1//===- llvm/ADT/SmallPtrSet.h - 'Normally small' pointer set ----*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file defines the SmallPtrSet class. See the doxygen comment for 11// SmallPtrSetImplBase for more details on the algorithm used. 12// 13//===----------------------------------------------------------------------===// 14 15#ifndef LLVM_ADT_SMALLPTRSET_H 16#define LLVM_ADT_SMALLPTRSET_H 17 18#include "llvm/Support/Compiler.h" 19#include "llvm/Support/DataTypes.h" 20#include "llvm/Support/PointerLikeTypeTraits.h" 21#include <cassert> 22#include <cstddef> 23#include <cstring> 24#include <iterator> 25 26namespace llvm { 27 28class SmallPtrSetIteratorImpl; 29 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. 33/// 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. 41/// 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. 47/// 48class SmallPtrSetImplBase { 49 friend class SmallPtrSetIteratorImpl; 50protected: 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; 58 59 // If small, this is # elts allocated consecutively 60 unsigned NumElements; 61 unsigned NumTombstones; 62 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!"); 71 clear(); 72 } 73 ~SmallPtrSetImplBase(); 74 75public: 76 typedef unsigned size_type; 77 bool LLVM_ATTRIBUTE_UNUSED_RESULT empty() const { return size() == 0; } 78 size_type size() const { return NumElements; } 79 80 void clear() { 81 // If the capacity of the array is huge, and the # elements used is small, 82 // shrink the array. 83 if (!isSmall() && NumElements*4 < CurArraySize && CurArraySize > 32) 84 return shrink_and_clear(); 85 86 // Fill the array with empty markers. 87 memset(CurArray, -1, CurArraySize*sizeof(void*)); 88 NumElements = 0; 89 NumTombstones = 0; 90 } 91 92protected: 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); 98 } 99 100 /// 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); 104 105 /// 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 108 /// in. 109 bool erase_imp(const void * Ptr); 110 111 bool count_imp(const void * Ptr) const { 112 if (isSmall()) { 113 // Linear search for the item. 114 for (const void *const *APtr = SmallArray, 115 *const *E = SmallArray+NumElements; APtr != E; ++APtr) 116 if (*APtr == Ptr) 117 return true; 118 return false; 119 } 120 121 // Big set case. 122 return *FindBucketFor(Ptr) == Ptr; 123 } 124 125private: 126 bool isSmall() const { return CurArray == SmallArray; } 127 128 const void * const *FindBucketFor(const void *Ptr) const; 129 void shrink_and_clear(); 130 131 /// Grow - Allocate a larger backing store for the buckets and move it over. 132 void Grow(unsigned NewSize); 133 134 void operator=(const SmallPtrSetImplBase &RHS) LLVM_DELETED_FUNCTION; 135protected: 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); 139 140 void CopyFrom(const SmallPtrSetImplBase &RHS); 141 void MoveFrom(unsigned SmallSize, SmallPtrSetImplBase &&RHS); 142}; 143 144/// SmallPtrSetIteratorImpl - This is the common base class shared between all 145/// instances of SmallPtrSetIterator. 146class SmallPtrSetIteratorImpl { 147protected: 148 const void *const *Bucket; 149 const void *const *End; 150public: 151 explicit SmallPtrSetIteratorImpl(const void *const *BP, const void*const *E) 152 : Bucket(BP), End(E) { 153 AdvanceIfNotValid(); 154 } 155 156 bool operator==(const SmallPtrSetIteratorImpl &RHS) const { 157 return Bucket == RHS.Bucket; 158 } 159 bool operator!=(const SmallPtrSetIteratorImpl &RHS) const { 160 return Bucket != RHS.Bucket; 161 } 162 163protected: 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 166 /// valid. 167 void AdvanceIfNotValid() { 168 assert(Bucket <= End); 169 while (Bucket != End && 170 (*Bucket == SmallPtrSetImplBase::getEmptyMarker() || 171 *Bucket == SmallPtrSetImplBase::getTombstoneMarker())) 172 ++Bucket; 173 } 174}; 175 176/// SmallPtrSetIterator - This implements a const_iterator for SmallPtrSet. 