ExplodedGraph.h revision 1833d284346b9fa11aae4e6aa07381347c04745c
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
37namespace clang {
38
39class CFG;
40
41namespace ento {
42
43class 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
54class 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  /// Efficiently stores a list of ExplodedNodes, or an optional flag.
64  ///
65  /// NodeGroup provides opaque storage for a list of ExplodedNodes, optimizing
66  /// for the case when there is only one node in the group. This is a fairly
67  /// common case in an ExplodedGraph, where most nodes have only one
68  /// predecessor and many have only one successor. It can also be used to
69  /// store a flag rather than a node list, which ExplodedNode uses to mark
70  /// whether a node is a sink. If the flag is set, the group is implicitly
71  /// empty and no nodes may be added.
72  class NodeGroup {
73    // Conceptually a discriminated union. If the low bit is set, the node is
74    // a sink. If the low bit is not set, the pointer refers to the storage
75    // for the nodes in the group.
76    // This is not a PointerIntPair in order to keep the storage type opaque.
77    uintptr_t P;
78
79  public:
80    NodeGroup(bool Flag = false) : P(Flag) {
81      assert(getFlag() == Flag);
82    }
83
84    ExplodedNode * const *begin() const;
85
86    ExplodedNode * const *end() const;
87
88    unsigned size() const;
89
90    bool empty() const { return P == 0 || getFlag() != 0; }
91
92    /// Adds a node to the list.
93    ///
94    /// The group must not have been created with its flag set.
95    void addNode(ExplodedNode *N, ExplodedGraph &G);
96
97    /// Replaces the single node in this group with a new node.
98    ///
99    /// Note that this should only be used when you know the group was not
100    /// created with its flag set, and that the group is empty or contains
101    /// only a single node.
102    void replaceNode(ExplodedNode *node);
103
104    /// Returns whether this group was created with its flag set.
105    bool getFlag() const {
106      return (P & 1);
107    }
108  };
109
110  /// Location - The program location (within a function body) associated
111  ///  with this node.
112  const ProgramPoint Location;
113
114  /// State - The state associated with this node.
115  ProgramStateRef State;
116
117  /// Preds - The predecessors of this node.
118  NodeGroup Preds;
119
120  /// Succs - The successors of this node.
121  NodeGroup Succs;
122
123public:
124
125  explicit ExplodedNode(const ProgramPoint &loc, ProgramStateRef state,
126                        bool IsSink)
127    : Location(loc), State(state), Succs(IsSink) {
128    assert(isSink() == IsSink);
129  }
130
131  ~ExplodedNode() {}
132
133  /// getLocation - Returns the edge associated with the given node.
134  ProgramPoint getLocation() const { return Location; }
135
136  const LocationContext *getLocationContext() const {
137    return getLocation().getLocationContext();
138  }
139
140  const StackFrameContext *getStackFrame() const {
141    return getLocationContext()->getCurrentStackFrame();
142  }
143
144  const Decl &getCodeDecl() const { return *getLocationContext()->getDecl(); }
145
146  CFG &getCFG() const { return *getLocationContext()->getCFG(); }
147
148  ParentMap &getParentMap() const {return getLocationContext()->getParentMap();}
149
150  template <typename T>
151  T &getAnalysis() const {
152    return *getLocationContext()->getAnalysis<T>();
153  }
154
155  ProgramStateRef getState() const { return State; }
156
157  template <typename T>
158  const T* getLocationAs() const { return llvm::dyn_cast<T>(&Location); }
159
160  static void Profile(llvm::FoldingSetNodeID &ID,
161                      const ProgramPoint &Loc,
162                      const ProgramStateRef &state,
163                      bool IsSink) {
164    ID.Add(Loc);
165    ID.AddPointer(state.getPtr());
166    ID.AddBoolean(IsSink);
167  }
168
169  void Profile(llvm::FoldingSetNodeID& ID) const {
170    Profile(ID, getLocation(), getState(), isSink());
171  }
172
173  /// addPredeccessor - Adds a predecessor to the current node, and
174  ///  in tandem add this node as a successor of the other node.
175  void addPredecessor(ExplodedNode *V, ExplodedGraph &G);
176
177  unsigned succ_size() const { return Succs.size(); }
178  unsigned pred_size() const { return Preds.size(); }
179  bool succ_empty() const { return Succs.empty(); }
180  bool pred_empty() const { return Preds.empty(); }
181
182  bool isSink() const { return Succs.getFlag(); }
183
184   bool hasSinglePred() const {
185    return (pred_size() == 1);
186  }
187
188  ExplodedNode *getFirstPred() {
189    return pred_empty() ? NULL : *(pred_begin());
190  }
191
192  const ExplodedNode *getFirstPred() const {
193    return const_cast<ExplodedNode*>(this)->getFirstPred();
194  }
195
196  // Iterators over successor and predecessor vertices.
