Have more bindingBits available inline

Many QML items have more than 32 properties, so we ended
up malloc'ing the binding bit table on the heap quite
often. Extending the inline data to be able to accommodate
for up to 64 properties fixes that.

Change-Id: I90a42d601a5406ffacf2506f1957b0c2080bbb7b
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

2 files changed, 40 insertions, 43 deletions

diff --git a/src/qml/qml/qqmldata_p.h b/src/qml/qml/qqmldata_p.h
index 4848f48766..5794e6f0c5 100644
--- a/src/qml/qml/qqmldata_p.h
+++ b/src/qml/qml/qqmldata_p.h
@@ -156,18 +156,21 @@ public:
     quint32 hasInterceptorMetaObject:1;
     quint32 hasVMEMetaObject:1;
     quint32 parentFrozen:1;
-    quint32 dummy:22;
+    quint32 dummy:6;
 
     // When bindingBitsSize < sizeof(ptr), we store the binding bit flags inside
     // bindingBitsValue. When we need more than sizeof(ptr) bits, we allocated
     // sufficient space and use bindingBits to point to it.
-    int bindingBitsSize;
+    quint32 bindingBitsArraySize : 16;
     typedef quintptr BindingBitsType;
+    enum {
+        BitsPerType = sizeof(BindingBitsType) * 8,
+        InlineBindingArraySize = 2
+    };
     union {
         BindingBitsType *bindingBits;
-        BindingBitsType bindingBitsValue;
+        BindingBitsType bindingBitsValue[InlineBindingArraySize];
     };
-    enum { MaxInlineBits = sizeof(BindingBitsType) * 8 };
 
     struct NotifyList {
         quint64 connectionMask;
@@ -275,6 +278,9 @@ public:
         return createPropertyCache(engine, object);
     }
 
+    Q_ALWAYS_INLINE static uint offsetForBit(int bit) { return static_cast<uint>(bit) / BitsPerType; }
+    Q_ALWAYS_INLINE static BindingBitsType bitFlagForBit(int bit) { return BindingBitsType(1) << (static_cast<uint>(bit) & (BitsPerType - 1)); }
+
 private:
     // For attachedProperties
     mutable QQmlDataExtended *extendedData;
@@ -286,13 +292,12 @@ private:
 
     Q_ALWAYS_INLINE bool hasBitSet(int bit) const
     {
-        if (bindingBitsSize <= bit)
+        uint offset = offsetForBit(bit);
+        if (bindingBitsArraySize <= offset)
             return false;
 
-        if (bindingBitsSize == MaxInlineBits)
-            return bindingBitsValue & (BindingBitsType(1) << bit);
-        else
-            return bindingBits[bit / MaxInlineBits] & (BindingBitsType(1) << (bit % MaxInlineBits));
+        const BindingBitsType *bits = (bindingBitsArraySize == InlineBindingArraySize) ? bindingBitsValue : bindingBits;
+        return bits[offset] & bitFlagForBit(bit);
     }
 };
 
diff --git a/src/qml/qml/qqmlengine.cpp b/src/qml/qml/qqmlengine.cpp
index 5350ad38a3..c09c048307 100644
--- a/src/qml/qml/qqmlengine.cpp
+++ b/src/qml/qml/qqmlengine.cpp
@@ -110,7 +110,10 @@ Q_DECLARE_METATYPE(QQmlProperty)
 QT_BEGIN_NAMESPACE
 
 typedef QQmlData::BindingBitsType BindingBitsType;
-enum { MaxInlineBits = QQmlData::MaxInlineBits };
+enum {
+    BitsPerType = QQmlData::BitsPerType,
+    InlineBindingArraySize = QQmlData::InlineBindingArraySize
+};
 
 void qmlRegisterBaseTypes(const char *uri, int versionMajor, int versionMinor)
 {
@@ -741,11 +744,12 @@ QQmlData::QQmlData()
     : ownedByQml1(false), ownMemory(true), indestructible(true), explicitIndestructibleSet(false),
       hasTaintedV4Object(false), isQueuedForDeletion(false), rootObjectInCreation(false),
       hasInterceptorMetaObject(false), hasVMEMetaObject(false), parentFrozen(false),
-      bindingBitsSize(MaxInlineBits), bindingBitsValue(0), notifyList(0),
+      bindingBitsArraySize(InlineBindingArraySize), notifyList(0),
       bindings(0), signalHandlers(0), nextContextObject(0), prevContextObject(0),
       lineNumber(0), columnNumber(0), jsEngineId(0), compilationUnit(0),
       propertyCache(0), guards(0), extendedData(0)
 {
+    memset(bindingBitsValue, 0, sizeof(bindingBitsValue));
     init();
 }
 
