include/llvm/ADT/DenseMap.h

   1 //===- llvm/ADT/DenseMap.h - Dense probed hash table ------------*- 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 // This file defines the DenseMap class.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #ifndef LLVM_ADT_DENSEMAP_H
  14 #define LLVM_ADT_DENSEMAP_H
  15
  16 #include "llvm/ADT/DenseMapInfo.h"
  17 #include "llvm/ADT/EpochTracker.h"
  18 #include "llvm/Support/AlignOf.h"
  19 #include "llvm/Support/Compiler.h"
  20 #include "llvm/Support/MathExtras.h"
  21 #include "llvm/Support/ReverseIteration.h"
  22 #include "llvm/Support/type_traits.h"
  23 #include <algorithm>
  24 #include <cassert>
  25 #include <cstddef>
  26 #include <cstring>
  27 #include <initializer_list>
  28 #include <iterator>
  29 #include <new>
  30 #include <type_traits>
  31 #include <utility>
  32
  33 namespace llvm {
  34
  35 namespace detail {
  36
  37 // We extend a pair to allow users to override the bucket type with their own
  38 // implementation without requiring two members.
  39 template <typename KeyT, typename ValueT>
  40 struct DenseMapPair : public std::pair<KeyT, ValueT> {
  41   using std::pair<KeyT, ValueT>::pair;
  42
  43   KeyT &getFirst() { return std::pair<KeyT, ValueT>::first; }
  44   const KeyT &getFirst() const { return std::pair<KeyT, ValueT>::first; }
  45   ValueT &getSecond() { return std::pair<KeyT, ValueT>::second; }
  46   const ValueT &getSecond() const { return std::pair<KeyT, ValueT>::second; }
  47 };
  48
  49 } // end namespace detail
  50
  51 template <typename KeyT, typename ValueT,
  52           typename KeyInfoT = DenseMapInfo<KeyT>,
  53           typename Bucket = llvm::detail::DenseMapPair<KeyT, ValueT>,
  54           bool IsConst = false>
  55 class DenseMapIterator;
  56
  57 template <typename DerivedT, typename KeyT, typename ValueT, typename KeyInfoT,
  58           typename BucketT>
  59 class DenseMapBase : public DebugEpochBase {
  60   template <typename T>
  61   using const_arg_type_t = typename const_pointer_or_const_ref<T>::type;
  62
  63 public:
  64   using size_type = unsigned;
  65   using key_type = KeyT;
  66   using mapped_type = ValueT;
  67   using value_type = BucketT;
  68
  69   using iterator = DenseMapIterator<KeyT, ValueT, KeyInfoT, BucketT>;
  70   using const_iterator =
  71       DenseMapIterator<KeyT, ValueT, KeyInfoT, BucketT, true>;
  72
  73   inline iterator begin() {
  74     // When the map is empty, avoid the overhead of advancing/retreating past
  75     // empty buckets.
  76     if (empty())
  77       return end();
  78     if (shouldReverseIterate<KeyT>())
  79       return makeIterator(getBucketsEnd() - 1, getBuckets(), *this);
  80     return makeIterator(getBuckets(), getBucketsEnd(), *this);
  81   }
  82   inline iterator end() {
  83     return makeIterator(getBucketsEnd(), getBucketsEnd(), *this, true);
  84   }
  85   inline const_iterator begin() const {
  86     if (empty())
  87       return end();
  88     if (shouldReverseIterate<KeyT>())
  89       return makeConstIterator(getBucketsEnd() - 1, getBuckets(), *this);
  90     return makeConstIterator(getBuckets(), getBucketsEnd(), *this);
  91   }
  92   inline const_iterator end() const {
  93     return makeConstIterator(getBucketsEnd(), getBucketsEnd(), *this, true);
  94   }
  95
  96   LLVM_NODISCARD bool empty() const {
  97     return getNumEntries() == 0;
  98   }
  99   unsigned size() const { return getNumEntries(); }
 100
 101   /// Grow the densemap so that it can contain at least \p NumEntries items
 102   /// before resizing again.
 103   void reserve(size_type NumEntries) {
 104     auto NumBuckets = getMinBucketToReserveForEntries(NumEntries);
 105     incrementEpoch();
 106     if (NumBuckets > getNumBuckets())
 107       grow(NumBuckets);
 108   }
 109
 110   void clear() {
 111     incrementEpoch();
 112     if (getNumEntries() == 0 && getNumTombstones() == 0) return;
 113
 114     // If the capacity of the array is huge, and the # elements used is small,
 115     // shrink the array.
 116     if (getNumEntries() * 4 < getNumBuckets() && getNumBuckets() > 64) {
 117       shrink_and_clear();
 118       return;
 119     }
 120
 121     const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
 122     if (is_trivially_copyable<KeyT>::value &&
 123         is_trivially_copyable<ValueT>::value) {
 124       // Use a simpler loop when these are trivial types.
 125       for (BucketT *P = getBuckets(), *E = getBucketsEnd(); P != E; ++P)
 126         P->getFirst() = EmptyKey;
 127     } else {
 128       unsigned NumEntries = getNumEntries();
 129       for (BucketT *P = getBuckets(), *E = getBucketsEnd(); P != E; ++P) {
 130         if (!KeyInfoT::isEqual(P->getFirst(), EmptyKey)) {
 131           if (!KeyInfoT::isEqual(P->getFirst(), TombstoneKey)) {
 132             P->getSecond().~ValueT();
 133             --NumEntries;
 134           }
 135           P->getFirst() = EmptyKey;
 136         }
 137       }
 138       assert(NumEntries == 0 && "Node count imbalance!");
 139     }
 140     setNumEntries(0);
 141     setNumTombstones(0);
 142   }
 143
 144   /// Return 1 if the specified key is in the map, 0 otherwise.
 145   size_type count(const_arg_type_t<KeyT> Val) const {
 146     const BucketT *TheBucket;
 147     return LookupBucketFor(Val, TheBucket) ? 1 : 0;
 148   }
 149
 150   iterator find(const_arg_type_t<KeyT> Val) {
 151     BucketT *TheBucket;
 152     if (LookupBucketFor(Val, TheBucket))
 153       return makeIterator(TheBucket, getBucketsEnd(), *this, true);
 154     return end();
 155   }
 156   const_iterator find(const_arg_type_t<KeyT> Val) const {
 157     const BucketT *TheBucket;
 158     if (LookupBucketFor(Val, TheBucket))
 159       return makeConstIterator(TheBucket, getBucketsEnd(), *this, true);
 160     return end();
 161   }
 162
 163   /// Alternate version of find() which allows a different, and possibly
 164   /// less expensive, key type.
 165   /// The DenseMapInfo is responsible for supplying methods
 166   /// getHashValue(LookupKeyT) and isEqual(LookupKeyT, KeyT) for each key
 167   /// type used.
