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 typedef size_t size_type;
77 bool LLVM_ATTRIBUTE_UNUSED_RESULT empty() const { return size() == 0; }
78 size_type size() const { return NumElements; }
81 // If the capacity of the array is huge, and the # elements used is small,
83 if (!isSmall() && NumElements*4 < CurArraySize && CurArraySize > 32)
84 return shrink_and_clear();
86 // Fill the array with empty markers.
87 memset(CurArray, -1, CurArraySize*sizeof(void*));
93 static void *getTombstoneMarker() { return reinterpret_cast<void*>(-2); }
94 static void *getEmptyMarker() {
95 // Note that -1 is chosen to make clear() efficiently implementable with
96 // memset and because it's not a valid pointer value.
97 return reinterpret_cast<void*>(-1);
100 /// insert_imp - This returns true if the pointer was new to the set, false if
101 /// it was already in the set. This is hidden from the client so that the
102 /// derived class can check that the right type of pointer is passed in.
103 bool insert_imp(const void * Ptr);
105 /// erase_imp - If the set contains the specified pointer, remove it and
106 /// return true, otherwise return false. This is hidden from the client so
107 /// that the derived class can check that the right type of pointer is passed
109 bool erase_imp(const void * Ptr);
111 bool count_imp(const void * Ptr) const {
113 // Linear search for the item.
114 for (const void *const *APtr = SmallArray,
115 *const *E = SmallArray+NumElements; APtr != E; ++APtr)
122 return *FindBucketFor(Ptr) == Ptr;
126 bool isSmall() const { return CurArray == SmallArray; }
128 const void * const *FindBucketFor(const void *Ptr) const;
129 void shrink_and_clear();
131 /// Grow - Allocate a larger backing store for the buckets and move it over.
132 void Grow(unsigned NewSize);
134 void operator=(const SmallPtrSetImplBase &RHS) LLVM_DELETED_FUNCTION;
136 /// swap - Swaps the elements of two sets.
137 /// Note: This method assumes that both sets have the same small size.
138 void swap(SmallPtrSetImplBase &RHS);
140 void CopyFrom(const SmallPtrSetImplBase &RHS);
141 void MoveFrom(unsigned SmallSize, SmallPtrSetImplBase &&RHS);
144 /// SmallPtrSetIteratorImpl - This is the common base class shared between all
145 /// instances of SmallPtrSetIterator.
146 class SmallPtrSetIteratorImpl {
148 const void *const *Bucket;
149 const void *const *End;
151 explicit SmallPtrSetIteratorImpl(const void *const *BP, const void*const *E)
152 : Bucket(BP), End(E) {
156 bool operator==(const SmallPtrSetIteratorImpl &RHS) const {
157 return Bucket == RHS.Bucket;
159 bool operator!=(const SmallPtrSetIteratorImpl &RHS) const {
160 return Bucket != RHS.Bucket;
164 /// AdvanceIfNotValid - If the current bucket isn't valid, advance to a bucket
165 /// that is. This is guaranteed to stop because the end() bucket is marked
167 void AdvanceIfNotValid() {
168 assert(Bucket <= End);
169 while (Bucket != End &&
170 (*Bucket == SmallPtrSetImplBase::getEmptyMarker() ||
171 *Bucket == SmallPtrSetImplBase::getTombstoneMarker()))
176 /// SmallPtrSetIterator - This implements a const_iterator for SmallPtrSet.
177 template<typename PtrTy>
178 class SmallPtrSetIterator : public SmallPtrSetIteratorImpl {
179 typedef PointerLikeTypeTraits<PtrTy> PtrTraits;
182 typedef PtrTy value_type;
183 typedef PtrTy reference;
184 typedef PtrTy pointer;
185 typedef std::ptrdiff_t difference_type;
186 typedef std::forward_iterator_tag iterator_category;
188 explicit SmallPtrSetIterator(const void *const *BP, const void *const *E)
189 : SmallPtrSetIteratorImpl(BP, E) {}
191 // Most methods provided by baseclass.
193 const PtrTy operator*() const {
194 assert(Bucket < End);
195 return PtrTraits::getFromVoidPointer(const_cast<void*>(*Bucket));
198 inline SmallPtrSetIterator& operator++() { // Preincrement
204 SmallPtrSetIterator operator++(int) { // Postincrement
205 SmallPtrSetIterator tmp = *this; ++*this; return tmp;
209 /// RoundUpToPowerOfTwo - This is a helper template that rounds N up to the next
210 /// power of two (which means N itself if N is already a power of two).
212 struct RoundUpToPowerOfTwo;
214 /// RoundUpToPowerOfTwoH - If N is not a power of two, increase it. This is a
215 /// helper template used to implement RoundUpToPowerOfTwo.
