1 //=-- ExplodedGraph.h - 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 //  See "Precise interprocedural dataflow analysis via graph reachability"
13 //  by Reps, Horwitz, and Sagiv
14 //  (http://portal.acm.org/citation.cfm?id=199462) for the definition of an
15 //  exploded graph.
16 //
17 //===----------------------------------------------------------------------===//
18 
19 #ifndef LLVM_CLANG_GR_EXPLODEDGRAPH
20 #define LLVM_CLANG_GR_EXPLODEDGRAPH
21 
22 #include "clang/Analysis/ProgramPoint.h"
23 #include "clang/Analysis/AnalysisContext.h"
24 #include "clang/AST/Decl.h"
25 #include "llvm/ADT/SmallVector.h"
26 #include "llvm/ADT/FoldingSet.h"
27 #include "llvm/ADT/SmallPtrSet.h"
28 #include "llvm/Support/Allocator.h"
29 #include "llvm/ADT/OwningPtr.h"
30 #include "llvm/ADT/GraphTraits.h"
31 #include "llvm/ADT/DepthFirstIterator.h"
32 #include "llvm/Support/Casting.h"
33 #include "clang/Analysis/Support/BumpVector.h"
34 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
35 #include <vector>
36 
37 namespace clang {
38 
39 class CFG;
40 
41 namespace ento {
42 
43 class ExplodedGraph;
44 
45 //===----------------------------------------------------------------------===//
46 // ExplodedGraph "implementation" classes.  These classes are not typed to
47 // contain a specific kind of state.  Typed-specialized versions are defined
48 // on top of these classes.
49 //===----------------------------------------------------------------------===//
50 
51 // ExplodedNode is not constified all over the engine because we need to add
52 // successors to it at any time after creating it.
53 
54 class ExplodedNode : public llvm::FoldingSetNode {
55   friend class ExplodedGraph;
56   friend class CoreEngine;
57   friend class NodeBuilder;
58   friend class BranchNodeBuilder;
59   friend class IndirectGotoNodeBuilder;
60   friend class SwitchNodeBuilder;
61   friend class EndOfFunctionNodeBuilder;
62 
63   class NodeGroup {
64     enum { Size1 = 0x0, SizeOther = 0x1, AuxFlag = 0x2, Mask = 0x3 };
65     uintptr_t P;
66 
67     unsigned getKind() const {
68       return P & 0x1;
69     }
70 
71     void *getPtr() const {
72       assert (!getFlag());
73       return reinterpret_cast<void*>(P & ~Mask);
74     }
75 
76     ExplodedNode *getNode() const {
77       return reinterpret_cast<ExplodedNode*>(getPtr());
78     }
79 
80   public:
81     NodeGroup() : P(0) {}
82 
83     ExplodedNode **begin() const;
84 
85     ExplodedNode **end() const;
86 
87     unsigned size() const;
88 
89     bool empty() const { return (P & ~Mask) == 0; }
90 
91     void addNode(ExplodedNode *N, ExplodedGraph &G);
92 
93     void replaceNode(ExplodedNode *node);
94 
95     void setFlag() {
96       assert(P == 0);
97       P = AuxFlag;
98     }
99 
100     bool getFlag() const {
101       return P & AuxFlag ? true : false;
102     }
103   };
104 
105   /// Location - The program location (within a function body) associated
106   ///  with this node.
107   const ProgramPoint Location;
108 
109   /// State - The state associated with this node.
110   ProgramStateRef State;
111 
112   /// Preds - The predecessors of this node.
113   NodeGroup Preds;
114 
115   /// Succs - The successors of this node.
116   NodeGroup Succs;
117 
118 public:
119 
120   explicit ExplodedNode(const ProgramPoint &loc, ProgramStateRef state,
121                         bool IsSink)
122     : Location(loc), State(state) {
123     if (IsSink)
124       Succs.setFlag();
125   }
126 
127   ~ExplodedNode() {}
128 
129   /// getLocation - Returns the edge associated with the given node.
