1 /* 2 * Copyright (C) 2014 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef ART_COMPILER_OPTIMIZING_SSA_PHI_ELIMINATION_H_ 18 #define ART_COMPILER_OPTIMIZING_SSA_PHI_ELIMINATION_H_ 19 20 #include "base/arena_containers.h" 21 #include "nodes.h" 22 #include "optimization.h" 23 24 namespace art { 25 26 /** 27 * Optimization phase that removes dead phis from the graph. Dead phis are unused 28 * phis, or phis only used by other phis. 29 */ 30 class SsaDeadPhiElimination : public HOptimization { 31 public: 32 explicit SsaDeadPhiElimination(HGraph* graph) 33 : HOptimization(graph, kSsaDeadPhiEliminationPassName), 34 worklist_(graph->GetArena()->Adapter(kArenaAllocSsaPhiElimination)) { 35 worklist_.reserve(kDefaultWorklistSize); 36 } 37 38 void Run() OVERRIDE; 39 40 void MarkDeadPhis(); 41 void EliminateDeadPhis(); 42 43 static constexpr const char* kSsaDeadPhiEliminationPassName = "dead_phi_elimination"; 44 45 private: 46 ArenaVector<HPhi*> worklist_; 47 48 static constexpr size_t kDefaultWorklistSize = 8; 49 50 DISALLOW_COPY_AND_ASSIGN(SsaDeadPhiElimination); 51 }; 52 53 /** 54 * Removes redundant phis that may have been introduced when doing SSA conversion. 55 * For example, when entering a loop, we create phis for all live registers. These 56 * registers might be updated with the same value, or not updated at all. We can just 57 * replace the phi with the value when entering the loop. 58 */ 59 class SsaRedundantPhiElimination : public HOptimization { 60 public: 61 explicit SsaRedundantPhiElimination(HGraph* graph) 62 : HOptimization(graph, kSsaRedundantPhiEliminationPassName), 63 worklist_(graph->GetArena()->Adapter(kArenaAllocSsaPhiElimination)) { 64 worklist_.reserve(kDefaultWorklistSize); 65 } 66 67 void Run() OVERRIDE; 68 69 static constexpr const char* kSsaRedundantPhiEliminationPassName = "redundant_phi_elimination"; 70 71 private: 72 ArenaVector<HPhi*> worklist_; 73 74 static constexpr size_t kDefaultWorklistSize = 8; 75 76 DISALLOW_COPY_AND_ASSIGN(SsaRedundantPhiElimination); 77 }; 78 79 } // namespace art 80 81 #endif // ART_COMPILER_OPTIMIZING_SSA_PHI_ELIMINATION_H_ 82
