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 // SmallPtrSetImpl for more details on the algorithm used.
13 //===----------------------------------------------------------------------===//
15 #ifndef LLVM_ADT_SMALLPTRSET_H
16 #define LLVM_ADT_SMALLPTRSET_H
20 #include "llvm/Support/DataTypes.h"
24 /// PointerLikeTypeInfo - This is a traits object that is used to handle pointer
25 /// types and things that are just wrappers for pointers as a uniform entity.
27 class PointerLikeTypeInfo {
28 //getAsVoidPointer/getFromVoidPointer
31 // Provide PointerLikeTypeInfo for all pointers.
33 class PointerLikeTypeInfo<T*> {
35 static inline void *getAsVoidPointer(T* P) { return P; }
36 static inline T *getFromVoidPointer(void *P) {
37 return static_cast<T*>(P);
41 class PointerLikeTypeInfo<const T*> {
43 static inline const void *getAsVoidPointer(const T* P) { return P; }
44 static inline const T *getFromVoidPointer(const void *P) {
45 return static_cast<const T*>(P);
49 class SmallPtrSetIteratorImpl;
51 /// SmallPtrSetImpl - This is the common code shared among all the
52 /// SmallPtrSet<>'s, which is almost everything. SmallPtrSet has two modes, one
53 /// for small and one for large sets.
55 /// Small sets use an array of pointers allocated in the SmallPtrSet object,
56 /// which is treated as a simple array of pointers. When a pointer is added to
57 /// the set, the array is scanned to see if the element already exists, if not
58 /// the element is 'pushed back' onto the array. If we run out of space in the
59 /// array, we grow into the 'large set' case. SmallSet should be used when the
60 /// sets are often small. In this case, no memory allocation is used, and only
61 /// light-weight and cache-efficient scanning is used.
63 /// Large sets use a classic exponentially-probed hash table. Empty buckets are
64 /// represented with an illegal pointer value (-1) to allow null pointers to be
65 /// inserted. Tombstones are represented with another illegal pointer value
66 /// (-2), to allow deletion. The hash table is resized when the table is 3/4 or
67 /// more. When this happens, the table is doubled in size.
69 class SmallPtrSetImpl {
70 friend class SmallPtrSetIteratorImpl;
72 /// CurArray - This is the current set of buckets. If it points to
73 /// SmallArray, then the set is in 'small mode'.
74 const void **CurArray;
75 /// CurArraySize - The allocated size of CurArray, always a power of two.
76 /// Note that CurArray points to an array that has CurArraySize+1 elements in
77 /// it, so that the end iterator actually points to valid memory.
78 unsigned CurArraySize;
80 // If small, this is # elts allocated consequtively
82 unsigned NumTombstones;
83 const void *SmallArray[1]; // Must be last ivar.
85 // Helper to copy construct a SmallPtrSet.
86 SmallPtrSetImpl(const SmallPtrSetImpl& that);
87 explicit SmallPtrSetImpl(unsigned SmallSize) {
88 assert(SmallSize && (SmallSize & (SmallSize-1)) == 0 &&
89 "Initial size must be a power of two!");
90 CurArray = &SmallArray[0];
91 CurArraySize = SmallSize;
92 // The end pointer, always valid, is set to a valid element to help the
94 CurArray[SmallSize] = 0;
100 bool empty() const { return size() == 0; }
101 unsigned size() const { return NumElements; }
104 // If the capacity of the array is huge, and the # elements used is small,
106 if (!isSmall() && NumElements*4 < CurArraySize && CurArraySize > 32)
107 return shrink_and_clear();
109 // Fill the array with empty markers.
110 memset(CurArray, -1, CurArraySize*sizeof(void*));
116 static void *getTombstoneMarker() { return reinterpret_cast<void*>(-2); }
117 static void *getEmptyMarker() {
118 // Note that -1 is chosen to make clear() efficiently implementable with
119 // memset and because it's not a valid pointer value.
120 return reinterpret_cast<void*>(-1);
123 /// insert_imp - This returns true if the pointer was new to the set, false if
124 /// it was already in the set. This is hidden from the client so that the
125 /// derived class can check that the right type of pointer is passed in.
126 bool insert_imp(const void * Ptr);
128 /// erase_imp - If the set contains the specified pointer, remove it and
129 /// return true, otherwise return false. This is hidden from the client so
130 /// that the derived class can check that the right type of pointer is passed
132 bool erase_imp(const void * Ptr);
134 bool count_imp(const void * Ptr) const {
136 // Linear search for the item.
137 for (const void *const *APtr = SmallArray,
138 *const *E = SmallArray+NumElements; APtr != E; ++APtr)
145 return *FindBucketFor(Ptr) == Ptr;
149 bool isSmall() const { return CurArray == &SmallArray[0]; }
151 unsigned Hash(const void *Ptr) const {
152 return static_cast<unsigned>(((uintptr_t)Ptr >> 4) & (CurArraySize-1));
154 const void * const *FindBucketFor(const void *Ptr) const;
155 void shrink_and_clear();
157 /// Grow - Allocate a larger backing store for the buckets and move it over.
