1 //===- llvm/ADT/MapVector.h - Map w/ deterministic value order --*- 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 /// \file 10 /// This file implements a map that provides insertion order iteration. The 11 /// interface is purposefully minimal. The key is assumed to be cheap to copy 12 /// and 2 copies are kept, one for indexing in a DenseMap, one for iteration in 13 /// a SmallVector. 14 /// 15 //===----------------------------------------------------------------------===// 16 17 #ifndef LLVM_ADT_MAPVECTOR_H 18 #define LLVM_ADT_MAPVECTOR_H 19 20 #include "llvm/ADT/DenseMap.h" 21 #include "llvm/ADT/SmallVector.h" 22 #include <cassert> 23 #include <cstddef> 24 #include <iterator> 25 #include <type_traits> 26 #include <utility> 27 28 namespace llvm { 29 30 /// This class implements a map that also provides access to all stored values 31 /// in a deterministic order. The values are kept in a SmallVector<*, 0> and the 32 /// mapping is done with DenseMap from Keys to indexes in that vector. 33 template <typename KeyT, typename ValueT, 34 typename MapType = DenseMap<KeyT, unsigned>, 35 typename VectorType = SmallVector<std::pair<KeyT, ValueT>, 0>> 36 class MapVector { 37 MapType Map; 38 VectorType Vector; 39 40 static_assert( 41 std::is_integral_v<typename MapType::mapped_type>, 42 "The mapped_type of the specified Map must be an integral type"); 43 44 public: 45 using key_type = KeyT; 46 using value_type = typename VectorType::value_type; 47 using size_type = typename VectorType::size_type; 48 49 using iterator = typename VectorType::iterator; 50 using const_iterator = typename VectorType::const_iterator; 51 using reverse_iterator = typename VectorType::reverse_iterator; 52 using const_reverse_iterator = typename VectorType::const_reverse_iterator; 53 54 /// Clear the MapVector and return the underlying vector. 55 VectorType takeVector() { 56 Map.clear(); 57 return std::move(Vector); 58 } 59 60 size_type size() const { return Vector.size(); } 61 62 /// Grow the MapVector so that it can contain at least \p NumEntries items 63 /// before resizing again. 64 void reserve(size_type NumEntries) { 65 Map.reserve(NumEntries); 66 Vector.reserve(NumEntries); 67 } 68 69 iterator begin() { return Vector.begin(); } 70 const_iterator begin() const { return Vector.begin(); } 71 iterator end() { return Vector.end(); } 72 const_iterator end() const { return Vector.end(); } 73 74 reverse_iterator rbegin() { return Vector.rbegin(); } 75 const_reverse_iterator rbegin() const { return Vector.rbegin(); } 76 reverse_iterator rend() { return Vector.rend(); } 77 const_reverse_iterator rend() const { return Vector.rend(); } 78 79 bool empty() const { 80 return Vector.empty(); 81 } 82 83 std::pair<KeyT, ValueT> &front() { return Vector.front(); } 84 const std::pair<KeyT, ValueT> &front() const { return Vector.front(); } 85 std::pair<KeyT, ValueT> &back() { return Vector.back(); } 86 const std::pair<KeyT, ValueT> &back() const { return Vector.back(); } 87 88 void clear() { 89 Map.clear(); 90 Vector.clear(); 91 } 92 93 void swap(MapVector &RHS) { 94 std::swap(Map, RHS.Map); 95 std::swap(Vector, RHS.Vector); 96 } 97 98 ValueT &operator[](const KeyT &Key) { 99 std::pair<KeyT, typename MapType::mapped_type> Pair = std::make_pair(Key, 0); 100 std::pair<typename MapType::iterator, bool> Result = Map.insert(Pair); 101 auto &I = Result.first->second; 102 if (Result.second) { 103 Vector.push_back(std::make_pair(Key, ValueT())); 104 I = Vector.size() - 1; 105 } 106 return Vector[I].second; 107 } 108 109 // Returns a copy of the value. Only allowed if ValueT is copyable. 