1 //===- llvm/ADT/SmallPtrSet.h - 'Normally small' pointer set ----*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the SmallPtrSet class. See the doxygen comment for
11 // SmallPtrSetImplBase for more details on the algorithm used.
13 //===----------------------------------------------------------------------===//
15 #ifndef LLVM_ADT_SMALLPTRSET_H
16 #define LLVM_ADT_SMALLPTRSET_H
18 #include "llvm/Support/Compiler.h"
19 #include "llvm/Support/DataTypes.h"
20 #include "llvm/Support/PointerLikeTypeTraits.h"
28 class SmallPtrSetIteratorImpl;
30 /// SmallPtrSetImplBase - This is the common code shared among all the
31 /// SmallPtrSet<>'s, which is almost everything. SmallPtrSet has two modes, one
32 /// for small and one for large sets.
34 /// Small sets use an array of pointers allocated in the SmallPtrSet object,
35 /// which is treated as a simple array of pointers. When a pointer is added to
36 /// the set, the array is scanned to see if the element already exists, if not
37 /// the element is 'pushed back' onto the array. If we run out of space in the
38 /// array, we grow into the 'large set' case. SmallSet should be used when the
39 /// sets are often small. In this case, no memory allocation is used, and only
40 /// light-weight and cache-efficient scanning is used.
42 /// Large sets use a classic exponentially-probed hash table. Empty buckets are
43 /// represented with an illegal pointer value (-1) to allow null pointers to be
44 /// inserted. Tombstones are represented with another illegal pointer value
45 /// (-2), to allow deletion. The hash table is resized when the table is 3/4 or
46 /// more. When this happens, the table is doubled in size.
48 class SmallPtrSetImplBase {
49 friend class SmallPtrSetIteratorImpl;
51 /// SmallArray - Points to a fixed size set of buckets, used in 'small mode'.
52 const void **SmallArray;
53 /// CurArray - This is the current set of buckets. If equal to SmallArray,
54 /// then the set is in 'small mode'.
55 const void **CurArray;
56 /// CurArraySize - The allocated size of CurArray, always a power of two.
57 unsigned CurArraySize;
59 // If small, this is # elts allocated consecutively
61 unsigned NumTombstones;
63 // Helpers to copy and move construct a SmallPtrSet.
64 SmallPtrSetImplBase(const void **SmallStorage, const SmallPtrSetImplBase &that);
65 SmallPtrSetImplBase(const void **SmallStorage, unsigned SmallSize,
66 SmallPtrSetImplBase &&that);
67 explicit SmallPtrSetImplBase(const void **SmallStorage, unsigned SmallSize) :
68 SmallArray(SmallStorage), CurArray(SmallStorage), CurArraySize(SmallSize) {
69 assert(SmallSize && (SmallSize & (SmallSize-1)) == 0 &&
70 "Initial size must be a power of two!");
73 ~SmallPtrSetImplBase();
76 bool LLVM_ATTRIBUTE_UNUSED_RESULT empty() const { return size() == 0; }
77 unsigned size() const { return NumElements; }
80 // If the capacity of the array is huge, and the # elements used is small,
82 if (!isSmall() && NumElements*4 < CurArraySize && CurArraySize > 32)
83 return shrink_and_clear();
85 // Fill the array with empty markers.
86 memset(CurArray, -1, CurArraySize*sizeof(void*));
92 static void *getTombstoneMarker() { return reinterpret_cast<void*>(-2); }
93 static void *getEmptyMarker() {
94 // Note that -1 is chosen to make clear() efficiently implementable with
95 // memset and because it's not a valid pointer value.
96 return reinterpret_cast<void*>(-1);
99 /// insert_imp - This returns true if the pointer was new to the set, false if
100 /// it was already in the set. This is hidden from the client so that the
101 /// derived class can check that the right type of pointer is passed in.
102 bool insert_imp(const void * Ptr);
104 /// erase_imp - If the set contains the specified pointer, remove it and
105 /// return true, otherwise return false. This is hidden from the client so
106 /// that the derived class can check that the right type of pointer is passed
108 bool erase_imp(const void * Ptr);
110 bool count_imp(const void * Ptr) const {
112 // Linear search for the item.
