LLVM  8.0.0svn
SmallSet.h
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1 //===- llvm/ADT/SmallSet.h - 'Normally small' sets --------------*- 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 SmallSet class.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_ADT_SMALLSET_H
15 #define LLVM_ADT_SMALLSET_H
16 
17 #include "llvm/ADT/None.h"
18 #include "llvm/ADT/SmallPtrSet.h"
19 #include "llvm/ADT/SmallVector.h"
20 #include "llvm/ADT/iterator.h"
21 #include "llvm/Support/Compiler.h"
23 #include <cstddef>
24 #include <functional>
25 #include <set>
26 #include <type_traits>
27 #include <utility>
28 
29 namespace llvm {
30 
31 /// SmallSetIterator - This class implements a const_iterator for SmallSet by
32 /// delegating to the underlying SmallVector or Set iterators.
33 template <typename T, unsigned N, typename C>
35  : public iterator_facade_base<SmallSetIterator<T, N, C>,
36  std::forward_iterator_tag, T> {
37 private:
38  using SetIterTy = typename std::set<T, C>::const_iterator;
39  using VecIterTy = typename SmallVector<T, N>::const_iterator;
41 
42  /// Iterators to the parts of the SmallSet containing the data. They are set
43  /// depending on isSmall.
44  union {
45  SetIterTy SetIter;
46  VecIterTy VecIter;
47  };
48 
49  bool isSmall;
50 
51 public:
52  SmallSetIterator(SetIterTy SetIter) : SetIter(SetIter), isSmall(false) {}
53 
54  SmallSetIterator(VecIterTy VecIter) : VecIter(VecIter), isSmall(true) {}
55 
56  // Spell out destructor, copy/move constructor and assignment operators for
57  // MSVC STL, where set<T>::const_iterator is not trivially copy constructible.
59  if (isSmall)
60  VecIter.~VecIterTy();
61  else
62  SetIter.~SetIterTy();
63  }
64 
65  SmallSetIterator(const SmallSetIterator &Other) : isSmall(Other.isSmall) {
66  if (isSmall)
67  VecIter = Other.VecIter;
68  else
69  // Use placement new, to make sure SetIter is properly constructed, even
70  // if it is not trivially copy-able (e.g. in MSVC).
71  new (&SetIter) SetIterTy(Other.SetIter);
72  }
73 
74  SmallSetIterator(SmallSetIterator &&Other) : isSmall(Other.isSmall) {
75  if (isSmall)
76  VecIter = std::move(Other.VecIter);
77  else
78  // Use placement new, to make sure SetIter is properly constructed, even
79  // if it is not trivially copy-able (e.g. in MSVC).
80  new (&SetIter) SetIterTy(std::move(Other.SetIter));
81  }
82 
84  // Call destructor for SetIter, so it gets properly destroyed if it is
85  // not trivially destructible in case we are setting VecIter.
86  if (!isSmall)
87  SetIter.~SetIterTy();
88 
89  isSmall = Other.isSmall;
90  if (isSmall)
91  VecIter = Other.VecIter;
92  else
93  new (&SetIter) SetIterTy(Other.SetIter);
94  return *this;
95  }
96 
98  // Call destructor for SetIter, so it gets properly destroyed if it is
99  // not trivially destructible in case we are setting VecIter.
100  if (!isSmall)
101  SetIter.~SetIterTy();
102 
103  isSmall = Other.isSmall;
104  if (isSmall)
105  VecIter = std::move(Other.VecIter);
106  else
107  new (&SetIter) SetIterTy(std::move(Other.SetIter));
108  return *this;
109  }
110 
111  bool operator==(const SmallSetIterator &RHS) const {
112  if (isSmall != RHS.isSmall)
113  return false;
114  if (isSmall)
115  return VecIter == RHS.VecIter;
116  return SetIter == RHS.SetIter;
117  }
118 
119  SmallSetIterator &operator++() { // Preincrement
120  if (isSmall)
121  VecIter++;
122  else
123  SetIter++;
124  return *this;
125  }
126 
127  const T &operator*() const { return isSmall ? *VecIter : *SetIter; }
128 };
129 
130 /// SmallSet - This maintains a set of unique values, optimizing for the case
131 /// when the set is small (less than N). In this case, the set can be
132 /// maintained with no mallocs. If the set gets large, we expand to using an
133 /// std::set to maintain reasonable lookup times.
134 template <typename T, unsigned N, typename C = std::less<T>>
135 class SmallSet {
136  /// Use a SmallVector to hold the elements here (even though it will never
137  /// reach its 'large' stage) to avoid calling the default ctors of elements
138  /// we will never use.
139  SmallVector<T, N> Vector;
140  std::set<T, C> Set;
141 
142  using VIterator = typename SmallVector<T, N>::const_iterator;
143  using mutable_iterator = typename SmallVector<T, N>::iterator;
144 
145  // In small mode SmallPtrSet uses linear search for the elements, so it is
146  // not a good idea to choose this value too high. You may consider using a
147  // DenseSet<> instead if you expect many elements in the set.
148  static_assert(N <= 32, "N should be small");
149 
150 public:
151  using size_type = size_t;
153 
154  SmallSet() = default;
155 
156  LLVM_NODISCARD bool empty() const {
157  return Vector.empty() && Set.empty();
158  }
159 
160  size_type size() const {
161  return isSmall() ? Vector.size() : Set.size();
162  }
163 
164  /// count - Return 1 if the element is in the set, 0 otherwise.
165  size_type count(const T &V) const {
166  if (isSmall()) {
167  // Since the collection is small, just do a linear search.
