DenseMap.h revision 345b378309eabd74a7a43f095dca9a4894bc371e
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 <iterator> 22#include <new> 23#include <utility> 24#include <cassert> 25#include <cstddef> 26#include <cstring> 27 28namespace llvm { 29 30template<typename KeyT, typename ValueT, 31 typename KeyInfoT = DenseMapInfo<KeyT>, 32 typename ValueInfoT = DenseMapInfo<ValueT>, bool IsConst = false> 33class DenseMapIterator; 34 35template<typename KeyT, typename ValueT, 36 typename KeyInfoT = DenseMapInfo<KeyT>, 37 typename ValueInfoT = DenseMapInfo<ValueT> > 38class DenseMap { 39 typedef std::pair<KeyT, ValueT> BucketT; 40 unsigned NumBuckets; 41 BucketT *Buckets; 42 43 unsigned NumEntries; 44 unsigned NumTombstones; 45public: 46 typedef KeyT key_type; 47 typedef ValueT mapped_type; 48 typedef BucketT value_type; 49 50 DenseMap(const DenseMap &other) { 51 NumBuckets = 0; 52 CopyFrom(other); 53 } 54 55 explicit DenseMap(unsigned NumInitBuckets = 64) { 56 init(NumInitBuckets); 57 } 58 59 template<typename InputIt> 60 DenseMap(const InputIt &I, const InputIt &E) { 61 init(64); 62 insert(I, E); 63 } 64 65 ~DenseMap() { 66 const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey(); 67 for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) { 68 if (!KeyInfoT::isEqual(P->first, EmptyKey) && 69 !KeyInfoT::isEqual(P->first, TombstoneKey)) 70 P->second.~ValueT(); 71 P->first.~KeyT(); 72 } 73#ifndef NDEBUG 74 memset(Buckets, 0x5a, sizeof(BucketT)*NumBuckets); 75#endif 76 operator delete(Buckets); 77 } 78 79 typedef DenseMapIterator<KeyT, ValueT, KeyInfoT> iterator; 80 typedef DenseMapIterator<KeyT, ValueT, 81 KeyInfoT, ValueInfoT, true> const_iterator; 82 inline iterator begin() { 83 // When the map is empty, avoid the overhead of AdvancePastEmptyBuckets(). 84 return empty() ? end() : iterator(Buckets, Buckets+NumBuckets); 85 } 86 inline iterator end() { 87 return iterator(Buckets+NumBuckets, Buckets+NumBuckets); 88 } 89 inline const_iterator begin() const { 90 return empty() ? end() : const_iterator(Buckets, Buckets+NumBuckets); 91 } 92 inline const_iterator end() const { 93 return const_iterator(Buckets+NumBuckets, Buckets+NumBuckets); 94 } 95 96 bool empty() const { return NumEntries == 0; } 97 unsigned size() const { return NumEntries; } 98 99 /// Grow the densemap so that it has at least Size buckets. Does not shrink 100 void resize(size_t Size) { grow(Size); } 101 102 void clear() { 103 if (NumEntries == 0 && NumTombstones == 0) return; 104 105 // If the capacity of the array is huge, and the # elements used is small, 106 // shrink the array. 107 if (NumEntries * 4 < NumBuckets && NumBuckets > 64) { 108 shrink_and_clear(); 109 return; 110 } 111 112 const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey(); 113 for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) { 114 if (!KeyInfoT::isEqual(P->first, EmptyKey)) { 115 if (!KeyInfoT::isEqual(P->first, TombstoneKey)) { 116 P->second.~ValueT(); 117 --NumEntries; 118 } 119 P->first = EmptyKey; 120 } 121 } 122 assert(NumEntries == 0 && "Node count imbalance!"); 123 NumTombstones = 0; 124 } 125 126 /// count - Return true if the specified key is in the map. 127 bool count(const KeyT &Val) const { 128 BucketT *TheBucket; 129 return LookupBucketFor(Val, TheBucket); 130 } 131 132 iterator find(const KeyT &Val) { 133 BucketT *TheBucket; 134 if (LookupBucketFor(Val, TheBucket)) 135 return iterator(TheBucket, Buckets+NumBuckets); 136 return end(); 137 } 138 const_iterator find(const KeyT &Val) const { 139 BucketT *TheBucket; 140 if (LookupBucketFor(Val, TheBucket)) 141 return const_iterator(TheBucket, Buckets+NumBuckets); 142 return end(); 143 } 144 145 /// lookup - Return the entry for the specified key, or a default 146 /// constructed value if no such entry exists. 