Add method to convert identifiers back into QV4::String objects

Allocating a new String for the Identifier is wasting both memory
and CPU. Let's rather extract it from the IdentifierTable.

Change-Id: Ibb9b2ac9775fefce74602d6954586195cdd5814e
Reviewed-by: Simon Hausmann <simon.hausmann@theqtcompany.com>

3 files changed, 20 insertions, 1 deletions

diff --git a/src/qml/jsruntime/qv4identifiertable.cpp b/src/qml/jsruntime/qv4identifiertable.cpp
index 138d76bf4a..a5336ee44f 100644
--- a/src/qml/jsruntime/qv4identifiertable.cpp
+++ b/src/qml/jsruntime/qv4identifiertable.cpp
@@ -149,6 +149,22 @@ Identifier *IdentifierTable::identifierImpl(const Heap::String *str)
     return str->identifier;
 }
 
+Heap::String *IdentifierTable::stringFromIdentifier(Identifier *i)
+{
+    if (!i)
+        return 0;
+
+    uint idx = i->hashValue % alloc;
+    while (1) {
+        Heap::String *e = entries[idx];
+        Q_ASSERT(e);
+        if (e->identifier == i)
+            return e;
+        ++idx;
+        idx %= alloc;
+    }
+}
+
 Identifier *IdentifierTable::identifier(const QString &s)
 {
     return insertString(s)->identifier;
diff --git a/src/qml/jsruntime/qv4identifiertable_p.h b/src/qml/jsruntime/qv4identifiertable_p.h
index 58f808b4d5..d91ce623c1 100644
--- a/src/qml/jsruntime/qv4identifiertable_p.h
+++ b/src/qml/jsruntime/qv4identifiertable_p.h
@@ -74,6 +74,8 @@ public:
 
     Identifier *identifierImpl(const Heap::String *str);
 
+    Heap::String *stringFromIdentifier(Identifier *i);
+
     void mark(ExecutionEngine *e) {
         for (int i = 0; i < alloc; ++i) {
             Heap::String *entry = entries[i];
diff --git a/src/qml/jsruntime/qv4object.cpp b/src/qml/jsruntime/qv4object.cpp
index 42cc3c7df4..ee3539c176 100644
--- a/src/qml/jsruntime/qv4object.cpp
+++ b/src/qml/jsruntime/qv4object.cpp
@@ -44,6 +44,7 @@
 #include "qv4objectiterator_p.h"
 #include "qv4identifier_p.h"
 #include "qv4string_p.h"
+#include "qv4identifiertable_p.h"
 
 #include <stdint.h>
 
@@ -590,7 +591,7 @@ 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()->newString(n->string));
+            name->setM(o->engine()->identifierTable->stringFromIdentifier(n));
             *attrs = a;
             pd->value = *o->propertyData(idx);
             if (a.isAccessor())