113 for (const void *const *APtr = SmallArray,
114 *const *E = SmallArray+NumElements; APtr != E; ++APtr)
121 return *FindBucketFor(Ptr) == Ptr;
125 bool isSmall() const { return CurArray == SmallArray; }
127 const void * const *FindBucketFor(const void *Ptr) const;
128 void shrink_and_clear();
130 /// Grow - Allocate a larger backing store for the buckets and move it over.
131 void Grow(unsigned NewSize);
133 void operator=(const SmallPtrSetImplBase &RHS) LLVM_DELETED_FUNCTION;
135 /// swap - Swaps the elements of two sets.
136 /// Note: This method assumes that both sets have the same small size.
137 void swap(SmallPtrSetImplBase &RHS);
139 void CopyFrom(const SmallPtrSetImplBase &RHS);
140 void MoveFrom(unsigned SmallSize, SmallPtrSetImplBase &&RHS);
143 /// SmallPtrSetIteratorImpl - This is the common base class shared between all
144 /// instances of SmallPtrSetIterator.
145 class SmallPtrSetIteratorImpl {
147 const void *const *Bucket;
148 const void *const *End;
150 explicit SmallPtrSetIteratorImpl(const void *const *BP, const void*const *E)
151 : Bucket(BP), End(E) {
155 bool operator==(const SmallPtrSetIteratorImpl &RHS) const {
156 return Bucket == RHS.Bucket;
158 bool operator!=(const SmallPtrSetIteratorImpl &RHS) const {
159 return Bucket != RHS.Bucket;
163 /// AdvanceIfNotValid - If the current bucket isn't valid, advance to a bucket
164 /// that is. This is guaranteed to stop because the end() bucket is marked
166 void AdvanceIfNotValid() {
167 assert(Bucket <= End);
168 while (Bucket != End &&
169 (*Bucket == SmallPtrSetImplBase::getEmptyMarker() ||
170 *Bucket == SmallPtrSetImplBase::getTombstoneMarker()))
175 /// SmallPtrSetIterator - This implements a const_iterator for SmallPtrSet.
176 template<typename PtrTy>
177 class SmallPtrSetIterator : public SmallPtrSetIteratorImpl {
178 typedef PointerLikeTypeTraits<PtrTy> PtrTraits;
181 typedef PtrTy value_type;
182 typedef PtrTy reference;
183 typedef PtrTy pointer;
184 typedef std::ptrdiff_t difference_type;
185 typedef std::forward_iterator_tag iterator_category;
187 explicit SmallPtrSetIterator(const void *const *BP, const void *const *E)
188 : SmallPtrSetIteratorImpl(BP, E) {}
190 // Most methods provided by baseclass.
192 const PtrTy operator*() const {
193 assert(Bucket < End);
194 return PtrTraits::getFromVoidPointer(const_cast<void*>(*Bucket));
197 inline SmallPtrSetIterator& operator++() { // Preincrement
203 SmallPtrSetIterator operator++(int) { // Postincrement
204 SmallPtrSetIterator tmp = *this; ++*this; return tmp;
208 /// RoundUpToPowerOfTwo - This is a helper template that rounds N up to the next
209 /// power of two (which means N itself if N is already a power of two).
211 struct RoundUpToPowerOfTwo;
213 /// RoundUpToPowerOfTwoH - If N is not a power of two, increase it. This is a
214 /// helper template used to implement RoundUpToPowerOfTwo.
215 template<unsigned N, bool isPowerTwo>
216 struct RoundUpToPowerOfTwoH {
220 struct RoundUpToPowerOfTwoH<N, false> {
222 // We could just use NextVal = N+1, but this converges faster. N|(N-1) sets
223 // the right-most zero bits to one all at once, e.g. 0b0011000 -> 0b0011111.
224 Val = RoundUpToPowerOfTwo<(N|(N-1)) + 1>::Val
229 struct RoundUpToPowerOfTwo {
230 enum { Val = RoundUpToPowerOfTwoH<N, (N&(N-1)) == 0>::Val };
234 /// \brief A templated base class for \c SmallPtrSet which provides the
235 /// typesafe interface that is common across all small sizes.