130   ProgramPoint getLocation() const { return Location; }
131 
132   const LocationContext *getLocationContext() const {
133     return getLocation().getLocationContext();
134   }
135 
136   const Decl &getCodeDecl() const { return *getLocationContext()->getDecl(); }
137 
138   CFG &getCFG() const { return *getLocationContext()->getCFG(); }
139 
140   ParentMap &getParentMap() const {return getLocationContext()->getParentMap();}
141 
142   template <typename T>
143   T &getAnalysis() const {
144     return *getLocationContext()->getAnalysis<T>();
145   }
146 
147   ProgramStateRef getState() const { return State; }
148 
149   template <typename T>
150   const T* getLocationAs() const { return llvm::dyn_cast<T>(&Location); }
151 
152   static void Profile(llvm::FoldingSetNodeID &ID,
153                       const ProgramPoint &Loc,
154                       ProgramStateRef state,
155                       bool IsSink) {
156     ID.Add(Loc);
157     ID.AddPointer(state.getPtr());
158     ID.AddBoolean(IsSink);
159   }
160 
161   void Profile(llvm::FoldingSetNodeID& ID) const {
162     Profile(ID, getLocation(), getState(), isSink());
163   }
164 
165   /// addPredeccessor - Adds a predecessor to the current node, and
166   ///  in tandem add this node as a successor of the other node.
167   void addPredecessor(ExplodedNode *V, ExplodedGraph &G);
168 
169   unsigned succ_size() const { return Succs.size(); }
170   unsigned pred_size() const { return Preds.size(); }
171   bool succ_empty() const { return Succs.empty(); }
172   bool pred_empty() const { return Preds.empty(); }
173 
174   bool isSink() const { return Succs.getFlag(); }
175 
176   ExplodedNode *getFirstPred() {
177     return pred_empty() ? NULL : *(pred_begin());
178   }
179 
180   const ExplodedNode *getFirstPred() const {
181     return const_cast<ExplodedNode*>(this)->getFirstPred();
182   }
183 
184   // Iterators over successor and predecessor vertices.
185   typedef ExplodedNode**       succ_iterator;
186   typedef const ExplodedNode* const * const_succ_iterator;
187   typedef ExplodedNode**       pred_iterator;
188   typedef const ExplodedNode* const * const_pred_iterator;
189 
190   pred_iterator pred_begin() { return Preds.begin(); }
191   pred_iterator pred_end() { return Preds.end(); }
192 
193   const_pred_iterator pred_begin() const {
194     return const_cast<ExplodedNode*>(this)->pred_begin();
195   }
196   const_pred_iterator pred_end() const {
197     return const_cast<ExplodedNode*>(this)->pred_end();
198   }
199 
200   succ_iterator succ_begin() { return Succs.begin(); }
201   succ_iterator succ_end() { return Succs.end(); }
202 
203   const_succ_iterator succ_begin() const {
204     return const_cast<ExplodedNode*>(this)->succ_begin();
205   }
206   const_succ_iterator succ_end() const {
207     return const_cast<ExplodedNode*>(this)->succ_end();
208   }
209 
210   // For debugging.
211 
212 public:
213 
214   class Auditor {
215   public:
216     virtual ~Auditor();
217     virtual void AddEdge(ExplodedNode *Src, ExplodedNode *Dst) = 0;
218   };
219 
220   static void SetAuditor(Auditor* A);
221 
222 private:
223   void replaceSuccessor(ExplodedNode *node) { Succs.replaceNode(node); }
224   void replacePredecessor(ExplodedNode *node) { Preds.replaceNode(node); }
225 };
226 
227 // FIXME: Is this class necessary?
228 class InterExplodedGraphMap {
229   virtual void anchor();
230   llvm::DenseMap<const ExplodedNode*, ExplodedNode*> M;
231   friend class ExplodedGraph;
232 
233 public:
234   ExplodedNode *getMappedNode(const ExplodedNode *N) const;
235 
236   InterExplodedGraphMap() {}
237   virtual ~InterExplodedGraphMap() {}
238 };
239 
240 class ExplodedGraph {
241 protected:
242   friend class CoreEngine;
243 
244   // Type definitions.
245   typedef std::vector<ExplodedNode *> NodeVector;
246 
247   /// The roots of the simulation graph. Usually there will be only
248   /// one, but clients are free to establish multiple subgraphs within a single
249   /// SimulGraph. Moreover, these subgraphs can often merge when paths from
250   /// different roots reach the same state at the same program location.
