DenseMap.h revision 9544dc294f63ce116fbab398a8874ebf834cf41e
1//===- llvm/ADT/DenseMap.h - Dense probed hash table ------------*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file was developed by Chris Lattner and is distributed under 6// the University of Illinois Open Source License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file defines the DenseMap class. 11// 12//===----------------------------------------------------------------------===// 13 14#ifndef LLVM_ADT_DENSEMAP_H 15#define LLVM_ADT_DENSEMAP_H 16 17#include "llvm/Support/DataTypes.h" 18#include "llvm/Support/MathExtras.h" 19#include <cassert> 20#include <utility> 21 22namespace llvm { 23 24template<typename T> 25struct DenseMapKeyInfo { 26 //static inline T getEmptyKey(); 27 //static inline T getTombstoneKey(); 28 //static unsigned getHashValue(const T &Val); 29 //static bool isPod() 30}; 31 32// Provide DenseMapKeyInfo for all pointers. 33template<typename T> 34struct DenseMapKeyInfo<T*> { 35 static inline T* getEmptyKey() { return reinterpret_cast<T*>(-1); } 36 static inline T* getTombstoneKey() { return reinterpret_cast<T*>(-2); } 37 static unsigned getHashValue(const T *PtrVal) { 38 return (unsigned(uintptr_t(PtrVal)) >> 4) ^ 39 (unsigned(uintptr_t(PtrVal)) >> 9); 40 } 41 static bool isPod() { return true; } 42}; 43 44template<typename KeyT, typename ValueT, 45 typename KeyInfoT = DenseMapKeyInfo<KeyT> > 46class DenseMapIterator; 47template<typename KeyT, typename ValueT, 48 typename KeyInfoT = DenseMapKeyInfo<KeyT> > 49class DenseMapConstIterator; 50 51template<typename KeyT, typename ValueT, 52 typename KeyInfoT = DenseMapKeyInfo<KeyT> > 53class DenseMap { 54 typedef std::pair<KeyT, ValueT> BucketT; 55 unsigned NumBuckets; 56 BucketT *Buckets; 57 58 unsigned NumEntries; 59 unsigned NumTombstones; 60public: 61 DenseMap(const DenseMap& other) { 62 NumBuckets = 0; 63 CopyFrom(other); 64 } 65 66 explicit DenseMap(unsigned NumInitBuckets = 64) { 67 init(NumInitBuckets); 68 } 69 70 ~DenseMap() { 71 const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey(); 72 for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) { 73 if (P->first != EmptyKey && P->first != TombstoneKey) 74 P->second.~ValueT(); 75 P->first.~KeyT(); 76 } 77 delete[] reinterpret_cast<char*>(Buckets); 78 } 79 80 typedef DenseMapIterator<KeyT, ValueT, KeyInfoT> iterator; 81 typedef DenseMapConstIterator<KeyT, ValueT, KeyInfoT> const_iterator; 82 inline iterator begin() { 83 return iterator(Buckets, Buckets+NumBuckets); 84 } 85 inline iterator end() { 86 return iterator(Buckets+NumBuckets, Buckets+NumBuckets); 87 } 88 inline const_iterator begin() const { 89 return const_iterator(Buckets, Buckets+NumBuckets); 90 } 91 inline const_iterator end() const { 92 return const_iterator(Buckets+NumBuckets, Buckets+NumBuckets); 93 } 94 95 bool empty() const { return NumEntries == 0; } 96 unsigned size() const { return NumEntries; } 97 98 void clear() { 99 // If the capacity of the array is huge, and the # elements used is small, 100 // shrink the array. 101 if (NumEntries * 4 < NumBuckets && NumBuckets > 64) { 102 shrink_and_clear(); 103 return; 104 } 105 106 const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey(); 107 for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) { 108 if (P->first != EmptyKey) { 109 if (P->first != TombstoneKey) { 110 P->second.