LLVM  3.7.0
SmallPtrSet.h
Go to the documentation of this file.
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"
21 #include <cassert>
22 #include <cstddef>
23 #include <cstring>
24 #include <iterator>
25 #include <utility>
26 
27 namespace llvm {
28 
29 class SmallPtrSetIteratorImpl;
30 
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.
34 ///
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.
42 ///
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.
48 ///
51 protected:
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;
59 
60  // If small, this is # elts allocated consecutively
61  unsigned NumElements;
62  unsigned NumTombstones;
63 
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!");
72  clear();
73  }
75 
76 public:
77  typedef unsigned size_type;
78  bool LLVM_ATTRIBUTE_UNUSED_RESULT empty() const { return size() == 0; }
79  size_type size() const { return NumElements; }
80 
81  void clear() {
82  // If the capacity of the array is huge, and the # elements used is small,
83  // shrink the array.
84  if (!isSmall() && NumElements*4 < CurArraySize && CurArraySize > 32)
85  return shrink_and_clear();
86 
87  // Fill the array with empty markers.
88  memset(CurArray, -1, CurArraySize*sizeof(void*));
89  NumElements = 0;
90  NumTombstones = 0;
91  }
92 
93 protected:
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);
99  }
100 
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);
105 
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
109  /// in.
110  bool erase_imp(const void * Ptr);
111 
112  bool count_imp(const void * Ptr) const {
113  if (isSmall()) {
114  // Linear search for the item.
115  for (const void *const *APtr = SmallArray,
116  *const *E = SmallArray+NumElements; APtr != E; ++APtr)
117  if (*APtr == Ptr)
118  return true;
119  return false;
120  }
121 
122  // Big set case.
123  return *FindBucketFor(Ptr) == Ptr;
124  }
125 
126 private:
127  bool isSmall() const { return CurArray == SmallArray; }
128 
129  const void * const *FindBucketFor(const void *Ptr) const;
130  void shrink_and_clear();
131 
132  /// Grow - Allocate a larger backing store for the buckets and move it over.
133  void Grow(unsigned NewSize);
134 
135  void operator=(const SmallPtrSetImplBase &RHS) = delete;
136 protected:
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);
140 
141  void CopyFrom(const SmallPtrSetImplBase &RHS);
142  void MoveFrom(unsigned SmallSize, SmallPtrSetImplBase &&RHS);
143 };
144 
145 /// SmallPtrSetIteratorImpl - This is the common base class shared between all
146 /// instances of SmallPtrSetIterator.
148 protected:
149  const void *const *Bucket;
150  const void *const *End;
151 public:
152  explicit SmallPtrSetIteratorImpl(const void *const *BP, const void*const *E)
153  : Bucket(BP), End(E) {
155  }
156 
157  bool operator==(const SmallPtrSetIteratorImpl &RHS) const {
158  return Bucket == RHS.Bucket;
159  }
160  bool operator!=(const SmallPtrSetIteratorImpl &RHS) const {
161  return Bucket != RHS.Bucket;
162  }
163 
164 protected:
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
167  /// valid.
169  assert(Bucket <= End);
170  while (Bucket != End &&
173  ++Bucket;
174  }
175 };
176 
177 /// SmallPtrSetIterator - This implements a const_iterator for SmallPtrSet.
178 template<typename PtrTy>
181 
182 public:
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;
188 
189  explicit SmallPtrSetIterator(const void *const *BP, const void *const *E)
190  : SmallPtrSetIteratorImpl(BP, E) {}
191 
192  // Most methods provided by baseclass.
193 
194  const PtrTy operator*() const {
195  assert(Bucket < End);
196  return PtrTraits::getFromVoidPointer(const_cast<void*>(*Bucket));
197  }
198 
199  inline SmallPtrSetIterator& operator++() { // Preincrement
200  ++Bucket;
202  return *this;
203  }
204 
205  SmallPtrSetIterator operator++(int) { // Postincrement
206  SmallPtrSetIterator tmp = *this; ++*this; return tmp;
207  }
208 };
209 
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).
212 template<unsigned N>
214 
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>
219  enum { Val = N };
220 };
221 template<unsigned N>
223  enum {
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.
