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 
36 namespace clang {
37 
38 class CFG;
39 
40 namespace ento {
41 
42 class ExplodedGraph;
43 
44 //===----------------------------------------------------------------------===//
45 // ExplodedGraph "implementation" classes.  These classes are not typed to
46 // contain a specific kind of state.  Typed-specialized versions are defined
47 // on top of these classes.
48 //===----------------------------------------------------------------------===//
49 
50 // ExplodedNode is not constified all over the engine because we need to add
51 // successors to it at any time after creating it.
52 
53 class ExplodedNode : public llvm::FoldingSetNode {
54   friend class ExplodedGraph;
55   friend class CoreEngine;
56   friend class NodeBuilder;
57   friend class BranchNodeBuilder;
58   friend class IndirectGotoNodeBuilder;
59   friend class SwitchNodeBuilder;
60   friend class EndOfFunctionNodeBuilder;
61 
62   class NodeGroup {
63     enum { Size1 = 0x0, SizeOther = 0x1, AuxFlag = 0x2, Mask = 0x3 };
64     uintptr_t P;
65 
66     unsigned getKind() const {
67       return P & 0x1;
68     }
69 
70     void *getPtr() const {
71       assert (!getFlag());
72       return reinterpret_cast<void*>(P & ~Mask);
73     }
74 
75     ExplodedNode *getNode() const {
76       return reinterpret_cast<ExplodedNode*>(getPtr());
77     }
78 
79   public:
80     NodeGroup() : P(0) {}
81 
82     ExplodedNode **begin() const;
83 
84     ExplodedNode **end() const;
85 
86     unsigned size() const;
87 
88     bool empty() const { return (P & ~Mask) == 0; }
89 
90     void addNode(ExplodedNode *N, ExplodedGraph &G);
91 
92     void replaceNode(ExplodedNode *node);
93 
94     void setFlag() {
95       assert(P == 0);
96       P = AuxFlag;
97     }
98 
99     bool getFlag() const {
100       return P & AuxFlag ? true : false;
101     }
102   };
103 
104   /// Location - The program location (within a function body) associated
105   ///  with this node.
106   const ProgramPoint Location;
107 
108   /// State - The state associated with this node.
109   const ProgramState *State;
110 
111   /// Preds - The predecessors of this node.
112   NodeGroup Preds;
113 
114   /// Succs - The successors of this node.
115   NodeGroup Succs;
116 
117 public:
118 
119   explicit ExplodedNode(const ProgramPoint &loc, const ProgramState *state,
120                         bool IsSink)
121     : Location(loc), State(state) {
122     const_cast<ProgramState*>(State)->incrementReferenceCount();
123     if (IsSink)
124       Succs.setFlag();
125   }
126 
127   ~ExplodedNode() {
128     const_cast<ProgramState*>(State)->decrementReferenceCount();
129   }
130 
131   /// getLocation - Returns the edge associated with the given node.
132   ProgramPoint getLocation() const { return Location; }
133 
134   const LocationContext *getLocationContext() const {
135     return getLocation().getLocationContext();
136   }
137 
138   const Decl &getCodeDecl() const { return *getLocationContext()->getDecl(); }
139 
140   CFG &getCFG() const { return *getLocationContext()->getCFG(); }
141 
142   ParentMap &getParentMap() const {return getLocationContext()->getParentMap();}
143 
144   template <typename T>
145   T &getAnalysis() const {
146     return *getLocationContext()->getAnalysis<T>();
147   }
148 
149   const ProgramState *getState() const { return State; }
150 
151   template <typename T>
152   const T* getLocationAs() const { return llvm::dyn_cast<T>(&Location); }
153 
154   static void Profile(llvm::FoldingSetNodeID &ID,
155                       const ProgramPoint &Loc,
156                       const ProgramState *state,
157                       bool IsSink) {
158     ID.Add(Loc);
159     ID.AddPointer(state);
160     ID.AddBoolean(IsSink);
161   }
162 
163   void Profile(llvm::FoldingSetNodeID& ID) const {
164     Profile(ID, getLocation(), getState(), isSink());
165   }
166 
167   /// addPredeccessor - Adds a predecessor to the current node, and
168   ///  in tandem add this node as a successor of the other node.
