llvm/lib/Support/SmallPtrSet.cpp

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