1//===- llvm/ADT/SmallPtrSet.cpp - 'Normally small' pointer set ------------===//
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 implements the SmallPtrSet class.  See SmallPtrSet.h for an
11// overview of the algorithm.
12//
13//===----------------------------------------------------------------------===//
14
15#include "llvm/ADT/SmallPtrSet.h"
16#include "llvm/ADT/DenseMapInfo.h"
17#include "llvm/Support/MathExtras.h"
18#include <algorithm>
19#include <cassert>
20#include <cstdlib>
21
22using namespace llvm;
23
24void SmallPtrSetImplBase::shrink_and_clear() {
25  assert(!isSmall() && "Can't shrink a small set!");
26  free(CurArray);
27
28  // Reduce the number of buckets.
29  unsigned Size = size();
30  CurArraySize = Size > 16 ? 1 << (Log2_32_Ceil(Size) + 1) : 32;
31  NumNonEmpty = NumTombstones = 0;
32
33  // Install the new array.  Clear all the buckets to empty.
34  CurArray = (const void**)malloc(sizeof(void*) * CurArraySize);
35  assert(CurArray && "Failed to allocate memory?");
36  memset(CurArray, -1, CurArraySize*sizeof(void*));
37}
38
39std::pair<const void *const *, bool>
40SmallPtrSetImplBase::insert_imp_big(const void *Ptr) {
41  if (LLVM_UNLIKELY(size() * 4 >= CurArraySize * 3)) {
42    // If more than 3/4 of the array is full, grow.
43    Grow(CurArraySize < 64 ? 128 : CurArraySize * 2);
44  } else if (LLVM_UNLIKELY(CurArraySize - NumNonEmpty < CurArraySize / 8)) {
45    // If fewer of 1/8 of the array is empty (meaning that many are filled with
46    // tombstones), rehash.
47    Grow(CurArraySize);
48  }
49
50  // Okay, we know we have space.  Find a hash bucket.
51  const void **Bucket = const_cast<const void**>(FindBucketFor(Ptr));
52  if (*Bucket == Ptr)
53    return std::make_pair(Bucket, false); // Already inserted, good.
54
55  // Otherwise, insert it!
56  if (*Bucket == getTombstoneMarker())
57    --NumTombstones;
58  else
59    ++NumNonEmpty; // Track density.
60  *Bucket = Ptr;
61  return std::make_pair(Bucket, true);
62}
63
64bool SmallPtrSetImplBase::erase_imp(const void * Ptr) {
65  if (isSmall()) {
66    // Check to see if it is in the set.
67    for (const void **APtr = CurArray, **E = CurArray + NumNonEmpty; APtr != E;
68         ++APtr)
69      if (*APtr == Ptr) {
70        // If it is in the set, replace this element.
71        *APtr = getTombstoneMarker();
72        ++NumTombstones;
73        return true;
74      }
75
76    return false;
77  }
78
79  // Okay, we know we have space.  Find a hash bucket.
80  void **Bucket = const_cast<void**>(FindBucketFor(Ptr));
81  if (*Bucket != Ptr) return false;  // Not in the set?
82
83  // Set this as a tombstone.
84  *Bucket = getTombstoneMarker();
85  ++NumTombstones;
86  return true;
87}
88
89const void * const *SmallPtrSetImplBase::FindBucketFor(const void *Ptr) const {
90  unsigned Bucket = DenseMapInfo<void *>::getHashValue(Ptr) & (CurArraySize-1);
91  unsigned ArraySize = CurArraySize;
92  unsigned ProbeAmt = 1;
93  const void *const *Array = CurArray;
94  const void *const *Tombstone = nullptr;
95  while (true) {
96    // If we found an empty bucket, the pointer doesn't exist in the set.
97    // Return a tombstone if we've seen one so far, or the empty bucket if
98    // not.
99    if (LLVM_LIKELY(Array[Bucket] == getEmptyMarker()))
100      return Tombstone ? Tombstone : Array+Bucket;
101
102    // Found Ptr's bucket?
103    if (LLVM_LIKELY(Array[Bucket] == Ptr))
104      return Array+Bucket;
105
106    // If this is a tombstone, remember it.  If Ptr ends up not in the set, we
107    // prefer to return it than something that would require more probing.
