FoldingSet.cpp revision 34aae111ffdc5e2506d2f611fb07406e030be589
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(uint64_t I) { 44 Bits.push_back(unsigned(I)); 45 46 // If the integer is small, encode it just as 32-bits. 47 if ((uint64_t)(int)I != I) 48 Bits.push_back(unsigned(I >> 32)); 49} 50void FoldingSetImpl::NodeID::AddFloat(float F) { 51 Bits.push_back(FloatToBits(F)); 52} 53void FoldingSetImpl::NodeID::AddDouble(double D) { 54 AddInteger(DoubleToBits(D)); 55} 56void FoldingSetImpl::NodeID::AddString(const std::string &String) { 57 unsigned Size = String.size(); 58 Bits.push_back(Size); 59 if (!Size) return; 60 61 unsigned Units = Size / 4; 62 unsigned Pos = 0; 63 const unsigned *Base = (const unsigned *)String.data(); 64 65 // If the string is aligned do a bulk transfer. 66 if (!((intptr_t)Base & 3)) { 67 Bits.append(Base, Base + Units); 68 Pos = (Units + 1) * 4; 69 } else { 70 // Otherwise do it the hard way. 71 for ( Pos += 4; Pos <= Size; Pos += 4) { 72 unsigned V = ((unsigned char)String[Pos - 4] << 24) | 73 ((unsigned char)String[Pos - 3] << 16) | 74 ((unsigned char)String[Pos - 2] << 8) | 75 (unsigned char)String[Pos - 1]; 76 Bits.push_back(V); 77 } 78 } 79 80 // With the leftover bits. 81 unsigned V = 0; 82 // Pos will have overshot size by 4 - #bytes left over. 83 switch (Pos - Size) { 84 case 1: V = (V << 8) | (unsigned char)String[Size - 3]; // Fall thru. 85 case 2: V = (V << 8) | (unsigned char)String[Size - 2]; // Fall thru. 86 case 3: V = (V << 8) | (unsigned char)String[Size - 1]; break; 87 default: return; // Nothing left. 88 } 89 90 Bits.push_back(V); 91} 92 93/// ComputeHash - Compute a strong hash value for this NodeID, used to 94/// lookup the node in the FoldingSetImpl. 95unsigned FoldingSetImpl::NodeID::ComputeHash() const { 96 // This is adapted from SuperFastHash by Paul Hsieh. 97 unsigned Hash = Bits.size(); 98 for (const unsigned *BP = &Bits[0], *E = BP+Bits.size(); BP != E; ++BP) { 99 unsigned Data = *BP; 100 Hash += Data & 0xFFFF; 101 unsigned Tmp = ((Data >> 16) << 11) ^ Hash; 102 Hash = (Hash << 16) ^ Tmp; 103 Hash += Hash >> 11; 104 } 105 106 // Force "avalanching" of final 127 bits. 107 Hash ^= Hash << 3; 108 Hash += Hash >> 5; 109 Hash ^= Hash << 4; 110 Hash += Hash >> 17; 111 Hash ^= Hash << 25; 112 Hash += Hash >> 6; 113 return Hash; 114} 115 116/// operator== - Used to compare two nodes to each other. 117/// 118bool FoldingSetImpl::NodeID::operator==(const FoldingSetImpl::NodeID &RHS)const{ 119 if (Bits.size() != RHS.Bits.size()) return false; 120 return memcmp(&Bits[0], &RHS.Bits[0], Bits.size()*sizeof(Bits[0])) == 0; 121} 122 123 124//===----------------------------------------------------------------------===// 125/// Helper functions for FoldingSetImpl. 126 127/// GetNextPtr - In order to save space, each bucket is a 128/// singly-linked-list. In order to make deletion more efficient, we make 129/// the list circular, so we can delete a node without computing its hash. 130/// The problem with this is that the start of the hash buckets are not 131/// Nodes. If NextInBucketPtr is a bucket pointer, this method returns null: 132/// use GetBucketPtr when this happens. 133static FoldingSetImpl::Node *GetNextPtr(void *NextInBucketPtr, 134 void **Buckets, unsigned NumBuckets) { 135 if (NextInBucketPtr >= Buckets && NextInBucketPtr < Buckets + NumBuckets) 136 return 0; 137 return static_cast<FoldingSetImpl::Node*>(NextInBucketPtr); 138} 139 140/// GetBucketPtr - Provides a casting of a bucket pointer for isNode 141/// testing. 142static void **GetBucketPtr(void *NextInBucketPtr) { 143 return static_cast<void**>(NextInBucketPtr); 144} 145 146/// GetBucketFor - Hash the specified node ID and return the hash bucket for 147/// the specified ID. 148static void **GetBucketFor(const FoldingSetImpl::NodeID &ID, 149 void **Buckets, unsigned NumBuckets) { 150 // NumBuckets is always a power of 2. 151 unsigned BucketNum = ID.ComputeHash() & (NumBuckets-1); 152 return Buckets + BucketNum; 153} 154 155//===----------------------------------------------------------------------===// 156// FoldingSetImpl Implementation 157 158FoldingSetImpl::FoldingSetImpl(unsigned Log2InitSize) : NumNodes(0) { 159 assert(5 < Log2InitSize && Log2InitSize < 32 && 160 "Initial hash table size out of range"); 161 NumBuckets = 1 << Log2InitSize; 162 Buckets = new void*[NumBuckets]; 163 memset(Buckets, 0, NumBuckets*sizeof(void*)); 164} 165FoldingSetImpl::~FoldingSetImpl() { 166 delete [] Buckets; 167} 168 169/// GrowHashTable - Double the size of the hash table and rehash everything. 