168  return vfind(V) == Vector.end() ? 0 : 1;
169  } else {
170  return Set.count(V);
171  }
172  }
173 
174  /// insert - Insert an element into the set if it isn't already there.
175  /// Returns true if the element is inserted (it was not in the set before).
176  /// The first value of the returned pair is unused and provided for
177  /// partial compatibility with the standard library self-associative container
178  /// concept.
179  // FIXME: Add iterators that abstract over the small and large form, and then
180  // return those here.
181  std::pair<NoneType, bool> insert(const T &V) {
182  if (!isSmall())
183  return std::make_pair(None, Set.insert(V).second);
184 
185  VIterator I = vfind(V);
186  if (I != Vector.end()) // Don't reinsert if it already exists.
187  return std::make_pair(None, false);
188  if (Vector.size() < N) {
189  Vector.push_back(V);
190  return std::make_pair(None, true);
191  }
192 
193  // Otherwise, grow from vector to set.
194  while (!Vector.empty()) {
195  Set.insert(Vector.back());
196  Vector.pop_back();
197  }
198  Set.insert(V);
199  return std::make_pair(None, true);
200  }
201 
202  template <typename IterT>
203  void insert(IterT I, IterT E) {
204  for (; I != E; ++I)
205  insert(*I);
206  }
207 
208  bool erase(const T &V) {
209  if (!isSmall())
210  return Set.erase(V);
211  for (mutable_iterator I = Vector.begin(), E = Vector.end(); I != E; ++I)
212  if (*I == V) {
213  Vector.erase(I);
214  return true;
215  }
216  return false;
217  }
218 
219  void clear() {
220  Vector.clear();
221  Set.clear();
222  }
223 
225  if (isSmall())
226  return {Vector.begin()};
227  return {Set.begin()};
228  }
229 
230  const_iterator end() const {
231  if (isSmall())
232  return {Vector.end()};
233  return {Set.end()};
234  }
235 
236 private:
237  bool isSmall() const { return Set.empty(); }
238 
239  VIterator vfind(const T &V) const {
240  for (VIterator I = Vector.begin(), E = Vector.end(); I != E; ++I)
241  if (*I == V)
242  return I;
243  return Vector.end();
244  }
245 };
246 
247 /// If this set is of pointer values, transparently switch over to using
248 /// SmallPtrSet for performance.
249 template <typename PointeeType, unsigned N>
250 class SmallSet<PointeeType*, N> : public SmallPtrSet<PointeeType*, N> {};
251 
252 } // end namespace llvm
253 
254 #endif // LLVM_ADT_SMALLSET_H
typename SuperClass::const_iterator const_iterator
Definition: SmallVector.h:328
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
SmallSetIterator & operator++()
Definition: SmallSet.h:119
#define LLVM_NODISCARD
LLVM_NODISCARD - Warn if a type or return value is discarded.
Definition: Compiler.h:129
block Block Frequency true
bool operator==(const SmallSetIterator &RHS) const
Definition: SmallSet.h:111
bool erase(const T &V)
Definition: SmallSet.h:208
LLVM_NODISCARD bool empty() const
Definition: SmallSet.h:156
const_iterator begin() const
Definition: SmallSet.h:224
ELFYAML::ELF_STO Other
Definition: ELFYAML.cpp:773
SmallSetIterator & operator=(const SmallSetIterator &Other)
Definition: SmallSet.h:83
void clear()
Definition: SmallSet.h:219
SmallSetIterator(SmallSetIterator &&Other)
Definition: SmallSet.h:74
const_iterator end() const
Definition: SmallSet.h:230
CRTP base class which implements the entire standard iterator facade in terms of a minimal subset of ...
Definition: iterator.h:68
void insert(IterT I, IterT E)
Definition: SmallSet.h:203
SmallSetIterator(SetIterTy SetIter)
Definition: SmallSet.h:52
const T & operator*() const
Definition: SmallSet.h:127
static GCRegistry::Add< CoreCLRGC > E("coreclr", "CoreCLR-compatible GC")
LLVM_ATTRIBUTE_ALWAYS_INLINE iterator begin()
Definition: SmallVector.h:129
SmallSet - This maintains a set of unique values, optimizing for the case when the set is small (less...
Definition: SmallSet.h:135
size_type size() const
Definition: SmallSet.h:160
SmallSetIterator(VecIterTy VecIter)
Definition: SmallSet.h:54
std::pair< NoneType, bool > insert(const T &V)
insert - Insert an element into the set if it isn&#39;t already there.
Definition: SmallSet.h:181
SmallSetIterator(const SmallSetIterator &Other)
Definition: SmallSet.h:65
iterator erase(const_iterator CI)
Definition: SmallVector.h:445
size_t size() const
Definition: SmallVector.h:53
This is a &#39;vector&#39; (really, a variable-sized array), optimized for the case when the array is small...
Definition: SmallVector.h:847
typename SuperClass::iterator iterator
Definition: SmallVector.h:327
SmallSetIterator - This class implements a const_iterator for SmallSet by delegating to the underlyin...
Definition: SmallSet.h:34
SmallSetIterator & operator=(SmallSetIterator &&Other)
Definition: SmallSet.h:97
LLVM_ATTRIBUTE_ALWAYS_INLINE iterator end()
Definition: SmallVector.h:133
LLVM_NODISCARD bool empty() const
Definition: SmallVector.h:56
#define I(x, y, z)
Definition: MD5.cpp:58
#define N
size_type count(const T &V) const
count - Return 1 if the element is in the set, 0 otherwise.
Definition: SmallSet.h:165