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.  This code was originally created by Chris Lattner for use
  12 // with SelectionDAGCSEMap, but was isolated to provide use across the llvm code
  13 // set.
  14 //
  15 //===----------------------------------------------------------------------===//
  16
  17 #include "llvm/ADT/FoldingSet.h"
  18 #include "llvm/Support/Allocator.h"
  19 #include "llvm/Support/ErrorHandling.h"
  20 #include "llvm/Support/MathExtras.h"
  21 #include "llvm/Support/Host.h"
  22 #include <cassert>
  23 #include <cstring>
  24 using namespace llvm;
  25
  26 //===----------------------------------------------------------------------===//
  27 // FoldingSetNodeIDRef Implementation
  28
  29 /// ComputeHash - Compute a strong hash value for this FoldingSetNodeIDRef,
  30 /// used to lookup the node in the FoldingSetImpl.
  31 unsigned FoldingSetNodeIDRef::ComputeHash() const {
  32   // This is adapted from SuperFastHash by Paul Hsieh.
  33   unsigned Hash = static_cast<unsigned>(Size);
  34   for (const unsigned *BP = Data, *E = BP+Size; BP != E; ++BP) {
  35     unsigned Data = *BP;
  36     Hash         += Data & 0xFFFF;
  37     unsigned Tmp  = ((Data >> 16) << 11) ^ Hash;
  38     Hash          = (Hash << 16) ^ Tmp;
  39     Hash         += Hash >> 11;
  40   }
  41
  42   // Force "avalanching" of final 127 bits.
  43   Hash ^= Hash << 3;
  44   Hash += Hash >> 5;
  45   Hash ^= Hash << 4;
  46   Hash += Hash >> 17;
  47   Hash ^= Hash << 25;
  48   Hash += Hash >> 6;
  49   return Hash;
  50 }
  51
  52 bool FoldingSetNodeIDRef::operator==(FoldingSetNodeIDRef RHS) const {
  53   if (Size != RHS.Size) return false;
  54   return memcmp(Data, RHS.Data, Size*sizeof(*Data)) == 0;
  55 }
  56
  57 //===----------------------------------------------------------------------===//
  58 // FoldingSetNodeID Implementation
  59
  60 /// Add* - Add various data types to Bit data.
  61 ///
  62 void FoldingSetNodeID::AddPointer(const void *Ptr) {
  63   // Note: this adds pointers to the hash using sizes and endianness that
  64   // depend on the host.  It doesn't matter however, because hashing on
  65   // pointer values in inherently unstable.  Nothing  should depend on the
  66   // ordering of nodes in the folding set.
  67   intptr_t PtrI = (intptr_t)Ptr;
  68   Bits.push_back(unsigned(PtrI));
  69   if (sizeof(intptr_t) > sizeof(unsigned))
  70     Bits.push_back(unsigned(uint64_t(PtrI) >> 32));
  71 }
  72 void FoldingSetNodeID::AddInteger(signed I) {
  73   Bits.push_back(I);
  74 }
  75 void FoldingSetNodeID::AddInteger(unsigned I) {
  76   Bits.push_back(I);
  77 }
  78 void FoldingSetNodeID::AddInteger(long I) {
  79   AddInteger((unsigned long)I);
  80 }
  81 void FoldingSetNodeID::AddInteger(unsigned long I) {
  82   if (sizeof(long) == sizeof(int))
  83     AddInteger(unsigned(I));
  84   else if (sizeof(long) == sizeof(long long)) {
  85     AddInteger((unsigned long long)I);
  86   } else {
  87     llvm_unreachable("unexpected sizeof(long)");
  88   }
  89 }
  90 void FoldingSetNodeID::AddInteger(long long I) {
  91   AddInteger((unsigned long long)I);
  92 }
  93 void FoldingSetNodeID::AddInteger(unsigned long long I) {
  94   AddInteger(unsigned(I));
  95   if ((uint64_t)(unsigned)I != I)
  96     Bits.push_back(unsigned(I >> 32));
  97 }
  98
  99 void FoldingSetNodeID::AddString(StringRef String) {
 100   unsigned Size =  String.size();
 101   Bits.push_back(Size);
 102   if (!Size) return;
 103
 104   unsigned Units = Size / 4;
 105   unsigned Pos = 0;
 106   const unsigned *Base = (const unsigned*) String.data();
 107
 108   // If the string is aligned do a bulk transfer.
 109   if (!((intptr_t)Base & 3)) {
 110     Bits.append(Base, Base + Units);
 111     Pos = (Units + 1) * 4;
 112   } else {
 113     // Otherwise do it the hard way.
 114     // To be compatible with above bulk transfer, we need to take endianness
 115     // into account.
