New mark table implementation

Automatically generate a table containing the data where JS Values
and pointers are in objects in the JS heap.

This will allow making the GC mark phase a lot more efficient.

A bit of a special hack is currently required for MemberData and
ArrayData, as they have a variable length, and we need to read the
size from the object.

We keep backwards compatibility with the old markObjects() functions
for now (calling them if they are defined). Some further work on
QV4::String and in a few other places is required before we can get
remove the compatibility.

Change-Id: I78528ace67e886bdbe4a4330c9677c7fc9f08a33
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

1 files changed, 48 insertions, 0 deletions

diff --git a/src/qml/memory/qv4mmdefs_p.h b/src/qml/memory/qv4mmdefs_p.h
index 588ae21ee0..90e7d9cb61 100644
--- a/src/qml/memory/qv4mmdefs_p.h
+++ b/src/qml/memory/qv4mmdefs_p.h
@@ -255,6 +255,54 @@ Q_STATIC_ASSERT(sizeof(HeapItem) == Chunk::SlotSize);
 Q_STATIC_ASSERT(QT_POINTER_SIZE*8 == Chunk::Bits);
 Q_STATIC_ASSERT((1 << Chunk::BitShift) == Chunk::Bits);
 
+// Some helper classes and macros to automate the generation of our
+// tables used for marking objects
+
+enum MarkFlags {
+    Mark_NoMark = 0,
+    Mark_Value = 1,
+    Mark_Pointer = 2,
+    Mark_ValueArray = 3
+};
+
+template<typename T>
+struct MarkFlagsForType {
+    static const quint64 markFlags = Mark_NoMark;
+};
+template<typename T>
+struct MarkFlagsForType<Heap::Pointer<T>> {
+    static const quint64 markFlags = Mark_Pointer;
+};
+template<>
+struct MarkFlagsForType<Value> {
+    static const quint64 markFlags = Mark_Value;
+};
+
+typedef Value ValueArray[1];
+template<>
+struct MarkFlagsForType<ValueArray> {
+    static const quint64 markFlags = Mark_ValueArray;
+};
+
+#define HEAP_OBJECT_MEMBER_EXPANSION(c, type, name) type name;
+
+#define HEAP_OBJECT_MARK_EXPANSION(class, type, name) \
+    (MarkFlagsForType<decltype(class::name)>::markFlags << (offsetof(class, name) >> 2)) |
+
+#define DECLARE_HEAP_OBJECT(name, base) \
+struct name##Data { \
+    name##Members(name, HEAP_OBJECT_MEMBER_EXPANSION) \
+}; \
+struct name##SizeStruct : base, name##Data {}; \
+static Q_CONSTEXPR quint64 name##_markTable = \
+    (name##Members(name##Data, HEAP_OBJECT_MARK_EXPANSION) 0) << (((sizeof(name##SizeStruct) - sizeof(name##Data)) >> 2) | QV4::Heap::base::markTable; \
+    \
+struct name : base, name##Data
+
+#define DECLARE_MARK_TABLE(class) static Q_CONSTEXPR quint64 markTable = class##_markTable
+
+
+
 }
 
 QT_END_NAMESPACE