DenseMap.h revision 88b0c6a59a54a2d7b3763dfabb595ce0e09e658a
1//===- llvm/ADT/DenseMap.h - Dense probed hash table ------------*- C++ -*-===// 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 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/MathExtras.h" 18#include "llvm/Support/PointerLikeTypeTraits.h" 19#include "llvm/Support/type_traits.h" 20#include "llvm/ADT/DenseMapInfo.h" 21#include <algorithm> 22#include <iterator> 23#include <new> 24#include <utility> 25#include <cassert> 26#include <cstddef> 27#include <cstring> 28 29namespace llvm { 30 31template<typename KeyT, typename ValueT, 32 typename KeyInfoT = DenseMapInfo<KeyT>, 33 typename ValueInfoT = DenseMapInfo<ValueT>, bool IsConst = false> 34class DenseMapIterator; 35 36template<typename KeyT, typename ValueT, 37 typename KeyInfoT = DenseMapInfo<KeyT>, 38 typename ValueInfoT = DenseMapInfo<ValueT> > 39class DenseMap { 40 typedef std::pair<KeyT, ValueT> BucketT; 41 unsigned NumBuckets; 42 BucketT *Buckets; 43 44 unsigned NumEntries; 45 unsigned NumTombstones; 46public: 47 typedef KeyT key_type; 48 typedef ValueT mapped_type; 49 typedef BucketT value_type; 50 51 DenseMap(const DenseMap &other) { 52 NumBuckets = 0; 53 CopyFrom(other); 54 } 55 56 explicit DenseMap(unsigned NumInitBuckets = 0) { 57 init(NumInitBuckets); 58 } 59 60 template<typename InputIt> 61 DenseMap(const InputIt &I, const InputIt &E) { 62 init(NextPowerOf2(std::distance(I, E))); 63 insert(I, E); 64 } 65 66 ~DenseMap() { 67 const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey(); 68 for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) { 69 if (!KeyInfoT::isEqual(P->first, EmptyKey) && 70 !KeyInfoT::isEqual(P->first, TombstoneKey)) 71 P->second.~ValueT(); 72 P->first.~KeyT(); 73 } 74#ifndef NDEBUG 75 memset(Buckets, 0x5a, sizeof(BucketT)*NumBuckets); 76#endif 77 operator delete(Buckets); 78 } 79 80 typedef DenseMapIterator<KeyT, ValueT, KeyInfoT> iterator; 81 typedef DenseMapIterator<KeyT, ValueT, 82 KeyInfoT, ValueInfoT, true> const_iterator; 83 inline iterator begin() { 84 // When the map is empty, avoid the overhead of AdvancePastEmptyBuckets(). 85 return empty() ? end() : iterator(Buckets, Buckets+NumBuckets); 86 } 87 inline iterator end() { 88 return iterator(Buckets+NumBuckets, Buckets+NumBuckets); 89 } 90 inline const_iterator begin() const { 91 return empty() ? end() : const_iterator(Buckets, Buckets+NumBuckets); 92 } 93 inline const_iterator end() const { 94 return const_iterator(Buckets+NumBuckets, Buckets+NumBuckets); 95 } 96 97 bool empty() const { return NumEntries == 0; } 98 unsigned size() const { return NumEntries; } 99 100 /// Grow the densemap so that it has at least Size buckets. Does not shrink 101 void resize(size_t Size) { 102 if (Size > NumBuckets) 103 grow(Size); 104 } 105 106 void clear() { 107 if (NumEntries == 0 && NumTombstones == 0) return; 108 109 // If the capacity of the array is huge, and the # elements used is small, 110 // shrink the array. 111 if (NumEntries * 4 < NumBuckets && NumBuckets > 64) { 112 shrink_and_clear(); 113 return; 114 } 115 116 const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey(); 117 for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) { 118 if (!KeyInfoT::isEqual(P->first, EmptyKey)) { 119 if (!KeyInfoT::isEqual(P->first, TombstoneKey)) { 120 P->second.