CoreEngine.cpp revision e62f048960645b79363408fdead53fec2a063c52
1//==- CoreEngine.cpp - Path-Sensitive Dataflow Engine ------------*- 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 a generic engine for intraprocedural, path-sensitive, 11// dataflow analysis via graph reachability engine. 12// 13//===----------------------------------------------------------------------===// 14 15#define DEBUG_TYPE "CoreEngine" 16 17#include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h" 18#include "clang/StaticAnalyzer/Core/PathSensitive/CoreEngine.h" 19#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h" 20#include "clang/Index/TranslationUnit.h" 21#include "clang/AST/Expr.h" 22#include "clang/AST/StmtCXX.h" 23#include "llvm/Support/Casting.h" 24#include "llvm/ADT/DenseMap.h" 25#include "llvm/ADT/Statistic.h" 26 27using namespace clang; 28using namespace ento; 29 30STATISTIC(NumReachedMaxSteps, 31 "The # of times we reached the max number of steps."); 32STATISTIC(NumPathsExplored, 33 "The # of paths explored by the analyzer."); 34 35//===----------------------------------------------------------------------===// 36// Worklist classes for exploration of reachable states. 37//===----------------------------------------------------------------------===// 38 39WorkList::Visitor::~Visitor() {} 40 41namespace { 42class DFS : public WorkList { 43 SmallVector<WorkListUnit,20> Stack; 44public: 45 virtual bool hasWork() const { 46 return !Stack.empty(); 47 } 48 49 virtual void enqueue(const WorkListUnit& U) { 50 Stack.push_back(U); 51 } 52 53 virtual WorkListUnit dequeue() { 54 assert (!Stack.empty()); 55 const WorkListUnit& U = Stack.back(); 56 Stack.pop_back(); // This technically "invalidates" U, but we are fine. 57 return U; 58 } 59 60 virtual bool visitItemsInWorkList(Visitor &V) { 61 for (SmallVectorImpl<WorkListUnit>::iterator 62 I = Stack.begin(), E = Stack.end(); I != E; ++I) { 63 if (V.visit(*I)) 64 return true; 65 } 66 return false; 67 } 68}; 69 70class BFS : public WorkList { 71 std::deque<WorkListUnit> Queue; 72public: 73 virtual bool hasWork() const { 74 return !Queue.empty(); 75 } 76 77 virtual void enqueue(const WorkListUnit& U) { 78 Queue.push_front(U); 79 } 80 81 virtual WorkListUnit dequeue() { 82 WorkListUnit U = Queue.front(); 83 Queue.pop_front(); 84 return U; 85 } 86 87 virtual bool visitItemsInWorkList(Visitor &V) { 88 for (std::deque<WorkListUnit>::iterator 89 I = Queue.begin(), E = Queue.end(); I != E; ++I) { 90 if (V.visit(*I)) 91 return true; 92 } 93 return false; 94 } 95}; 96 97} // end anonymous namespace 98 99// Place the dstor for WorkList here because it contains virtual member 100// functions, and we the code for the dstor generated in one compilation unit. 101WorkList::~WorkList() {} 102 103WorkList *WorkList::makeDFS() { return new DFS(); } 104WorkList *WorkList::makeBFS() { return new BFS(); } 105 106namespace { 107 class BFSBlockDFSContents : public WorkList { 108 std::deque<WorkListUnit> Queue; 109 SmallVector<WorkListUnit,20> Stack; 110 public: 111 virtual bool hasWork() const { 112 return !Queue.empty() || !Stack.empty(); 113 } 114 115 virtual void enqueue(const WorkListUnit& U) { 116 if (isa<BlockEntrance>(U.getNode()->getLocation())) 117 Queue.push_front(U); 118 else 119 Stack.push_back(U); 120 } 121 122 virtual WorkListUnit dequeue() { 123 // Process all basic blocks to completion. 