 168   template<class LookupKeyT>
 169   iterator find_as(const LookupKeyT &Val) {
 170     BucketT *TheBucket;
 171     if (LookupBucketFor(Val, TheBucket))
 172       return makeIterator(TheBucket, getBucketsEnd(), *this, true);
 173     return end();
 174   }
 175   template<class LookupKeyT>
 176   const_iterator find_as(const LookupKeyT &Val) const {
 177     const BucketT *TheBucket;
 178     if (LookupBucketFor(Val, TheBucket))
 179       return makeConstIterator(TheBucket, getBucketsEnd(), *this, true);
 180     return end();
 181   }
 182
 183   /// lookup - Return the entry for the specified key, or a default
 184   /// constructed value if no such entry exists.
 185   ValueT lookup(const_arg_type_t<KeyT> Val) const {
 186     const BucketT *TheBucket;
 187     if (LookupBucketFor(Val, TheBucket))
 188       return TheBucket->getSecond();
 189     return ValueT();
 190   }
 191
 192   // Inserts key,value pair into the map if the key isn't already in the map.
 193   // If the key is already in the map, it returns false and doesn't update the
 194   // value.
 195   std::pair<iterator, bool> insert(const std::pair<KeyT, ValueT> &KV) {
 196     return try_emplace(KV.first, KV.second);
 197   }
 198
 199   // Inserts key,value pair into the map if the key isn't already in the map.
 200   // If the key is already in the map, it returns false and doesn't update the
 201   // value.
 202   std::pair<iterator, bool> insert(std::pair<KeyT, ValueT> &&KV) {
 203     return try_emplace(std::move(KV.first), std::move(KV.second));
 204   }
 205
 206   // Inserts key,value pair into the map if the key isn't already in the map.
 207   // The value is constructed in-place if the key is not in the map, otherwise
 208   // it is not moved.
 209   template <typename... Ts>
 210   std::pair<iterator, bool> try_emplace(KeyT &&Key, Ts &&... Args) {
 211     BucketT *TheBucket;
 212     if (LookupBucketFor(Key, TheBucket))
 213       return std::make_pair(
 214                makeIterator(TheBucket, getBucketsEnd(), *this, true),
 215                false); // Already in map.
 216
 217     // Otherwise, insert the new element.
 218     TheBucket =
 219         InsertIntoBucket(TheBucket, std::move(Key), std::forward<Ts>(Args)...);
 220     return std::make_pair(
 221              makeIterator(TheBucket, getBucketsEnd(), *this, true),
 222              true);
 223   }
 224
 225   // Inserts key,value pair into the map if the key isn't already in the map.
 226   // The value is constructed in-place if the key is not in the map, otherwise
 227   // it is not moved.
 228   template <typename... Ts>
 229   std::pair<iterator, bool> try_emplace(const KeyT &Key, Ts &&... Args) {
 230     BucketT *TheBucket;
 231     if (LookupBucketFor(Key, TheBucket))
 232       return std::make_pair(
 233                makeIterator(TheBucket, getBucketsEnd(), *this, true),
 234                false); // Already in map.
 235
 236     // Otherwise, insert the new element.
 237     TheBucket = InsertIntoBucket(TheBucket, Key, std::forward<Ts>(Args)...);
 238     return std::make_pair(
 239              makeIterator(TheBucket, getBucketsEnd(), *this, true),
 240              true);
 241   }
 242
 243   /// Alternate version of insert() which allows a different, and possibly
 244   /// less expensive, key type.
 245   /// The DenseMapInfo is responsible for supplying methods
 246   /// getHashValue(LookupKeyT) and isEqual(LookupKeyT, KeyT) for each key
 247   /// type used.
 248   template <typename LookupKeyT>
 249   std::pair<iterator, bool> insert_as(std::pair<KeyT, ValueT> &&KV,
 250                                       const LookupKeyT &Val) {
 251     BucketT *TheBucket;
 252     if (LookupBucketFor(Val, TheBucket))
 253       return std::make_pair(
 254                makeIterator(TheBucket, getBucketsEnd(), *this, true),
 255                false); // Already in map.
 256
 257     // Otherwise, insert the new element.
 258     TheBucket = InsertIntoBucketWithLookup(TheBucket, std::move(KV.first),
 259                                            std::move(KV.second), Val);
 260     return std::make_pair(
 261              makeIterator(TheBucket, getBucketsEnd(), *this, true),
 262              true);
 263   }
 264
 265   /// insert - Range insertion of pairs.
 266   template<typename InputIt>
 267   void insert(InputIt I, InputIt E) {
 268     for (; I != E; ++I)
 269       insert(*I);
 270   }
 271
 272   bool erase(const KeyT &Val) {
 273     BucketT *TheBucket;
 274     if (!LookupBucketFor(Val, TheBucket))
 275       return false; // not in map.
 276
 277     TheBucket->getSecond().~ValueT();
 278     TheBucket->getFirst() = getTombstoneKey();
 279     decrementNumEntries();
 280     incrementNumTombstones();
 281     return true;
 282   }
 283   void erase(iterator I) {
 284     BucketT *TheBucket = &*I;
 285     TheBucket->getSecond().~ValueT();
 286     TheBucket->getFirst() = getTombstoneKey();
 287     decrementNumEntries();
 288     incrementNumTombstones();
 289   }
 290
 291   value_type& FindAndConstruct(const KeyT &Key) {
 292     BucketT *TheBucket;
 293     if (LookupBucketFor(Key, TheBucket))
 294       return *TheBucket;
 295
 296     return *InsertIntoBucket(TheBucket, Key);
 297   }
 298
 299   ValueT &operator[](const KeyT &Key) {
 300     return FindAndConstruct(Key).second;
 301   }
 302
 303   value_type& FindAndConstruct(KeyT &&Key) {
 304     BucketT *TheBucket;
 305     if (LookupBucketFor(Key, TheBucket))
 306       return *TheBucket;
 307
 308     return *InsertIntoBucket(TheBucket, std::move(Key));
 309   }
 310
 311   ValueT &operator[](KeyT &&Key) {
 312     return FindAndConstruct(std::move(Key)).second;
 313   }
 314
 315   /// isPointerIntoBucketsArray - Return true if the specified pointer points
 316   /// somewhere into the DenseMap's array of buckets (i.e. either to a key or
 317   /// value in the DenseMap).
 318   bool isPointerIntoBucketsArray(const void *Ptr) const {
 319     return Ptr >= getBuckets() && Ptr < getBucketsEnd();
 320   }
 321
 322   /// getPointerIntoBucketsArray() - Return an opaque pointer into the buckets
 323   /// array.  In conjunction with the previous method, this can be used to
 324   /// determine whether an insertion caused the DenseMap to reallocate.
