FoldingSet.cpp revision 0e5af195f6c54dbf5a24a1ec12ed2d0bd02f5b7f
15821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)//===-- Support/FoldingSet.cpp - Uniquing Hash Set --------------*- C++ -*-===// 25821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// 35821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// The LLVM Compiler Infrastructure 45821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// 55821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// This file was developed by James M. Laskey and is distributed under 65821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// the University of Illinois Open Source License. See LICENSE.TXT for details. 75821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// 85821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)//===----------------------------------------------------------------------===// 95821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// 105821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// This file implements a hash set that can be used to remove duplication of 115821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// nodes in a graph. This code was originally created by Chris Lattner for use 125821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// with SelectionDAGCSEMap, but was isolated to provide use across the llvm code 135821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// set. 145821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)// 155821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)//===----------------------------------------------------------------------===// 165821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 175821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "llvm/ADT/FoldingSet.h" 185821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles) 195821806d5e7f356e8fa4b058a389a808ea183019Torne (Richard Coles)#include "llvm/ADT/MathExtras.h" 20 21using namespace llvm; 22 23//===----------------------------------------------------------------------===// 24// FoldingSetImpl::NodeID Implementation 25 26/// Add* - Add various data types to Bit data. 27/// 28void FoldingSetImpl::NodeID::AddPointer(const void *Ptr) { 29 // Note: this adds pointers to the hash using sizes and endianness that 30 // depend on the host. It doesn't matter however, because hashing on 31 // pointer values in inherently unstable. Nothing should depend on the 32 // ordering of nodes in the folding set. 33 intptr_t PtrI = (intptr_t)Ptr; 34 Bits.push_back(unsigned(PtrI)); 35 if (sizeof(intptr_t) > sizeof(unsigned)) 36 Bits.push_back(unsigned(uint64_t(PtrI) >> 32)); 37} 38void FoldingSetImpl::NodeID::AddInteger(signed I) { 39 Bits.push_back(I); 40} 41void FoldingSetImpl::NodeID::AddInteger(unsigned I) { 42 Bits.push_back(I); 43} 44void FoldingSetImpl::NodeID::AddInteger(uint64_t I) { 45 Bits.push_back(unsigned(I)); 46 Bits.push_back(unsigned(I >> 32)); 47} 48void FoldingSetImpl::NodeID::AddFloat(float F) { 49 Bits.push_back(FloatToBits(F)); 50} 51void FoldingSetImpl::NodeID::AddDouble(double D) { 52 Bits.push_back(DoubleToBits(D)); 53} 54void FoldingSetImpl::NodeID::AddString(const std::string &String) { 55 // Note: An assumption is made here that strings are composed of one byte 56 // chars. 57 unsigned Size = String.size(); 58 unsigned Units = Size / sizeof(unsigned); 59 const unsigned *Base = (const unsigned *)String.data(); 60 Bits.insert(Bits.end(), Base, Base + Units); 61 if (Size & 3) { 62 unsigned V = 0; 63 for (unsigned i = Units * sizeof(unsigned); i < Size; ++i) 64 V = (V << 8) | String[i]; 65 Bits.push_back(V); 66 } 67} 68 69/// ComputeHash - Compute a strong hash value for this NodeID, used to 70/// lookup the node in the FoldingSetImpl. 