Serializer: canonicalize cleared weak cells.

src/snapshot/serialize.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/v8.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/base/platform/platform.h"
 #include "src/bootstrapper.h"
@@ skipping 1074 matching lines @@
         const Heap::Reservation& reservation = reservations_[space];
         // Make sure the current chunk is indeed exhausted.
         CHECK_EQ(reservation[chunk_index].end, high_water_[space]);
         // Move to next reserved chunk.
         chunk_index = ++current_chunk_[space];
         CHECK_LT(chunk_index, reservation.length());
         high_water_[space] = reservation[chunk_index].start;
         break;
       }
 
+      case kClearedWeakCell: {
+        Object* cleared_weak_cell = isolate_->heap()->cleared_weak_cell();
+        UnalignedCopy(current++, &cleared_weak_cell);
+        break;
+      }
+
       case kSynchronize:
         // If we get here then that indicates that you have a mismatch between
         // the number of GC roots when serializing and deserializing.
         CHECK(false);
         break;
 
       case kNativesStringResource: {
         DCHECK(!isolate_->heap()->deserialization_complete());
         int index = source_.Get();
         Vector<const char> source_vector = Natives::GetScriptSource(index);
@@ skipping 350 matching lines @@
   } else {
     return chunk_index < completed_chunks_[space].length() &&
            reference.chunk_offset() < completed_chunks_[space][chunk_index];
   }
 }
 #endif  // DEBUG
 
 
 bool Serializer::SerializeKnownObject(HeapObject* obj, HowToCode how_to_code,
                                       WhereToPoint where_to_point, int skip) {
+  if (obj->IsWeakCell() && WeakCell::cast(obj)->cleared()) {
+    FlushSkip(skip);
+    sink_->Put(kClearedWeakCell, "ClearedWeakCell");
+    return true;
+  }
   if (how_to_code == kPlain && where_to_point == kStartOfObject) {
     // Encode a reference to a hot object by its index in the working set.
     int index = hot_objects_.Find(obj);
     if (index != HotObjectsList::kNotFound) {
       DCHECK(index >= 0 && index < kNumberOfHotObjects);
       if (FLAG_trace_serializer) {
         PrintF(" Encoding hot object %d:", index);
         obj->ShortPrint();
         PrintF("\n");
       }
@@ skipping 1116 matching lines @@
   DisallowHeapAllocation no_gc;
   SerializedCodeData* scd = new SerializedCodeData(cached_data);
   SanityCheckResult r = scd->SanityCheck(isolate, source);
   if (r == CHECK_SUCCESS) return scd;
   cached_data->Reject();
   source->GetIsolate()->counters()->code_cache_reject_reason()->AddSample(r);
   delete scd;
   return NULL;
 }
 } }  // namespace v8::internal