FoldingSet.cpp revision 167b8bc24d4cc2789c682962b123877a73ad0568
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/APFloat.h" 19#include "llvm/ADT/APInt.h" 20#include "llvm/Support/MathExtras.h" 21#include <cassert> 22using namespace llvm; 23 24//===----------------------------------------------------------------------===// 25// FoldingSetNodeID Implementation 26 27/// Add* - Add various data types to Bit data. 28/// 29void FoldingSetNodeID::AddPointer(const void *Ptr) { 30 // Note: this adds pointers to the hash using sizes and endianness that 31 // depend on the host. It doesn't matter however, because hashing on 32 // pointer values in inherently unstable. Nothing should depend on the 33 // ordering of nodes in the folding set. 34 intptr_t PtrI = (intptr_t)Ptr; 35 Bits.push_back(unsigned(PtrI)); 36 if (sizeof(intptr_t) > sizeof(unsigned)) 37 Bits.push_back(unsigned(uint64_t(PtrI) >> 32)); 38} 39void FoldingSetNodeID::AddInteger(signed I) { 40 Bits.push_back(I); 41} 42void FoldingSetNodeID::AddInteger(unsigned I) { 43 Bits.push_back(I); 44} 45void FoldingSetNodeID::AddInteger(int64_t I) { 46 AddInteger((uint64_t)I); 47} 48void FoldingSetNodeID::AddInteger(uint64_t I) { 49 Bits.push_back(unsigned(I)); 50 51 // If the integer is small, encode it just as 32-bits. 52 if ((uint64_t)(int)I != I) 53 Bits.push_back(unsigned(I >> 32)); 54} 55void FoldingSetNodeID::AddFloat(float F) { 56 Bits.push_back(FloatToBits(F)); 57} 58void FoldingSetNodeID::AddDouble(double D) { 59 AddInteger(DoubleToBits(D)); 60} 61void FoldingSetNodeID::AddAPFloat(const APFloat& apf) { 62 APInt api = apf.convertToAPInt(); 63 AddAPInt(api); 64} 65void FoldingSetNodeID::AddAPInt(const APInt& api) { 66 const uint64_t *p = api.getRawData(); 67 for (unsigned i=0; i<api.getNumWords(); i++) 68 AddInteger(*p++); 69} 70void FoldingSetNodeID::AddString(const std::string &String) { 71 unsigned Size = String.size(); 72 Bits.push_back(Size); 73 if (!Size) return; 74 75 unsigned Units = Size / 4; 76 unsigned Pos = 0; 77 const unsigned *Base = (const unsigned *)String.data(); 78 79 // If the string is aligned do a bulk transfer. 80 if (!((intptr_t)Base & 3)) { 81 Bits.append(Base, Base + Units); 82 Pos = (Units + 1) * 4; 83 } else { 84 // Otherwise do it the hard way. 85 for ( Pos += 4; Pos <= Size; Pos += 4) { 86 unsigned V = ((unsigned char)String[Pos - 4] << 24) | 87 ((unsigned char)String[Pos - 3] << 16) | 88 ((unsigned char)String[Pos - 2] << 8) | 89 (unsigned char)String[Pos - 1]; 90 Bits.push_back(V); 91 } 92 } 93 94 // With the leftover bits. 95 unsigned V = 0; 96 // Pos will have overshot size by 4 - #bytes left over. 97 switch (Pos - Size) { 98 case 1: V = (V << 8) | (unsigned char)String[Size - 3]; // Fall thru. 99 case 2: V = (V << 8) | (unsigned char)String[Size - 2]; // Fall thru. 100 case 3: V = (V << 8) | (unsigned char)String[Size - 1]; break; 101 default: return; // Nothing left. 102 } 103 104 Bits.push_back(V); 105} 106 107/// ComputeHash - Compute a strong hash value for this FoldingSetNodeID, used to 108/// lookup the node in the FoldingSetImpl. 109unsigned FoldingSetNodeID::ComputeHash() const { 110 // This is adapted from SuperFastHash by Paul Hsieh. 111 unsigned Hash = Bits.size(); 112 for (const unsigned *BP = &Bits[0], *E = BP+Bits.size(); BP != E; ++BP) { 113 unsigned Data = *BP; 114 Hash += Data & 0xFFFF; 115 unsigned Tmp = ((Data >> 16) << 11) ^ Hash; 116 Hash = (Hash << 16) ^ Tmp; 117 Hash += Hash >> 11; 118 } 119 120 // Force "avalanching" of final 127 bits. 121 Hash ^= Hash << 3; 122 Hash += Hash >> 5; 123 Hash ^= Hash << 4; 124 Hash += Hash >> 17; 125 Hash ^= Hash << 25; 126 Hash += Hash >> 6; 127 return Hash; 128} 129 130/// operator== - Used to compare two nodes to each other. 131/// 132bool FoldingSetNodeID::operator==(const FoldingSetNodeID &RHS)const{ 133 if (Bits.size() != RHS.Bits.size()) return false; 134 return memcmp(&Bits[0], &RHS.Bits[0], Bits.size()*sizeof(Bits[0])) == 0; 135} 136 137 138//===----------------------------------------------------------------------===// 139/// Helper functions for FoldingSetImpl. 