FoldingSet.h revision 9e3d3abd937c9bb79d56d25ec0e0724c7cbba67c
1//===-- llvm/ADT/FoldingSet.h - 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 defines a hash set that can be used to remove duplication of nodes 11// in a graph. This code was originally created by Chris Lattner for use with 12// SelectionDAGCSEMap, but was isolated to provide use across the llvm code set. 13// 14//===----------------------------------------------------------------------===// 15 16#ifndef LLVM_ADT_FOLDINGSET_H 17#define LLVM_ADT_FOLDINGSET_H 18 19#include "llvm/Support/DataTypes.h" 20#include "llvm/ADT/SmallVector.h" 21#include "llvm/ADT/APFloat.h" 22#include <string> 23 24namespace llvm { 25 26/// This folding set used for two purposes: 27/// 1. Given information about a node we want to create, look up the unique 28/// instance of the node in the set. If the node already exists, return 29/// it, otherwise return the bucket it should be inserted into. 30/// 2. Given a node that has already been created, remove it from the set. 31/// 32/// This class is implemented as a single-link chained hash table, where the 33/// "buckets" are actually the nodes themselves (the next pointer is in the 34/// node). The last node points back to the bucket to simplified node removal. 35/// 36/// Any node that is to be included in the folding set must be a subclass of 37/// FoldingSetNode. The node class must also define a Profile method used to 38/// establish the unique bits of data for the node. The Profile method is 39/// passed a FoldingSetNodeID object which is used to gather the bits. Just 40/// call one of the Add* functions defined in the FoldingSetImpl::NodeID class. 41/// NOTE: That the folding set does not own the nodes and it is the 42/// responsibility of the user to dispose of the nodes. 43/// 44/// Eg. 45/// class MyNode : public FoldingSetNode { 46/// private: 47/// std::string Name; 48/// unsigned Value; 49/// public: 50/// MyNode(const char *N, unsigned V) : Name(N), Value(V) {} 51/// ... 52/// void Profile(FoldingSetNodeID &ID) { 53/// ID.AddString(Name); 54/// ID.AddInteger(Value); 55/// } 56/// ... 57/// }; 58/// 59/// To define the folding set itself use the FoldingSet template; 60/// 61/// Eg. 62/// FoldingSet<MyNode> MyFoldingSet; 63/// 64/// Four public methods are available to manipulate the folding set; 65/// 66/// 1) If you have an existing node that you want add to the set but unsure 67/// that the node might already exist then call; 68/// 69/// MyNode *M = MyFoldingSet.GetOrInsertNode(N); 70/// 71/// If The result is equal to the input then the node has been inserted. 72/// Otherwise, the result is the node existing in the folding set, and the 73/// input can be discarded (use the result instead.) 74/// 75/// 2) If you are ready to construct a node but want to check if it already 76/// exists, then call FindNodeOrInsertPos with a FoldingSetNodeID of the bits to 77/// check; 78/// 79/// FoldingSetNodeID ID; 80/// ID.AddString(Name); 81/// ID.AddInteger(Value); 82/// void *InsertPoint; 83/// 84/// MyNode *M = MyFoldingSet.FindNodeOrInsertPos(ID, InsertPoint); 85/// 86/// If found then M with be non-NULL, else InsertPoint will point to where it 87/// should be inserted using InsertNode. 88/// 89/// 3) If you get a NULL result from FindNodeOrInsertPos then you can as a new 90/// node with FindNodeOrInsertPos; 91/// 92/// InsertNode(N, InsertPoint); 93/// 94/// 4) Finally, if you want to remove a node from the folding set call; 95/// 96/// bool WasRemoved = RemoveNode(N); 97/// 98/// The result indicates whether the node existed in the folding set. 99 100 101//===----------------------------------------------------------------------===// 102/// FoldingSetImpl - Implements the folding set functionality. The main 103/// structure is an array of buckets. Each bucket is indexed by the hash of 104/// the nodes it contains. The bucket itself points to the nodes contained 105/// in the bucket via a singly linked list. The last node in the list points 106/// back to the bucket to facilitate node removal. 107/// 108class FoldingSetImpl { 109private: 110 /// Buckets - Array of bucket chains. 111 /// 112 void **Buckets; 113 114 /// NumBuckets - Length of the Buckets array. Always a power of 2. 115 /// 116 unsigned NumBuckets; 117 118 /// NumNodes - Number of nodes in the folding set. Growth occurs when NumNodes 119 /// is greater than twice the number of buckets. 120 unsigned NumNodes; 121 122public: 123 explicit FoldingSetImpl(unsigned Log2InitSize = 6); 124 virtual ~FoldingSetImpl(); 125 126 // Forward declaration. 