llvm/lib/Support/FoldingSet.cpp

   1 //===-- Support/FoldingSet.cpp - Uniquing Hash Set --------------*- C++ -*-===//
   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 a hash set that can be used to remove duplication of
  10 // nodes in a graph.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/ADT/FoldingSet.h"
  15 #include "llvm/ADT/Hashing.h"
  16 #include "llvm/ADT/StringRef.h"
  17 #include "llvm/Support/Allocator.h"
  18 #include "llvm/Support/ErrorHandling.h"
  19 #include "llvm/Support/Host.h"
  20 #include "llvm/Support/MathExtras.h"
  21 #include <cassert>
  22 #include <cstring>
  23 using namespace llvm;
  24
  25 //===----------------------------------------------------------------------===//
  26 // FoldingSetNodeIDRef Implementation
  27
  28 /// ComputeHash - Compute a strong hash value for this FoldingSetNodeIDRef,
  29 /// used to lookup the node in the FoldingSetBase.
  30 unsigned FoldingSetNodeIDRef::ComputeHash() const {
  31   return static_cast<unsigned>(hash_combine_range(Data, Data+Size));
  32 }
  33
  34 bool FoldingSetNodeIDRef::operator==(FoldingSetNodeIDRef RHS) const {
  35   if (Size != RHS.Size) return false;
  36   return memcmp(Data, RHS.Data, Size*sizeof(*Data)) == 0;
  37 }
  38
  39 /// Used to compare the "ordering" of two nodes as defined by the
  40 /// profiled bits and their ordering defined by memcmp().
  41 bool FoldingSetNodeIDRef::operator<(FoldingSetNodeIDRef RHS) const {
  42   if (Size != RHS.Size)
  43     return Size < RHS.Size;
  44   return memcmp(Data, RHS.Data, Size*sizeof(*Data)) < 0;
  45 }
  46
  47 //===----------------------------------------------------------------------===//
  48 // FoldingSetNodeID Implementation
  49
  50 /// Add* - Add various data types to Bit data.
  51 ///
  52 void FoldingSetNodeID::AddPointer(const void *Ptr) {
  53   // Note: this adds pointers to the hash using sizes and endianness that
  54   // depend on the host. It doesn't matter, however, because hashing on
  55   // pointer values is inherently unstable. Nothing should depend on the
  56   // ordering of nodes in the folding set.
  57   static_assert(sizeof(uintptr_t) <= sizeof(unsigned long long),
  58                 "unexpected pointer size");
  59   AddInteger(reinterpret_cast<uintptr_t>(Ptr));
  60 }
  61 void FoldingSetNodeID::AddInteger(signed I) {
  62   Bits.push_back(I);
  63 }
  64 void FoldingSetNodeID::AddInteger(unsigned I) {
  65   Bits.push_back(I);
  66 }
  67 void FoldingSetNodeID::AddInteger(long I) {
  68   AddInteger((unsigned long)I);
  69 }
  70 void FoldingSetNodeID::AddInteger(unsigned long I) {
  71   if (sizeof(long) == sizeof(int))
  72     AddInteger(unsigned(I));
  73   else if (sizeof(long) == sizeof(long long)) {
  74     AddInteger((unsigned long long)I);
  75   } else {
  76     llvm_unreachable("unexpected sizeof(long)");
  77   }
  78 }
  79 void FoldingSetNodeID::AddInteger(long long I) {
  80   AddInteger((unsigned long long)I);
  81 }
  82 void FoldingSetNodeID::AddInteger(unsigned long long I) {
  83   AddInteger(unsigned(I));
  84   AddInteger(unsigned(I >> 32));
  85 }
  86
  87 void FoldingSetNodeID::AddString(StringRef String) {
  88   unsigned Size =  String.size();
  89
  90   unsigned NumInserts = 1 + divideCeil(Size, 4);
  91   Bits.reserve(Bits.size() + NumInserts);
  92
  93   Bits.push_back(Size);
  94   if (!Size) return;
  95
  96   unsigned Units = Size / 4;
  97   unsigned Pos = 0;
  98   const unsigned *Base = (const unsigned*) String.data();
  99
 100   // If the string is aligned do a bulk transfer.
