1 // Copyright 2013 the V8 project authors. All rights reserved. 2 // Redistribution and use in source and binary forms, with or without 3 // modification, are permitted provided that the following conditions are 4 // met: 5 // 6 // * Redistributions of source code must retain the above copyright 7 // notice, this list of conditions and the following disclaimer. 8 // * Redistributions in binary form must reproduce the above 9 // copyright notice, this list of conditions and the following 10 // disclaimer in the documentation and/or other materials provided 11 // with the distribution. 12 // * Neither the name of Google Inc. nor the names of its 13 // contributors may be used to endorse or promote products derived 14 // from this software without specific prior written permission. 15 // 16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 28 #ifndef V8_HYDROGEN_ENVIRONMENT_LIVENESS_H_ 29 #define V8_HYDROGEN_ENVIRONMENT_LIVENESS_H_ 30 31 32 #include "hydrogen.h" 33 34 namespace v8 { 35 namespace internal { 36 37 38 // Trims live ranges of environment slots by doing explicit liveness analysis. 39 // Values in the environment are kept alive by every subsequent LInstruction 40 // that is assigned an LEnvironment, which creates register pressure and 41 // unnecessary spill slot moves. Therefore it is beneficial to trim the 42 // live ranges of environment slots by zapping them with a constant after 43 // the last lookup that refers to them. 44 // Slots are identified by their index and only affected if whitelisted in 45 // HOptimizedGraphBuilder::IsEligibleForEnvironmentLivenessAnalysis(). 46 class HEnvironmentLivenessAnalysisPhase : public HPhase { 47 public: 48 explicit HEnvironmentLivenessAnalysisPhase(HGraph* graph); 49 50 void Run(); 51 52 private: 53 void ZapEnvironmentSlot(int index, HSimulate* simulate); 54 void ZapEnvironmentSlotsInSuccessors(HBasicBlock* block, BitVector* live); 55 void ZapEnvironmentSlotsForInstruction(HEnvironmentMarker* marker); 56 void UpdateLivenessAtBlockEnd(HBasicBlock* block, BitVector* live); 57 void UpdateLivenessAtInstruction(HInstruction* instr, BitVector* live); 58 59 int block_count_; 60 61 // Largest number of local variables in any environment in the graph 62 // (including inlined environments). 63 int maximum_environment_size_; 64 65 // Per-block data. All these lists are indexed by block_id. 66 ZoneList<BitVector*> live_at_block_start_; 67 ZoneList<HSimulate*> first_simulate_; 68 ZoneList<BitVector*> first_simulate_invalid_for_index_; 69 70 // List of all HEnvironmentMarker instructions for quick iteration/deletion. 71 // It is populated during the first pass over the graph, controlled by 72 // |collect_markers_|. 73 ZoneList<HEnvironmentMarker*> markers_; 74 bool collect_markers_; 75 76 // Keeps track of the last simulate seen, as well as the environment slots 77 // for which a new live range has started since (so they must not be zapped 78 // in that simulate when the end of another live range of theirs is found). 79 HSimulate* last_simulate_; 80 BitVector went_live_since_last_simulate_; 81 82 DISALLOW_COPY_AND_ASSIGN(HEnvironmentLivenessAnalysisPhase); 83 }; 84 85 86 } } // namespace v8::internal 87 88 #endif /* V8_HYDROGEN_ENVIRONMENT_LIVENESS_H_ */ 89