1 /* 2 * Copyright (C) 2022 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_WRITE_BARRIER_ELIMINATION_H_ 18 #define ART_COMPILER_OPTIMIZING_WRITE_BARRIER_ELIMINATION_H_ 19 20 #include "base/macros.h" 21 #include "optimization.h" 22 23 namespace art HIDDEN { 24 25 // Eliminates unnecessary write barriers from InstanceFieldSet, StaticFieldSet, and ArraySet. 26 // 27 // We can eliminate redundant write barriers as we don't need several for the same receiver. For 28 // example: 29 // MyObject o; 30 // o.inner_obj = io; 31 // o.inner_obj2 = io2; 32 // o.inner_obj3 = io3; 33 // We can keep the write barrier for `inner_obj` and remove the other two. 34 // 35 // In order to do this, we set the WriteBarrierKind of the instruction. The instruction's kind are 36 // set to kEmitBeingReliedOn (if this write barrier coalesced other write barriers, we don't want to 37 // perform the null check optimization), or to kDontEmit (if the write barrier as a whole is not 38 // needed). 39 class WriteBarrierElimination : public HOptimization { 40 public: 41 WriteBarrierElimination(HGraph* graph, 42 OptimizingCompilerStats* stats, 43 const char* name = kWBEPassName) HOptimization(graph,name,stats)44 : HOptimization(graph, name, stats) {} 45 46 bool Run() override; 47 48 static constexpr const char* kWBEPassName = "write_barrier_elimination"; 49 50 private: 51 DISALLOW_COPY_AND_ASSIGN(WriteBarrierElimination); 52 }; 53 54 } // namespace art 55 56 #endif // ART_COMPILER_OPTIMIZING_WRITE_BARRIER_ELIMINATION_H_ 57