ExplodedGraph.cpp revision 218893
1//=-- ExplodedGraph.cpp - Local, Path-Sens. "Exploded Graph" -*- C++ -*------=// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file defines the template classes ExplodedNode and ExplodedGraph, 11// which represent a path-sensitive, intra-procedural "exploded graph." 12// 13//===----------------------------------------------------------------------===// 14 15#include "clang/StaticAnalyzer/Core/PathSensitive/ExplodedGraph.h" 16#include "clang/StaticAnalyzer/Core/PathSensitive/GRState.h" 17#include "clang/AST/Stmt.h" 18#include "llvm/ADT/DenseSet.h" 19#include "llvm/ADT/DenseMap.h" 20#include "llvm/ADT/SmallVector.h" 21#include <vector> 22 23using namespace clang; 24using namespace ento; 25 26//===----------------------------------------------------------------------===// 27// Node auditing. 28//===----------------------------------------------------------------------===// 29 30// An out of line virtual method to provide a home for the class vtable. 31ExplodedNode::Auditor::~Auditor() {} 32 33#ifndef NDEBUG 34static ExplodedNode::Auditor* NodeAuditor = 0; 35#endif 36 37void ExplodedNode::SetAuditor(ExplodedNode::Auditor* A) { 38#ifndef NDEBUG 39 NodeAuditor = A; 40#endif 41} 42 43//===----------------------------------------------------------------------===// 44// Cleanup. 45//===----------------------------------------------------------------------===// 46 47typedef std::vector<ExplodedNode*> NodeList; 48static inline NodeList*& getNodeList(void *&p) { return (NodeList*&) p; } 49 50ExplodedGraph::~ExplodedGraph() { 51 if (reclaimNodes) { 52 delete getNodeList(recentlyAllocatedNodes); 53 delete getNodeList(freeNodes); 54 } 55} 56 57//===----------------------------------------------------------------------===// 58// Node reclamation. 59//===----------------------------------------------------------------------===// 60 61void ExplodedGraph::reclaimRecentlyAllocatedNodes() { 62 if (!recentlyAllocatedNodes) 63 return; 64 NodeList &nl = *getNodeList(recentlyAllocatedNodes); 65 66 // Reclaimn all nodes that match *all* the following criteria: 67 // 68 // (1) 1 predecessor (that has one successor) 69 // (2) 1 successor (that has one predecessor) 70 // (3) The ProgramPoint is for a PostStmt. 71 // (4) There is no 'tag' for the ProgramPoint. 72 // (5) The 'store' is the same as the predecessor. 73 // (6) The 'GDM' is the same as the predecessor. 74 // (7) The LocationContext is the same as the predecessor. 75 // (8) The PostStmt is for a non-CFGElement expression. 76 77 for (NodeList::iterator i = nl.begin(), e = nl.end() ; i != e; ++i) { 78 ExplodedNode *node = *i; 79 80 // Conditions 1 and 2. 81 if (node->pred_size() != 1 || node->succ_size() != 1) 82 continue; 83 84 ExplodedNode *pred = *(node->pred_begin()); 85 if (pred->succ_size() != 1) 86 continue; 87 88 ExplodedNode *succ = *(node->succ_begin()); 89 if (succ->pred_size() != 1) 90 continue; 91 92 // Condition 3. 93 ProgramPoint progPoint = node->getLocation(); 94 if (!isa<PostStmt>(progPoint)) 95 continue; 96 97 // Condition 4. 98 PostStmt ps = cast<PostStmt>(progPoint); 99 if (ps.getTag() || isa<PostStmtCustom>(ps)) 100 continue; 101 102 if (isa<BinaryOperator>(ps.getStmt())) 103 continue; 104 105 // Conditions 5, 6, and 7. 106 const GRState *state = node->getState(); 107 const GRState *pred_state = pred->getState(); 108 if (state->store != pred_state->store || state->GDM != pred_state->GDM || 109 progPoint.getLocationContext() != pred->getLocationContext()) 110 continue; 111 112 // Condition 8. 113 if (node->getCFG().isBlkExpr(ps.getStmt())) 114 continue; 115 116 // If we reach here, we can remove the node. This means: 117 // (a) changing the predecessors successor to the successor of this node 118 // (b) changing the successors predecessor to the predecessor of this node 119 // (c) Putting 'node' onto freeNodes. 