Disable short-circuiting of cons-strings when compaction is pending.

src/heap.cc

 // 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 1644 matching lines @@
   } else {
     if (!logging_and_profiling) {
       scavenging_visitors_table_.CopyFrom(
           ScavengingVisitor<TRANSFER_MARKS,
                             LOGGING_AND_PROFILING_DISABLED>::GetTable());
     } else {
       scavenging_visitors_table_.CopyFrom(
           ScavengingVisitor<TRANSFER_MARKS,
                             LOGGING_AND_PROFILING_ENABLED>::GetTable());
     }
+
+    if (incremental_marking()->IsCompacting()) {
+      // When compacting forbid short-circuiting of cons-strings.
+      // Scavenging code relies on the fact that new space object
+      // can't be evacuated into evacuation candidate but
+      // short-circuiting violates this assumption.
+      scavenging_visitors_table_.Register(
+          StaticVisitorBase::kVisitShortcutCandidate,
+          scavenging_visitors_table_.GetVisitorById(
+              StaticVisitorBase::kVisitConsString));
+    }
   }
 }
 
 
 void Heap::ScavengeObjectSlow(HeapObject** p, HeapObject* object) {
   ASSERT(HEAP->InFromSpace(object));
   MapWord first_word = object->map_word();
   ASSERT(!first_word.IsForwardingAddress());
   Map* map = first_word.ToMap();
   map->GetHeap()->DoScavengeObject(map, p, object);
@@ skipping 4718 matching lines @@
   isolate_->heap()->store_buffer()->Compact();
   isolate_->heap()->store_buffer()->Filter(MemoryChunk::ABOUT_TO_BE_FREED);
   for (chunk = chunks_queued_for_free_; chunk != NULL; chunk = next) {
     next = chunk->next_chunk();
     isolate_->memory_allocator()->Free(chunk);
   }
   chunks_queued_for_free_ = NULL;
 }
 
 } }  // namespace v8::internal