DenseMap.h revision f8a3ee1d637a747c87f72bc880445e6a82280ff0 
1//===- llvm/ADT/DenseMap.h - Dense probed hash table ------------*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file was developed by Chris Lattner and is distributed under
6// the University of Illinois Open Source 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
46template<typename KeyT, typename ValueT,
47         typename KeyInfoT = DenseMapInfo<KeyT>,
48         typename ValueInfoT = DenseMapInfo<ValueT> >
49class DenseMapIterator;
50template<typename KeyT, typename ValueT,
51         typename KeyInfoT = DenseMapInfo<KeyT>,
52         typename ValueInfoT = DenseMapInfo<ValueT> >
53class DenseMapConstIterator;
54
55template<typename KeyT, typename ValueT,
56         typename KeyInfoT = DenseMapInfo<KeyT>,
57         typename ValueInfoT = DenseMapInfo<ValueT> >
58class DenseMap {
59  typedef std::pair<KeyT, ValueT> BucketT;
60  unsigned NumBuckets;
61  BucketT *Buckets;
62
63  unsigned NumEntries;
64  unsigned NumTombstones;
65public:
66  DenseMap(const DenseMap& other) {
67    NumBuckets = 0;
68    CopyFrom(other);
69  }
70
71  explicit DenseMap(unsigned NumInitBuckets = 64) {
72    init(NumInitBuckets);
73  }
74
75  ~DenseMap() {
76    const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
77    for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
78      if (P->first != EmptyKey && P->first != TombstoneKey)
79        P->second.~ValueT();
80      P->first.~KeyT();
81    }
82    delete[] reinterpret_cast<char*>(Buckets);
83  }
84
85  typedef DenseMapIterator<KeyT, ValueT, KeyInfoT> iterator;
86  typedef DenseMapConstIterator<KeyT, ValueT, KeyInfoT> const_iterator;
87  inline iterator begin() {
88     return iterator(Buckets, Buckets+NumBuckets);
89  }
90  inline iterator end() {
91    return iterator(Buckets+NumBuckets, Buckets+NumBuckets);
92  }
93  inline const_iterator begin() const {
94    return const_iterator(Buckets, Buckets+NumBuckets);
95  }
96  inline const_iterator end() const {
97    return const_iterator(Buckets+NumBuckets, Buckets+NumBuckets);
98  }
99
100  bool empty() const { return NumEntries == 0; }
101  unsigned size() const { return NumEntries; }
102
103  /// Grow the densemap so that it has at least Size buckets. Does not shrink
104  void resize(size_t Size) { grow(Size); }
105
106  void clear() {
107    // If the capacity of the array is huge, and the # elements used is small,
108    // shrink the array.
109    if (NumEntries * 4 < NumBuckets && NumBuckets > 64) {
110      shrink_and_clear();
111      return;
112    }
113
114    const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
115    for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
116      if (P->first != EmptyKey) {
117        if (P->first != TombstoneKey) {
118          P->second.~ValueT();
119          --NumEntries;
120        }
121        P->first = EmptyKey;
122      }
123    }
124    assert(NumEntries == 0 && "Node count imbalance!");
125    NumTombstones = 0;
126  }
127
128  /// count - Return true if the specified key is in the map.
129  bool count(const KeyT &Val) const {
130    BucketT *TheBucket;
131    return LookupBucketFor(Val, TheBucket);
132  }
133
134  iterator find(const KeyT &Val) {
135    BucketT *TheBucket;
136    if (LookupBucketFor(Val, TheBucket))
137      return iterator(TheBucket, Buckets+NumBuckets);
138    return end();
139  }
140  const_iterator find(const KeyT &Val) const {
141    BucketT *TheBucket;
142    if (LookupBucketFor(Val, TheBucket))
143      return const_iterator(TheBucket, Buckets+NumBuckets);
144    return end();
145  }
146
147  bool insert(const std::pair<KeyT, ValueT> &KV) {
148    BucketT *TheBucket;
149    if (LookupBucketFor(KV.first, TheBucket))
150      return false; // Already in map.
