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 is 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 static_assert(sys::IsBigEndianHost || sys::IsLittleEndianHost, 105 "Unexpected host endianness"); 106 if (sys::IsBigEndianHost) { 107 for (Pos += 4; Pos <= Size; Pos += 4) { 108 unsigned V = ((unsigned char)String[Pos - 4] << 24) | 109 ((unsigned char)String[Pos - 3] << 16) | 110 ((unsigned char)String[Pos - 2] << 8) | 111 (unsigned char)String[Pos - 1]; 112 Bits.push_back(V); 113 } 114 } else { // Little-endian host 115 for (Pos += 4; Pos <= Size; Pos += 4) { 116 unsigned V = ((unsigned char)String[Pos - 1] << 24) | 117 ((unsigned char)String[Pos - 2] << 16) | 118 ((unsigned char)String[Pos - 3] << 8) | 119 (unsigned char)String[Pos - 4]; 120 Bits.push_back(V); 121 } 122 } 123 } 124 125 // With the leftover bits. 126 unsigned V = 0; 127 // Pos will have overshot size by 4 - #bytes left over. 128 // No need to take endianness into account here - this is always executed. 129 switch (Pos - Size) { 130 case 1: V = (V << 8) | (unsigned char)String[Size - 3]; // Fall thru. 131 case 2: V = (V << 8) | (unsigned char)String[Size - 2]; // Fall thru. 132 case 3: V = (V << 8) | (unsigned char)String[Size - 1]; break; 133 default: return; // Nothing left. 134 } 135 136 Bits.push_back(V); 137 } 138 139 // AddNodeID - Adds the Bit data of another ID to *this. 140 void FoldingSetNodeID::AddNodeID(const FoldingSetNodeID &ID) { 141 Bits.append(ID.Bits.begin(), ID.Bits.end()); 142 } 143 144 /// ComputeHash - Compute a strong hash value for this FoldingSetNodeID, used to 145 /// lookup the node in the FoldingSetImpl. 146 unsigned FoldingSetNodeID::ComputeHash() const { 147 return FoldingSetNodeIDRef(Bits.data(), Bits.size()).ComputeHash(); 148 } 149 150 /// operator== - Used to compare two nodes to each other. 151 /// 152 bool FoldingSetNodeID::operator==(const FoldingSetNodeID &RHS) const { 153 return *this == FoldingSetNodeIDRef(RHS.Bits.data(), RHS.Bits.size()); 154 } 155 156 /// operator== - Used to compare two nodes to each other. 157 /// 158 bool FoldingSetNodeID::operator==(FoldingSetNodeIDRef RHS) const { 159 return FoldingSetNodeIDRef(Bits.data(), Bits.size()) == RHS; 160 } 161 162 /// Used to compare the "ordering" of two nodes as defined by the 163 /// profiled bits and their ordering defined by memcmp(). 164 bool FoldingSetNodeID::operator<(const FoldingSetNodeID &RHS) const { 165 return *this < FoldingSetNodeIDRef(RHS.Bits.data(), RHS.Bits.size()); 166 } 167 168 bool FoldingSetNodeID::operator<(FoldingSetNodeIDRef RHS) const { 169 return FoldingSetNodeIDRef(Bits.data(), Bits.size()) < RHS; 170 } 171 172 /// Intern - Copy this node's data to a memory region allocated from the 173 /// given allocator and return a FoldingSetNodeIDRef describing the 174 /// interned data. 175 FoldingSetNodeIDRef 176 FoldingSetNodeID::Intern(BumpPtrAllocator &Allocator) const { 177 unsigned *New = Allocator.Allocate<unsigned>(Bits.size()); 178 std::uninitialized_copy(Bits.begin(), Bits.end(), New); 179 return FoldingSetNodeIDRef(New, Bits.size()); 180 } 181 182 //===----------------------------------------------------------------------===// 183 /// Helper functions for FoldingSetImpl. 184 185 /// GetNextPtr - In order to save space, each bucket is a 186 /// singly-linked-list. In order to make deletion more efficient, we make 187 /// the list circular, so we can delete a node without computing its hash. 188 /// The problem with this is that the start of the hash buckets are not 189 /// Nodes. If NextInBucketPtr is a bucket pointer, this method returns null: 190 /// use GetBucketPtr when this happens. 191 static FoldingSetImpl::Node *GetNextPtr(void *NextInBucketPtr) { 192 // The low bit is set if this is the pointer back to the bucket. 