 325   const void *getPointerIntoBucketsArray() const { return getBuckets(); }
 326
 327 protected:
 328   DenseMapBase() = default;
 329
 330   void destroyAll() {
 331     if (getNumBuckets() == 0) // Nothing to do.
 332       return;
 333
 334     const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
 335     for (BucketT *P = getBuckets(), *E = getBucketsEnd(); P != E; ++P) {
 336       if (!KeyInfoT::isEqual(P->getFirst(), EmptyKey) &&
 337           !KeyInfoT::isEqual(P->getFirst(), TombstoneKey))
 338         P->getSecond().~ValueT();
 339       P->getFirst().~KeyT();
 340     }
 341   }
 342
 343   void initEmpty() {
 344     setNumEntries(0);
 345     setNumTombstones(0);
 346
 347     assert((getNumBuckets() & (getNumBuckets()-1)) == 0 &&
 348            "# initial buckets must be a power of two!");
 349     const KeyT EmptyKey = getEmptyKey();
 350     for (BucketT *B = getBuckets(), *E = getBucketsEnd(); B != E; ++B)
 351       ::new (&B->getFirst()) KeyT(EmptyKey);
 352   }
 353
 354   /// Returns the number of buckets to allocate to ensure that the DenseMap can
 355   /// accommodate \p NumEntries without need to grow().
 356   unsigned getMinBucketToReserveForEntries(unsigned NumEntries) {
 357     // Ensure that "NumEntries * 4 < NumBuckets * 3"
 358     if (NumEntries == 0)
 359       return 0;
 360     // +1 is required because of the strict equality.
 361     // For example if NumEntries is 48, we need to return 401.
 362     return NextPowerOf2(NumEntries * 4 / 3 + 1);
 363   }
 364
 365   void moveFromOldBuckets(BucketT *OldBucketsBegin, BucketT *OldBucketsEnd) {
 366     initEmpty();
 367
 368     // Insert all the old elements.
 369     const KeyT EmptyKey = getEmptyKey();
 370     const KeyT TombstoneKey = getTombstoneKey();
 371     for (BucketT *B = OldBucketsBegin, *E = OldBucketsEnd; B != E; ++B) {
 372       if (!KeyInfoT::isEqual(B->getFirst(), EmptyKey) &&
 373           !KeyInfoT::isEqual(B->getFirst(), TombstoneKey)) {
 374         // Insert the key/value into the new table.
 375         BucketT *DestBucket;
 376         bool FoundVal = LookupBucketFor(B->getFirst(), DestBucket);
 377         (void)FoundVal; // silence warning.
 378         assert(!FoundVal && "Key already in new map?");
 379         DestBucket->getFirst() = std::move(B->getFirst());
 380         ::new (&DestBucket->getSecond()) ValueT(std::move(B->getSecond()));
 381         incrementNumEntries();
 382
 383         // Free the value.
 384         B->getSecond().~ValueT();
 385       }
 386       B->getFirst().~KeyT();
 387     }
 388   }
 389
 390   template <typename OtherBaseT>
 391   void copyFrom(
 392       const DenseMapBase<OtherBaseT, KeyT, ValueT, KeyInfoT, BucketT> &other) {
 393     assert(&other != this);
 394     assert(getNumBuckets() == other.getNumBuckets());
 395
 396     setNumEntries(other.getNumEntries());
 397     setNumTombstones(other.getNumTombstones());
 398
 399     if (is_trivially_copyable<KeyT>::value &&
 400         is_trivially_copyable<ValueT>::value)
 401       memcpy(reinterpret_cast<void *>(getBuckets()), other.getBuckets(),
 402              getNumBuckets() * sizeof(BucketT));
 403     else
 404       for (size_t i = 0; i < getNumBuckets(); ++i) {
 405         ::new (&getBuckets()[i].getFirst())
 406             KeyT(other.getBuckets()[i].getFirst());
 407         if (!KeyInfoT::isEqual(getBuckets()[i].getFirst(), getEmptyKey()) &&
 408             !KeyInfoT::isEqual(getBuckets()[i].getFirst(), getTombstoneKey()))
 409           ::new (&getBuckets()[i].getSecond())
 410               ValueT(other.getBuckets()[i].getSecond());
 411       }
 412   }
 413
 414   static unsigned getHashValue(const KeyT &Val) {
 415     return KeyInfoT::getHashValue(Val);
 416   }
 417
 418   template<typename LookupKeyT>
 419   static unsigned getHashValue(const LookupKeyT &Val) {
 420     return KeyInfoT::getHashValue(Val);
 421   }
 422
 423   static const KeyT getEmptyKey() {
 424     static_assert(std::is_base_of<DenseMapBase, DerivedT>::value,
 425                   "Must pass the derived type to this template!");
 426     return KeyInfoT::getEmptyKey();
 427   }
 428
 429   static const KeyT getTombstoneKey() {
 430     return KeyInfoT::getTombstoneKey();
 431   }
 432
 433 private:
 434   iterator makeIterator(BucketT *P, BucketT *E,
 435                         DebugEpochBase &Epoch,
 436                         bool NoAdvance=false) {
 437     if (shouldReverseIterate<KeyT>()) {
 438       BucketT *B = P == getBucketsEnd() ? getBuckets() : P + 1;
 439       return iterator(B, E, Epoch, NoAdvance);
 440     }
 441     return iterator(P, E, Epoch, NoAdvance);
 442   }
 443
 444   const_iterator makeConstIterator(const BucketT *P, const BucketT *E,
 445                                    const DebugEpochBase &Epoch,
 446                                    const bool NoAdvance=false) const {
 447     if (shouldReverseIterate<KeyT>()) {
 448       const BucketT *B = P == getBucketsEnd() ? getBuckets() : P + 1;
 449       return const_iterator(B, E, Epoch, NoAdvance);
 450     }
 451     return const_iterator(P, E, Epoch, NoAdvance);
 452   }
 453
 454   unsigned getNumEntries() const {
 455     return static_cast<const DerivedT *>(this)->getNumEntries();
 456   }
 457
 458   void setNumEntries(unsigned Num) {
 459     static_cast<DerivedT *>(this)->setNumEntries(Num);
 460   }
 461
 462   void incrementNumEntries() {
 463     setNumEntries(getNumEntries() + 1);
 464   }
 465
 466   void decrementNumEntries() {
 467     setNumEntries(getNumEntries() - 1);
 468   }
 469
 470   unsigned getNumTombstones() const {
 471     return static_cast<const DerivedT *>(this)->getNumTombstones();
 472   }
 473
 474   void setNumTombstones(unsigned Num) {
 475     static_cast<DerivedT *>(this)->setNumTombstones(Num);
 476   }
 477
 478   void incrementNumTombstones() {
 479     setNumTombstones(getNumTombstones() + 1);
 480   }
 481
 482   void decrementNumTombstones() {
 483     setNumTombstones(getNumTombstones() - 1);
 484   }
 485
 486   const BucketT *getBuckets() const {
 487     return static_cast<const DerivedT *>(this)->getBuckets();
 488   }
 489
 490   BucketT *getBuckets() {