216 template<unsigned N, bool isPowerTwo>
217 struct RoundUpToPowerOfTwoH {
221 struct RoundUpToPowerOfTwoH<N, false> {
223 // We could just use NextVal = N+1, but this converges faster. N|(N-1) sets
224 // the right-most zero bits to one all at once, e.g. 0b0011000 -> 0b0011111.
225 Val = RoundUpToPowerOfTwo<(N|(N-1)) + 1>::Val
230 struct RoundUpToPowerOfTwo {
231 enum { Val = RoundUpToPowerOfTwoH<N, (N&(N-1)) == 0>::Val };
235 /// \brief A templated base class for \c SmallPtrSet which provides the
236 /// typesafe interface that is common across all small sizes.
238 /// This is particularly useful for passing around between interface boundaries
239 /// to avoid encoding a particular small size in the interface boundary.
240 template <typename PtrType>
241 class SmallPtrSetImpl : public SmallPtrSetImplBase {
242 typedef PointerLikeTypeTraits<PtrType> PtrTraits;
244 // Constructors that forward to the base.
245 SmallPtrSetImpl(const void **SmallStorage, const SmallPtrSetImpl &that)
246 : SmallPtrSetImplBase(SmallStorage, that) {}
247 SmallPtrSetImpl(const void **SmallStorage, unsigned SmallSize,
248 SmallPtrSetImpl &&that)
249 : SmallPtrSetImplBase(SmallStorage, SmallSize, std::move(that)) {}
250 explicit SmallPtrSetImpl(const void **SmallStorage, unsigned SmallSize)
251 : SmallPtrSetImplBase(SmallStorage, SmallSize) {}
254 /// insert - This returns true if the pointer was new to the set, false if it
255 /// was already in the set.
256 bool insert(PtrType Ptr) {
257 return insert_imp(PtrTraits::getAsVoidPointer(Ptr));
260 /// erase - If the set contains the specified pointer, remove it and return
261 /// true, otherwise return false.
262 bool erase(PtrType Ptr) {
263 return erase_imp(PtrTraits::getAsVoidPointer(Ptr));
266 /// count - Return 1 if the specified pointer is in the set, 0 otherwise.
267 size_type count(PtrType Ptr) const {
268 return count_imp(PtrTraits::getAsVoidPointer(Ptr)) ? 1 : 0;
271 template <typename IterT>
272 void insert(IterT I, IterT E) {
277 typedef SmallPtrSetIterator<PtrType> iterator;
278 typedef SmallPtrSetIterator<PtrType> const_iterator;
279 inline iterator begin() const {
280 return iterator(CurArray, CurArray+CurArraySize);
282 inline iterator end() const {
283 return iterator(CurArray+CurArraySize, CurArray+CurArraySize);
287 /// SmallPtrSet - This class implements a set which is optimized for holding
288 /// SmallSize or less elements. This internally rounds up SmallSize to the next
289 /// power of two if it is not already a power of two. See the comments above
290 /// SmallPtrSetImplBase for details of the algorithm.
291 template<class PtrType, unsigned SmallSize>
292 class SmallPtrSet : public SmallPtrSetImpl<PtrType> {
293 typedef SmallPtrSetImpl<PtrType> BaseT;
295 // Make sure that SmallSize is a power of two, round up if not.
296 enum { SmallSizePowTwo = RoundUpToPowerOfTwo<SmallSize>::Val };
297 /// SmallStorage - Fixed size storage used in 'small mode'.
298 const void *SmallStorage[SmallSizePowTwo];
300 SmallPtrSet() : BaseT(SmallStorage, SmallSizePowTwo) {}
301 SmallPtrSet(const SmallPtrSet &that) : BaseT(SmallStorage, that) {}
302 SmallPtrSet(SmallPtrSet &&that)
303 : BaseT(SmallStorage, SmallSizePowTwo, std::move(that)) {}
305 template<typename It>
306 SmallPtrSet(It I, It E) : BaseT(SmallStorage, SmallSizePowTwo) {
310 SmallPtrSet<PtrType, SmallSize> &
311 operator=(const SmallPtrSet<PtrType, SmallSize> &RHS) {
317 SmallPtrSet<PtrType, SmallSize>&
318 operator=(SmallPtrSet<PtrType, SmallSize> &&RHS) {
320 this->MoveFrom(SmallSizePowTwo, std::move(RHS));
324 /// swap - Swaps the elements of two sets.
325 void swap(SmallPtrSet<PtrType, SmallSize> &RHS) {
326 SmallPtrSetImplBase::swap(RHS);
333 /// Implement std::swap in terms of SmallPtrSet swap.
334 template<class T, unsigned N>
335 inline void swap(llvm::SmallPtrSet<T, N> &LHS, llvm::SmallPtrSet<T, N> &RHS) {