ExplodedGraph.cpp revision 437ee81e54f39c2363d5fe0ea155604c28adc615
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/ProgramState.h" 17#include "clang/AST/Stmt.h" 18#include "clang/AST/ParentMap.h" 19#include "llvm/ADT/DenseSet.h" 20#include "llvm/ADT/DenseMap.h" 21#include "llvm/ADT/SmallVector.h" 22#include <vector> 23 24using namespace clang; 25using namespace ento; 26 27//===----------------------------------------------------------------------===// 28// Node auditing. 29//===----------------------------------------------------------------------===// 30 31// An out of line virtual method to provide a home for the class vtable. 32ExplodedNode::Auditor::~Auditor() {} 33 34#ifndef NDEBUG 35static ExplodedNode::Auditor* NodeAuditor = 0; 36#endif 37 38void ExplodedNode::SetAuditor(ExplodedNode::Auditor* A) { 39#ifndef NDEBUG 40 NodeAuditor = A; 41#endif 42} 43 44//===----------------------------------------------------------------------===// 45// Cleanup. 46//===----------------------------------------------------------------------===// 47 48ExplodedGraph::ExplodedGraph() 49 : NumNodes(0), reclaimNodes(false) {} 50 51ExplodedGraph::~ExplodedGraph() {} 52 53//===----------------------------------------------------------------------===// 54// Node reclamation. 55//===----------------------------------------------------------------------===// 56 57bool ExplodedGraph::shouldCollect(const ExplodedNode *node) { 58 // Reclaimn all nodes that match *all* the following criteria: 59 // 60 // (1) 1 predecessor (that has one successor) 61 // (2) 1 successor (that has one predecessor) 62 // (3) The ProgramPoint is for a PostStmt. 63 // (4) There is no 'tag' for the ProgramPoint. 64 // (5) The 'store' is the same as the predecessor. 65 // (6) The 'GDM' is the same as the predecessor. 66 // (7) The LocationContext is the same as the predecessor. 67 // (8) The PostStmt is for a non-consumed Stmt or Expr. 68 69 // Conditions 1 and 2. 70 if (node->pred_size() != 1 || node->succ_size() != 1) 71 return false; 72 73 const ExplodedNode *pred = *(node->pred_begin()); 74 if (pred->succ_size() != 1) 75 return false; 76 77 const ExplodedNode *succ = *(node->succ_begin()); 78 if (succ->pred_size() != 1) 79 return false; 80 81 // Condition 3. 82 ProgramPoint progPoint = node->getLocation(); 83 if (!isa<PostStmt>(progPoint) || 84 (isa<CallEnter>(progPoint) || isa<CallExit>(progPoint))) 85 return false; 86 87 // Condition 4. 88 PostStmt ps = cast<PostStmt>(progPoint); 89 if (ps.getTag()) 90 return false; 91 92 if (isa<BinaryOperator>(ps.getStmt())) 93 return false; 94 95 // Conditions 5, 6, and 7. 96 ProgramStateRef state = node->getState(); 97 ProgramStateRef pred_state = pred->getState(); 98 if (state->store != pred_state->store || state->GDM != pred_state->GDM || 99 progPoint.getLocationContext() != pred->getLocationContext()) 100 return false; 101 102 // Condition 8. 103 if (const Expr *Ex = dyn_cast<Expr>(ps.getStmt())) { 104 ParentMap &PM = progPoint.getLocationContext()->getParentMap(); 105 if (!PM.isConsumedExpr(Ex)) 106 return false; 107 } 108 109 return true; 110} 111 112void ExplodedGraph::collectNode(ExplodedNode *node) { 113 // Removing a node means: 114 // (a) changing the predecessors successor to the successor of this node 115 // (b) changing the successors predecessor to the predecessor of this node 116 // (c) Putting 'node' onto freeNodes. 117 assert(node->pred_size() == 1 || node->succ_size() == 1); 118 ExplodedNode *pred = *(node->pred_begin()); 119 ExplodedNode *succ = *(node->succ_begin()); 120 pred->replaceSuccessor(succ); 121 succ->replacePredecessor(pred); 122 FreeNodes.push_back(node); 123 Nodes.RemoveNode(node); 124 --NumNodes; 125 node->~ExplodedNode(); 126} 127 128void ExplodedGraph::reclaimChangedNodes() { 129 if (ChangedNodes.empty()) 130 return; 131 132 for (llvm::DenseSet<ExplodedNode*>::iterator it = 133 ChangedNodes.begin(), et = ChangedNodes.end(); 134 it != et; ++it) { 135 ExplodedNode *node = *it; 136 if (shouldCollect(node)) 137 collectNode(node); 138 } 139 ChangedNodes.clear(); 140} 141 142//===----------------------------------------------------------------------===// 143// ExplodedNode. 