147 ValueT lookup(const KeyT &Val) const { 148 BucketT *TheBucket; 149 if (LookupBucketFor(Val, TheBucket)) 150 return TheBucket->second; 151 return ValueT(); 152 } 153 154 // Inserts key,value pair into the map if the key isn't already in the map. 155 // If the key is already in the map, it returns false and doesn't update the 156 // value. 157 std::pair<iterator, bool> insert(const std::pair<KeyT, ValueT> &KV) { 158 BucketT *TheBucket; 159 if (LookupBucketFor(KV.first, TheBucket)) 160 return std::make_pair(iterator(TheBucket, Buckets+NumBuckets), 161 false); // Already in map. 162 163 // Otherwise, insert the new element. 164 TheBucket = InsertIntoBucket(KV.first, KV.second, TheBucket); 165 return std::make_pair(iterator(TheBucket, Buckets+NumBuckets), 166 true); 167 } 168 169 /// insert - Range insertion of pairs. 170 template<typename InputIt> 171 void insert(InputIt I, InputIt E) { 172 for (; I != E; ++I) 173 insert(*I); 174 } 175 176 177 bool erase(const KeyT &Val) { 178 BucketT *TheBucket; 179 if (!LookupBucketFor(Val, TheBucket)) 180 return false; // not in map. 181 182 TheBucket->second.~ValueT(); 183 TheBucket->first = getTombstoneKey(); 184 --NumEntries; 185 ++NumTombstones; 186 return true; 187 } 188 bool erase(iterator I) { 189 BucketT *TheBucket = &*I; 190 TheBucket->second.~ValueT(); 191 TheBucket->first = getTombstoneKey(); 192 --NumEntries; 193 ++NumTombstones; 194 return true; 195 } 196 197 void swap(DenseMap& RHS) { 198 std::swap(NumBuckets, RHS.NumBuckets); 199 std::swap(Buckets, RHS.Buckets); 200 std::swap(NumEntries, RHS.NumEntries); 201 std::swap(NumTombstones, RHS.NumTombstones); 202 } 203 204 value_type& FindAndConstruct(const KeyT &Key) { 205 BucketT *TheBucket; 206 if (LookupBucketFor(Key, TheBucket)) 207 return *TheBucket; 208 209 return *InsertIntoBucket(Key, ValueT(), TheBucket); 210 } 211 212 ValueT &operator[](const KeyT &Key) { 213 return FindAndConstruct(Key).second; 214 } 215 216 DenseMap& operator=(const DenseMap& other) { 217 CopyFrom(other); 218 return *this; 219 } 220 221 /// isPointerIntoBucketsArray - Return true if the specified pointer points 222 /// somewhere into the DenseMap's array of buckets (i.e. either to a key or 223 /// value in the DenseMap). 224 bool isPointerIntoBucketsArray(const void *Ptr) const { 225 return Ptr >= Buckets && Ptr < Buckets+NumBuckets; 226 } 227 228 /// getPointerIntoBucketsArray() - Return an opaque pointer into the buckets 229 /// array. In conjunction with the previous method, this can be used to 230 /// determine whether an insertion caused the DenseMap to reallocate. 231 const void *getPointerIntoBucketsArray() const { return Buckets; } 232 233private: 234 void CopyFrom(const DenseMap& other) { 235 if (NumBuckets != 0 && 236 (!isPodLike<KeyInfoT>::value || !isPodLike<ValueInfoT>::value)) { 237 const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey(); 238 for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) { 239 if (!KeyInfoT::isEqual(P->first, EmptyKey) && 240 !KeyInfoT::isEqual(P->first, TombstoneKey)) 241 P->second.~ValueT(); 242 P->first.~KeyT(); 243 } 244 } 245 246 NumEntries = other.NumEntries; 247 NumTombstones = other.NumTombstones; 248 249 if (NumBuckets) { 250#ifndef NDEBUG 251 memset(Buckets, 0x5a, sizeof(BucketT)*NumBuckets); 252#endif 253 operator delete(Buckets); 254 } 255 Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT) * 256 other.NumBuckets)); 257 258 if (isPodLike<KeyInfoT>::value && isPodLike<ValueInfoT>::value) 259 memcpy(Buckets, other.Buckets, other.NumBuckets * sizeof(BucketT)); 260 else 261 for (size_t i = 0; i < other.NumBuckets; ++i) { 262 new (&Buckets[i].first) KeyT(other.Buckets[i].first); 263 if (!KeyInfoT::isEqual(Buckets[i].first, getEmptyKey()) && 264 !KeyInfoT::isEqual(Buckets[i].first, getTombstoneKey())) 265 new (&Buckets[i].second) ValueT(other.Buckets[i].second); 266 } 267 NumBuckets = other.NumBuckets; 268 } 269 270 BucketT *InsertIntoBucket(const KeyT &Key, const ValueT &Value, 271 BucketT *TheBucket) { 272 // If the load of the hash table is more than 3/4, or if fewer than 1/8 of 273 // the buckets are empty (meaning that many are filled with tombstones), 274 // grow the table. 