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 <cstdlib>
20
21using namespace llvm;
22
23void SmallPtrSetImplBase::shrink_and_clear() {
24  assert(!isSmall() && "Can't shrink a small set!");
25  free(CurArray);
26
27  // Reduce the number of buckets.
28  CurArraySize = NumElements > 16 ? 1 << (Log2_32_Ceil(NumElements) + 1) : 32;
29  NumElements = NumTombstones = 0;
30
31  // Install the new array.  Clear all the buckets to empty.
32  CurArray = (const void**)malloc(sizeof(void*) * CurArraySize);
33  assert(CurArray && "Failed to allocate memory?");
34  memset(CurArray, -1, CurArraySize*sizeof(void*));
35}
36
37bool SmallPtrSetImplBase::insert_imp(const void * Ptr) {
38  if (isSmall()) {
39    // Check to see if it is already in the set.
40    for (const void **APtr = SmallArray, **E = SmallArray+NumElements;
41         APtr != E; ++APtr)
42      if (*APtr == Ptr)
43        return false;
44
45    // Nope, there isn't.  If we stay small, just 'pushback' now.
46    if (NumElements < CurArraySize-1) {
47      SmallArray[NumElements++] = Ptr;
48      return true;
49    }
50    // Otherwise, hit the big set case, which will call grow.
51  }
52
53  if (NumElements*4 >= CurArraySize*3) {
54    // If more than 3/4 of the array is full, grow.
55    Grow(CurArraySize < 64 ? 128 : CurArraySize*2);
56  } else if (CurArraySize-(NumElements+NumTombstones) < CurArraySize/8) {
57    // If fewer of 1/8 of the array is empty (meaning that many are filled with
58    // tombstones), rehash.
59    Grow(CurArraySize);
60  }
61
62  // Okay, we know we have space.  Find a hash bucket.
63  const void **Bucket = const_cast<const void**>(FindBucketFor(Ptr));
64  if (*Bucket == Ptr) return false; // Already inserted, good.
65
66  // Otherwise, insert it!
67  if (*Bucket == getTombstoneMarker())
68    --NumTombstones;
69  *Bucket = Ptr;
70  ++NumElements;  // Track density.
71  return true;
72}
73
74bool SmallPtrSetImplBase::erase_imp(const void * Ptr) {
75  if (isSmall()) {
76    // Check to see if it is in the set.
77    for (const void **APtr = SmallArray, **E = SmallArray+NumElements;
78         APtr != E; ++APtr)
79      if (*APtr == Ptr) {
80        // If it is in the set, replace this element.
81        *APtr = E[-1];
82        E[-1] = getEmptyMarker();
83        --NumElements;
84        return true;
85      }
86
87    return false;
88  }
89
90  // Okay, we know we have space.  Find a hash bucket.
91  void **Bucket = const_cast<void**>(FindBucketFor(Ptr));
92  if (*Bucket != Ptr) return false;  // Not in the set?
93
94  // Set this as a tombstone.
95  *Bucket = getTombstoneMarker();
96  --NumElements;
97  ++NumTombstones;
98  return true;
99}
100
101const void * const *SmallPtrSetImplBase::FindBucketFor(const void *Ptr) const {
102  unsigned Bucket = DenseMapInfo<void *>::getHashValue(Ptr) & (CurArraySize-1);
103  unsigned ArraySize = CurArraySize;
104  unsigned ProbeAmt = 1;
105  const void *const *Array = CurArray;
106  const void *const *Tombstone = nullptr;
107  while (1) {
108    // Found Ptr's bucket?
109    if (Array[Bucket] == Ptr)
110      return Array+Bucket;
111
112    // If we found an empty bucket, the pointer doesn't exist in the set.
113    // Return a tombstone if we've seen one so far, or the empty bucket if
114    // not.
115    if (Array[Bucket] == getEmptyMarker())
116      return Tombstone ? Tombstone : Array+Bucket;
117
118    // If this is a tombstone, remember it.  If Ptr ends up not in the set, we
119    // prefer to return it than something that would require more probing.
120    if (Array[Bucket] == getTombstoneMarker() && !Tombstone)
121      Tombstone = Array+Bucket;  // Remember the first tombstone found.
122
123    // It's a hash collision or a tombstone. Reprobe.