108    if (Array[Bucket] == getTombstoneMarker() && !Tombstone)
109      Tombstone = Array+Bucket;  // Remember the first tombstone found.
110
111    // It's a hash collision or a tombstone. Reprobe.
112    Bucket = (Bucket + ProbeAmt++) & (ArraySize-1);
113  }
114}
115
116/// Grow - Allocate a larger backing store for the buckets and move it over.
117///
118void SmallPtrSetImplBase::Grow(unsigned NewSize) {
119  const void **OldBuckets = CurArray;
120  const void **OldEnd = EndPointer();
121  bool WasSmall = isSmall();
122
123  // Install the new array.  Clear all the buckets to empty.
124  CurArray = (const void**)malloc(sizeof(void*) * NewSize);
125  assert(CurArray && "Failed to allocate memory?");
126  CurArraySize = NewSize;
127  memset(CurArray, -1, NewSize*sizeof(void*));
128
129  // Copy over all valid entries.
130  for (const void **BucketPtr = OldBuckets; BucketPtr != OldEnd; ++BucketPtr) {
131    // Copy over the element if it is valid.
132    const void *Elt = *BucketPtr;
133    if (Elt != getTombstoneMarker() && Elt != getEmptyMarker())
134      *const_cast<void**>(FindBucketFor(Elt)) = const_cast<void*>(Elt);
135  }
136
137  if (!WasSmall)
138    free(OldBuckets);
139  NumNonEmpty -= NumTombstones;
140  NumTombstones = 0;
141}
142
143SmallPtrSetImplBase::SmallPtrSetImplBase(const void **SmallStorage,
144                                         const SmallPtrSetImplBase &that) {
145  SmallArray = SmallStorage;
146
147  // If we're becoming small, prepare to insert into our stack space
148  if (that.isSmall()) {
149    CurArray = SmallArray;
150  // Otherwise, allocate new heap space (unless we were the same size)
151  } else {
152    CurArray = (const void**)malloc(sizeof(void*) * that.CurArraySize);
153    assert(CurArray && "Failed to allocate memory?");
154  }
155
156  // Copy over the that array.
157  CopyHelper(that);
158}
159
160SmallPtrSetImplBase::SmallPtrSetImplBase(const void **SmallStorage,
161                                         unsigned SmallSize,
162                                         SmallPtrSetImplBase &&that) {
163  SmallArray = SmallStorage;
164  MoveHelper(SmallSize, std::move(that));
165}
166
167void SmallPtrSetImplBase::CopyFrom(const SmallPtrSetImplBase &RHS) {
168  assert(&RHS != this && "Self-copy should be handled by the caller.");
169
170  if (isSmall() && RHS.isSmall())
171    assert(CurArraySize == RHS.CurArraySize &&
172           "Cannot assign sets with different small sizes");
173
174  // If we're becoming small, prepare to insert into our stack space
175  if (RHS.isSmall()) {
176    if (!isSmall())
177      free(CurArray);
178    CurArray = SmallArray;
179  // Otherwise, allocate new heap space (unless we were the same size)
180  } else if (CurArraySize != RHS.CurArraySize) {
181    if (isSmall())
182      CurArray = (const void**)malloc(sizeof(void*) * RHS.CurArraySize);
183    else {
184      const void **T = (const void**)realloc(CurArray,
185                                             sizeof(void*) * RHS.CurArraySize);
186      if (!T)
187        free(CurArray);
188      CurArray = T;
189    }
190    assert(CurArray && "Failed to allocate memory?");
191  }
192
193  CopyHelper(RHS);
194}
195
196void SmallPtrSetImplBase::CopyHelper(const SmallPtrSetImplBase &RHS) {
197  // Copy over the new array size
198  CurArraySize = RHS.CurArraySize;
199
200  // Copy over the contents from the other set
201  std::copy(RHS.CurArray, RHS.EndPointer(), CurArray);
202
203  NumNonEmpty = RHS.NumNonEmpty;
204  NumTombstones = RHS.NumTombstones;
205}
206
207void SmallPtrSetImplBase::MoveFrom(unsigned SmallSize,
208                                   SmallPtrSetImplBase &&RHS) {
209  if (!isSmall())
210    free(CurArray);
211  MoveHelper(SmallSize, std::move(RHS));
212}
213
214void SmallPtrSetImplBase::MoveHelper(unsigned SmallSize,
215                                     SmallPtrSetImplBase &&RHS) {
216  assert(&RHS != this && "Self-move should be handled by the caller.");
217
218  if (RHS.isSmall()) {
219    // Copy a small RHS rather than moving.
