ExplodedGraph.h revision 0a6e09f67c719c318856be19d57e19972101f62c
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/AST/Decl.h"
23#include "clang/Analysis/AnalysisContext.h"
24#include "clang/Analysis/ProgramPoint.h"
25#include "clang/Analysis/Support/BumpVector.h"
26#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
27#include "llvm/ADT/DepthFirstIterator.h"
28#include "llvm/ADT/FoldingSet.h"
29#include "llvm/ADT/GraphTraits.h"
30#include "llvm/ADT/OwningPtr.h"
31#include "llvm/ADT/SmallPtrSet.h"
32#include "llvm/ADT/SmallVector.h"
33#include "llvm/Support/Allocator.h"
34#include "llvm/Support/Casting.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, const 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  const ProgramStateRef &getState() const { return State; }
156
157  template <typename T>
158  const T* getLocationAs() const LLVM_LVALUE_FUNCTION {
159    return dyn_cast<T>(&Location);
160  }
161
162#if LLVM_HAS_RVALUE_REFERENCE_THIS
163  template <typename T>
164  void getLocationAs() && LLVM_DELETED_FUNCTION;
165#endif
166
167  static void Profile(llvm::FoldingSetNodeID &ID,
168                      const ProgramPoint &Loc,
169                      const ProgramStateRef &state,
170                      bool IsSink) {
171    ID.Add(Loc);
172    ID.AddPointer(state.getPtr());
173    ID.AddBoolean(IsSink);
174  }
175
176  void Profile(llvm::FoldingSetNodeID& ID) const {
177    // We avoid copy constructors by not using accessors.
178    Profile(ID, Location, State, isSink());
179  }
180
181  /// addPredeccessor - Adds a predecessor to the current node, and
182  ///  in tandem add this node as a successor of the other node.
183  void addPredecessor(ExplodedNode *V, ExplodedGraph &G);
184
185  unsigned succ_size() const { return Succs.size(); }
186  unsigned pred_size() const { return Preds.size(); }
187  bool succ_empty() const { return Succs.empty(); }
188  bool pred_empty() const { return Preds.empty(); }
189
190  bool isSink() const { return Succs.getFlag(); }
191
192   bool hasSinglePred() const {
193    return (pred_size() == 1);
194  }
195
196  ExplodedNode *getFirstPred() {
197    return pred_empty() ? NULL : *(pred_begin());
198  }
199
200  const ExplodedNode *getFirstPred() const {
201    return const_cast<ExplodedNode*>(this)->getFirstPred();
202  }
203
204  // Iterators over successor and predecessor vertices.
205  typedef ExplodedNode*       const *       succ_iterator;
206  typedef const ExplodedNode* const * const_succ_iterator;
207  typedef ExplodedNode*       const *       pred_iterator;
208  typedef const ExplodedNode* const * const_pred_iterator;
209
210  pred_iterator pred_begin() { return Preds.begin(); }
211  pred_iterator pred_end() { return Preds.end(); }
212
213  const_pred_iterator pred_begin() const {
214    return const_cast<ExplodedNode*>(this)->pred_begin();
215  }
216  const_pred_iterator pred_end() const {
217    return const_cast<ExplodedNode*>(this)->pred_end();
218  }
219
220  succ_iterator succ_begin() { return Succs.begin(); }
221  succ_iterator succ_end() { return Succs.end(); }
222
223  const_succ_iterator succ_begin() const {
224    return const_cast<ExplodedNode*>(this)->succ_begin();
225  }
226  const_succ_iterator succ_end() const {
227    return const_cast<ExplodedNode*>(this)->succ_end();
228  }
229
230  // For debugging.
231
232public:
233
234  class Auditor {
235  public:
236    virtual ~Auditor();
237    virtual void AddEdge(ExplodedNode *Src, ExplodedNode *Dst) = 0;
238  };
239
240  static void SetAuditor(Auditor* A);
241
242private:
243  void replaceSuccessor(ExplodedNode *node) { Succs.replaceNode(node); }
244  void replacePredecessor(ExplodedNode *node) { Preds.replaceNode(node); }
245};
246
247// FIXME: Is this class necessary?
248class InterExplodedGraphMap {
249  virtual void anchor();
250  llvm::DenseMap<const ExplodedNode*, ExplodedNode*> M;
251  friend class ExplodedGraph;
252
253public:
254  ExplodedNode *getMappedNode(const ExplodedNode *N) const;
255
256  InterExplodedGraphMap() {}
257  virtual ~InterExplodedGraphMap() {}
258};
259
260class ExplodedGraph {
261protected:
262  friend class CoreEngine;
263
264  // Type definitions.
265  typedef std::vector<ExplodedNode *> NodeVector;
266
267  /// The roots of the simulation graph. Usually there will be only
268  /// one, but clients are free to establish multiple subgraphs within a single
269  /// SimulGraph. Moreover, these subgraphs can often merge when paths from
270  /// different roots reach the same state at the same program location.
271  NodeVector Roots;
272
273  /// The nodes in the simulation graph which have been
274  /// specially marked as the endpoint of an abstract simulation path.
275  NodeVector EndNodes;
276
277  /// Nodes - The nodes in the graph.
278  llvm::FoldingSet<ExplodedNode> Nodes;
279
280  /// BVC - Allocator and context for allocating nodes and their predecessor
281  /// and successor groups.
282  BumpVectorContext BVC;
283
284  /// NumNodes - The number of nodes in the graph.
285  unsigned NumNodes;
286
287  /// A list of recently allocated nodes that can potentially be recycled.
288  NodeVector ChangedNodes;
289
290  /// A list of nodes that can be reused.
