xref: /freebsd/contrib/llvm-project/llvm/lib/Support/SmallPtrSet.cpp (revision 32100375a661c1e16588ddfa7b90ca8d26cb9786)
1 //===- llvm/ADT/SmallPtrSet.cpp - 'Normally small' pointer set ------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements the SmallPtrSet class.  See SmallPtrSet.h for an
10 // overview of the algorithm.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/ADT/SmallPtrSet.h"
15 #include "llvm/ADT/DenseMapInfo.h"
16 #include "llvm/Support/MathExtras.h"
17 #include "llvm/Support/ErrorHandling.h"
18 #include <algorithm>
19 #include <cassert>
20 #include <cstdlib>
21 
22 using namespace llvm;
23 
24 void 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**)safe_malloc(sizeof(void*) * CurArraySize);
35 
36   memset(CurArray, -1, CurArraySize*sizeof(void*));
37 }
38 
39 std::pair<const void *const *, bool>
40 SmallPtrSetImplBase::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   incrementEpoch();
62   return std::make_pair(Bucket, true);
63 }
64 
65 const void * const *SmallPtrSetImplBase::FindBucketFor(const void *Ptr) const {
66   unsigned Bucket = DenseMapInfo<void *>::getHashValue(Ptr) & (CurArraySize-1);
67   unsigned ArraySize = CurArraySize;
68   unsigned ProbeAmt = 1;
69   const void *const *Array = CurArray;
70   const void *const *Tombstone = nullptr;
71   while (true) {
72     // If we found an empty bucket, the pointer doesn't exist in the set.
73     // Return a tombstone if we've seen one so far, or the empty bucket if
74     // not.
75     if (LLVM_LIKELY(Array[Bucket] == getEmptyMarker()))
76       return Tombstone ? Tombstone : Array+Bucket;
77 
78     // Found Ptr's bucket?
79     if (LLVM_LIKELY(Array[Bucket] == Ptr))
80       return Array+Bucket;
81 
82     // If this is a tombstone, remember it.  If Ptr ends up not in the set, we
83     // prefer to return it than something that would require more probing.
84     if (Array[Bucket] == getTombstoneMarker() && !Tombstone)
85       Tombstone = Array+Bucket;  // Remember the first tombstone found.
86 
87     // It's a hash collision or a tombstone. Reprobe.
88     Bucket = (Bucket + ProbeAmt++) & (ArraySize-1);
89   }
90 }
91 
92 /// Grow - Allocate a larger backing store for the buckets and move it over.
93 ///
94 void SmallPtrSetImplBase::Grow(unsigned NewSize) {
95   const void **OldBuckets = CurArray;
96   const void **OldEnd = EndPointer();
97   bool WasSmall = isSmall();
98 
99   // Install the new array.  Clear all the buckets to empty.
100   const void **NewBuckets = (const void**) safe_malloc(sizeof(void*) * NewSize);
101 
102   // Reset member only if memory was allocated successfully
103   CurArray = NewBuckets;
104   CurArraySize = NewSize;
105   memset(CurArray, -1, NewSize*sizeof(void*));
106 
107   // Copy over all valid entries.
108   for (const void **BucketPtr = OldBuckets; BucketPtr != OldEnd; ++BucketPtr) {
109     // Copy over the element if it is valid.
110     const void *Elt = *BucketPtr;
111     if (Elt != getTombstoneMarker() && Elt != getEmptyMarker())
112       *const_cast<void**>(FindBucketFor(Elt)) = const_cast<void*>(Elt);
113   }
114 
115   if (!WasSmall)
116     free(OldBuckets);
117   NumNonEmpty -= NumTombstones;
118   NumTombstones = 0;
119 }
120 
121 SmallPtrSetImplBase::SmallPtrSetImplBase(const void **SmallStorage,
122                                          const SmallPtrSetImplBase &that) {
123   SmallArray = SmallStorage;
124 
125   // If we're becoming small, prepare to insert into our stack space
126   if (that.isSmall()) {
127     CurArray = SmallArray;
128   // Otherwise, allocate new heap space (unless we were the same size)
129   } else {
130     CurArray = (const void**)safe_malloc(sizeof(void*) * that.CurArraySize);
131   }
132 
133   // Copy over the that array.
