Avoid creating duplicate entries for a value when merging HSimulates

src/hydrogen.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 139 matching lines @@
   ASSERT(ast_id.IsNone() ||
          ast_id == BailoutId::StubEntry() ||
          environment->closure()->shared()->VerifyBailoutId(ast_id));
 
   int push_count = environment->push_count();
   int pop_count = environment->pop_count();
 
   HSimulate* instr =
       new(zone()) HSimulate(ast_id, pop_count, zone(), removable);
   // Order of pushed values: newest (top of stack) first. This allows
-  // HSimulate::MergeInto() to easily append additional pushed values
+  // HSimulate::MergeWith() to easily append additional pushed values
   // that are older (from further down the stack).
   for (int i = 0; i < push_count; ++i) {
     instr->AddPushedValue(environment->ExpressionStackAt(i));
   }
   for (GrowableBitVector::Iterator it(environment->assigned_variables(),
                                       zone());
        !it.Done();
        it.Advance()) {
     int index = it.Current();
     instr->AddAssignedValue(index, environment->Lookup(index));
@@ skipping 12304 matching lines @@
     }
   }
 
 #ifdef DEBUG
   if (graph_ != NULL) graph_->Verify(false);  // No full verify.
   if (allocator_ != NULL) allocator_->Verify();
 #endif
 }
 
 } }  // namespace v8::internal