DenseMap.h revision b6bbe6320b4a60b7399eea08426aec834701d514 
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<uint32_t> {
48  static inline uint32_t getEmptyKey() { return ~0; }
49  static inline uint32_t getTombstoneKey() { return ~0 - 1; }
50  static unsigned getHashValue(const uint32_t& Val) { return Val * 37; }
51  static bool isPod() { return true; }
52  static bool isEqual(const uint32_t& LHS, const uint32_t& RHS) {
53  return LHS == RHS;
54  }
55};
56
57// Provide DenseMapInfo for all pairs whose members have info.
58template<typename T, typename U>
59struct DenseMapInfo<std::pair<T, U> > {
60  typedef std::pair<T, U> Pair;
61  typedef DenseMapInfo<T> FirstInfo;
62  typedef DenseMapInfo<U> SecondInfo;
63
64  static inline Pair getEmptyKey() {
65    return std::make_pair(FirstInfo::getEmptyKey(),
66                          SecondInfo::getEmptyKey());
67  }
68  static inline Pair getTombstoneKey() {
69    return std::make_pair(FirstInfo::getTombstoneKey(),
70                            SecondInfo::getEmptyKey());
71  }
72  static unsigned getHashValue(const Pair& PairVal) {
73    uint64_t key = (uint64_t)FirstInfo::getHashValue(PairVal.first) << 32
74          | (uint64_t)SecondInfo::getHashValue(PairVal.second);
75    key += ~(key << 32);
76    key ^= (key >> 22);
77    key += ~(key << 13);
78    key ^= (key >> 8);
79    key += (key << 3);
80    key ^= (key >> 15);
81    key += ~(key << 27);
82    key ^= (key >> 31);
83    return (unsigned)key;
84  }
85  static bool isEqual(const Pair& LHS, const Pair& RHS) { return LHS == RHS; }
86  static bool isPod() { return FirstInfo::isPod() && SecondInfo::isPod(); }
87};
88
89template<typename KeyT, typename ValueT,
90         typename KeyInfoT = DenseMapInfo<KeyT>,
91         typename ValueInfoT = DenseMapInfo<ValueT> >
92class DenseMapIterator;
93template<typename KeyT, typename ValueT,
94         typename KeyInfoT = DenseMapInfo<KeyT>,
95         typename ValueInfoT = DenseMapInfo<ValueT> >
96class DenseMapConstIterator;
97
98template<typename KeyT, typename ValueT,
99         typename KeyInfoT = DenseMapInfo<KeyT>,
100         typename ValueInfoT = DenseMapInfo<ValueT> >
101class DenseMap {
102  typedef std::pair<KeyT, ValueT> BucketT;
103  unsigned NumBuckets;
104  BucketT *Buckets;
105
106  unsigned NumEntries;
107  unsigned NumTombstones;
108public:
109  typedef KeyT key_type;
110  typedef ValueT mapped_type;
111  typedef BucketT value_type;
112
113  DenseMap(const DenseMap& other) {
114    NumBuckets = 0;
115    CopyFrom(other);
116  }
117
118  explicit DenseMap(unsigned NumInitBuckets = 64) {
119    init(NumInitBuckets);
120  }
121
122  ~DenseMap() {
123    const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
124    for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
125      if (!KeyInfoT::isEqual(P->first, EmptyKey) &&
126          !KeyInfoT::isEqual(P->first, TombstoneKey))
127        P->second.~ValueT();
128      P->first.~KeyT();
129    }
130    operator delete(Buckets);
131  }
132
133  typedef DenseMapIterator<KeyT, ValueT, KeyInfoT> iterator;
134  typedef DenseMapConstIterator<KeyT, ValueT, KeyInfoT> const_iterator;
135  inline iterator begin() {
136     return iterator(Buckets, Buckets+NumBuckets);
137  }
138  inline iterator end() {
139    return iterator(Buckets+NumBuckets, Buckets+NumBuckets);
140  }
141  inline const_iterator begin() const {
142    return const_iterator(Buckets, Buckets+NumBuckets);
143  }
144  inline const_iterator end() const {
145    return const_iterator(Buckets+NumBuckets, Buckets+NumBuckets);
146  }
147
148  bool empty() const { return NumEntries == 0; }
149  unsigned size() const { return NumEntries; }
150
151  /// Grow the densemap so that it has at least Size buckets. Does not shrink
152  void resize(size_t Size) { grow(Size); }
153
154  void clear() {
155    // If the capacity of the array is huge, and the # elements used is small,
156    // shrink the array.
