Implement simple dead store elimination.

runtime/vm/intermediate_language.h

 // Copyright (c) 2013, 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_INTERMEDIATE_LANGUAGE_H_
 #define VM_INTERMEDIATE_LANGUAGE_H_
 
 #include "vm/allocation.h"
 #include "vm/ast.h"
 #include "vm/growable_array.h"
@@ skipping 1455 matching lines @@
     ASSERT(block_entry_->previous() == NULL);
   }
 
   void Advance() {
     ASSERT(!Done());
     current_ = current_->previous();
   }
 
   bool Done() const { return current_ == block_entry_; }
 
+  void RemoveCurrentFromGraph();
+
   Instruction* Current() const { return current_; }
 
  private:
   BlockEntryInstr* block_entry_;
   Instruction* current_;
 };
 
 
 class GraphEntryInstr : public BlockEntryInstr {
  public:
@@ skipping 2265 matching lines @@
 
   void set_is_initialization(bool value) { is_initialization_ = value; }
 
   enum {
     kInstancePos = 0,
     kValuePos = 1
   };
 
   Value* instance() const { return inputs_[kInstancePos]; }
   Value* value() const { return inputs_[kValuePos]; }
+  bool is_initialization() const { return is_initialization_; }
   virtual intptr_t token_pos() const { return token_pos_; }
 
   virtual CompileType* ComputeInitialType() const;
 
   const Field& field() const { return field_; }
   intptr_t offset_in_bytes() const { return offset_in_bytes_; }
 
   bool ShouldEmitStoreBarrier() const {
     return value()->NeedsStoreBuffer()
         && (emit_store_barrier_ == kEmitStoreBarrier);
@@ skipping 4182 matching lines @@
   ForwardInstructionIterator* current_iterator_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FlowGraphVisitor);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_INTERMEDIATE_LANGUAGE_H_