[turbofan] Make sure Operator is really immutable.

src/compiler/operator.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_COMPILER_OPERATOR_H_
 #define V8_COMPILER_OPERATOR_H_
 
 #include "src/base/flags.h"
 #include "src/ostreams.h"
 #include "src/unique.h"
@@ skipping 251 matching lines @@
 
  private:
   int input_count_;
   int output_count_;
   T parameter_;
 };
 
 // Type definitions for operators with specific types of parameters.
 typedef Operator1<PrintableUnique<Name> > NameOperator;
 
+
+// Helper to extract parameters from Operator1<*> operator.
+template <typename T>
+static inline T OpParameter(const Operator* op) {
+  return reinterpret_cast<const Operator1<T>*>(op)->parameter();
+}
+
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_OPERATOR_H_