src/llvm/lib/Support/FoldingSet.cpp

   1 //===-- Support/FoldingSet.cpp - Uniquing Hash Set --------------*- C++ -*-===//
   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 a hash set that can be used to remove duplication of
  11 // nodes in a graph.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "llvm/ADT/FoldingSet.h"
  16 #include "llvm/ADT/Hashing.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 FoldingSetImpl.
  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 in inherently unstable.  Nothing  should depend on the
  56   // ordering of nodes in the folding set.
  57   Bits.append(reinterpret_cast<unsigned *>(&Ptr),
  58               reinterpret_cast<unsigned *>(&Ptr+1));
  59 }
  60 void FoldingSetNodeID::AddInteger(signed I) {
  61   Bits.push_back(I);
  62 }
  63 void FoldingSetNodeID::AddInteger(unsigned I) {
  64   Bits.push_back(I);
  65 }
  66 void FoldingSetNodeID::AddInteger(long I) {
  67   AddInteger((unsigned long)I);
  68 }
  69 void FoldingSetNodeID::AddInteger(unsigned long I) {
  70   if (sizeof(long) == sizeof(int))
  71     AddInteger(unsigned(I));
  72   else if (sizeof(long) == sizeof(long long)) {
  73     AddInteger((unsigned long long)I);
  74   } else {
  75     llvm_unreachable("unexpected sizeof(long)");
  76   }
  77 }
  78 void FoldingSetNodeID::AddInteger(long long I) {
  79   AddInteger((unsigned long long)I);
  80 }
  81 void FoldingSetNodeID::AddInteger(unsigned long long I) {
  82   AddInteger(unsigned(I));
  83   if ((uint64_t)(unsigned)I != I)
  84     Bits.push_back(unsigned(I >> 32));
  85 }
  86
  87 void FoldingSetNodeID::AddString(StringRef String) {
  88   unsigned Size =  String.size();
  89   Bits.push_back(Size);
  90   if (!Size) return;
  91
  92   unsigned Units = Size / 4;
  93   unsigned Pos = 0;
  94   const unsigned *Base = (const unsigned*) String.data();
  95
  96   // If the string is aligned do a bulk transfer.
  97   if (!((intptr_t)Base & 3)) {
  98     Bits.append(Base, Base + Units);
  99     Pos = (Units + 1) * 4;
 100   } else {
 101     // Otherwise do it the hard way.
 102     // To be compatible with above bulk transfer, we need to take endianness
 103     // into account.
 104     if (sys::IsBigEndianHost) {
 105       for (Pos += 4; Pos <= Size; Pos += 4) {
 106         unsigned V = ((unsigned char)String[Pos - 4] << 24) |
 107                      ((unsigned char)String[Pos - 3] << 16) |
 108                      ((unsigned char)String[Pos - 2] << 8) |
 109                       (unsigned char)String[Pos - 1];
 110         Bits.push_back(V);
 111       }
 112     } else {
 113       assert(sys::IsLittleEndianHost && "Unexpected host endianness");
 114       for (Pos += 4; Pos <= Size; Pos += 4) {
 115         unsigned V = ((unsigned char)String[Pos - 1] << 24) |
 116                      ((unsigned char)String[Pos - 2] << 16) |
 117                      ((unsigned char)String[Pos - 3] << 8) |
 118                       (unsigned char)String[Pos - 4];
 119         Bits.push_back(V);
 120       }
 121     }
 122   }
 123
 124   // With the leftover bits.
 125   unsigned V = 0;
 126   // Pos will have overshot size by 4 - #bytes left over.
 127   // No need to take endianness into account here - this is always executed.
 128   switch (Pos - Size) {
 129   case 1: V = (V << 8) | (unsigned char)String[Size - 3]; // Fall thru.
 130   case 2: V = (V << 8) | (unsigned char)String[Size - 2]; // Fall thru.
 131   case 3: V = (V << 8) | (unsigned char)String[Size - 1]; break;
 132   default: return; // Nothing left.
 133   }
 134
 135   Bits.push_back(V);
 136 }
 137
 138 // AddNodeID - Adds the Bit data of another ID to *this.