124 if (!Stack.empty()) { 125 const WorkListUnit& U = Stack.back(); 126 Stack.pop_back(); // This technically "invalidates" U, but we are fine. 127 return U; 128 } 129 130 assert(!Queue.empty()); 131 // Don't use const reference. The subsequent pop_back() might make it 132 // unsafe. 133 WorkListUnit U = Queue.front(); 134 Queue.pop_front(); 135 return U; 136 } 137 virtual bool visitItemsInWorkList(Visitor &V) { 138 for (SmallVectorImpl<WorkListUnit>::iterator 139 I = Stack.begin(), E = Stack.end(); I != E; ++I) { 140 if (V.visit(*I)) 141 return true; 142 } 143 for (std::deque<WorkListUnit>::iterator 144 I = Queue.begin(), E = Queue.end(); I != E; ++I) { 145 if (V.visit(*I)) 146 return true; 147 } 148 return false; 149 } 150 151 }; 152} // end anonymous namespace 153 154WorkList* WorkList::makeBFSBlockDFSContents() { 155 return new BFSBlockDFSContents(); 156} 157 158//===----------------------------------------------------------------------===// 159// Core analysis engine. 160//===----------------------------------------------------------------------===// 161 162/// ExecuteWorkList - Run the worklist algorithm for a maximum number of steps. 163bool CoreEngine::ExecuteWorkList(const LocationContext *L, unsigned Steps, 164 ProgramStateRef InitState) { 165 166 if (G->num_roots() == 0) { // Initialize the analysis by constructing 167 // the root if none exists. 168 169 const CFGBlock *Entry = &(L->getCFG()->getEntry()); 170 171 assert (Entry->empty() && 172 "Entry block must be empty."); 173 174 assert (Entry->succ_size() == 1 && 175 "Entry block must have 1 successor."); 176 177 // Mark the entry block as visited. 178 FunctionSummaries->markVisitedBasicBlock(Entry->getBlockID(), 179 L->getDecl(), 180 L->getCFG()->getNumBlockIDs()); 181 182 // Get the solitary successor. 183 const CFGBlock *Succ = *(Entry->succ_begin()); 184 185 // Construct an edge representing the 186 // starting location in the function. 187 BlockEdge StartLoc(Entry, Succ, L); 188 189 // Set the current block counter to being empty. 190 WList->setBlockCounter(BCounterFactory.GetEmptyCounter()); 191 192 if (!InitState) 193 // Generate the root. 194 generateNode(StartLoc, SubEng.getInitialState(L), 0); 195 else 196 generateNode(StartLoc, InitState, 0); 197 } 198 199 // Check if we have a steps limit 200 bool UnlimitedSteps = Steps == 0; 201 202 while (WList->hasWork()) { 203 if (!UnlimitedSteps) { 204 if (Steps == 0) { 205 NumReachedMaxSteps++; 206 break; 207 } 208 --Steps; 209 } 210 211 const WorkListUnit& WU = WList->dequeue(); 212 213 // Set the current block counter. 214 WList->setBlockCounter(WU.getBlockCounter()); 215 216 // Retrieve the node. 217 ExplodedNode *Node = WU.getNode(); 218 219 dispatchWorkItem(Node, Node->getLocation(), WU); 220 } 221 SubEng.processEndWorklist(hasWorkRemaining()); 222 return WList->hasWork(); 223} 224 225void CoreEngine::dispatchWorkItem(ExplodedNode* Pred, ProgramPoint Loc, 226 const WorkListUnit& WU) { 227 // Dispatch on the location type. 228 switch (Loc.getKind()) { 229 case ProgramPoint::BlockEdgeKind: 230 HandleBlockEdge(cast<BlockEdge>(Loc), Pred); 231 break; 232 233 case ProgramPoint::BlockEntranceKind: 234 HandleBlockEntrance(cast<BlockEntrance>(Loc), Pred); 