[heap] Provide ObjectMarking with marking transitions

src/heap/spaces.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/heap/spaces.h"
 
 #include <utility>
 
 #include "src/base/bits.h"
 #include "src/base/platform/platform.h"
@@ skipping 2972 matching lines @@
     reinterpret_cast<Object**>(object->address())[0] =
         heap()->fixed_array_map();
     reinterpret_cast<Object**>(object->address())[1] = Smi::kZero;
   }
 
   heap()->StartIncrementalMarkingIfAllocationLimitIsReached(Heap::kNoGCFlags,
                                                             kNoGCCallbackFlags);
   AllocationStep(object->address(), object_size);
 
   if (heap()->incremental_marking()->black_allocation()) {
-    Marking::MarkBlack(ObjectMarking::MarkBitFrom(object));
+    // We cannot use ObjectMarking here as the object still lacks a size.

[Hannes Payer (out of office), 2017/01/18 14:43:35]

This one is really unfortunate. However, we do not need the live byte count for
large objects because we can always check the liveness of the LO and return its
size.

[Michael Lippautz, 2017/01/18 15:58:07]

Acknowledged.

+    Marking::WhiteToBlack(ObjectMarking::MarkBitFrom(object));
     MemoryChunk::IncrementLiveBytes(object, object_size);
   }
   return object;
 }
 
 
 size_t LargeObjectSpace::CommittedPhysicalMemory() {
   // On a platform that provides lazy committing of memory, we over-account
   // the actually committed memory. There is no easy way right now to support
   // precise accounting of committed memory in large object space.
@@ skipping 28 matching lines @@
     }
   }
   return NULL;
 }
 
 
 void LargeObjectSpace::ClearMarkingStateOfLiveObjects() {
   LargePage* current = first_page_;
   while (current != NULL) {
     HeapObject* object = current->GetObject();
-    MarkBit mark_bit = ObjectMarking::MarkBitFrom(object);
-    DCHECK(Marking::IsBlack(mark_bit));
-    Marking::BlackToWhite(mark_bit);
+    DCHECK(Marking::IsBlack(ObjectMarking::MarkBitFrom(object)));
+    ObjectMarking::BlackToWhite(object);
     Page::FromAddress(object->address())->ResetProgressBar();
     Page::FromAddress(object->address())->ResetLiveBytes();
     current = current->next_page();
   }
 }
 
 void LargeObjectSpace::InsertChunkMapEntries(LargePage* page) {
   // Register all MemoryChunk::kAlignment-aligned chunks covered by
   // this large page in the chunk map.
   uintptr_t start = reinterpret_cast<uintptr_t>(page) / MemoryChunk::kAlignment;
@@ skipping 174 matching lines @@
     object->ShortPrint();
     PrintF("\n");
   }
   printf(" --------------------------------------\n");
   printf(" Marked: %x, LiveCount: %x\n", mark_size, LiveBytes());
 }
 
 #endif  // DEBUG
 }  // namespace internal
 }  // namespace v8