~ValueT(); 111 --NumEntries; 112 } 113 P->first = EmptyKey; 114 } 115 } 116 assert(NumEntries == 0 && "Node count imbalance!"); 117 NumTombstones = 0; 118 } 119 120 /// count - Return true if the specified key is in the map. 121 bool count(const KeyT &Val) const { 122 BucketT *TheBucket; 123 return LookupBucketFor(Val, TheBucket); 124 } 125 126 iterator find(const KeyT &Val) { 127 BucketT *TheBucket; 128 if (LookupBucketFor(Val, TheBucket)) 129 return iterator(TheBucket, Buckets+NumBuckets); 130 return end(); 131 } 132 const_iterator find(const KeyT &Val) const { 133 BucketT *TheBucket; 134 if (LookupBucketFor(Val, TheBucket)) 135 return const_iterator(TheBucket, Buckets+NumBuckets); 136 return end(); 137 } 138 139 bool insert(const std::pair<KeyT, ValueT> &KV) { 140 BucketT *TheBucket; 141 if (LookupBucketFor(KV.first, TheBucket)) 142 return false; // Already in map. 143 144 // Otherwise, insert the new element. 145 InsertIntoBucket(KV.first, KV.second, TheBucket); 146 return true; 147 } 148 149 bool erase(const KeyT &Val) { 150 BucketT *TheBucket; 151 if (!LookupBucketFor(Val, TheBucket)) 152 return false; // not in map. 153 154 TheBucket->second.~ValueT(); 155 TheBucket->first = getTombstoneKey(); 156 --NumEntries; 157 ++NumTombstones; 158 return true; 159 } 160 bool erase(iterator I) { 161 BucketT *TheBucket = &*I; 162 TheBucket->second.~ValueT(); 163 TheBucket->first = getTombstoneKey(); 164 --NumEntries; 165 ++NumTombstones; 166 return true; 167 } 168 169 ValueT &operator[](const KeyT &Key) { 170 BucketT *TheBucket; 171 if (LookupBucketFor(Key, TheBucket)) 172 return TheBucket->second; 173 174 return InsertIntoBucket(Key, ValueT(), TheBucket)->second; 175 } 176 177 DenseMap& operator=(const DenseMap& other) { 178 CopyFrom(other); 179 return *this; 180 } 181 182private: 183 void CopyFrom(const DenseMap& other) { 184 if (NumBuckets != 0 && !KeyInfoT::isPod()) { 185 const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey(); 186 for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) { 187 if (P->first != EmptyKey && P->first != TombstoneKey) 188 P->second.~ValueT(); 189 P->first.~KeyT(); 190 } 191 } 192 193 NumEntries = other.NumEntries; 194 NumTombstones = other.NumTombstones; 195 196 if (NumBuckets) 197 delete[] reinterpret_cast<char*>(Buckets); 198 Buckets = reinterpret_cast<BucketT*>(new char[sizeof(BucketT) * 199 other.NumBuckets]); 200 201 if (KeyInfoT::isPod()) 202 memcpy(Buckets, other.Buckets, other.NumBuckets * sizeof(BucketT)); 203 else 204 for (size_t i = 0; i < other.NumBuckets; ++i) { 205 new (Buckets[i].first) KeyT(other.Buckets[i].first); 206 new (Buckets[i].second) ValueT(other.Buckets[i].second); 207 } 208 NumBuckets = other.NumBuckets; 209 } 210 211 BucketT *InsertIntoBucket(const KeyT &Key, const ValueT &Value, 212 BucketT *TheBucket) { 213 // If the load of the hash table is more than 3/4, or if fewer than 1/8 of 214 // the buckets are empty (meaning that many are filled with tombstones), 215 // grow the table. 216 // 217 // The later case is tricky. For example, if we had one empty bucket with 218 // tons of tombstones, failing lookups (e.g. for insertion) would have to 219 // probe almost the entire table until it found the empty bucket. If the 220 // table completely filled with tombstones, no lookup would ever succeed, 221 // causing infinite loops in lookup. 