120 pred->replaceSuccessor(succ); 121 succ->replacePredecessor(pred); 122 if (!freeNodes) 123 freeNodes = new NodeList(); 124 getNodeList(freeNodes)->push_back(node); 125 Nodes.RemoveNode(node); 126 --NumNodes; 127 node->~ExplodedNode(); 128 } 129 130 nl.clear(); 131} 132 133//===----------------------------------------------------------------------===// 134// ExplodedNode. 135//===----------------------------------------------------------------------===// 136 137static inline BumpVector<ExplodedNode*>& getVector(void* P) { 138 return *reinterpret_cast<BumpVector<ExplodedNode*>*>(P); 139} 140 141void ExplodedNode::addPredecessor(ExplodedNode* V, ExplodedGraph &G) { 142 assert (!V->isSink()); 143 Preds.addNode(V, G); 144 V->Succs.addNode(this, G); 145#ifndef NDEBUG 146 if (NodeAuditor) NodeAuditor->AddEdge(V, this); 147#endif 148} 149 150void ExplodedNode::NodeGroup::replaceNode(ExplodedNode *node) { 151 assert(getKind() == Size1); 152 P = reinterpret_cast<uintptr_t>(node); 153 assert(getKind() == Size1); 154} 155 156void ExplodedNode::NodeGroup::addNode(ExplodedNode* N, ExplodedGraph &G) { 157 assert((reinterpret_cast<uintptr_t>(N) & Mask) == 0x0); 158 assert(!getFlag()); 159 160 if (getKind() == Size1) { 161 if (ExplodedNode* NOld = getNode()) { 162 BumpVectorContext &Ctx = G.getNodeAllocator(); 163 BumpVector<ExplodedNode*> *V = 164 G.getAllocator().Allocate<BumpVector<ExplodedNode*> >(); 165 new (V) BumpVector<ExplodedNode*>(Ctx, 4); 166 167 assert((reinterpret_cast<uintptr_t>(V) & Mask) == 0x0); 168 V->push_back(NOld, Ctx); 169 V->push_back(N, Ctx); 170 P = reinterpret_cast<uintptr_t>(V) | SizeOther; 171 assert(getPtr() == (void*) V); 172 assert(getKind() == SizeOther); 173 } 174 else { 175 P = reinterpret_cast<uintptr_t>(N); 176 assert(getKind() == Size1); 177 } 178 } 179 else { 180 assert(getKind() == SizeOther); 181 getVector(getPtr()).push_back(N, G.getNodeAllocator()); 182 } 183} 184 185unsigned ExplodedNode::NodeGroup::size() const { 186 if (getFlag()) 187 return 0; 188 189 if (getKind() == Size1) 190 return getNode() ? 1 : 0; 191 else 192 return getVector(getPtr()).size(); 193} 194 195ExplodedNode **ExplodedNode::NodeGroup::begin() const { 196 if (getFlag()) 197 return NULL; 198 199 if (getKind() == Size1) 200 return (ExplodedNode**) (getPtr() ? &P : NULL); 201 else 202 return const_cast<ExplodedNode**>(&*(getVector(getPtr()).begin())); 203} 204 205ExplodedNode** ExplodedNode::NodeGroup::end() const { 206 if (getFlag()) 207 return NULL; 208 209 if (getKind() == Size1) 210 return (ExplodedNode**) (getPtr() ? &P+1 : NULL); 211 else { 212 // Dereferencing end() is undefined behaviour. The vector is not empty, so 213 // we can dereference the last elem and then add 1 to the result. 214 return const_cast<ExplodedNode**>(getVector(getPtr()).end()); 215 } 216} 217 218ExplodedNode *ExplodedGraph::getNode(const ProgramPoint& L, 219 const GRState* State, bool* IsNew) { 220 // Profile 'State' to determine if we already have an existing node. 221 llvm::FoldingSetNodeID profile; 222 void* InsertPos = 0; 223 224 NodeTy::Profile(profile, L, State); 225 NodeTy* V = Nodes.FindNodeOrInsertPos(profile, InsertPos); 226 227 if (!V) { 228 if (freeNodes && !getNodeList(freeNodes)->empty()) { 229 NodeList *nl = getNodeList(freeNodes); 230 V = nl->back(); 231 nl->pop_back(); 232 } 233 else { 234 // Allocate a new node. 235 V = (NodeTy*) getAllocator().Allocate<NodeTy>(); 236 } 237 238 new (V) NodeTy(L, State); 239 240 if (reclaimNodes) { 241 if (!recentlyAllocatedNodes) 242 recentlyAllocatedNodes = new NodeList(); 243 getNodeList(recentlyAllocatedNodes)->push_back(V); 244 } 245 246 // Insert the node into the node set and return it. 247 Nodes.InsertNode(V, InsertPos); 248 249 ++NumNodes; 250 251 if (IsNew) *IsNew = true; 252 } 253 else 254 if (IsNew) *IsNew = false; 255 256 return V; 257} 258 259std::pair<ExplodedGraph*, InterExplodedGraphMap*> 260ExplodedGraph::Trim(const NodeTy* const* NBeg, const NodeTy* const* NEnd, 261 llvm::DenseMap<const void*, const void*> *InverseMap) const { 262 263 if (NBeg == NEnd) 264 return std::make_pair((ExplodedGraph*) 0, 265 (InterExplodedGraphMap*) 