Add a simple dominator based redundancy elimination.

runtime/vm/flow_graph.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_FLOW_GRAPH_H_
 #define VM_FLOW_GRAPH_H_
 
 #include "vm/growable_array.h"
 #include "vm/parser.h"
 
@@ skipping 38 matching lines @@
     return postorder_;
   }
   const GrowableArray<BlockEntryInstr*>& reverse_postorder() const {
     return reverse_postorder_;
   }
 
   intptr_t max_virtual_register_number() const {
     return current_ssa_temp_index();
   }
 
+  GraphEntryInstr* graph_entry() const {
+    return graph_entry_;
+  }
+
   // Operations on the flow graph.
   void ComputeSSA();
 
   // TODO(zerny): Once the SSA is feature complete this should be removed.
   void Bailout(const char* reason) const;
 
  private:
   void DiscoverBlocks();
 
   // SSA transformation methods and fields.
@@ skipping 38 matching lines @@
   const intptr_t stack_local_count_;
   GraphEntryInstr* graph_entry_;
   GrowableArray<BlockEntryInstr*> preorder_;
   GrowableArray<BlockEntryInstr*> postorder_;
   GrowableArray<BlockEntryInstr*> reverse_postorder_;
 };
 
 }  // namespace dart
 
 #endif  // VM_FLOW_GRAPH_H_