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

src/mark-compact.cc

 // 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 3343 matching lines @@
 
 void MarkCompactCollector::EvacuateNewSpaceAndCandidates() {
   Heap::RelocationLock relocation_lock(heap());
 
   bool code_slots_filtering_required;
   { GCTracer::Scope gc_scope(tracer_, GCTracer::Scope::MC_SWEEP_NEWSPACE);
     code_slots_filtering_required = MarkInvalidatedCode();
     EvacuateNewSpace();
   }
 
+  // We have to travers our allocation sites scratchpad which contains raw
+  // pointers before we move objects. During new space evacauation we
+  // gathered pretenuring statistics. The found allocation sites may not be
+  // valid after compacting old space.
+  heap()->ProcessPretenuringFeedback();
+
+
   { GCTracer::Scope gc_scope(tracer_, GCTracer::Scope::MC_EVACUATE_PAGES);
     EvacuatePages();
   }
 
   // Second pass: find pointers to new space and update them.
   PointersUpdatingVisitor updating_visitor(heap());
 
   { GCTracer::Scope gc_scope(tracer_,
                              GCTracer::Scope::MC_UPDATE_NEW_TO_NEW_POINTERS);
     // Update pointers in to space.
@@ skipping 987 matching lines @@
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 
 
 } }  // namespace v8::internal