169   void addPredecessor(ExplodedNode *V, ExplodedGraph &G);
170 
171   unsigned succ_size() const { return Succs.size(); }
172   unsigned pred_size() const { return Preds.size(); }
173   bool succ_empty() const { return Succs.empty(); }
174   bool pred_empty() const { return Preds.empty(); }
175 
176   bool isSink() const { return Succs.getFlag(); }
177 
178   ExplodedNode *getFirstPred() {
179     return pred_empty() ? NULL : *(pred_begin());
180   }
181 
182   const ExplodedNode *getFirstPred() const {
183     return const_cast<ExplodedNode*>(this)->getFirstPred();
184   }
185 
186   // Iterators over successor and predecessor vertices.
187   typedef ExplodedNode**       succ_iterator;
188   typedef const ExplodedNode* const * const_succ_iterator;
189   typedef ExplodedNode**       pred_iterator;
190   typedef const ExplodedNode* const * const_pred_iterator;
191 
192   pred_iterator pred_begin() { return Preds.begin(); }
193   pred_iterator pred_end() { return Preds.end(); }
194 
195   const_pred_iterator pred_begin() const {
196     return const_cast<ExplodedNode*>(this)->pred_begin();
197   }
198   const_pred_iterator pred_end() const {
199     return const_cast<ExplodedNode*>(this)->pred_end();
200   }
201 
202   succ_iterator succ_begin() { return Succs.begin(); }
203   succ_iterator succ_end() { return Succs.end(); }
204 
205   const_succ_iterator succ_begin() const {
206     return const_cast<ExplodedNode*>(this)->succ_begin();
207   }
208   const_succ_iterator succ_end() const {
209     return const_cast<ExplodedNode*>(this)->succ_end();
210   }
211 
212   // For debugging.
213 
214 public:
215 
216   class Auditor {
217   public:
218     virtual ~Auditor();
219     virtual void AddEdge(ExplodedNode *Src, ExplodedNode *Dst) = 0;
220   };
221 
222   static void SetAuditor(Auditor* A);
223 
224 private:
225   void replaceSuccessor(ExplodedNode *node) { Succs.replaceNode(node); }
226   void replacePredecessor(ExplodedNode *node) { Preds.replaceNode(node); }
227 };
228 
229 // FIXME: Is this class necessary?
230 class InterExplodedGraphMap {
231   llvm::DenseMap<const ExplodedNode*, ExplodedNode*> M;
232   friend class ExplodedGraph;
233 
234 public:
235   ExplodedNode *getMappedNode(const ExplodedNode *N) const;
236 
237   InterExplodedGraphMap() {}
238   virtual ~InterExplodedGraphMap() {}
239 };
240 
241 class ExplodedGraph {
242 protected:
243   friend class CoreEngine;
244 
245   // Type definitions.
246   typedef SmallVector<ExplodedNode*,2>    RootsTy;
247   typedef SmallVector<ExplodedNode*,10>   EndNodesTy;
248 
249   /// Roots - The roots of the simulation graph. Usually there will be only
250   /// one, but clients are free to establish multiple subgraphs within a single
251   /// SimulGraph. Moreover, these subgraphs can often merge when paths from
252   /// different roots reach the same state at the same program location.
253   RootsTy Roots;
254 
255   /// EndNodes - The nodes in the simulation graph which have been
256   ///  specially marked as the endpoint of an abstract simulation path.
257   EndNodesTy EndNodes;
258 
259   /// Nodes - The nodes in the graph.
260   llvm::FoldingSet<ExplodedNode> Nodes;
261 
262   /// BVC - Allocator and context for allocating nodes and their predecessor
263   /// and successor groups.