140 141/// GetNextPtr - In order to save space, each bucket is a 142/// singly-linked-list. In order to make deletion more efficient, we make 143/// the list circular, so we can delete a node without computing its hash. 144/// The problem with this is that the start of the hash buckets are not 145/// Nodes. If NextInBucketPtr is a bucket pointer, this method returns null: 146/// use GetBucketPtr when this happens. 147static FoldingSetImpl::Node *GetNextPtr(void *NextInBucketPtr) { 148 // The low bit is set if this is the pointer back to the bucket. 149 if (reinterpret_cast<intptr_t>(NextInBucketPtr) & 1) 150 return 0; 151 152 return static_cast<FoldingSetImpl::Node*>(NextInBucketPtr); 153} 154 155 156/// testing. 157static void **GetBucketPtr(void *NextInBucketPtr) { 158 intptr_t Ptr = reinterpret_cast<intptr_t>(NextInBucketPtr); 159 assert((Ptr & 1) && "Not a bucket pointer"); 160 return reinterpret_cast<void**>(Ptr & ~intptr_t(1)); 161} 162 163/// GetBucketFor - Hash the specified node ID and return the hash bucket for 164/// the specified ID. 165static void **GetBucketFor(const FoldingSetNodeID &ID, 166 void **Buckets, unsigned NumBuckets) { 167 // NumBuckets is always a power of 2. 168 unsigned BucketNum = ID.ComputeHash() & (NumBuckets-1); 169 return Buckets + BucketNum; 170} 171 172//===----------------------------------------------------------------------===// 173// FoldingSetImpl Implementation 174 175FoldingSetImpl::FoldingSetImpl(unsigned Log2InitSize) : NumNodes(0) { 176 assert(5 < Log2InitSize && Log2InitSize < 32 && 177 "Initial hash table size out of range"); 178 NumBuckets = 1 << Log2InitSize; 179 Buckets = new void*[NumBuckets+1]; 180 memset(Buckets, 0, NumBuckets*sizeof(void*)); 181 182 // Set the very last bucket to be a non-null "pointer". 183 Buckets[NumBuckets] = reinterpret_cast<void*>(-2); 184} 185FoldingSetImpl::~FoldingSetImpl() { 186 delete [] Buckets; 187} 188 189/// GrowHashTable - Double the size of the hash table and rehash everything. 190/// 191void FoldingSetImpl::GrowHashTable() { 192 void **OldBuckets = Buckets; 193 unsigned OldNumBuckets = NumBuckets; 194 NumBuckets <<= 1; 195 196 // Reset the node count to zero: we're going to reinsert everything. 197 NumNodes = 0; 198 199 // Clear out new buckets. 200 Buckets = new void*[NumBuckets+1]; 201 memset(Buckets, 0, NumBuckets*sizeof(void*)); 202 203 // Set the very last bucket to be a non-null "pointer". 204 Buckets[NumBuckets] = reinterpret_cast<void*>(-1); 205 206 // Walk the old buckets, rehashing nodes into their new place. 207 for (unsigned i = 0; i != OldNumBuckets; ++i) { 208 void *Probe = OldBuckets[i]; 209 if (!Probe) continue; 210 while (Node *NodeInBucket = GetNextPtr(Probe)) { 211 // Figure out the next link, remove NodeInBucket from the old link. 212 Probe = NodeInBucket->getNextInBucket(); 213 NodeInBucket->SetNextInBucket(0); 214 215 // Insert the node into the new bucket, after recomputing the hash. 216 FoldingSetNodeID ID; 217 GetNodeProfile(ID, NodeInBucket); 218 InsertNode(NodeInBucket, GetBucketFor(ID, Buckets, NumBuckets)); 219 } 220 } 221 222 delete[] OldBuckets; 223} 224 225/// FindNodeOrInsertPos - Look up the node specified by ID. If it exists, 226/// return it. If not, return the insertion token that will make insertion 227/// faster. 228FoldingSetImpl::Node 229*FoldingSetImpl::FindNodeOrInsertPos(const FoldingSetNodeID &ID, 230 void *&InsertPos) { 231 232 void **Bucket = GetBucketFor(ID, Buckets, NumBuckets); 233 void *Probe = *Bucket; 234 235 InsertPos = 0; 236 237 while (Node *NodeInBucket = GetNextPtr(Probe)) { 238 FoldingSetNodeID OtherID; 239 GetNodeProfile(OtherID, NodeInBucket); 240 if (OtherID == ID) 241 return NodeInBucket; 242 243 Probe = NodeInBucket->getNextInBucket(); 244 } 245 246 // Didn't find the node, return null with the bucket as the InsertPos. 