 139 void FoldingSetNodeID::AddNodeID(const FoldingSetNodeID &ID) {
 140   Bits.append(ID.Bits.begin(), ID.Bits.end());
 141 }
 142
 143 /// ComputeHash - Compute a strong hash value for this FoldingSetNodeID, used to
 144 /// lookup the node in the FoldingSetImpl.
 145 unsigned FoldingSetNodeID::ComputeHash() const {
 146   return FoldingSetNodeIDRef(Bits.data(), Bits.size()).ComputeHash();
 147 }
 148
 149 /// operator== - Used to compare two nodes to each other.
 150 ///
 151 bool FoldingSetNodeID::operator==(const FoldingSetNodeID &RHS) const {
 152   return *this == FoldingSetNodeIDRef(RHS.Bits.data(), RHS.Bits.size());
 153 }
 154
 155 /// operator== - Used to compare two nodes to each other.
 156 ///
 157 bool FoldingSetNodeID::operator==(FoldingSetNodeIDRef RHS) const {
 158   return FoldingSetNodeIDRef(Bits.data(), Bits.size()) == RHS;
 159 }
 160
 161 /// Used to compare the "ordering" of two nodes as defined by the
 162 /// profiled bits and their ordering defined by memcmp().
 163 bool FoldingSetNodeID::operator<(const FoldingSetNodeID &RHS) const {
 164   return *this < FoldingSetNodeIDRef(RHS.Bits.data(), RHS.Bits.size());
 165 }
 166
 167 bool FoldingSetNodeID::operator<(FoldingSetNodeIDRef RHS) const {
 168   return FoldingSetNodeIDRef(Bits.data(), Bits.size()) < RHS;
 169 }
 170
 171 /// Intern - Copy this node's data to a memory region allocated from the
 172 /// given allocator and return a FoldingSetNodeIDRef describing the
 173 /// interned data.
 174 FoldingSetNodeIDRef
 175 FoldingSetNodeID::Intern(BumpPtrAllocator &Allocator) const {
 176   unsigned *New = Allocator.Allocate<unsigned>(Bits.size());
 177   std::uninitialized_copy(Bits.begin(), Bits.end(), New);
 178   return FoldingSetNodeIDRef(New, Bits.size());
 179 }
 180
 181 //===----------------------------------------------------------------------===//
 182 /// Helper functions for FoldingSetImpl.
 183
 184 /// GetNextPtr - In order to save space, each bucket is a
 185 /// singly-linked-list. In order to make deletion more efficient, we make
 186 /// the list circular, so we can delete a node without computing its hash.
 187 /// The problem with this is that the start of the hash buckets are not
 188 /// Nodes.  If NextInBucketPtr is a bucket pointer, this method returns null:
 189 /// use GetBucketPtr when this happens.
 190 static FoldingSetImpl::Node *GetNextPtr(void *NextInBucketPtr) {
 191   // The low bit is set if this is the pointer back to the bucket.
 192   if (reinterpret_cast<intptr_t>(NextInBucketPtr) & 1)
 193     return nullptr;
 194
 195   return static_cast<FoldingSetImpl::Node*>(NextInBucketPtr);
 196 }
 197
 198
 199 /// testing.
 200 static void **GetBucketPtr(void *NextInBucketPtr) {
 201   intptr_t Ptr = reinterpret_cast<intptr_t>(NextInBucketPtr);
 202   assert((Ptr & 1) && "Not a bucket pointer");
 203   return reinterpret_cast<void**>(Ptr & ~intptr_t(1));
 204 }
 205
 206 /// GetBucketFor - Hash the specified node ID and return the hash bucket for
 207 /// the specified ID.
 208 static void **GetBucketFor(unsigned Hash, void **Buckets, unsigned NumBuckets) {
 209   // NumBuckets is always a power of 2.
 210   unsigned BucketNum = Hash & (NumBuckets-1);
 211   return Buckets + BucketNum;
 212 }
 213
 214 /// AllocateBuckets - Allocated initialized bucket memory.
 215 static void **AllocateBuckets(unsigned NumBuckets) {
 216   void **Buckets = static_cast<void**>(calloc(NumBuckets+1, sizeof(void*)));
 217   // Set the very last bucket to be a non-null "pointer".
