1 //=== InstructionWorklist.h - Worklist for InstCombine & others -*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #ifndef LLVM_TRANSFORMS_UTILS_INSTRUCTIONWORKLIST_H 10 #define LLVM_TRANSFORMS_UTILS_INSTRUCTIONWORKLIST_H 11 12 #include "llvm/ADT/DenseMap.h" 13 #include "llvm/ADT/STLExtras.h" 14 #include "llvm/ADT/SetVector.h" 15 #include "llvm/ADT/SmallVector.h" 16 #include "llvm/IR/Instruction.h" 17 #include "llvm/Support/Compiler.h" 18 #include "llvm/Support/Debug.h" 19 #include "llvm/Support/raw_ostream.h" 20 21 namespace llvm { 22 23 /// InstructionWorklist - This is the worklist management logic for 24 /// InstCombine and other simplification passes. 25 class InstructionWorklist { 26 SmallVector<Instruction *, 256> Worklist; 27 DenseMap<Instruction *, unsigned> WorklistMap; 28 /// These instructions will be added in reverse order after the current 29 /// combine has finished. This means that these instructions will be visited 30 /// in the order they have been added. 31 SmallSetVector<Instruction *, 16> Deferred; 32 33 public: 34 InstructionWorklist() = default; 35 36 InstructionWorklist(InstructionWorklist &&) = default; 37 InstructionWorklist &operator=(InstructionWorklist &&) = default; 38 isEmpty()39 bool isEmpty() const { return Worklist.empty() && Deferred.empty(); } 40 41 /// Add instruction to the worklist. 42 /// Instructions will be visited in the order they are added. 43 /// You likely want to use this method. add(Instruction * I)44 void add(Instruction *I) { 45 if (Deferred.insert(I)) 46 LLVM_DEBUG(dbgs() << "ADD DEFERRED: " << *I << '\n'); 47 } 48 49 /// Add value to the worklist if it is an instruction. 50 /// Instructions will be visited in the order they are added. addValue(Value * V)51 void addValue(Value *V) { 52 if (Instruction *I = dyn_cast<Instruction>(V)) 53 add(I); 54 } 55 56 /// Push the instruction onto the worklist stack. 57 /// Instructions that have been added first will be visited last. push(Instruction * I)58 void push(Instruction *I) { 59 assert(I); 60 assert(I->getParent() && "Instruction not inserted yet?"); 61 62 if (WorklistMap.insert(std::make_pair(I, Worklist.size())).second) { 63 LLVM_DEBUG(dbgs() << "ADD: " << *I << '\n'); 64 Worklist.push_back(I); 65 } 66 } 67 pushValue(Value * V)68 void pushValue(Value *V) { 69 if (Instruction *I = dyn_cast<Instruction>(V)) 70 push(I); 71 } 72 popDeferred()73 Instruction *popDeferred() { 74 if (Deferred.empty()) 75 return nullptr; 76 return Deferred.pop_back_val(); 77 } 78 reserve(size_t Size)79 void reserve(size_t Size) { 80 Worklist.reserve(Size + 16); 81 WorklistMap.reserve(Size); 82 } 83 84 /// Remove I from the worklist if it exists. remove(Instruction * I)85 void remove(Instruction *I) { 86 DenseMap<Instruction *, unsigned>::iterator It = WorklistMap.find(I); 87 if (It != WorklistMap.end()) { 88 // Don't bother moving everything down, just null out the slot. 89 Worklist[It->second] = nullptr; 90 WorklistMap.erase(It); 91 } 92 93 Deferred.remove(I); 94 } 95 removeOne()96 Instruction *removeOne() { 97 if (Worklist.empty()) 98 return nullptr; 99 Instruction *I = Worklist.pop_back_val(); 100 WorklistMap.erase(I); 101 return I; 102 } 103 104 /// When an instruction is simplified, add all users of the instruction 105 /// to the work lists because they might get more simplified now. pushUsersToWorkList(Instruction & I)106 void pushUsersToWorkList(Instruction &I) { 107 for (User *U : I.users()) 108 push(cast<Instruction>(U)); 109 } 110 111 /// Should be called *after* decrementing the use-count on V. handleUseCountDecrement(Value * V)112 void handleUseCountDecrement(Value *V) { 113 if (auto *I = dyn_cast<Instruction>(V)) { 114 add(I); 115 // Many folds have one-use limitations. If there's only one use left, 116 // revisit that use. 117 if (I->hasOneUse()) 118 add(cast<Instruction>(*I->user_begin())); 119 } 120 } 121 122 /// Check that the worklist is empty and nuke the backing store for the map. zap()123 void zap() { 124 assert(WorklistMap.empty() && "Worklist empty, but map not?"); 125 assert(Deferred.empty() && "Deferred instructions left over"); 126 127 // Do an explicit clear, this shrinks the map if needed. 128 WorklistMap.clear(); 129 } 130 }; 131 132 } // end namespace llvm. 133 134 #endif 135