 101   if (!((intptr_t)Base & 3)) {
 102     Bits.append(Base, Base + Units);
 103     Pos = (Units + 1) * 4;
 104   } else {
 105     // Otherwise do it the hard way.
 106     // To be compatible with above bulk transfer, we need to take endianness
 107     // into account.
 108     static_assert(sys::IsBigEndianHost || sys::IsLittleEndianHost,
 109                   "Unexpected host endianness");
 110     if (sys::IsBigEndianHost) {
 111       for (Pos += 4; Pos <= Size; Pos += 4) {
 112         unsigned V = ((unsigned char)String[Pos - 4] << 24) |
 113                      ((unsigned char)String[Pos - 3] << 16) |
 114                      ((unsigned char)String[Pos - 2] << 8) |
 115                       (unsigned char)String[Pos - 1];
 116         Bits.push_back(V);
 117       }
 118     } else {  // Little-endian host
 119       for (Pos += 4; Pos <= Size; Pos += 4) {
 120         unsigned V = ((unsigned char)String[Pos - 1] << 24) |
 121                      ((unsigned char)String[Pos - 2] << 16) |
 122                      ((unsigned char)String[Pos - 3] << 8) |
 123                       (unsigned char)String[Pos - 4];
 124         Bits.push_back(V);
 125       }
 126     }
 127   }
 128
 129   // With the leftover bits.
 130   unsigned V = 0;
 131   // Pos will have overshot size by 4 - #bytes left over.
 132   // No need to take endianness into account here - this is always executed.
 133   switch (Pos - Size) {
 134   case 1: V = (V << 8) | (unsigned char)String[Size - 3]; LLVM_FALLTHROUGH;
 135   case 2: V = (V << 8) | (unsigned char)String[Size - 2]; LLVM_FALLTHROUGH;
 136   case 3: V = (V << 8) | (unsigned char)String[Size - 1]; break;
 137   default: return; // Nothing left.
 138   }
 139
 140   Bits.push_back(V);
 141 }
 142
 143 // AddNodeID - Adds the Bit data of another ID to *this.
 144 void FoldingSetNodeID::AddNodeID(const FoldingSetNodeID &ID) {
 145   Bits.append(ID.Bits.begin(), ID.Bits.end());
 146 }
 147
 148 /// ComputeHash - Compute a strong hash value for this FoldingSetNodeID, used to
 149 /// lookup the node in the FoldingSetBase.
 150 unsigned FoldingSetNodeID::ComputeHash() const {
 151   return FoldingSetNodeIDRef(Bits.data(), Bits.size()).ComputeHash();
 152 }
 153
 154 /// operator== - Used to compare two nodes to each other.
 155 ///
 156 bool FoldingSetNodeID::operator==(const FoldingSetNodeID &RHS) const {
 157   return *this == FoldingSetNodeIDRef(RHS.Bits.data(), RHS.Bits.size());
 158 }
 159
 160 /// operator== - Used to compare two nodes to each other.
 161 ///
 162 bool FoldingSetNodeID::operator==(FoldingSetNodeIDRef RHS) const {
 163   return FoldingSetNodeIDRef(Bits.data(), Bits.size()) == RHS;
 164 }
 165
 166 /// Used to compare the "ordering" of two nodes as defined by the
 167 /// profiled bits and their ordering defined by memcmp().
 168 bool FoldingSetNodeID::operator<(const FoldingSetNodeID &RHS) const {
 169   return *this < FoldingSetNodeIDRef(RHS.Bits.data(), RHS.Bits.size());
 170 }
 171
 172 bool FoldingSetNodeID::operator<(FoldingSetNodeIDRef RHS) const {
 173   return FoldingSetNodeIDRef(Bits.data(), Bits.size()) < RHS;
 174 }
 175
 176 /// Intern - Copy this node's data to a memory region allocated from the
 177 /// given allocator and return a FoldingSetNodeIDRef describing the
 178 /// interned data.
 179 FoldingSetNodeIDRef
 180 FoldingSetNodeID::Intern(BumpPtrAllocator &Allocator) const {
 181   unsigned *New = Allocator.Allocate<unsigned>(Bits.size());
 182   std::uninitialized_copy(Bits.begin(), Bits.end(), New);
 183   return FoldingSetNodeIDRef(New, Bits.size());
 184 }
 185
 186 //===----------------------------------------------------------------------===//
 187 /// Helper functions for FoldingSetBase.