251   NodeVector Roots;
252 
253   /// The nodes in the simulation graph which have been
254   /// specially marked as the endpoint of an abstract simulation path.
255   NodeVector EndNodes;
256 
257   /// Nodes - The nodes in the graph.
258   llvm::FoldingSet<ExplodedNode> Nodes;
259 
260   /// BVC - Allocator and context for allocating nodes and their predecessor
261   /// and successor groups.
262   BumpVectorContext BVC;
263 
264   /// NumNodes - The number of nodes in the graph.
265   unsigned NumNodes;
266 
267   /// A list of recently allocated nodes that can potentially be recycled.
268   NodeVector ChangedNodes;
269 
270   /// A list of nodes that can be reused.
271   NodeVector FreeNodes;
272 
273   /// A flag that indicates whether nodes should be recycled.
274   bool reclaimNodes;
275 
276   /// Counter to determine when to reclaim nodes.
277   unsigned reclaimCounter;
278 
279 public:
280 
281   /// \brief Retrieve the node associated with a (Location,State) pair,
282   ///  where the 'Location' is a ProgramPoint in the CFG.  If no node for
283   ///  this pair exists, it is created. IsNew is set to true if
284   ///  the node was freshly created.
285   ExplodedNode *getNode(const ProgramPoint &L, ProgramStateRef State,
286                         bool IsSink = false,
287                         bool* IsNew = 0);
288 
289   ExplodedGraph* MakeEmptyGraph() const {
290     return new ExplodedGraph();
291   }
292 
293   /// addRoot - Add an untyped node to the set of roots.
294   ExplodedNode *addRoot(ExplodedNode *V) {
295     Roots.push_back(V);
296     return V;
297   }
298 
299   /// addEndOfPath - Add an untyped node to the set of EOP nodes.
300   ExplodedNode *addEndOfPath(ExplodedNode *V) {
301     EndNodes.push_back(V);
302     return V;
303   }
304 
305   ExplodedGraph();
306 
307   ~ExplodedGraph();
308 
309   unsigned num_roots() const { return Roots.size(); }
310   unsigned num_eops() const { return EndNodes.size(); }
311 
312   bool empty() const { return NumNodes == 0; }
313   unsigned size() const { return NumNodes; }
314 
315   // Iterators.
316   typedef ExplodedNode                        NodeTy;
317   typedef llvm::FoldingSet<ExplodedNode>      AllNodesTy;
318   typedef NodeVector::iterator                roots_iterator;
319   typedef NodeVector::const_iterator          const_roots_iterator;
320   typedef NodeVector::iterator                eop_iterator;
321   typedef NodeVector::const_iterator          const_eop_iterator;
322   typedef AllNodesTy::iterator                node_iterator;
323   typedef AllNodesTy::const_iterator          const_node_iterator;
324 
325   node_iterator nodes_begin() { return Nodes.begin(); }
326 
327   node_iterator nodes_end() { return Nodes.end(); }
328 
329   const_node_iterator nodes_begin() const { return Nodes.begin(); }
330 
331   const_node_iterator nodes_end() const { return Nodes.end(); }
332 
333   roots_iterator roots_begin() { return Roots.begin(); }
334 
335   roots_iterator roots_end() { return Roots.end(); }
336 
337   const_roots_iterator roots_begin() const { return Roots.begin(); }
338 
339   const_roots_iterator roots_end() const { return Roots.end(); }
340 
341   eop_iterator eop_begin() { return EndNodes.begin(); }
342 
343   eop_iterator eop_end() { return EndNodes.end(); }
344 
345   const_eop_iterator eop_begin() const { return EndNodes.begin(); }
346 
347   const_eop_iterator eop_end() const { return EndNodes.end(); }
348 
349   llvm::BumpPtrAllocator & getAllocator() { return BVC.getAllocator(); }
350   BumpVectorContext &getNodeAllocator() { return BVC; }
351 
352   typedef llvm::DenseMap<const ExplodedNode*, ExplodedNode*> NodeMap;
353 
354   std::pair<ExplodedGraph*, InterExplodedGraphMap*>
355   Trim(const NodeTy* const* NBeg, const NodeTy* const* NEnd,
356        llvm::DenseMap<const void*, const void*> *InverseMap = 0) const;
357 
358   ExplodedGraph* TrimInternal(const ExplodedNode* const * NBeg,
359                               const ExplodedNode* const * NEnd,
360                               InterExplodedGraphMap *M,
361                     llvm::DenseMap<const void*, const void*> *InverseMap) const;
362 
363   /// Enable tracking of recently allocated nodes for potential reclamation
364   /// when calling reclaimRecentlyAllocatedNodes().
