FoldingSet.cpp revision 9e3d3abd937c9bb79d56d25ec0e0724c7cbba67c
1//===-- Support/FoldingSet.cpp - Uniquing Hash Set --------------*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file was developed by James M. Laskey and is distributed under 6// the University of Illinois Open Source 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/MathExtras.h" 19#include <cassert> 20using namespace llvm; 21 22//===----------------------------------------------------------------------===// 23// FoldingSetImpl::NodeID Implementation 24 25/// Add* - Add various data types to Bit data. 26/// 27void FoldingSetImpl::NodeID::AddPointer(const void *Ptr) { 28 // Note: this adds pointers to the hash using sizes and endianness that 29 // depend on the host. It doesn't matter however, because hashing on 30 // pointer values in inherently unstable. Nothing should depend on the 31 // ordering of nodes in the folding set. 32 intptr_t PtrI = (intptr_t)Ptr; 33 Bits.push_back(unsigned(PtrI)); 34 if (sizeof(intptr_t) > sizeof(unsigned)) 35 Bits.push_back(unsigned(uint64_t(PtrI) >> 32)); 36} 37void FoldingSetImpl::NodeID::AddInteger(signed I) { 38 Bits.push_back(I); 39} 40void FoldingSetImpl::NodeID::AddInteger(unsigned I) { 41 Bits.push_back(I); 42} 43void FoldingSetImpl::NodeID::AddInteger(int64_t I) { 44 AddInteger((uint64_t)I); 45} 46void FoldingSetImpl::NodeID::AddInteger(uint64_t I) { 47 Bits.push_back(unsigned(I)); 48 49 // If the integer is small, encode it just as 32-bits. 50 if ((uint64_t)(int)I != I) 51 Bits.push_back(unsigned(I >> 32)); 52} 53void FoldingSetImpl::NodeID::AddFloat(float F) { 54 Bits.push_back(FloatToBits(F)); 55} 56void FoldingSetImpl::NodeID::AddDouble(double D) { 57 AddInteger(DoubleToBits(D)); 58} 59void FoldingSetImpl::NodeID::AddAPFloat(const APFloat& apf) { 60 APInt api = apf.convertToAPInt(); 61 const uint64_t *p = api.getRawData(); 62 for (int i=0; i<api.getNumWords(); i++) 63 AddInteger(*p++); 64} 65void FoldingSetImpl::NodeID::AddString(const std::string &String) { 66 unsigned Size = String.size(); 67 Bits.push_back(Size); 68 if (!Size) return; 69 70 unsigned Units = Size / 4; 71 unsigned Pos = 0; 72 const unsigned *Base = (const unsigned *)String.data(); 73 74 // If the string is aligned do a bulk transfer. 75 if (!((intptr_t)Base & 3)) { 76 Bits.append(Base, Base + Units); 77 Pos = (Units + 1) * 4; 78 } else { 79 // Otherwise do it the hard way. 80 for ( Pos += 4; Pos <= Size; Pos += 4) { 81 unsigned V = ((unsigned char)String[Pos - 4] << 24) | 82 ((unsigned char)String[Pos - 3] << 16) | 83 ((unsigned char)String[Pos - 2] << 8) | 84 (unsigned char)String[Pos - 1]; 85 Bits.push_back(V); 86 } 87 } 88 89 // With the leftover bits. 90 unsigned V = 0; 91 // Pos will have overshot size by 4 - #bytes left over. 92 switch (Pos - Size) { 93 case 1: V = (V << 8) | (unsigned char)String[Size - 3]; // Fall thru. 94 case 2: V = (V << 8) | (unsigned char)String[Size - 2]; // Fall thru. 95 case 3: V = (V << 8) | (unsigned char)String[Size - 1]; break; 96 default: return; // Nothing left. 97 } 98 99 Bits.push_back(V); 100} 101 102/// ComputeHash - Compute a strong hash value for this NodeID, used to 103/// lookup the node in the FoldingSetImpl. 104unsigned FoldingSetImpl::NodeID::ComputeHash() const { 105 // This is adapted from SuperFastHash by Paul Hsieh. 