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"
29 class SmallPtrSetIteratorImpl;
31 /// SmallPtrSetImplBase - This is the common code shared among all the
32 /// SmallPtrSet<>'s, which is almost everything. SmallPtrSet has two modes, one
33 /// for small and one for large sets.
35 /// Small sets use an array of pointers allocated in the SmallPtrSet object,
36 /// which is treated as a simple array of pointers. When a pointer is added to
37 /// the set, the array is scanned to see if the element already exists, if not
38 /// the element is 'pushed back' onto the array. If we run out of space in the
39 /// array, we grow into the 'large set' case. SmallSet should be used when the
40 /// sets are often small. In this case, no memory allocation is used, and only
41 /// light-weight and cache-efficient scanning is used.
43 /// Large sets use a classic exponentially-probed hash table. Empty buckets are
44 /// represented with an illegal pointer value (-1) to allow null pointers to be
45 /// inserted. Tombstones are represented with another illegal pointer value
46 /// (-2), to allow deletion. The hash table is resized when the table is 3/4 or
47 /// more. When this happens, the table is doubled in size.
49 class SmallPtrSetImplBase {
50 friend class SmallPtrSetIteratorImpl;
52 /// SmallArray - Points to a fixed size set of buckets, used in 'small mode'.
53 const void **SmallArray;
54 /// CurArray - This is the current set of buckets. If equal to SmallArray,
55 /// then the set is in 'small mode'.
56 const void **CurArray;
57 /// CurArraySize - The allocated size of CurArray, always a power of two.
58 unsigned CurArraySize;
60 // If small, this is # elts allocated consecutively
62 unsigned NumTombstones;
64 // Helpers to copy and move construct a SmallPtrSet.
65 SmallPtrSetImplBase(const void **SmallStorage, const SmallPtrSetImplBase &that);
66 SmallPtrSetImplBase(const void **SmallStorage, unsigned SmallSize,
67 SmallPtrSetImplBase &&that);
68 explicit SmallPtrSetImplBase(const void **SmallStorage, unsigned SmallSize) :
69 SmallArray(SmallStorage), CurArray(SmallStorage), CurArraySize(SmallSize) {
70 assert(SmallSize && (SmallSize & (SmallSize-1)) == 0 &&
71 "Initial size must be a power of two!");
74 ~SmallPtrSetImplBase();
77 typedef unsigned size_type;
78 bool LLVM_ATTRIBUTE_UNUSED_RESULT empty() const { return size() == 0; }
79 size_type size() const { return NumElements; }
82 // If the capacity of the array is huge, and the # elements used is small,
84 if (!isSmall() && NumElements*4 < CurArraySize && CurArraySize > 32)
85 return shrink_and_clear();
87 // Fill the array with empty markers.
88 memset(CurArray, -1, CurArraySize*sizeof(void*));
94 static void *getTombstoneMarker() { return reinterpret_cast<void*>(-2); }
95 static void *getEmptyMarker() {
96 // Note that -1 is chosen to make clear() efficiently implementable with
97 // memset and because it's not a valid pointer value.
98 return reinterpret_cast<void*>(-1);
101 /// insert_imp - This returns true if the pointer was new to the set, false if
102 /// it was already in the set. This is hidden from the client so that the
103 /// derived class can check that the right type of pointer is passed in.
104 std::pair<const void *const *, bool> insert_imp(const void *Ptr);
106 /// erase_imp - If the set contains the specified pointer, remove it and
107 /// return true, otherwise return false. This is hidden from the client so
108 /// that the derived class can check that the right type of pointer is passed
110 bool erase_imp(const void * Ptr);
112 bool count_imp(const void * Ptr) const {
114 // Linear search for the item.
115 for (const void *const *APtr = SmallArray,
116 *const *E = SmallArray+NumElements; APtr != E; ++APtr)
123 return *FindBucketFor(Ptr) == Ptr;
127 bool isSmall() const { return CurArray == SmallArray; }
129 const void * const *FindBucketFor(const void *Ptr) const;
130 void shrink_and_clear();
132 /// Grow - Allocate a larger backing store for the buckets and move it over.