@@ -1792,7 +1796,7 @@ void QQmlData::destroyed(QObject *object)
         signalHandler = next;
     }
 
-    if (bindingBitsSize > MaxInlineBits)
+    if (bindingBitsArraySize > InlineBindingArraySize)
         free(bindingBits);
 
     if (propertyCache)
@@ -1841,47 +1845,35 @@ void QQmlData::parentChanged(QObject *object, QObject *parent)
 
 static void QQmlData_setBit(QQmlData *data, QObject *obj, int bit)
 {
-    if (Q_UNLIKELY(data->bindingBitsSize <= bit)) {
+    uint offset = QQmlData::offsetForBit(bit);
+    BindingBitsType *bits = (data->bindingBitsArraySize == InlineBindingArraySize) ? data->bindingBitsValue : data->bindingBits;
+    if (Q_UNLIKELY(data->bindingBitsArraySize <= offset)) {
         int props = QQmlMetaObject(obj).propertyCount();
         Q_ASSERT(bit < 2 * props);
 
-        int arraySize = (2 * props + MaxInlineBits - 1) / MaxInlineBits;
-        Q_ASSERT(arraySize > 1);
-
-        // special handling for 32 here is to make sure we wipe the first byte
-        // when going from bindingBitsValue to bindingBits, and preserve the old
-        // set bits so we can restore them after the allocation
-        int oldArraySize = data->bindingBitsSize > MaxInlineBits ? data->bindingBitsSize / MaxInlineBits : 0;
-        quintptr oldValue = data->bindingBitsSize == MaxInlineBits ? data->bindingBitsValue : 0;
-
-        data->bindingBits = static_cast<BindingBitsType *>(realloc((data->bindingBitsSize == MaxInlineBits) ? 0 : data->bindingBits,
-                                                                   arraySize * sizeof(BindingBitsType)));
-
-        memset(data->bindingBits + oldArraySize,
-               0x00,
-               sizeof(BindingBitsType) * (arraySize - oldArraySize));
+        uint arraySize = (2 * static_cast<uint>(props) + BitsPerType - 1) / BitsPerType;
+        Q_ASSERT(arraySize > InlineBindingArraySize && arraySize > data->bindingBitsArraySize);
 
-        data->bindingBitsSize = arraySize * MaxInlineBits;
+        BindingBitsType *newBits = static_cast<BindingBitsType *>(malloc(arraySize*sizeof(BindingBitsType)));
+        memcpy(newBits, bits, data->bindingBitsArraySize * sizeof(BindingBitsType));
+        memset(newBits + data->bindingBitsArraySize, 0, sizeof(BindingBitsType) * (arraySize - data->bindingBitsArraySize));
 
-        // reinstate bindingBitsValue after we dropped it
-        if (oldValue) {
-            memcpy(data->bindingBits, &oldValue, sizeof(oldValue));
-        }
+        if (data->bindingBitsArraySize > InlineBindingArraySize)
+            free(bits);
+        data->bindingBits = newBits;
+        bits = newBits;
+        data->bindingBitsArraySize = arraySize;
     }
-
-    if (data->bindingBitsSize == MaxInlineBits)
-        data->bindingBitsValue |= BindingBitsType(1) << bit;
-    else
-        data->bindingBits[bit / MaxInlineBits] |= (BindingBitsType(1) << (bit % MaxInlineBits));
+    Q_ASSERT(offset < data->bindingBitsArraySize);
+    bits[offset] |= QQmlData::bitFlagForBit(bit);
 }
 
 static void QQmlData_clearBit(QQmlData *data, int bit)
 {
-    if (data->bindingBitsSize > bit) {
-        if (data->bindingBitsSize == MaxInlineBits)
-            data->bindingBitsValue &= ~(BindingBitsType(1) << (bit % MaxInlineBits));
-        else
-            data->bindingBits[bit / MaxInlineBits] &= ~(BindingBitsType(1) << (bit % MaxInlineBits));
+    uint offset = QQmlData::offsetForBit(bit);
+    if (data->bindingBitsArraySize > offset) {
+        BindingBitsType *bits = (data->bindingBitsArraySize == InlineBindingArraySize) ? data->bindingBitsValue : data->bindingBits;
+        bits[offset] &= ~QQmlData::bitFlagForBit(bit);
     }
 }