Forward white to grey transition only if slot is before the progress bar of a given object.

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 485 matching lines @@
     progress_bar_ = progress_bar;
   }
 
   void ResetProgressBar() {
     if (IsFlagSet(MemoryChunk::HAS_PROGRESS_BAR)) {
       set_progress_bar(0);
       ClearFlag(MemoryChunk::HAS_PROGRESS_BAR);
     }
   }
 
+  bool IsLeftOfProgressBar(Object** slot) {
+    ASSERT(reinterpret_cast<Address>(slot) > reinterpret_cast<Address>(this));
+    return reinterpret_cast<Address>(slot) - (reinterpret_cast<Address>(this) +

[Michael Starzinger, 2012/11/26 15:10:26]

Used the address() helper instead of "reinterpret_cast<Address>(this)".

Also if you pull out the cast of slot to Address the code will be easier to read
and the condition will fit into one line.

[Hannes Payer (out of office), 2012/11/26 16:14:35]

Done.

+        kObjectStartOffset) < progress_bar();
+  }
 
   static void IncrementLiveBytesFromGC(Address address, int by) {
     MemoryChunk::FromAddress(address)->IncrementLiveBytes(by);
   }
 
   static void IncrementLiveBytesFromMutator(Address address, int by);
 
   static const intptr_t kAlignment =
       (static_cast<uintptr_t>(1) << kPageSizeBits);
 
@@ skipping 2206 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_