Remove PhiReducer.

src/compiler/phi-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_PHI_REDUCER_H_
-#define V8_COMPILER_PHI_REDUCER_H_
-
-#include "src/compiler/generic-node-inl.h"
-#include "src/compiler/graph-reducer.h"
-
-namespace v8 {
-namespace internal {
-namespace compiler {
-
-// Replaces redundant phis if all the inputs are the same or the phi itself.
-class PhiReducer FINAL : public Reducer {
- public:
-  virtual Reduction Reduce(Node* node) OVERRIDE {
-    if (node->opcode() != IrOpcode::kPhi &&
-        node->opcode() != IrOpcode::kEffectPhi)
-      return NoChange();
-
-    int n = node->op()->InputCount();
-    if (n == 1) return Replace(node->InputAt(0));
-
-    Node* replacement = NULL;
-    Node::Inputs inputs = node->inputs();
-    for (InputIter it = inputs.begin(); n > 0; --n, ++it) {
-      Node* input = *it;
-      if (input != node && input != replacement) {
-        if (replacement != NULL) return NoChange();
-        replacement = input;
-      }
-    }
-    DCHECK_NE(node, replacement);
-    return Replace(replacement);
-  }
-};
-}
-}
-}  // namespace v8::internal::compiler
-
-#endif  // V8_COMPILER_PHI_REDUCER_H_