 491     return static_cast<DerivedT *>(this)->getBuckets();
 492   }
 493
 494   unsigned getNumBuckets() const {
 495     return static_cast<const DerivedT *>(this)->getNumBuckets();
 496   }
 497
 498   BucketT *getBucketsEnd() {
 499     return getBuckets() + getNumBuckets();
 500   }
 501
 502   const BucketT *getBucketsEnd() const {
 503     return getBuckets() + getNumBuckets();
 504   }
 505
 506   void grow(unsigned AtLeast) {
 507     static_cast<DerivedT *>(this)->grow(AtLeast);
 508   }
 509
 510   void shrink_and_clear() {
 511     static_cast<DerivedT *>(this)->shrink_and_clear();
 512   }
 513
 514   template <typename KeyArg, typename... ValueArgs>
 515   BucketT *InsertIntoBucket(BucketT *TheBucket, KeyArg &&Key,
 516                             ValueArgs &&... Values) {
 517     TheBucket = InsertIntoBucketImpl(Key, Key, TheBucket);
 518
 519     TheBucket->getFirst() = std::forward<KeyArg>(Key);
 520     ::new (&TheBucket->getSecond()) ValueT(std::forward<ValueArgs>(Values)...);
 521     return TheBucket;
 522   }
 523
 524   template <typename LookupKeyT>
 525   BucketT *InsertIntoBucketWithLookup(BucketT *TheBucket, KeyT &&Key,
 526                                       ValueT &&Value, LookupKeyT &Lookup) {
 527     TheBucket = InsertIntoBucketImpl(Key, Lookup, TheBucket);
 528
 529     TheBucket->getFirst() = std::move(Key);
 530     ::new (&TheBucket->getSecond()) ValueT(std::move(Value));
 531     return TheBucket;
 532   }
 533
 534   template <typename LookupKeyT>
 535   BucketT *InsertIntoBucketImpl(const KeyT &Key, const LookupKeyT &Lookup,
 536                                 BucketT *TheBucket) {
 537     incrementEpoch();
 538
 539     // If the load of the hash table is more than 3/4, or if fewer than 1/8 of
 540     // the buckets are empty (meaning that many are filled with tombstones),
 541     // grow the table.
 542     //
 543     // The later case is tricky.  For example, if we had one empty bucket with
 544     // tons of tombstones, failing lookups (e.g. for insertion) would have to
 545     // probe almost the entire table until it found the empty bucket.  If the
 546     // table completely filled with tombstones, no lookup would ever succeed,
 547     // causing infinite loops in lookup.
 548     unsigned NewNumEntries = getNumEntries() + 1;
 549     unsigned NumBuckets = getNumBuckets();
 550     if (LLVM_UNLIKELY(NewNumEntries * 4 >= NumBuckets * 3)) {
 551       this->grow(NumBuckets * 2);
 552       LookupBucketFor(Lookup, TheBucket);
 553       NumBuckets = getNumBuckets();
 554     } else if (LLVM_UNLIKELY(NumBuckets-(NewNumEntries+getNumTombstones()) <=
 555                              NumBuckets/8)) {
 556       this->grow(NumBuckets);
 557       LookupBucketFor(Lookup, TheBucket);
 558     }
 559     assert(TheBucket);
 560
 561     // Only update the state after we've grown our bucket space appropriately
 562     // so that when growing buckets we have self-consistent entry count.
 563     incrementNumEntries();
 564
 565     // If we are writing over a tombstone, remember this.
 566     const KeyT EmptyKey = getEmptyKey();
 567     if (!KeyInfoT::isEqual(TheBucket->getFirst(), EmptyKey))
 568       decrementNumTombstones();
 569
 570     return TheBucket;
 571   }
 572
 573   /// LookupBucketFor - Lookup the appropriate bucket for Val, returning it in
 574   /// FoundBucket.  If the bucket contains the key and a value, this returns
 575   /// true, otherwise it returns a bucket with an empty marker or tombstone and
 576   /// returns false.
 577   template<typename LookupKeyT>
 578   bool LookupBucketFor(const LookupKeyT &Val,
 579                        const BucketT *&FoundBucket) const {
 580     const BucketT *BucketsPtr = getBuckets();
 581     const unsigned NumBuckets = getNumBuckets();
 582
 583     if (NumBuckets == 0) {
 584       FoundBucket = nullptr;
 585       return false;
 586     }
 587
 588     // FoundTombstone - Keep track of whether we find a tombstone while probing.
 589     const BucketT *FoundTombstone = nullptr;
 590     const KeyT EmptyKey = getEmptyKey();
 591     const KeyT TombstoneKey = getTombstoneKey();
 592     assert(!KeyInfoT::isEqual(Val, EmptyKey) &&
 593            !KeyInfoT::isEqual(Val, TombstoneKey) &&
 594            "Empty/Tombstone value shouldn't be inserted into map!");
 595
 596     unsigned BucketNo = getHashValue(Val) & (NumBuckets-1);
 597     unsigned ProbeAmt = 1;
 598     while (true) {
 599       const BucketT *ThisBucket = BucketsPtr + BucketNo;
 600       // Found Val's bucket?  If so, return it.
 601       if (LLVM_LIKELY(KeyInfoT::isEqual(Val, ThisBucket->getFirst()))) {
 602         FoundBucket = ThisBucket;
 603         return true;
 604       }
 605
 606       // If we found an empty bucket, the key doesn't exist in the set.
 607       // Insert it and return the default value.
 608       if (LLVM_LIKELY(KeyInfoT::isEqual(ThisBucket->getFirst(), EmptyKey))) {
 609         // If we've already seen a tombstone while probing, fill it in instead
 610         // of the empty bucket we eventually probed to.
 611         FoundBucket = FoundTombstone ? FoundTombstone : ThisBucket;
 612         return false;
 613       }
 614
 615       // If this is a tombstone, remember it.  If Val ends up not in the map, we
 616       // prefer to return it than something that would require more probing.
 617       if (KeyInfoT::isEqual(ThisBucket->getFirst(), TombstoneKey) &&
 618           !FoundTombstone)
 619         FoundTombstone = ThisBucket;  // Remember the first tombstone found.
 620
 621       // Otherwise, it's a hash collision or a tombstone, continue quadratic
 622       // probing.
 623       BucketNo += ProbeAmt++;
 624       BucketNo &= (NumBuckets-1);
 625     }
 626   }
 627
 628   template <typename LookupKeyT>
 629   bool LookupBucketFor(const LookupKeyT &Val, BucketT *&FoundBucket) {
 630     const BucketT *ConstFoundBucket;
 631     bool Result = const_cast<const DenseMapBase *>(this)
 632       ->LookupBucketFor(Val, ConstFoundBucket);
 633     FoundBucket = const_cast<BucketT *>(ConstFoundBucket);
 634     return Result;
 635   }
 636
 637 public:
 638   /// Return the approximate size (in bytes) of the actual map.