193 if (reinterpret_cast<intptr_t>(NextInBucketPtr) & 1) 194 return nullptr; 195 196 return static_cast<FoldingSetImpl::Node*>(NextInBucketPtr); 197 } 198 199 200 /// testing. 201 static void **GetBucketPtr(void *NextInBucketPtr) { 202 intptr_t Ptr = reinterpret_cast<intptr_t>(NextInBucketPtr); 203 assert((Ptr & 1) && "Not a bucket pointer"); 204 return reinterpret_cast<void**>(Ptr & ~intptr_t(1)); 205 } 206 207 /// GetBucketFor - Hash the specified node ID and return the hash bucket for 208 /// the specified ID. 209 static void **GetBucketFor(unsigned Hash, void **Buckets, unsigned NumBuckets) { 210 // NumBuckets is always a power of 2. 211 unsigned BucketNum = Hash & (NumBuckets-1); 212 return Buckets + BucketNum; 213 } 214 215 /// AllocateBuckets - Allocated initialized bucket memory. 216 static void **AllocateBuckets(unsigned NumBuckets) { 217 void **Buckets = static_cast<void**>(calloc(NumBuckets+1, sizeof(void*))); 218 // Set the very last bucket to be a non-null "pointer". 219 Buckets[NumBuckets] = reinterpret_cast<void*>(-1); 220 return Buckets; 221 } 222 223 //===----------------------------------------------------------------------===// 224 // FoldingSetImpl Implementation 225 226 void FoldingSetImpl::anchor() {} 227 228 FoldingSetImpl::FoldingSetImpl(unsigned Log2InitSize) { 229 assert(5 < Log2InitSize && Log2InitSize < 32 && 230 "Initial hash table size out of range"); 231 NumBuckets = 1 << Log2InitSize; 232 Buckets = AllocateBuckets(NumBuckets); 233 NumNodes = 0; 234 } 235 FoldingSetImpl::~FoldingSetImpl() { 236 free(Buckets); 237 } 238 void FoldingSetImpl::clear() { 239 // Set all but the last bucket to null pointers. 240 memset(Buckets, 0, NumBuckets*sizeof(void*)); 241 242 // Set the very last bucket to be a non-null "pointer". 243 Buckets[NumBuckets] = reinterpret_cast<void*>(-1); 244 245 // Reset the node count to zero. 246 NumNodes = 0; 247 } 248 249 /// GrowHashTable - Double the size of the hash table and rehash everything. 250 /// 251 void FoldingSetImpl::GrowHashTable() { 252 void **OldBuckets = Buckets; 253 unsigned OldNumBuckets = NumBuckets; 254 NumBuckets <<= 1; 255 256 // Clear out new buckets. 257 Buckets = AllocateBuckets(NumBuckets); 258 NumNodes = 0; 259 260 // Walk the old buckets, rehashing nodes into their new place. 261 FoldingSetNodeID TempID; 262 for (unsigned i = 0; i != OldNumBuckets; ++i) { 263 void *Probe = OldBuckets[i]; 264 if (!Probe) continue; 265 while (Node *NodeInBucket = GetNextPtr(Probe)) { 266 // Figure out the next link, remove NodeInBucket from the old link. 267 Probe = NodeInBucket->getNextInBucket(); 268 NodeInBucket->SetNextInBucket(nullptr); 269 270 // Insert the node into the new bucket, after recomputing the hash. 271 InsertNode(NodeInBucket, 272 GetBucketFor(ComputeNodeHash(NodeInBucket, TempID), 273 Buckets, NumBuckets)); 274 TempID.clear(); 275 } 276 } 277 278 free(OldBuckets); 279 } 280 281 /// FindNodeOrInsertPos - Look up the node specified by ID. If it exists, 282 /// return it. If not, return the insertion token that will make insertion 283 /// faster. 284 FoldingSetImpl::Node 285 *FoldingSetImpl::FindNodeOrInsertPos(const FoldingSetNodeID &ID, 286 void *&InsertPos) { 287 unsigned IDHash = ID.ComputeHash(); 288 void **Bucket = GetBucketFor(IDHash, Buckets, NumBuckets); 289 void *Probe = *Bucket; 290 291 InsertPos = nullptr; 292 293 FoldingSetNodeID TempID; 294 while (Node *NodeInBucket = GetNextPtr(Probe)) { 295 if (NodeEquals(NodeInBucket, ID, IDHash, TempID)) 296 return NodeInBucket; 297 TempID.clear(); 298 299 Probe = NodeInBucket->getNextInBucket(); 300 } 301 302 // Didn't find the node, return null with the bucket as the InsertPos. 303 InsertPos = Bucket; 304 return nullptr; 305 } 306 307 /// InsertNode - Insert the specified node into the folding set, knowing that it 308 /// is not already in the map. InsertPos must be obtained from 309 /// FindNodeOrInsertPos. 