365   void enableNodeReclamation() { reclaimNodes = true; }
366 
367   /// Reclaim "uninteresting" nodes created since the last time this method
368   /// was called.
369   void reclaimRecentlyAllocatedNodes();
370 
371 private:
372   bool shouldCollect(const ExplodedNode *node);
373   void collectNode(ExplodedNode *node);
374 };
375 
376 class ExplodedNodeSet {
377   typedef llvm::SmallPtrSet<ExplodedNode*,5> ImplTy;
378   ImplTy Impl;
379 
380 public:
381   ExplodedNodeSet(ExplodedNode *N) {
382     assert (N && !static_cast<ExplodedNode*>(N)->isSink());
383     Impl.insert(N);
384   }
385 
386   ExplodedNodeSet() {}
387 
388   inline void Add(ExplodedNode *N) {
389     if (N && !static_cast<ExplodedNode*>(N)->isSink()) Impl.insert(N);
390   }
391 
392   typedef ImplTy::iterator       iterator;
393   typedef ImplTy::const_iterator const_iterator;
394 
395   unsigned size() const { return Impl.size();  }
396   bool empty()    const { return Impl.empty(); }
397   bool erase(ExplodedNode *N) { return Impl.erase(N); }
398 
399   void clear() { Impl.clear(); }
400   void insert(const ExplodedNodeSet &S) {
401     assert(&S != this);
402     if (empty())
403       Impl = S.Impl;
404     else
405       Impl.insert(S.begin(), S.end());
406   }
407 
408   inline iterator begin() { return Impl.begin(); }
409   inline iterator end()   { return Impl.end();   }
410 
411   inline const_iterator begin() const { return Impl.begin(); }
412   inline const_iterator end()   const { return Impl.end();   }
413 };
414 
415 } // end GR namespace
416 
417 } // end clang namespace
418 
419 // GraphTraits
420 
421 namespace llvm {
422   template<> struct GraphTraits<clang::ento::ExplodedNode*> {
423     typedef clang::ento::ExplodedNode NodeType;
424     typedef NodeType::succ_iterator  ChildIteratorType;
425     typedef llvm::df_iterator<NodeType*>      nodes_iterator;
426 
427     static inline NodeType* getEntryNode(NodeType* N) {
428       return N;
429     }
430 
431     static inline ChildIteratorType child_begin(NodeType* N) {
432       return N->succ_begin();
433     }
434 
435     static inline ChildIteratorType child_end(NodeType* N) {
436       return N->succ_end();
437     }
438 
439     static inline nodes_iterator nodes_begin(NodeType* N) {
440       return df_begin(N);
441     }
442 
443     static inline nodes_iterator nodes_end(NodeType* N) {
444       return df_end(N);
445     }
446   };
447 
448   template<> struct GraphTraits<const clang::ento::ExplodedNode*> {
449     typedef const clang::ento::ExplodedNode NodeType;
450     typedef NodeType::const_succ_iterator   ChildIteratorType;
451     typedef llvm::df_iterator<NodeType*>       nodes_iterator;
452 
453     static inline NodeType* getEntryNode(NodeType* N) {
454       return N;
455     }
456 
457     static inline ChildIteratorType child_begin(NodeType* N) {
458       return N->succ_begin();
459     }
460 
461     static inline ChildIteratorType child_end(NodeType* N) {
462       return N->succ_end();
463     }
464 
465     static inline nodes_iterator nodes_begin(NodeType* N) {
466       return df_begin(N);
467     }
468 
469     static inline nodes_iterator nodes_end(NodeType* N) {
470       return df_end(N);
471     }
472   };
473 
474 } // end llvm namespace
475 
476 #endif
477