227  };
228 };
229 
230 template<unsigned N>
231 struct RoundUpToPowerOfTwo {
232  enum { Val = RoundUpToPowerOfTwoH<N, (N&(N-1)) == 0>::Val };
233 };
234 
235 
236 /// \brief A templated base class for \c SmallPtrSet which provides the
237 /// typesafe interface that is common across all small sizes.
238 ///
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>
244 
245  SmallPtrSetImpl(const SmallPtrSetImpl&) = delete;
246 protected:
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) {}
255 
256 public:
259 
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);
267  }
268 
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));
273  }
274 
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;
278  }
279 
280  template <typename IterT>
281  void insert(IterT I, IterT E) {
282  for (; I != E; ++I)
283  insert(*I);
284  }
285 
286  inline iterator begin() const {
288  }
289  inline iterator end() const {
291  }
292 };
293 
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> {
301 
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];
306 public:
307  SmallPtrSet() : BaseT(SmallStorage, SmallSizePowTwo) {}
308  SmallPtrSet(const SmallPtrSet &that) : BaseT(SmallStorage, that) {}
310  : BaseT(SmallStorage, SmallSizePowTwo, std::move(that)) {}
311 
312  template<typename It>
313  SmallPtrSet(It I, It E) : BaseT(SmallStorage, SmallSizePowTwo) {
314  this->insert(I, E);
315  }
316 
319  if (&RHS != this)
320  this->CopyFrom(RHS);
321  return *this;
322  }
323 
326  if (&RHS != this)
327  this->MoveFrom(SmallSizePowTwo, std::move(RHS));
328  return *this;
329  }
330 
331  /// swap - Swaps the elements of two sets.
334  }
335 };
336 
337 }
338 
339 namespace std {
340  /// Implement std::swap in terms of SmallPtrSet swap.
341  template<class T, unsigned N>
343  LHS.swap(RHS);
344  }
345 }
346 
347 #endif
static void * getTombstoneMarker()
Definition: SmallPtrSet.h:94
SmallPtrSetImpl(const void **SmallStorage, unsigned SmallSize, SmallPtrSetImpl &&that)
Definition: SmallPtrSet.h:250
bool count_imp(const void *Ptr) const
Definition: SmallPtrSet.h:112
#define LLVM_ATTRIBUTE_UNUSED_RESULT
Definition: Compiler.h:128
bool LLVM_ATTRIBUTE_UNUSED_RESULT empty() const
Definition: SmallPtrSet.h:78
SmallPtrSet(const SmallPtrSet &that)
Definition: SmallPtrSet.h:308
SmallPtrSet(It I, It E)
Definition: SmallPtrSet.h:313
SmallPtrSetImpl(const void **SmallStorage, const SmallPtrSetImpl &that)
Definition: SmallPtrSet.h:248
SmallPtrSetIterator< PtrType > const_iterator
Definition: SmallPtrSet.h:258
std::ptrdiff_t difference_type
Definition: SmallPtrSet.h:186
size_type count(PtrType Ptr) const
count - Return 1 if the specified pointer is in the set, 0 otherwise.
Definition: SmallPtrSet.h:276
void MoveFrom(unsigned SmallSize, SmallPtrSetImplBase &&RHS)
PointerLikeTypeTraits - This is a traits object that is used to handle pointer types and things that ...
A templated base class for SmallPtrSet which provides the typesafe interface that is common across al...
Definition: SmallPtrSet.h:242
SmallPtrSetIterator & operator++()
Definition: SmallPtrSet.h:199
SmallPtrSetIteratorImpl - This is the common base class shared between all instances of SmallPtrSetIt...
Definition: SmallPtrSet.h:147
void swap(SmallPtrSetImplBase &RHS)
swap - Swaps the elements of two sets.
SmallPtrSet(SmallPtrSet &&that)
Definition: SmallPtrSet.h:309
unsigned CurArraySize
CurArraySize - The allocated size of CurArray, always a power of two.
Definition: SmallPtrSet.h:58
SmallPtrSetIterator(const void *const *BP, const void *const *E)
Definition: SmallPtrSet.h:189
const void ** CurArray
CurArray - This is the current set of buckets.
