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/ADT/Hashing.h" 19 #include "llvm/Support/Allocator.h" 20 #include "llvm/Support/ErrorHandling.h" 21 #include "llvm/Support/MathExtras.h" 22 #include "llvm/Support/Host.h" 23 #include <cassert> 24 #include <cstring> 25 using namespace llvm; 26 27 //===----------------------------------------------------------------------===// 28 // FoldingSetNodeIDRef Implementation 29 30 /// ComputeHash - Compute a strong hash value for this FoldingSetNodeIDRef, 31 /// used to lookup the node in the FoldingSetImpl. 32 unsigned FoldingSetNodeIDRef::ComputeHash() const { 33 return static_cast<unsigned>(hash_combine_range(Data, Data+Size)); 34 } 35 36 bool FoldingSetNodeIDRef::operator==(FoldingSetNodeIDRef RHS) const { 37 if (Size != RHS.Size) return false; 38 return memcmp(Data, RHS.Data, Size*sizeof(*Data)) == 0; 39 } 40 41 /// Used to compare the "ordering" of two nodes as defined by the 42 /// profiled bits and their ordering defined by memcmp(). 43 bool FoldingSetNodeIDRef::operator<(FoldingSetNodeIDRef RHS) const { 44 if (Size != RHS.Size) 45 return Size < RHS.Size; 46 return memcmp(Data, RHS.Data, Size*sizeof(*Data)) < 0; 47 } 48 49 //===----------------------------------------------------------------------===// 50 // FoldingSetNodeID Implementation 51 52 /// Add* - Add various data types to Bit data. 53 /// 54 void FoldingSetNodeID::AddPointer(const void *Ptr) { 55 // Note: this adds pointers to the hash using sizes and endianness that 56 // depend on the host. It doesn't matter however, because hashing on 57 // pointer values in inherently unstable. Nothing should depend on the 58 // ordering of nodes in the folding set. 59 Bits.append(reinterpret_cast<unsigned *>(&Ptr), 60 reinterpret_cast<unsigned *>(&Ptr+1)); 61 } 62 void FoldingSetNodeID::AddInteger(signed I) { 63 Bits.push_back(I); 64 } 65 void FoldingSetNodeID::AddInteger(unsigned I) { 66 Bits.push_back(I); 67 } 68 void FoldingSetNodeID::AddInteger(long I) { 69 AddInteger((unsigned long)I); 70 } 71 void FoldingSetNodeID::AddInteger(unsigned long I) { 72 if (sizeof(long) == sizeof(int)) 73 AddInteger(unsigned(I)); 74 else if (sizeof(long) == sizeof(long long)) { 75 AddInteger((unsigned long long)I); 76 } else { 77 llvm_unreachable("unexpected sizeof(long)"); 78 } 79 } 80 void FoldingSetNodeID::AddInteger(long long I) { 81 AddInteger((unsigned long long)I); 82 } 83 void FoldingSetNodeID::AddInteger(unsigned long long I) { 84 AddInteger(unsigned(I)); 85 if ((uint64_t)(unsigned)I != I) 86 Bits.push_back(unsigned(I >> 32)); 87 } 88 89 void FoldingSetNodeID::AddString(StringRef String) { 90 unsigned Size = String.size(); 91 Bits.push_back(Size); 92 if (!Size) return; 93 94 unsigned Units = Size / 4; 95 unsigned Pos = 0; 96 const unsigned *Base = (const unsigned*) String.data(); 97 98 // If the string is aligned do a bulk transfer. 99 if (!((intptr_t)Base & 3)) { 100 Bits.append(Base, Base + Units); 101 Pos = (Units + 1) * 4; 102 } else { 103 // Otherwise do it the hard way. 104 // To be compatible with above bulk transfer, we need to take endianness 105 // into account. 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 { 115 assert(sys::isLittleEndianHost() && "Unexpected host endianness"); 116 for (Pos += 4; Pos <= Size; Pos += 4) { 117 unsigned V = ((unsigned char)String[Pos - 1] << 24) | 118 ((unsigned char)String[Pos - 2] << 16) | 119 ((unsigned char)String[Pos - 3] << 8) | 120 (unsigned char)String[Pos - 4]; 121 Bits.push_back(V); 122 } 123 } 124 } 125 126 // With the leftover bits. 127 unsigned V = 0; 128 // Pos will have overshot size by 4 - #bytes left over. 129 // No need to take endianness into account here - this is always executed. 130 switch (Pos - Size) { 131 case 1: V = (V << 8) | (unsigned char)String[Size - 3]; // Fall thru. 132 case 2: V = (V << 8) | (unsigned char)String[Size - 2]; // Fall thru. 133 case 3: V = (V << 8) | (unsigned char)String[Size - 1]; break; 134 default: return; // Nothing left. 135 } 136 137 Bits.push_back(V); 138 } 139 140 // AddNodeID - Adds the Bit data of another ID to *this. 141 void FoldingSetNodeID::AddNodeID(const FoldingSetNodeID &ID) { 142 Bits.append(ID.Bits.begin(), ID.Bits.end()); 143 } 144 145 /// ComputeHash - Compute a strong hash value for this FoldingSetNodeID, used to 146 /// lookup the node in the FoldingSetImpl. 147 unsigned FoldingSetNodeID::ComputeHash() const { 148 return FoldingSetNodeIDRef(Bits.data(), Bits.size()).ComputeHash(); 149 } 150 151 /// operator== - Used to compare two nodes to each other. 152 /// 153 bool FoldingSetNodeID::operator==(const FoldingSetNodeID &RHS)const{ 154 return *this == FoldingSetNodeIDRef(RHS.Bits.data(), RHS.Bits.size()); 155 } 156 157 /// operator== - Used to compare two nodes to each other. 158 /// 159 bool FoldingSetNodeID::operator==(FoldingSetNodeIDRef RHS) const { 160 return FoldingSetNodeIDRef(Bits.data(), Bits.size()) == RHS; 161 } 162 163 /// Used to compare the "ordering" of two nodes as defined by the 164 /// profiled bits and their ordering defined by memcmp(). 165 bool FoldingSetNodeID::operator<(const FoldingSetNodeID &RHS)const{ 166 return *this < FoldingSetNodeIDRef(RHS.Bits.data(), RHS.Bits.size()); 167 } 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 unsigned IDHash = ID.ComputeHash(); 287 void **Bucket = GetBucketFor(IDHash, 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, IDHash, 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 } 427