Line data    Source code

       1             : // Copyright 2013 the V8 project authors. All rights reserved.
       2             : // Use of this source code is governed by a BSD-style license that can be
       3             : // found in the LICENSE file.
       4             : 
       5             : #ifndef V8_CRANKSHAFT_HYDROGEN_ENVIRONMENT_LIVENESS_H_
       6             : #define V8_CRANKSHAFT_HYDROGEN_ENVIRONMENT_LIVENESS_H_
       7             : 
       8             : #include "src/crankshaft/hydrogen.h"
       9             : 
      10             : namespace v8 {
      11             : namespace internal {
      12             : 
      13             : 
      14             : // Trims live ranges of environment slots by doing explicit liveness analysis.
      15             : // Values in the environment are kept alive by every subsequent LInstruction
      16             : // that is assigned an LEnvironment, which creates register pressure and
      17             : // unnecessary spill slot moves. Therefore it is beneficial to trim the
      18             : // live ranges of environment slots by zapping them with a constant after
      19             : // the last lookup that refers to them.
      20             : // Slots are identified by their index and only affected if whitelisted in
      21             : // HOptimizedGraphBuilder::IsEligibleForEnvironmentLivenessAnalysis().
      22      280035 : class HEnvironmentLivenessAnalysisPhase : public HPhase {
      23             :  public:
      24             :   explicit HEnvironmentLivenessAnalysisPhase(HGraph* graph);
      25             : 
      26             :   void Run();
      27             : 
      28             :  private:
      29             :   void ZapEnvironmentSlot(int index, HSimulate* simulate);
      30             :   void ZapEnvironmentSlotsInSuccessors(HBasicBlock* block, BitVector* live);
      31             :   void ZapEnvironmentSlotsForInstruction(HEnvironmentMarker* marker);
      32             :   void UpdateLivenessAtBlockEnd(HBasicBlock* block, BitVector* live);
      33             :   void UpdateLivenessAtInstruction(HInstruction* instr, BitVector* live);
      34             : #ifdef DEBUG
      35             :   bool VerifyClosures(Handle<JSFunction> a, Handle<JSFunction> b);
      36             : #endif
      37             : 
      38             :   int block_count_;
      39             : 
      40             :   // Largest number of local variables in any environment in the graph
      41             :   // (including inlined environments).
      42             :   int maximum_environment_size_;
      43             : 
      44             :   // Per-block data. All these lists are indexed by block_id.
      45             :   ZoneList<BitVector*> live_at_block_start_;
      46             :   ZoneList<HSimulate*> first_simulate_;
      47             :   ZoneList<BitVector*> first_simulate_invalid_for_index_;
      48             : 
      49             :   // List of all HEnvironmentMarker instructions for quick iteration/deletion.
      50             :   // It is populated during the first pass over the graph, controlled by
      51             :   // |collect_markers_|.
      52             :   ZoneList<HEnvironmentMarker*> markers_;
      53             :   bool collect_markers_;
      54             : 
      55             :   // Keeps track of the last simulate seen, as well as the environment slots
      56             :   // for which a new live range has started since (so they must not be zapped
      57             :   // in that simulate when the end of another live range of theirs is found).
      58             :   HSimulate* last_simulate_;
      59             :   BitVector went_live_since_last_simulate_;
      60             : 
      61             :   DISALLOW_COPY_AND_ASSIGN(HEnvironmentLivenessAnalysisPhase);
      62             : };
      63             : 
      64             : 
      65             : }  // namespace internal
      66             : }  // namespace v8
      67             : 
      68             : #endif  // V8_CRANKSHAFT_HYDROGEN_ENVIRONMENT_LIVENESS_H_