Avoid creating duplicate entries for a value when merging HSimulates

src/code-stubs-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 130 matching lines @@
     parameters_[i] = param;
   }
 
   HInstruction* stack_parameter_count;
   if (descriptor_->stack_parameter_count_ != NULL) {
     ASSERT(descriptor_->environment_length() == (param_count + 1));
     stack_parameter_count = new(zone) HParameter(param_count,
                                                  HParameter::REGISTER_PARAMETER,
                                                  Representation::Integer32());
     stack_parameter_count->set_type(HType::Smi());
-    // it's essential to bind this value to the environment in case of deopt
+    // It's essential to bind this value to the environment in case of deopt.
     AddInstruction(stack_parameter_count);
     start_environment->Bind(param_count, stack_parameter_count);
     arguments_length_ = stack_parameter_count;
   } else {
     ASSERT(descriptor_->environment_length() == param_count);
     stack_parameter_count = graph()->GetConstantMinus1();
     arguments_length_ = graph()->GetConstant0();
   }
 
   context_ = new(zone) HContext();
   AddInstruction(context_);
   start_environment->BindContext(context_);
 
   AddSimulate(BailoutId::StubEntry());
 
   NoObservableSideEffectsScope no_effects(this);
 
   HValue* return_value = BuildCodeStub();
 
   // We might have extra expressions to pop from the stack in addition to the
-  // arguments above
+  // arguments above.
   HInstruction* stack_pop_count = stack_parameter_count;
   if (descriptor_->function_mode_ == JS_FUNCTION_STUB_MODE) {
     if (!stack_parameter_count->IsConstant() &&
         descriptor_->hint_stack_parameter_count_ < 0) {
       HInstruction* amount = graph()->GetConstant1();
       stack_pop_count = AddInstruction(
           HAdd::New(zone, context_, stack_parameter_count, amount));
       stack_pop_count->ChangeRepresentation(Representation::Integer32());
       stack_pop_count->ClearFlag(HValue::kCanOverflow);
     } else {
@@ skipping 511 matching lines @@
       ? graph()->GetConstantSmi1()
       : graph()->GetConstantUndefined();
 }
 
 
 Handle<Code> CompareNilICStub::GenerateCode() {
   return DoGenerateCode(this);
 }
 
 } }  // namespace v8::internal