (index < size)
@@ -330,7 +332,7 @@ struct InternalClass : Base {
 private:
     Q_QML_EXPORT InternalClass *changeVTableImpl(const VTable *vt);
     Q_QML_EXPORT InternalClass *changePrototypeImpl(Heap::Object *proto);
-    InternalClass *addMemberImpl(Identifier *identifier, PropertyAttributes data, uint *index);
+    InternalClass *addMemberImpl(Identifier identifier, PropertyAttributes data, uint *index);
 
     void removeChildEntry(InternalClass *child);
     friend struct ExecutionEngine;
diff --git a/src/qml/jsruntime/qv4lookup.cpp b/src/qml/jsruntime/qv4lookup.cpp
index fdf3d7685d..cd9583cccb 100644
--- a/src/qml/jsruntime/qv4lookup.cpp
+++ b/src/qml/jsruntime/qv4lookup.cpp
@@ -47,7 +47,7 @@ QT_BEGIN_NAMESPACE
 using namespace QV4;
 
 
-void Lookup::resolveProtoGetter(Identifier *name, const Heap::Object *proto)
+void Lookup::resolveProtoGetter(Identifier name, const Heap::Object *proto)
 {
     while (proto) {
         uint index = proto->internalClass->find(name);
@@ -70,7 +70,7 @@ void Lookup::resolveProtoGetter(Identifier *name, const Heap::Object *proto)
 ReturnedValue Lookup::resolveGetter(ExecutionEngine *engine, const Object *object)
 {
     Heap::Object *obj = object->d();
-    Identifier *name = engine->identifierTable->identifier(engine->currentStackFrame->v4Function->compilationUnit->runtimeStrings[nameIndex]);
+    Identifier name = engine->identifierTable->identifier(engine->currentStackFrame->v4Function->compilationUnit->runtimeStrings[nameIndex]);
 
     uint index = obj->internalClass->find(name);
     if (index != UINT_MAX) {
@@ -125,7 +125,7 @@ ReturnedValue Lookup::resolvePrimitiveGetter(ExecutionEngine *engine, const Valu
         primitiveLookup.proto = engine->numberPrototype()->d();
     }
 
-    Identifier *name = engine->identifierTable->identifier(engine->currentStackFrame->v4Function->compilationUnit->runtimeStrings[nameIndex]);
+    Identifier name = engine->identifierTable->identifier(engine->currentStackFrame->v4Function->compilationUnit->runtimeStrings[nameIndex]);
     protoLookup.protoId = primitiveLookup.proto->internalClass->protoId;
     resolveProtoGetter(name, primitiveLookup.proto);
 
@@ -139,7 +139,7 @@ ReturnedValue Lookup::resolvePrimitiveGetter(ExecutionEngine *engine, const Valu
 ReturnedValue Lookup::resolveGlobalGetter(ExecutionEngine *engine)
 {
     Object *o = engine->globalObject;
-    Identifier *name = engine->identifierTable->identifier(engine->currentStackFrame->v4Function->compilationUnit->runtimeStrings[nameIndex]);
+    Identifier name = engine->identifierTable->identifier(engine->currentStackFrame->v4Function->compilationUnit->runtimeStrings[nameIndex]);
     protoLookup.protoId = o->internalClass()->protoId;
     resolveProtoGetter(name, o->d());
 
diff --git a/src/qml/jsruntime/qv4lookup_p.h b/src/qml/jsruntime/qv4lookup_p.h
index 49eb66d1fb..eb6ad067d7 100644
--- a/src/qml/jsruntime/qv4lookup_p.h
+++ b/src/qml/jsruntime/qv4lookup_p.h
@@ -117,7 +117,7 @@ struct Lookup {
     ReturnedValue resolveGetter(ExecutionEngine *engine, const Object *object);
     ReturnedValue resolvePrimitiveGetter(ExecutionEngine *engine, const Value &object);
     ReturnedValue resolveGlobalGetter(ExecutionEngine *engine);
-    void resolveProtoGetter(Identifier *name, const Heap::Object *proto);
+    void resolveProtoGetter(Identifier name, const Heap::Object *proto);
 
     static ReturnedValue getterGeneric(Lookup *l, ExecutionEngine *engine, const Value &object);
     static ReturnedValue getterTwoClasses(Lookup *l, ExecutionEngine *engine, const Value &object);
diff --git a/src/qml/jsruntime/qv4managed_p.h b/src/qml/jsruntime/qv4managed_p.h
index b35788a711..7c5bda3efb 100644
--- a/src/qml/jsruntime/qv4managed_p.h
+++ b/src/qml/jsruntime/qv4managed_p.h
@@ -273,7 +273,7 @@ struct InternalClass : Managed
     Q_REQUIRED_RESULT Heap::InternalClass *addMember(QV4::String *string, PropertyAttributes data, uint *index = 0) {
         return d()->addMember(string, data, index);
     }
-    Q_REQUIRED_RESULT Heap::InternalClass *addMember(Identifier *identifier, PropertyAttributes data, uint *index = 0) {
+    Q_REQUIRED_RESULT Heap::InternalClass *addMember(Identifier identifier, PropertyAttributes data, uint *index = 0) {
         return d()->addMember(identifier, data, index);
     }
 
diff --git a/src/qml/jsruntime/qv4object.cpp b/src/qml/jsruntime/qv4object.cpp
index d7cad2231e..56f93ef1ce 100644
--- a/src/qml/jsruntime/qv4object.cpp
+++ b/src/qml/jsruntime/qv4object.cpp
@@ -267,7 +267,7 @@ void Object::getOwnProperty(String *name, PropertyAttributes *attrs, Property *p
         return getOwnProperty(idx, attrs, p);
 
     name->makeIdentifier();
-    Identifier *id = name->identifier();
+    Identifier id = name->identifier();
 
     uint member = internalClass()->find(id);
     if (member < UINT_MAX) {
@@ -309,7 +309,7 @@ MemberData::Index Object::getValueOrSetter(String *name, PropertyAttributes *att
     Q_ASSERT(name->asArrayIndex() == UINT_MAX);
 
     name->makeIdentifier();
-    Identifier *id = name->identifier();
+    Identifier id = name->identifier();
 