275 // 276 // The later case is tricky. For example, if we had one empty bucket with 277 // tons of tombstones, failing lookups (e.g. for insertion) would have to 278 // probe almost the entire table until it found the empty bucket. If the 279 // table completely filled with tombstones, no lookup would ever succeed, 280 // causing infinite loops in lookup. 281 ++NumEntries; 282 if (NumEntries*4 >= NumBuckets*3 || 283 NumBuckets-(NumEntries+NumTombstones) < NumBuckets/8) { 284 this->grow(NumBuckets * 2); 285 LookupBucketFor(Key, TheBucket); 286 } 287 288 // If we are writing over a tombstone, remember this. 289 if (!KeyInfoT::isEqual(TheBucket->first, getEmptyKey())) 290 --NumTombstones; 291 292 TheBucket->first = Key; 293 new (&TheBucket->second) ValueT(Value); 294 return TheBucket; 295 } 296 297 static unsigned getHashValue(const KeyT &Val) { 298 return KeyInfoT::getHashValue(Val); 299 } 300 static const KeyT getEmptyKey() { 301 return KeyInfoT::getEmptyKey(); 302 } 303 static const KeyT getTombstoneKey() { 304 return KeyInfoT::getTombstoneKey(); 305 } 306 307 /// LookupBucketFor - Lookup the appropriate bucket for Val, returning it in 308 /// FoundBucket. If the bucket contains the key and a value, this returns 309 /// true, otherwise it returns a bucket with an empty marker or tombstone and 310 /// returns false. 311 bool LookupBucketFor(const KeyT &Val, BucketT *&FoundBucket) const { 312 unsigned BucketNo = getHashValue(Val); 313 unsigned ProbeAmt = 1; 314 BucketT *BucketsPtr = Buckets; 315 316 // FoundTombstone - Keep track of whether we find a tombstone while probing. 317 BucketT *FoundTombstone = 0; 318 const KeyT EmptyKey = getEmptyKey(); 319 const KeyT TombstoneKey = getTombstoneKey(); 320 assert(!KeyInfoT::isEqual(Val, EmptyKey) && 321 !KeyInfoT::isEqual(Val, TombstoneKey) && 322 "Empty/Tombstone value shouldn't be inserted into map!"); 323 324 while (1) { 325 BucketT *ThisBucket = BucketsPtr + (BucketNo & (NumBuckets-1)); 326 // Found Val's bucket? If so, return it. 327 if (KeyInfoT::isEqual(ThisBucket->first, Val)) { 328 FoundBucket = ThisBucket; 329 return true; 330 } 331 332 // If we found an empty bucket, the key doesn't exist in the set. 333 // Insert it and return the default value. 334 if (KeyInfoT::isEqual(ThisBucket->first, EmptyKey)) { 335 // If we've already seen a tombstone while probing, fill it in instead 336 // of the empty bucket we eventually probed to. 337 if (FoundTombstone) ThisBucket = FoundTombstone; 338 FoundBucket = FoundTombstone ? FoundTombstone : ThisBucket; 339 return false; 340 } 341 342 // If this is a tombstone, remember it. If Val ends up not in the map, we 343 // prefer to return it than something that would require more probing. 344 if (KeyInfoT::isEqual(ThisBucket->first, TombstoneKey) && !FoundTombstone) 345 FoundTombstone = ThisBucket; // Remember the first tombstone found. 346 347 // Otherwise, it's a hash collision or a tombstone, continue quadratic 348 // probing. 349 BucketNo += ProbeAmt++; 350 } 351 } 352 353 void init(unsigned InitBuckets) { 354 NumEntries = 0; 355 NumTombstones = 0; 356 NumBuckets = InitBuckets; 357 assert(InitBuckets && (InitBuckets & (InitBuckets-1)) == 0 && 358 "# initial buckets must be a power of two!"); 359 Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT)*InitBuckets)); 360 // Initialize all the keys to EmptyKey. 361 const KeyT EmptyKey = getEmptyKey(); 362 for (unsigned i = 0; i != InitBuckets; ++i) 363 new (&Buckets[i].first) KeyT(EmptyKey); 364 } 365 366 void grow(unsigned AtLeast) { 367 unsigned OldNumBuckets = NumBuckets; 368 BucketT *OldBuckets = Buckets; 369 370 // Double the number of buckets. 371 while (NumBuckets < AtLeast) 372 NumBuckets <<= 1; 373 NumTombstones = 0; 374 Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT)*NumBuckets)); 375 376 // Initialize all the keys to EmptyKey. 