 116     if (sys::isBigEndianHost()) {
 117       for (Pos += 4; Pos <= Size; Pos += 4) {
 118         unsigned V = ((unsigned char)String[Pos - 4] << 24) |
 119                      ((unsigned char)String[Pos - 3] << 16) |
 120                      ((unsigned char)String[Pos - 2] << 8) |
 121                       (unsigned char)String[Pos - 1];
 122         Bits.push_back(V);
 123       }
 124     } else {
 125       assert(sys::isLittleEndianHost() && "Unexpected host endianness");
 126       for (Pos += 4; Pos <= Size; Pos += 4) {
 127         unsigned V = ((unsigned char)String[Pos - 1] << 24) |
 128                      ((unsigned char)String[Pos - 2] << 16) |
 129                      ((unsigned char)String[Pos - 3] << 8) |
 130                       (unsigned char)String[Pos - 4];
 131         Bits.push_back(V);
 132       }
 133     }
 134   }
 135
 136   // With the leftover bits.
 137   unsigned V = 0;
 138   // Pos will have overshot size by 4 - #bytes left over.
 139   // No need to take endianness into account here - this is always executed.
 140   switch (Pos - Size) {
 141   case 1: V = (V << 8) | (unsigned char)String[Size - 3]; // Fall thru.
 142   case 2: V = (V << 8) | (unsigned char)String[Size - 2]; // Fall thru.
 143   case 3: V = (V << 8) | (unsigned char)String[Size - 1]; break;
 144   default: return; // Nothing left.
 145   }
 146
 147   Bits.push_back(V);
 148 }
 149
 150 // AddNodeID - Adds the Bit data of another ID to *this.
 151 void FoldingSetNodeID::AddNodeID(const FoldingSetNodeID &ID) {
 152   Bits.append(ID.Bits.begin(), ID.Bits.end());
 153 }
 154
 155 /// ComputeHash - Compute a strong hash value for this FoldingSetNodeID, used to
 156 /// lookup the node in the FoldingSetImpl.
 157 unsigned FoldingSetNodeID::ComputeHash() const {
 158   return FoldingSetNodeIDRef(Bits.data(), Bits.size()).ComputeHash();
 159 }
 160
 161 /// operator== - Used to compare two nodes to each other.
 162 ///
 163 bool FoldingSetNodeID::operator==(const FoldingSetNodeID &RHS)const{
 164   return *this == FoldingSetNodeIDRef(RHS.Bits.data(), RHS.Bits.size());
 165 }
 166
 167 /// operator== - Used to compare two nodes to each other.
 168 ///
 169 bool FoldingSetNodeID::operator==(FoldingSetNodeIDRef RHS) const {
 170   return FoldingSetNodeIDRef(Bits.data(), Bits.size()) == RHS;
 171 }
 172
 173 /// Intern - Copy this node's data to a memory region allocated from the
 174 /// given allocator and return a FoldingSetNodeIDRef describing the
 175 /// interned data.
 176 FoldingSetNodeIDRef
 177 FoldingSetNodeID::Intern(BumpPtrAllocator &Allocator) const {
 178   unsigned *New = Allocator.Allocate<unsigned>(Bits.size());
 179   std::uninitialized_copy(Bits.begin(), Bits.end(), New);
 180   return FoldingSetNodeIDRef(New, Bits.size());
 181 }
 182
 183 //===----------------------------------------------------------------------===//
 184 /// Helper functions for FoldingSetImpl.
 185
 186 /// GetNextPtr - In order to save space, each bucket is a
 187 /// singly-linked-list. In order to make deletion more efficient, we make
 188 /// the list circular, so we can delete a node without computing its hash.
 189 /// The problem with this is that the start of the hash buckets are not
 190 /// Nodes.  If NextInBucketPtr is a bucket pointer, this method returns null:
 191 /// use GetBucketPtr when this happens.
 192 static FoldingSetImpl::Node *GetNextPtr(void *NextInBucketPtr) {
 193   // The low bit is set if this is the pointer back to the bucket.
 194   if (reinterpret_cast<intptr_t>(NextInBucketPtr) & 1)
 195     return 0;
 196
 197   return static_cast<FoldingSetImpl::Node*>(NextInBucketPtr);
 198 }
 199
 200
 201 /// testing.
 202 static void **GetBucketPtr(void *NextInBucketPtr) {
 203   intptr_t Ptr = reinterpret_cast<intptr_t>(NextInBucketPtr);
 204   assert((Ptr & 1) && "Not a bucket pointer");
 205   return reinterpret_cast<void**>(Ptr & ~intptr_t(1));
 206 }
 207
 208 /// GetBucketFor - Hash the specified node ID and return the hash bucket for
 209 /// the specified ID.
