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/MemAlloc.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::doFind(const void *Ptr) const { 66 unsigned BucketNo = 67 DenseMapInfo<void *>::getHashValue(Ptr) & (CurArraySize - 1); 68 unsigned ProbeAmt = 1; 69 while (true) { 70 const void *const *Bucket = CurArray + BucketNo; 71 if (LLVM_LIKELY(*Bucket == Ptr)) 72 return Bucket; 73 if (LLVM_LIKELY(*Bucket == getEmptyMarker())) 74 return nullptr; 75 76 // Otherwise, it's a hash collision or a tombstone, continue quadratic 77 // probing. 78 BucketNo += ProbeAmt++; 79 BucketNo &= CurArraySize - 1; 80 } 81 } 82 83 const void *const *SmallPtrSetImplBase::FindBucketFor(const void *Ptr) const { 84 unsigned Bucket = DenseMapInfo<void *>::getHashValue(Ptr) & (CurArraySize-1); 85 unsigned ArraySize = CurArraySize; 86 unsigned ProbeAmt = 1; 87 const void *const *Array = CurArray; 88 const void *const *Tombstone = nullptr; 89 while (true) { 90 // If we found an empty bucket, the pointer doesn't exist in the set. 91 // Return a tombstone if we've seen one so far, or the empty bucket if 92 // not. 93 if (LLVM_LIKELY(Array[Bucket] == getEmptyMarker())) 94 return Tombstone ? Tombstone : Array+Bucket; 95 96 // Found Ptr's bucket? 97 if (LLVM_LIKELY(Array[Bucket] == Ptr)) 98 return Array+Bucket; 99 100 // If this is a tombstone, remember it. If Ptr ends up not in the set, we 101 // prefer to return it than something that would require more probing. 102 if (Array[Bucket] == getTombstoneMarker() && !Tombstone) 103 Tombstone = Array+Bucket; // Remember the first tombstone found. 104 105 // It's a hash collision or a tombstone. Reprobe. 106 Bucket = (Bucket + ProbeAmt++) & (ArraySize-1); 107 } 108 } 109 110 /// Grow - Allocate a larger backing store for the buckets and move it over. 111 /// 112 void SmallPtrSetImplBase::Grow(unsigned NewSize) { 113 const void **OldBuckets = CurArray; 114 const void **OldEnd = EndPointer(); 115 bool WasSmall = isSmall(); 116 117 // Install the new array. Clear all the buckets to empty. 118 const void **NewBuckets = (const void**) safe_malloc(sizeof(void*) * NewSize); 119 120 // Reset member only if memory was allocated successfully 121 CurArray = NewBuckets; 122 CurArraySize = NewSize; 123 memset(CurArray, -1, NewSize*sizeof(void*)); 124 125 // Copy over all valid entries. 126 for (const void **BucketPtr = OldBuckets; BucketPtr != OldEnd; ++BucketPtr) { 127 // Copy over the element if it is valid. 128 const void *Elt = *BucketPtr; 129 if (Elt != getTombstoneMarker() && Elt != getEmptyMarker()) 130 *const_cast<void**>(FindBucketFor(Elt)) = const_cast<void*>(Elt); 131 } 132 133 if (!WasSmall) 134 free(OldBuckets); 135 NumNonEmpty -= NumTombstones; 136 NumTombstones = 0; 137 IsSmall = false; 138 } 139 140 SmallPtrSetImplBase::SmallPtrSetImplBase(const void **SmallStorage, 141 const SmallPtrSetImplBase &that) { 142 IsSmall = that.isSmall(); 143 if (IsSmall) { 144 // If we're becoming small, prepare to insert into our stack space 145 CurArray = SmallStorage; 146 } else { 147 // Otherwise, allocate new heap space (unless we were the same size) 148 CurArray = (const void**)safe_malloc(sizeof(void*) * that.CurArraySize); 149 } 150 151 // Copy over the that array. 152 copyHelper(that); 153 } 154 155 SmallPtrSetImplBase::SmallPtrSetImplBase(const void **SmallStorage, 156 unsigned SmallSize, 157 const void **RHSSmallStorage, 158 SmallPtrSetImplBase &&that) { 159 moveHelper(SmallStorage, SmallSize, RHSSmallStorage, std::move(that)); 160 } 161 162 void SmallPtrSetImplBase::copyFrom(const void **SmallStorage, 163 const SmallPtrSetImplBase &RHS) { 164 assert(&RHS != this && "Self-copy should be handled by the caller."); 165 166 if (isSmall() && RHS.isSmall()) 167 assert(CurArraySize == RHS.CurArraySize && 168 "Cannot assign sets with different small sizes"); 169 170 // If we're becoming small, prepare to insert into our stack space 171 if (RHS.isSmall()) { 172 if (!isSmall()) 173 free(CurArray); 174 CurArray = SmallStorage; 175 IsSmall = true; 176 // Otherwise, allocate new heap space (unless we were the same size) 177 } else if (CurArraySize != RHS.CurArraySize) { 178 if (isSmall()) 179 CurArray = (const void**)safe_malloc(sizeof(void*) * RHS.CurArraySize); 180 else { 181 const void **T = (const void**)safe_realloc(CurArray, 182 sizeof(void*) * RHS.CurArraySize); 183 CurArray = T; 184 } 185 IsSmall = false; 186 } 187 188 copyHelper(RHS); 189 } 190 191 void SmallPtrSetImplBase::copyHelper(const SmallPtrSetImplBase &RHS) { 192 // Copy over the new array size 193 CurArraySize = RHS.CurArraySize; 194 195 // Copy over the contents from the other set 196 std::copy(RHS.CurArray, RHS.EndPointer(), CurArray); 197 198 NumNonEmpty = RHS.NumNonEmpty; 199 NumTombstones = RHS.NumTombstones; 200 } 201 202 void SmallPtrSetImplBase::moveFrom(const void **SmallStorage, 203 unsigned SmallSize, 204 const void **RHSSmallStorage, 205 SmallPtrSetImplBase &&RHS) { 206 if (!isSmall()) 207 free(CurArray); 208 moveHelper(SmallStorage, SmallSize, RHSSmallStorage, std::move(RHS)); 209 } 210 211 void SmallPtrSetImplBase::moveHelper(const void **SmallStorage, 212 unsigned SmallSize, 213 const void **RHSSmallStorage, 214 SmallPtrSetImplBase &&RHS) { 215 assert(&RHS != this && "Self-move should be handled by the caller."); 216 217 if (RHS.isSmall()) { 218 // Copy a small RHS rather than moving. 219 CurArray = SmallStorage; 220 std::copy(RHS.CurArray, RHS.CurArray + RHS.NumNonEmpty, CurArray); 221 } else { 222 CurArray = RHS.CurArray; 223 RHS.CurArray = RHSSmallStorage; 224 } 225 226 // Copy the rest of the trivial members. 227 CurArraySize = RHS.CurArraySize; 228 NumNonEmpty = RHS.NumNonEmpty; 229 NumTombstones = RHS.NumTombstones; 230 IsSmall = RHS.IsSmall; 231 232 // Make the RHS small and empty. 233 RHS.CurArraySize = SmallSize; 234 RHS.NumNonEmpty = 0; 235 RHS.NumTombstones = 0; 236 RHS.IsSmall = true; 237 } 238 239 void SmallPtrSetImplBase::swap(const void **SmallStorage, 240 const void **RHSSmallStorage, 241 SmallPtrSetImplBase &RHS) { 242 if (this == &RHS) return; 243 244 // We can only avoid copying elements if neither set is small. 245 if (!this->isSmall() && !RHS.isSmall()) { 246 std::swap(this->CurArray, RHS.CurArray); 247 std::swap(this->CurArraySize, RHS.CurArraySize); 248 std::swap(this->NumNonEmpty, RHS.NumNonEmpty); 249 std::swap(this->NumTombstones, RHS.NumTombstones); 250 return; 251 } 252 253 // FIXME: From here on we assume that both sets have the same small size. 254 255 // If only RHS is small, copy the small elements into LHS and move the pointer 256 // from LHS to RHS. 257 if (!this->isSmall() && RHS.isSmall()) { 258 std::copy(RHS.CurArray, RHS.CurArray + RHS.NumNonEmpty, SmallStorage); 259 std::swap(RHS.CurArraySize, this->CurArraySize); 260 std::swap(this->NumNonEmpty, RHS.NumNonEmpty); 261 std::swap(this->NumTombstones, RHS.NumTombstones); 262 RHS.CurArray = this->CurArray; 263 RHS.IsSmall = false; 264 this->CurArray = SmallStorage; 265 this->IsSmall = true; 266 return; 267 } 268 269 // If only LHS is small, copy the small elements into RHS and move the pointer 270 // from RHS to LHS. 271 if (this->isSmall() && !RHS.isSmall()) { 272 std::copy(this->CurArray, this->CurArray + this->NumNonEmpty, 273 RHSSmallStorage); 274 std::swap(RHS.CurArraySize, this->CurArraySize); 275 std::swap(RHS.NumNonEmpty, this->NumNonEmpty); 276 std::swap(RHS.NumTombstones, this->NumTombstones); 277 this->CurArray = RHS.CurArray; 278 this->IsSmall = false; 279 RHS.CurArray = RHSSmallStorage; 280 RHS.IsSmall = true; 281 return; 282 } 283 284 // Both a small, just swap the small elements. 285 assert(this->isSmall() && RHS.isSmall()); 286 unsigned MinNonEmpty = std::min(this->NumNonEmpty, RHS.NumNonEmpty); 287 std::swap_ranges(this->CurArray, this->CurArray + MinNonEmpty, RHS.CurArray); 288 if (this->NumNonEmpty > MinNonEmpty) { 289 std::copy(this->CurArray + MinNonEmpty, this->CurArray + this->NumNonEmpty, 290 RHS.CurArray + MinNonEmpty); 291 } else { 292 std::copy(RHS.CurArray + MinNonEmpty, RHS.CurArray + RHS.NumNonEmpty, 293 this->CurArray + MinNonEmpty); 294 } 295 assert(this->CurArraySize == RHS.CurArraySize); 296 std::swap(this->NumNonEmpty, RHS.NumNonEmpty); 297 std::swap(this->NumTombstones, RHS.NumTombstones); 298 } 299