247 InsertPos = Bucket; 248 return 0; 249} 250 251/// InsertNode - Insert the specified node into the folding set, knowing that it 252/// is not already in the map. InsertPos must be obtained from 253/// FindNodeOrInsertPos. 254void FoldingSetImpl::InsertNode(Node *N, void *InsertPos) { 255 assert(N->getNextInBucket() == 0); 256 // Do we need to grow the hashtable? 257 if (NumNodes+1 > NumBuckets*2) { 258 GrowHashTable(); 259 FoldingSetNodeID ID; 260 GetNodeProfile(ID, N); 261 InsertPos = GetBucketFor(ID, Buckets, NumBuckets); 262 } 263 264 ++NumNodes; 265 266 /// The insert position is actually a bucket pointer. 267 void **Bucket = static_cast<void**>(InsertPos); 268 269 void *Next = *Bucket; 270 271 // If this is the first insertion into this bucket, its next pointer will be 272 // null. Pretend as if it pointed to itself, setting the low bit to indicate 273 // that it is a pointer to the bucket. 274 if (Next == 0) 275 Next = reinterpret_cast<void*>(reinterpret_cast<intptr_t>(Bucket)|1); 276 277 // Set the node's next pointer, and make the bucket point to the node. 278 N->SetNextInBucket(Next); 279 *Bucket = N; 280} 281 282/// RemoveNode - Remove a node from the folding set, returning true if one was 283/// removed or false if the node was not in the folding set. 284bool FoldingSetImpl::RemoveNode(Node *N) { 285 // Because each bucket is a circular list, we don't need to compute N's hash 286 // to remove it. 287 void *Ptr = N->getNextInBucket(); 288 if (Ptr == 0) return false; // Not in folding set. 289 290 --NumNodes; 291 N->SetNextInBucket(0); 292 293 // Remember what N originally pointed to, either a bucket or another node. 294 void *NodeNextPtr = Ptr; 295 296 // Chase around the list until we find the node (or bucket) which points to N. 297 while (true) { 298 if (Node *NodeInBucket = GetNextPtr(Ptr)) { 299 // Advance pointer. 300 Ptr = NodeInBucket->getNextInBucket(); 301 302 // We found a node that points to N, change it to point to N's next node, 303 // removing N from the list. 304 if (Ptr == N) { 305 NodeInBucket->SetNextInBucket(NodeNextPtr); 306 return true; 307 } 308 } else { 309 void **Bucket = GetBucketPtr(Ptr); 310 Ptr = *Bucket; 311 312 // If we found that the bucket points to N, update the bucket to point to 313 // whatever is next. 314 if (Ptr == N) { 315 *Bucket = NodeNextPtr; 316 return true; 317 } 318 } 319 } 320} 321 322/// GetOrInsertNode - If there is an existing simple Node exactly 323/// equal to the specified node, return it. Otherwise, insert 'N' and it 324/// instead. 325FoldingSetImpl::Node *FoldingSetImpl::GetOrInsertNode(FoldingSetImpl::Node *N) { 326 FoldingSetNodeID ID; 327 GetNodeProfile(ID, N); 328 void *IP; 329 if (Node *E = FindNodeOrInsertPos(ID, IP)) 330 return E; 331 InsertNode(N, IP); 332 return N; 333} 334 335//===----------------------------------------------------------------------===// 336// FoldingSetIteratorImpl Implementation 337 338FoldingSetIteratorImpl::FoldingSetIteratorImpl(void **Bucket) { 339 // Skip to the first non-null non-self-cycle bucket. 340 while (*Bucket == 0 || GetNextPtr(*Bucket) == 0) 341 ++Bucket; 342 343 NodePtr = static_cast<FoldingSetNode*>(*Bucket); 344} 345 346void FoldingSetIteratorImpl::advance() { 347 // If there is another link within this bucket, go to it. 348 void *Probe = NodePtr->getNextInBucket(); 349 350 if (FoldingSetNode *NextNodeInBucket = GetNextPtr(Probe)) 351 NodePtr = NextNodeInBucket; 352 else { 353 // Otherwise, this is the last link in this bucket. 354 void **Bucket = GetBucketPtr(Probe); 355 356 // Skip to the next non-null non-self-cycle bucket. 357 do { 358 ++Bucket; 359 } while (*Bucket == 0 || GetNextPtr(*Bucket) == 0); 360 361 NodePtr = static_cast<FoldingSetNode*>(*Bucket); 362 } 363} 364 365//===----------------------------------------------------------------------===// 366// FoldingSetBucketIteratorImpl Implementation 367 368FoldingSetBucketIteratorImpl::FoldingSetBucketIteratorImpl(void **Bucket) { 369 Ptr = (*Bucket == 0 || GetNextPtr(*Bucket) == 0) ? (void*) Bucket : *Bucket; 370} 371