222 if (NumEntries*4 >= NumBuckets*3 || 223 NumBuckets-(NumEntries+NumTombstones) < NumBuckets/8) { 224 this->grow(); 225 LookupBucketFor(Key, TheBucket); 226 } 227 ++NumEntries; 228 229 // If we are writing over a tombstone, remember this. 230 if (TheBucket->first != getEmptyKey()) 231 --NumTombstones; 232 233 TheBucket->first = Key; 234 new (&TheBucket->second) ValueT(Value); 235 return TheBucket; 236 } 237 238 static unsigned getHashValue(const KeyT &Val) { 239 return KeyInfoT::getHashValue(Val); 240 } 241 static const KeyT getEmptyKey() { 242 return KeyInfoT::getEmptyKey(); 243 } 244 static const KeyT getTombstoneKey() { 245 return KeyInfoT::getTombstoneKey(); 246 } 247 248 /// LookupBucketFor - Lookup the appropriate bucket for Val, returning it in 249 /// FoundBucket. If the bucket contains the key and a value, this returns 250 /// true, otherwise it returns a bucket with an empty marker or tombstone and 251 /// returns false. 252 bool LookupBucketFor(const KeyT &Val, BucketT *&FoundBucket) const { 253 unsigned BucketNo = getHashValue(Val); 254 unsigned ProbeAmt = 1; 255 BucketT *BucketsPtr = Buckets; 256 257 // FoundTombstone - Keep track of whether we find a tombstone while probing. 258 BucketT *FoundTombstone = 0; 259 const KeyT EmptyKey = getEmptyKey(); 260 const KeyT TombstoneKey = getTombstoneKey(); 261 assert(Val != EmptyKey && Val != TombstoneKey && 262 "Empty/Tombstone value shouldn't be inserted into map!"); 263 264 while (1) { 265 BucketT *ThisBucket = BucketsPtr + (BucketNo & (NumBuckets-1)); 266 // Found Val's bucket? If so, return it. 267 if (ThisBucket->first == Val) { 268 FoundBucket = ThisBucket; 269 return true; 270 } 271 272 // If we found an empty bucket, the key doesn't exist in the set. 273 // Insert it and return the default value. 274 if (ThisBucket->first == EmptyKey) { 275 // If we've already seen a tombstone while probing, fill it in instead 276 // of the empty bucket we eventually probed to. 277 if (FoundTombstone) ThisBucket = FoundTombstone; 278 FoundBucket = FoundTombstone ? FoundTombstone : ThisBucket; 279 return false; 280 } 281 282 // If this is a tombstone, remember it. If Val ends up not in the map, we 283 // prefer to return it than something that would require more probing. 284 if (ThisBucket->first == TombstoneKey && !FoundTombstone) 285 FoundTombstone = ThisBucket; // Remember the first tombstone found. 286 287 // Otherwise, it's a hash collision or a tombstone, continue quadratic 288 // probing. 289 BucketNo += ProbeAmt++; 290 } 291 } 292 293 void init(unsigned InitBuckets) { 294 NumEntries = 0; 295 NumTombstones = 0; 296 NumBuckets = InitBuckets; 297 assert(InitBuckets && (InitBuckets & InitBuckets-1) == 0 && 298 "# initial buckets must be a power of two!"); 299 Buckets = reinterpret_cast<BucketT*>(new char[sizeof(BucketT)*InitBuckets]); 300 // Initialize all the keys to EmptyKey. 301 const KeyT EmptyKey = getEmptyKey(); 302 for (unsigned i = 0; i != InitBuckets; ++i) 303 new (&Buckets[i].first) KeyT(EmptyKey); 304 } 305 306 void grow() { 307 unsigned OldNumBuckets = NumBuckets; 308 BucketT *OldBuckets = Buckets; 309 310 // Double the number of buckets. 311 NumBuckets <<= 1; 312 NumTombstones = 0; 313 Buckets = reinterpret_cast<BucketT*>(new char[sizeof(BucketT)*NumBuckets]); 314 315 // Initialize all the keys to EmptyKey. 316 const KeyT EmptyKey = getEmptyKey(); 317 for (unsigned i = 0, e = NumBuckets; i != e; ++i) 318 new (&Buckets[i].first) KeyT(EmptyKey); 319 320 // Insert all the old elements. 