377 const KeyT EmptyKey = getEmptyKey(); 378 for (unsigned i = 0, e = NumBuckets; i != e; ++i) 379 new (&Buckets[i].first) KeyT(EmptyKey); 380 381 // Insert all the old elements. 382 const KeyT TombstoneKey = getTombstoneKey(); 383 for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) { 384 if (!KeyInfoT::isEqual(B->first, EmptyKey) && 385 !KeyInfoT::isEqual(B->first, TombstoneKey)) { 386 // Insert the key/value into the new table. 387 BucketT *DestBucket; 388 bool FoundVal = LookupBucketFor(B->first, DestBucket); 389 FoundVal = FoundVal; // silence warning. 390 assert(!FoundVal && "Key already in new map?"); 391 DestBucket->first = B->first; 392 new (&DestBucket->second) ValueT(B->second); 393 394 // Free the value. 395 B->second.~ValueT(); 396 } 397 B->first.~KeyT(); 398 } 399 400#ifndef NDEBUG 401 memset(OldBuckets, 0x5a, sizeof(BucketT)*OldNumBuckets); 402#endif 403 // Free the old table. 404 operator delete(OldBuckets); 405 } 406 407 void shrink_and_clear() { 408 unsigned OldNumBuckets = NumBuckets; 409 BucketT *OldBuckets = Buckets; 410 411 // Reduce the number of buckets. 412 NumBuckets = NumEntries > 32 ? 1 << (Log2_32_Ceil(NumEntries) + 1) 413 : 64; 414 NumTombstones = 0; 415 Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT)*NumBuckets)); 416 417 // Initialize all the keys to EmptyKey. 418 const KeyT EmptyKey = getEmptyKey(); 419 for (unsigned i = 0, e = NumBuckets; i != e; ++i) 420 new (&Buckets[i].first) KeyT(EmptyKey); 421 422 // Free the old buckets. 423 const KeyT TombstoneKey = getTombstoneKey(); 424 for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) { 425 if (!KeyInfoT::isEqual(B->first, EmptyKey) && 426 !KeyInfoT::isEqual(B->first, TombstoneKey)) { 427 // Free the value. 428 B->second.~ValueT(); 429 } 430 B->first.~KeyT(); 431 } 432 433#ifndef NDEBUG 434 memset(OldBuckets, 0x5a, sizeof(BucketT)*OldNumBuckets); 435#endif 436 // Free the old table. 437 operator delete(OldBuckets); 438 439 NumEntries = 0; 440 } 441}; 442 443template<typename KeyT, typename ValueT, 444 typename KeyInfoT, typename ValueInfoT, bool IsConst> 445class DenseMapIterator { 446 typedef std::pair<KeyT, ValueT> Bucket; 447 typedef DenseMapIterator<KeyT, ValueT, 448 KeyInfoT, ValueInfoT, true> ConstIterator; 449 friend class DenseMapIterator<KeyT, ValueT, KeyInfoT, ValueInfoT, true>; 450public: 451 typedef ptrdiff_t difference_type; 452 typedef typename conditional<IsConst, const Bucket, Bucket>::type value_type; 453 typedef value_type *pointer; 454 typedef value_type &reference; 455 typedef std::forward_iterator_tag iterator_category; 456private: 457 pointer Ptr, End; 458public: 459 DenseMapIterator() : Ptr(0), End(0) {} 460 461 DenseMapIterator(pointer Pos, pointer E) : Ptr(Pos), End(E) { 462 AdvancePastEmptyBuckets(); 463 } 464 465 // If IsConst is true this is a converting constructor from iterator to 466 // const_iterator and the default copy constructor is used. 467 // Otherwise this is a copy constructor for iterator. 468 DenseMapIterator(const DenseMapIterator<KeyT, ValueT, 469 KeyInfoT, ValueInfoT, false>& I) 470 : Ptr(I.Ptr), End(I.End) {} 471 472 reference operator*() const { 473 return *Ptr; 474 } 475 pointer operator->() const { 476 return Ptr; 477 } 478 479 bool operator==(const ConstIterator &RHS) const { 480 return Ptr == RHS.operator->(); 481 } 482 bool operator!=(const ConstIterator &RHS) const { 483 return Ptr != RHS.operator->(); 484 } 485 486 inline DenseMapIterator& operator++() { // Preincrement 487 ++Ptr; 488 AdvancePastEmptyBuckets(); 489 return *this; 490 } 491 DenseMapIterator operator++(int) { // Postincrement 492 DenseMapIterator tmp = *this; ++*this; return tmp; 493 } 494 495private: 496 void AdvancePastEmptyBuckets() { 497 const KeyT Empty = KeyInfoT::getEmptyKey(); 498 const KeyT Tombstone = KeyInfoT::getTombstoneKey(); 499 500 while (Ptr != End && 501 (KeyInfoT::isEqual(Ptr->first, Empty) || 502 KeyInfoT::isEqual(Ptr->first, Tombstone))) 503 ++Ptr; 504 } 505}; 506 507} // end namespace llvm 508 509#endif 510