0); 266 267 assert (NBeg < NEnd); 268 269 llvm::OwningPtr<InterExplodedGraphMap> M(new InterExplodedGraphMap()); 270 271 ExplodedGraph* G = TrimInternal(NBeg, NEnd, M.get(), InverseMap); 272 273 return std::make_pair(static_cast<ExplodedGraph*>(G), M.take()); 274} 275 276ExplodedGraph* 277ExplodedGraph::TrimInternal(const ExplodedNode* const* BeginSources, 278 const ExplodedNode* const* EndSources, 279 InterExplodedGraphMap* M, 280 llvm::DenseMap<const void*, const void*> *InverseMap) const { 281 282 typedef llvm::DenseSet<const ExplodedNode*> Pass1Ty; 283 Pass1Ty Pass1; 284 285 typedef llvm::DenseMap<const ExplodedNode*, ExplodedNode*> Pass2Ty; 286 Pass2Ty& Pass2 = M->M; 287 288 llvm::SmallVector<const ExplodedNode*, 10> WL1, WL2; 289 290 // ===- Pass 1 (reverse DFS) -=== 291 for (const ExplodedNode* const* I = BeginSources; I != EndSources; ++I) { 292 assert(*I); 293 WL1.push_back(*I); 294 } 295 296 // Process the first worklist until it is empty. Because it is a std::list 297 // it acts like a FIFO queue. 298 while (!WL1.empty()) { 299 const ExplodedNode *N = WL1.back(); 300 WL1.pop_back(); 301 302 // Have we already visited this node? If so, continue to the next one. 303 if (Pass1.count(N)) 304 continue; 305 306 // Otherwise, mark this node as visited. 307 Pass1.insert(N); 308 309 // If this is a root enqueue it to the second worklist. 310 if (N->Preds.empty()) { 311 WL2.push_back(N); 312 continue; 313 } 314 315 // Visit our predecessors and enqueue them. 316 for (ExplodedNode** I=N->Preds.begin(), **E=N->Preds.end(); I!=E; ++I) 317 WL1.push_back(*I); 318 } 319 320 // We didn't hit a root? Return with a null pointer for the new graph. 321 if (WL2.empty()) 322 return 0; 323 324 // Create an empty graph. 325 ExplodedGraph* G = MakeEmptyGraph(); 326 327 // ===- Pass 2 (forward DFS to construct the new graph) -=== 328 while (!WL2.empty()) { 329 const ExplodedNode* N = WL2.back(); 330 WL2.pop_back(); 331 332 // Skip this node if we have already processed it. 333 if (Pass2.find(N) != Pass2.end()) 334 continue; 335 336 // Create the corresponding node in the new graph and record the mapping 337 // from the old node to the new node. 338 ExplodedNode* NewN = G->getNode(N->getLocation(), N->State, NULL); 339 Pass2[N] = NewN; 340 341 // Also record the reverse mapping from the new node to the old node. 342 if (InverseMap) (*InverseMap)[NewN] = N; 343 344 // If this node is a root, designate it as such in the graph. 345 if (N->Preds.empty()) 346 G->addRoot(NewN); 347 348 // In the case that some of the intended predecessors of NewN have already 349 // been created, we should hook them up as predecessors. 350 351 // Walk through the predecessors of 'N' and hook up their corresponding 352 // nodes in the new graph (if any) to the freshly created node. 353 for (ExplodedNode **I=N->Preds.begin(), **E=N->Preds.end(); I!=E; ++I) { 354 Pass2Ty::iterator PI = Pass2.find(*I); 355 if (PI == Pass2.end()) 356 continue; 357 358 NewN->addPredecessor(PI->second, *G); 359 } 360 361 // In the case that some of the intended successors of NewN have already 362 // been created, we should hook them up as successors. Otherwise, enqueue 363 // the new nodes from the original graph that should have nodes created 364 // in the new graph. 365 for (ExplodedNode **I=N->Succs.begin(), **E=N->Succs.end(); I!=E; ++I) { 366 Pass2Ty::iterator PI = Pass2.find(*I); 367 if (PI != Pass2.end()) { 368 PI->second->addPredecessor(NewN, *G); 369 continue; 370 } 371 372 // Enqueue nodes to the worklist that were marked during pass 1. 373 if (Pass1.count(*I)) 374 WL2.push_back(*I); 375 } 376 377 // Finally, explictly mark all nodes without any successors as sinks. 378 if (N->isSink()) 379 NewN->markAsSink(); 380 } 381 382 return G; 383} 384 385ExplodedNode* 386InterExplodedGraphMap::getMappedNode(const ExplodedNode* N) const { 387 llvm::DenseMap<const ExplodedNode*, ExplodedNode*>::const_iterator I = 388 M.find(N); 389 390 return I == M.end() ? 0 : I->second; 391} 392 393