1 //===- llvm/ADT/DenseMap.h - Dense probed hash table ------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
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.
8 //===----------------------------------------------------------------------===//
10 // This file defines the DenseMap class.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_ADT_DENSEMAP_H
15 #define LLVM_ADT_DENSEMAP_H
17 #include "llvm/Support/DataTypes.h"
24 struct DenseMapKeyInfo {
25 //static inline T getEmptyKey();
26 //static inline T getTombstoneKey();
27 //static unsigned getHashValue(const T &Val);
31 // Provide DenseMapKeyInfo for all pointers.
33 struct DenseMapKeyInfo<T*> {
34 static inline T* getEmptyKey() { return (T*)-1; }
35 static inline T* getTombstoneKey() { return (T*)-2; }
36 static unsigned getHashValue(const T *PtrVal) {
37 return (unsigned)((uintptr_t)PtrVal >> 4) ^
38 (unsigned)((uintptr_t)PtrVal >> 9);
40 static bool isPod() { return true; }
43 template<typename KeyT, typename ValueT,
44 typename KeyInfoT = DenseMapKeyInfo<KeyT> >
45 class DenseMapIterator;
46 template<typename KeyT, typename ValueT,
47 typename KeyInfoT = DenseMapKeyInfo<KeyT> >
48 class DenseMapConstIterator;
50 template<typename KeyT, typename ValueT,
51 typename KeyInfoT = DenseMapKeyInfo<KeyT> >
53 typedef std::pair<KeyT, ValueT> BucketT;
58 unsigned NumTombstones;
59 DenseMap(const DenseMap &); // not implemented.
61 explicit DenseMap(unsigned NumInitBuckets = 64) {
65 const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
66 for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
67 if (P->first != EmptyKey && P->first != TombstoneKey)
71 delete[] (char*)Buckets;
74 typedef DenseMapIterator<KeyT, ValueT, KeyInfoT> iterator;
75 typedef DenseMapConstIterator<KeyT, ValueT, KeyInfoT> const_iterator;
76 inline iterator begin() {
77 return iterator(Buckets, Buckets+NumBuckets);
79 inline iterator end() {
80 return iterator(Buckets+NumBuckets, Buckets+NumBuckets);
82 inline const_iterator begin() const {
83 return const_iterator(Buckets, Buckets+NumBuckets);
85 inline const_iterator end() const {
86 return const_iterator(Buckets+NumBuckets, Buckets+NumBuckets);
89 bool empty() const { return NumEntries == 0; }
90 unsigned size() const { return NumEntries; }
93 if (NumEntries * 4 < NumBuckets && NumBuckets > 64) {
98 const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
99 for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
100 if (P->first != EmptyKey && P->first != TombstoneKey) {
106 assert(NumEntries == 0 && "Node count imbalance!");
110 /// count - Return true if the specified key is in the map.
111 bool count(const KeyT &Val) const {
113 return LookupBucketFor(Val, TheBucket);
116 iterator find(const KeyT &Val) {
118 if (LookupBucketFor(Val, TheBucket))
119 return iterator(TheBucket, Buckets+NumBuckets);
122 const_iterator find(const KeyT &Val) const {
124 if (LookupBucketFor(Val, TheBucket))
125 return const_iterator(TheBucket, Buckets+NumBuckets);
129 bool insert(const std::pair<KeyT, ValueT> &KV) {
131 if (LookupBucketFor(KV.first, TheBucket))
132 return false; // Already in map.
134 // Otherwise, insert the new element.
135 InsertIntoBucket(KV.first, KV.second, TheBucket);
139 bool erase(const KeyT &Val) {
141 if (!LookupBucketFor(Val, TheBucket))
142 return false; // not in map.