134   CopyHelper(that);
135 }
136 
137 SmallPtrSetImplBase::SmallPtrSetImplBase(const void **SmallStorage,
138                                          unsigned SmallSize,
139                                          SmallPtrSetImplBase &&that) {
140   SmallArray = SmallStorage;
141   MoveHelper(SmallSize, std::move(that));
142 }
143 
144 void SmallPtrSetImplBase::CopyFrom(const SmallPtrSetImplBase &RHS) {
145   assert(&RHS != this && "Self-copy should be handled by the caller.");
146 
147   if (isSmall() && RHS.isSmall())
148     assert(CurArraySize == RHS.CurArraySize &&
149            "Cannot assign sets with different small sizes");
150 
151   // If we're becoming small, prepare to insert into our stack space
152   if (RHS.isSmall()) {
153     if (!isSmall())
154       free(CurArray);
155     CurArray = SmallArray;
156   // Otherwise, allocate new heap space (unless we were the same size)
157   } else if (CurArraySize != RHS.CurArraySize) {
158     if (isSmall())
159       CurArray = (const void**)safe_malloc(sizeof(void*) * RHS.CurArraySize);
160     else {
161       const void **T = (const void**)safe_realloc(CurArray,
162                                              sizeof(void*) * RHS.CurArraySize);
163       CurArray = T;
164     }
165   }
166 
167   CopyHelper(RHS);
168 }
169 
170 void SmallPtrSetImplBase::CopyHelper(const SmallPtrSetImplBase &RHS) {
171   // Copy over the new array size
172   CurArraySize = RHS.CurArraySize;
173 
174   // Copy over the contents from the other set
175   std::copy(RHS.CurArray, RHS.EndPointer(), CurArray);
176 
177   NumNonEmpty = RHS.NumNonEmpty;
178   NumTombstones = RHS.NumTombstones;
179 }
180 
181 void SmallPtrSetImplBase::MoveFrom(unsigned SmallSize,
182                                    SmallPtrSetImplBase &&RHS) {
183   if (!isSmall())
184     free(CurArray);
185   MoveHelper(SmallSize, std::move(RHS));
186 }
187 
188 void SmallPtrSetImplBase::MoveHelper(unsigned SmallSize,
189                                      SmallPtrSetImplBase &&RHS) {
190   assert(&RHS != this && "Self-move should be handled by the caller.");
191 
192   if (RHS.isSmall()) {
193     // Copy a small RHS rather than moving.
194     CurArray = SmallArray;
195     std::copy(RHS.CurArray, RHS.CurArray + RHS.NumNonEmpty, CurArray);
196   } else {
197     CurArray = RHS.CurArray;
198     RHS.CurArray = RHS.SmallArray;
199   }
200 
201   // Copy the rest of the trivial members.
202   CurArraySize = RHS.CurArraySize;
203   NumNonEmpty = RHS.NumNonEmpty;
204   NumTombstones = RHS.NumTombstones;
205 
206   // Make the RHS small and empty.
207   RHS.CurArraySize = SmallSize;
208   assert(RHS.CurArray == RHS.SmallArray);
209   RHS.NumNonEmpty = 0;
210   RHS.NumTombstones = 0;
211 }
212 
213 void SmallPtrSetImplBase::swap(SmallPtrSetImplBase &RHS) {
214   if (this == &RHS) return;
215 
216   // We can only avoid copying elements if neither set is small.
217   if (!this->isSmall() && !RHS.isSmall()) {
218     std::swap(this->CurArray, RHS.CurArray);
219     std::swap(this->CurArraySize, RHS.CurArraySize);
220     std::swap(this->NumNonEmpty, RHS.NumNonEmpty);
221     std::swap(this->NumTombstones, RHS.NumTombstones);
222     return;
223   }
224 
225   // FIXME: From here on we assume that both sets have the same small size.
226 
227   // If only RHS is small, copy the small elements into LHS and move the pointer
228   // from LHS to RHS.
229   if (!this->isSmall() && RHS.isSmall()) {
230     assert(RHS.CurArray == RHS.SmallArray);
231     std::copy(RHS.CurArray, RHS.CurArray + RHS.NumNonEmpty, this->SmallArray);
232     std::swap(RHS.CurArraySize, this->CurArraySize);
233     std::swap(this->NumNonEmpty, RHS.NumNonEmpty);
234     std::swap(this->NumTombstones, RHS.NumTombstones);
235     RHS.CurArray = this->CurArray;
236     this->CurArray = this->SmallArray;
237     return;
238   }
239 
240   // If only LHS is small, copy the small elements into RHS and move the pointer
241   // from RHS to LHS.
242   if (this->isSmall() && !RHS.isSmall()) {
243     assert(this->CurArray == this->SmallArray);
244     std::copy(this->CurArray, this->CurArray + this->NumNonEmpty,
245               RHS.SmallArray);
246     std::swap(RHS.CurArraySize, this->CurArraySize);
247     std::swap(RHS.NumNonEmpty, this->NumNonEmpty);
248     std::swap(RHS.NumTombstones, this->NumTombstones);
249     this->CurArray = RHS.CurArray;
250     RHS.CurArray = RHS.SmallArray;
251     return;
252   }
253 
254   // Both a small, just swap the small elements.
255   assert(this->isSmall() && RHS.isSmall());
256   unsigned MinNonEmpty = std::min(this->NumNonEmpty, RHS.NumNonEmpty);
257   std::swap_ranges(this->SmallArray, this->SmallArray + MinNonEmpty,
258                    RHS.SmallArray);
259   if (this->NumNonEmpty > MinNonEmpty) {
260     std::copy(this->SmallArray + MinNonEmpty,
261               this->SmallArray + this->NumNonEmpty,
262               RHS.SmallArray + MinNonEmpty);
263   } else {
264     std::copy(RHS.SmallArray + MinNonEmpty, RHS.SmallArray + RHS.NumNonEmpty,
265               this->SmallArray + MinNonEmpty);
266   }
267   assert(this->CurArraySize == RHS.CurArraySize);
268   std::swap(this->NumNonEmpty, RHS.NumNonEmpty);
269   std::swap(this->NumTombstones, RHS.NumTombstones);
270 }
271