Incremental mode now works for x64. The only difference

src/mark-compact.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 111 matching lines @@
   void TransferMark(Address old_start, Address new_start);
 
 #ifdef DEBUG
   enum ObjectColor {
     BLACK_OBJECT,
     WHITE_OBJECT,
     GREY_OBJECT,
     IMPOSSIBLE_COLOR
   };
 
+  static const char* ColorName(ObjectColor color) {
+    switch (color) {
+      case BLACK_OBJECT: return "black";
+      case WHITE_OBJECT: return "white";
+      case GREY_OBJECT: return "grey";
+      case IMPOSSIBLE_COLOR: return "impossible";
+    }
+    return "error";
+  }
+
   static ObjectColor Color(HeapObject* obj) {
     return Color(Marking::MarkBitFrom(obj));
   }
 
   static ObjectColor Color(MarkBit mark_bit) {
     if (IsBlack(mark_bit)) return BLACK_OBJECT;
     if (IsWhite(mark_bit)) return WHITE_OBJECT;
     if (IsGrey(mark_bit)) return GREY_OBJECT;
     UNREACHABLE();
     return IMPOSSIBLE_COLOR;
@@ skipping 411 matching lines @@
   MarkingDeque marking_deque_;
   CodeFlusher* code_flusher_;
 
   friend class Heap;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_MARK_COMPACT_H_