127 class Node; 128 129 //===--------------------------------------------------------------------===// 130 /// NodeID - This class is used to gather all the unique data bits of a 131 /// node. When all the bits are gathered this class is used to produce a 132 /// hash value for the node. 133 /// 134 class NodeID { 135 /// Bits - Vector of all the data bits that make the node unique. 136 /// Use a SmallVector to avoid a heap allocation in the common case. 137 SmallVector<unsigned, 32> Bits; 138 139 public: 140 NodeID() {} 141 142 /// getRawData - Return the ith entry in the Bits data. 143 /// 144 unsigned getRawData(unsigned i) const { 145 return Bits[i]; 146 } 147 148 /// Add* - Add various data types to Bit data. 149 /// 150 void AddPointer(const void *Ptr); 151 void AddInteger(signed I); 152 void AddInteger(unsigned I); 153 void AddInteger(int64_t I); 154 void AddInteger(uint64_t I); 155 void AddFloat(float F); 156 void AddDouble(double D); 157 void AddAPFloat(const APFloat& apf); 158 void AddString(const std::string &String); 159 160 /// ComputeHash - Compute a strong hash value for this NodeID, used to 161 /// lookup the node in the FoldingSetImpl. 162 unsigned ComputeHash() const; 163 164 /// operator== - Used to compare two nodes to each other. 165 /// 166 bool operator==(const NodeID &RHS) const; 167 }; 168 169 //===--------------------------------------------------------------------===// 170 /// Node - This class is used to maintain the singly linked bucket list in 171 /// a folding set. 172 /// 173 class Node { 174 private: 175 // NextInFoldingSetBucket - next link in the bucket list. 176 void *NextInFoldingSetBucket; 177 178 public: 179 180 Node() : NextInFoldingSetBucket(0) {} 181 182 // Accessors 183 void *getNextInBucket() const { return NextInFoldingSetBucket; } 184 void SetNextInBucket(void *N) { NextInFoldingSetBucket = N; } 185 }; 186 187 /// RemoveNode - Remove a node from the folding set, returning true if one 188 /// was removed or false if the node was not in the folding set. 189 bool RemoveNode(Node *N); 190 191 /// GetOrInsertNode - If there is an existing simple Node exactly 192 /// equal to the specified node, return it. Otherwise, insert 'N' and return 193 /// it instead. 194 Node *GetOrInsertNode(Node *N); 195 196 /// FindNodeOrInsertPos - Look up the node specified by ID. If it exists, 197 /// return it. If not, return the insertion token that will make insertion 198 /// faster. 199 Node *FindNodeOrInsertPos(const NodeID &ID, void *&InsertPos); 200 201 /// InsertNode - Insert the specified node into the folding set, knowing that 202 /// it is not already in the folding set. InsertPos must be obtained from 203 /// FindNodeOrInsertPos. 204 void InsertNode(Node *N, void *InsertPos); 205 206private: 207 208 /// GrowHashTable - Double the size of the hash table and rehash everything. 209 /// 210 void GrowHashTable(); 211 212protected: 213 214 /// GetNodeProfile - Instantiations of the FoldingSet template implement 215 /// this function to gather data bits for the given node. 216 virtual void GetNodeProfile(NodeID &ID, Node *N) const = 0; 217}; 218 219// Convenience types to hide the implementation of the folding set. 220typedef FoldingSetImpl::Node FoldingSetNode; 221typedef FoldingSetImpl::NodeID FoldingSetNodeID; 222 223//===----------------------------------------------------------------------===// 224/// FoldingSet - This template class is used to instantiate a specialized 225/// implementation of the folding set to the node class T. T must be a 226/// subclass of FoldingSetNode and implement a Profile function. 227/// 228template<class T> class FoldingSet : public FoldingSetImpl { 229private: 230 /// GetNodeProfile - Each instantiatation of the FoldingSet needs to provide a 231 /// way to convert nodes into a unique specifier. 232 virtual void GetNodeProfile(NodeID &ID, Node *N) const { 233 T *TN = static_cast<T *>(N); 234 TN->Profile(ID); 235 } 236 237public: 238 explicit FoldingSet(unsigned Log2InitSize = 6) 239 : FoldingSetImpl(Log2InitSize) 240 {} 241 242 /// GetOrInsertNode - If there is an existing simple Node exactly 243 /// equal to the specified node, return it. Otherwise, insert 'N' and 244 /// return it instead. 245 T *GetOrInsertNode(Node *N) { 246 return static_cast<T *>(FoldingSetImpl::GetOrInsertNode(N)); 247 } 248 249 /// FindNodeOrInsertPos - Look up the node specified by ID. If it exists, 250 /// return it. If not, return the insertion token that will make insertion 251 /// faster. 252 T *FindNodeOrInsertPos(const FoldingSetNodeID &ID, void *&InsertPos) { 253 return static_cast<T *>(FoldingSetImpl::FindNodeOrInsertPos(ID, InsertPos)); 254 } 255}; 256 257} // End of namespace llvm. 258 259 260#endif 261 262