1 //===-- GlobalDCE.h - DCE unreachable internal functions ------------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This transform is designed to eliminate unreachable internal globals from the 11 // program. It uses an aggressive algorithm, searching out globals that are 12 // known to be alive. After it finds all of the globals which are needed, it 13 // deletes whatever is left over. This allows it to delete recursive chunks of 14 // the program which are unreachable. 15 // 16 //===----------------------------------------------------------------------===// 17 18 #ifndef LLVM_TRANSFORMS_IPO_GLOBALDCE_H 19 #define LLVM_TRANSFORMS_IPO_GLOBALDCE_H 20 21 #include "llvm/ADT/DenseMap.h" 22 #include "llvm/ADT/SmallSet.h" 23 #include "llvm/IR/Module.h" 24 #include "llvm/IR/PassManager.h" 25 #include <unordered_map> 26 27 namespace llvm { 28 29 /// Pass to remove unused function declarations. 30 class GlobalDCEPass : public PassInfoMixin<GlobalDCEPass> { 31 public: 32 PreservedAnalyses run(Module &M, ModuleAnalysisManager &); 33 34 private: 35 SmallPtrSet<GlobalValue*, 32> AliveGlobals; 36 37 /// Global -> Global that uses this global. 38 std::unordered_multimap<GlobalValue *, GlobalValue *> GVDependencies; 39 40 /// Constant -> Globals that use this global cache. 41 std::unordered_map<Constant *, SmallPtrSet<GlobalValue *, 8>> 42 ConstantDependenciesCache; 43 44 /// Comdat -> Globals in that Comdat section. 45 std::unordered_multimap<Comdat *, GlobalValue *> ComdatMembers; 46 47 void UpdateGVDependencies(GlobalValue &GV); 48 void MarkLive(GlobalValue &GV, 49 SmallVectorImpl<GlobalValue *> *Updates = nullptr); 50 bool RemoveUnusedGlobalValue(GlobalValue &GV); 51 52 void ComputeDependencies(Value *V, SmallPtrSetImpl<GlobalValue *> &U); 53 }; 54 55 } 56 57 #endif // LLVM_TRANSFORMS_IPO_GLOBALDCE_H 58
