Preserve marking bits across scavenges if incremental marker is running.

src/incremental-marking.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 40 matching lines @@
   }
 
   static inline bool IsStopped() { return state() == STOPPED; }
 
   static bool WorthActivating();
 
   static void Start();
 
   static void Stop();
 
+  static void PrepareForScavenge();
+
+  static void UpdateMarkingStackAfterScavenge();
+
   static void Hurry();
 
   static void Finalize();
 
   static void MarkingComplete();
 
   static const intptr_t kAllocatedThreshold = 1024;
   static const intptr_t kAllocationMarkingFactor = 8;
 
   static void Step(intptr_t allocated);
 
   static inline void RestartIfNotMarking() {
     if (state_ == COMPLETE) {
       state_ = MARKING;
       if (FLAG_trace_incremental_marking) {
         PrintF("[IncrementalMarking] Restarting (new grey objects)\n");
       }
     }
   }
 
   static inline void RecordWrite(HeapObject* obj, Object* value) {
     if (!IsStopped() && value->IsHeapObject()) {
       MarkBit value_bit = Marking::MarkBitFrom(HeapObject::cast(value));
       if (IsWhite(value_bit)) {
         MarkBit obj_bit = Marking::MarkBitFrom(obj);
         if (IsBlack(obj_bit)) {
-          BlackToGrey(obj, obj_bit);
+          BlackToGreyAndPush(obj, obj_bit);
           RestartIfNotMarking();
         }
       }
     }
   }
 
   static inline void RecordWriteOf(HeapObject* value) {
     if (state_ != STOPPED) {
       MarkBit value_bit = Marking::MarkBitFrom(value);
       if (IsWhite(value_bit)) {
-        WhiteToGrey(value, value_bit);
+        WhiteToGreyAndPush(value, value_bit);
         RestartIfNotMarking();
       }
     }
   }
 
 
   static inline void RecordWrites(HeapObject* obj) {
     if (!IsStopped()) {
       MarkBit obj_bit = Marking::MarkBitFrom(obj);
       if (IsBlack(obj_bit)) {
-        BlackToGrey(obj, obj_bit);
+        BlackToGreyAndPush(obj, obj_bit);
         RestartIfNotMarking();
       }
     }
   }
 
   // Impossible markbits: 01
   static inline bool IsImpossible(MarkBit mark_bit) {
     return !mark_bit.Get() && mark_bit.Next().Get();
   }
 
   // Black markbits: 10 - this is required by the sweeper.
   static inline bool IsBlack(MarkBit mark_bit) {
     ASSERT(!IsImpossible(mark_bit));
     return mark_bit.Get() && !mark_bit.Next().Get();
   }
 
   // White markbits: 00 - this is required by the mark bit clearer.
   static inline bool IsWhite(MarkBit mark_bit) {
     ASSERT(!IsImpossible(mark_bit));
     return !mark_bit.Get();
   }
 
   // Grey markbits: 11
   static inline bool IsGrey(MarkBit mark_bit) {
     ASSERT(!IsImpossible(mark_bit));
     return mark_bit.Get() && mark_bit.Next().Get();
   }
 
-  static inline void BlackToGrey(HeapObject* obj, MarkBit mark_bit) {
+  static inline void BlackToGreyAndPush(HeapObject* obj, MarkBit mark_bit) {
     ASSERT(Marking::MarkBitFrom(obj) == mark_bit);
     ASSERT(obj->Size() >= 2*kPointerSize);
     ASSERT(!IsStopped());
     ASSERT(IsBlack(mark_bit));
     mark_bit.Next().Set();
     ASSERT(IsGrey(mark_bit));
 
     marking_stack_.Push(obj);
     ASSERT(!marking_stack_.overflowed());
   }
 
+  static inline void WhiteToGreyAndPush(HeapObject* obj, MarkBit mark_bit) {
+    WhiteToGrey(obj, mark_bit);
+    marking_stack_.Push(obj);
+    ASSERT(!marking_stack_.overflowed());
+  }
+
   static inline void WhiteToGrey(HeapObject* obj, MarkBit mark_bit) {
     ASSERT(Marking::MarkBitFrom(obj) == mark_bit);
     ASSERT(obj->Size() >= 2*kPointerSize);
     ASSERT(!IsStopped());
     ASSERT(IsWhite(mark_bit));
     mark_bit.Set();
     mark_bit.Next().Set();
     ASSERT(IsGrey(mark_bit));
-
-    marking_stack_.Push(obj);
-    ASSERT(!marking_stack_.overflowed());
   }
 
   static inline void MarkBlack(MarkBit mark_bit) {
     mark_bit.Set();
     mark_bit.Next().Clear();
     ASSERT(IsBlack(mark_bit));
   }
 
   static inline const char* ColorStr(MarkBit mark_bit) {
     if (IsBlack(mark_bit)) return "black";
     if (IsWhite(mark_bit)) return "white";
     if (IsGrey(mark_bit)) return "grey";
     UNREACHABLE();
     return "???";
   }
 
+  enum ObjectColor {
+    BLACK_OBJECT,
+    WHITE_OBJECT,
+    GREY_OBJECT,
+    IMPOSSIBLE_COLOR
+  };
+
+  static inline ObjectColor Color(HeapObject* obj) {
+    MarkBit mark_bit = Marking::MarkBitFrom(obj);
+    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;
+  }
+
  private:
   static State state_;
   static MarkingStack marking_stack_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_INCREMENTAL_MARKING_H_