DenseMap.h revision d10aacea5e2c8ea62e08956aa0a94fa2da60e148 
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/DataTypes.h"
18#include "llvm/Support/MathExtras.h"
19#include <cassert>
20#include <utility>
21
22namespace llvm {
23
24template<typename T>
25struct DenseMapInfo {
26  //static inline T getEmptyKey();
27  //static inline T getTombstoneKey();
28  //static unsigned getHashValue(const T &Val);
29  //static bool isEqual(const T &LHS, const T &RHS);
30  //static bool isPod()
31};
32
33// Provide DenseMapInfo for all pointers.
34template<typename T>
35struct DenseMapInfo<T*> {
36  static inline T* getEmptyKey() { return reinterpret_cast<T*>(-1); }
37  static inline T* getTombstoneKey() { return reinterpret_cast<T*>(-2); }
38  static unsigned getHashValue(const T *PtrVal) {
39    return (unsigned((uintptr_t)PtrVal) >> 4) ^
40           (unsigned((uintptr_t)PtrVal) >> 9);
41  }
42  static bool isEqual(const T *LHS, const T *RHS) { return LHS == RHS; }
43  static bool isPod() { return true; }
44};
45
46// Provide DenseMapInfo for unsigned ints.
47template<> struct DenseMapInfo<unsigned> {
48  static inline unsigned getEmptyKey() { return ~0; }
49  static inline unsigned getTombstoneKey() { return ~0 - 1; }
50  static unsigned getHashValue(const unsigned& Val) { return Val * 37; }
51  static bool isPod() { return true; }
52  static bool isEqual(const unsigned& LHS, const unsigned& RHS) {
53  return LHS == RHS;
54  }
55};
56
57// Provide DenseMapInfo for unsigned longs.
58template<> struct DenseMapInfo<unsigned long> {
59  static inline unsigned long getEmptyKey() { return ~0L; }
60  static inline unsigned long getTombstoneKey() { return ~0L - 1L; }
61  static unsigned getHashValue(const unsigned long& Val) {
62    return (unsigned)(Val * 37L);
63  }
64  static bool isPod() { return true; }
65  static bool isEqual(const unsigned long& LHS, const unsigned long& RHS) {
66  return LHS == RHS;
67  }
68};
69
70// Provide DenseMapInfo for all pairs whose members have info.
71template<typename T, typename U>
72struct DenseMapInfo<std::pair<T, U> > {
73  typedef std::pair<T, U> Pair;
74  typedef DenseMapInfo<T> FirstInfo;
75  typedef DenseMapInfo<U> SecondInfo;
76
77  static inline Pair getEmptyKey() {
78    return std::make_pair(FirstInfo::getEmptyKey(),
79                          SecondInfo::getEmptyKey());
80  }
81  static inline Pair getTombstoneKey() {
82    return std::make_pair(FirstInfo::getTombstoneKey(),
83                            SecondInfo::getEmptyKey());
84  }
85  static unsigned getHashValue(const Pair& PairVal) {
86    uint64_t key = (uint64_t)FirstInfo::getHashValue(PairVal.first) << 32
87          | (uint64_t)SecondInfo::getHashValue(PairVal.second);
88    key += ~(key << 32);
89    key ^= (key >> 22);
90    key += ~(key << 13);
91    key ^= (key >> 8);
92    key += (key << 3);
93    key ^= (key >> 15);
94    key += ~(key << 27);
95    key ^= (key >> 31);
96    return (unsigned)key;
97  }
98  static bool isEqual(const Pair& LHS, const Pair& RHS) { return LHS == RHS; }
99  static bool isPod() { return FirstInfo::isPod() && SecondInfo::isPod(); }
100};
101
102template<typename KeyT, typename ValueT,
103         typename KeyInfoT = DenseMapInfo<KeyT>,
104         typename ValueInfoT = DenseMapInfo<ValueT> >
105class DenseMapIterator;
106template<typename KeyT, typename ValueT,
107         typename KeyInfoT = DenseMapInfo<KeyT>,
108         typename ValueInfoT = DenseMapInfo<ValueT> >
109class DenseMapConstIterator;
110
111template<typename KeyT, typename ValueT,
112         typename KeyInfoT = DenseMapInfo<KeyT>,
113         typename ValueInfoT = DenseMapInfo<ValueT> >
