Optimistically hoist SmiCheck through phi when the only value of unknown type coming into the phi i…

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"
 
@@ skipping 106 matching lines @@
   const ParsedFunction& parsed_function_;
   bool still_changing_;
   DISALLOW_COPY_AND_ASSIGN(FlowGraphTypePropagator);
 };
 
 
 // Loop invariant code motion.
 class LICM : public AllStatic {
  public:
   static void Optimize(FlowGraph* flow_graph);
+
+ private:
+  static void Hoist(ForwardInstructionIterator* it,
+                    BlockEntryInstr* pre_header,
+                    Definition* current);
+
+  static void TryHoistCheckSmiThroughPhi(ForwardInstructionIterator* it,
+                                         BlockEntryInstr* header,
+                                         BlockEntryInstr* pre_header,
+                                         Definition* current);
 };
 
 
 // A simple common subexpression elimination based
 // on the dominator tree.
 class DominatorBasedCSE : public AllStatic {
  public:
   static void Optimize(BlockEntryInstr* graph_entry);
 
  private:
   static void OptimizeRecursive(
       BlockEntryInstr* entry,
       DirectChainedHashMap<Definition*>* map);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_FLOW_GRAPH_OPTIMIZER_H_