Mark phi as producing a smi value if it is dominated by SmiChecks over its operands.

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 63 matching lines @@
   }
 
   // Iterators.
   BlockIterator reverse_postorder_iterator() const {
     return BlockIterator(reverse_postorder());
   }
   BlockIterator postorder_iterator() const {
     return BlockIterator(postorder());
   }
 
+  intptr_t current_ssa_temp_index() const { return current_ssa_temp_index_; }
+
   intptr_t max_virtual_register_number() const {
     return current_ssa_temp_index();
   }
 
   GraphEntryInstr* graph_entry() const {
     return graph_entry_;
   }
 
   ZoneGrowableArray<ReturnInstr*>* exits() const { return exits_; }
   void set_exits(ZoneGrowableArray<ReturnInstr*>* exits) { exits_ = exits; }
@@ skipping 40 matching lines @@
       GrowableArray<Definition*>* env,
       GrowableArray<PhiInstr*>* live_phis);
 
   void InsertPhis(
       const GrowableArray<BlockEntryInstr*>& preorder,
       const GrowableArray<BitVector*>& assigned_vars,
       const GrowableArray<BitVector*>& dom_frontier);
 
   void MarkLivePhis(GrowableArray<PhiInstr*>* live_phis);
 
-  intptr_t current_ssa_temp_index() const { return current_ssa_temp_index_; }
-
   // DiscoverBlocks computes parent_ and assigned_vars_ which are then used
   // if/when computing SSA.
   GrowableArray<intptr_t> parent_;
   GrowableArray<BitVector*> assigned_vars_;
 
   intptr_t current_ssa_temp_index_;
 
   // Flow graph fields.
   const ParsedFunction& parsed_function_;
   const intptr_t num_copied_params_;
   const intptr_t num_non_copied_params_;
   const intptr_t num_stack_locals_;
   GraphEntryInstr* graph_entry_;
   GrowableArray<BlockEntryInstr*> preorder_;
   GrowableArray<BlockEntryInstr*> postorder_;
   GrowableArray<BlockEntryInstr*> reverse_postorder_;
   ZoneGrowableArray<ReturnInstr*>* exits_;
 };
 
 }  // namespace dart
 
 #endif  // VM_FLOW_GRAPH_H_