235 break; 236 237 case ProgramPoint::BlockExitKind: 238 assert (false && "BlockExit location never occur in forward analysis."); 239 break; 240 241 case ProgramPoint::CallEnterKind: { 242 CallEnter CEnter = cast<CallEnter>(Loc); 243 if (AnalyzedCallees) 244 if (const CallExpr* CE = 245 dyn_cast_or_null<CallExpr>(CEnter.getCallExpr())) 246 if (const Decl *CD = CE->getCalleeDecl()) 247 AnalyzedCallees->insert(CD); 248 SubEng.processCallEnter(CEnter, Pred); 249 break; 250 } 251 252 case ProgramPoint::CallExitKind: 253 SubEng.processCallExit(Pred); 254 break; 255 256 case ProgramPoint::EpsilonKind: { 257 assert(Pred->hasSinglePred() && 258 "Assume epsilon has exactly one predecessor by construction"); 259 ExplodedNode *PNode = Pred->getFirstPred(); 260 dispatchWorkItem(Pred, PNode->getLocation(), WU); 261 break; 262 } 263 default: 264 assert(isa<PostStmt>(Loc) || 265 isa<PostInitializer>(Loc)); 266 HandlePostStmt(WU.getBlock(), WU.getIndex(), Pred); 267 break; 268 } 269} 270 271bool CoreEngine::ExecuteWorkListWithInitialState(const LocationContext *L, 272 unsigned Steps, 273 ProgramStateRef InitState, 274 ExplodedNodeSet &Dst) { 275 bool DidNotFinish = ExecuteWorkList(L, Steps, InitState); 276 for (ExplodedGraph::eop_iterator I = G->eop_begin(), 277 E = G->eop_end(); I != E; ++I) { 278 Dst.Add(*I); 279 } 280 return DidNotFinish; 281} 282 283void CoreEngine::HandleBlockEdge(const BlockEdge &L, ExplodedNode *Pred) { 284 285 const CFGBlock *Blk = L.getDst(); 286 NodeBuilderContext BuilderCtx(*this, Blk, Pred); 287 288 // Mark this block as visited. 289 const LocationContext *LC = Pred->getLocationContext(); 290 FunctionSummaries->markVisitedBasicBlock(Blk->getBlockID(), 291 LC->getDecl(), 292 LC->getCFG()->getNumBlockIDs()); 293 294 // Check if we are entering the EXIT block. 295 if (Blk == &(L.getLocationContext()->getCFG()->getExit())) { 296 297 assert (L.getLocationContext()->getCFG()->getExit().size() == 0 298 && "EXIT block cannot contain Stmts."); 299 300 // Process the final state transition. 301 SubEng.processEndOfFunction(BuilderCtx); 302 303 // This path is done. Don't enqueue any more nodes. 304 return; 305 } 306 307 // Call into the SubEngine to process entering the CFGBlock. 308 ExplodedNodeSet dstNodes; 309 BlockEntrance BE(Blk, Pred->getLocationContext()); 310 NodeBuilderWithSinks nodeBuilder(Pred, dstNodes, BuilderCtx, BE); 311 SubEng.processCFGBlockEntrance(L, nodeBuilder); 312 313 // Auto-generate a node. 314 if (!nodeBuilder.hasGeneratedNodes()) { 315 nodeBuilder.generateNode(Pred->State, Pred); 316 } 317 318 // Enqueue nodes onto the worklist. 319 enqueue(dstNodes); 320} 321 322void CoreEngine::HandleBlockEntrance(const BlockEntrance &L, 323 ExplodedNode *Pred) { 324 325 // Increment the block counter. 326 const LocationContext *LC = Pred->getLocationContext(); 327 unsigned BlockId = L.getBlock()->getBlockID(); 328 BlockCounter Counter = WList->getBlockCounter(); 329 Counter = BCounterFactory.IncrementCount(Counter, LC->getCurrentStackFrame(), 330 BlockId); 331 WList->setBlockCounter(Counter); 332 333 // Process the entrance of the block. 