114class DenseMap {
115  typedef std::pair<KeyT, ValueT> BucketT;
116  unsigned NumBuckets;
117  BucketT *Buckets;
118
119  unsigned NumEntries;
120  unsigned NumTombstones;
121public:
122  typedef KeyT key_type;
123  typedef ValueT mapped_type;
124  typedef BucketT value_type;
125
126  DenseMap(const DenseMap& other) {
127    NumBuckets = 0;
128    CopyFrom(other);
129  }
130
131  explicit DenseMap(unsigned NumInitBuckets = 64) {
132    init(NumInitBuckets);
133  }
134
135  ~DenseMap() {
136    const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
137    for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
138      if (!KeyInfoT::isEqual(P->first, EmptyKey) &&
139          !KeyInfoT::isEqual(P->first, TombstoneKey))
140        P->second.~ValueT();
141      P->first.~KeyT();
142    }
143    operator delete(Buckets);
144  }
145
146  typedef DenseMapIterator<KeyT, ValueT, KeyInfoT> iterator;
147  typedef DenseMapConstIterator<KeyT, ValueT, KeyInfoT> const_iterator;
148  inline iterator begin() {
149     return iterator(Buckets, Buckets+NumBuckets);
150  }
151  inline iterator end() {
152    return iterator(Buckets+NumBuckets, Buckets+NumBuckets);
153  }
154  inline const_iterator begin() const {
155    return const_iterator(Buckets, Buckets+NumBuckets);
156  }
157  inline const_iterator end() const {
158    return const_iterator(Buckets+NumBuckets, Buckets+NumBuckets);
159  }
160
161  bool empty() const { return NumEntries == 0; }
162  unsigned size() const { return NumEntries; }
163
164  /// Grow the densemap so that it has at least Size buckets. Does not shrink
165  void resize(size_t Size) { grow(Size); }
166
167  void clear() {
168    // If the capacity of the array is huge, and the # elements used is small,
169    // shrink the array.
170    if (NumEntries * 4 < NumBuckets && NumBuckets > 64) {
171      shrink_and_clear();
172      return;
173    }
174
175    const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
176    for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
177      if (!KeyInfoT::isEqual(P->first, EmptyKey)) {
178        if (!KeyInfoT::isEqual(P->first, TombstoneKey)) {
179          P->second.~ValueT();
180          --NumEntries;
181        }
182        P->first = EmptyKey;
183      }
184    }
185    assert(NumEntries == 0 && "Node count imbalance!");
186    NumTombstones = 0;
187  }
188
189  /// count - Return true if the specified key is in the map.
190  bool count(const KeyT &Val) const {
191    BucketT *TheBucket;
192    return LookupBucketFor(Val, TheBucket);
193  }
194
195  iterator find(const KeyT &Val) {
196    BucketT *TheBucket;
197    if (LookupBucketFor(Val, TheBucket))
198      return iterator(TheBucket, Buckets+NumBuckets);
199    return end();
200  }
201  const_iterator find(const KeyT &Val) const {
202    BucketT *TheBucket;
203    if (LookupBucketFor(Val, TheBucket))
204      return const_iterator(TheBucket, Buckets+NumBuckets);
205    return end();
206  }
207
208  /// lookup - Return the entry for the specified key, or a default
209  /// constructed value if no such entry exists.
210  ValueT lookup(const KeyT &Val) const {
211    BucketT *TheBucket;
212    if (LookupBucketFor(Val, TheBucket))
213      return TheBucket->second;
214    return ValueT();
215  }
216
217  std::pair<iterator, bool> insert(const std::pair<KeyT, ValueT> &KV) {
218    BucketT *TheBucket;
219    if (LookupBucketFor(KV.first, TheBucket))
220      return std::make_pair(iterator(TheBucket, Buckets+NumBuckets),
221                            false); // Already in map.
222
223    // Otherwise, insert the new element.
