DenseMap.h revision 4938d347723d452786c1a7c1d1b9ec79121b0040 
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  void clear() {
104    // If the capacity of the array is huge, and the # elements used is small,
105    // shrink the array.
106    if (NumEntries * 4 < NumBuckets && NumBuckets > 64) {
107      shrink_and_clear();
108      return;
109    }
110
111    const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
112    for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
113      if (P->first != EmptyKey) {
114        if (P->first != TombstoneKey) {
115          P->second.~ValueT();
116          --NumEntries;
117        }
118        P->first = EmptyKey;
119      }
120    }
121    assert(NumEntries == 0 && "Node count imbalance!");
122    NumTombstones = 0;
123  }
124
125  /// count - Return true if the specified key is in the map.
126  bool count(const KeyT &Val) const {
127    BucketT *TheBucket;
128    return LookupBucketFor(Val, TheBucket);
129  }
130
131  iterator find(const KeyT &Val) {
132    BucketT *TheBucket;
133    if (LookupBucketFor(Val, TheBucket))
134      return iterator(TheBucket, Buckets+NumBuckets);
135    return end();
136  }
137  const_iterator find(const KeyT &Val) const {
138    BucketT *TheBucket;
139    if (LookupBucketFor(Val, TheBucket))
140      return const_iterator(TheBucket, Buckets+NumBuckets);
141    return end();
142  }
143
144  bool insert(const std::pair<KeyT, ValueT> &KV) {
145    BucketT *TheBucket;
146    if (LookupBucketFor(KV.first, TheBucket))
147      return false; // Already in map.
148
149    // Otherwise, insert the new element.
150    InsertIntoBucket(KV.first, KV.second, TheBucket);
151    return true;
152  }
153
154  bool erase(const KeyT &Val) {
155    BucketT *TheBucket;
156    if (!LookupBucketFor(Val, TheBucket))
157      return false; // not in map.
158
159    TheBucket->second.~ValueT();
160    TheBucket->first = getTombstoneKey();
161    --NumEntries;
162    ++NumTombstones;
163    return true;
164  }
165  bool erase(iterator I) {
166    BucketT *TheBucket = &*I;
167    TheBucket->second.~ValueT();
168    TheBucket->first = getTombstoneKey();
169    --NumEntries;
170    ++NumTombstones;
171    return true;
172  }
173
174  ValueT &operator[](const KeyT &Key) {
175    BucketT *TheBucket;
176    if (LookupBucketFor(Key, TheBucket))
177      return TheBucket->second;
178
179    return InsertIntoBucket(Key, ValueT(), TheBucket)->second;
180  }
181
182  DenseMap& operator=(const DenseMap& other) {
183    CopyFrom(other);
184    return *this;
185  }
186
187private:
188  void CopyFrom(const DenseMap& other) {
189    if (NumBuckets != 0 && (!KeyInfoT::isPod() || !ValueInfoT::isPod())) {
190      const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
191      for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
192        if (P->first != EmptyKey && P->first != TombstoneKey)
193          P->second.~ValueT();
194        P->first.~KeyT();
195      }
196    }
197
198    NumEntries = other.NumEntries;
199    NumTombstones = other.NumTombstones;
200
201    if (NumBuckets)
202      delete[] reinterpret_cast<char*>(Buckets);
203    Buckets = reinterpret_cast<BucketT*>(new char[sizeof(BucketT) *
204                                                  other.NumBuckets]);
205
206    if (KeyInfoT::isPod() && ValueInfoT::isPod())
207      memcpy(Buckets, other.Buckets, other.NumBuckets * sizeof(BucketT));
208    else
209      for (size_t i = 0; i < other.NumBuckets; ++i) {
210        new (Buckets[i].first) KeyT(other.Buckets[i].first);
211        if (Buckets[i].first != getEmptyKey() &&
212            Buckets[i].first != getTombstoneKey())
213          new (&Buckets[i].second) ValueT(other.Buckets[i].second);
214      }
215    NumBuckets = other.NumBuckets;
216  }
217
218  BucketT *InsertIntoBucket(const KeyT &Key, const ValueT &Value,
219                            BucketT *TheBucket) {
220    // If the load of the hash table is more than 3/4, or if fewer than 1/8 of
221    // the buckets are empty (meaning that many are filled with tombstones),
222    // grow the table.