144 TheBucket->second.~ValueT();
145 TheBucket->first = getTombstoneKey();
150 bool erase(iterator I) {
151 BucketT *TheBucket = &*I;
152 TheBucket->second.~ValueT();
153 TheBucket->first = getTombstoneKey();
159 ValueT &operator[](const KeyT &Key) {
161 if (LookupBucketFor(Key, TheBucket))
162 return TheBucket->second;
164 return InsertIntoBucket(Key, ValueT(), TheBucket)->second;
168 BucketT *InsertIntoBucket(const KeyT &Key, const ValueT &Value,
169 BucketT *TheBucket) {
170 // If the load of the hash table is more than 3/4, or if fewer than 1/8 of
171 // the buckets are empty (meaning that many are filled with tombstones),
174 // The later case is tricky. For example, if we had one empty bucket with
175 // tons of tombstones, failing lookups (e.g. for insertion) would have to
176 // probe almost the entire table until it found the empty bucket. If the
177 // table completely filled with tombstones, no lookup would ever succeed,
178 // causing infinite loops in lookup.
179 if (NumEntries*4 >= NumBuckets*3 ||
180 NumBuckets-(NumEntries+NumTombstones) < NumBuckets/8) {
182 LookupBucketFor(Key, TheBucket);
186 // If we are writing over a tombstone, remember this.
187 if (TheBucket->first != getEmptyKey())
190 TheBucket->first = Key;
191 new (&TheBucket->second) ValueT(Value);
195 static unsigned getHashValue(const KeyT &Val) {
196 return KeyInfoT::getHashValue(Val);
198 static const KeyT getEmptyKey() {
199 return KeyInfoT::getEmptyKey();
201 static const KeyT getTombstoneKey() {
202 return KeyInfoT::getTombstoneKey();
205 /// LookupBucketFor - Lookup the appropriate bucket for Val, returning it in
206 /// FoundBucket. If the bucket contains the key and a value, this returns
207 /// true, otherwise it returns a bucket with an empty marker or tombstone and
209 bool LookupBucketFor(const KeyT &Val, BucketT *&FoundBucket) const {
210 unsigned BucketNo = getHashValue(Val);
211 unsigned ProbeAmt = 1;
212 BucketT *BucketsPtr = Buckets;
214 // FoundTombstone - Keep track of whether we find a tombstone while probing.
215 BucketT *FoundTombstone = 0;
216 const KeyT EmptyKey = getEmptyKey();
217 const KeyT TombstoneKey = getTombstoneKey();
218 assert(Val != EmptyKey && Val != TombstoneKey &&
219 "Empty/Tombstone value shouldn't be inserted into map!");
222 BucketT *ThisBucket = BucketsPtr + (BucketNo & (NumBuckets-1));
223 // Found Val's bucket? If so, return it.
224 if (ThisBucket->first == Val) {
225 FoundBucket = ThisBucket;
229 // If we found an empty bucket, the key doesn't exist in the set.
230 // Insert it and return the default value.
231 if (ThisBucket->first == EmptyKey) {
232 // If we've already seen a tombstone while probing, fill it in instead
233 // of the empty bucket we eventually probed to.
234 if (FoundTombstone) ThisBucket = FoundTombstone;
235 FoundBucket = FoundTombstone ? FoundTombstone : ThisBucket;
239 // If this is a tombstone, remember it. If Val ends up not in the map, we
240 // prefer to return it than something that would require more probing.
241 if (ThisBucket->first == TombstoneKey && !FoundTombstone)
242 FoundTombstone = ThisBucket; // Remember the first tombstone found.
244 // Otherwise, it's a hash collision or a tombstone, continue quadratic
246 BucketNo += ProbeAmt++;
250 void init(unsigned InitBuckets) {
253 NumBuckets = InitBuckets;
254 assert(InitBuckets && (InitBuckets & InitBuckets-1) == 0 &&
255 "# initial buckets must be a power of two!");
256 Buckets = (BucketT*)new char[sizeof(BucketT)*InitBuckets];
257 // Initialize all the keys to EmptyKey.