 210 static void **GetBucketFor(unsigned Hash, void **Buckets, unsigned NumBuckets) {
 211   // NumBuckets is always a power of 2.
 212   unsigned BucketNum = Hash & (NumBuckets-1);
 213   return Buckets + BucketNum;
 214 }
 215
 216 /// AllocateBuckets - Allocated initialized bucket memory.
 217 static void **AllocateBuckets(unsigned NumBuckets) {
 218   void **Buckets = static_cast<void**>(calloc(NumBuckets+1, sizeof(void*)));
 219   // Set the very last bucket to be a non-null "pointer".
 220   Buckets[NumBuckets] = reinterpret_cast<void*>(-1);
 221   return Buckets;
 222 }
 223
 224 //===----------------------------------------------------------------------===//
 225 // FoldingSetImpl Implementation
 226
 227 FoldingSetImpl::FoldingSetImpl(unsigned Log2InitSize) {
 228   assert(5 < Log2InitSize && Log2InitSize < 32 &&
 229          "Initial hash table size out of range");
 230   NumBuckets = 1 << Log2InitSize;
 231   Buckets = AllocateBuckets(NumBuckets);
 232   NumNodes = 0;
 233 }
 234 FoldingSetImpl::~FoldingSetImpl() {
 235   free(Buckets);
 236 }
 237 void FoldingSetImpl::clear() {
 238   // Set all but the last bucket to null pointers.
 239   memset(Buckets, 0, NumBuckets*sizeof(void*));
 240
 241   // Set the very last bucket to be a non-null "pointer".
 242   Buckets[NumBuckets] = reinterpret_cast<void*>(-1);
 243
 244   // Reset the node count to zero.
 245   NumNodes = 0;
 246 }
 247
 248 /// GrowHashTable - Double the size of the hash table and rehash everything.
 249 ///
 250 void FoldingSetImpl::GrowHashTable() {
 251   void **OldBuckets = Buckets;
 252   unsigned OldNumBuckets = NumBuckets;
 253   NumBuckets <<= 1;
 254
 255   // Clear out new buckets.
 256   Buckets = AllocateBuckets(NumBuckets);
 257   NumNodes = 0;
 258
 259   // Walk the old buckets, rehashing nodes into their new place.
 260   FoldingSetNodeID TempID;
 261   for (unsigned i = 0; i != OldNumBuckets; ++i) {
 262     void *Probe = OldBuckets[i];
 263     if (!Probe) continue;
 264     while (Node *NodeInBucket = GetNextPtr(Probe)) {
 265       // Figure out the next link, remove NodeInBucket from the old link.
 266       Probe = NodeInBucket->getNextInBucket();
 267       NodeInBucket->SetNextInBucket(0);
 268
 269       // Insert the node into the new bucket, after recomputing the hash.
 270       InsertNode(NodeInBucket,
 271                  GetBucketFor(ComputeNodeHash(NodeInBucket, TempID),
 272                               Buckets, NumBuckets));
 273       TempID.clear();
 274     }
 275   }
 276
 277   free(OldBuckets);
 278 }
 279
 280 /// FindNodeOrInsertPos - Look up the node specified by ID.  If it exists,
 281 /// return it.  If not, return the insertion token that will make insertion
 282 /// faster.
 283 FoldingSetImpl::Node
 284 *FoldingSetImpl::FindNodeOrInsertPos(const FoldingSetNodeID &ID,
 285                                      void *&InsertPos) {
 286
 287   void **Bucket = GetBucketFor(ID.ComputeHash(), Buckets, NumBuckets);
 288   void *Probe = *Bucket;
 289
 290   InsertPos = 0;
 291
 292   FoldingSetNodeID TempID;
 293   while (Node *NodeInBucket = GetNextPtr(Probe)) {
 294     if (NodeEquals(NodeInBucket, ID, TempID))
 295       return NodeInBucket;
 296     TempID.clear();
 297
 298     Probe = NodeInBucket->getNextInBucket();
 299   }
 300
 301   // Didn't find the node, return null with the bucket as the InsertPos.
 302   InsertPos = Bucket;
 303   return 0;
 304 }
 305
 306 /// InsertNode - Insert the specified node into the folding set, knowing that it
 307 /// is not already in the map.  InsertPos must be obtained from
 308 /// FindNodeOrInsertPos.
 309 void FoldingSetImpl::InsertNode(Node *N, void *InsertPos) {
 310   assert(N->getNextInBucket() == 0);
 311   // Do we need to grow the hashtable?
