Add heuristic for flattening strings before comparing them.

src/heap.cc

 // Copyright 2009 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 96 matching lines @@
 // Will be 4 * reserved_semispace_size_ to ensure that young
 // generation can be aligned to its size.
 int Heap::survived_since_last_expansion_ = 0;
 int Heap::external_allocation_limit_ = 0;
 
 Heap::HeapState Heap::gc_state_ = NOT_IN_GC;
 
 int Heap::mc_count_ = 0;
 int Heap::gc_count_ = 0;
 
+int Heap::unflattended_strings_length_ = 0;
+
 int Heap::always_allocate_scope_depth_ = 0;
 int Heap::linear_allocation_scope_depth_ = 0;
 int Heap::contexts_disposed_ = 0;
 
 #ifdef DEBUG
 bool Heap::allocation_allowed_ = true;
 
 int Heap::allocation_timeout_ = 0;
 bool Heap::disallow_allocation_failure_ = false;
 #endif  // DEBUG
@@ skipping 168 matching lines @@
 #elif defined(ENABLE_LOGGING_AND_PROFILING)
   if (FLAG_log_gc) new_space_.ReportStatistics();
 #endif
 }
 #endif  // defined(DEBUG) || defined(ENABLE_LOGGING_AND_PROFILING)
 
 
 void Heap::GarbageCollectionPrologue() {
   TranscendentalCache::Clear();
   gc_count_++;
+  unflattended_strings_length_ = 0;
 #ifdef DEBUG
   ASSERT(allocation_allowed_ && gc_state_ == NOT_IN_GC);
   allow_allocation(false);
 
   if (FLAG_verify_heap) {
     Verify();
   }
 
   if (FLAG_gc_verbose) Print();
 
@@ skipping 3936 matching lines @@
 void ExternalStringTable::TearDown() {
   new_space_strings_.Free();
   old_space_strings_.Free();
 }
 
 
 List<Object*> ExternalStringTable::new_space_strings_;
 List<Object*> ExternalStringTable::old_space_strings_;
 
 } }  // namespace v8::internal