124    Bucket = (Bucket + ProbeAmt++) & (ArraySize-1);
125  }
126}
127
128/// Grow - Allocate a larger backing store for the buckets and move it over.
129///
130void SmallPtrSetImplBase::Grow(unsigned NewSize) {
131  // Allocate at twice as many buckets, but at least 128.
132  unsigned OldSize = CurArraySize;
133
134  const void **OldBuckets = CurArray;
135  bool WasSmall = isSmall();
136
137  // Install the new array.  Clear all the buckets to empty.
138  CurArray = (const void**)malloc(sizeof(void*) * NewSize);
139  assert(CurArray && "Failed to allocate memory?");
140  CurArraySize = NewSize;
141  memset(CurArray, -1, NewSize*sizeof(void*));
142
143  // Copy over all the elements.
144  if (WasSmall) {
145    // Small sets store their elements in order.
146    for (const void **BucketPtr = OldBuckets, **E = OldBuckets+NumElements;
147         BucketPtr != E; ++BucketPtr) {
148      const void *Elt = *BucketPtr;
149      *const_cast<void**>(FindBucketFor(Elt)) = const_cast<void*>(Elt);
150    }
151  } else {
152    // Copy over all valid entries.
153    for (const void **BucketPtr = OldBuckets, **E = OldBuckets+OldSize;
154         BucketPtr != E; ++BucketPtr) {
155      // Copy over the element if it is valid.
156      const void *Elt = *BucketPtr;
157      if (Elt != getTombstoneMarker() && Elt != getEmptyMarker())
158        *const_cast<void**>(FindBucketFor(Elt)) = const_cast<void*>(Elt);
159    }
160
161    free(OldBuckets);
162    NumTombstones = 0;
163  }
164}
165
166SmallPtrSetImplBase::SmallPtrSetImplBase(const void **SmallStorage,
167                                 const SmallPtrSetImplBase& that) {
168  SmallArray = SmallStorage;
169
170  // If we're becoming small, prepare to insert into our stack space
171  if (that.isSmall()) {
172    CurArray = SmallArray;
173  // Otherwise, allocate new heap space (unless we were the same size)
174  } else {
175    CurArray = (const void**)malloc(sizeof(void*) * that.CurArraySize);
176    assert(CurArray && "Failed to allocate memory?");
177  }
178
179  // Copy over the new array size
180  CurArraySize = that.CurArraySize;
181
182  // Copy over the contents from the other set
183  memcpy(CurArray, that.CurArray, sizeof(void*)*CurArraySize);
184
185  NumElements = that.NumElements;
186  NumTombstones = that.NumTombstones;
187}
188
189SmallPtrSetImplBase::SmallPtrSetImplBase(const void **SmallStorage,
190                                         unsigned SmallSize,
191                                         SmallPtrSetImplBase &&that) {
192  SmallArray = SmallStorage;
193
194  // Copy over the basic members.
195  CurArraySize = that.CurArraySize;
196  NumElements = that.NumElements;
197  NumTombstones = that.NumTombstones;
198
199  // When small, just copy into our small buffer.
200  if (that.isSmall()) {
201    CurArray = SmallArray;
202    memcpy(CurArray, that.CurArray, sizeof(void *) * CurArraySize);
203    return;
204  }
205
206  // Otherwise, we steal the large memory allocation and no copy is needed.
207  CurArray = that.CurArray;
208  that.CurArray = that.SmallArray;
209
210  // Make the "that" object small and empty.
211  that.CurArraySize = SmallSize;
212  assert(that.CurArray == that.SmallArray);
213  that.NumElements = 0;
214  that.NumTombstones = 0;
215}
216
217/// CopyFrom - implement operator= from a smallptrset that has the same pointer
218/// type, but may have a different small size.