334 if (CFGElement E = L.getFirstElement()) { 335 NodeBuilderContext Ctx(*this, L.getBlock(), Pred); 336 SubEng.processCFGElement(E, Pred, 0, &Ctx); 337 } 338 else 339 HandleBlockExit(L.getBlock(), Pred); 340} 341 342void CoreEngine::HandleBlockExit(const CFGBlock * B, ExplodedNode *Pred) { 343 344 if (const Stmt *Term = B->getTerminator()) { 345 switch (Term->getStmtClass()) { 346 default: 347 llvm_unreachable("Analysis for this terminator not implemented."); 348 349 case Stmt::BinaryOperatorClass: // '&&' and '||' 350 HandleBranch(cast<BinaryOperator>(Term)->getLHS(), Term, B, Pred); 351 return; 352 353 case Stmt::BinaryConditionalOperatorClass: 354 case Stmt::ConditionalOperatorClass: 355 HandleBranch(cast<AbstractConditionalOperator>(Term)->getCond(), 356 Term, B, Pred); 357 return; 358 359 // FIXME: Use constant-folding in CFG construction to simplify this 360 // case. 361 362 case Stmt::ChooseExprClass: 363 HandleBranch(cast<ChooseExpr>(Term)->getCond(), Term, B, Pred); 364 return; 365 366 case Stmt::CXXTryStmtClass: { 367 // Generate a node for each of the successors. 368 // Our logic for EH analysis can certainly be improved. 369 for (CFGBlock::const_succ_iterator it = B->succ_begin(), 370 et = B->succ_end(); it != et; ++it) { 371 if (const CFGBlock *succ = *it) { 372 generateNode(BlockEdge(B, succ, Pred->getLocationContext()), 373 Pred->State, Pred); 374 } 375 } 376 return; 377 } 378 379 case Stmt::DoStmtClass: 380 HandleBranch(cast<DoStmt>(Term)->getCond(), Term, B, Pred); 381 return; 382 383 case Stmt::CXXForRangeStmtClass: 384 HandleBranch(cast<CXXForRangeStmt>(Term)->getCond(), Term, B, Pred); 385 return; 386 387 case Stmt::ForStmtClass: 388 HandleBranch(cast<ForStmt>(Term)->getCond(), Term, B, Pred); 389 return; 390 391 case Stmt::ContinueStmtClass: 392 case Stmt::BreakStmtClass: 393 case Stmt::GotoStmtClass: 394 break; 395 396 case Stmt::IfStmtClass: 397 HandleBranch(cast<IfStmt>(Term)->getCond(), Term, B, Pred); 398 return; 399 400 case Stmt::IndirectGotoStmtClass: { 401 // Only 1 successor: the indirect goto dispatch block. 402 assert (B->succ_size() == 1); 403 404 IndirectGotoNodeBuilder 405 builder(Pred, B, cast<IndirectGotoStmt>(Term)->getTarget(), 406 *(B->succ_begin()), this); 407 408 SubEng.processIndirectGoto(builder); 409 return; 410 } 411 412 case Stmt::ObjCForCollectionStmtClass: { 413 // In the case of ObjCForCollectionStmt, it appears twice in a CFG: 414 // 415 // (1) inside a basic block, which represents the binding of the 416 // 'element' variable to a value. 417 // (2) in a terminator, which represents the branch. 418 // 419 // For (1), subengines will bind a value (i.e., 0 or 1) indicating 420 // whether or not collection contains any more elements. We cannot 421 // just test to see if the element is nil because a container can 422 // contain nil elements. 423 HandleBranch(Term, Term, B, Pred); 424 return; 425 } 426 427 case Stmt::SwitchStmtClass: { 428 SwitchNodeBuilder builder(Pred, B, cast<SwitchStmt>(Term)->getCond(), 429 this); 430 431 SubEng.processSwitch(builder); 432 return; 433 } 434 435 case Stmt::WhileStmtClass: 436 HandleBranch(cast<WhileStmt>(Term)->getCond(), Term, B, Pred); 437 return; 438 } 439 } 440 441 assert (B->succ_size() == 1 && 442 "Blocks with no terminator should have at most 1 successor."); 443 444 generateNode(BlockEdge(B, *(B->succ_begin()), Pred->getLocationContext()), 445 Pred->State, Pred); 446} 447 448void CoreEngine::HandleBranch(const Stmt *Cond, const Stmt *Term, 449 const CFGBlock * B, ExplodedNode *Pred) { 450 assert(B->succ_size() == 2); 451 NodeBuilderContext Ctx(*this, B, Pred); 452 ExplodedNodeSet Dst; 453 SubEng.processBranch(Cond, Term, Ctx, Pred, Dst, 454 *(B->succ_begin()), *(B->succ_begin()+1)); 455 // Enqueue the new frontier onto the worklist. 