~ValueT(); 121 --NumEntries; 122 } 123 P->first = EmptyKey; 124 } 125 } 126 assert(NumEntries == 0 && "Node count imbalance!"); 127 NumTombstones = 0; 128 } 129 130 /// count - Return true if the specified key is in the map. 131 bool count(const KeyT &Val) const { 132 BucketT *TheBucket; 133 return LookupBucketFor(Val, TheBucket); 134 } 135 136 iterator find(const KeyT &Val) { 137 BucketT *TheBucket; 138 if (LookupBucketFor(Val, TheBucket)) 139 return iterator(TheBucket, Buckets+NumBuckets); 140 return end(); 141 } 142 const_iterator find(const KeyT &Val) const { 143 BucketT *TheBucket; 144 if (LookupBucketFor(Val, TheBucket)) 145 return const_iterator(TheBucket, Buckets+NumBuckets); 146 return end(); 147 } 148 149 /// lookup - Return the entry for the specified key, or a default 150 /// constructed value if no such entry exists. 151 ValueT lookup(const KeyT &Val) const { 152 BucketT *TheBucket; 153 if (LookupBucketFor(Val, TheBucket)) 154 return TheBucket->second; 155 return ValueT(); 156 } 157 158 // Inserts key,value pair into the map if the key isn't already in the map. 159 // If the key is already in the map, it returns false and doesn't update the 160 // value. 161 std::pair<iterator, bool> insert(const std::pair<KeyT, ValueT> &KV) { 162 BucketT *TheBucket; 163 if (LookupBucketFor(KV.first, TheBucket)) 164 return std::make_pair(iterator(TheBucket, Buckets+NumBuckets), 165 false); // Already in map. 166 167 // Otherwise, insert the new element. 168 TheBucket = InsertIntoBucket(KV.first, KV.second, TheBucket); 169 return std::make_pair(iterator(TheBucket, Buckets+NumBuckets), 170 true); 171 } 172 173 /// insert - Range insertion of pairs. 174 template<typename InputIt> 175 void insert(InputIt I, InputIt E) { 176 for (; I != E; ++I) 177 insert(*I); 178 } 179 180 181 bool erase(const KeyT &Val) { 182 BucketT *TheBucket; 183 if (!LookupBucketFor(Val, TheBucket)) 184 return false; // not in map. 185 186 TheBucket->second.~ValueT(); 187 TheBucket->first = getTombstoneKey(); 188 --NumEntries; 189 ++NumTombstones; 190 return true; 191 } 192 void erase(iterator I) { 193 BucketT *TheBucket = &*I; 194 TheBucket->second.~ValueT(); 195 TheBucket->first = getTombstoneKey(); 196 --NumEntries; 197 ++NumTombstones; 198 } 199 200 void swap(DenseMap& RHS) { 201 std::swap(NumBuckets, RHS.NumBuckets); 202 std::swap(Buckets, RHS.Buckets); 203 std::swap(NumEntries, RHS.NumEntries); 204 std::swap(NumTombstones, RHS.NumTombstones); 205 } 206 207 value_type& FindAndConstruct(const KeyT &Key) { 208 BucketT *TheBucket; 209 if (LookupBucketFor(Key, TheBucket)) 210 return *TheBucket; 211 212 return *InsertIntoBucket(Key, ValueT(), TheBucket); 213 } 214 215 ValueT &operator[](const KeyT &Key) { 216 return FindAndConstruct(Key).second; 217 } 218 219 DenseMap& operator=(const DenseMap& other) { 220 CopyFrom(other); 221 return *this; 222 } 223 224 /// isPointerIntoBucketsArray - Return true if the specified pointer points 225 /// somewhere into the DenseMap's array of buckets (i.e. either to a key or 226 /// value in the DenseMap). 227 bool isPointerIntoBucketsArray(const void *Ptr) const { 228 return Ptr >= Buckets && Ptr < Buckets+NumBuckets; 229 } 230 231 /// getPointerIntoBucketsArray() - Return an opaque pointer into the buckets 232 /// array. In conjunction with the previous method, this can be used to 233 /// determine whether an insertion caused the DenseMap to reallocate. 