160 void operator=(const SmallPtrSetImpl &RHS); // DO NOT IMPLEMENT.
162 void CopyFrom(const SmallPtrSetImpl &RHS);
165 /// SmallPtrSetIteratorImpl - This is the common base class shared between all
166 /// instances of SmallPtrSetIterator.
167 class SmallPtrSetIteratorImpl {
169 const void *const *Bucket;
171 explicit SmallPtrSetIteratorImpl(const void *const *BP) : Bucket(BP) {
175 bool operator==(const SmallPtrSetIteratorImpl &RHS) const {
176 return Bucket == RHS.Bucket;
178 bool operator!=(const SmallPtrSetIteratorImpl &RHS) const {
179 return Bucket != RHS.Bucket;
183 /// AdvanceIfNotValid - If the current bucket isn't valid, advance to a bucket
184 /// that is. This is guaranteed to stop because the end() bucket is marked
186 void AdvanceIfNotValid() {
187 while (*Bucket == SmallPtrSetImpl::getEmptyMarker() ||
188 *Bucket == SmallPtrSetImpl::getTombstoneMarker())
193 /// SmallPtrSetIterator - This implements a const_iterator for SmallPtrSet.
194 template<typename PtrTy>
195 class SmallPtrSetIterator : public SmallPtrSetIteratorImpl {
196 typedef PointerLikeTypeInfo<PtrTy> PtrTraits;
198 explicit SmallPtrSetIterator(const void *const *BP)
199 : SmallPtrSetIteratorImpl(BP) {}
201 // Most methods provided by baseclass.
203 const PtrTy operator*() const {
204 return PtrTraits::getFromVoidPointer(const_cast<void*>(*Bucket));
207 inline SmallPtrSetIterator& operator++() { // Preincrement
213 SmallPtrSetIterator operator++(int) { // Postincrement
214 SmallPtrSetIterator tmp = *this; ++*this; return tmp;
218 /// NextPowerOfTwo - This is a helper template that rounds N up to the next
221 struct NextPowerOfTwo;
223 /// NextPowerOfTwoH - If N is not a power of two, increase it. This is a helper
224 /// template used to implement NextPowerOfTwo.
225 template<unsigned N, bool isPowerTwo>
226 struct NextPowerOfTwoH {
230 struct NextPowerOfTwoH<N, false> {
232 // We could just use NextVal = N+1, but this converges faster. N|(N-1) sets
233 // the right-most zero bits to one all at once, e.g. 0b0011000 -> 0b0011111.
234 Val = NextPowerOfTwo<(N|(N-1)) + 1>::Val
239 struct NextPowerOfTwo {
240 enum { Val = NextPowerOfTwoH<N, (N&(N-1)) == 0>::Val };
244 /// SmallPtrSet - This class implements a set which is optimizer for holding
245 /// SmallSize or less elements. This internally rounds up SmallSize to the next
246 /// power of two if it is not already a power of two. See the comments above
247 /// SmallPtrSetImpl for details of the algorithm.
248 template<class PtrType, unsigned SmallSize>
249 class SmallPtrSet : public SmallPtrSetImpl {
250 // Make sure that SmallSize is a power of two, round up if not.
251 enum { SmallSizePowTwo = NextPowerOfTwo<SmallSize>::Val };
252 void *SmallArray[SmallSizePowTwo];
253 typedef PointerLikeTypeInfo<PtrType> PtrTraits;
255 SmallPtrSet() : SmallPtrSetImpl(NextPowerOfTwo<SmallSizePowTwo>::Val) {}
256 SmallPtrSet(const SmallPtrSet &that) : SmallPtrSetImpl(that) {}
258 template<typename It>
259 SmallPtrSet(It I, It E)
260 : SmallPtrSetImpl(NextPowerOfTwo<SmallSizePowTwo>::Val) {
264 /// insert - This returns true if the pointer was new to the set, false if it
265 /// was already in the set.
266 bool insert(PtrType Ptr) {
267 return insert_imp(PtrTraits::getAsVoidPointer(Ptr));
270 /// erase - If the set contains the specified pointer, remove it and return
271 /// true, otherwise return false.
272 bool erase(PtrType Ptr) {
273 return erase_imp(PtrTraits::getAsVoidPointer(Ptr));
276 /// count - Return true if the specified pointer is in the set.
277 bool count(PtrType Ptr) const {
278 return count_imp(PtrTraits::getAsVoidPointer(Ptr));
281 template <typename IterT>
282 void insert(IterT I, IterT E) {
287 typedef SmallPtrSetIterator<PtrType> iterator;
288 typedef SmallPtrSetIterator<PtrType> const_iterator;
289 inline iterator begin() const {
290 return iterator(CurArray);
292 inline iterator end() const {
293 return iterator(CurArray+CurArraySize);
296 // Allow assignment from any smallptrset with the same element type even if it
297 // doesn't have the same smallsize.
298 const SmallPtrSet<PtrType, SmallSize>&
299 operator=(const SmallPtrSet<PtrType, SmallSize> &RHS) {