Simplify the write barrier.

src/spaces.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 106 matching lines @@
 class MemoryAllocator;
 class AllocationInfo;
 class Space;
 class FreeList;
 class MemoryChunk;
 
 class MarkBit {
  public:
   typedef uint32_t CellType;
 
-  inline MarkBit(CellType* cell, CellType mask, bool data_only)
-      : cell_(cell), mask_(mask), data_only_(data_only) { }
+  inline MarkBit(CellType* cell, CellType mask)
+      : cell_(cell), mask_(mask) { }
 
   inline CellType* cell() { return cell_; }
   inline CellType mask() { return mask_; }
 
 #ifdef DEBUG
   bool operator==(const MarkBit& other) {
     return cell_ == other.cell_ && mask_ == other.mask_;
   }
 #endif
 
   inline void Set() { *cell_ |= mask_; }
   inline bool Get() { return (*cell_ & mask_) != 0; }
   inline void Clear() { *cell_ &= ~mask_; }
 
-  inline bool data_only() { return data_only_; }
-
   inline MarkBit Next() {
     CellType new_mask = mask_ << 1;
     if (new_mask == 0) {
-      return MarkBit(cell_ + 1, 1, data_only_);
+      return MarkBit(cell_ + 1, 1);
     } else {
-      return MarkBit(cell_, new_mask, data_only_);
+      return MarkBit(cell_, new_mask);
     }
   }
 
  private:
   CellType* cell_;
   CellType mask_;
-  // This boolean indicates that the object is in a data-only space with no
-  // pointers.  This enables some optimizations when marking.
-  // It is expected that this field is inlined and turned into control flow
-  // at the place where the MarkBit object is created.
-  bool data_only_;
 };
 
 
 // Bitmap is a sequence of cells each containing fixed number of bits.
 class Bitmap {
  public:
   static const uint32_t kBitsPerCell = 32;
   static const uint32_t kBitsPerCellLog2 = 5;
   static const uint32_t kBitIndexMask = kBitsPerCell - 1;
   static const uint32_t kBytesPerCell = kBitsPerCell / kBitsPerByte;
@@ skipping 35 matching lines @@
   }
 
   INLINE(Address address()) {
     return reinterpret_cast<Address>(this);
   }
 
   INLINE(static Bitmap* FromAddress(Address addr)) {
     return reinterpret_cast<Bitmap*>(addr);
   }
 
-  inline MarkBit MarkBitFromIndex(uint32_t index, bool data_only = false) {
+  inline MarkBit MarkBitFromIndex(uint32_t index) {
     MarkBit::CellType mask = 1 << (index & kBitIndexMask);
     MarkBit::CellType* cell = this->cells() + (index >> kBitsPerCellLog2);
-    return MarkBit(cell, mask, data_only);
+    return MarkBit(cell, mask);
   }
 
   static inline void Clear(MemoryChunk* chunk);
 
   static void PrintWord(uint32_t word, uint32_t himask = 0) {
     for (uint32_t mask = 1; mask != 0; mask <<= 1) {
       if ((mask & himask) != 0) PrintF("[");
       PrintF((mask & word) ? "1" : "0");
       if ((mask & himask) != 0) PrintF("]");
     }
@@ skipping 2392 matching lines @@
   }
   // Must be small, since an iteration is used for lookup.
   static const int kMaxComments = 64;
 };
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_SPACES_H_