144//===----------------------------------------------------------------------===// 145 146static inline BumpVector<ExplodedNode*>& getVector(void *P) { 147 return *reinterpret_cast<BumpVector<ExplodedNode*>*>(P); 148} 149 150void ExplodedNode::addPredecessor(ExplodedNode *V, ExplodedGraph &G) { 151 assert (!V->isSink()); 152 Preds.addNode(V, G); 153 V->Succs.addNode(this, G); 154 if (G.reclaimNodes) { 155 if (Succs.size() == 1 && Preds.size() == 1) 156 G.ChangedNodes.insert(this); 157 if (V->Succs.size() == 1 && V->Preds.size() == 1) 158 G.ChangedNodes.insert(V); 159 } 160#ifndef NDEBUG 161 if (NodeAuditor) NodeAuditor->AddEdge(V, this); 162#endif 163} 164 165void ExplodedNode::NodeGroup::replaceNode(ExplodedNode *node) { 166 assert(getKind() == Size1); 167 P = reinterpret_cast<uintptr_t>(node); 168 assert(getKind() == Size1); 169} 170 171void ExplodedNode::NodeGroup::addNode(ExplodedNode *N, ExplodedGraph &G) { 172 assert((reinterpret_cast<uintptr_t>(N) & Mask) == 0x0); 173 assert(!getFlag()); 174 175 if (getKind() == Size1) { 176 if (ExplodedNode *NOld = getNode()) { 177 BumpVectorContext &Ctx = G.getNodeAllocator(); 178 BumpVector<ExplodedNode*> *V = 179 G.getAllocator().Allocate<BumpVector<ExplodedNode*> >(); 180 new (V) BumpVector<ExplodedNode*>(Ctx, 4); 181 182 assert((reinterpret_cast<uintptr_t>(V) & Mask) == 0x0); 183 V->push_back(NOld, Ctx); 184 V->push_back(N, Ctx); 185 P = reinterpret_cast<uintptr_t>(V) | SizeOther; 186 assert(getPtr() == (void*) V); 187 assert(getKind() == SizeOther); 188 } 189 else { 190 P = reinterpret_cast<uintptr_t>(N); 191 assert(getKind() == Size1); 192 } 193 } 194 else { 195 assert(getKind() == SizeOther); 196 getVector(getPtr()).push_back(N, G.getNodeAllocator()); 197 } 198} 199 200unsigned ExplodedNode::NodeGroup::size() const { 201 if (getFlag()) 202 return 0; 203 204 if (getKind() == Size1) 205 return getNode() ? 1 : 0; 206 else 207 return getVector(getPtr()).size(); 208} 209 210ExplodedNode **ExplodedNode::NodeGroup::begin() const { 211 if (getFlag()) 212 return NULL; 213 214 if (getKind() == Size1) 215 return (ExplodedNode**) (getPtr() ? &P : NULL); 216 else 217 return const_cast<ExplodedNode**>(&*(getVector(getPtr()).begin())); 218} 219 220ExplodedNode** ExplodedNode::NodeGroup::end() const { 221 if (getFlag()) 222 return NULL; 223 224 if (getKind() == Size1) 225 return (ExplodedNode**) (getPtr() ? &P+1 : NULL); 226 else { 227 // Dereferencing end() is undefined behaviour. The vector is not empty, so 228 // we can dereference the last elem and then add 1 to the result. 229 return const_cast<ExplodedNode**>(getVector(getPtr()).end()); 230 } 231} 232 233ExplodedNode *ExplodedGraph::getNode(const ProgramPoint &L, 234 ProgramStateRef State, 235 bool IsSink, 236 bool* IsNew) { 237 // Profile 'State' to determine if we already have an existing node. 238 llvm::FoldingSetNodeID profile; 239 void *InsertPos = 0; 240 241 NodeTy::Profile(profile, L, State, IsSink); 242 NodeTy* V = Nodes.FindNodeOrInsertPos(profile, InsertPos); 243 244 if (!V) { 245 if (!FreeNodes.empty()) { 246 V = FreeNodes.back(); 247 FreeNodes.pop_back(); 248 } 249 else { 250 // Allocate a new node. 251 V = (NodeTy*) getAllocator().Allocate<NodeTy>(); 252 } 253 254 new (V) NodeTy(L, State, IsSink); 255 256 // Insert the node into the node set and return it. 257 Nodes.InsertNode(V, InsertPos); 258 ++NumNodes; 259 260 if (IsNew) *IsNew = true; 261 } 262 else 263 if (IsNew) *IsNew = false; 264 265 return V; 266} 267 268std::pair<ExplodedGraph*, InterExplodedGraphMap*> 269ExplodedGraph::Trim(const NodeTy* const* NBeg, const NodeTy* const* NEnd, 270 llvm::DenseMap<const void*, const void*> *InverseMap) const { 271 272 if (NBeg == NEnd) 273 return std::make_pair((ExplodedGraph*) 