 188
 189 /// GetNextPtr - In order to save space, each bucket is a
 190 /// singly-linked-list. In order to make deletion more efficient, we make
 191 /// the list circular, so we can delete a node without computing its hash.
 192 /// The problem with this is that the start of the hash buckets are not
 193 /// Nodes.  If NextInBucketPtr is a bucket pointer, this method returns null:
 194 /// use GetBucketPtr when this happens.
 195 static FoldingSetBase::Node *GetNextPtr(void *NextInBucketPtr) {
 196   // The low bit is set if this is the pointer back to the bucket.
 197   if (reinterpret_cast<intptr_t>(NextInBucketPtr) & 1)
 198     return nullptr;
 199
 200   return static_cast<FoldingSetBase::Node*>(NextInBucketPtr);
 201 }
 202
 203
 204 /// testing.
 205 static void **GetBucketPtr(void *NextInBucketPtr) {
 206   intptr_t Ptr = reinterpret_cast<intptr_t>(NextInBucketPtr);
 207   assert((Ptr & 1) && "Not a bucket pointer");
 208   return reinterpret_cast<void**>(Ptr & ~intptr_t(1));
 209 }
 210
 211 /// GetBucketFor - Hash the specified node ID and return the hash bucket for
 212 /// the specified ID.
 213 static void **GetBucketFor(unsigned Hash, void **Buckets, unsigned NumBuckets) {
 214   // NumBuckets is always a power of 2.
 215   unsigned BucketNum = Hash & (NumBuckets-1);
 216   return Buckets + BucketNum;
 217 }
 218
 219 /// AllocateBuckets - Allocated initialized bucket memory.
 220 static void **AllocateBuckets(unsigned NumBuckets) {
 221   void **Buckets = static_cast<void**>(safe_calloc(NumBuckets + 1,
 222                                                    sizeof(void*)));
 223   // Set the very last bucket to be a non-null "pointer".
 224   Buckets[NumBuckets] = reinterpret_cast<void*>(-1);
 225   return Buckets;
 226 }
 227
 228 //===----------------------------------------------------------------------===//
 229 // FoldingSetBase Implementation
 230
 231 FoldingSetBase::FoldingSetBase(unsigned Log2InitSize) {
 232   assert(5 < Log2InitSize && Log2InitSize < 32 &&
 233          "Initial hash table size out of range");
 234   NumBuckets = 1 << Log2InitSize;
 235   Buckets = AllocateBuckets(NumBuckets);
 236   NumNodes = 0;
 237 }
 238
 239 FoldingSetBase::FoldingSetBase(FoldingSetBase &&Arg)
 240     : Buckets(Arg.Buckets), NumBuckets(Arg.NumBuckets), NumNodes(Arg.NumNodes) {
 241   Arg.Buckets = nullptr;
 242   Arg.NumBuckets = 0;
 243   Arg.NumNodes = 0;
 244 }
 245
 246 FoldingSetBase &FoldingSetBase::operator=(FoldingSetBase &&RHS) {
 247   free(Buckets); // This may be null if the set is in a moved-from state.
 248   Buckets = RHS.Buckets;
 249   NumBuckets = RHS.NumBuckets;
 250   NumNodes = RHS.NumNodes;
 251   RHS.Buckets = nullptr;
 252   RHS.NumBuckets = 0;
 253   RHS.NumNodes = 0;
 254   return *this;
 255 }
 256
 257 FoldingSetBase::~FoldingSetBase() {
 258   free(Buckets);
 259 }
 260
 261 void FoldingSetBase::clear() {
 262   // Set all but the last bucket to null pointers.
 263   memset(Buckets, 0, NumBuckets*sizeof(void*));
 264
 265   // Set the very last bucket to be a non-null "pointer".
 266   Buckets[NumBuckets] = reinterpret_cast<void*>(-1);
 267
 268   // Reset the node count to zero.
 269   NumNodes = 0;
 270 }
 271
 272 void FoldingSetBase::GrowBucketCount(unsigned NewBucketCount,
 273                                      const FoldingSetInfo &Info) {
 274   assert((NewBucketCount > NumBuckets) &&
 275          "Can't shrink a folding set with GrowBucketCount");
 276   assert(isPowerOf2_32(NewBucketCount) && "Bad bucket count!");
 277   void **OldBuckets = Buckets;
 278   unsigned OldNumBuckets = NumBuckets;
 279
 280   // Clear out new buckets.