224    TheBucket = InsertIntoBucket(KV.first, KV.second, TheBucket);
225    return std::make_pair(iterator(TheBucket, Buckets+NumBuckets),
226                          true);
227  }
228
229  /// insert - Range insertion of pairs.
230  template<typename InputIt>
231  void insert(InputIt I, InputIt E) {
232    for (; I != E; ++I)
233      insert(*I);
234  }
235
236
237  bool erase(const KeyT &Val) {
238    BucketT *TheBucket;
239    if (!LookupBucketFor(Val, TheBucket))
240      return false; // not in map.
241
242    TheBucket->second.~ValueT();
243    TheBucket->first = getTombstoneKey();
244    --NumEntries;
245    ++NumTombstones;
246    return true;
247  }
248  bool erase(iterator I) {
249    BucketT *TheBucket = &*I;
250    TheBucket->second.~ValueT();
251    TheBucket->first = getTombstoneKey();
252    --NumEntries;
253    ++NumTombstones;
254    return true;
255  }
256
257  value_type& FindAndConstruct(const KeyT &Key) {
258    BucketT *TheBucket;
259    if (LookupBucketFor(Key, TheBucket))
260      return *TheBucket;
261
262    return *InsertIntoBucket(Key, ValueT(), TheBucket);
263  }
264
265  ValueT &operator[](const KeyT &Key) {
266    return FindAndConstruct(Key).second;
267  }
268
269  DenseMap& operator=(const DenseMap& other) {
270    CopyFrom(other);
271    return *this;
272  }
273
274private:
275  void CopyFrom(const DenseMap& other) {
276    if (NumBuckets != 0 && (!KeyInfoT::isPod() || !ValueInfoT::isPod())) {
277      const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
278      for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
279        if (!KeyInfoT::isEqual(P->first, EmptyKey) &&
280            !KeyInfoT::isEqual(P->first, TombstoneKey))
281          P->second.~ValueT();
282        P->first.~KeyT();
283      }
284    }
285
286    NumEntries = other.NumEntries;
287    NumTombstones = other.NumTombstones;
288
289    if (NumBuckets)
290      operator delete(Buckets);
291    Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT) *
292                                                 other.NumBuckets));
293
294    if (KeyInfoT::isPod() && ValueInfoT::isPod())
295      memcpy(Buckets, other.Buckets, other.NumBuckets * sizeof(BucketT));
296    else
297      for (size_t i = 0; i < other.NumBuckets; ++i) {
298        new (&Buckets[i].first) KeyT(other.Buckets[i].first);
299        if (!KeyInfoT::isEqual(Buckets[i].first, getEmptyKey()) &&
300            !KeyInfoT::isEqual(Buckets[i].first, getTombstoneKey()))
301          new (&Buckets[i].second) ValueT(other.Buckets[i].second);
302      }
303    NumBuckets = other.NumBuckets;
304  }
305
306  BucketT *InsertIntoBucket(const KeyT &Key, const ValueT &Value,
307                            BucketT *TheBucket) {
308    // If the load of the hash table is more than 3/4, or if fewer than 1/8 of
309    // the buckets are empty (meaning that many are filled with tombstones),
310    // grow the table.
311    //
312    // The later case is tricky.  For example, if we had one empty bucket with
313    // tons of tombstones, failing lookups (e.g. for insertion) would have to
314    // probe almost the entire table until it found the empty bucket.  If the
315    // table completely filled with tombstones, no lookup would ever succeed,
316    // causing infinite loops in lookup.
317    if (NumEntries*4 >= NumBuckets*3 ||
318        NumBuckets-(NumEntries+NumTombstones) < NumBuckets/8) {
319      this->grow(NumBuckets * 2);
320      LookupBucketFor(Key, TheBucket);
321    }
322    ++NumEntries;
323
324    // If we are writing over a tombstone, remember this.
