Land the Fan (disabled)

src/compiler/phi-reducer.h

Index: src/compiler/phi-reducer.h
diff --git a/src/compiler/phi-reducer.h b/src/compiler/phi-reducer.h
new file mode 100644
index 0000000000000000000000000000000000000000..b6aa65e85119ccaa7149429aa19412497d29b9e2
--- /dev/null
+++ b/src/compiler/phi-reducer.h
@@ -0,0 +1,42 @@
+// 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/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 V8_FINAL : public Reducer {
+ public:
+  virtual Reduction Reduce(Node* node) V8_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;
+      }
+    }
+    ASSERT_NE(node, replacement);
+    return Replace(replacement);
+  }
+};
+}
+}
+}  // namespace v8::internal::compiler
+
+#endif  // V8_COMPILER_PHI_REDUCER_H_