 639   /// This is just the raw memory used by DenseMap.
 640   /// If entries are pointers to objects, the size of the referenced objects
 641   /// are not included.
 642   size_t getMemorySize() const {
 643     return getNumBuckets() * sizeof(BucketT);
 644   }
 645 };
 646
 647 /// Equality comparison for DenseMap.
 648 ///
 649 /// Iterates over elements of LHS confirming that each (key, value) pair in LHS
 650 /// is also in RHS, and that no additional pairs are in RHS.
 651 /// Equivalent to N calls to RHS.find and N value comparisons. Amortized
 652 /// complexity is linear, worst case is O(N^2) (if every hash collides).
 653 template <typename DerivedT, typename KeyT, typename ValueT, typename KeyInfoT,
 654           typename BucketT>
 655 bool operator==(
 656     const DenseMapBase<DerivedT, KeyT, ValueT, KeyInfoT, BucketT> &LHS,
 657     const DenseMapBase<DerivedT, KeyT, ValueT, KeyInfoT, BucketT> &RHS) {
 658   if (LHS.size() != RHS.size())
 659     return false;
 660
 661   for (auto &KV : LHS) {
 662     auto I = RHS.find(KV.first);
 663     if (I == RHS.end() || I->second != KV.second)
 664       return false;
 665   }
 666
 667   return true;
 668 }
 669
 670 /// Inequality comparison for DenseMap.
 671 ///
 672 /// Equivalent to !(LHS == RHS). See operator== for performance notes.
 673 template <typename DerivedT, typename KeyT, typename ValueT, typename KeyInfoT,
 674           typename BucketT>
 675 bool operator!=(
 676     const DenseMapBase<DerivedT, KeyT, ValueT, KeyInfoT, BucketT> &LHS,
 677     const DenseMapBase<DerivedT, KeyT, ValueT, KeyInfoT, BucketT> &RHS) {
 678   return !(LHS == RHS);
 679 }
 680
 681 template <typename KeyT, typename ValueT,
 682           typename KeyInfoT = DenseMapInfo<KeyT>,
 683           typename BucketT = llvm::detail::DenseMapPair<KeyT, ValueT>>
 684 class DenseMap : public DenseMapBase<DenseMap<KeyT, ValueT, KeyInfoT, BucketT>,
 685                                      KeyT, ValueT, KeyInfoT, BucketT> {
 686   friend class DenseMapBase<DenseMap, KeyT, ValueT, KeyInfoT, BucketT>;
 687
 688   // Lift some types from the dependent base class into this class for
 689   // simplicity of referring to them.
 690   using BaseT = DenseMapBase<DenseMap, KeyT, ValueT, KeyInfoT, BucketT>;
 691
 692   BucketT *Buckets;
 693   unsigned NumEntries;
 694   unsigned NumTombstones;
 695   unsigned NumBuckets;
 696
 697 public:
 698   /// Create a DenseMap wth an optional \p InitialReserve that guarantee that
 699   /// this number of elements can be inserted in the map without grow()
 700   explicit DenseMap(unsigned InitialReserve = 0) { init(InitialReserve); }
 701
 702   DenseMap(const DenseMap &other) : BaseT() {
 703     init(0);
 704     copyFrom(other);
 705   }
 706
 707   DenseMap(DenseMap &&other) : BaseT() {
 708     init(0);
 709     swap(other);
 710   }
 711
 712   template<typename InputIt>
 713   DenseMap(const InputIt &I, const InputIt &E) {
 714     init(std::distance(I, E));
 715     this->insert(I, E);
 716   }
 717
 718   DenseMap(std::initializer_list<typename BaseT::value_type> Vals) {
 719     init(Vals.size());
 720     this->insert(Vals.begin(), Vals.end());
 721   }
 722
 723   ~DenseMap() {
 724     this->destroyAll();
 725     deallocate_buffer(Buckets, sizeof(BucketT) * NumBuckets, alignof(BucketT));
 726   }
 727
 728   void swap(DenseMap& RHS) {
 729     this->incrementEpoch();
 730     RHS.incrementEpoch();
 731     std::swap(Buckets, RHS.Buckets);
 732     std::swap(NumEntries, RHS.NumEntries);
 733     std::swap(NumTombstones, RHS.NumTombstones);
 734     std::swap(NumBuckets, RHS.NumBuckets);
 735   }
 736
 737   DenseMap& operator=(const DenseMap& other) {
 738     if (&other != this)
 739       copyFrom(other);
 740     return *this;
 741   }
 742
 743   DenseMap& operator=(DenseMap &&other) {
 744     this->destroyAll();
 745     deallocate_buffer(Buckets, sizeof(BucketT) * NumBuckets, alignof(BucketT));
 746     init(0);
 747     swap(other);
 748     return *this;
 749   }
 750
 751   void copyFrom(const DenseMap& other) {
 752     this->destroyAll();
 753     deallocate_buffer(Buckets, sizeof(BucketT) * NumBuckets, alignof(BucketT));
 754     if (allocateBuckets(other.NumBuckets)) {
 755       this->BaseT::copyFrom(other);
 756     } else {
 757       NumEntries = 0;
 758       NumTombstones = 0;
 759     }
 760   }
 761
 762   void init(unsigned InitNumEntries) {
 763     auto InitBuckets = BaseT::getMinBucketToReserveForEntries(InitNumEntries);
 764     if (allocateBuckets(InitBuckets)) {
 765       this->BaseT::initEmpty();
 766     } else {
 767       NumEntries = 0;
 768       NumTombstones = 0;
 769     }
 770   }
 771
 772   void grow(unsigned AtLeast) {
 773     unsigned OldNumBuckets = NumBuckets;
 774     BucketT *OldBuckets = Buckets;
 775
 776     allocateBuckets(std::max<unsigned>(64, static_cast<unsigned>(NextPowerOf2(AtLeast-1))));
 777     assert(Buckets);
 778     if (!OldBuckets) {
 779       this->BaseT::initEmpty();
 780       return;
 781     }
 782
 783     this->moveFromOldBuckets(OldBuckets, OldBuckets+OldNumBuckets);
 784
 785     // Free the old table.
 786     deallocate_buffer(OldBuckets, sizeof(BucketT) * OldNumBuckets,
 787                       alignof(BucketT));
 788   }
 789
 790   void shrink_and_clear() {
 791     unsigned OldNumBuckets = NumBuckets;
 792     unsigned OldNumEntries = NumEntries;
 793     this->destroyAll();
 794
 795     // Reduce the number of buckets.
