FoldingSet.cpp revision e27c3ea2bcdabf1b8be87675c66a38c3ad0ac1f9
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> 24using 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. 31unsigned 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 52bool 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/// 62void 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} 72void FoldingSetNodeID::AddInteger(signed I) { 73 Bits.push_back(I); 74} 75void FoldingSetNodeID::AddInteger(unsigned I) { 76 Bits.push_back(I); 77} 78void FoldingSetNodeID::AddInteger(long I) { 79 AddInteger((unsigned long)I); 80} 81void 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} 90void FoldingSetNodeID::AddInteger(long long I) { 91 AddInteger((unsigned long long)I); 92} 93void FoldingSetNodeID::AddInteger(unsigned long long I) { 94 AddInteger(unsigned(I)); 95 if ((uint64_t)(int)I != I) 96 Bits.push_back(unsigned(I >> 32)); 97} 98 99void 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. 151void 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. 157unsigned FoldingSetNodeID::ComputeHash() const { 158 return FoldingSetNodeIDRef(Bits.data(), Bits.size()).ComputeHash(); 159} 160 161/// operator== - Used to compare two nodes to each other. 162/// 163bool 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/// 169bool 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. 176FoldingSetNodeIDRef 177FoldingSetNodeID::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. 192static 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. 202static 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. 210static 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. 217static 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 227FoldingSetImpl::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} 234FoldingSetImpl::~FoldingSetImpl() { 235 free(Buckets); 236} 237void 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/// 250void 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. 283FoldingSetImpl::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. 309void 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. 338bool 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. 379FoldingSetImpl::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 392FoldingSetIteratorImpl::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 401void 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 424FoldingSetBucketIteratorImpl::FoldingSetBucketIteratorImpl(void **Bucket) { 425 Ptr = (*Bucket == 0 || GetNextPtr(*Bucket) == 0) ? (void*) Bucket : *Bucket; 426} 427