0, 274 (InterExplodedGraphMap*) 0); 275 276 assert (NBeg < NEnd); 277 278 OwningPtr<InterExplodedGraphMap> M(new InterExplodedGraphMap()); 279 280 ExplodedGraph* G = TrimInternal(NBeg, NEnd, M.get(), InverseMap); 281 282 return std::make_pair(static_cast<ExplodedGraph*>(G), M.take()); 283} 284 285ExplodedGraph* 286ExplodedGraph::TrimInternal(const ExplodedNode* const* BeginSources, 287 const ExplodedNode* const* EndSources, 288 InterExplodedGraphMap* M, 289 llvm::DenseMap<const void*, const void*> *InverseMap) const { 290 291 typedef llvm::DenseSet<const ExplodedNode*> Pass1Ty; 292 Pass1Ty Pass1; 293 294 typedef llvm::DenseMap<const ExplodedNode*, ExplodedNode*> Pass2Ty; 295 Pass2Ty& Pass2 = M->M; 296 297 SmallVector<const ExplodedNode*, 10> WL1, WL2; 298 299 // ===- Pass 1 (reverse DFS) -=== 300 for (const ExplodedNode* const* I = BeginSources; I != EndSources; ++I) { 301 assert(*I); 302 WL1.push_back(*I); 303 } 304 305 // Process the first worklist until it is empty. Because it is a std::list 306 // it acts like a FIFO queue. 307 while (!WL1.empty()) { 308 const ExplodedNode *N = WL1.back(); 309 WL1.pop_back(); 310 311 // Have we already visited this node? If so, continue to the next one. 312 if (Pass1.count(N)) 313 continue; 314 315 // Otherwise, mark this node as visited. 316 Pass1.insert(N); 317 318 // If this is a root enqueue it to the second worklist. 319 if (N->Preds.empty()) { 320 WL2.push_back(N); 321 continue; 322 } 323 324 // Visit our predecessors and enqueue them. 325 for (ExplodedNode** I=N->Preds.begin(), **E=N->Preds.end(); I!=E; ++I) 326 WL1.push_back(*I); 327 } 328 329 // We didn't hit a root? Return with a null pointer for the new graph. 330 if (WL2.empty()) 331 return 0; 332 333 // Create an empty graph. 334 ExplodedGraph* G = MakeEmptyGraph(); 335 336 // ===- Pass 2 (forward DFS to construct the new graph) -=== 337 while (!WL2.empty()) { 338 const ExplodedNode *N = WL2.back(); 339 WL2.pop_back(); 340 341 // Skip this node if we have already processed it. 342 if (Pass2.find(N) != Pass2.end()) 343 continue; 344 345 // Create the corresponding node in the new graph and record the mapping 346 // from the old node to the new node. 347 ExplodedNode *NewN = G->getNode(N->getLocation(), N->State, N->isSink(), 0); 348 Pass2[N] = NewN; 349 350 // Also record the reverse mapping from the new node to the old node. 351 if (InverseMap) (*InverseMap)[NewN] = N; 352 353 // If this node is a root, designate it as such in the graph. 354 if (N->Preds.empty()) 355 G->addRoot(NewN); 356 357 // In the case that some of the intended predecessors of NewN have already 358 // been created, we should hook them up as predecessors. 359 360 // Walk through the predecessors of 'N' and hook up their corresponding 361 // nodes in the new graph (if any) to the freshly created node. 362 for (ExplodedNode **I=N->Preds.begin(), **E=N->Preds.end(); I!=E; ++I) { 363 Pass2Ty::iterator PI = Pass2.find(*I); 364 if (PI == Pass2.end()) 365 continue; 366 367 NewN->addPredecessor(PI->second, *G); 368 } 369 370 // In the case that some of the intended successors of NewN have already 371 // been created, we should hook them up as successors. Otherwise, enqueue 372 // the new nodes from the original graph that should have nodes created 373 // in the new graph. 374 for (ExplodedNode **I=N->Succs.begin(), **E=N->Succs.end(); I!=E; ++I) { 375 Pass2Ty::iterator PI = Pass2.find(*I); 376 if (PI != Pass2.end()) { 377 PI->second->addPredecessor(NewN, *G); 378 continue; 379 } 380 381 // Enqueue nodes to the worklist that were marked during pass 1. 382 if (Pass1.count(*I)) 383 WL2.push_back(*I); 384 } 385 } 386 387 return G; 388} 389 390void InterExplodedGraphMap::anchor() { } 391 392ExplodedNode* 393InterExplodedGraphMap::getMappedNode(const ExplodedNode *N) const { 394 llvm::DenseMap<const ExplodedNode*, ExplodedNode*>::const_iterator I = 395 M.find(N); 396 397 return I == M.end() ? 0 : I->second; 398} 399 400