 796     unsigned NewNumBuckets = 0;
 797     if (OldNumEntries)
 798       NewNumBuckets = std::max(64, 1 << (Log2_32_Ceil(OldNumEntries) + 1));
 799     if (NewNumBuckets == NumBuckets) {
 800       this->BaseT::initEmpty();
 801       return;
 802     }
 803
 804     deallocate_buffer(Buckets, sizeof(BucketT) * OldNumBuckets,
 805                       alignof(BucketT));
 806     init(NewNumBuckets);
 807   }
 808
 809 private:
 810   unsigned getNumEntries() const {
 811     return NumEntries;
 812   }
 813
 814   void setNumEntries(unsigned Num) {
 815     NumEntries = Num;
 816   }
 817
 818   unsigned getNumTombstones() const {
 819     return NumTombstones;
 820   }
 821
 822   void setNumTombstones(unsigned Num) {
 823     NumTombstones = Num;
 824   }
 825
 826   BucketT *getBuckets() const {
 827     return Buckets;
 828   }
 829
 830   unsigned getNumBuckets() const {
 831     return NumBuckets;
 832   }
 833
 834   bool allocateBuckets(unsigned Num) {
 835     NumBuckets = Num;
 836     if (NumBuckets == 0) {
 837       Buckets = nullptr;
 838       return false;
 839     }
 840
 841     Buckets = static_cast<BucketT *>(
 842         allocate_buffer(sizeof(BucketT) * NumBuckets, alignof(BucketT)));
 843     return true;
 844   }
 845 };
 846
 847 template <typename KeyT, typename ValueT, unsigned InlineBuckets = 4,
 848           typename KeyInfoT = DenseMapInfo<KeyT>,
 849           typename BucketT = llvm::detail::DenseMapPair<KeyT, ValueT>>
 850 class SmallDenseMap
 851     : public DenseMapBase<
 852           SmallDenseMap<KeyT, ValueT, InlineBuckets, KeyInfoT, BucketT>, KeyT,
 853           ValueT, KeyInfoT, BucketT> {
 854   friend class DenseMapBase<SmallDenseMap, KeyT, ValueT, KeyInfoT, BucketT>;
 855
 856   // Lift some types from the dependent base class into this class for
 857   // simplicity of referring to them.
 858   using BaseT = DenseMapBase<SmallDenseMap, KeyT, ValueT, KeyInfoT, BucketT>;
 859
 860   static_assert(isPowerOf2_64(InlineBuckets),
 861                 "InlineBuckets must be a power of 2.");
 862
 863   unsigned Small : 1;
 864   unsigned NumEntries : 31;
 865   unsigned NumTombstones;
 866
 867   struct LargeRep {
 868     BucketT *Buckets;
 869     unsigned NumBuckets;
 870   };
 871
 872   /// A "union" of an inline bucket array and the struct representing
 873   /// a large bucket. This union will be discriminated by the 'Small' bit.
 874   AlignedCharArrayUnion<BucketT[InlineBuckets], LargeRep> storage;
 875
 876 public:
 877   explicit SmallDenseMap(unsigned NumInitBuckets = 0) {
 878     init(NumInitBuckets);
 879   }
 880
 881   SmallDenseMap(const SmallDenseMap &other) : BaseT() {
 882     init(0);
 883     copyFrom(other);
 884   }
 885
 886   SmallDenseMap(SmallDenseMap &&other) : BaseT() {
 887     init(0);
 888     swap(other);
 889   }
 890
 891   template<typename InputIt>
 892   SmallDenseMap(const InputIt &I, const InputIt &E) {
 893     init(NextPowerOf2(std::distance(I, E)));
 894     this->insert(I, E);
 895   }
 896
 897   ~SmallDenseMap() {
 898     this->destroyAll();
 899     deallocateBuckets();
 900   }
 901
 902   void swap(SmallDenseMap& RHS) {
 903     unsigned TmpNumEntries = RHS.NumEntries;
 904     RHS.NumEntries = NumEntries;
 905     NumEntries = TmpNumEntries;
 906     std::swap(NumTombstones, RHS.NumTombstones);
 907
 908     const KeyT EmptyKey = this->getEmptyKey();
 909     const KeyT TombstoneKey = this->getTombstoneKey();
 910     if (Small && RHS.Small) {
 911       // If we're swapping inline bucket arrays, we have to cope with some of
 912       // the tricky bits of DenseMap's storage system: the buckets are not
 913       // fully initialized. Thus we swap every key, but we may have
 914       // a one-directional move of the value.
 915       for (unsigned i = 0, e = InlineBuckets; i != e; ++i) {
 916         BucketT *LHSB = &getInlineBuckets()[i],
 917                 *RHSB = &RHS.getInlineBuckets()[i];
 918         bool hasLHSValue = (!KeyInfoT::isEqual(LHSB->getFirst(), EmptyKey) &&
 919                             !KeyInfoT::isEqual(LHSB->getFirst(), TombstoneKey));
 920         bool hasRHSValue = (!KeyInfoT::isEqual(RHSB->getFirst(), EmptyKey) &&
 921                             !KeyInfoT::isEqual(RHSB->getFirst(), TombstoneKey));
 922         if (hasLHSValue && hasRHSValue) {
 923           // Swap together if we can...
 924           std::swap(*LHSB, *RHSB);
 925           continue;
 926         }
 927         // Swap separately and handle any assymetry.
 928         std::swap(LHSB->getFirst(), RHSB->getFirst());
 929         if (hasLHSValue) {
 930           ::new (&RHSB->getSecond()) ValueT(std::move(LHSB->getSecond()));
 931           LHSB->getSecond().~ValueT();
 932         } else if (hasRHSValue) {
 933           ::new (&LHSB->getSecond()) ValueT(std::move(RHSB->getSecond()));
 934           RHSB->getSecond().~ValueT();
 935         }
 936       }
 937       return;
 938     }
 939     if (!Small && !RHS.Small) {
 940       std::swap(getLargeRep()->Buckets, RHS.getLargeRep()->Buckets);
 941       std::swap(getLargeRep()->NumBuckets, RHS.getLargeRep()->NumBuckets);
 942       return;
 943     }
 944
 945     SmallDenseMap &SmallSide = Small ? *this : RHS;
 946     SmallDenseMap &LargeSide = Small ? RHS : *this;
 947
 948     // First stash the large side's rep and move the small side across.
 949     LargeRep TmpRep = std::move(*LargeSide.getLargeRep());
 950     LargeSide.getLargeRep()->~LargeRep();
 951     LargeSide.Small = true;
 952     // This is similar to the standard move-from-old-buckets, but the bucket
 953     // count hasn't actually rotated in this case. So we have to carefully
 954     // move construct the keys and values into their new locations, but there
 955     // is no need to re-hash things.
