Garbage collect identifiers

Implemented by storing a backpointer to the Heap object
in the identifier.

Since identifiers now point back to their originating
String or Symbol, we can now easily mark all identifiers
that are still in use and collect those that aren't.

Since Identifiers are 64bit also add support for holding an
array index in there. With that an identifier can describe
any kind of property that can be accessed in an object. This
helps speed up and simplify some code paths.

To make this possible, we need to register all
IdentifierHash instances with the identifier table, so that
we can properly mark those identifiers.

Change-Id: Icadbaf5712ab9d252d4e71aa4a520e86b14cd2a0
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

1 files changed, 9 insertions, 0 deletions

diff --git a/src/qml/jsruntime/qv4string_p.h b/src/qml/jsruntime/qv4string_p.h
index a1763522b5..4e35853f69 100644
--- a/src/qml/jsruntime/qv4string_p.h
+++ b/src/qml/jsruntime/qv4string_p.h
@@ -68,6 +68,15 @@ struct Q_QML_PRIVATE_EXPORT StringOrSymbol : Base
 {
     mutable QStringData *text;
     mutable Identifier identifier;
+    static void markObjects(Heap::Base *that, MarkStack *markStack);
+
+    inline QString toQString() const {
+        if (!text)
+            return QString();
+        QStringDataPtr ptr = { text };
+        text->ref.ref();
+        return QString(ptr);
+    }
 };
 
 struct Q_QML_PRIVATE_EXPORT String : StringOrSymbol {