 312   if (NumNodes+1 > NumBuckets*2) {
 313     GrowHashTable();
 314     FoldingSetNodeID TempID;
 315     InsertPos = GetBucketFor(ComputeNodeHash(N, TempID), Buckets, NumBuckets);
 316   }
 317
 318   ++NumNodes;
 319
 320   /// The insert position is actually a bucket pointer.
 321   void **Bucket = static_cast<void**>(InsertPos);
 322
 323   void *Next = *Bucket;
 324
 325   // If this is the first insertion into this bucket, its next pointer will be
 326   // null.  Pretend as if it pointed to itself, setting the low bit to indicate
 327   // that it is a pointer to the bucket.
 328   if (Next == 0)
 329     Next = reinterpret_cast<void*>(reinterpret_cast<intptr_t>(Bucket)|1);
 330
 331   // Set the node's next pointer, and make the bucket point to the node.
 332   N->SetNextInBucket(Next);
 333   *Bucket = N;
 334 }
 335
 336 /// RemoveNode - Remove a node from the folding set, returning true if one was
 337 /// removed or false if the node was not in the folding set.
 338 bool FoldingSetImpl::RemoveNode(Node *N) {
 339   // Because each bucket is a circular list, we don't need to compute N's hash
 340   // to remove it.
 341   void *Ptr = N->getNextInBucket();
 342   if (Ptr == 0) return false;  // Not in folding set.
 343
 344   --NumNodes;
 345   N->SetNextInBucket(0);
 346
 347   // Remember what N originally pointed to, either a bucket or another node.
 348   void *NodeNextPtr = Ptr;
 349
 350   // Chase around the list until we find the node (or bucket) which points to N.
 351   while (true) {
 352     if (Node *NodeInBucket = GetNextPtr(Ptr)) {
 353       // Advance pointer.
 354       Ptr = NodeInBucket->getNextInBucket();
 355
 356       // We found a node that points to N, change it to point to N's next node,
 357       // removing N from the list.
 358       if (Ptr == N) {
 359         NodeInBucket->SetNextInBucket(NodeNextPtr);
 360         return true;
 361       }
 362     } else {
 363       void **Bucket = GetBucketPtr(Ptr);
 364       Ptr = *Bucket;
 365
 366       // If we found that the bucket points to N, update the bucket to point to
 367       // whatever is next.
 368       if (Ptr == N) {
 369         *Bucket = NodeNextPtr;
 370         return true;
 371       }
 372     }
 373   }
 374 }
 375
 376 /// GetOrInsertNode - If there is an existing simple Node exactly
 377 /// equal to the specified node, return it.  Otherwise, insert 'N' and it
 378 /// instead.
 379 FoldingSetImpl::Node *FoldingSetImpl::GetOrInsertNode(FoldingSetImpl::Node *N) {
 380   FoldingSetNodeID ID;
 381   GetNodeProfile(N, ID);
 382   void *IP;
 383   if (Node *E = FindNodeOrInsertPos(ID, IP))
 384     return E;
 385   InsertNode(N, IP);
 386   return N;
 387 }
 388
 389 //===----------------------------------------------------------------------===//
 390 // FoldingSetIteratorImpl Implementation
 391
 392 FoldingSetIteratorImpl::FoldingSetIteratorImpl(void **Bucket) {
 393   // Skip to the first non-null non-self-cycle bucket.
 394   while (*Bucket != reinterpret_cast<void*>(-1) &&
 395          (*Bucket == 0 || GetNextPtr(*Bucket) == 0))
 396     ++Bucket;
 397
 398   NodePtr = static_cast<FoldingSetNode*>(*Bucket);
 399 }
 400
 401 void FoldingSetIteratorImpl::advance() {
 402   // If there is another link within this bucket, go to it.
 403   void *Probe = NodePtr->getNextInBucket();
 404
 405   if (FoldingSetNode *NextNodeInBucket = GetNextPtr(Probe))
 406     NodePtr = NextNodeInBucket;
 407   else {
 408     // Otherwise, this is the last link in this bucket.
 409     void **Bucket = GetBucketPtr(Probe);
 410
 411     // Skip to the next non-null non-self-cycle bucket.
 412     do {
 413       ++Bucket;
 414     } while (*Bucket != reinterpret_cast<void*>(-1) &&
 415              (*Bucket == 0 || GetNextPtr(*Bucket) == 0));
 416
 417     NodePtr = static_cast<FoldingSetNode*>(*Bucket);
 418   }
 419 }
 420
 421 //===----------------------------------------------------------------------===//
 422 // FoldingSetBucketIteratorImpl Implementation
 423
 424 FoldingSetBucketIteratorImpl::FoldingSetBucketIteratorImpl(void **Bucket) {
 425   Ptr = (*Bucket == 0 || GetNextPtr(*Bucket) == 0) ? (void*) Bucket : *Bucket;
 426 }