234 const void *getPointerIntoBucketsArray() const { return Buckets; } 235 236private: 237 void CopyFrom(const DenseMap& other) { 238 if (NumBuckets != 0 && 239 (!isPodLike<KeyInfoT>::value || !isPodLike<ValueInfoT>::value)) { 240 const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey(); 241 for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) { 242 if (!KeyInfoT::isEqual(P->first, EmptyKey) && 243 !KeyInfoT::isEqual(P->first, TombstoneKey)) 244 P->second.~ValueT(); 245 P->first.~KeyT(); 246 } 247 } 248 249 NumEntries = other.NumEntries; 250 NumTombstones = other.NumTombstones; 251 252 if (NumBuckets) { 253#ifndef NDEBUG 254 memset(Buckets, 0x5a, sizeof(BucketT)*NumBuckets); 255#endif 256 operator delete(Buckets); 257 } 258 259 NumBuckets = other.NumBuckets; 260 261 if (NumBuckets == 0) { 262 Buckets = 0; 263 return; 264 } 265 266 Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT) * NumBuckets)); 267 268 if (isPodLike<KeyInfoT>::value && isPodLike<ValueInfoT>::value) 269 memcpy(Buckets, other.Buckets, NumBuckets * sizeof(BucketT)); 270 else 271 for (size_t i = 0; i < NumBuckets; ++i) { 272 new (&Buckets[i].first) KeyT(other.Buckets[i].first); 273 if (!KeyInfoT::isEqual(Buckets[i].first, getEmptyKey()) && 274 !KeyInfoT::isEqual(Buckets[i].first, getTombstoneKey())) 275 new (&Buckets[i].second) ValueT(other.Buckets[i].second); 276 } 277 } 278 279 BucketT *InsertIntoBucket(const KeyT &Key, const ValueT &Value, 280 BucketT *TheBucket) { 281 // If the load of the hash table is more than 3/4, or if fewer than 1/8 of 282 // the buckets are empty (meaning that many are filled with tombstones), 283 // grow the table. 284 // 285 // The later case is tricky. For example, if we had one empty bucket with 286 // tons of tombstones, failing lookups (e.g. for insertion) would have to 287 // probe almost the entire table until it found the empty bucket. If the 288 // table completely filled with tombstones, no lookup would ever succeed, 289 // causing infinite loops in lookup. 290 ++NumEntries; 291 if (NumEntries*4 >= NumBuckets*3 || 292 NumBuckets-(NumEntries+NumTombstones) < NumBuckets/8) { 293 this->grow(NumBuckets * 2); 294 LookupBucketFor(Key, TheBucket); 295 } 296 297 // If we are writing over a tombstone, remember this. 298 if (!KeyInfoT::isEqual(TheBucket->first, getEmptyKey())) 299 --NumTombstones; 300 301 TheBucket->first = Key; 302 new (&TheBucket->second) ValueT(Value); 303 return TheBucket; 304 } 305 306 static unsigned getHashValue(const KeyT &Val) { 307 return KeyInfoT::getHashValue(Val); 308 } 309 static const KeyT getEmptyKey() { 310 return KeyInfoT::getEmptyKey(); 311 } 312 static const KeyT getTombstoneKey() { 313 return KeyInfoT::getTombstoneKey(); 314 } 315 316 /// LookupBucketFor - Lookup the appropriate bucket for Val, returning it in 317 /// FoundBucket. If the bucket contains the key and a value, this returns 318 /// true, otherwise it returns a bucket with an empty marker or tombstone and 319 /// returns false. 