110 ValueT lookup(const KeyT &Key) const { 111 static_assert(std::is_copy_constructible_v<ValueT>, 112 "Cannot call lookup() if ValueT is not copyable."); 113 typename MapType::const_iterator Pos = Map.find(Key); 114 return Pos == Map.end()? ValueT() : Vector[Pos->second].second; 115 } 116 117 std::pair<iterator, bool> insert(const std::pair<KeyT, ValueT> &KV) { 118 std::pair<KeyT, typename MapType::mapped_type> Pair = std::make_pair(KV.first, 0); 119 std::pair<typename MapType::iterator, bool> Result = Map.insert(Pair); 120 auto &I = Result.first->second; 121 if (Result.second) { 122 Vector.push_back(std::make_pair(KV.first, KV.second)); 123 I = Vector.size() - 1; 124 return std::make_pair(std::prev(end()), true); 125 } 126 return std::make_pair(begin() + I, false); 127 } 128 129 std::pair<iterator, bool> insert(std::pair<KeyT, ValueT> &&KV) { 130 // Copy KV.first into the map, then move it into the vector. 131 std::pair<KeyT, typename MapType::mapped_type> Pair = std::make_pair(KV.first, 0); 132 std::pair<typename MapType::iterator, bool> Result = Map.insert(Pair); 133 auto &I = Result.first->second; 134 if (Result.second) { 135 Vector.push_back(std::move(KV)); 136 I = Vector.size() - 1; 137 return std::make_pair(std::prev(end()), true); 138 } 139 return std::make_pair(begin() + I, false); 140 } 141 142 bool contains(const KeyT &Key) const { return Map.find(Key) != Map.end(); } 143 144 size_type count(const KeyT &Key) const { return contains(Key) ? 1 : 0; } 145 146 iterator find(const KeyT &Key) { 147 typename MapType::const_iterator Pos = Map.find(Key); 148 return Pos == Map.end()? Vector.end() : 149 (Vector.begin() + Pos->second); 150 } 151 152 const_iterator find(const KeyT &Key) const { 153 typename MapType::const_iterator Pos = Map.find(Key); 154 return Pos == Map.end()? Vector.end() : 155 (Vector.begin() + Pos->second); 156 } 157 158 /// Remove the last element from the vector. 159 void pop_back() { 160 typename MapType::iterator Pos = Map.find(Vector.back().first); 161 Map.erase(Pos); 162 Vector.pop_back(); 163 } 164 165 /// Remove the element given by Iterator. 166 /// 167 /// Returns an iterator to the element following the one which was removed, 168 /// which may be end(). 169 /// 170 /// \note This is a deceivingly expensive operation (linear time). It's 171 /// usually better to use \a remove_if() if possible. 172 typename VectorType::iterator erase(typename VectorType::iterator Iterator) { 173 Map.erase(Iterator->first); 174 auto Next = Vector.erase(Iterator); 175 if (Next == Vector.end()) 176 return Next; 177 178 // Update indices in the map. 179 size_t Index = Next - Vector.begin(); 180 for (auto &I : Map) { 181 assert(I.second != Index && "Index was already erased!"); 182 if (I.second > Index) 183 --I.second; 184 } 185 return Next; 186 } 187 188 /// Remove all elements with the key value Key. 189 /// 190 /// Returns the number of elements removed. 191 size_type erase(const KeyT &Key) { 192 auto Iterator = find(Key); 193 if (Iterator == end()) 194 return 0; 195 erase(Iterator); 196 return 1; 197 } 198 199 /// Remove the elements that match the predicate. 200 /// 201 /// Erase all elements that match \c Pred in a single pass. Takes linear 202 /// time. 203 template <class Predicate> void remove_if(Predicate Pred); 204 }; 205 206 template <typename KeyT, typename ValueT, typename MapType, typename VectorType> 207 template <class Function> 208 void MapVector<KeyT, ValueT, MapType, VectorType>::remove_if(Function Pred) { 209 auto O = Vector.begin(); 210 for (auto I = O, E = Vector.end(); I != E; ++I) { 211 if (Pred(*I)) { 212 // Erase from the map. 213 Map.erase(I->first); 214 continue; 215 } 216 217 if (I != O) { 218 // Move the value and update the index in the map. 219 *O = std::move(*I); 220 Map[O->first] = O - Vector.begin(); 221 } 222 ++O; 223 } 224 // Erase trailing entries in the vector. 225 Vector.erase(O, Vector.end()); 226 } 227 228 /// A MapVector that performs no allocations if smaller than a certain 229 /// size. 230 template <typename KeyT, typename ValueT, unsigned N> 231 struct SmallMapVector 232 : MapVector<KeyT, ValueT, SmallDenseMap<KeyT, unsigned, N>, 233 SmallVector<std::pair<KeyT, ValueT>, N>> { 234 }; 235 236 } // end namespace llvm 237 238 #endif // LLVM_ADT_MAPVECTOR_H 239