Refactor Hydrogen environment liveness analysis into an HPhase.

src/hydrogen-environment-liveness.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 27 matching lines @@
 // Trims live ranges of environment slots by doing explicit liveness analysis.
 // Values in the environment are kept alive by every subsequent LInstruction
 // that is assigned an LEnvironment, which creates register pressure and
 // unnecessary spill slot moves. Therefore it is beneficial to trim the
 // live ranges of environment slots by zapping them with a constant after
 // the last lookup that refers to them.
 // Slots are identified by their index and only affected if whitelisted in
 // HOptimizedGraphBuilder::IsEligibleForEnvironmentLivenessAnalysis().
 class EnvironmentSlotLivenessAnalyzer {
  public:
-  explicit EnvironmentSlotLivenessAnalyzer(HGraph* graph);
+  EnvironmentSlotLivenessAnalyzer(HGraph* graph, Zone* phase_zone);
 
-  void AnalyzeAndTrim();
+  void Run();
 
  private:
   void ZapEnvironmentSlot(int index, HSimulate* simulate);
   void ZapEnvironmentSlotsInSuccessors(HBasicBlock* block, BitVector* live);
   void ZapEnvironmentSlotsForInstruction(HEnvironmentMarker* marker);
   void UpdateLivenessAtBlockEnd(HBasicBlock* block, BitVector* live);
   void UpdateLivenessAtInstruction(HInstruction* instr, BitVector* live);
 
-  Zone* zone() { return &zone_; }
+  Zone* phase_zone() { return phase_zone_; }
 
   HGraph* graph_;
-  // Use a dedicated Zone for this phase, with a ZoneScope to ensure it
-  // gets freed.
-  Zone zone_;
-  ZoneScope zone_scope_;
+  Zone* phase_zone_;
+  ZoneScope phase_zone_scope_;
 
   int block_count_;
 
   // Largest number of local variables in any environment in the graph
   // (including inlined environments).
   int maximum_environment_size_;
 
   // Per-block data. All these lists are indexed by block_id.
   ZoneList<BitVector*>* live_at_block_start_;
   ZoneList<HSimulate*>* first_simulate_;
   ZoneList<BitVector*>* first_simulate_invalid_for_index_;
 
   // List of all HEnvironmentMarker instructions for quick iteration/deletion.
   // It is populated during the first pass over the graph, controlled by
   // |collect_markers_|.
   ZoneList<HEnvironmentMarker*>* markers_;
   bool collect_markers_;
 
   // Keeps track of the last simulate seen, as well as the environment slots
   // for which a new live range has started since (so they must not be zapped
   // in that simulate when the end of another live range of theirs is found).
   HSimulate* last_simulate_;
   BitVector* went_live_since_last_simulate_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif /* V8_HYDROGEN_ENVIRONMENT_LIVENESS_H_ */