133 void Grow(unsigned NewSize);
135 void operator=(const SmallPtrSetImplBase &RHS) = delete;
137 /// swap - Swaps the elements of two sets.
138 /// Note: This method assumes that both sets have the same small size.
139 void swap(SmallPtrSetImplBase &RHS);
141 void CopyFrom(const SmallPtrSetImplBase &RHS);
142 void MoveFrom(unsigned SmallSize, SmallPtrSetImplBase &&RHS);
145 /// SmallPtrSetIteratorImpl - This is the common base class shared between all
146 /// instances of SmallPtrSetIterator.
147 class SmallPtrSetIteratorImpl {
149 const void *const *Bucket;
150 const void *const *End;
152 explicit SmallPtrSetIteratorImpl(const void *const *BP, const void*const *E)
153 : Bucket(BP), End(E) {
157 bool operator==(const SmallPtrSetIteratorImpl &RHS) const {
158 return Bucket == RHS.Bucket;
160 bool operator!=(const SmallPtrSetIteratorImpl &RHS) const {
161 return Bucket != RHS.Bucket;
165 /// AdvanceIfNotValid - If the current bucket isn't valid, advance to a bucket
166 /// that is. This is guaranteed to stop because the end() bucket is marked
168 void AdvanceIfNotValid() {
169 assert(Bucket <= End);
170 while (Bucket != End &&
171 (*Bucket == SmallPtrSetImplBase::getEmptyMarker() ||
172 *Bucket == SmallPtrSetImplBase::getTombstoneMarker()))
177 /// SmallPtrSetIterator - This implements a const_iterator for SmallPtrSet.
178 template<typename PtrTy>
179 class SmallPtrSetIterator : public SmallPtrSetIteratorImpl {
180 typedef PointerLikeTypeTraits<PtrTy> PtrTraits;
183 typedef PtrTy value_type;
184 typedef PtrTy reference;
185 typedef PtrTy pointer;
186 typedef std::ptrdiff_t difference_type;
187 typedef std::forward_iterator_tag iterator_category;
189 explicit SmallPtrSetIterator(const void *const *BP, const void *const *E)
190 : SmallPtrSetIteratorImpl(BP, E) {}
192 // Most methods provided by baseclass.
194 const PtrTy operator*() const {
195 assert(Bucket < End);
196 return PtrTraits::getFromVoidPointer(const_cast<void*>(*Bucket));
199 inline SmallPtrSetIterator& operator++() { // Preincrement
205 SmallPtrSetIterator operator++(int) { // Postincrement
206 SmallPtrSetIterator tmp = *this; ++*this; return tmp;
210 /// RoundUpToPowerOfTwo - This is a helper template that rounds N up to the next
211 /// power of two (which means N itself if N is already a power of two).
213 struct RoundUpToPowerOfTwo;
215 /// RoundUpToPowerOfTwoH - If N is not a power of two, increase it. This is a
216 /// helper template used to implement RoundUpToPowerOfTwo.
217 template<unsigned N, bool isPowerTwo>
218 struct RoundUpToPowerOfTwoH {
222 struct RoundUpToPowerOfTwoH<N, false> {
224 // We could just use NextVal = N+1, but this converges faster. N|(N-1) sets
225 // the right-most zero bits to one all at once, e.g. 0b0011000 -> 0b0011111.
226 Val = RoundUpToPowerOfTwo<(N|(N-1)) + 1>::Val
231 struct RoundUpToPowerOfTwo {
232 enum { Val = RoundUpToPowerOfTwoH<N, (N&(N-1)) == 0>::Val };
236 /// \brief A templated base class for \c SmallPtrSet which provides the
237 /// typesafe interface that is common across all small sizes.
239 /// This is particularly useful for passing around between interface boundaries
240 /// to avoid encoding a particular small size in the interface boundary.
241 template <typename PtrType>
242 class SmallPtrSetImpl : public SmallPtrSetImplBase {
243 typedef PointerLikeTypeTraits<PtrType> PtrTraits;
245 SmallPtrSetImpl(const SmallPtrSetImpl&) = delete;
247 // Constructors that forward to the base.
