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