237 /// This is particularly useful for passing around between interface boundaries
238 /// to avoid encoding a particular small size in the interface boundary.
239 template <typename PtrType>
240 class SmallPtrSetImpl : public SmallPtrSetImplBase {
241 typedef PointerLikeTypeTraits<PtrType> PtrTraits;
243 // Constructors that forward to the base.
244 SmallPtrSetImpl(const void **SmallStorage, const SmallPtrSetImpl &that)
245 : SmallPtrSetImplBase(SmallStorage, that) {}
246 SmallPtrSetImpl(const void **SmallStorage, unsigned SmallSize,
247 SmallPtrSetImpl &&that)
248 : SmallPtrSetImplBase(SmallStorage, SmallSize, std::move(that)) {}
249 explicit SmallPtrSetImpl(const void **SmallStorage, unsigned SmallSize)
250 : SmallPtrSetImplBase(SmallStorage, SmallSize) {}
253 /// insert - This returns true if the pointer was new to the set, false if it
254 /// was already in the set.
255 bool insert(PtrType Ptr) {
256 return insert_imp(PtrTraits::getAsVoidPointer(Ptr));
259 /// erase - If the set contains the specified pointer, remove it and return
260 /// true, otherwise return false.
261 bool erase(PtrType Ptr) {
262 return erase_imp(PtrTraits::getAsVoidPointer(Ptr));
265 /// count - Return 1 if the specified pointer is in the set, 0 otherwise.
266 unsigned count(PtrType Ptr) const {
267 return count_imp(PtrTraits::getAsVoidPointer(Ptr)) ? 1 : 0;
270 template <typename IterT>
271 void insert(IterT I, IterT E) {
276 typedef SmallPtrSetIterator<PtrType> iterator;
277 typedef SmallPtrSetIterator<PtrType> const_iterator;
278 inline iterator begin() const {
279 return iterator(CurArray, CurArray+CurArraySize);
281 inline iterator end() const {
282 return iterator(CurArray+CurArraySize, CurArray+CurArraySize);
286 /// SmallPtrSet - This class implements a set which is optimized for holding
287 /// SmallSize or less elements. This internally rounds up SmallSize to the next
288 /// power of two if it is not already a power of two. See the comments above
289 /// SmallPtrSetImplBase for details of the algorithm.
290 template<class PtrType, unsigned SmallSize>
291 class SmallPtrSet : public SmallPtrSetImpl<PtrType> {
292 typedef SmallPtrSetImpl<PtrType> BaseT;
294 // Make sure that SmallSize is a power of two, round up if not.
295 enum { SmallSizePowTwo = RoundUpToPowerOfTwo<SmallSize>::Val };
296 /// SmallStorage - Fixed size storage used in 'small mode'.
297 const void *SmallStorage[SmallSizePowTwo];
299 SmallPtrSet() : BaseT(SmallStorage, SmallSizePowTwo) {}
300 SmallPtrSet(const SmallPtrSet &that) : BaseT(SmallStorage, that) {}
301 SmallPtrSet(SmallPtrSet &&that)
302 : BaseT(SmallStorage, SmallSizePowTwo, std::move(that)) {}
304 template<typename It>
305 SmallPtrSet(It I, It E) : BaseT(SmallStorage, SmallSizePowTwo) {
309 SmallPtrSet<PtrType, SmallSize> &
310 operator=(const SmallPtrSet<PtrType, SmallSize> &RHS) {
316 SmallPtrSet<PtrType, SmallSize>&
317 operator=(SmallPtrSet<PtrType, SmallSize> &&RHS) {
319 this->MoveFrom(SmallSizePowTwo, std::move(RHS));
323 /// swap - Swaps the elements of two sets.
324 void swap(SmallPtrSet<PtrType, SmallSize> &RHS) {
325 SmallPtrSetImplBase::swap(RHS);
332 /// Implement std::swap in terms of SmallPtrSet swap.
333 template<class T, unsigned N>
334 inline void swap(llvm::SmallPtrSet<T, N> &LHS, llvm::SmallPtrSet<T, N> &RHS) {