321 const KeyT TombstoneKey = getTombstoneKey(); 322 for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) { 323 if (B->first != EmptyKey && B->first != TombstoneKey) { 324 // Insert the key/value into the new table. 325 BucketT *DestBucket; 326 bool FoundVal = LookupBucketFor(B->first, DestBucket); 327 FoundVal = FoundVal; // silence warning. 328 assert(!FoundVal && "Key already in new map?"); 329 DestBucket->first = B->first; 330 new (&DestBucket->second) ValueT(B->second); 331 332 // Free the value. 333 B->second.~ValueT(); 334 } 335 B->first.~KeyT(); 336 } 337 338 // Free the old table. 339 delete[] reinterpret_cast<char*>(OldBuckets); 340 } 341 342 void shrink_and_clear() { 343 unsigned OldNumBuckets = NumBuckets; 344 BucketT *OldBuckets = Buckets; 345 346 // Reduce the number of buckets. 347 NumBuckets = NumEntries > 32 ? 1 << (Log2_32_Ceil(NumEntries) + 1) 348 : 64; 349 NumTombstones = 0; 350 Buckets = reinterpret_cast<BucketT*>(new char[sizeof(BucketT)*NumBuckets]); 351 352 // Initialize all the keys to EmptyKey. 353 const KeyT EmptyKey = getEmptyKey(); 354 for (unsigned i = 0, e = NumBuckets; i != e; ++i) 355 new (&Buckets[i].first) KeyT(EmptyKey); 356 357 // Free the old buckets. 358 const KeyT TombstoneKey = getTombstoneKey(); 359 for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) { 360 if (B->first != EmptyKey && B->first != TombstoneKey) { 361 // Free the value. 362 B->second.~ValueT(); 363 } 364 B->first.~KeyT(); 365 } 366 367 // Free the old table. 368 delete[] reinterpret_cast<char*>(OldBuckets); 369 370 NumEntries = 0; 371 } 372}; 373 374template<typename KeyT, typename ValueT, typename KeyInfoT> 375class DenseMapIterator { 376 typedef std::pair<KeyT, ValueT> BucketT; 377protected: 378 const BucketT *Ptr, *End; 379public: 380 DenseMapIterator(const BucketT *Pos, const BucketT *E) : Ptr(Pos), End(E) { 381 AdvancePastEmptyBuckets(); 382 } 383 384 std::pair<KeyT, ValueT> &operator*() const { 385 return *const_cast<BucketT*>(Ptr); 386 } 387 std::pair<KeyT, ValueT> *operator->() const { 388 return const_cast<BucketT*>(Ptr); 389 } 390 391 bool operator==(const DenseMapIterator &RHS) const { 392 return Ptr == RHS.Ptr; 393 } 394 bool operator!=(const DenseMapIterator &RHS) const { 395 return Ptr != RHS.Ptr; 396 } 397 398 inline DenseMapIterator& operator++() { // Preincrement 399 ++Ptr; 400 AdvancePastEmptyBuckets(); 401 return *this; 402 } 403 DenseMapIterator operator++(int) { // Postincrement 404 DenseMapIterator tmp = *this; ++*this; return tmp; 405 } 406 407private: 408 void AdvancePastEmptyBuckets() { 409 const KeyT Empty = KeyInfoT::getEmptyKey(); 410 const KeyT Tombstone = KeyInfoT::getTombstoneKey(); 411 412 while (Ptr != End && (Ptr->first == Empty || Ptr->first == Tombstone)) 413 ++Ptr; 414 } 415}; 416 417template<typename KeyT, typename ValueT, typename KeyInfoT> 418class DenseMapConstIterator : public DenseMapIterator<KeyT, ValueT, KeyInfoT> { 419public: 420 DenseMapConstIterator(const std::pair<KeyT, ValueT> *Pos, 421 const std::pair<KeyT, ValueT> *E) 422 : DenseMapIterator<KeyT, ValueT, KeyInfoT>(Pos, E) { 423 } 424 const std::pair<KeyT, ValueT> &operator*() const { 425 return *this->Ptr; 426 } 427 const std::pair<KeyT, ValueT> *operator->() const { 428 return this->Ptr; 429 } 430}; 431 432} // end namespace llvm 433 434#endif 435