197  typedef ExplodedNode*       const *       succ_iterator;
198  typedef const ExplodedNode* const * const_succ_iterator;
199  typedef ExplodedNode*       const *       pred_iterator;
200  typedef const ExplodedNode* const * const_pred_iterator;
201
202  pred_iterator pred_begin() { return Preds.begin(); }
203  pred_iterator pred_end() { return Preds.end(); }
204
205  const_pred_iterator pred_begin() const {
206    return const_cast<ExplodedNode*>(this)->pred_begin();
207  }
208  const_pred_iterator pred_end() const {
209    return const_cast<ExplodedNode*>(this)->pred_end();
210  }
211
212  succ_iterator succ_begin() { return Succs.begin(); }
213  succ_iterator succ_end() { return Succs.end(); }
214
215  const_succ_iterator succ_begin() const {
216    return const_cast<ExplodedNode*>(this)->succ_begin();
217  }
218  const_succ_iterator succ_end() const {
219    return const_cast<ExplodedNode*>(this)->succ_end();
220  }
221
222  // For debugging.
223
224public:
225
226  class Auditor {
227  public:
228    virtual ~Auditor();
229    virtual void AddEdge(ExplodedNode *Src, ExplodedNode *Dst) = 0;
230  };
231
232  static void SetAuditor(Auditor* A);
233
234private:
235  void replaceSuccessor(ExplodedNode *node) { Succs.replaceNode(node); }
236  void replacePredecessor(ExplodedNode *node) { Preds.replaceNode(node); }
237};
238
239// FIXME: Is this class necessary?
240class InterExplodedGraphMap {
241  virtual void anchor();
242  llvm::DenseMap<const ExplodedNode*, ExplodedNode*> M;
243  friend class ExplodedGraph;
244
245public:
246  ExplodedNode *getMappedNode(const ExplodedNode *N) const;
247
248  InterExplodedGraphMap() {}
249  virtual ~InterExplodedGraphMap() {}
250};
251
252class ExplodedGraph {
253protected:
254  friend class CoreEngine;
255
256  // Type definitions.
257  typedef std::vector<ExplodedNode *> NodeVector;
258
259  /// The roots of the simulation graph. Usually there will be only
260  /// one, but clients are free to establish multiple subgraphs within a single
261  /// SimulGraph. Moreover, these subgraphs can often merge when paths from
262  /// different roots reach the same state at the same program location.
263  NodeVector Roots;
264
265  /// The nodes in the simulation graph which have been
266  /// specially marked as the endpoint of an abstract simulation path.
267  NodeVector EndNodes;
268
269  /// Nodes - The nodes in the graph.
270  llvm::FoldingSet<ExplodedNode> Nodes;
271
272  /// BVC - Allocator and context for allocating nodes and their predecessor
273  /// and successor groups.
274  BumpVectorContext BVC;
275
276  /// NumNodes - The number of nodes in the graph.
277  unsigned NumNodes;
278
279  /// A list of recently allocated nodes that can potentially be recycled.
280  NodeVector ChangedNodes;
281
282  /// A list of nodes that can be reused.
283  NodeVector FreeNodes;
284
285  /// A flag that indicates whether nodes should be recycled.
286  bool reclaimNodes;
287
288  /// Counter to determine when to reclaim nodes.
289  unsigned reclaimCounter;
290
291public:
292
293  /// \brief Retrieve the node associated with a (Location,State) pair,
294  ///  where the 'Location' is a ProgramPoint in the CFG.  If no node for
295  ///  this pair exists, it is created. IsNew is set to true if
296  ///  the node was freshly created.
297  ExplodedNode *getNode(const ProgramPoint &L, ProgramStateRef State,
298                        bool IsSink = false,
299                        bool* IsNew = 0);
300
301  ExplodedGraph* MakeEmptyGraph() const {
302    return new ExplodedGraph();
303  }
304
305  /// addRoot - Add an untyped node to the set of roots.
306  ExplodedNode *addRoot(ExplodedNode *V) {
307    Roots.push_back(V);
308    return V;
309  }
310
311  /// addEndOfPath - Add an untyped node to the set of EOP nodes.
312  ExplodedNode *addEndOfPath(ExplodedNode *V) {
313    EndNodes.push_back(V);
314    return V;
315  }
316
317  ExplodedGraph();
318
319  ~ExplodedGraph();
320
321  unsigned num_roots() const { return Roots.size(); }
322  unsigned num_eops() const { return EndNodes.size(); }
323
324  bool empty() const { return NumNodes == 0; }
325  unsigned size() const { return NumNodes; }
326
327  // Iterators.
