1 //===- IntervalIterator.h - Interval Iterator Declaration -------*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file defines an iterator that enumerates the intervals in a control flow 10 // graph of some sort. This iterator is parametric, allowing iterator over the 11 // following types of graphs: 12 // 13 // 1. A Function* object, composed of BasicBlock nodes. 14 // 2. An IntervalPartition& object, composed of Interval nodes. 15 // 16 // This iterator is defined to walk the control flow graph, returning intervals 17 // in depth first order. These intervals are completely filled in except for 18 // the predecessor fields (the successor information is filled in however). 19 // 20 // By default, the intervals created by this iterator are deleted after they 21 // are no longer any use to the iterator. This behavior can be changed by 22 // passing a false value into the intervals_begin() function. This causes the 23 // IOwnMem member to be set, and the intervals to not be deleted. 24 // 25 // It is only safe to use this if all of the intervals are deleted by the caller 26 // and all of the intervals are processed. However, the user of the iterator is 27 // not allowed to modify or delete the intervals until after the iterator has 28 // been used completely. The IntervalPartition class uses this functionality. 29 // 30 //===----------------------------------------------------------------------===// 31 32 #ifndef LLVM_ANALYSIS_INTERVALITERATOR_H 33 #define LLVM_ANALYSIS_INTERVALITERATOR_H 34 35 #include "llvm/ADT/GraphTraits.h" 36 #include "llvm/Analysis/Interval.h" 37 #include "llvm/Analysis/IntervalPartition.h" 38 #include "llvm/IR/CFG.h" 39 #include <algorithm> 40 #include <cassert> 41 #include <iterator> 42 #include <set> 43 #include <utility> 44 #include <vector> 45 46 namespace llvm { 47 48 class BasicBlock; 49 class Function; 50 51 // getNodeHeader - Given a source graph node and the source graph, return the 52 // BasicBlock that is the header node. This is the opposite of 53 // getSourceGraphNode. 54 inline BasicBlock *getNodeHeader(BasicBlock *BB) { return BB; } 55 inline BasicBlock *getNodeHeader(Interval *I) { return I->getHeaderNode(); } 56 57 // getSourceGraphNode - Given a BasicBlock and the source graph, return the 58 // source graph node that corresponds to the BasicBlock. This is the opposite 59 // of getNodeHeader. 60 inline BasicBlock *getSourceGraphNode(Function *, BasicBlock *BB) { 61 return BB; 62 } 63 inline Interval *getSourceGraphNode(IntervalPartition *IP, BasicBlock *BB) { 64 return IP->getBlockInterval(BB); 65 } 66 67 // addNodeToInterval - This method exists to assist the generic ProcessNode 68 // with the task of adding a node to the new interval, depending on the 69 // type of the source node. In the case of a CFG source graph (BasicBlock 70 // case), the BasicBlock itself is added to the interval. 71 inline void addNodeToInterval(Interval *Int, BasicBlock *BB) { 72 Int->Nodes.push_back(BB); 73 } 74 75 // addNodeToInterval - This method exists to assist the generic ProcessNode 76 // with the task of adding a node to the new interval, depending on the 77 // type of the source node. In the case of a CFG source graph (BasicBlock 78 // case), the BasicBlock itself is added to the interval. In the case of 79 // an IntervalPartition source graph (Interval case), all of the member 80 // BasicBlocks are added to the interval. 81 inline void addNodeToInterval(Interval *Int, Interval *I) { 82 // Add all of the nodes in I as new nodes in Int. 83 llvm::append_range(Int->Nodes, I->Nodes); 84 } 85 86 template<class NodeTy, class OrigContainer_t, class GT = GraphTraits<NodeTy *>, 87 class IGT = GraphTraits<Inverse<NodeTy *>>> 88 class IntervalIterator { 89 std::vector<std::pair<Interval *, typename Interval::succ_iterator>> IntStack; 90 std::set<BasicBlock *> Visited; 91 OrigContainer_t *OrigContainer; 92 bool IOwnMem; // If True, delete intervals when done with them 93 // See file header for conditions of use 94 95 public: 96 using iterator_category = std::forward_iterator_tag; 97 98 IntervalIterator() = default; // End iterator, empty stack 99 100 IntervalIterator(Function *M, bool OwnMemory) : IOwnMem(OwnMemory) { 101 OrigContainer = M; 102 if (!ProcessInterval(&M->front())) { 103 llvm_unreachable("ProcessInterval should never fail for first interval!"); 104 } 105 } 106 107 IntervalIterator(IntervalIterator &&x) 108 : IntStack(std::move(x.IntStack)), Visited(std::move(x.Visited)), 109 OrigContainer(x.OrigContainer), IOwnMem(x.IOwnMem) { 110 x.IOwnMem = false; 111 } 112 113 IntervalIterator(IntervalPartition &IP, bool OwnMemory) : IOwnMem(OwnMemory) { 114 OrigContainer = &IP; 115 if (!ProcessInterval(IP.getRootInterval())) { 116 llvm_unreachable("ProcessInterval should never fail for first interval!"); 117 } 118 } 119 120 ~IntervalIterator() { 121 if (IOwnMem) 122 while (!IntStack.empty()) { 123 delete operator*(); 124 IntStack.pop_back(); 125 } 126 } 127 128 bool operator==(const IntervalIterator &x) const { 129 return IntStack == x.IntStack; 130 } 131 bool operator!=(const IntervalIterator &x) const { return !