 281   Buckets = AllocateBuckets(NewBucketCount);
 282   // Set NumBuckets only if allocation of new buckets was successful.
 283   NumBuckets = NewBucketCount;
 284   NumNodes = 0;
 285
 286   // Walk the old buckets, rehashing nodes into their new place.
 287   FoldingSetNodeID TempID;
 288   for (unsigned i = 0; i != OldNumBuckets; ++i) {
 289     void *Probe = OldBuckets[i];
 290     if (!Probe) continue;
 291     while (Node *NodeInBucket = GetNextPtr(Probe)) {
 292       // Figure out the next link, remove NodeInBucket from the old link.
 293       Probe = NodeInBucket->getNextInBucket();
 294       NodeInBucket->SetNextInBucket(nullptr);
 295
 296       // Insert the node into the new bucket, after recomputing the hash.
 297       InsertNode(NodeInBucket,
 298                  GetBucketFor(Info.ComputeNodeHash(this, NodeInBucket, TempID),
 299                               Buckets, NumBuckets),
 300                  Info);
 301       TempID.clear();
 302     }
 303   }
 304
 305   free(OldBuckets);
 306 }
 307
 308 /// GrowHashTable - Double the size of the hash table and rehash everything.
 309 ///
 310 void FoldingSetBase::GrowHashTable(const FoldingSetInfo &Info) {
 311   GrowBucketCount(NumBuckets * 2, Info);
 312 }
 313
 314 void FoldingSetBase::reserve(unsigned EltCount, const FoldingSetInfo &Info) {
 315   // This will give us somewhere between EltCount / 2 and
 316   // EltCount buckets.  This puts us in the load factor
 317   // range of 1.0 - 2.0.
 318   if(EltCount < capacity())
 319     return;
 320   GrowBucketCount(PowerOf2Floor(EltCount), Info);
 321 }
 322
 323 /// FindNodeOrInsertPos - Look up the node specified by ID.  If it exists,
 324 /// return it.  If not, return the insertion token that will make insertion
 325 /// faster.
 326 FoldingSetBase::Node *FoldingSetBase::FindNodeOrInsertPos(
 327     const FoldingSetNodeID &ID, void *&InsertPos, const FoldingSetInfo &Info) {
 328   unsigned IDHash = ID.ComputeHash();
 329   void **Bucket = GetBucketFor(IDHash, Buckets, NumBuckets);
 330   void *Probe = *Bucket;
 331
 332   InsertPos = nullptr;
 333
 334   FoldingSetNodeID TempID;
 335   while (Node *NodeInBucket = GetNextPtr(Probe)) {
 336     if (Info.NodeEquals(this, NodeInBucket, ID, IDHash, TempID))
 337       return NodeInBucket;
 338     TempID.clear();
 339
 340     Probe = NodeInBucket->getNextInBucket();
 341   }
 342
 343   // Didn't find the node, return null with the bucket as the InsertPos.
 344   InsertPos = Bucket;
 345   return nullptr;
 346 }
 347
 348 /// InsertNode - Insert the specified node into the folding set, knowing that it
 349 /// is not already in the map.  InsertPos must be obtained from
 350 /// FindNodeOrInsertPos.
 351 void FoldingSetBase::InsertNode(Node *N, void *InsertPos,
 352                                 const FoldingSetInfo &Info) {
 353   assert(!N->getNextInBucket());
 354   // Do we need to grow the hashtable?
 355   if (NumNodes+1 > capacity()) {
 356     GrowHashTable(Info);
 357     FoldingSetNodeID TempID;
 358     InsertPos = GetBucketFor(Info.ComputeNodeHash(this, N, TempID), Buckets,
 359                              NumBuckets);
 360   }
 361
 362   ++NumNodes;
 363
 364   /// The insert position is actually a bucket pointer.
 365   void **Bucket = static_cast<void**>(InsertPos);
 366
 367   void *Next = *Bucket;
 368
 369   // If this is the first insertion into this bucket, its next pointer will be
 370   // null.  Pretend as if it pointed to itself, setting the low bit to indicate
 371   // that it is a pointer to the bucket.
