Use a hashmap to lookup items in the partial snapshot cache when serializing.

src/serialize.h

 // 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.
 
 #ifndef V8_SERIALIZE_H_
 #define V8_SERIALIZE_H_
 
 #include "src/hashmap.h"
 #include "src/heap-profiler.h"
 #include "src/isolate.h"
@@ skipping 168 matching lines @@
     return kInvalidRootIndex;
   }
 
  private:
   HashMap* map_;
 
   DISALLOW_COPY_AND_ASSIGN(RootIndexMap);
 };
 
 
+class PartialCacheIndexMap : public AddressMapBase {
+ public:
+  PartialCacheIndexMap() : map_(HashMap::PointersMatch) {}
+
+  static const int kInvalidIndex = -1;
+
+  // Lookup object in the map. Return its index if found, or create
+  // a new entry with new_index as value, and return kInvalidIndex.
+  int LookupOrInsert(HeapObject* obj, int new_index) {
+    HashMap::Entry* entry = LookupEntry(&map_, obj, true);
+    if (entry->value != NULL) return GetValue(entry);
+    SetValue(entry, static_cast<uint32_t>(new_index));
+    return kInvalidIndex;
+  }
+
+ private:
+  HashMap map_;
+
+  DISALLOW_COPY_AND_ASSIGN(PartialCacheIndexMap);
+};
+
+
 class BackReference {
  public:
   explicit BackReference(uint32_t bitfield) : bitfield_(bitfield) {}
 
   BackReference() : bitfield_(kInvalidValue) {}
 
   static BackReference SourceReference() { return BackReference(kSourceValue); }
 
   static BackReference GlobalProxyReference() {
     return BackReference(kGlobalProxyValue);
@@ skipping 596 matching lines @@
            o->IsScopeInfo() ||
            o->map() ==
                startup_serializer_->isolate()->heap()->fixed_cow_array_map();
   }
 
   void SerializeOutdatedContextsAsFixedArray();
 
   Serializer* startup_serializer_;
   List<BackReference> outdated_contexts_;
   Object* global_object_;
+  PartialCacheIndexMap partial_cache_index_map_;
   DISALLOW_COPY_AND_ASSIGN(PartialSerializer);
 };
 
 
 class StartupSerializer : public Serializer {
  public:
   StartupSerializer(Isolate* isolate, SnapshotByteSink* sink)
       : Serializer(isolate, sink), root_index_wave_front_(0) {
     // Clear the cache of objects used by the partial snapshot.  After the
     // strong roots have been serialized we can create a partial snapshot
@@ skipping 178 matching lines @@
       kNumInternalizedStringsOffset + kInt32Size;
   static const int kNumCodeStubKeysOffset = kNumReservationsOffset + kInt32Size;
   static const int kPayloadLengthOffset = kNumCodeStubKeysOffset + kInt32Size;
   static const int kChecksum1Offset = kPayloadLengthOffset + kInt32Size;
   static const int kChecksum2Offset = kChecksum1Offset + kInt32Size;
   static const int kHeaderSize = kChecksum2Offset + kInt32Size;
 };
 } }  // namespace v8::internal
 
 #endif  // V8_SERIALIZE_H_