223    //
224    // The later case is tricky.  For example, if we had one empty bucket with
225    // tons of tombstones, failing lookups (e.g. for insertion) would have to
226    // probe almost the entire table until it found the empty bucket.  If the
227    // table completely filled with tombstones, no lookup would ever succeed,
228    // causing infinite loops in lookup.
229    if (NumEntries*4 >= NumBuckets*3 ||
230        NumBuckets-(NumEntries+NumTombstones) < NumBuckets/8) {
231      this->grow();
232      LookupBucketFor(Key, TheBucket);
233    }
234    ++NumEntries;
235
236    // If we are writing over a tombstone, remember this.
237    if (TheBucket->first != getEmptyKey())
238      --NumTombstones;
239
240    TheBucket->first = Key;
241    new (&TheBucket->second) ValueT(Value);
242    return TheBucket;
243  }
244
245  static unsigned getHashValue(const KeyT &Val) {
246    return KeyInfoT::getHashValue(Val);
247  }
248  static const KeyT getEmptyKey() {
249    return KeyInfoT::getEmptyKey();
250  }
251  static const KeyT getTombstoneKey() {
252    return KeyInfoT::getTombstoneKey();
253  }
254
255  /// LookupBucketFor - Lookup the appropriate bucket for Val, returning it in
256  /// FoundBucket.  If the bucket contains the key and a value, this returns
257  /// true, otherwise it returns a bucket with an empty marker or tombstone and
258  /// returns false.
259  bool LookupBucketFor(const KeyT &Val, BucketT *&FoundBucket) const {
260    unsigned BucketNo = getHashValue(Val);
261    unsigned ProbeAmt = 1;
262    BucketT *BucketsPtr = Buckets;
263
264    // FoundTombstone - Keep track of whether we find a tombstone while probing.
265    BucketT *FoundTombstone = 0;
266    const KeyT EmptyKey = getEmptyKey();
267    const KeyT TombstoneKey = getTombstoneKey();
268    assert(Val != EmptyKey && Val != TombstoneKey &&
269           "Empty/Tombstone value shouldn't be inserted into map!");
270
271    while (1) {
272      BucketT *ThisBucket = BucketsPtr + (BucketNo & (NumBuckets-1));
273      // Found Val's bucket?  If so, return it.
274      if (KeyInfoT::isEqual(ThisBucket->first, Val)) {
275        FoundBucket = ThisBucket;
276        return true;
277      }
278
279      // If we found an empty bucket, the key doesn't exist in the set.
280      // Insert it and return the default value.
281      if (KeyInfoT::isEqual(ThisBucket->first, EmptyKey)) {
282        // If we've already seen a tombstone while probing, fill it in instead
283        // of the empty bucket we eventually probed to.
284        if (FoundTombstone) ThisBucket = FoundTombstone;
285        FoundBucket = FoundTombstone ? FoundTombstone : ThisBucket;
286        return false;
287      }
288
289      // If this is a tombstone, remember it.  If Val ends up not in the map, we
290      // prefer to return it than something that would require more probing.
291      if (KeyInfoT::isEqual(ThisBucket->first, TombstoneKey) && !FoundTombstone)
292        FoundTombstone = ThisBucket;  // Remember the first tombstone found.
293
294      // Otherwise, it's a hash collision or a tombstone, continue quadratic
295      // probing.
296      BucketNo += ProbeAmt++;
297    }
298  }
299
300  void init(unsigned InitBuckets) {
301    NumEntries = 0;
302    NumTombstones = 0;
303    NumBuckets = InitBuckets;
304    assert(InitBuckets && (InitBuckets & InitBuckets-1) == 0 &&
305           "# initial buckets must be a power of two!");
306    Buckets = reinterpret_cast<BucketT*>(new char[sizeof(BucketT)*InitBuckets]);
307    // Initialize all the keys to EmptyKey.
308    const KeyT EmptyKey = getEmptyKey();
309    for (unsigned i = 0; i != InitBuckets; ++i)
310      new (&Buckets[i].first) KeyT(EmptyKey);
311  }
312
313  void grow() {
314    unsigned OldNumBuckets = NumBuckets;
315    BucketT *OldBuckets = Buckets;
316
317    // Double the number of buckets.
318    NumBuckets <<= 1;
319    NumTombstones = 0;
320    Buckets = reinterpret_cast<BucketT*>(new char[sizeof(BucketT)*NumBuckets]);
321
322    // Initialize all the keys to EmptyKey.
323    const KeyT EmptyKey = getEmptyKey();
324    for (unsigned i = 0, e = NumBuckets; i != e; ++i)
325      new (&Buckets[i].first) KeyT(EmptyKey);
326
327    // Insert all the old elements.
