Simplify handling of non GC managed heap data

Let the destroy() method in QV4::String clean up the
unmanaged heap size instead of having a special hook in
the code that sweeps the GC heap.

Change-Id: I989ee99604f0cc67b896d3acc94e200dd5e56a60
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

src/qml/jsruntime/qv4string.cpp

@@ -114,6 +114,15 @@ void Heap::String::init(MemoryManager *mm, String *l, String *r)
         simplifyString();
 }
 
+void Heap::String::destroy() {
+    if (!largestSubLength) {
+        mm->changeUnmanagedHeapSizeUsage(qptrdiff(-text->size) * (int)sizeof(QChar));
+        if (!text->ref.deref())
+            QStringData::deallocate(text);
+    }
+    Base::destroy();
+}
+
 uint String::toUInt(bool *ok) const
 {
     *ok = true;
@@ -152,7 +161,7 @@ void Heap::String::simplifyString() const
     text->ref.ref();
     identifier = 0;
     largestSubLength = 0;
-    mm->growUnmanagedHeapSizeUsage(size_t(text->size) * sizeof(QChar));
+    mm->changeUnmanagedHeapSizeUsage(qptrdiff(text->size) * (qptrdiff)sizeof(QChar));
 }
 
 void Heap::String::append(const String *data, QChar *ch)

src/qml/jsruntime/qv4string_p.h

@@ -73,11 +73,7 @@ struct Q_QML_PRIVATE_EXPORT String : Base {
 #ifndef V4_BOOTSTRAP
     void init(MemoryManager *mm, const QString &text);
     void init(MemoryManager *mm, String *l, String *n);
-    void destroy() {
+    void destroy();
-        if (!largestSubLength && !text->ref.deref())
-            QStringData::deallocate(text);
-        Base::destroy();
-    }
     void simplifyString() const;
     int length() const {
         Q_ASSERT((largestSubLength &&

src/qml/memory/qv4mm.cpp

@@ -194,10 +194,8 @@ struct MemoryManager::Data
 
 namespace {
 
-bool sweepChunk(MemoryManager::Data::ChunkHeader *header, uint *itemsInUse, ExecutionEngine *engine, std::size_t *unmanagedHeapSize)
+bool sweepChunk(MemoryManager::Data::ChunkHeader *header, uint *itemsInUse, ExecutionEngine *engine)
 {
-    Q_ASSERT(unmanagedHeapSize);
-
     bool isEmpty = true;
     Heap::Base *tail = &header->freeItems;
 //    qDebug("chunkStart @ %p, size=%x, pos=%x", header->itemStart, header->itemSize, header->itemSize>>4);
@@ -222,13 +220,6 @@ bool sweepChunk(MemoryManager::Data::ChunkHeader *header, uint *itemsInUse, Exec
 #ifdef V4_USE_VALGRIND
                 VALGRIND_ENABLE_ERROR_REPORTING;
 #endif
-                if (std::size_t(header->itemSize) == MemoryManager::align(sizeof(Heap::String)) && m->vtable()->isString) {
-                    std::size_t heapBytes = static_cast<Heap::String *>(m)->retainedTextSize();
-                    Q_ASSERT(*unmanagedHeapSize >= heapBytes);
-//                    qDebug() << "-- it's a string holding on to" << heapBytes << "bytes";
-                    *unmanagedHeapSize -= heapBytes;
-                }
-
                 if (m->vtable()->destroy) {
                     m->vtable()->destroy(m);
                     m->_checkIsDestroyed();
@@ -502,7 +493,7 @@ void MemoryManager::sweep(bool lastSweep)
 
     for (size_t i = 0; i < m_d->heapChunks.size(); ++i) {
         Data::ChunkHeader *header = reinterpret_cast<Data::ChunkHeader *>(m_d->heapChunks[i].base());
-        chunkIsEmpty[i] = sweepChunk(header, &itemsInUse[header->itemSize >> 4], engine, &m_d->unmanagedHeapSize);
+        chunkIsEmpty[i] = sweepChunk(header, &itemsInUse[header->itemSize >> 4], engine);
     }
 
     std::vector<PageAllocation>::iterator chunkIter = m_d->heapChunks.begin();
@@ -642,7 +633,7 @@ size_t MemoryManager::getLargeItemsMem() const
     return total;
 }
 
-void MemoryManager::growUnmanagedHeapSizeUsage(size_t delta)
+void MemoryManager::changeUnmanagedHeapSizeUsage(qptrdiff delta)
 {
     m_d->unmanagedHeapSize += delta;
 }

src/qml/memory/qv4mm_p.h

@@ -297,7 +297,7 @@ public:
     size_t getAllocatedMem() const;
     size_t getLargeItemsMem() const;
 
-    void growUnmanagedHeapSizeUsage(size_t delta); // called when a JS object grows itself. Specifically: Heap::String::append
+    void changeUnmanagedHeapSizeUsage(qptrdiff delta); // called when a JS object grows itself. Specifically: Heap::String::append
 
 protected:
     /// expects size to be aligned