219void SmallPtrSetImplBase::CopyFrom(const SmallPtrSetImplBase &RHS) {
220  assert(&RHS != this && "Self-copy should be handled by the caller.");
221
222  if (isSmall() && RHS.isSmall())
223    assert(CurArraySize == RHS.CurArraySize &&
224           "Cannot assign sets with different small sizes");
225
226  // If we're becoming small, prepare to insert into our stack space
227  if (RHS.isSmall()) {
228    if (!isSmall())
229      free(CurArray);
230    CurArray = SmallArray;
231  // Otherwise, allocate new heap space (unless we were the same size)
232  } else if (CurArraySize != RHS.CurArraySize) {
233    if (isSmall())
234      CurArray = (const void**)malloc(sizeof(void*) * RHS.CurArraySize);
235    else {
236      const void **T = (const void**)realloc(CurArray,
237                                             sizeof(void*) * RHS.CurArraySize);
238      if (!T)
239        free(CurArray);
240      CurArray = T;
241    }
242    assert(CurArray && "Failed to allocate memory?");
243  }
244
245  // Copy over the new array size
246  CurArraySize = RHS.CurArraySize;
247
248  // Copy over the contents from the other set
249  memcpy(CurArray, RHS.CurArray, sizeof(void*)*CurArraySize);
250
251  NumElements = RHS.NumElements;
252  NumTombstones = RHS.NumTombstones;
253}
254
255void SmallPtrSetImplBase::MoveFrom(unsigned SmallSize,
256                                   SmallPtrSetImplBase &&RHS) {
257  assert(&RHS != this && "Self-move should be handled by the caller.");
258
259  if (!isSmall())
260    free(CurArray);
261
262  if (RHS.isSmall()) {
263    // Copy a small RHS rather than moving.
264    CurArray = SmallArray;
265    memcpy(CurArray, RHS.CurArray, sizeof(void*)*RHS.CurArraySize);
266  } else {
267    CurArray = RHS.CurArray;
268    RHS.CurArray = RHS.SmallArray;
269  }
270
271  // Copy the rest of the trivial members.
272  CurArraySize = RHS.CurArraySize;
273  NumElements = RHS.NumElements;
274  NumTombstones = RHS.NumTombstones;
275
276  // Make the RHS small and empty.
277  RHS.CurArraySize = SmallSize;
278  assert(RHS.CurArray == RHS.SmallArray);
279  RHS.NumElements = 0;
280  RHS.NumTombstones = 0;
281}
282
283void SmallPtrSetImplBase::swap(SmallPtrSetImplBase &RHS) {
284  if (this == &RHS) return;
285
286  // We can only avoid copying elements if neither set is small.
287  if (!this->isSmall() && !RHS.isSmall()) {
288    std::swap(this->CurArray, RHS.CurArray);
289    std::swap(this->CurArraySize, RHS.CurArraySize);
290    std::swap(this->NumElements, RHS.NumElements);
291    std::swap(this->NumTombstones, RHS.NumTombstones);
292    return;
293  }
294
295  // FIXME: From here on we assume that both sets have the same small size.
296
297  // If only RHS is small, copy the small elements into LHS and move the pointer
298  // from LHS to RHS.
299  if (!this->isSmall() && RHS.isSmall()) {
300    std::copy(RHS.SmallArray, RHS.SmallArray+RHS.CurArraySize,
301              this->SmallArray);
302    std::swap(this->NumElements, RHS.NumElements);
303    std::swap(this->CurArraySize, RHS.CurArraySize);
304    RHS.CurArray = this->CurArray;
305    RHS.NumTombstones = this->NumTombstones;
306    this->CurArray = this->SmallArray;
307    this->NumTombstones = 0;
308    return;
309  }
310
311  // If only LHS is small, copy the small elements into RHS and move the pointer
312  // from RHS to LHS.
313  if (this->isSmall() && !RHS.isSmall()) {
314    std::copy(this->SmallArray, this->SmallArray+this->CurArraySize,
315              RHS.SmallArray);
316    std::swap(RHS.NumElements, this->NumElements);
317    std::swap(RHS.CurArraySize, this->CurArraySize);
318    this->CurArray = RHS.CurArray;
319    this->NumTombstones = RHS.NumTombstones;
320    RHS.CurArray = RHS.SmallArray;
321    RHS.NumTombstones = 0;
322    return;
323  }
324
325  // Both a small, just swap the small elements.
326  assert(this->isSmall() && RHS.isSmall());
327  assert(this->CurArraySize == RHS.CurArraySize);
328  std::swap_ranges(this->SmallArray, this->SmallArray+this->CurArraySize,
329                   RHS.SmallArray);
330  std::swap(this->NumElements, RHS.NumElements);
331}
332
333SmallPtrSetImplBase::~SmallPtrSetImplBase() {
334  if (!isSmall())
335    free(CurArray);
336}
337