328  typedef ExplodedNode                        NodeTy;
329  typedef llvm::FoldingSet<ExplodedNode>      AllNodesTy;
330  typedef NodeVector::iterator                roots_iterator;
331  typedef NodeVector::const_iterator          const_roots_iterator;
332  typedef NodeVector::iterator                eop_iterator;
333  typedef NodeVector::const_iterator          const_eop_iterator;
334  typedef AllNodesTy::iterator                node_iterator;
335  typedef AllNodesTy::const_iterator          const_node_iterator;
336
337  node_iterator nodes_begin() { return Nodes.begin(); }
338
339  node_iterator nodes_end() { return Nodes.end(); }
340
341  const_node_iterator nodes_begin() const { return Nodes.begin(); }
342
343  const_node_iterator nodes_end() const { return Nodes.end(); }
344
345  roots_iterator roots_begin() { return Roots.begin(); }
346
347  roots_iterator roots_end() { return Roots.end(); }
348
349  const_roots_iterator roots_begin() const { return Roots.begin(); }
350
351  const_roots_iterator roots_end() const { return Roots.end(); }
352
353  eop_iterator eop_begin() { return EndNodes.begin(); }
354
355  eop_iterator eop_end() { return EndNodes.end(); }
356
357  const_eop_iterator eop_begin() const { return EndNodes.begin(); }
358
359  const_eop_iterator eop_end() const { return EndNodes.end(); }
360
361  llvm::BumpPtrAllocator & getAllocator() { return BVC.getAllocator(); }
362  BumpVectorContext &getNodeAllocator() { return BVC; }
363
364  typedef llvm::DenseMap<const ExplodedNode*, ExplodedNode*> NodeMap;
365
366  std::pair<ExplodedGraph*, InterExplodedGraphMap*>
367  Trim(const NodeTy* const* NBeg, const NodeTy* const* NEnd,
368       llvm::DenseMap<const void*, const void*> *InverseMap = 0) const;
369
370  ExplodedGraph* TrimInternal(const ExplodedNode* const * NBeg,
371                              const ExplodedNode* const * NEnd,
372                              InterExplodedGraphMap *M,
373                    llvm::DenseMap<const void*, const void*> *InverseMap) const;
374
375  /// Enable tracking of recently allocated nodes for potential reclamation
376  /// when calling reclaimRecentlyAllocatedNodes().
377  void enableNodeReclamation() { reclaimNodes = true; }
378
379  /// Reclaim "uninteresting" nodes created since the last time this method
380  /// was called.
381  void reclaimRecentlyAllocatedNodes();
382
383private:
384  bool shouldCollect(const ExplodedNode *node);
385  void collectNode(ExplodedNode *node);
386};
387
388class ExplodedNodeSet {
389  typedef llvm::SmallPtrSet<ExplodedNode*,5> ImplTy;
390  ImplTy Impl;
391
392public:
393  ExplodedNodeSet(ExplodedNode *N) {
394    assert (N && !static_cast<ExplodedNode*>(N)->isSink());
395    Impl.insert(N);
396  }
397
398  ExplodedNodeSet() {}
399
400  inline void Add(ExplodedNode *N) {
401    if (N && !static_cast<ExplodedNode*>(N)->isSink()) Impl.insert(N);
402  }
403
404  typedef ImplTy::iterator       iterator;
405  typedef ImplTy::const_iterator const_iterator;
406
407  unsigned size() const { return Impl.size();  }
408  bool empty()    const { return Impl.empty(); }
409  bool erase(ExplodedNode *N) { return Impl.erase(N); }
410
411  void clear() { Impl.clear(); }
412  void insert(const ExplodedNodeSet &S) {
413    assert(&S != this);
414    if (empty())
415      Impl = S.Impl;
416    else
417      Impl.insert(S.begin(), S.end());
418  }
419
420  inline iterator begin() { return Impl.begin(); }
421  inline iterator end()   { return Impl.end();   }
422
423  inline const_iterator begin() const { return Impl.begin(); }
424  inline const_iterator end()   const { return Impl.end();   }
425};
426
427} // end GR namespace
428
429} // end clang namespace
430
431// GraphTraits
432
433namespace llvm {
434  template<> struct GraphTraits<clang::ento::ExplodedNode*> {
435    typedef clang::ento::ExplodedNode NodeType;
436    typedef NodeType::succ_iterator  ChildIteratorType;
437    typedef llvm::df_iterator<NodeType*>      nodes_iterator;
438
439    static inline NodeType* getEntryNode(NodeType* N) {
440      return N;
441    }
442
443    static inline ChildIteratorType child_begin(NodeType* N) {
444      return N->succ_begin();
445    }
446
447    static inline ChildIteratorType child_end(NodeType* N) {
448      return N->succ_end();
449    }
450
451    static inline nodes_iterator nodes_begin(NodeType* N) {
452      return df_begin(N);
453    }
454
455    static inline nodes_iterator nodes_end(NodeType* N) {
456      return df_end(N);
457    }
458  };
459
460  template<> struct GraphTraits<const clang::ento::ExplodedNode*> {
461    typedef const clang::ento::ExplodedNode NodeType;
462    typedef NodeType::const_succ_iterator   ChildIteratorType;
463    typedef llvm::df_iterator<NodeType*>       nodes_iterator;
464
465    static inline NodeType* getEntryNode(NodeType* N) {
466      return N;
467    }
468
469    static inline ChildIteratorType child_begin(NodeType* N) {
470      return N->succ_begin();
471    }
472
473    static inline ChildIteratorType child_end(NodeType* N) {
474      return N->succ_end();
475    }
476
477    static inline nodes_iterator nodes_begin(NodeType* N) {
478      return df_begin(N);
479    }
480
481    static inline nodes_iterator nodes_end(NodeType* N) {
482      return df_end(N);
483    }
484  };
485
486} // end llvm namespace
487
488#endif
489