Definition: SmallPtrSet.h:56
#define false
Definition: ConvertUTF.c:65
RoundUpToPowerOfTwo - This is a helper template that rounds N up to the next power of two (which mean...
Definition: SmallPtrSet.h:213
bool operator!=(const SmallPtrSetIteratorImpl &RHS) const
Definition: SmallPtrSet.h:160
SmallPtrSet< PtrType, SmallSize > & operator=(const SmallPtrSet< PtrType, SmallSize > &RHS)
Definition: SmallPtrSet.h:318
static void * getEmptyMarker()
Definition: SmallPtrSet.h:95
void AdvanceIfNotValid()
AdvanceIfNotValid - If the current bucket isn't valid, advance to a bucket that is.
Definition: SmallPtrSet.h:168
void CopyFrom(const SmallPtrSetImplBase &RHS)
CopyFrom - implement operator= from a smallptrset that has the same pointer type, but may have a diff...
void insert(IterT I, IterT E)
Definition: SmallPtrSet.h:281
SmallPtrSet< PtrType, SmallSize > & operator=(SmallPtrSet< PtrType, SmallSize > &&RHS)
Definition: SmallPtrSet.h:325
size_type size() const
Definition: SmallPtrSet.h:79
const PtrTy operator*() const
Definition: SmallPtrSet.h:194
SmallPtrSetIterator operator++(int)
Definition: SmallPtrSet.h:205
std::pair< iterator, bool > insert(PtrType Ptr)
Inserts Ptr if and only if there is no element in the container equal to Ptr.
Definition: SmallPtrSet.h:264
SmallPtrSetImpl(const void **SmallStorage, unsigned SmallSize)
Definition: SmallPtrSet.h:253
const void *const * Bucket
Definition: SmallPtrSet.h:149
iterator begin() const
Definition: SmallPtrSet.h:286
bool operator==(const SmallPtrSetIteratorImpl &RHS) const
Definition: SmallPtrSet.h:157
const void *const * End
Definition: SmallPtrSet.h:150
SmallPtrSetIterator - This implements a const_iterator for SmallPtrSet.
Definition: SmallPtrSet.h:179
bool erase_imp(const void *Ptr)
erase_imp - If the set contains the specified pointer, remove it and return true, otherwise return fa...
Definition: SmallPtrSet.cpp:77
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements...
Definition: SmallPtrSet.h:299
bool erase(PtrType Ptr)
erase - If the set contains the specified pointer, remove it and return true, otherwise return false...
Definition: SmallPtrSet.h:271
const void ** SmallArray
SmallArray - Points to a fixed size set of buckets, used in 'small mode'.
Definition: SmallPtrSet.h:53
SmallPtrSetImplBase(const void **SmallStorage, unsigned SmallSize)
Definition: SmallPtrSet.h:68
SmallPtrSetIterator< PtrType > iterator
Definition: SmallPtrSet.h:257
SmallPtrSetImplBase(const void **SmallStorage, const SmallPtrSetImplBase &that)
void swap(llvm::BitVector &LHS, llvm::BitVector &RHS)
Implement std::swap in terms of BitVector swap.
Definition: BitVector.h:576
RoundUpToPowerOfTwoH - If N is not a power of two, increase it.
Definition: SmallPtrSet.h:218
SmallPtrSetImplBase - This is the common code shared among all the SmallPtrSet<>'s, which is almost everything.
Definition: SmallPtrSet.h:49
iterator end() const
Definition: SmallPtrSet.h:289
#define I(x, y, z)
Definition: MD5.cpp:54
#define N
std::pair< const void *const *, bool > insert_imp(const void *Ptr)
insert_imp - This returns true if the pointer was new to the set, false if it was already in the set...
Definition: SmallPtrSet.cpp:38
SmallPtrSetIteratorImpl(const void *const *BP, const void *const *E)
Definition: SmallPtrSet.h:152
void swap(SmallPtrSet< PtrType, SmallSize > &RHS)
swap - Swaps the elements of two sets.
Definition: SmallPtrSet.h:332
std::forward_iterator_tag iterator_category
Definition: SmallPtrSet.h:187