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| 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_HYDROGEN_ENVIRONMENT_LIVENESS_H_ | |
| 6 #define V8_HYDROGEN_ENVIRONMENT_LIVENESS_H_ | |
| 7 | |
| 8 | |
| 9 #include "src/hydrogen.h" | |
| 10 | |
| 11 namespace v8 { | |
| 12 namespace internal { | |
| 13 | |
| 14 | |
| 15 // Trims live ranges of environment slots by doing explicit liveness analysis. | |
| 16 // Values in the environment are kept alive by every subsequent LInstruction | |
| 17 // that is assigned an LEnvironment, which creates register pressure and | |
| 18 // unnecessary spill slot moves. Therefore it is beneficial to trim the | |
| 19 // live ranges of environment slots by zapping them with a constant after | |
| 20 // the last lookup that refers to them. | |
| 21 // Slots are identified by their index and only affected if whitelisted in | |
| 22 // HOptimizedGraphBuilder::IsEligibleForEnvironmentLivenessAnalysis(). | |
| 23 class HEnvironmentLivenessAnalysisPhase : public HPhase { | |
| 24 public: | |
| 25 explicit HEnvironmentLivenessAnalysisPhase(HGraph* graph); | |
| 26 | |
| 27 void Run(); | |
| 28 | |
| 29 private: | |
| 30 void ZapEnvironmentSlot(int index, HSimulate* simulate); | |
| 31 void ZapEnvironmentSlotsInSuccessors(HBasicBlock* block, BitVector* live); | |
| 32 void ZapEnvironmentSlotsForInstruction(HEnvironmentMarker* marker); | |
| 33 void UpdateLivenessAtBlockEnd(HBasicBlock* block, BitVector* live); | |
| 34 void UpdateLivenessAtInstruction(HInstruction* instr, BitVector* live); | |
| 35 #ifdef DEBUG | |
| 36 bool VerifyClosures(Handle<JSFunction> a, Handle<JSFunction> b); | |
| 37 #endif | |
| 38 | |
| 39 int block_count_; | |
| 40 | |
| 41 // Largest number of local variables in any environment in the graph | |
| 42 // (including inlined environments). | |
| 43 int maximum_environment_size_; | |
| 44 | |
| 45 // Per-block data. All these lists are indexed by block_id. | |
| 46 ZoneList<BitVector*> live_at_block_start_; | |
| 47 ZoneList<HSimulate*> first_simulate_; | |
| 48 ZoneList<BitVector*> first_simulate_invalid_for_index_; | |
| 49 | |
| 50 // List of all HEnvironmentMarker instructions for quick iteration/deletion. | |
| 51 // It is populated during the first pass over the graph, controlled by | |
| 52 // |collect_markers_|. | |
| 53 ZoneList<HEnvironmentMarker*> markers_; | |
| 54 bool collect_markers_; | |
| 55 | |
| 56 // Keeps track of the last simulate seen, as well as the environment slots | |
| 57 // for which a new live range has started since (so they must not be zapped | |
| 58 // in that simulate when the end of another live range of theirs is found). | |
| 59 HSimulate* last_simulate_; | |
| 60 BitVector went_live_since_last_simulate_; | |
| 61 | |
| 62 DISALLOW_COPY_AND_ASSIGN(HEnvironmentLivenessAnalysisPhase); | |
| 63 }; | |
| 64 | |
| 65 | |
| 66 } // namespace internal | |
| 67 } // namespace v8 | |
| 68 | |
| 69 #endif /* V8_HYDROGEN_ENVIRONMENT_LIVENESS_H_ */ | |
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