 218   Buckets[NumBuckets] = reinterpret_cast<void*>(-1);
 219   return Buckets;
 220 }
 221
 222 //===----------------------------------------------------------------------===//
 223 // FoldingSetImpl Implementation
 224
 225 FoldingSetImpl::FoldingSetImpl(unsigned Log2InitSize) {
 226   assert(5 < Log2InitSize && Log2InitSize < 32 &&
 227          "Initial hash table size out of range");
 228   NumBuckets = 1 << Log2InitSize;
 229   Buckets = AllocateBuckets(NumBuckets);
 230   NumNodes = 0;
 231 }
 232 FoldingSetImpl::~FoldingSetImpl() {
 233   free(Buckets);
 234 }
 235 void FoldingSetImpl::clear() {
 236   // Set all but the last bucket to null pointers.
 237   memset(Buckets, 0, NumBuckets*sizeof(void*));
 238
 239   // Set the very last bucket to be a non-null "pointer".
 240   Buckets[NumBuckets] = reinterpret_cast<void*>(-1);
 241
 242   // Reset the node count to zero.
 243   NumNodes = 0;
 244 }
 245
 246 /// GrowHashTable - Double the size of the hash table and rehash everything.
 247 ///
 248 void FoldingSetImpl::GrowHashTable() {
 249   void **OldBuckets = Buckets;
 250   unsigned OldNumBuckets = NumBuckets;
 251   NumBuckets <<= 1;
 252
 253   // Clear out new buckets.
 254   Buckets = AllocateBuckets(NumBuckets);
 255   NumNodes = 0;
 256
 257   // Walk the old buckets, rehashing nodes into their new place.
 258   FoldingSetNodeID TempID;
 259   for (unsigned i = 0; i != OldNumBuckets; ++i) {
 260     void *Probe = OldBuckets[i];
 261     if (!Probe) continue;
 262     while (Node *NodeInBucket = GetNextPtr(Probe)) {
 263       // Figure out the next link, remove NodeInBucket from the old link.
 264       Probe = NodeInBucket->getNextInBucket();
 265       NodeInBucket->SetNextInBucket(nullptr);
 266
 267       // Insert the node into the new bucket, after recomputing the hash.
 268       InsertNode(NodeInBucket,
 269                  GetBucketFor(ComputeNodeHash(NodeInBucket, TempID),
 270                               Buckets, NumBuckets));
 271       TempID.clear();
 272     }
 273   }
 274
 275   free(OldBuckets);
 276 }
 277
 278 /// FindNodeOrInsertPos - Look up the node specified by ID.  If it exists,
 279 /// return it.  If not, return the insertion token that will make insertion
 280 /// faster.
 281 FoldingSetImpl::Node
 282 *FoldingSetImpl::FindNodeOrInsertPos(const FoldingSetNodeID &ID,
 283                                      void *&InsertPos) {
 284   unsigned IDHash = ID.ComputeHash();
 285   void **Bucket = GetBucketFor(IDHash, Buckets, NumBuckets);
 286   void *Probe = *Bucket;
 287
 288   InsertPos = nullptr;
 289
 290   FoldingSetNodeID TempID;
 291   while (Node *NodeInBucket = GetNextPtr(Probe)) {
 292     if (NodeEquals(NodeInBucket, ID, IDHash, TempID))
 293       return NodeInBucket;
 294     TempID.clear();
 295
 296     Probe = NodeInBucket->getNextInBucket();
 297   }
 298
 299   // Didn't find the node, return null with the bucket as the InsertPos.
 300   InsertPos = Bucket;
 301   return nullptr;
 302 }
 303
 304 /// InsertNode - Insert the specified node into the folding set, knowing that it
 305 /// is not already in the map.  InsertPos must be obtained from
 306 /// FindNodeOrInsertPos.
 307 void FoldingSetImpl::InsertNode(Node *N, void *InsertPos) {
 308   assert(!N->getNextInBucket());
 309   // Do we need to grow the hashtable?
 310   if (NumNodes+1 > NumBuckets*2) {
 311     GrowHashTable();
 312     FoldingSetNodeID TempID;
 313     InsertPos = GetBucketFor(ComputeNodeHash(N, TempID), Buckets, NumBuckets);
 314   }
 315
 316   ++NumNodes;
 317
 318   /// The insert position is actually a bucket pointer.
 319   void **Bucket = static_cast<void**>(InsertPos);
 320
 321   void *Next = *Bucket;
 322
 323   // If this is the first insertion into this bucket, its next pointer will be
 324   // null.  Pretend as if it pointed to itself, setting the low bit to indicate
 325   // that it is a pointer to the bucket.
