[heap] Explicitly clear mark bits when writing filler for left and right trimming.

src/heap/heap.cc

 // Copyright 2012 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/heap.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/ast/context-slot-cache.h"
 #include "src/base/bits.h"
@@ skipping 1151 matching lines @@
         for (int i = 0; i < num_maps; i++) {
           // The deserializer will update the skip list.
           AllocationResult allocation = map_space()->AllocateRawUnaligned(
               Map::kSize, PagedSpace::IGNORE_SKIP_LIST);
           HeapObject* free_space = nullptr;
           if (allocation.To(&free_space)) {
             // Mark with a free list node, in case we have a GC before
             // deserializing.
             Address free_space_address = free_space->address();
             CreateFillerObjectAt(free_space_address, Map::kSize,
-                                 ClearRecordedSlots::kNo, ClearBlackArea::kNo);
+                                 ClearRecordedSlots::kNo);
             maps->Add(free_space_address);
           } else {
             perform_gc = true;
             break;
           }
         }
       } else if (space == LO_SPACE) {
         // Just check that we can allocate during deserialization.
         DCHECK_EQ(1, reservation->length());
         perform_gc = !CanExpandOldGeneration(reservation->at(0).size);
@@ skipping 10 matching lines @@
             // The deserializer will update the skip list.
             allocation = paged_space(space)->AllocateRawUnaligned(
                 size, PagedSpace::IGNORE_SKIP_LIST);
           }
           HeapObject* free_space = nullptr;
           if (allocation.To(&free_space)) {
             // Mark with a free list node, in case we have a GC before
             // deserializing.
             Address free_space_address = free_space->address();
             CreateFillerObjectAt(free_space_address, size,
-                                 ClearRecordedSlots::kNo, ClearBlackArea::kNo);
+                                 ClearRecordedSlots::kNo);
             DCHECK(space < SerializerDeserializer::kNumberOfPreallocatedSpaces);
             chunk.start = free_space_address;
             chunk.end = free_space_address + size;
           } else {
             perform_gc = true;
             break;
           }
         }
       }
       if (perform_gc) {
@@ skipping 879 matching lines @@
   HeapObject* obj = nullptr;
   {
     AllocationAlignment align = double_align ? kDoubleAligned : kWordAligned;
     AllocationResult allocation = AllocateRaw(size, space, align);
     if (!allocation.To(&obj)) return allocation;
   }
 #ifdef DEBUG
   MemoryChunk* chunk = MemoryChunk::FromAddress(obj->address());
   DCHECK(chunk->owner()->identity() == space);
 #endif
-  CreateFillerObjectAt(obj->address(), size, ClearRecordedSlots::kNo,
-                       ClearBlackArea::kNo);
+  CreateFillerObjectAt(obj->address(), size, ClearRecordedSlots::kNo);
   return obj;
 }
 
 
 const Heap::StringTypeTable Heap::string_type_table[] = {
 #define STRING_TYPE_ELEMENT(type, size, name, camel_name) \
   { type, size, k##camel_name##MapRootIndex }             \
   ,
     STRING_TYPE_LIST(STRING_TYPE_ELEMENT)
 #undef STRING_TYPE_ELEMENT
@@ skipping 941 matching lines @@
   instance->set_osr_loop_nesting_level(0);
   instance->set_bytecode_age(BytecodeArray::kNoAgeBytecodeAge);
   instance->set_constant_pool(constant_pool);
   instance->set_handler_table(empty_fixed_array());
   instance->set_source_position_table(empty_byte_array());
   CopyBytes(instance->GetFirstBytecodeAddress(), raw_bytecodes, length);
 
   return result;
 }
 
-void Heap::CreateFillerObjectAt(Address addr, int size, ClearRecordedSlots mode,
-                                ClearBlackArea black_area_mode) {
+void Heap::CreateFillerObjectAt(Address addr, int size,
+                                ClearRecordedSlots mode) {
   if (size == 0) return;
   HeapObject* filler = HeapObject::FromAddress(addr);
   if (size == kPointerSize) {
     filler->set_map_no_write_barrier(
         reinterpret_cast<Map*>(root(kOnePointerFillerMapRootIndex)));
   } else if (size == 2 * kPointerSize) {
     filler->set_map_no_write_barrier(
         reinterpret_cast<Map*>(root(kTwoPointerFillerMapRootIndex)));
   } else {
     DCHECK_GT(size, 2 * kPointerSize);
     filler->set_map_no_write_barrier(
         reinterpret_cast<Map*>(root(kFreeSpaceMapRootIndex)));
     FreeSpace::cast(filler)->nobarrier_set_size(size);
   }
   if (mode == ClearRecordedSlots::kYes) {
     ClearRecordedSlotRange(addr, addr + size);
   }
 