170/// 171void FoldingSetImpl::GrowHashTable() { 172 void **OldBuckets = Buckets; 173 unsigned OldNumBuckets = NumBuckets; 174 NumBuckets <<= 1; 175 176 // Reset the node count to zero: we're going to reinsert everything. 177 NumNodes = 0; 178 179 // Clear out new buckets. 180 Buckets = new void*[NumBuckets]; 181 memset(Buckets, 0, NumBuckets*sizeof(void*)); 182 183 // Walk the old buckets, rehashing nodes into their new place. 184 for (unsigned i = 0; i != OldNumBuckets; ++i) { 185 void *Probe = OldBuckets[i]; 186 if (!Probe) continue; 187 while (Node *NodeInBucket = GetNextPtr(Probe, OldBuckets, OldNumBuckets)) { 188 // Figure out the next link, remove NodeInBucket from the old link. 189 Probe = NodeInBucket->getNextInBucket(); 190 NodeInBucket->SetNextInBucket(0); 191 192 // Insert the node into the new bucket, after recomputing the hash. 193 NodeID ID; 194 GetNodeProfile(ID, NodeInBucket); 195 InsertNode(NodeInBucket, GetBucketFor(ID, Buckets, NumBuckets)); 196 } 197 } 198 199 delete[] OldBuckets; 200} 201 202/// FindNodeOrInsertPos - Look up the node specified by ID. If it exists, 203/// return it. If not, return the insertion token that will make insertion 204/// faster. 205FoldingSetImpl::Node *FoldingSetImpl::FindNodeOrInsertPos(const NodeID &ID, 206 void *&InsertPos) { 207 void **Bucket = GetBucketFor(ID, Buckets, NumBuckets); 208 void *Probe = *Bucket; 209 210 InsertPos = 0; 211 212 while (Node *NodeInBucket = GetNextPtr(Probe, Buckets, NumBuckets)) { 213 NodeID OtherID; 214 GetNodeProfile(OtherID, NodeInBucket); 215 if (OtherID == ID) 216 return NodeInBucket; 217 218 Probe = NodeInBucket->getNextInBucket(); 219 } 220 221 // Didn't find the node, return null with the bucket as the InsertPos. 222 InsertPos = Bucket; 223 return 0; 224} 225 226/// InsertNode - Insert the specified node into the folding set, knowing that it 227/// is not already in the map. InsertPos must be obtained from 228/// FindNodeOrInsertPos. 229void FoldingSetImpl::InsertNode(Node *N, void *InsertPos) { 230 assert(N->getNextInBucket() == 0); 231 // Do we need to grow the hashtable? 232 if (NumNodes+1 > NumBuckets*2) { 233 GrowHashTable(); 234 NodeID ID; 235 GetNodeProfile(ID, N); 236 InsertPos = GetBucketFor(ID, Buckets, NumBuckets); 237 } 238 239 ++NumNodes; 240 241 /// The insert position is actually a bucket pointer. 242 void **Bucket = static_cast<void**>(InsertPos); 243 244 void *Next = *Bucket; 245 246 // If this is the first insertion into this bucket, its next pointer will be 247 // null. Pretend as if it pointed to itself. 248 if (Next == 0) 249 Next = Bucket; 250 251 // Set the node's next pointer, and make the bucket point to the node. 252 N->SetNextInBucket(Next); 253 *Bucket = N; 254} 255 256/// RemoveNode - Remove a node from the folding set, returning true if one was 257/// removed or false if the node was not in the folding set. 258bool FoldingSetImpl::RemoveNode(Node *N) { 259 // Because each bucket is a circular list, we don't need to compute N's hash 260 // to remove it. 261 void *Ptr = N->getNextInBucket(); 262 if (Ptr == 0) return false; // Not in folding set. 263 264 --NumNodes; 265 N->SetNextInBucket(0); 266 267 // Remember what N originally pointed to, either a bucket or another node. 268 void *NodeNextPtr = Ptr; 269 270 // Chase around the list until we find the node (or bucket) which points to N. 271 while (true) { 272 if (Node *NodeInBucket = GetNextPtr(Ptr, Buckets, NumBuckets)) { 273 // Advance pointer. 274 Ptr = NodeInBucket->getNextInBucket(); 275 276 // We found a node that points to N, change it to point to N's next node, 277 // removing N from the list. 278 if (Ptr == N) { 279 NodeInBucket->SetNextInBucket(NodeNextPtr); 280 return true; 281 } 282 } else { 283 void **Bucket = GetBucketPtr(Ptr); 284 Ptr = *Bucket; 285 286 // If we found that the bucket points to N, update the bucket to point to 287 // whatever is next. 288 if (Ptr == N) { 289 *Bucket = NodeNextPtr; 290 return true; 291 } 292 } 293 } 294} 295 296/// GetOrInsertNode - If there is an existing simple Node exactly 297/// equal to the specified node, return it. Otherwise, insert 'N' and it 298/// instead. 299FoldingSetImpl::Node *FoldingSetImpl::GetOrInsertNode(FoldingSetImpl::Node *N) { 300 NodeID ID; 301 GetNodeProfile(ID, N); 302 void *IP; 303 if (Node *E = FindNodeOrInsertPos(ID, IP)) 304 return E; 305 InsertNode(N, IP); 306 return N; 307} 308