 956     for (unsigned i = 0, e = InlineBuckets; i != e; ++i) {
 957       BucketT *NewB = &LargeSide.getInlineBuckets()[i],
 958               *OldB = &SmallSide.getInlineBuckets()[i];
 959       ::new (&NewB->getFirst()) KeyT(std::move(OldB->getFirst()));
 960       OldB->getFirst().~KeyT();
 961       if (!KeyInfoT::isEqual(NewB->getFirst(), EmptyKey) &&
 962           !KeyInfoT::isEqual(NewB->getFirst(), TombstoneKey)) {
 963         ::new (&NewB->getSecond()) ValueT(std::move(OldB->getSecond()));
 964         OldB->getSecond().~ValueT();
 965       }
 966     }
 967
 968     // The hard part of moving the small buckets across is done, just move
 969     // the TmpRep into its new home.
 970     SmallSide.Small = false;
 971     new (SmallSide.getLargeRep()) LargeRep(std::move(TmpRep));
 972   }
 973
 974   SmallDenseMap& operator=(const SmallDenseMap& other) {
 975     if (&other != this)
 976       copyFrom(other);
 977     return *this;
 978   }
 979
 980   SmallDenseMap& operator=(SmallDenseMap &&other) {
 981     this->destroyAll();
 982     deallocateBuckets();
 983     init(0);
 984     swap(other);
 985     return *this;
 986   }
 987
 988   void copyFrom(const SmallDenseMap& other) {
 989     this->destroyAll();
 990     deallocateBuckets();
 991     Small = true;
 992     if (other.getNumBuckets() > InlineBuckets) {
 993       Small = false;
 994       new (getLargeRep()) LargeRep(allocateBuckets(other.getNumBuckets()));
 995     }
 996     this->BaseT::copyFrom(other);
 997   }
 998
 999   void init(unsigned InitBuckets) {
1000     Small = true;
1001     if (InitBuckets > InlineBuckets) {
1002       Small = false;
1003       new (getLargeRep()) LargeRep(allocateBuckets(InitBuckets));
1004     }
1005     this->BaseT::initEmpty();
1006   }
1007
1008   void grow(unsigned AtLeast) {
1009     if (AtLeast >= InlineBuckets)
1010       AtLeast = std::max<unsigned>(64, NextPowerOf2(AtLeast-1));
1011
1012     if (Small) {
1013       if (AtLeast < InlineBuckets)
1014         return; // Nothing to do.
1015
1016       // First move the inline buckets into a temporary storage.
1017       AlignedCharArrayUnion<BucketT[InlineBuckets]> TmpStorage;
1018       BucketT *TmpBegin = reinterpret_cast<BucketT *>(TmpStorage.buffer);
1019       BucketT *TmpEnd = TmpBegin;
1020
1021       // Loop over the buckets, moving non-empty, non-tombstones into the
1022       // temporary storage. Have the loop move the TmpEnd forward as it goes.
1023       const KeyT EmptyKey = this->getEmptyKey();
1024       const KeyT TombstoneKey = this->getTombstoneKey();
1025       for (BucketT *P = getBuckets(), *E = P + InlineBuckets; P != E; ++P) {
1026         if (!KeyInfoT::isEqual(P->getFirst(), EmptyKey) &&
1027             !KeyInfoT::isEqual(P->getFirst(), TombstoneKey)) {
1028           assert(size_t(TmpEnd - TmpBegin) < InlineBuckets &&
1029                  "Too many inline buckets!");
1030           ::new (&TmpEnd->getFirst()) KeyT(std::move(P->getFirst()));
1031           ::new (&TmpEnd->getSecond()) ValueT(std::move(P->getSecond()));
1032           ++TmpEnd;
1033           P->getSecond().~ValueT();
1034         }
1035         P->getFirst().~KeyT();
1036       }
1037
1038       // Now make this map use the large rep, and move all the entries back
1039       // into it.
1040       Small = false;
1041       new (getLargeRep()) LargeRep(allocateBuckets(AtLeast));
1042       this->moveFromOldBuckets(TmpBegin, TmpEnd);
1043       return;
1044     }
1045
1046     LargeRep OldRep = std::move(*getLargeRep());
1047     getLargeRep()->~LargeRep();
1048     if (AtLeast <= InlineBuckets) {
1049       Small = true;
1050     } else {
1051       new (getLargeRep()) LargeRep(allocateBuckets(AtLeast));
1052     }
1053
1054     this->moveFromOldBuckets(OldRep.Buckets, OldRep.Buckets+OldRep.NumBuckets);
1055
1056     // Free the old table.
1057     deallocate_buffer(OldRep.Buckets, sizeof(BucketT) * OldRep.NumBuckets,
1058                       alignof(BucketT));
1059   }
1060
1061   void shrink_and_clear() {
1062     unsigned OldSize = this->size();
1063     this->destroyAll();
1064
1065     // Reduce the number of buckets.
1066     unsigned NewNumBuckets = 0;
1067     if (OldSize) {
1068       NewNumBuckets = 1 << (Log2_32_Ceil(OldSize) + 1);
1069       if (NewNumBuckets > InlineBuckets && NewNumBuckets < 64u)
1070         NewNumBuckets = 64;
1071     }
1072     if ((Small && NewNumBuckets <= InlineBuckets) ||
1073         (!Small && NewNumBuckets == getLargeRep()->NumBuckets)) {
1074       this->BaseT::initEmpty();
1075       return;
1076     }
1077
1078     deallocateBuckets();
1079     init(NewNumBuckets);
1080   }
1081
1082 private:
1083   unsigned getNumEntries() const {
1084     return NumEntries;
1085   }
1086
1087   void setNumEntries(unsigned Num) {
1088     // NumEntries is hardcoded to be 31 bits wide.
1089     assert(Num < (1U << 31) && "Cannot support more than 1<<31 entries");
1090     NumEntries = Num;
1091   }
1092
1093   unsigned getNumTombstones() const {
1094     return NumTombstones;
1095   }
1096
1097   void setNumTombstones(unsigned Num) {
1098     NumTombstones = Num;
1099   }
1100
1101   const BucketT *getInlineBuckets() const {
1102     assert(Small);
1103     // Note that this cast does not violate aliasing rules as we assert that
1104     // the memory's dynamic type is the small, inline bucket buffer, and the
1105     // 'storage.buffer' static type is 'char *'.
1106     return reinterpret_cast<const BucketT *>(storage.buffer);
1107   }
1108
1109   BucketT *getInlineBuckets() {
1110     return const_cast<BucketT *>(
1111       const_cast<const SmallDenseMap *>(this)->getInlineBuckets());
1112   }
1113
1114   const LargeRep *getLargeRep() const {
1115     assert(!Small);
1116     // Note, same rule about aliasing as with getInlineBuckets.
