Initiate a dead code elimination pass in the optimizing compiler.

Change-Id: Ie9db5d8e2c2c30e34145a0f7d2386b8ec58cfc4e
diff --git a/compiler/optimizing/dead_code_elimination.h b/compiler/optimizing/dead_code_elimination.h
new file mode 100644
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+++ b/compiler/optimizing/dead_code_elimination.h
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+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ART_COMPILER_OPTIMIZING_DEAD_CODE_ELIMINATION_H_
+#define ART_COMPILER_OPTIMIZING_DEAD_CODE_ELIMINATION_H_
+
+#include "nodes.h"
+
+namespace art {
+
+/**
+ * Optimization pass performing dead code elimination (removal of
+ * unused variables/instructions) on the SSA form.
+ */
+class DeadCodeElimination : public ValueObject {
+ public:
+  explicit DeadCodeElimination(HGraph* graph)
+      : graph_(graph) {}
+
+  void Run();
+
+ private:
+  HGraph* const graph_;
+
+  DISALLOW_COPY_AND_ASSIGN(DeadCodeElimination);
+};
+
+}  // namespace art
+
+#endif  // ART_COMPILER_OPTIMIZING_DEAD_CODE_ELIMINATION_H_