177template<typename PtrTy> 178class SmallPtrSetIterator : public SmallPtrSetIteratorImpl { 179 typedef PointerLikeTypeTraits<PtrTy> PtrTraits; 180 181public: 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; 187 188 explicit SmallPtrSetIterator(const void *const *BP, const void *const *E) 189 : SmallPtrSetIteratorImpl(BP, E) {} 190 191 // Most methods provided by baseclass. 192 193 const PtrTy operator*() const { 194 assert(Bucket < End); 195 return PtrTraits::getFromVoidPointer(const_cast<void*>(*Bucket)); 196 } 197 198 inline SmallPtrSetIterator& operator++() { // Preincrement 199 ++Bucket; 200 AdvanceIfNotValid(); 201 return *this; 202 } 203 204 SmallPtrSetIterator operator++(int) { // Postincrement 205 SmallPtrSetIterator tmp = *this; ++*this; return tmp; 206 } 207}; 208 209/// 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). 211template<unsigned N> 212struct RoundUpToPowerOfTwo; 213 214/// RoundUpToPowerOfTwoH - If N is not a power of two, increase it. This is a 215/// helper template used to implement RoundUpToPowerOfTwo. 216template<unsigned N, bool isPowerTwo> 217struct RoundUpToPowerOfTwoH { 218 enum { Val = N }; 219}; 220template<unsigned N> 221struct RoundUpToPowerOfTwoH<N, false> { 222 enum { 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 226 }; 227}; 228 229template<unsigned N> 230struct RoundUpToPowerOfTwo { 231 enum { Val = RoundUpToPowerOfTwoH<N, (N&(N-1)) == 0>::Val }; 232}; 233 234 235/// \brief A templated base class for \c SmallPtrSet which provides the 236/// typesafe interface that is common across all small sizes. 237/// 238/// This is particularly useful for passing around between interface boundaries 239/// to avoid encoding a particular small size in the interface boundary. 240template <typename PtrType> 241class SmallPtrSetImpl : public SmallPtrSetImplBase { 242 typedef PointerLikeTypeTraits<PtrType> PtrTraits; 243protected: 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) {} 252 253public: 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)); 258 } 259 260 /// 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)); 264 } 265 266 /// 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; 269 } 270 271 template <typename IterT> 272 void insert(IterT I, IterT E) { 273 for (; I != E; ++I) 274 insert(*I); 275 } 276 277 typedef SmallPtrSetIterator<PtrType> iterator; 278 typedef SmallPtrSetIterator<PtrType> const_iterator; 279 inline iterator begin() const { 280 return iterator(CurArray, CurArray+CurArraySize); 281 } 282 inline iterator end() const { 283 return iterator(CurArray+CurArraySize, CurArray+CurArraySize); 284 } 285}; 286 287/// 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. 291template<class PtrType, unsigned SmallSize> 292class SmallPtrSet : public SmallPtrSetImpl<PtrType> { 293 typedef SmallPtrSetImpl<PtrType> BaseT; 294 295 // 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]; 299public: 300 SmallPtrSet() : BaseT(SmallStorage, SmallSizePowTwo) {} 301 SmallPtrSet(const SmallPtrSet &that) : BaseT(SmallStorage, that) {} 302 SmallPtrSet(SmallPtrSet &&that) 303 : BaseT(SmallStorage, SmallSizePowTwo, std::move(that)) {} 304 305 template<typename It> 306 SmallPtrSet(It I, It E) : BaseT(SmallStorage, SmallSizePowTwo) { 307 this->insert(I, E); 308 } 309 310 SmallPtrSet<PtrType, SmallSize> & 311 operator=(const SmallPtrSet<PtrType, SmallSize> &RHS) { 312 if (&RHS != this) 313 this->CopyFrom(RHS); 314 return *this; 315 } 316 317 SmallPtrSet<PtrType, SmallSize>& 318 operator=(SmallPtrSet<PtrType, SmallSize> &&RHS) { 319 if (&RHS != this) 320 this->MoveFrom(SmallSizePowTwo, std::move(RHS)); 321 return *this; 322 } 323 324 /// swap - Swaps the elements of two sets. 325 void swap(SmallPtrSet<PtrType, SmallSize> &RHS) { 326 SmallPtrSetImplBase::swap(RHS); 327 } 328}; 329 330} 331 332namespace std { 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) { 336 LHS.swap(RHS); 337 } 338} 339 340#endif 341