456 enqueue(Dst); 457} 458 459void CoreEngine::HandlePostStmt(const CFGBlock *B, unsigned StmtIdx, 460 ExplodedNode *Pred) { 461 assert(B); 462 assert(!B->empty()); 463 464 if (StmtIdx == B->size()) 465 HandleBlockExit(B, Pred); 466 else { 467 NodeBuilderContext Ctx(*this, B, Pred); 468 SubEng.processCFGElement((*B)[StmtIdx], Pred, StmtIdx, &Ctx); 469 } 470} 471 472/// generateNode - Utility method to generate nodes, hook up successors, 473/// and add nodes to the worklist. 474void CoreEngine::generateNode(const ProgramPoint &Loc, 475 ProgramStateRef State, 476 ExplodedNode *Pred) { 477 478 bool IsNew; 479 ExplodedNode *Node = G->getNode(Loc, State, false, &IsNew); 480 481 if (Pred) 482 Node->addPredecessor(Pred, *G); // Link 'Node' with its predecessor. 483 else { 484 assert (IsNew); 485 G->addRoot(Node); // 'Node' has no predecessor. Make it a root. 486 } 487 488 // Only add 'Node' to the worklist if it was freshly generated. 489 if (IsNew) WList->enqueue(Node); 490} 491 492void CoreEngine::enqueueStmtNode(ExplodedNode *N, 493 const CFGBlock *Block, unsigned Idx) { 494 assert(Block); 495 assert (!N->isSink()); 496 497 // Check if this node entered a callee. 498 if (isa<CallEnter>(N->getLocation())) { 499 // Still use the index of the CallExpr. It's needed to create the callee 500 // StackFrameContext. 501 WList->enqueue(N, Block, Idx); 502 return; 503 } 504 505 // Do not create extra nodes. Move to the next CFG element. 506 if (isa<PostInitializer>(N->getLocation())) { 507 WList->enqueue(N, Block, Idx+1); 508 return; 509 } 510 511 if (isa<EpsilonPoint>(N->getLocation())) { 512 WList->enqueue(N, Block, Idx); 513 return; 514 } 515 516 const CFGStmt *CS = (*Block)[Idx].getAs<CFGStmt>(); 517 const Stmt *St = CS ? CS->getStmt() : 0; 518 PostStmt Loc(St, N->getLocationContext()); 519 520 if (Loc == N->getLocation()) { 521 // Note: 'N' should be a fresh node because otherwise it shouldn't be 522 // a member of Deferred. 523 WList->enqueue(N, Block, Idx+1); 524 return; 525 } 526 527 bool IsNew; 528 ExplodedNode *Succ = G->getNode(Loc, N->getState(), false, &IsNew); 529 Succ->addPredecessor(N, *G); 530 531 if (IsNew) 532 WList->enqueue(Succ, Block, Idx+1); 533} 534 535ExplodedNode *CoreEngine::generateCallExitNode(ExplodedNode *N) { 536 // Create a CallExit node and enqueue it. 537 const StackFrameContext *LocCtx 538 = cast<StackFrameContext>(N->getLocationContext()); 539 const Stmt *CE = LocCtx->getCallSite(); 540 541 // Use the the callee location context. 