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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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