151
152    // Otherwise, insert the new element.
153    InsertIntoBucket(KV.first, KV.second, TheBucket);
154    return true;
155  }
156
157  bool erase(const KeyT &Val) {
158    BucketT *TheBucket;
159    if (!LookupBucketFor(Val, TheBucket))
160      return false; // not in map.
161
162    TheBucket->second.~ValueT();
163    TheBucket->first = getTombstoneKey();
164    --NumEntries;
165    ++NumTombstones;
166    return true;
167  }
168  bool erase(iterator I) {
169    BucketT *TheBucket = &*I;
170    TheBucket->second.~ValueT();
171    TheBucket->first = getTombstoneKey();
172    --NumEntries;
173    ++NumTombstones;
174    return true;
175  }
176
177  ValueT &operator[](const KeyT &Key) {
178    BucketT *TheBucket;
179    if (LookupBucketFor(Key, TheBucket))
180      return TheBucket->second;
181
182    return InsertIntoBucket(Key, ValueT(), TheBucket)->second;
183  }
184
185  DenseMap& operator=(const DenseMap& other) {
186    CopyFrom(other);
187    return *this;
188  }
189
190private:
191  void CopyFrom(const DenseMap& other) {
192    if (NumBuckets != 0 && (!KeyInfoT::isPod() || !ValueInfoT::isPod())) {
193      const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
194      for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
195        if (P->first != EmptyKey && P->first != TombstoneKey)
196          P->second.~ValueT();
197        P->first.~KeyT();
198      }
199    }
200
201    NumEntries = other.NumEntries;
202    NumTombstones = other.NumTombstones;
203
204    if (NumBuckets)
205      delete[] reinterpret_cast<char*>(Buckets);
206    Buckets = reinterpret_cast<BucketT*>(new char[sizeof(BucketT) *
207                                                  other.NumBuckets]);
208
209    if (KeyInfoT::isPod() && ValueInfoT::isPod())
210      memcpy(Buckets, other.Buckets, other.NumBuckets * sizeof(BucketT));
211    else
212      for (size_t i = 0; i < other.NumBuckets; ++i) {
213        new (Buckets[i].first) KeyT(other.Buckets[i].first);
214        if (Buckets[i].first != getEmptyKey() &&
215            Buckets[i].first != getTombstoneKey())
216          new (&Buckets[i].second) ValueT(other.Buckets[i].second);
217      }
218    NumBuckets = other.NumBuckets;
219  }
220
221  BucketT *InsertIntoBucket(const KeyT &Key, const ValueT &Value,
222                            BucketT *TheBucket) {
223    // If the load of the hash table is more than 3/4, or if fewer than 1/8 of
224    // the buckets are empty (meaning that many are filled with tombstones),
225    // grow the table.
226    //
227    // The later case is tricky.  For example, if we had one empty bucket with
228    // tons of tombstones, failing lookups (e.g. for insertion) would have to
229    // probe almost the entire table until it found the empty bucket.  If the
230    // table completely filled with tombstones, no lookup would ever succeed,
231    // causing infinite loops in lookup.
232    if (NumEntries*4 >= NumBuckets*3 ||
233        NumBuckets-(NumEntries+NumTombstones) < NumBuckets/8) {
234      this->grow(NumBuckets * 2);
235      LookupBucketFor(Key, TheBucket);
236    }
237    ++NumEntries;
238
239    // If we are writing over a tombstone, remember this.
240    if (TheBucket->first != getEmptyKey())
241      --NumTombstones;
242
243    TheBucket->first = Key;
244    new (&TheBucket->second) ValueT(Value);
245    return TheBucket;
246  }
247
248  static unsigned getHashValue(const KeyT &Val) {
249    return KeyInfoT::getHashValue(Val);
250  }
251  static const KeyT getEmptyKey() {
252    return KeyInfoT::getEmptyKey();
253  }
254  static const KeyT getTombstoneKey() {
255    return KeyInfoT::getTombstoneKey();
256  }
257
258  /// LookupBucketFor - Lookup the appropriate bucket for Val, returning it in
259  /// FoundBucket.  If the bucket contains the key and a value, this returns
260  /// true, otherwise it returns a bucket with an empty marker or tombstone and
261  /// returns false.
