Separate the stack used for GC from the regular JS stack

This is required to be able to implement concurrent or
incremental garbage collection.

Change-Id: Ib3c5eee3779ca2ee08a57cd3961dbcb0537bbb54
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

1 files changed, 21 insertions, 1 deletions

diff --git a/src/qml/memory/qv4mmdefs_p.h b/src/qml/memory/qv4mmdefs_p.h
index 1fc7b6a527..9512722782 100644
--- a/src/qml/memory/qv4mmdefs_p.h
+++ b/src/qml/memory/qv4mmdefs_p.h
@@ -59,6 +59,8 @@ QT_BEGIN_NAMESPACE
 
 namespace QV4 {
 
+struct MarkStack;
+
 /*
  * Chunks are the basic structure containing GC managed objects.
  *
@@ -185,7 +187,7 @@ struct Chunk {
     void sweep();
     void freeAll();
     void resetBlackBits();
-    void collectGrayItems(ExecutionEngine *engine);
+    void collectGrayItems(QV4::MarkStack *markStack);
 
     void sortIntoBins(HeapItem **bins, uint nBins);
 };
@@ -265,6 +267,24 @@ Q_STATIC_ASSERT(sizeof(HeapItem) == Chunk::SlotSize);
 Q_STATIC_ASSERT(QT_POINTER_SIZE*8 == Chunk::Bits);
 Q_STATIC_ASSERT((1 << Chunk::BitShift) == Chunk::Bits);
 
+struct MarkStack {\
+    MarkStack(ExecutionEngine *engine);
+    Heap::Base **top = 0;
+    Heap::Base **base = 0;
+    Heap::Base **limit = 0;
+    ExecutionEngine *engine;
+    void push(Heap::Base *m) {
+        *top = m;
+        ++top;
+    }
+    Heap::Base *pop() {
+        --top;
+        return *top;
+    }
+    void drain();
+
+};
+
 // Base class for the execution engine
 
 #if defined(Q_CC_MSVC) || defined(Q_CC_GNU)