248 SmallPtrSetImpl(const void **SmallStorage, const SmallPtrSetImpl &that)
249 : SmallPtrSetImplBase(SmallStorage, that) {}
250 SmallPtrSetImpl(const void **SmallStorage, unsigned SmallSize,
251 SmallPtrSetImpl &&that)
252 : SmallPtrSetImplBase(SmallStorage, SmallSize, std::move(that)) {}
253 explicit SmallPtrSetImpl(const void **SmallStorage, unsigned SmallSize)
254 : SmallPtrSetImplBase(SmallStorage, SmallSize) {}
257 typedef SmallPtrSetIterator<PtrType> iterator;
258 typedef SmallPtrSetIterator<PtrType> const_iterator;
260 /// Inserts Ptr if and only if there is no element in the container equal to
261 /// Ptr. The bool component of the returned pair is true if and only if the
262 /// insertion takes place, and the iterator component of the pair points to
263 /// the element equal to Ptr.
264 std::pair<iterator, bool> insert(PtrType Ptr) {
265 auto p = insert_imp(PtrTraits::getAsVoidPointer(Ptr));
266 return std::make_pair(iterator(p.first, CurArray + CurArraySize), p.second);
269 /// erase - If the set contains the specified pointer, remove it and return
270 /// true, otherwise return false.
271 bool erase(PtrType Ptr) {
272 return erase_imp(PtrTraits::getAsVoidPointer(Ptr));
275 /// count - Return 1 if the specified pointer is in the set, 0 otherwise.
276 size_type count(PtrType Ptr) const {
277 return count_imp(PtrTraits::getAsVoidPointer(Ptr)) ? 1 : 0;
280 template <typename IterT>
281 void insert(IterT I, IterT E) {
286 inline iterator begin() const {
287 return iterator(CurArray, CurArray+CurArraySize);
289 inline iterator end() const {
290 return iterator(CurArray+CurArraySize, CurArray+CurArraySize);
294 /// SmallPtrSet - This class implements a set which is optimized for holding
295 /// SmallSize or less elements. This internally rounds up SmallSize to the next
296 /// power of two if it is not already a power of two. See the comments above
297 /// SmallPtrSetImplBase for details of the algorithm.
298 template<class PtrType, unsigned SmallSize>
299 class SmallPtrSet : public SmallPtrSetImpl<PtrType> {
300 typedef SmallPtrSetImpl<PtrType> BaseT;
302 // Make sure that SmallSize is a power of two, round up if not.
303 enum { SmallSizePowTwo = RoundUpToPowerOfTwo<SmallSize>::Val };
304 /// SmallStorage - Fixed size storage used in 'small mode'.
305 const void *SmallStorage[SmallSizePowTwo];
307 SmallPtrSet() : BaseT(SmallStorage, SmallSizePowTwo) {}
308 SmallPtrSet(const SmallPtrSet &that) : BaseT(SmallStorage, that) {}
309 SmallPtrSet(SmallPtrSet &&that)
310 : BaseT(SmallStorage, SmallSizePowTwo, std::move(that)) {}
312 template<typename It>
313 SmallPtrSet(It I, It E) : BaseT(SmallStorage, SmallSizePowTwo) {
317 SmallPtrSet<PtrType, SmallSize> &
318 operator=(const SmallPtrSet<PtrType, SmallSize> &RHS) {
324 SmallPtrSet<PtrType, SmallSize>&
325 operator=(SmallPtrSet<PtrType, SmallSize> &&RHS) {
327 this->MoveFrom(SmallSizePowTwo, std::move(RHS));
331 /// swap - Swaps the elements of two sets.
332 void swap(SmallPtrSet<PtrType, SmallSize> &RHS) {
333 SmallPtrSetImplBase::swap(RHS);
340 /// Implement std::swap in terms of SmallPtrSet swap.
341 template<class T, unsigned N>
342 inline void swap(llvm::SmallPtrSet<T, N> &LHS, llvm::SmallPtrSet<T, N> &RHS) {