106 unsigned Hash = Bits.size(); 107 for (const unsigned *BP = &Bits[0], *E = BP+Bits.size(); BP != E; ++BP) { 108 unsigned Data = *BP; 109 Hash += Data & 0xFFFF; 110 unsigned Tmp = ((Data >> 16) << 11) ^ Hash; 111 Hash = (Hash << 16) ^ Tmp; 112 Hash += Hash >> 11; 113 } 114 115 // Force "avalanching" of final 127 bits. 116 Hash ^= Hash << 3; 117 Hash += Hash >> 5; 118 Hash ^= Hash << 4; 119 Hash += Hash >> 17; 120 Hash ^= Hash << 25; 121 Hash += Hash >> 6; 122 return Hash; 123} 124 125/// operator== - Used to compare two nodes to each other. 126/// 127bool FoldingSetImpl::NodeID::operator==(const FoldingSetImpl::NodeID &RHS)const{ 128 if (Bits.size() != RHS.Bits.size()) return false; 129 return memcmp(&Bits[0], &RHS.Bits[0], Bits.size()*sizeof(Bits[0])) == 0; 130} 131 132 133//===----------------------------------------------------------------------===// 134/// Helper functions for FoldingSetImpl. 135 136/// GetNextPtr - In order to save space, each bucket is a 137/// singly-linked-list. In order to make deletion more efficient, we make 138/// the list circular, so we can delete a node without computing its hash. 139/// The problem with this is that the start of the hash buckets are not 140/// Nodes. If NextInBucketPtr is a bucket pointer, this method returns null: 141/// use GetBucketPtr when this happens. 142static FoldingSetImpl::Node *GetNextPtr(void *NextInBucketPtr, 143 void **Buckets, unsigned NumBuckets) { 144 if (NextInBucketPtr >= Buckets && NextInBucketPtr < Buckets + NumBuckets) 145 return 0; 146 return static_cast<FoldingSetImpl::Node*>(NextInBucketPtr); 147} 148 149/// GetBucketPtr - Provides a casting of a bucket pointer for isNode 150/// testing. 151static void **GetBucketPtr(void *NextInBucketPtr) { 152 return static_cast<void**>(NextInBucketPtr); 153} 154 155/// GetBucketFor - Hash the specified node ID and return the hash bucket for 156/// the specified ID. 157static void **GetBucketFor(const FoldingSetImpl::NodeID &ID, 158 void **Buckets, unsigned NumBuckets) { 159 // NumBuckets is always a power of 2. 160 unsigned BucketNum = ID.ComputeHash() & (NumBuckets-1); 161 return Buckets + BucketNum; 162} 163 164//===----------------------------------------------------------------------===// 165// FoldingSetImpl Implementation 166 167FoldingSetImpl::FoldingSetImpl(unsigned Log2InitSize) : NumNodes(0) { 168 assert(5 < Log2InitSize && Log2InitSize < 32 && 169 "Initial hash table size out of range"); 170 NumBuckets = 1 << Log2InitSize; 171 Buckets = new void*[NumBuckets]; 172 memset(Buckets, 0, NumBuckets*sizeof(void*)); 173} 174FoldingSetImpl::~FoldingSetImpl() { 175 delete [] Buckets; 176} 177 178/// GrowHashTable - Double the size of the hash table and rehash everything. 179/// 180void FoldingSetImpl::GrowHashTable() { 181 void **OldBuckets = Buckets; 182 unsigned OldNumBuckets = NumBuckets; 183 NumBuckets <<= 1; 184 185 // Reset the node count to zero: we're going to reinsert everything. 186 NumNodes = 0; 187 188 // Clear out new buckets. 189 Buckets = new void*[NumBuckets]; 190 memset(Buckets, 0, NumBuckets*sizeof(void*)); 191 192 // Walk the old buckets, rehashing nodes into their new place. 193 for (unsigned i = 0; i != OldNumBuckets; ++i) { 194 void *Probe = OldBuckets[i]; 195 if (!Probe) continue; 196 while (Node *NodeInBucket = GetNextPtr(Probe, OldBuckets, OldNumBuckets)) { 197 // Figure out the next link, remove NodeInBucket from the old link. 198 Probe = NodeInBucket->getNextInBucket(); 199 NodeInBucket->SetNextInBucket(0); 200 201 // Insert the node into the new bucket, after recomputing the hash. 202 NodeID ID; 203 GetNodeProfile(ID, NodeInBucket); 204 InsertNode(NodeInBucket, GetBucketFor(ID, Buckets, NumBuckets)); 205 } 206 } 207 208 delete[] OldBuckets; 209} 210 211/// FindNodeOrInsertPos - Look up the node specified by ID. If it exists, 212/// return it. If not, return the insertion token that will make insertion 213/// faster. 