157    if (NumEntries * 4 < NumBuckets && NumBuckets > 64) {
158      shrink_and_clear();
159      return;
160    }
161
162    const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
163    for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
164      if (!KeyInfoT::isEqual(P->first, EmptyKey)) {
165        if (!KeyInfoT::isEqual(P->first, TombstoneKey)) {
166          P->second.~ValueT();
167          --NumEntries;
168        }
169        P->first = EmptyKey;
170      }
171    }
172    assert(NumEntries == 0 && "Node count imbalance!");
173    NumTombstones = 0;
174  }
175
176  /// count - Return true if the specified key is in the map.
177  bool count(const KeyT &Val) const {
178    BucketT *TheBucket;
179    return LookupBucketFor(Val, TheBucket);
180  }
181
182  iterator find(const KeyT &Val) {
183    BucketT *TheBucket;
184    if (LookupBucketFor(Val, TheBucket))
185      return iterator(TheBucket, Buckets+NumBuckets);
186    return end();
187  }
188  const_iterator find(const KeyT &Val) const {
189    BucketT *TheBucket;
190    if (LookupBucketFor(Val, TheBucket))
191      return const_iterator(TheBucket, Buckets+NumBuckets);
192    return end();
193  }
194
195  /// lookup - Return the entry for the specified key, or a default
196  /// constructed value if no such entry exists.
197  ValueT lookup(const KeyT &Val) const {
198    BucketT *TheBucket;
199    if (LookupBucketFor(Val, TheBucket))
200      return TheBucket->second;
201    return ValueT();
202  }
203
204  std::pair<iterator, bool> insert(const std::pair<KeyT, ValueT> &KV) {
205    BucketT *TheBucket;
206    if (LookupBucketFor(KV.first, TheBucket))
207      return std::make_pair(iterator(TheBucket, Buckets+NumBuckets),
208                            false); // Already in map.
209
210    // Otherwise, insert the new element.
211    TheBucket = InsertIntoBucket(KV.first, KV.second, TheBucket);
212    return std::make_pair(iterator(TheBucket, Buckets+NumBuckets),
213                          true);
214  }
215
216  /// insert - Range insertion of pairs.
217  template<typename InputIt>
218  void insert(InputIt I, InputIt E) {
219    for (; I != E; ++I)
220      insert(*I);
221  }
222
223
224  bool erase(const KeyT &Val) {
225    BucketT *TheBucket;
226    if (!LookupBucketFor(Val, TheBucket))
227      return false; // not in map.
228
229    TheBucket->second.~ValueT();
230    TheBucket->first = getTombstoneKey();
231    --NumEntries;
232    ++NumTombstones;
233    return true;
234  }
235  bool erase(iterator I) {
236    BucketT *TheBucket = &*I;
237    TheBucket->second.~ValueT();
238    TheBucket->first = getTombstoneKey();
239    --NumEntries;
240    ++NumTombstones;
241    return true;
242  }
243
244  value_type& FindAndConstruct(const KeyT &Key) {
245    BucketT *TheBucket;
246    if (LookupBucketFor(Key, TheBucket))
247      return *TheBucket;
248
249    return *InsertIntoBucket(Key, ValueT(), TheBucket);
250  }
251
252  ValueT &operator[](const KeyT &Key) {
253    return FindAndConstruct(Key).second;
254  }
255
256  DenseMap& operator=(const DenseMap& other) {
257    CopyFrom(other);
258    return *this;
259  }
260
261private:
262  void CopyFrom(const DenseMap& other) {
263    if (NumBuckets != 0 && (!KeyInfoT::isPod() || !ValueInfoT::isPod())) {
264      const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
265      for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
266        if (!KeyInfoT::isEqual(P->first, EmptyKey) &&
267            !KeyInfoT::isEqual(P->first, TombstoneKey))
268          P->second.~ValueT();
269        P->first.~KeyT();
270      }
271    }
272
273    NumEntries = other.NumEntries;
274    NumTombstones = other.NumTombstones;
275
276    if (NumBuckets)
277      operator delete(Buckets);
278    Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT) *
279                                                 other.NumBuckets));
280
281    if (KeyInfoT::isPod() && ValueInfoT::isPod())
282      memcpy(Buckets, other.Buckets, other.NumBuckets * sizeof(BucketT));
283    else
284      for (size_t i = 0; i < other.NumBuckets; ++i) {
285        new (&Buckets[i].first) KeyT(other.Buckets[i].first);
286        if (!KeyInfoT::isEqual(Buckets[i].first, getEmptyKey()) &&
287            !KeyInfoT::isEqual(Buckets[i].first, getTombstoneKey()))
288          new (&Buckets[i].second) ValueT(other.Buckets[i].second);
289      }
290    NumBuckets = other.NumBuckets;
291  }
292
293  BucketT *InsertIntoBucket(const KeyT &Key, const ValueT &Value,
294                            BucketT *TheBucket) {
295    // If the load of the hash table is more than 3/4, or if fewer than 1/8 of
296    // the buckets are empty (meaning that many are filled with tombstones),
297    // grow the table.