71unsigned FoldingSetImpl::NodeID::ComputeHash() const { 72 // This is adapted from SuperFastHash by Paul Hsieh. 73 unsigned Hash = Bits.size(); 74 for (const unsigned *BP = &Bits[0], *E = BP+Bits.size(); BP != E; ++BP) { 75 unsigned Data = *BP; 76 Hash += Data & 0xFFFF; 77 unsigned Tmp = ((Data >> 16) << 11) ^ Hash; 78 Hash = (Hash << 16) ^ Tmp; 79 Hash += Hash >> 11; 80 } 81 82 // Force "avalanching" of final 127 bits. 83 Hash ^= Hash << 3; 84 Hash += Hash >> 5; 85 Hash ^= Hash << 4; 86 Hash += Hash >> 17; 87 Hash ^= Hash << 25; 88 Hash += Hash >> 6; 89 return Hash; 90} 91 92/// operator== - Used to compare two nodes to each other. 93/// 94bool FoldingSetImpl::NodeID::operator==(const FoldingSetImpl::NodeID &RHS)const{ 95 if (Bits.size() != RHS.Bits.size()) return false; 96 return memcmp(&Bits[0], &RHS.Bits[0], Bits.size()*sizeof(Bits[0])) == 0; 97} 98 99 100//===----------------------------------------------------------------------===// 101// FoldingSetImpl Implementation 102 103FoldingSetImpl::FoldingSetImpl() : NumNodes(0) { 104 NumBuckets = 64; 105 Buckets = new void*[NumBuckets]; 106 memset(Buckets, 0, NumBuckets*sizeof(void*)); 107} 108FoldingSetImpl::~FoldingSetImpl() { 109 delete [] Buckets; 110} 111 112/// GetNextPtr - In order to save space, each bucket is a 113/// singly-linked-list. In order to make deletion more efficient, we make 114/// the list circular, so we can delete a node without computing its hash. 115/// The problem with this is that the start of the hash buckets are not 116/// Nodes. If NextInBucketPtr is a bucket pointer, this method returns null 117/// : use GetBucketPtr when this happens. 118FoldingSetImpl::Node *FoldingSetImpl::GetNextPtr(void *NextInBucketPtr) { 119 if (NextInBucketPtr >= Buckets && NextInBucketPtr < Buckets+NumBuckets) 120 return 0; 121 return static_cast<Node*>(NextInBucketPtr); 122} 123 124/// GetNextPtr - This is just like the previous GetNextPtr implementation, 125/// but allows a bucket array to be specified. 126FoldingSetImpl::Node *FoldingSetImpl::GetNextPtr(void *NextInBucketPtr, 127 void **Bucks, 128 unsigned NumBuck) { 129 if (NextInBucketPtr >= Bucks && NextInBucketPtr < Bucks+NumBuck) 130 return 0; 131 return static_cast<Node*>(NextInBucketPtr); 132} 133 134/// GetBucketPtr - Provides a casting of a bucket pointer for isNode 135/// testing. 136void **FoldingSetImpl::GetBucketPtr(void *NextInBucketPtr) { 137 return static_cast<void**>(NextInBucketPtr); 138} 139 140/// GetBucketFor - Hash the specified node ID and return the hash bucket for 141/// the specified ID. 142void **FoldingSetImpl::GetBucketFor(const NodeID &ID) const { 143 // NumBuckets is always a power of 2. 144 unsigned BucketNum = ID.ComputeHash() & (NumBuckets-1); 145 return Buckets+BucketNum; 146} 147 148/// GrowHashTable - Double the size of the hash table and rehash everything. 149/// 150void FoldingSetImpl::GrowHashTable() { 151 void **OldBuckets = Buckets; 152 unsigned OldNumBuckets = NumBuckets; 153 NumBuckets <<= 1; 154 155 // Reset the node count to zero: we're going to reinsert everything. 156 NumNodes = 0; 157 158 // Clear out new buckets. 159 Buckets = new void*[NumBuckets]; 160 memset(Buckets, 0, NumBuckets*sizeof(void*)); 161 162 // Walk the old buckets, rehashing nodes into their new place. 