542 CallExit Loc(CE, LocCtx); 543 544 bool isNew; 545 ExplodedNode *Node = G->getNode(Loc, N->getState(), false, &isNew); 546 Node->addPredecessor(N, *G); 547 return isNew ? Node : 0; 548} 549 550 551void CoreEngine::enqueue(ExplodedNodeSet &Set) { 552 for (ExplodedNodeSet::iterator I = Set.begin(), 553 E = Set.end(); I != E; ++I) { 554 WList->enqueue(*I); 555 } 556} 557 558void CoreEngine::enqueue(ExplodedNodeSet &Set, 559 const CFGBlock *Block, unsigned Idx) { 560 for (ExplodedNodeSet::iterator I = Set.begin(), 561 E = Set.end(); I != E; ++I) { 562 enqueueStmtNode(*I, Block, Idx); 563 } 564} 565 566void CoreEngine::enqueueEndOfFunction(ExplodedNodeSet &Set) { 567 for (ExplodedNodeSet::iterator I = Set.begin(), E = Set.end(); I != E; ++I) { 568 ExplodedNode *N = *I; 569 // If we are in an inlined call, generate CallExit node. 570 if (N->getLocationContext()->getParent()) { 571 N = generateCallExitNode(N); 572 if (N) 573 WList->enqueue(N); 574 } else { 575 G->addEndOfPath(N); 576 NumPathsExplored++; 577 } 578 } 579} 580 581 582void NodeBuilder::anchor() { } 583 584ExplodedNode* NodeBuilder::generateNodeImpl(const ProgramPoint &Loc, 585 ProgramStateRef State, 586 ExplodedNode *FromN, 587 bool MarkAsSink) { 588 HasGeneratedNodes = true; 589 bool IsNew; 590 ExplodedNode *N = C.Eng.G->getNode(Loc, State, MarkAsSink, &IsNew); 591 N->addPredecessor(FromN, *C.Eng.G); 592 Frontier.erase(FromN); 593 594 if (!IsNew) 595 return 0; 596 597 if (!MarkAsSink) 598 Frontier.Add(N); 599 600 return N; 601} 602 603void NodeBuilderWithSinks::anchor() { } 604 605StmtNodeBuilder::~StmtNodeBuilder() { 606 if (EnclosingBldr) 607 for (ExplodedNodeSet::iterator I = Frontier.begin(), 608 E = Frontier.end(); I != E; ++I ) 609 EnclosingBldr->addNodes(*I); 610} 611 612void BranchNodeBuilder::anchor() { } 613 614ExplodedNode *BranchNodeBuilder::generateNode(ProgramStateRef State, 615 bool branch, 616 ExplodedNode *NodePred) { 617 // If the branch has been marked infeasible we should not generate a node. 618 if (!isFeasible(branch)) 619 return NULL; 620 621 ProgramPoint Loc = BlockEdge(C.Block, branch ? DstT:DstF, 622 NodePred->getLocationContext()); 623 ExplodedNode *Succ = generateNodeImpl(Loc, State, NodePred); 624 return Succ; 625} 626 627ExplodedNode* 628IndirectGotoNodeBuilder::generateNode(const iterator &I, 629 ProgramStateRef St, 630 bool IsSink) { 631 bool IsNew; 632 ExplodedNode *Succ = Eng.G->getNode(BlockEdge(Src, I.getBlock(), 633 Pred->getLocationContext()), St, 634 IsSink, &IsNew); 635 Succ->addPredecessor(Pred, *Eng.G); 636 637 if (!IsNew) 638 return 0; 639 640 if (!IsSink) 641 Eng.WList->enqueue(Succ); 642 643 return Succ; 644} 645 646 647ExplodedNode* 648SwitchNodeBuilder::generateCaseStmtNode(const iterator &I, 649 ProgramStateRef St) { 650 651 bool IsNew; 652 ExplodedNode *Succ = Eng.G->getNode(BlockEdge(Src, I.getBlock(), 653 Pred->getLocationContext()), St, 654 false, &IsNew); 655 Succ->addPredecessor(Pred, *Eng.G); 656 if (!IsNew) 657 return 0; 658 659 Eng.WList->enqueue(Succ); 660 return Succ; 661} 662 663 664ExplodedNode* 665SwitchNodeBuilder::generateDefaultCaseNode(ProgramStateRef St, 666 bool IsSink) { 667 // Get the block for the default case. 668 assert(Src->succ_rbegin() != Src->succ_rend()); 669 CFGBlock *DefaultBlock = *Src->succ_rbegin(); 670 671 // Sanity check for default blocks that are unreachable and not caught 672 // by earlier stages. 673 if (!DefaultBlock) 674 return NULL; 675 676 bool IsNew; 677 ExplodedNode *Succ = Eng.G->getNode(BlockEdge(Src, DefaultBlock, 678 Pred->getLocationContext()), St, 679 IsSink, &IsNew); 680 Succ->addPredecessor(Pred, *Eng.G); 681 682 if (!IsNew) 683 return 0; 684 685 if (!IsSink) 686 Eng.WList->enqueue(Succ); 687 688 return Succ; 689} 690