262  bool LookupBucketFor(const KeyT &Val, BucketT *&FoundBucket) const {
263    unsigned BucketNo = getHashValue(Val);
264    unsigned ProbeAmt = 1;
265    BucketT *BucketsPtr = Buckets;
266
267    // FoundTombstone - Keep track of whether we find a tombstone while probing.
268    BucketT *FoundTombstone = 0;
269    const KeyT EmptyKey = getEmptyKey();
270    const KeyT TombstoneKey = getTombstoneKey();
271    assert(Val != EmptyKey && Val != TombstoneKey &&
272           "Empty/Tombstone value shouldn't be inserted into map!");
273
274    while (1) {
275      BucketT *ThisBucket = BucketsPtr + (BucketNo & (NumBuckets-1));
276      // Found Val's bucket?  If so, return it.
277      if (KeyInfoT::isEqual(ThisBucket->first, Val)) {
278        FoundBucket = ThisBucket;
279        return true;
280      }
281
282      // If we found an empty bucket, the key doesn't exist in the set.
283      // Insert it and return the default value.
284      if (KeyInfoT::isEqual(ThisBucket->first, EmptyKey)) {
285        // If we've already seen a tombstone while probing, fill it in instead
286        // of the empty bucket we eventually probed to.
287        if (FoundTombstone) ThisBucket = FoundTombstone;
288        FoundBucket = FoundTombstone ? FoundTombstone : ThisBucket;
289        return false;
290      }
291
292      // If this is a tombstone, remember it.  If Val ends up not in the map, we
293      // prefer to return it than something that would require more probing.
294      if (KeyInfoT::isEqual(ThisBucket->first, TombstoneKey) && !FoundTombstone)
295        FoundTombstone = ThisBucket;  // Remember the first tombstone found.
296
297      // Otherwise, it's a hash collision or a tombstone, continue quadratic
298      // probing.
299      BucketNo += ProbeAmt++;
300    }
301  }
302
303  void init(unsigned InitBuckets) {
304    NumEntries = 0;
305    NumTombstones = 0;
306    NumBuckets = InitBuckets;
307    assert(InitBuckets && (InitBuckets & InitBuckets-1) == 0 &&
308           "# initial buckets must be a power of two!");
309    Buckets = reinterpret_cast<BucketT*>(new char[sizeof(BucketT)*InitBuckets]);
310    // Initialize all the keys to EmptyKey.
311    const KeyT EmptyKey = getEmptyKey();
312    for (unsigned i = 0; i != InitBuckets; ++i)
313      new (&Buckets[i].first) KeyT(EmptyKey);
314  }
315
316  void grow(unsigned AtLeast) {
317    unsigned OldNumBuckets = NumBuckets;
318    BucketT *OldBuckets = Buckets;
319
320    // Double the number of buckets.
321    while (NumBuckets <= AtLeast)
322      NumBuckets <<= 1;
323    NumTombstones = 0;
324    Buckets = reinterpret_cast<BucketT*>(new char[sizeof(BucketT)*NumBuckets]);
325
326    // Initialize all the keys to EmptyKey.
327    const KeyT EmptyKey = getEmptyKey();
328    for (unsigned i = 0, e = NumBuckets; i != e; ++i)
329      new (&Buckets[i].first) KeyT(EmptyKey);
330
331    // Insert all the old elements.
332    const KeyT TombstoneKey = getTombstoneKey();
333    for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) {
334      if (B->first != EmptyKey && B->first != TombstoneKey) {
335        // Insert the key/value into the new table.
