Use an allocation site scratchpad to speed up allocaton site processing during gc.

src/heap.h

 // Copyright 2012 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 2039 matching lines @@
   void MarkMapPointersAsEncoded(bool encoded) {
     ASSERT(!encoded);
     gc_safe_size_of_old_object_ = &GcSafeSizeOfOldObject;
   }
 
   // Code that should be run before and after each GC.  Includes some
   // reporting/verification activities when compiled with DEBUG set.
   void GarbageCollectionPrologue();
   void GarbageCollectionEpilogue();
 
+  // Pretenuring decisions are made based on feedback collected during new
+  // space evacuation. Note that between feedback collection and calling this
+  // method object in old space must not move.
+  void ProcessPretenuringFeedback();
+
   // Checks whether a global GC is necessary
   GarbageCollector SelectGarbageCollector(AllocationSpace space,
                                           const char** reason);
 
   // Performs garbage collection operation.
   // Returns whether there is a chance that another major GC could
   // collect more garbage.
   bool CollectGarbage(AllocationSpace space,
                       GarbageCollector collector,
                       const char* gc_reason,
@@ skipping 306 matching lines @@
 
   // If the --deopt_every_n_garbage_collections flag is set to a positive value,
   // this variable holds the number of garbage collections since the last
   // deoptimization triggered by garbage collection.
   int gcs_since_last_deopt_;
 
 #ifdef VERIFY_HEAP
   int no_weak_object_verification_scope_depth_;
 #endif
 
+
+  static const int kAllocationSiteScratchpadSize = 256;
+  int allocation_sites_scratchpad_length;
+  AllocationSite* allocation_sites_scratchpad[kAllocationSiteScratchpadSize];
+
   static const int kMaxMarkSweepsInIdleRound = 7;
   static const int kIdleScavengeThreshold = 5;
 
   // Shared state read by the scavenge collector and set by ScavengeObject.
   PromotionQueue promotion_queue_;
 
   // Flag is set when the heap has been configured.  The heap can be repeatedly
   // configured through the API until it is set up.
   bool configured_;
 
@@ skipping 684 matching lines @@
   DisallowHeapAllocation no_allocation;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_H_