214FoldingSetImpl::Node *FoldingSetImpl::FindNodeOrInsertPos(const NodeID &ID, 215 void *&InsertPos) { 216 void **Bucket = GetBucketFor(ID, Buckets, NumBuckets); 217 void *Probe = *Bucket; 218 219 InsertPos = 0; 220 221 while (Node *NodeInBucket = GetNextPtr(Probe, Buckets, NumBuckets)) { 222 NodeID OtherID; 223 GetNodeProfile(OtherID, NodeInBucket); 224 if (OtherID == ID) 225 return NodeInBucket; 226 227 Probe = NodeInBucket->getNextInBucket(); 228 } 229 230 // Didn't find the node, return null with the bucket as the InsertPos. 231 InsertPos = Bucket; 232 return 0; 233} 234 235/// InsertNode - Insert the specified node into the folding set, knowing that it 236/// is not already in the map. InsertPos must be obtained from 237/// FindNodeOrInsertPos. 238void FoldingSetImpl::InsertNode(Node *N, void *InsertPos) { 239 assert(N->getNextInBucket() == 0); 240 // Do we need to grow the hashtable? 241 if (NumNodes+1 > NumBuckets*2) { 242 GrowHashTable(); 243 NodeID ID; 244 GetNodeProfile(ID, N); 245 InsertPos = GetBucketFor(ID, Buckets, NumBuckets); 246 } 247 248 ++NumNodes; 249 250 /// The insert position is actually a bucket pointer. 251 void **Bucket = static_cast<void**>(InsertPos); 252 253 void *Next = *Bucket; 254 255 // If this is the first insertion into this bucket, its next pointer will be 256 // null. Pretend as if it pointed to itself. 257 if (Next == 0) 258 Next = Bucket; 259 260 // Set the node's next pointer, and make the bucket point to the node. 261 N->SetNextInBucket(Next); 262 *Bucket = N; 263} 264 265/// RemoveNode - Remove a node from the folding set, returning true if one was 266/// removed or false if the node was not in the folding set. 267bool FoldingSetImpl::RemoveNode(Node *N) { 268 // Because each bucket is a circular list, we don't need to compute N's hash 269 // to remove it. 270 void *Ptr = N->getNextInBucket(); 271 if (Ptr == 0) return false; // Not in folding set. 272 273 --NumNodes; 274 N->SetNextInBucket(0); 275 276 // Remember what N originally pointed to, either a bucket or another node. 277 void *NodeNextPtr = Ptr; 278 279 // Chase around the list until we find the node (or bucket) which points to N. 280 while (true) { 281 if (Node *NodeInBucket = GetNextPtr(Ptr, Buckets, NumBuckets)) { 282 // Advance pointer. 283 Ptr = NodeInBucket->getNextInBucket(); 284 285 // We found a node that points to N, change it to point to N's next node, 286 // removing N from the list. 287 if (Ptr == N) { 288 NodeInBucket->SetNextInBucket(NodeNextPtr); 289 return true; 290 } 291 } else { 292 void **Bucket = GetBucketPtr(Ptr); 293 Ptr = *Bucket; 294 295 // If we found that the bucket points to N, update the bucket to point to 296 // whatever is next. 297 if (Ptr == N) { 298 *Bucket = NodeNextPtr; 299 return true; 300 } 301 } 302 } 303} 304 305/// GetOrInsertNode - If there is an existing simple Node exactly 306/// equal to the specified node, return it. Otherwise, insert 'N' and it 307/// instead. 308FoldingSetImpl::Node *FoldingSetImpl::GetOrInsertNode(FoldingSetImpl::Node *N) { 309 NodeID ID; 310 GetNodeProfile(ID, N); 311 void *IP; 312 if (Node *E = FindNodeOrInsertPos(ID, IP)) 313 return E; 314 InsertNode(N, IP); 315 return N; 316} 317