-  // If the location where the filler is created is within a black area we have
-  // to clear the mark bits of the filler space.
-  if (black_area_mode == ClearBlackArea::kYes &&
-      incremental_marking()->black_allocation() &&
-      Marking::IsBlackOrGrey(ObjectMarking::MarkBitFrom(addr))) {
-    Page* page = Page::FromAddress(addr);
-    page->markbits()->ClearRange(page->AddressToMarkbitIndex(addr),
-                                 page->AddressToMarkbitIndex(addr + size));
-  }
-
   // At this point, we may be deserializing the heap from a snapshot, and
   // none of the maps have been created yet and are NULL.
   DCHECK((filler->map() == NULL && !deserialization_complete_) ||
          filler->map()->IsMap());
 }
 
 
 bool Heap::CanMoveObjectStart(HeapObject* object) {
   if (!FLAG_move_object_start) return false;
 
@@ skipping 54 matching lines @@
   // a black area.
   if (!incremental_marking()->black_allocation() ||
       !Marking::IsBlack(ObjectMarking::MarkBitFrom(new_start))) {
     IncrementalMarking::TransferMark(this, old_start, new_start);
   }
 
   // Technically in new space this write might be omitted (except for
   // debug mode which iterates through the heap), but to play safer
   // we still do it.
   CreateFillerObjectAt(old_start, bytes_to_trim, ClearRecordedSlots::kYes);
+
+  // Clear the mark bits of the black area that belongs now to the filler.
+  // This is an optimization. The sweeper will release black fillers anyway.
+  if (incremental_marking()->black_allocation() &&
+      Marking::IsBlackOrGrey(ObjectMarking::MarkBitFrom(old_start))) {
+    Page* page = Page::FromAddress(old_start);
+    page->markbits()->ClearRange(
+        page->AddressToMarkbitIndex(old_start),
+        page->AddressToMarkbitIndex(old_start + bytes_to_trim));
+  }
+
   // Initialize header of the trimmed array. Since left trimming is only
   // performed on pages which are not concurrently swept creating a filler
   // object does not require synchronization.
   DCHECK(CanMoveObjectStart(object));
   Object** former_start = HeapObject::RawField(object, 0);
   int new_start_index = elements_to_trim * (element_size / kPointerSize);
   former_start[new_start_index] = map;
   former_start[new_start_index + 1] = Smi::FromInt(len - elements_to_trim);
 
   FixedArrayBase* new_object =
@@ skipping 51 matching lines @@
   // Technically in new space this write might be omitted (except for
   // debug mode which iterates through the heap), but to play safer
   // we still do it.
   // We do not create a filler for objects in large object space.
   // TODO(hpayer): We should shrink the large object page if the size
   // of the object changed significantly.
   if (!lo_space()->Contains(object)) {
     CreateFillerObjectAt(new_end, bytes_to_trim, ClearRecordedSlots::kYes);
   }
 
+  // Clear the mark bits of the black area that belongs now to the filler.
+  // This is an optimization. The sweeper will release black fillers anyway.
+  if (incremental_marking()->black_allocation() &&
+      Marking::IsBlackOrGrey(ObjectMarking::MarkBitFrom(new_end))) {
+    Page* page = Page::FromAddress(new_end);
+    page->markbits()->ClearRange(
+        page->AddressToMarkbitIndex(new_end),
+        page->AddressToMarkbitIndex(new_end + bytes_to_trim));
+  }
+
   // Initialize header of the trimmed array. We are storing the new length
   // using release store after creating a filler for the left-over space to
   // avoid races with the sweeper thread.
   object->synchronized_set_length(len - elements_to_trim);
 
   // Maintain consistency of live bytes during incremental marking
   AdjustLiveBytes(object, -bytes_to_trim);
 
   // Notify the heap profiler of change in object layout. The array may not be
   // moved during GC, and size has to be adjusted nevertheless.
@@ skipping 3239 matching lines @@
 }
 
 
 // static
 int Heap::GetStaticVisitorIdForMap(Map* map) {
   return StaticVisitorBase::GetVisitorId(map);
 }
 
 }  // namespace internal
 }  // namespace v8