Allow partial scanning of large arrays in order to avoid

src/mark-compact.h

Index: src/mark-compact.h
===================================================================
--- src/mark-compact.h	(revision 12610)
+++ src/mark-compact.h	(working copy)
@@ -240,6 +240,35 @@
   int mask() { return mask_; }
   void set_top(int top) { top_ = top; }
 
+  int space_left() {
+    // If we already overflowed we may as well just say there is lots of
+    // space left.
+    if (overflowed_) return mask_ + 1;
+    if (IsEmpty()) return mask_ + 1;
+    if (IsFull()) return 0;
+    return (bottom_ - top_) & mask_;
+  }
+
+#ifdef DEBUG
+  const char* Status() {
+    if (overflowed_) return "Overflowed";
+    if (IsEmpty()) return "Empty";
+    if (IsFull()) return "Full";
+    int oct = (((top_ - bottom_) & mask_) * 8) / (mask_ + 1);
+    switch (oct) {
+      case 0: return "Almost empty";
+      case 1: return "1/8 full";
+      case 2: return "2/8 full";
+      case 3: return "3/8 full";
+      case 4: return "4/8 full";
+      case 5: return "5/8 full";
+      case 6: return "6/8 full";
+      case 7: return "7/8 full";
+    }
+    return "??";
+  }
+#endif
+
  private:
   HeapObject** array_;
   // array_[(top - 1) & mask_] is the top element in the deque.  The Deque is
@@ -566,6 +595,10 @@
 
   bool is_compacting() const { return compacting_; }
 
+  // Find the large objects that are not completely scanned, but have been
+  // postponed to later.
+  static void ProcessLargePostponedArrays(Heap* heap, MarkingDeque* deque);
+
  private:
   MarkCompactCollector();
   ~MarkCompactCollector();