325    if (!KeyInfoT::isEqual(TheBucket->first, getEmptyKey()))
326      --NumTombstones;
327
328    TheBucket->first = Key;
329    new (&TheBucket->second) ValueT(Value);
330    return TheBucket;
331  }
332
333  static unsigned getHashValue(const KeyT &Val) {
334    return KeyInfoT::getHashValue(Val);
335  }
336  static const KeyT getEmptyKey() {
337    return KeyInfoT::getEmptyKey();
338  }
339  static const KeyT getTombstoneKey() {
340    return KeyInfoT::getTombstoneKey();
341  }
342
343  /// LookupBucketFor - Lookup the appropriate bucket for Val, returning it in
344  /// FoundBucket.  If the bucket contains the key and a value, this returns
345  /// true, otherwise it returns a bucket with an empty marker or tombstone and
346  /// returns false.
347  bool LookupBucketFor(const KeyT &Val, BucketT *&FoundBucket) const {
348    unsigned BucketNo = getHashValue(Val);
349    unsigned ProbeAmt = 1;
350    BucketT *BucketsPtr = Buckets;
351
352    // FoundTombstone - Keep track of whether we find a tombstone while probing.
353    BucketT *FoundTombstone = 0;
354    const KeyT EmptyKey = getEmptyKey();
355    const KeyT TombstoneKey = getTombstoneKey();
356    assert(!KeyInfoT::isEqual(Val, EmptyKey) &&
357           !KeyInfoT::isEqual(Val, TombstoneKey) &&
358           "Empty/Tombstone value shouldn't be inserted into map!");
359
360    while (1) {
361      BucketT *ThisBucket = BucketsPtr + (BucketNo & (NumBuckets-1));
362      // Found Val's bucket?  If so, return it.
363      if (KeyInfoT::isEqual(ThisBucket->first, Val)) {
364        FoundBucket = ThisBucket;
365        return true;
366      }
367
368      // If we found an empty bucket, the key doesn't exist in the set.
369      // Insert it and return the default value.
370      if (KeyInfoT::isEqual(ThisBucket->first, EmptyKey)) {
371        // If we've already seen a tombstone while probing, fill it in instead
372        // of the empty bucket we eventually probed to.
373        if (FoundTombstone) ThisBucket = FoundTombstone;
374        FoundBucket = FoundTombstone ? FoundTombstone : ThisBucket;
375        return false;
376      }
377
378      // If this is a tombstone, remember it.  If Val ends up not in the map, we
379      // prefer to return it than something that would require more probing.
380      if (KeyInfoT::isEqual(ThisBucket->first, TombstoneKey) && !FoundTombstone)
381        FoundTombstone = ThisBucket;  // Remember the first tombstone found.
382
383      // Otherwise, it's a hash collision or a tombstone, continue quadratic
384      // probing.
385      BucketNo += ProbeAmt++;
386    }
387  }
388
389  void init(unsigned InitBuckets) {
390    NumEntries = 0;
391    NumTombstones = 0;
392    NumBuckets = InitBuckets;
393    assert(InitBuckets && (InitBuckets & (InitBuckets-1)) == 0 &&
394           "# initial buckets must be a power of two!");
395    Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT)*InitBuckets));
396    // Initialize all the keys to EmptyKey.
397    const KeyT EmptyKey = getEmptyKey();
398    for (unsigned i = 0; i != InitBuckets; ++i)
399      new (&Buckets[i].first) KeyT(EmptyKey);
400  }
401
402  void grow(unsigned AtLeast) {
403    unsigned OldNumBuckets = NumBuckets;
404    BucketT *OldBuckets = Buckets;
405
406    // Double the number of buckets.
407    while (NumBuckets <= AtLeast)
408      NumBuckets <<= 1;
409    NumTombstones = 0;
410    Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT)*NumBuckets));
411
412    // Initialize all the keys to EmptyKey.
413    const KeyT EmptyKey = getEmptyKey();
414    for (unsigned i = 0, e = NumBuckets; i != e; ++i)
415      new (&Buckets[i].first) KeyT(EmptyKey);
416
417    // Insert all the old elements.
418    const KeyT TombstoneKey = getTombstoneKey();
419    for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) {
420      if (!KeyInfoT::isEqual(B->first, EmptyKey) &&
421          !KeyInfoT::isEqual(B->first, TombstoneKey)) {
422        // Insert the key/value into the new table.