258 const KeyT EmptyKey = getEmptyKey();
259 for (unsigned i = 0; i != InitBuckets; ++i)
260 new (&Buckets[i].first) KeyT(EmptyKey);
264 unsigned OldNumBuckets = NumBuckets;
265 BucketT *OldBuckets = Buckets;
267 // Double the number of buckets.
270 Buckets = (BucketT*)new char[sizeof(BucketT)*NumBuckets];
272 // Initialize all the keys to EmptyKey.
273 const KeyT EmptyKey = getEmptyKey();
274 for (unsigned i = 0, e = NumBuckets; i != e; ++i)
275 new (&Buckets[i].first) KeyT(EmptyKey);
277 // Insert all the old elements.
278 const KeyT TombstoneKey = getTombstoneKey();
279 for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) {
280 if (B->first != EmptyKey && B->first != TombstoneKey) {
281 // Insert the key/value into the new table.
283 bool FoundVal = LookupBucketFor(B->first, DestBucket);
284 FoundVal = FoundVal; // silence warning.
285 assert(!FoundVal && "Key already in new map?");
286 DestBucket->first = B->first;
287 new (&DestBucket->second) ValueT(B->second);
295 // Free the old table.
296 delete[] (char*)OldBuckets;
299 void shrink_and_clear() {
300 unsigned OldNumBuckets = NumBuckets;
301 BucketT *OldBuckets = Buckets;
303 // Halve the number of buckets.
306 Buckets = (BucketT*)new char[sizeof(BucketT)*NumBuckets];
308 // Initialize all the keys to EmptyKey.
309 const KeyT EmptyKey = getEmptyKey();
310 for (unsigned i = 0, e = NumBuckets; i != e; ++i)
311 new (&Buckets[i].first) KeyT(EmptyKey);
313 // Free the old buckets.
314 const KeyT TombstoneKey = getTombstoneKey();
315 for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) {
316 if (B->first != EmptyKey && B->first != TombstoneKey) {
323 // Free the old table.
324 delete[] (char*)OldBuckets;
330 template<typename KeyT, typename ValueT, typename KeyInfoT>
331 class DenseMapIterator {
332 typedef std::pair<KeyT, ValueT> BucketT;
334 const BucketT *Ptr, *End;
336 DenseMapIterator(const BucketT *Pos, const BucketT *E) : Ptr(Pos), End(E) {
337 AdvancePastEmptyBuckets();
340 std::pair<KeyT, ValueT> &operator*() const {
341 return *const_cast<BucketT*>(Ptr);
343 std::pair<KeyT, ValueT> *operator->() const {
344 return const_cast<BucketT*>(Ptr);
347 bool operator==(const DenseMapIterator &RHS) const {
348 return Ptr == RHS.Ptr;
350 bool operator!=(const DenseMapIterator &RHS) const {
351 return Ptr != RHS.Ptr;
354 inline DenseMapIterator& operator++() { // Preincrement
356 AdvancePastEmptyBuckets();
359 DenseMapIterator operator++(int) { // Postincrement
360 DenseMapIterator tmp = *this; ++*this; return tmp;
364 void AdvancePastEmptyBuckets() {
365 const KeyT Empty = KeyInfoT::getEmptyKey();
366 const KeyT Tombstone = KeyInfoT::getTombstoneKey();
368 while (Ptr != End && (Ptr->first == Empty || Ptr->first == Tombstone))
373 template<typename KeyT, typename ValueT, typename KeyInfoT>
374 class DenseMapConstIterator : public DenseMapIterator<KeyT, ValueT, KeyInfoT> {
376 DenseMapConstIterator(const std::pair<KeyT, ValueT> *Pos,
377 const std::pair<KeyT, ValueT> *E)
378 : DenseMapIterator<KeyT, ValueT, KeyInfoT>(Pos, E) {
380 const std::pair<KeyT, ValueT> &operator*() const {
383 const std::pair<KeyT, ValueT> *operator->() const {
388 } // end namespace llvm