328    const KeyT TombstoneKey = getTombstoneKey();
329    for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) {
330      if (B->first != EmptyKey && B->first != TombstoneKey) {
331        // Insert the key/value into the new table.
332        BucketT *DestBucket;
333        bool FoundVal = LookupBucketFor(B->first, DestBucket);
334        FoundVal = FoundVal; // silence warning.
335        assert(!FoundVal && "Key already in new map?");
336        DestBucket->first = B->first;
337        new (&DestBucket->second) ValueT(B->second);
338
339        // Free the value.
340        B->second.~ValueT();
341      }
342      B->first.~KeyT();
343    }
344
345    // Free the old table.
346    delete[] reinterpret_cast<char*>(OldBuckets);
347  }
348
349  void shrink_and_clear() {
350    unsigned OldNumBuckets = NumBuckets;
351    BucketT *OldBuckets = Buckets;
352
353    // Reduce the number of buckets.
354    NumBuckets = NumEntries > 32 ? 1 << (Log2_32_Ceil(NumEntries) + 1)
355                                 : 64;
356    NumTombstones = 0;
357    Buckets = reinterpret_cast<BucketT*>(new char[sizeof(BucketT)*NumBuckets]);
358
359    // Initialize all the keys to EmptyKey.
360    const KeyT EmptyKey = getEmptyKey();
361    for (unsigned i = 0, e = NumBuckets; i != e; ++i)
362      new (&Buckets[i].first) KeyT(EmptyKey);
363
364    // Free the old buckets.
365    const KeyT TombstoneKey = getTombstoneKey();
366    for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) {
367      if (B->first != EmptyKey && B->first != TombstoneKey) {
368        // Free the value.
369        B->second.~ValueT();
370      }
371      B->first.~KeyT();
372    }
373
374    // Free the old table.
375    delete[] reinterpret_cast<char*>(OldBuckets);
376
377    NumEntries = 0;
378  }
379};
380
381template<typename KeyT, typename ValueT, typename KeyInfoT, typename ValueInfoT>
382class DenseMapIterator {
383  typedef std::pair<KeyT, ValueT> BucketT;
384protected:
385  const BucketT *Ptr, *End;
386public:
387  DenseMapIterator(const BucketT *Pos, const BucketT *E) : Ptr(Pos), End(E) {
388    AdvancePastEmptyBuckets();
389  }
390
391  std::pair<KeyT, ValueT> &operator*() const {
392    return *const_cast<BucketT*>(Ptr);
393  }
394  std::pair<KeyT, ValueT> *operator->() const {
395    return const_cast<BucketT*>(Ptr);
396  }
397
398  bool operator==(const DenseMapIterator &RHS) const {
399    return Ptr == RHS.Ptr;
400  }
401  bool operator!=(const DenseMapIterator &RHS) const {
402    return Ptr != RHS.Ptr;
403  }
404
405  inline DenseMapIterator& operator++() {          // Preincrement
406    ++Ptr;
407    AdvancePastEmptyBuckets();
408    return *this;
409  }
410  DenseMapIterator operator++(int) {        // Postincrement
411    DenseMapIterator tmp = *this; ++*this; return tmp;
412  }
413
414private:
415  void AdvancePastEmptyBuckets() {
416    const KeyT Empty = KeyInfoT::getEmptyKey();
417    const KeyT Tombstone = KeyInfoT::getTombstoneKey();
418
419    while (Ptr != End &&
420           (KeyInfoT::isEqual(Ptr->first, Empty) ||
421            KeyInfoT::isEqual(Ptr->first, Tombstone)))
422      ++Ptr;
423  }
424};
425
426template<typename KeyT, typename ValueT, typename KeyInfoT, typename ValueInfoT>
427class DenseMapConstIterator : public DenseMapIterator<KeyT, ValueT, KeyInfoT> {
428public:
429  DenseMapConstIterator(const std::pair<KeyT, ValueT> *Pos,
430                        const std::pair<KeyT, ValueT> *E)
431    : DenseMapIterator<KeyT, ValueT, KeyInfoT>(Pos, E) {
432  }
433  const std::pair<KeyT, ValueT> &operator*() const {
434    return *this->Ptr;
435  }
436  const std::pair<KeyT, ValueT> *operator->() const {
437    return this->Ptr;
438  }
439};
440
441} // end namespace llvm
442
443#endif
444