     Heap::Object *o = d();
     while (o) {
@@ -389,7 +389,7 @@ bool Object::hasOwnProperty(String *name) const
         return hasOwnProperty(idx);
 
     name->makeIdentifier();
-    Identifier *id = name->identifier();
+    Identifier id = name->identifier();
 
     if (internalClass()->find(id) < UINT_MAX)
         return true;
@@ -449,7 +449,7 @@ PropertyAttributes Object::query(const Managed *m, String *name)
         return queryIndexed(m, idx);
 
     name->makeIdentifier();
-    Identifier *id = name->identifier();
+    Identifier id = name->identifier();
 
     const Object *o = static_cast<const Object *>(m);
     idx = o->internalClass()->find(id);
@@ -529,7 +529,7 @@ void Object::advanceIterator(Managed *m, ObjectIterator *it, Value *name, uint *
     }
 
     while (it->memberIndex < o->internalClass()->size) {
-        Identifier *n = o->internalClass()->nameMap.at(it->memberIndex);
+        Identifier n = o->internalClass()->nameMap.at(it->memberIndex);
         if (!n) {
             // accessor properties have a dummy entry with n == 0
             ++it->memberIndex;
@@ -540,7 +540,7 @@ void Object::advanceIterator(Managed *m, ObjectIterator *it, Value *name, uint *
         PropertyAttributes a = o->internalClass()->propertyData[it->memberIndex];
         ++it->memberIndex;
         if (!(it->flags & ObjectIterator::EnumerableOnly) || a.isEnumerable()) {
-            name->setM(o->engine()->identifierTable->stringFromIdentifier(n));
+            name->setM(o->engine()->identifierTable->stringForId(n));
             *attrs = a;
             pd->value = *o->propertyData(idx);
             if (a.isAccessor())
@@ -560,7 +560,7 @@ ReturnedValue Object::internalGet(String *name, bool *hasProperty) const
         return getIndexed(idx, hasProperty);
 
     name->makeIdentifier();
-    Identifier *id = name->identifier();
+    Identifier id = name->identifier();
 
     Heap::Object *o = d();
     while (o) {
@@ -627,7 +627,7 @@ bool Object::internalPut(String *name, const Value &value)
         return putIndexed(idx, value);
 
     name->makeIdentifier();
-    Identifier *id = name->identifier();
+    Identifier id = name->identifier();
 
     MemberData::Index memberIndex{nullptr, nullptr};
     uint member = internalClass()->find(id);
diff --git a/src/qml/jsruntime/qv4string.cpp b/src/qml/jsruntime/qv4string.cpp
index 57832a0068..a7a8868bdd 100644
--- a/src/qml/jsruntime/qv4string.cpp
+++ b/src/qml/jsruntime/qv4string.cpp
@@ -175,7 +175,7 @@ void Heap::String::simplifyString() const
     text = result.data_ptr();
     text->ref.ref();
     const ComplexString *cs = static_cast<const ComplexString *>(this);
-    identifier = nullptr;
+    identifier = Identifier::invalid();
     cs->left = cs->right = nullptr;
 
     internalClass->engine->memoryManager->changeUnmanagedHeapSizeUsage(qptrdiff(text->size) * (qptrdiff)sizeof(QChar));
diff --git a/src/qml/jsruntime/qv4string_p.h b/src/qml/jsruntime/qv4string_p.h
index 72c4057b20..200d979f24 100644
--- a/src/qml/jsruntime/qv4string_p.h
+++ b/src/qml/jsruntime/qv4string_p.h
@@ -108,7 +108,7 @@ struct Q_QML_PRIVATE_EXPORT String : Base {
         if (hashValue() != other->hashValue())
             return false;
         Q_ASSERT(subtype < StringType_Complex);
-        if (identifier && identifier == other->identifier)
+        if (identifier.isValid() && identifier == other->identifier)
             return true;
         if (subtype == Heap::String::StringType_ArrayIndex && other->subtype == Heap::String::StringType_ArrayIndex)
             return true;
@@ -119,7 +119,7 @@ struct Q_QML_PRIVATE_EXPORT String : Base {
     bool startsWithUpper() const;
 
     mutable QStringData *text;
-    mutable Identifier *identifier;
+    mutable Identifier identifier;
     mutable uint subtype;
     mutable uint stringHash;
 private:
@@ -192,7 +192,7 @@ struct Q_QML_PRIVATE_EXPORT String : public Managed {
     uint toUInt(bool *ok) const;
 
     void makeIdentifier() const {
-        if (d()->identifier)
+        if (d()->identifier.isValid())
             return;
         makeIdentifierImpl();
     }
@@ -214,7 +214,7 @@ struct Q_QML_PRIVATE_EXPORT String : public Managed {
 
     bool startsWithUpper() const { return d()->startsWithUpper(); }
 
-    Identifier *identifier() const { return d()->identifier; }
+    Identifier identifier() const { return d()->identifier; }
 
 protected:
     static bool isEqualTo(Managed *that, Managed *o);