To fully support hydrogen code stubs which accept a variable number of arguments,

src/code-stubs.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 252 matching lines @@
   CodeStubInterfaceDescriptor()
       : register_param_count_(-1),
         stack_parameter_count_(NULL),
         extra_expression_stack_count_(0),
         register_params_(NULL) { }
   int register_param_count_;
   const Register* stack_parameter_count_;
   int extra_expression_stack_count_;
   Register* register_params_;
   Address deoptimization_handler_;
+
+  int environment_length() const {
+    if (stack_parameter_count_ != NULL) {
+      return register_param_count_ + 1;
+    }
+    return register_param_count_;
+  }
 };
 
 
 class HydrogenCodeStub : public CodeStub {
  public:
   // Retrieve the code for the stub. Generate the code if needed.
   virtual Handle<Code> GenerateCode() = 0;
 
   virtual int GetCodeKind() { return Code::COMPILED_STUB; }
 
@@ skipping 1329 matching lines @@
 
   // The current function entry hook.
   static FunctionEntryHook entry_hook_;
 
   DISALLOW_COPY_AND_ASSIGN(ProfileEntryHookStub);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_CODE_STUBS_H_