 326   if (!Next)
 327     Next = reinterpret_cast<void*>(reinterpret_cast<intptr_t>(Bucket)|1);
 328
 329   // Set the node's next pointer, and make the bucket point to the node.
 330   N->SetNextInBucket(Next);
 331   *Bucket = N;
 332 }
 333
 334 /// RemoveNode - Remove a node from the folding set, returning true if one was
 335 /// removed or false if the node was not in the folding set.
 336 bool FoldingSetImpl::RemoveNode(Node *N) {
 337   // Because each bucket is a circular list, we don't need to compute N's hash
 338   // to remove it.
 339   void *Ptr = N->getNextInBucket();
 340   if (!Ptr) return false;  // Not in folding set.
 341
 342   --NumNodes;
 343   N->SetNextInBucket(nullptr);
 344
 345   // Remember what N originally pointed to, either a bucket or another node.
 346   void *NodeNextPtr = Ptr;
 347
 348   // Chase around the list until we find the node (or bucket) which points to N.
 349   while (true) {
 350     if (Node *NodeInBucket = GetNextPtr(Ptr)) {
 351       // Advance pointer.
 352       Ptr = NodeInBucket->getNextInBucket();
 353
 354       // We found a node that points to N, change it to point to N's next node,
 355       // removing N from the list.
 356       if (Ptr == N) {
 357         NodeInBucket->SetNextInBucket(NodeNextPtr);
 358         return true;
 359       }
 360     } else {
 361       void **Bucket = GetBucketPtr(Ptr);
 362       Ptr = *Bucket;
 363
 364       // If we found that the bucket points to N, update the bucket to point to
 365       // whatever is next.
 366       if (Ptr == N) {
 367         *Bucket = NodeNextPtr;
 368         return true;
 369       }
 370     }
 371   }
 372 }
 373
 374 /// GetOrInsertNode - If there is an existing simple Node exactly
 375 /// equal to the specified node, return it.  Otherwise, insert 'N' and it
 376 /// instead.
 377 FoldingSetImpl::Node *FoldingSetImpl::GetOrInsertNode(FoldingSetImpl::Node *N) {
 378   FoldingSetNodeID ID;
 379   GetNodeProfile(N, ID);
 380   void *IP;
 381   if (Node *E = FindNodeOrInsertPos(ID, IP))
 382     return E;
 383   InsertNode(N, IP);
 384   return N;
 385 }
 386
 387 //===----------------------------------------------------------------------===//
 388 // FoldingSetIteratorImpl Implementation
 389
 390 FoldingSetIteratorImpl::FoldingSetIteratorImpl(void **Bucket) {
 391   // Skip to the first non-null non-self-cycle bucket.
 392   while (*Bucket != reinterpret_cast<void*>(-1) &&
 393          (!*Bucket || !GetNextPtr(*Bucket)))
 394     ++Bucket;
 395
 396   NodePtr = static_cast<FoldingSetNode*>(*Bucket);
 397 }
 398
 399 void FoldingSetIteratorImpl::advance() {
 400   // If there is another link within this bucket, go to it.
 401   void *Probe = NodePtr->getNextInBucket();
 402
 403   if (FoldingSetNode *NextNodeInBucket = GetNextPtr(Probe))
 404     NodePtr = NextNodeInBucket;
 405   else {
 406     // Otherwise, this is the last link in this bucket.
 407     void **Bucket = GetBucketPtr(Probe);
 408
 409     // Skip to the next non-null non-self-cycle bucket.
 410     do {
 411       ++Bucket;
 412     } while (*Bucket != reinterpret_cast<void*>(-1) &&
 413              (!*Bucket || !GetNextPtr(*Bucket)));
 414
 415     NodePtr = static_cast<FoldingSetNode*>(*Bucket);
 416   }
 417 }
 418
 419 //===----------------------------------------------------------------------===//
 420 // FoldingSetBucketIteratorImpl Implementation
 421
 422 FoldingSetBucketIteratorImpl::FoldingSetBucketIteratorImpl(void **Bucket) {
 423   Ptr = (!*Bucket || !GetNextPtr(*Bucket)) ? (void*) Bucket : *Bucket;
 424 }