220    CurArray = SmallArray;
221    std::copy(RHS.CurArray, RHS.CurArray + RHS.NumNonEmpty, CurArray);
222  } else {
223    CurArray = RHS.CurArray;
224    RHS.CurArray = RHS.SmallArray;
225  }
226
227  // Copy the rest of the trivial members.
228  CurArraySize = RHS.CurArraySize;
229  NumNonEmpty = RHS.NumNonEmpty;
230  NumTombstones = RHS.NumTombstones;
231
232  // Make the RHS small and empty.
233  RHS.CurArraySize = SmallSize;
234  assert(RHS.CurArray == RHS.SmallArray);
235  RHS.NumNonEmpty = 0;
236  RHS.NumTombstones = 0;
237}
238
239void SmallPtrSetImplBase::swap(SmallPtrSetImplBase &RHS) {
240  if (this == &RHS) return;
241
242  // We can only avoid copying elements if neither set is small.
243  if (!this->isSmall() && !RHS.isSmall()) {
244    std::swap(this->CurArray, RHS.CurArray);
245    std::swap(this->CurArraySize, RHS.CurArraySize);
246    std::swap(this->NumNonEmpty, RHS.NumNonEmpty);
247    std::swap(this->NumTombstones, RHS.NumTombstones);
248    return;
249  }
250
251  // FIXME: From here on we assume that both sets have the same small size.
252
253  // If only RHS is small, copy the small elements into LHS and move the pointer
254  // from LHS to RHS.
255  if (!this->isSmall() && RHS.isSmall()) {
256    assert(RHS.CurArray == RHS.SmallArray);
257    std::copy(RHS.CurArray, RHS.CurArray + RHS.NumNonEmpty, this->SmallArray);
258    std::swap(RHS.CurArraySize, this->CurArraySize);
259    std::swap(this->NumNonEmpty, RHS.NumNonEmpty);
260    std::swap(this->NumTombstones, RHS.NumTombstones);
261    RHS.CurArray = this->CurArray;
262    this->CurArray = this->SmallArray;
263    return;
264  }
265
266  // If only LHS is small, copy the small elements into RHS and move the pointer
267  // from RHS to LHS.
268  if (this->isSmall() && !RHS.isSmall()) {
269    assert(this->CurArray == this->SmallArray);
270    std::copy(this->CurArray, this->CurArray + this->NumNonEmpty,
271              RHS.SmallArray);
272    std::swap(RHS.CurArraySize, this->CurArraySize);
273    std::swap(RHS.NumNonEmpty, this->NumNonEmpty);
274    std::swap(RHS.NumTombstones, this->NumTombstones);
275    this->CurArray = RHS.CurArray;
276    RHS.CurArray = RHS.SmallArray;
277    return;
278  }
279
280  // Both a small, just swap the small elements.
281  assert(this->isSmall() && RHS.isSmall());
282  unsigned MinNonEmpty = std::min(this->NumNonEmpty, RHS.NumNonEmpty);
283  std::swap_ranges(this->SmallArray, this->SmallArray + MinNonEmpty,
284                   RHS.SmallArray);
285  if (this->NumNonEmpty > MinNonEmpty) {
286    std::copy(this->SmallArray + MinNonEmpty,
287              this->SmallArray + this->NumNonEmpty,
288              RHS.SmallArray + MinNonEmpty);
289  } else {
290    std::copy(RHS.SmallArray + MinNonEmpty, RHS.SmallArray + RHS.NumNonEmpty,
291              this->SmallArray + MinNonEmpty);
292  }
293  assert(this->CurArraySize == RHS.CurArraySize);
294  std::swap(this->NumNonEmpty, RHS.NumNonEmpty);
295  std::swap(this->NumTombstones, RHS.NumTombstones);
296}
297