Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 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 | 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_ |