VERIFY_PREDICTABLE build mode introduced. Shadow pages support added.

src/spaces.h

Index: src/spaces.h
diff --git a/src/spaces.h b/src/spaces.h
index 93e247846836423a495bac3848ff1fd4311242f3..10d0172a127a018746266c92588d4b148c80b9f2 100644
--- a/src/spaces.h
+++ b/src/spaces.h
@@ -306,6 +306,11 @@ class MemoryChunk {
     Release_Store(&prev_chunk_, reinterpret_cast<AtomicWord>(prev));
   }
 
+  uintptr_t shadow_data_offset() { return shadow_data_offset_; }
+
+  MemoryChunk* shadow_chunk() { return shadow_chunk_; }
+  void set_shadow_chunk(MemoryChunk* shadow) { shadow_chunk_ = shadow; }
+
   Space* owner() const {
     if ((reinterpret_cast<intptr_t>(owner_) & kFailureTagMask) ==
         kFailureTag) {
@@ -547,6 +552,7 @@ class MemoryChunk {
   static const intptr_t kLiveBytesOffset =
      kSizeOffset + kPointerSize + kPointerSize + kPointerSize +
      kPointerSize + kPointerSize +
+     kPointerSize + kPointerSize + kPointerSize +
      kPointerSize + kPointerSize + kPointerSize + kIntSize;
 
   static const size_t kSlotsBufferOffset = kLiveBytesOffset + kIntSize;
@@ -685,6 +691,12 @@ class MemoryChunk {
   Address area_start_;
   Address area_end_;
 
+  MemoryChunk* shadow_chunk_;
+  // Offset to object's shadow data.
+  intptr_t shadow_data_offset_;
+  // Shadow data storage for large objects.
+  intptr_t large_object_shadow_data_;
+
   // If the chunk needs to remember its memory reservation, it is stored here.
   VirtualMemory reservation_;
   // The identity of the owning space.  This is tagged as a failure pointer, but
@@ -1110,6 +1122,14 @@ class MemoryAllocator {
                              Executability executable,
                              Space* space);
 
+  // Allocates shadow page of respective size and sets it as a shadow
+  // of given chunk.
+  bool AllocateShadowChunkFor(MemoryChunk* chunk);
+
+  // Frees and clears shadow page of given chunk.
+  void FreeShadowChunkFor(MemoryChunk* chunk);
+
+
   Address ReserveAlignedMemory(size_t requested,
                                size_t alignment,
                                VirtualMemory* controller);
@@ -2285,6 +2305,15 @@ class SemiSpace : public Space {
   // Updates Capacity and MaximumCommitted based on new capacity.
   void SetCapacity(int new_capacity);
 
+  // Allocates new shadow chunk for pages with indexes in the range
+  // [start_index, end_index).
+  // Returns false on allocation failure.
+  bool AllocateShadowChunksForPages(int start_index, int end_index);
+
+  // Frees shadow chunk for pages with indexes in the range
+  // [start_index, end_index).
+  void FreeShadowChunksForPages(int start_index, int end_index);
+
   NewSpacePage* anchor() { return &anchor_; }
 
   // The current and maximum capacity of the space.