298    //
299    // The later case is tricky.  For example, if we had one empty bucket with
300    // tons of tombstones, failing lookups (e.g. for insertion) would have to
301    // probe almost the entire table until it found the empty bucket.  If the
302    // table completely filled with tombstones, no lookup would ever succeed,
303    // causing infinite loops in lookup.
304    if (NumEntries*4 >= NumBuckets*3 ||
305        NumBuckets-(NumEntries+NumTombstones) < NumBuckets/8) {
306      this->grow(NumBuckets * 2);
307      LookupBucketFor(Key, TheBucket);
308    }
309    ++NumEntries;
310
311    // If we are writing over a tombstone, remember this.
312    if (!KeyInfoT::isEqual(TheBucket->first, getEmptyKey()))
313      --NumTombstones;
314
315    TheBucket->first = Key;
316    new (&TheBucket->second) ValueT(Value);
317    return TheBucket;
318  }
319
320  static unsigned getHashValue(const KeyT &Val) {
321    return KeyInfoT::getHashValue(Val);
322  }
323  static const KeyT getEmptyKey() {
324    return KeyInfoT::getEmptyKey();
325  }
326  static const KeyT getTombstoneKey() {
327    return KeyInfoT::getTombstoneKey();
328  }
329
330  /// LookupBucketFor - Lookup the appropriate bucket for Val, returning it in
331  /// FoundBucket.  If the bucket contains the key and a value, this returns
332  /// true, otherwise it returns a bucket with an empty marker or tombstone and
333  /// returns false.
334  bool LookupBucketFor(const KeyT &Val, BucketT *&FoundBucket) const {
335    unsigned BucketNo = getHashValue(Val);
336    unsigned ProbeAmt = 1;
337    BucketT *BucketsPtr = Buckets;
338
339    // FoundTombstone - Keep track of whether we find a tombstone while probing.
340    BucketT *FoundTombstone = 0;
341    const KeyT EmptyKey = getEmptyKey();
342    const KeyT TombstoneKey = getTombstoneKey();
343    assert(!KeyInfoT::isEqual(Val, EmptyKey) &&
344           !KeyInfoT::isEqual(Val, TombstoneKey) &&
345           "Empty/Tombstone value shouldn't be inserted into map!");
346
347    while (1) {
348      BucketT *ThisBucket = BucketsPtr + (BucketNo & (NumBuckets-1));
349      // Found Val's bucket?  If so, return it.
350      if (KeyInfoT::isEqual(ThisBucket->first, Val)) {
351        FoundBucket = ThisBucket;
352        return true;
353      }
354
355      // If we found an empty bucket, the key doesn't exist in the set.
356      // Insert it and return the default value.
357      if (KeyInfoT::isEqual(ThisBucket->first, EmptyKey)) {
358        // If we've already seen a tombstone while probing, fill it in instead
359        // of the empty bucket we eventually probed to.
360        if (FoundTombstone) ThisBucket = FoundTombstone;
361        FoundBucket = FoundTombstone ? FoundTombstone : ThisBucket;
362        return false;
363      }
364
365      // If this is a tombstone, remember it.  If Val ends up not in the map, we
366      // prefer to return it than something that would require more probing.
