Index: src/heap/mark-compact-inl.h |
diff --git a/src/heap/mark-compact-inl.h b/src/heap/mark-compact-inl.h |
index 0bf88ee888bc9be61209ea3f9c83f5c7ec871f22..7ead42150b698f7b44fb198738fbe854066c56d0 100644 |
--- a/src/heap/mark-compact-inl.h |
+++ b/src/heap/mark-compact-inl.h |
@@ -148,7 +148,16 @@ HeapObject* LiveObjectIterator<T>::Next() { |
second_bit_index = 0x1; |
// The overlapping case; there has to exist a cell after the current |
// cell. |
- DCHECK(!it_.Done()); |
+ // However, if there is a black area at the end of the page, and the |
+ // last word is a one word filler, we are not allowed to advance. In |
+ // that case we can return immediately. |
+ if (it_.Done()) { |
+ DCHECK(HeapObject::FromAddress(addr)->map() == |
+ HeapObject::FromAddress(addr) |
+ ->GetHeap() |
+ ->one_pointer_filler_map()); |
+ return nullptr; |
+ } |
it_.Advance(); |
cell_base_ = it_.CurrentCellBase(); |
current_cell_ = *it_.CurrentCell(); |
@@ -160,20 +169,26 @@ HeapObject* LiveObjectIterator<T>::Next() { |
// object ends. |
HeapObject* black_object = HeapObject::FromAddress(addr); |
Address end = addr + black_object->Size() - kPointerSize; |
- DCHECK_EQ(chunk_, MemoryChunk::FromAddress(end)); |
- uint32_t end_mark_bit_index = chunk_->AddressToMarkbitIndex(end); |
- unsigned int end_cell_index = |
- end_mark_bit_index >> Bitmap::kBitsPerCellLog2; |
- MarkBit::CellType end_index_mask = |
- 1u << Bitmap::IndexInCell(end_mark_bit_index); |
- if (it_.Advance(end_cell_index)) { |
- cell_base_ = it_.CurrentCellBase(); |
- current_cell_ = *it_.CurrentCell(); |
+ // One word filler objects do not borrow the second mark bit. We have |
+ // to jump over the advancing and clearing part. |
+ // Note that we know that we are at a one word filler when |
+ // object_start + object_size - kPointerSize == object_start. |
+ if (addr != end) { |
+ DCHECK_EQ(chunk_, MemoryChunk::FromAddress(end)); |
+ uint32_t end_mark_bit_index = chunk_->AddressToMarkbitIndex(end); |
+ unsigned int end_cell_index = |
+ end_mark_bit_index >> Bitmap::kBitsPerCellLog2; |
+ MarkBit::CellType end_index_mask = |
+ 1u << Bitmap::IndexInCell(end_mark_bit_index); |
+ if (it_.Advance(end_cell_index)) { |
+ cell_base_ = it_.CurrentCellBase(); |
+ current_cell_ = *it_.CurrentCell(); |
+ } |
+ |
+ // Clear all bits in current_cell, including the end index. |
+ current_cell_ &= ~(end_index_mask + end_index_mask - 1); |
} |
- // Clear all bits in current_cell, including the end index. |
- current_cell_ &= ~(end_index_mask + end_index_mask - 1); |
- |
if (T == kBlackObjects || T == kAllLiveObjects) { |
object = black_object; |
} |