1117     return reinterpret_cast<const LargeRep *>(storage.buffer);
1118   }
1119
1120   LargeRep *getLargeRep() {
1121     return const_cast<LargeRep *>(
1122       const_cast<const SmallDenseMap *>(this)->getLargeRep());
1123   }
1124
1125   const BucketT *getBuckets() const {
1126     return Small ? getInlineBuckets() : getLargeRep()->Buckets;
1127   }
1128
1129   BucketT *getBuckets() {
1130     return const_cast<BucketT *>(
1131       const_cast<const SmallDenseMap *>(this)->getBuckets());
1132   }
1133
1134   unsigned getNumBuckets() const {
1135     return Small ? InlineBuckets : getLargeRep()->NumBuckets;
1136   }
1137
1138   void deallocateBuckets() {
1139     if (Small)
1140       return;
1141
1142     deallocate_buffer(getLargeRep()->Buckets,
1143                       sizeof(BucketT) * getLargeRep()->NumBuckets,
1144                       alignof(BucketT));
1145     getLargeRep()->~LargeRep();
1146   }
1147
1148   LargeRep allocateBuckets(unsigned Num) {
1149     assert(Num > InlineBuckets && "Must allocate more buckets than are inline");
1150     LargeRep Rep = {static_cast<BucketT *>(allocate_buffer(
1151                         sizeof(BucketT) * Num, alignof(BucketT))),
1152                     Num};
1153     return Rep;
1154   }
1155 };
1156
1157 template <typename KeyT, typename ValueT, typename KeyInfoT, typename Bucket,
1158           bool IsConst>
1159 class DenseMapIterator : DebugEpochBase::HandleBase {
1160   friend class DenseMapIterator<KeyT, ValueT, KeyInfoT, Bucket, true>;
1161   friend class DenseMapIterator<KeyT, ValueT, KeyInfoT, Bucket, false>;
1162
1163   using ConstIterator = DenseMapIterator<KeyT, ValueT, KeyInfoT, Bucket, true>;
1164
1165 public:
1166   using difference_type = ptrdiff_t;
1167   using value_type =
1168       typename std::conditional<IsConst, const Bucket, Bucket>::type;
1169   using pointer = value_type *;
1170   using reference = value_type &;
1171   using iterator_category = std::forward_iterator_tag;
1172
1173 private:
1174   pointer Ptr = nullptr;
1175   pointer End = nullptr;
1176
1177 public:
1178   DenseMapIterator() = default;
1179
1180   DenseMapIterator(pointer Pos, pointer E, const DebugEpochBase &Epoch,
1181                    bool NoAdvance = false)
1182       : DebugEpochBase::HandleBase(&Epoch), Ptr(Pos), End(E) {
1183     assert(isHandleInSync() && "invalid construction!");
1184
1185     if (NoAdvance) return;
1186     if (shouldReverseIterate<KeyT>()) {
1187       RetreatPastEmptyBuckets();
1188       return;
1189     }
1190     AdvancePastEmptyBuckets();
1191   }
1192
1193   // Converting ctor from non-const iterators to const iterators. SFINAE'd out
1194   // for const iterator destinations so it doesn't end up as a user defined copy
1195   // constructor.
1196   template <bool IsConstSrc,
1197             typename = typename std::enable_if<!IsConstSrc && IsConst>::type>
1198   DenseMapIterator(
1199       const DenseMapIterator<KeyT, ValueT, KeyInfoT, Bucket, IsConstSrc> &I)
1200       : DebugEpochBase::HandleBase(I), Ptr(I.Ptr), End(I.End) {}
1201
1202   reference operator*() const {
1203     assert(isHandleInSync() && "invalid iterator access!");
1204     if (shouldReverseIterate<KeyT>())
1205       return Ptr[-1];
1206     return *Ptr;
1207   }
1208   pointer operator->() const {
1209     assert(isHandleInSync() && "invalid iterator access!");
1210     if (shouldReverseIterate<KeyT>())
1211       return &(Ptr[-1]);
1212     return Ptr;
1213   }
1214
1215   bool operator==(const ConstIterator &RHS) const {
1216     assert((!Ptr || isHandleInSync()) && "handle not in sync!");
1217     assert((!RHS.Ptr || RHS.isHandleInSync()) && "handle not in sync!");
1218     assert(getEpochAddress() == RHS.getEpochAddress() &&
1219            "comparing incomparable iterators!");
1220     return Ptr == RHS.Ptr;
1221   }
1222   bool operator!=(const ConstIterator &RHS) const {
1223     assert((!Ptr || isHandleInSync()) && "handle not in sync!");
1224     assert((!RHS.Ptr || RHS.isHandleInSync()) && "handle not in sync!");
1225     assert(getEpochAddress() == RHS.getEpochAddress() &&
1226            "comparing incomparable iterators!");
1227     return Ptr != RHS.Ptr;
1228   }
1229
1230   inline DenseMapIterator& operator++() {  // Preincrement
1231     assert(isHandleInSync() && "invalid iterator access!");
1232     if (shouldReverseIterate<KeyT>()) {
1233       --Ptr;
1234       RetreatPastEmptyBuckets();
1235       return *this;
1236     }
1237     ++Ptr;
1238     AdvancePastEmptyBuckets();
1239     return *this;
1240   }
1241   DenseMapIterator operator++(int) {  // Postincrement
1242     assert(isHandleInSync() && "invalid iterator access!");
1243     DenseMapIterator tmp = *this; ++*this; return tmp;
1244   }
1245
1246 private:
1247   void AdvancePastEmptyBuckets() {
1248     assert(Ptr <= End);
1249     const KeyT Empty = KeyInfoT::getEmptyKey();
1250     const KeyT Tombstone = KeyInfoT::getTombstoneKey();
1251
1252     while (Ptr != End && (KeyInfoT::isEqual(Ptr->getFirst(), Empty) ||
1253                           KeyInfoT::isEqual(Ptr->getFirst(), Tombstone)))
1254       ++Ptr;
1255   }
1256
1257   void RetreatPastEmptyBuckets() {
1258     assert(Ptr >= End);
1259     const KeyT Empty = KeyInfoT::getEmptyKey();
1260     const KeyT Tombstone = KeyInfoT::getTombstoneKey();
1261
1262     while (Ptr != End && (KeyInfoT::isEqual(Ptr[-1].getFirst(), Empty) ||
1263                           KeyInfoT::isEqual(Ptr[-1].getFirst(), Tombstone)))
1264       --Ptr;
1265   }
1266 };
1267
1268 template <typename KeyT, typename ValueT, typename KeyInfoT>
1269 inline size_t capacity_in_bytes(const DenseMap<KeyT, ValueT, KeyInfoT> &X) {
1270   return X.getMemorySize();
1271 }
1272
1273 } // end namespace llvm
1274
1275 #endif // LLVM_ADT_DENSEMAP_H