367      if (KeyInfoT::isEqual(ThisBucket->first, TombstoneKey) && !FoundTombstone)
368        FoundTombstone = ThisBucket;  // Remember the first tombstone found.
369
370      // Otherwise, it's a hash collision or a tombstone, continue quadratic
371      // probing.
372      BucketNo += ProbeAmt++;
373    }
374  }
375
376  void init(unsigned InitBuckets) {
377    NumEntries = 0;
378    NumTombstones = 0;
379    NumBuckets = InitBuckets;
380    assert(InitBuckets && (InitBuckets & (InitBuckets-1)) == 0 &&
381           "# initial buckets must be a power of two!");
382    Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT)*InitBuckets));
383    // Initialize all the keys to EmptyKey.
384    const KeyT EmptyKey = getEmptyKey();
385    for (unsigned i = 0; i != InitBuckets; ++i)
386      new (&Buckets[i].first) KeyT(EmptyKey);
387  }
388
389  void grow(unsigned AtLeast) {
390    unsigned OldNumBuckets = NumBuckets;
391    BucketT *OldBuckets = Buckets;
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        FoundVal = 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    // Free the old table.
424    operator delete(OldBuckets);
425  }
426
427  void shrink_and_clear() {
428    unsigned OldNumBuckets = NumBuckets;
429    BucketT *OldBuckets = Buckets;
430
431    // Reduce the number of buckets.
432    NumBuckets = NumEntries > 32 ? 1 << (Log2_32_Ceil(NumEntries) + 1)
433                                 : 64;
434    NumTombstones = 0;
435    Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT)*NumBuckets));
436
437    // Initialize all the keys to EmptyKey.
438    const KeyT EmptyKey = getEmptyKey();
439    for (unsigned i = 0, e = NumBuckets; i != e; ++i)
440      new (&Buckets[i].first) KeyT(EmptyKey);
441
442    // Free the old buckets.
443    const KeyT TombstoneKey = getTombstoneKey();
444    for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) {
445      if (!KeyInfoT::isEqual(B->first, EmptyKey) &&
446          !KeyInfoT::isEqual(B->first, TombstoneKey)) {
447        // Free the value.
448        B->second.~ValueT();
449      }
450      B->first.~KeyT();
451    }
452
453    // Free the old table.
454    operator delete(OldBuckets);
455
456    NumEntries = 0;
457  }
458};
459
460template<typename KeyT, typename ValueT, typename KeyInfoT, typename ValueInfoT>
461class DenseMapIterator {
462  typedef std::pair<KeyT, ValueT> BucketT;
463protected:
464  const BucketT *Ptr, *End;
465public:
466  DenseMapIterator(void) : Ptr(0), End(0) {}
467
468  DenseMapIterator(const BucketT *Pos, const BucketT *E) : Ptr(Pos), End(E) {
469    AdvancePastEmptyBuckets();
470  }
471
472  std::pair<KeyT, ValueT> &operator*() const {
473    return *const_cast<BucketT*>(Ptr);
474  }
475  std::pair<KeyT, ValueT> *operator->() const {
476    return const_cast<BucketT*>(Ptr);
477  }
478
479  bool operator==(const DenseMapIterator &RHS) const {
480    return Ptr == RHS.Ptr;
481  }
482  bool operator!=(const DenseMapIterator &RHS) const {
483    return Ptr != RHS.Ptr;
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
507template<typename KeyT, typename ValueT, typename KeyInfoT, typename ValueInfoT>
508class DenseMapConstIterator : public DenseMapIterator<KeyT, ValueT, KeyInfoT> {
509public:
510  DenseMapConstIterator(void) : DenseMapIterator<KeyT, ValueT, KeyInfoT>() {}
511  DenseMapConstIterator(const std::pair<KeyT, ValueT> *Pos,
512                        const std::pair<KeyT, ValueT> *E)
513    : DenseMapIterator<KeyT, ValueT, KeyInfoT>(Pos, E) {
514  }
515  const std::pair<KeyT, ValueT> &operator*() const {
516    return *this->Ptr;
517  }
518  const std::pair<KeyT, ValueT> *operator->() const {
519    return this->Ptr;
520  }
521};
522
523} // end namespace llvm
524
525#endif
526