310 void FoldingSetImpl::InsertNode(Node *N, void *InsertPos) { 311 assert(!N->getNextInBucket()); 312 // Do we need to grow the hashtable? 313 if (NumNodes+1 > NumBuckets*2) { 314 GrowHashTable(); 315 FoldingSetNodeID TempID; 316 InsertPos = GetBucketFor(ComputeNodeHash(N, TempID), Buckets, NumBuckets); 317 } 318 319 ++NumNodes; 320 321 /// The insert position is actually a bucket pointer. 322 void **Bucket = static_cast<void**>(InsertPos); 323 324 void *Next = *Bucket; 325 326 // If this is the first insertion into this bucket, its next pointer will be 327 // null. Pretend as if it pointed to itself, setting the low bit to indicate 328 // that it is a pointer to the bucket. 329 if (!Next) 330 Next = reinterpret_cast<void*>(reinterpret_cast<intptr_t>(Bucket)|1); 331 332 // Set the node's next pointer, and make the bucket point to the node. 333 N->SetNextInBucket(Next); 334 *Bucket = N; 335 } 336 337 /// RemoveNode - Remove a node from the folding set, returning true if one was 338 /// removed or false if the node was not in the folding set. 339 bool FoldingSetImpl::RemoveNode(Node *N) { 340 // Because each bucket is a circular list, we don't need to compute N's hash 341 // to remove it. 342 void *Ptr = N->getNextInBucket(); 343 if (!Ptr) return false; // Not in folding set. 344 345 --NumNodes; 346 N->SetNextInBucket(nullptr); 347 348 // Remember what N originally pointed to, either a bucket or another node. 349 void *NodeNextPtr = Ptr; 350 351 // Chase around the list until we find the node (or bucket) which points to N. 352 while (true) { 353 if (Node *NodeInBucket = GetNextPtr(Ptr)) { 354 // Advance pointer. 355 Ptr = NodeInBucket->getNextInBucket(); 356 357 // We found a node that points to N, change it to point to N's next node, 358 // removing N from the list. 359 if (Ptr == N) { 360 NodeInBucket->SetNextInBucket(NodeNextPtr); 361 return true; 362 } 363 } else { 364 void **Bucket = GetBucketPtr(Ptr); 365 Ptr = *Bucket; 366 367 // If we found that the bucket points to N, update the bucket to point to 368 // whatever is next. 369 if (Ptr == N) { 370 *Bucket = NodeNextPtr; 371 return true; 372 } 373 } 374 } 375 } 376 377 /// GetOrInsertNode - If there is an existing simple Node exactly 378 /// equal to the specified node, return it. Otherwise, insert 'N' and it 379 /// instead. 380 FoldingSetImpl::Node *FoldingSetImpl::GetOrInsertNode(FoldingSetImpl::Node *N) { 381 FoldingSetNodeID ID; 382 GetNodeProfile(N, ID); 383 void *IP; 384 if (Node *E = FindNodeOrInsertPos(ID, IP)) 385 return E; 386 InsertNode(N, IP); 387 return N; 388 } 389 390 //===----------------------------------------------------------------------===// 391 // FoldingSetIteratorImpl Implementation 392 393 FoldingSetIteratorImpl::FoldingSetIteratorImpl(void **Bucket) { 394 // Skip to the first non-null non-self-cycle bucket. 395 while (*Bucket != reinterpret_cast<void*>(-1) && 396 (!*Bucket || !GetNextPtr(*Bucket))) 397 ++Bucket; 398 399 NodePtr = static_cast<FoldingSetNode*>(*Bucket); 400 } 401 402 void FoldingSetIteratorImpl::advance() { 403 // If there is another link within this bucket, go to it. 404 void *Probe = NodePtr->getNextInBucket(); 405 406 if (FoldingSetNode *NextNodeInBucket = GetNextPtr(Probe)) 407 NodePtr = NextNodeInBucket; 408 else { 409 // Otherwise, this is the last link in this bucket. 410 void **Bucket = GetBucketPtr(Probe); 411 412 // Skip to the next non-null non-self-cycle bucket. 413 do { 414 ++Bucket; 415 } while (*Bucket != reinterpret_cast<void*>(-1) && 416 (!*Bucket || !GetNextPtr(*Bucket))); 417 418 NodePtr = static_cast<FoldingSetNode*>(*Bucket); 419 } 420 } 421 422 //===----------------------------------------------------------------------===// 423 // FoldingSetBucketIteratorImpl Implementation 424 425 FoldingSetBucketIteratorImpl::FoldingSetBucketIteratorImpl(void **Bucket) { 426 Ptr = (!*Bucket || !GetNextPtr(*Bucket)) ? (void*) Bucket : *Bucket; 427 } 428