320 bool LookupBucketFor(const KeyT &Val, BucketT *&FoundBucket) const { 321 unsigned BucketNo = getHashValue(Val); 322 unsigned ProbeAmt = 1; 323 BucketT *BucketsPtr = Buckets; 324 325 if (NumBuckets == 0) { 326 FoundBucket = 0; 327 return false; 328 } 329 330 // FoundTombstone - Keep track of whether we find a tombstone while probing. 331 BucketT *FoundTombstone = 0; 332 const KeyT EmptyKey = getEmptyKey(); 333 const KeyT TombstoneKey = getTombstoneKey(); 334 assert(!KeyInfoT::isEqual(Val, EmptyKey) && 335 !KeyInfoT::isEqual(Val, TombstoneKey) && 336 "Empty/Tombstone value shouldn't be inserted into map!"); 337 338 while (1) { 339 BucketT *ThisBucket = BucketsPtr + (BucketNo & (NumBuckets-1)); 340 // Found Val's bucket? If so, return it. 341 if (KeyInfoT::isEqual(ThisBucket->first, Val)) { 342 FoundBucket = ThisBucket; 343 return true; 344 } 345 346 // If we found an empty bucket, the key doesn't exist in the set. 347 // Insert it and return the default value. 348 if (KeyInfoT::isEqual(ThisBucket->first, EmptyKey)) { 349 // If we've already seen a tombstone while probing, fill it in instead 350 // of the empty bucket we eventually probed to. 351 if (FoundTombstone) ThisBucket = FoundTombstone; 352 FoundBucket = FoundTombstone ? FoundTombstone : ThisBucket; 353 return false; 354 } 355 356 // If this is a tombstone, remember it. If Val ends up not in the map, we 357 // prefer to return it than something that would require more probing. 358 if (KeyInfoT::isEqual(ThisBucket->first, TombstoneKey) && !FoundTombstone) 359 FoundTombstone = ThisBucket; // Remember the first tombstone found. 360 361 // Otherwise, it's a hash collision or a tombstone, continue quadratic 362 // probing. 363 BucketNo += ProbeAmt++; 364 } 365 } 366 367 void init(unsigned InitBuckets) { 368 NumEntries = 0; 369 NumTombstones = 0; 370 NumBuckets = InitBuckets; 371 372 if (InitBuckets == 0) { 373 Buckets = 0; 374 return; 375 } 376 377 assert(InitBuckets && (InitBuckets & (InitBuckets-1)) == 0 && 378 "# initial buckets must be a power of two!"); 379 Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT)*InitBuckets)); 380 // Initialize all the keys to EmptyKey. 381 const KeyT EmptyKey = getEmptyKey(); 382 for (unsigned i = 0; i != InitBuckets; ++i) 383 new (&Buckets[i].first) KeyT(EmptyKey); 384 } 385 386 void grow(unsigned AtLeast) { 387 unsigned OldNumBuckets = NumBuckets; 388 BucketT *OldBuckets = Buckets; 389 390 if (NumBuckets < 64) 391 NumBuckets = 64; 392 393 // Double the number of buckets. 394 while (NumBuckets < AtLeast) 395 NumBuckets <<= 1; 396 NumTombstones = 0; 397 Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT)*NumBuckets)); 398 399 // Initialize all the keys to EmptyKey. 400 const KeyT EmptyKey = getEmptyKey(); 401 for (unsigned i = 0, e = NumBuckets; i != e; ++i) 402 new (&Buckets[i].first) KeyT(EmptyKey); 403 404 // Insert all the old elements. 405 const KeyT TombstoneKey = getTombstoneKey(); 406 for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) { 407 if (!KeyInfoT::isEqual(B->first, EmptyKey) && 408 !KeyInfoT::isEqual(B->first, TombstoneKey)) { 409 // Insert the key/value into the new table. 410 BucketT *DestBucket; 411 bool FoundVal = LookupBucketFor(B->first, DestBucket); 412 (void)FoundVal; // silence warning. 413 assert(!FoundVal && "Key already in new map?"); 414 DestBucket->first = B->first; 415 new (&DestBucket->second) ValueT(B->second); 416 417 // Free the value. 