336        BucketT *DestBucket;
337        bool FoundVal = LookupBucketFor(B->first, DestBucket);
338        FoundVal = FoundVal; // silence warning.
339        assert(!FoundVal && "Key already in new map?");
340        DestBucket->first = B->first;
341        new (&DestBucket->second) ValueT(B->second);
342
343        // Free the value.
344        B->second.~ValueT();
345      }
346      B->first.~KeyT();
347    }
348
349    // Free the old table.
350    delete[] reinterpret_cast<char*>(OldBuckets);
351  }
352
353  void shrink_and_clear() {
354    unsigned OldNumBuckets = NumBuckets;
355    BucketT *OldBuckets = Buckets;
356
357    // Reduce the number of buckets.
358    NumBuckets = NumEntries > 32 ? 1 << (Log2_32_Ceil(NumEntries) + 1)
359                                 : 64;
360    NumTombstones = 0;
361    Buckets = reinterpret_cast<BucketT*>(new char[sizeof(BucketT)*NumBuckets]);
362
363    // Initialize all the keys to EmptyKey.
364    const KeyT EmptyKey = getEmptyKey();
365    for (unsigned i = 0, e = NumBuckets; i != e; ++i)
366      new (&Buckets[i].first) KeyT(EmptyKey);
367
368    // Free the old buckets.
369    const KeyT TombstoneKey = getTombstoneKey();
370    for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) {
371      if (B->first != EmptyKey && B->first != TombstoneKey) {
372        // Free the value.
373        B->second.~ValueT();
374      }
375      B->first.~KeyT();
376    }
377
378    // Free the old table.
379    delete[] reinterpret_cast<char*>(OldBuckets);
380
381    NumEntries = 0;
382  }
383};
384
385template<typename KeyT, typename ValueT, typename KeyInfoT, typename ValueInfoT>
386class DenseMapIterator {
387  typedef std::pair<KeyT, ValueT> BucketT;
388protected:
389  const BucketT *Ptr, *End;
390public:
391  DenseMapIterator(const BucketT *Pos, const BucketT *E) : Ptr(Pos), End(E) {
392    AdvancePastEmptyBuckets();
393  }
394
395  std::pair<KeyT, ValueT> &operator*() const {
396    return *const_cast<BucketT*>(Ptr);
397  }
398  std::pair<KeyT, ValueT> *operator->() const {
399    return const_cast<BucketT*>(Ptr);
400  }
401
402  bool operator==(const DenseMapIterator &RHS) const {
403    return Ptr == RHS.Ptr;
404  }
405  bool operator!=(const DenseMapIterator &RHS) const {
406    return Ptr != RHS.Ptr;
407  }
408
409  inline DenseMapIterator& operator++() {          // Preincrement
410    ++Ptr;
411    AdvancePastEmptyBuckets();
412    return *this;
413  }
414  DenseMapIterator operator++(int) {        // Postincrement
415    DenseMapIterator tmp = *this; ++*this; return tmp;
416  }
417
418private:
419  void AdvancePastEmptyBuckets() {
420    const KeyT Empty = KeyInfoT::getEmptyKey();
421    const KeyT Tombstone = KeyInfoT::getTombstoneKey();
422
423    while (Ptr != End &&
424           (KeyInfoT::isEqual(Ptr->first, Empty) ||
425            KeyInfoT::isEqual(Ptr->first, Tombstone)))
426      ++Ptr;
427  }
428};
429
430template<typename KeyT, typename ValueT, typename KeyInfoT, typename ValueInfoT>
431class DenseMapConstIterator : public DenseMapIterator<KeyT, ValueT, KeyInfoT> {
432public:
433  DenseMapConstIterator(const std::pair<KeyT, ValueT> *Pos,
434                        const std::pair<KeyT, ValueT> *E)
435    : DenseMapIterator<KeyT, ValueT, KeyInfoT>(Pos, E) {
436  }
437  const std::pair<KeyT, ValueT> &operator*() const {
438    return *this->Ptr;
439  }
440  const std::pair<KeyT, ValueT> *operator->() const {
441    return this->Ptr;
442  }
443};
444
445} // end namespace llvm
446
447#endif
448