Convert some compiler passes to preserve valid def-use chains.

runtime/vm/flow_graph.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_FLOW_GRAPH_H_
 #define VM_FLOW_GRAPH_H_
 
 #include "vm/growable_array.h"
+#include "vm/intermediate_language.h"
 #include "vm/parser.h"
 
 namespace dart {
 
-class BlockEntryInstr;
-class ConstantInstr;
-class Definition;
 class FlowGraphBuilder;
-class GraphEntryInstr;
-class PhiInstr;
-class ReturnInstr;
 class ValueInliningContext;
 
 class BlockIterator : public ValueObject {
  public:
   explicit BlockIterator(const GrowableArray<BlockEntryInstr*>& block_order)
       : block_order_(block_order), current_(0) { }
 
   BlockIterator(const BlockIterator& other)
       : ValueObject(),
         block_order_(other.block_order_),
@@ skipping 80 matching lines @@
     return constant_null_;
   }
 
   intptr_t alloc_ssa_temp_index() { return current_ssa_temp_index_++; }
 
   intptr_t InstructionCount() const;
 
   ConstantInstr* AddConstantToInitialDefinitions(const Object& object);
   void AddToInitialDefinitions(Definition* defn);
 
+  void InsertBefore(Instruction* next,
+                    Instruction* instr,
+                    Environment* env,
+                    Definition::UseKind use_kind);
+  void InsertAfter(Instruction* prev,
+                   Instruction* instr,
+                   Environment* env,
+                   Definition::UseKind use_kind);
+
   // Operations on the flow graph.
   void ComputeSSA(intptr_t next_virtual_register_number,
                   GrowableArray<Definition*>* inlining_parameters);
   void ComputeUseLists();
 
   // Finds natural loops in the flow graph and attaches a list of loop
   // body blocks for each loop header.
   void ComputeLoops(GrowableArray<BlockEntryInstr*>* loop_headers);
 
   void RepairGraphAfterInlining();
@@ skipping 57 matching lines @@
   GrowableArray<BlockEntryInstr*> preorder_;
   GrowableArray<BlockEntryInstr*> postorder_;
   GrowableArray<BlockEntryInstr*> reverse_postorder_;
   bool invalid_dominator_tree_;
   ConstantInstr* constant_null_;
 };
 
 }  // namespace dart
 
 #endif  // VM_FLOW_GRAPH_H_