264   BumpVectorContext BVC;
265 
266   /// NumNodes - The number of nodes in the graph.
267   unsigned NumNodes;
268 
269   /// A list of recently allocated nodes that can potentially be recycled.
270   void *recentlyAllocatedNodes;
271 
272   /// A list of nodes that can be reused.
273   void *freeNodes;
274 
275   /// A flag that indicates whether nodes should be recycled.
276   bool reclaimNodes;
277 
278 public:
279 
280   /// \brief Retrieve the node associated with a (Location,State) pair,
281   ///  where the 'Location' is a ProgramPoint in the CFG.  If no node for
282   ///  this pair exists, it is created. IsNew is set to true if
283   ///  the node was freshly created.
284   ExplodedNode *getNode(const ProgramPoint &L, const ProgramState *State,
285                         bool IsSink = false,
286                         bool* IsNew = 0);
287 
288   ExplodedGraph* MakeEmptyGraph() const {
289     return new ExplodedGraph();
290   }
291 
292   /// addRoot - Add an untyped node to the set of roots.
293   ExplodedNode *addRoot(ExplodedNode *V) {
294     Roots.push_back(V);
295     return V;
296   }
297 
298   /// addEndOfPath - Add an untyped node to the set of EOP nodes.
299   ExplodedNode *addEndOfPath(ExplodedNode *V) {
300     EndNodes.push_back(V);
301     return V;
302   }
303 
304   ExplodedGraph()
305     : NumNodes(0), recentlyAllocatedNodes(0),
306       freeNodes(0), reclaimNodes(false) {}
307 
308   ~ExplodedGraph();
309 
310   unsigned num_roots() const { return Roots.size(); }
311   unsigned num_eops() const { return EndNodes.size(); }
312 
313   bool empty() const { return NumNodes == 0; }
314   unsigned size() const { return NumNodes; }
315 
316   // Iterators.
317   typedef ExplodedNode                        NodeTy;
318   typedef llvm::FoldingSet<ExplodedNode>      AllNodesTy;
319   typedef NodeTy**                            roots_iterator;
320   typedef NodeTy* const *                     const_roots_iterator;
321   typedef NodeTy**                            eop_iterator;
322   typedef NodeTy* const *                     const_eop_iterator;
323   typedef AllNodesTy::iterator                node_iterator;
324   typedef AllNodesTy::const_iterator          const_node_iterator;
325 
326   node_iterator nodes_begin() { return Nodes.begin(); }
327 
328   node_iterator nodes_end() { return Nodes.end(); }
329 
330   const_node_iterator nodes_begin() const { return Nodes.begin(); }
331 
332   const_node_iterator nodes_end() const { return Nodes.end(); }
333 
334   roots_iterator roots_begin() { return Roots.begin(); }
335 
336   roots_iterator roots_end() { return Roots.end(); }
337 
338   const_roots_iterator roots_begin() const { return Roots.begin(); }
339 
340   const_roots_iterator roots_end() const { return Roots.end(); }
341 
342   eop_iterator eop_begin() { return EndNodes.begin(); }
343 
344   eop_iterator eop_end() { return EndNodes.end(); }
345 
346   const_eop_iterator eop_begin() const { return EndNodes.begin(); }
347 
348   const_eop_iterator eop_end() const { return EndNodes.end(); }
349 
350   llvm::BumpPtrAllocator & getAllocator() { return BVC.getAllocator(); }
351   BumpVectorContext &getNodeAllocator() { return BVC; }
352 
353   typedef llvm::DenseMap<const ExplodedNode*, ExplodedNode*> NodeMap;
354 
355   std::pair<ExplodedGraph*, InterExplodedGraphMap*>
356   Trim(const NodeTy* const* NBeg, const NodeTy* const* NEnd,
357        llvm::DenseMap<const void*, const void*> *InverseMap = 0) const;
358 
359   ExplodedGraph* TrimInternal(const ExplodedNode* const * NBeg,
360                               const ExplodedNode* const * NEnd,
361                               InterExplodedGraphMap *M,
362                     llvm::DenseMap<const void*, const void*> *InverseMap) const;
363 
364   /// Enable tracking of recently allocated nodes for potential reclamation
365   /// when calling reclaimRecentlyAllocatedNodes().