(*this == x); } 132 133 const Interval *operator*() const { return IntStack.back().first; } 134 Interval *operator*() { return IntStack.back().first; } 135 const Interval *operator->() const { return operator*(); } 136 Interval *operator->() { return operator*(); } 137 138 IntervalIterator &operator++() { // Preincrement 139 assert(!IntStack.empty() && "Attempting to use interval iterator at end!"); 140 do { 141 // All of the intervals on the stack have been visited. Try visiting 142 // their successors now. 143 Interval::succ_iterator &SuccIt = IntStack.back().second, 144 EndIt = succ_end(IntStack.back().first); 145 while (SuccIt != EndIt) { // Loop over all interval succs 146 bool Done = ProcessInterval(getSourceGraphNode(OrigContainer, *SuccIt)); 147 ++SuccIt; // Increment iterator 148 if (Done) return *this; // Found a new interval! Use it! 149 } 150 151 // Free interval memory... if necessary 152 if (IOwnMem) delete IntStack.back().first; 153 154 // We ran out of successors for this interval... pop off the stack 155 IntStack.pop_back(); 156 } while (!IntStack.empty()); 157 158 return *this; 159 } 160 161 IntervalIterator operator++(int) { // Postincrement 162 IntervalIterator tmp = *this; 163 ++*this; 164 return tmp; 165 } 166 167 private: 168 // ProcessInterval - This method is used during the construction of the 169 // interval graph. It walks through the source graph, recursively creating 170 // an interval per invocation until the entire graph is covered. This uses 171 // the ProcessNode method to add all of the nodes to the interval. 172 // 173 // This method is templated because it may operate on two different source 174 // graphs: a basic block graph, or a preexisting interval graph. 175 bool ProcessInterval(NodeTy *Node) { 176 BasicBlock *Header = getNodeHeader(Node); 177 if (!Visited.insert(Header).second) 178 return false; 179 180 Interval *Int = new Interval(Header); 181 182 // Check all of our successors to see if they are in the interval... 183 for (typename GT::ChildIteratorType I = GT::child_begin(Node), 184 E = GT::child_end(Node); I != E; ++I) 185 ProcessNode(Int, getSourceGraphNode(OrigContainer, *I)); 186 187 IntStack.push_back(std::make_pair(Int, succ_begin(Int))); 188 return true; 189 } 190 191 // ProcessNode - This method is called by ProcessInterval to add nodes to the 192 // interval being constructed, and it is also called recursively as it walks 193 // the source graph. A node is added to the current interval only if all of 194 // its predecessors are already in the graph. This also takes care of keeping 195 // the successor set of an interval up to date. 196 // 197 // This method is templated because it may operate on two different source 198 // graphs: a basic block graph, or a preexisting interval graph. 199 void ProcessNode(Interval *Int, NodeTy *Node) { 200 assert(Int && "Null interval == bad!"); 201 assert(Node && "Null Node == bad!"); 202 203 BasicBlock *NodeHeader = getNodeHeader(Node); 204 205 if (Visited.count(NodeHeader)) { // Node already been visited? 206 if (Int->contains(NodeHeader)) { // Already in this interval... 207 return; 208 } else { // In other interval, add as successor 209 if (!Int->isSuccessor(NodeHeader)) // Add only if not already in set 210 Int->Successors.push_back(NodeHeader); 211 } 212 } else { // Otherwise, not in interval yet 213 for (typename IGT::ChildIteratorType I = IGT::child_begin(Node), 214 E = IGT::child_end(Node); I != E; ++I) { 215 if (!Int->contains(*I)) { // If pred not in interval, we can't be 216 if (!Int->isSuccessor(NodeHeader)) // Add only if not already in set 217 Int->Successors.push_back(NodeHeader); 218 return; // See you later 219 } 220 } 221 222 // If we get here, then all of the predecessors of BB are in the interval 223 // already. In this case, we must add BB to the interval! 224 addNodeToInterval(Int, Node); 225 Visited.insert(NodeHeader); // The node has now been visited! 226 227 if (Int->isSuccessor(NodeHeader)) { 228 // If we were in the successor list from before... remove from succ list 229 llvm::erase_value(Int->Successors, NodeHeader); 230 } 231 232 // Now that we have discovered that Node is in the interval, perhaps some 233 // of its successors are as well? 234 for (typename GT::ChildIteratorType It = GT::child_begin(Node), 235 End = GT::child_end(Node); It != End; ++It) 236 ProcessNode(Int, getSourceGraphNode(OrigContainer, *It)); 237 } 238 } 239 }; 240 241 using function_interval_iterator = IntervalIterator<BasicBlock, Function>; 242 using interval_part_interval_iterator = 243 IntervalIterator<Interval, IntervalPartition>; 244 245 inline function_interval_iterator intervals_begin(Function *F, 246 bool DeleteInts = true) { 247 return function_interval_iterator(F, DeleteInts); 248 } 249 inline function_interval_iterator intervals_end(Function *) { 250 return function_interval_iterator(); 251 } 252 253 inline interval_part_interval_iterator 254 intervals_begin(IntervalPartition &IP, bool DeleteIntervals = true) { 255 return interval_part_interval_iterator(IP, DeleteIntervals); 256 } 257 258 inline interval_part_interval_iterator intervals_end(IntervalPartition &IP) { 259 return interval_part_interval_iterator(); 260 } 261 262 } // end namespace llvm 263 264 #endif // LLVM_ANALYSIS_INTERVALITERATOR_H 265