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

src/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 1505 matching lines @@
     // Sentinel is the undefined object, which is a root so it will not normally
     // be found in the cache.
     if (cache->at(i)->IsUndefined()) break;
   }
 }
 
 
 int PartialSerializer::PartialSnapshotCacheIndex(HeapObject* heap_object) {
   Isolate* isolate = this->isolate();
   List<Object*>* cache = isolate->partial_snapshot_cache();
-  for (int i = 0; i < cache->length(); ++i) {
-    Object* entry = cache->at(i);
-    if (entry == heap_object) return i;
+  int new_index = cache->length();
+
+  int index = partial_cache_index_map_.LookupOrInsert(heap_object, new_index);
+  if (index == PartialCacheIndexMap::kInvalidIndex) {
+    // We didn't find the object in the cache.  So we add it to the cache and
+    // then visit the pointer so that it becomes part of the startup snapshot
+    // and we can refer to it from the partial snapshot.
+    cache->Add(heap_object);
+    startup_serializer_->VisitPointer(reinterpret_cast<Object**>(&heap_object));
+    // We don't recurse from the startup snapshot generator into the partial
+    // snapshot generator.
+    return new_index;
   }
-
-  // We didn't find the object in the cache.  So we add it to the cache and
-  // then visit the pointer so that it becomes part of the startup snapshot
-  // and we can refer to it from the partial snapshot.
-  cache->Add(heap_object);
-  startup_serializer_->VisitPointer(reinterpret_cast<Object**>(&heap_object));
-  // We don't recurse from the startup snapshot generator into the partial
-  // snapshot generator.
-  return cache->length() - 1;
+  return index;
 }
 
 
 #ifdef DEBUG
 bool Serializer::BackReferenceIsAlreadyAllocated(BackReference reference) {
   DCHECK(reference.is_valid());
   DCHECK(!reference.is_source());
   DCHECK(!reference.is_global_proxy());
   AllocationSpace space = reference.space();
   int chunk_index = reference.chunk_index();
@@ skipping 1114 matching lines @@
   DisallowHeapAllocation no_gc;
   SerializedCodeData* scd = new SerializedCodeData(cached_data);
   SanityCheckResult r = scd->SanityCheck(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