366   void enableNodeReclamation() { reclaimNodes = true; }
367 
368   /// Reclaim "uninteresting" nodes created since the last time this method
369   /// was called.
370   void reclaimRecentlyAllocatedNodes();
371 };
372 
373 class ExplodedNodeSet {
374   typedef llvm::SmallPtrSet<ExplodedNode*,5> ImplTy;
375   ImplTy Impl;
376 
377 public:
378   ExplodedNodeSet(ExplodedNode *N) {
379     assert (N && !static_cast<ExplodedNode*>(N)->isSink());
380     Impl.insert(N);
381   }
382 
383   ExplodedNodeSet() {}
384 
385   inline void Add(ExplodedNode *N) {
386     if (N && !static_cast<ExplodedNode*>(N)->isSink()) Impl.insert(N);
387   }
388 
389   typedef ImplTy::iterator       iterator;
390   typedef ImplTy::const_iterator const_iterator;
391 
392   unsigned size() const { return Impl.size();  }
393   bool empty()    const { return Impl.empty(); }
394   bool erase(ExplodedNode *N) { return Impl.erase(N); }
395 
396   void clear() { Impl.clear(); }
397   void insert(const ExplodedNodeSet &S) {
398     assert(&S != this);
399     if (empty())
400       Impl = S.Impl;
401     else
402       Impl.insert(S.begin(), S.end());
403   }
404 
405   inline iterator begin() { return Impl.begin(); }
406   inline iterator end()   { return Impl.end();   }
407 
408   inline const_iterator begin() const { return Impl.begin(); }
409   inline const_iterator end()   const { return Impl.end();   }
410 };
411 
412 } // end GR namespace
413 
414 } // end clang namespace
415 
416 // GraphTraits
417 
418 namespace llvm {
419   template<> struct GraphTraits<clang::ento::ExplodedNode*> {
420     typedef clang::ento::ExplodedNode NodeType;
421     typedef NodeType::succ_iterator  ChildIteratorType;
422     typedef llvm::df_iterator<NodeType*>      nodes_iterator;
423 
424     static inline NodeType* getEntryNode(NodeType* N) {
425       return N;
426     }
427 
428     static inline ChildIteratorType child_begin(NodeType* N) {
429       return N->succ_begin();
430     }
431 
432     static inline ChildIteratorType child_end(NodeType* N) {
433       return N->succ_end();
434     }
435 
436     static inline nodes_iterator nodes_begin(NodeType* N) {
437       return df_begin(N);
438     }
439 
440     static inline nodes_iterator nodes_end(NodeType* N) {
441       return df_end(N);
442     }
443   };
444 
445   template<> struct GraphTraits<const clang::ento::ExplodedNode*> {
446     typedef const clang::ento::ExplodedNode NodeType;
447     typedef NodeType::const_succ_iterator   ChildIteratorType;
448     typedef llvm::df_iterator<NodeType*>       nodes_iterator;
449 
450     static inline NodeType* getEntryNode(NodeType* N) {
451       return N;
452     }
453 
454     static inline ChildIteratorType child_begin(NodeType* N) {
455       return N->succ_begin();
456     }
457 
458     static inline ChildIteratorType child_end(NodeType* N) {
459       return N->succ_end();
460     }
461 
462     static inline nodes_iterator nodes_begin(NodeType* N) {
463       return df_begin(N);
464     }
465 
466     static inline nodes_iterator nodes_end(NodeType* N) {
467       return df_end(N);
468     }
469   };
470 
471 } // end llvm namespace
472 
473 #endif
474