163 for (unsigned i = 0; i != OldNumBuckets; ++i) { 164 void *Probe = OldBuckets[i]; 165 if (!Probe) continue; 166 while (Node *NodeInBucket = GetNextPtr(Probe, OldBuckets, OldNumBuckets)){ 167 // Figure out the next link, remove NodeInBucket from the old link. 168 Probe = NodeInBucket->getNextInBucket(); 169 NodeInBucket->SetNextInBucket(0); 170 171 // Insert the node into the new bucket, after recomputing the hash. 172 NodeID ID; 173 GetNodeProfile(ID, NodeInBucket); 174 InsertNode(NodeInBucket, GetBucketFor(ID)); 175 } 176 } 177 178 delete[] OldBuckets; 179} 180 181/// FindNodeOrInsertPos - Look up the node specified by ID. If it exists, 182/// return it. If not, return the insertion token that will make insertion 183/// faster. 184FoldingSetImpl::Node *FoldingSetImpl::FindNodeOrInsertPos(const NodeID &ID, 185 void *&InsertPos) { 186 void **Bucket = GetBucketFor(ID); 187 void *Probe = *Bucket; 188 189 InsertPos = 0; 190 191 while (Node *NodeInBucket = GetNextPtr(Probe)) { 192 NodeID OtherID; 193 GetNodeProfile(OtherID, NodeInBucket); 194 if (OtherID == ID) 195 return NodeInBucket; 196 197 Probe = NodeInBucket->getNextInBucket(); 198 } 199 200 // Didn't find the node, return null with the bucket as the InsertPos. 201 InsertPos = Bucket; 202 return 0; 203} 204 205/// InsertNode - Insert the specified node into the folding set, knowing that it 206/// is not already in the map. InsertPos must be obtained from 207/// FindNodeOrInsertPos. 208void FoldingSetImpl::InsertNode(Node *N, void *InsertPos) { 209 ++NumNodes; 210 // Do we need to grow the hashtable? 211 if (NumNodes > NumBuckets*2) { 212 GrowHashTable(); 213 NodeID ID; 214 GetNodeProfile(ID, N); 215 InsertPos = GetBucketFor(ID); 216 } 217 218 /// The insert position is actually a bucket pointer. 219 void **Bucket = static_cast<void**>(InsertPos); 220 221 void *Next = *Bucket; 222 223 // If this is the first insertion into this bucket, its next pointer will be 224 // null. Pretend as if it pointed to itself. 225 if (Next == 0) 226 Next = Bucket; 227 228 // Set the nodes next pointer, and make the bucket point to the node. 229 N->SetNextInBucket(Next); 230 *Bucket = N; 231} 232 233/// RemoveNode - Remove a node from the folding set, returning true if one was 234/// removed or false if the node was not in the folding set. 235bool FoldingSetImpl::RemoveNode(Node *N) { 236 // Because each bucket is a circular list, we don't need to compute N's hash 237 // to remove it. Chase around the list until we find the node (or bucket) 238 // which points to N. 239 void *Ptr = N->getNextInBucket(); 240 if (Ptr == 0) return false; // Not in folding set. 241 242 --NumNodes; 243 244 void *NodeNextPtr = Ptr; 245 N->SetNextInBucket(0); 246 while (true) { 247 if (Node *NodeInBucket = GetNextPtr(Ptr)) { 248 // Advance pointer. 249 Ptr = NodeInBucket->getNextInBucket(); 250 251 // We found a node that points to N, change it to point to N's next node, 252 // removing N from the list. 253 if (Ptr == N) { 254 NodeInBucket->SetNextInBucket(NodeNextPtr); 255 return true; 256 } 257 } else { 258 void **Bucket = GetBucketPtr(Ptr); 259 Ptr = *Bucket; 260 261 // If we found that the bucket points to N, update the bucket to point to 262 // whatever is next. 263 if (Ptr == N) { 264 *Bucket = NodeNextPtr; 265 return true; 266 } 267 } 268 } 269} 270 271/// GetOrInsertNode - If there is an existing simple Node exactly 272/// equal to the specified node, return it. Otherwise, insert 'N' and it 273/// instead. 274FoldingSetImpl::Node *FoldingSetImpl::GetOrInsertNode(FoldingSetImpl::Node *N) { 275 NodeID ID; 276 GetNodeProfile(ID, N); 277 void *IP; 278 if (Node *E = FindNodeOrInsertPos(ID, IP)) 279 return E; 280 InsertNode(N, IP); 281 return N; 282} 283