 372   if (!Next)
 373     Next = reinterpret_cast<void*>(reinterpret_cast<intptr_t>(Bucket)|1);
 374
 375   // Set the node's next pointer, and make the bucket point to the node.
 376   N->SetNextInBucket(Next);
 377   *Bucket = N;
 378 }
 379
 380 /// RemoveNode - Remove a node from the folding set, returning true if one was
 381 /// removed or false if the node was not in the folding set.
 382 bool FoldingSetBase::RemoveNode(Node *N) {
 383   // Because each bucket is a circular list, we don't need to compute N's hash
 384   // to remove it.
 385   void *Ptr = N->getNextInBucket();
 386   if (!Ptr) return false;  // Not in folding set.
 387
 388   --NumNodes;
 389   N->SetNextInBucket(nullptr);
 390
 391   // Remember what N originally pointed to, either a bucket or another node.
 392   void *NodeNextPtr = Ptr;
 393
 394   // Chase around the list until we find the node (or bucket) which points to N.
 395   while (true) {
 396     if (Node *NodeInBucket = GetNextPtr(Ptr)) {
 397       // Advance pointer.
 398       Ptr = NodeInBucket->getNextInBucket();
 399
 400       // We found a node that points to N, change it to point to N's next node,
 401       // removing N from the list.
 402       if (Ptr == N) {
 403         NodeInBucket->SetNextInBucket(NodeNextPtr);
 404         return true;
 405       }
 406     } else {
 407       void **Bucket = GetBucketPtr(Ptr);
 408       Ptr = *Bucket;
 409
 410       // If we found that the bucket points to N, update the bucket to point to
 411       // whatever is next.
 412       if (Ptr == N) {
 413         *Bucket = NodeNextPtr;
 414         return true;
 415       }
 416     }
 417   }
 418 }
 419
 420 /// GetOrInsertNode - If there is an existing simple Node exactly
 421 /// equal to the specified node, return it.  Otherwise, insert 'N' and it
 422 /// instead.
 423 FoldingSetBase::Node *
 424 FoldingSetBase::GetOrInsertNode(FoldingSetBase::Node *N,
 425                                 const FoldingSetInfo &Info) {
 426   FoldingSetNodeID ID;
 427   Info.GetNodeProfile(this, N, ID);
 428   void *IP;
 429   if (Node *E = FindNodeOrInsertPos(ID, IP, Info))
 430     return E;
 431   InsertNode(N, IP, Info);
 432   return N;
 433 }
 434
 435 //===----------------------------------------------------------------------===//
 436 // FoldingSetIteratorImpl Implementation
 437
 438 FoldingSetIteratorImpl::FoldingSetIteratorImpl(void **Bucket) {
 439   // Skip to the first non-null non-self-cycle bucket.
 440   while (*Bucket != reinterpret_cast<void*>(-1) &&
 441          (!*Bucket || !GetNextPtr(*Bucket)))
 442     ++Bucket;
 443
 444   NodePtr = static_cast<FoldingSetNode*>(*Bucket);
 445 }
 446
 447 void FoldingSetIteratorImpl::advance() {
 448   // If there is another link within this bucket, go to it.
 449   void *Probe = NodePtr->getNextInBucket();
 450
 451   if (FoldingSetNode *NextNodeInBucket = GetNextPtr(Probe))
 452     NodePtr = NextNodeInBucket;
 453   else {
 454     // Otherwise, this is the last link in this bucket.
 455     void **Bucket = GetBucketPtr(Probe);
 456
 457     // Skip to the next non-null non-self-cycle bucket.
 458     do {
 459       ++Bucket;
 460     } while (*Bucket != reinterpret_cast<void*>(-1) &&
 461              (!*Bucket || !GetNextPtr(*Bucket)));
 462
 463     NodePtr = static_cast<FoldingSetNode*>(*Bucket);
 464   }
 465 }
 466
 467 //===----------------------------------------------------------------------===//
 468 // FoldingSetBucketIteratorImpl Implementation
 469
 470 FoldingSetBucketIteratorImpl::FoldingSetBucketIteratorImpl(void **Bucket) {
 471   Ptr = (!*Bucket || !GetNextPtr(*Bucket)) ? (void*) Bucket : *Bucket;
 472 }