418 B->second.~ValueT(); 419 } 420 B->first.~KeyT(); 421 } 422 423#ifndef NDEBUG 424 memset(OldBuckets, 0x5a, sizeof(BucketT)*OldNumBuckets); 425#endif 426 // Free the old table. 427 operator delete(OldBuckets); 428 } 429 430 void shrink_and_clear() { 431 unsigned OldNumBuckets = NumBuckets; 432 BucketT *OldBuckets = Buckets; 433 434 // Reduce the number of buckets. 435 NumBuckets = NumEntries > 32 ? 1 << (Log2_32_Ceil(NumEntries) + 1) 436 : 64; 437 NumTombstones = 0; 438 Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT)*NumBuckets)); 439 440 // Initialize all the keys to EmptyKey. 441 const KeyT EmptyKey = getEmptyKey(); 442 for (unsigned i = 0, e = NumBuckets; i != e; ++i) 443 new (&Buckets[i].first) KeyT(EmptyKey); 444 445 // Free the old buckets. 446 const KeyT TombstoneKey = getTombstoneKey(); 447 for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) { 448 if (!KeyInfoT::isEqual(B->first, EmptyKey) && 449 !KeyInfoT::isEqual(B->first, TombstoneKey)) { 450 // Free the value. 451 B->second.~ValueT(); 452 } 453 B->first.~KeyT(); 454 } 455 456#ifndef NDEBUG 457 memset(OldBuckets, 0x5a, sizeof(BucketT)*OldNumBuckets); 458#endif 459 // Free the old table. 460 operator delete(OldBuckets); 461 462 NumEntries = 0; 463 } 464}; 465 466template<typename KeyT, typename ValueT, 467 typename KeyInfoT, typename ValueInfoT, bool IsConst> 468class DenseMapIterator { 469 typedef std::pair<KeyT, ValueT> Bucket; 470 typedef DenseMapIterator<KeyT, ValueT, 471 KeyInfoT, ValueInfoT, true> ConstIterator; 472 friend class DenseMapIterator<KeyT, ValueT, KeyInfoT, ValueInfoT, true>; 473public: 474 typedef ptrdiff_t difference_type; 475 typedef typename conditional<IsConst, const Bucket, Bucket>::type value_type; 476 typedef value_type *pointer; 477 typedef value_type &reference; 478 typedef std::forward_iterator_tag iterator_category; 479private: 480 pointer Ptr, End; 481public: 482 DenseMapIterator() : Ptr(0), End(0) {} 483 484 DenseMapIterator(pointer Pos, pointer E) : Ptr(Pos), End(E) { 485 AdvancePastEmptyBuckets(); 486 } 487 488 // If IsConst is true this is a converting constructor from iterator to 489 // const_iterator and the default copy constructor is used. 490 // Otherwise this is a copy constructor for iterator. 491 DenseMapIterator(const DenseMapIterator<KeyT, ValueT, 492 KeyInfoT, ValueInfoT, false>& I) 493 : Ptr(I.Ptr), End(I.End) {} 494 495 reference operator*() const { 496 return *Ptr; 497 } 498 pointer operator->() const { 499 return Ptr; 500 } 501 502 bool operator==(const ConstIterator &RHS) const { 503 return Ptr == RHS.operator->(); 504 } 505 bool operator!=(const ConstIterator &RHS) const { 506 return Ptr != RHS.operator->(); 507 } 508 509 inline DenseMapIterator& operator++() { // Preincrement 510 ++Ptr; 511 AdvancePastEmptyBuckets(); 512 return *this; 513 } 514 DenseMapIterator operator++(int) { // Postincrement 515 DenseMapIterator tmp = *this; ++*this; return tmp; 516 } 517 518private: 519 void AdvancePastEmptyBuckets() { 520 const KeyT Empty = KeyInfoT::getEmptyKey(); 521 const KeyT Tombstone = KeyInfoT::getTombstoneKey(); 522 523 while (Ptr != End && 524 (KeyInfoT::isEqual(Ptr->first, Empty) || 525 KeyInfoT::isEqual(Ptr->first, Tombstone))) 526 ++Ptr; 527 } 528}; 529 530} // end namespace llvm 531 532#endif 533