[turbofan] Initial version of ValueNumberingReducer.

src/compiler/value-numbering-reducer.h

+// Copyright 2014 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_VALUE_NUMBERING_REDUCER_H_
+#define V8_COMPILER_VALUE_NUMBERING_REDUCER_H_
+
+#include "src/compiler/graph-reducer.h"
+
+namespace v8 {
+namespace internal {
+namespace compiler {
+
+class ValueNumberingReducer FINAL : public Reducer {
+ public:
+  explicit ValueNumberingReducer(Zone* zone);
+  ~ValueNumberingReducer();
+
+  virtual Reduction Reduce(Node* node) OVERRIDE;
+
+ private:
+  Zone* zone() const { return zone_; }
+
+  // TODO(turbofan): We currently use separate chaining with linked lists here,
+  // we may want to replace that with a more sophisticated data structure at
+  // some point in the future.
+  class Entry;
+  Entry* buckets_[117u];
+  Zone* zone_;
+};
+
+}  // namespace compiler
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_COMPILER_VALUE_NUMBERING_REDUCER_H_