423        BucketT *DestBucket;
424        bool FoundVal = LookupBucketFor(B->first, DestBucket);
425        FoundVal = FoundVal; // silence warning.
426        assert(!FoundVal && "Key already in new map?");
427        DestBucket->first = B->first;
428        new (&DestBucket->second) ValueT(B->second);
429
430        // Free the value.
431        B->second.~ValueT();
432      }
433      B->first.~KeyT();
434    }
435
436    // Free the old table.
437    operator delete(OldBuckets);
438  }
439
440  void shrink_and_clear() {
441    unsigned OldNumBuckets = NumBuckets;
442    BucketT *OldBuckets = Buckets;
443
444    // Reduce the number of buckets.
445    NumBuckets = NumEntries > 32 ? 1 << (Log2_32_Ceil(NumEntries) + 1)
446                                 : 64;
447    NumTombstones = 0;
448    Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT)*NumBuckets));
449
450    // Initialize all the keys to EmptyKey.
451    const KeyT EmptyKey = getEmptyKey();
452    for (unsigned i = 0, e = NumBuckets; i != e; ++i)
453      new (&Buckets[i].first) KeyT(EmptyKey);
454
455    // Free the old buckets.
456    const KeyT TombstoneKey = getTombstoneKey();
457    for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) {
458      if (!KeyInfoT::isEqual(B->first, EmptyKey) &&
459          !KeyInfoT::isEqual(B->first, TombstoneKey)) {
460        // Free the value.
461        B->second.~ValueT();
462      }
463      B->first.~KeyT();
464    }
465
466    // Free the old table.
467    operator delete(OldBuckets);
468
469    NumEntries = 0;
470  }
471};
472
473template<typename KeyT, typename ValueT, typename KeyInfoT, typename ValueInfoT>
474class DenseMapIterator {
475  typedef std::pair<KeyT, ValueT> BucketT;
476protected:
477  const BucketT *Ptr, *End;
478public:
479  DenseMapIterator(void) : Ptr(0), End(0) {}
480
481  DenseMapIterator(const BucketT *Pos, const BucketT *E) : Ptr(Pos), End(E) {
482    AdvancePastEmptyBuckets();
483  }
484
485  std::pair<KeyT, ValueT> &operator*() const {
486    return *const_cast<BucketT*>(Ptr);
487  }
488  std::pair<KeyT, ValueT> *operator->() const {
489    return const_cast<BucketT*>(Ptr);
490  }
491
492  bool operator==(const DenseMapIterator &RHS) const {
493    return Ptr == RHS.Ptr;
494  }
495  bool operator!=(const DenseMapIterator &RHS) const {
496    return Ptr != RHS.Ptr;
497  }
498
499  inline DenseMapIterator& operator++() {          // Preincrement
500    ++Ptr;
501    AdvancePastEmptyBuckets();
502    return *this;
503  }
504  DenseMapIterator operator++(int) {        // Postincrement
505    DenseMapIterator tmp = *this; ++*this; return tmp;
506  }
507
508private:
509  void AdvancePastEmptyBuckets() {
510    const KeyT Empty = KeyInfoT::getEmptyKey();
511    const KeyT Tombstone = KeyInfoT::getTombstoneKey();
512
513    while (Ptr != End &&
514           (KeyInfoT::isEqual(Ptr->first, Empty) ||
515            KeyInfoT::isEqual(Ptr->first, Tombstone)))
516      ++Ptr;
517  }
518};
519
520template<typename KeyT, typename ValueT, typename KeyInfoT, typename ValueInfoT>
521class DenseMapConstIterator : public DenseMapIterator<KeyT, ValueT, KeyInfoT> {
522public:
523  DenseMapConstIterator(void) : DenseMapIterator<KeyT, ValueT, KeyInfoT>() {}
524  DenseMapConstIterator(const std::pair<KeyT, ValueT> *Pos,
525                        const std::pair<KeyT, ValueT> *E)
526    : DenseMapIterator<KeyT, ValueT, KeyInfoT>(Pos, E) {
527  }
528  const std::pair<KeyT, ValueT> &operator*() const {
529    return *this->Ptr;
530  }
531  const std::pair<KeyT, ValueT> *operator->() const {
532    return this->Ptr;
533  }
534};
535
536} // end namespace llvm
537
538#endif
539