Improve load forwarding:

runtime/vm/flow_graph_optimizer.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_OPTIMIZER_H_
 #define VM_FLOW_GRAPH_OPTIMIZER_H_
 
 #include "vm/intermediate_language.h"
 #include "vm/flow_graph.h"
 
 namespace dart {
 
 class CSEInstructionMap;
 template <typename T> class GrowableArray;
 class ParsedFunction;
 
 class FlowGraphOptimizer : public FlowGraphVisitor {
  public:
   FlowGraphOptimizer(FlowGraph* flow_graph,
-                     GrowableArray<Field*>* guarded_fields)
+                     GrowableArray<const Field*>* guarded_fields)
       : FlowGraphVisitor(flow_graph->reverse_postorder()),
         flow_graph_(flow_graph),
         guarded_fields_(guarded_fields) { }
   virtual ~FlowGraphOptimizer() {}
 
   FlowGraph* flow_graph() const { return flow_graph_; }
 
   // Use ICData to optimize, replace or eliminate instructions.
   void ApplyICData();
 
   // Use propagated class ids to optimize, replace or eliminate instructions.
   void ApplyClassIds();
 
   // Optimize (a << b) & c pattern: if c is a positive Smi or zero, then the
   // shift can be a truncating Smi shift-left and result is always Smi.
   void TryOptimizeLeftShiftWithBitAndPattern();
 
-  void Canonicalize();
+  // Returns true if any instructions were canonicalized away.
+  bool Canonicalize();
 
   void EliminateDeadPhis();
 
   void SelectRepresentations();
 
   void InferSmiRanges();
 
   virtual void VisitStaticCall(StaticCallInstr* instr);
   virtual void VisitInstanceCall(InstanceCallInstr* instr);
   virtual void VisitRelationalOp(RelationalOpInstr* instr);
@@ skipping 114 matching lines @@
   static bool CanStrictifyEqualityCompare(EqualityCompareInstr* call);
 
   template <typename T>
   bool StrictifyEqualityCompare(EqualityCompareInstr* compare,
                                 T current_instruction) const;
 
   void OptimizeLeftShiftBitAndSmiOp(Definition* bit_and_instr,
                                     Definition* left_instr,
                                     Definition* right_instr);
 
-  void AddToGuardedFields(Field* field);
+  void AddToGuardedFields(const Field& field);
 
   FlowGraph* flow_graph_;
-  GrowableArray<Field*>* guarded_fields_;
+  GrowableArray<const Field*>* guarded_fields_;
 
   DISALLOW_COPY_AND_ASSIGN(FlowGraphOptimizer);
 };
 
 
 // Loop invariant code motion.
 class LICM : public ValueObject {
  public:
   explicit LICM(FlowGraph* flow_graph);
 
@@ skipping 130 matching lines @@
 // platform.
 class IfConverter : public AllStatic {
  public:
   static void Simplify(FlowGraph* flow_graph);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_FLOW_GRAPH_OPTIMIZER_H_