291  NodeVector FreeNodes;
292
293  /// Determines how often nodes are reclaimed.
294  ///
295  /// If this is 0, nodes will never be reclaimed.
296  unsigned ReclaimNodeInterval;
297
298  /// Counter to determine when to reclaim nodes.
299  unsigned ReclaimCounter;
300
301public:
302
303  /// \brief Retrieve the node associated with a (Location,State) pair,
304  ///  where the 'Location' is a ProgramPoint in the CFG.  If no node for
305  ///  this pair exists, it is created. IsNew is set to true if
306  ///  the node was freshly created.
307  ExplodedNode *getNode(const ProgramPoint &L, ProgramStateRef State,
308                        bool IsSink = false,
309                        bool* IsNew = 0);
310
311  ExplodedGraph* MakeEmptyGraph() const {
312    return new ExplodedGraph();
313  }
314
315  /// addRoot - Add an untyped node to the set of roots.
316  ExplodedNode *addRoot(ExplodedNode *V) {
317    Roots.push_back(V);
318    return V;
319  }
320
321  /// addEndOfPath - Add an untyped node to the set of EOP nodes.
322  ExplodedNode *addEndOfPath(ExplodedNode *V) {
323    EndNodes.push_back(V);
324    return V;
325  }
326
327  ExplodedGraph();
328
329  ~ExplodedGraph();
330
331  unsigned num_roots() const { return Roots.size(); }
332  unsigned num_eops() const { return EndNodes.size(); }
333
334  bool empty() const { return NumNodes == 0; }
335  unsigned size() const { return NumNodes; }
336
337  // Iterators.
338  typedef ExplodedNode                        NodeTy;
339  typedef llvm::FoldingSet<ExplodedNode>      AllNodesTy;
340  typedef NodeVector::iterator                roots_iterator;
341  typedef NodeVector::const_iterator          const_roots_iterator;
342  typedef NodeVector::iterator                eop_iterator;
343  typedef NodeVector::const_iterator          const_eop_iterator;
344  typedef AllNodesTy::iterator                node_iterator;
345  typedef AllNodesTy::const_iterator          const_node_iterator;
346
347  node_iterator nodes_begin() { return Nodes.begin(); }
348
349  node_iterator nodes_end() { return Nodes.end(); }
350
351  const_node_iterator nodes_begin() const { return Nodes.begin(); }
352
353  const_node_iterator nodes_end() const { return Nodes.end(); }
354
355  roots_iterator roots_begin() { return Roots.begin(); }
356
357  roots_iterator roots_end() { return Roots.end(); }
358
359  const_roots_iterator roots_begin() const { return Roots.begin(); }
360
361  const_roots_iterator roots_end() const { return Roots.end(); }
362
363  eop_iterator eop_begin() { return EndNodes.begin(); }
364
365  eop_iterator eop_end() { return EndNodes.end(); }
366
367  const_eop_iterator eop_begin() const { return EndNodes.begin(); }
368
369  const_eop_iterator eop_end() const { return EndNodes.end(); }
370
371  llvm::BumpPtrAllocator & getAllocator() { return BVC.getAllocator(); }
372  BumpVectorContext &getNodeAllocator() { return BVC; }
373
374  typedef llvm::DenseMap<const ExplodedNode*, ExplodedNode*> NodeMap;
375
376  std::pair<ExplodedGraph*, InterExplodedGraphMap*>
377  Trim(const NodeTy* const* NBeg, const NodeTy* const* NEnd,
378       llvm::DenseMap<const void*, const void*> *InverseMap = 0) const;
379
380  ExplodedGraph* TrimInternal(const ExplodedNode* const * NBeg,
381                              const ExplodedNode* const * NEnd,
382                              InterExplodedGraphMap *M,
383                    llvm::DenseMap<const void*, const void*> *InverseMap) const;
384
385  /// Enable tracking of recently allocated nodes for potential reclamation
386  /// when calling reclaimRecentlyAllocatedNodes().
387  void enableNodeReclamation(unsigned Interval) {
388    ReclaimCounter = ReclaimNodeInterval = Interval;
389  }
390
391  /// Reclaim "uninteresting" nodes created since the last time this method
392  /// was called.
393  void reclaimRecentlyAllocatedNodes();
394
395private:
396  bool shouldCollect(const ExplodedNode *node);
397  void collectNode(ExplodedNode *node);
398};
399
400class ExplodedNodeSet {
401  typedef llvm::SmallPtrSet<ExplodedNode*,5> ImplTy;
402  ImplTy Impl;
403
404public:
405  ExplodedNodeSet(ExplodedNode *N) {
406    assert (N && !static_cast<ExplodedNode*>(N)->isSink());
407    Impl.insert(N);
408  }
409
410  ExplodedNodeSet() {}
411
412  inline void Add(ExplodedNode *N) {
413    if (N && !static_cast<ExplodedNode*>(N)->isSink()) Impl.insert(N);
414  }
415
416  typedef ImplTy::iterator       iterator;
417  typedef ImplTy::const_iterator const_iterator;
418
419  unsigned size() const { return Impl.size();  }
420  bool empty()    const { return Impl.empty(); }
421  bool erase(ExplodedNode *N) { return Impl.erase(N); }
422
423  void clear() { Impl.clear(); }
424  void insert(const ExplodedNodeSet &S) {
425    assert(&S != this);
426    if (empty())
427      Impl = S.Impl;
428    else
429      Impl.insert(S.begin(), S.end());
430  }
431
432  inline iterator begin() { return Impl.begin(); }
433  inline iterator end()   { return Impl.end();   }
434
435  inline const_iterator begin() const { return Impl.begin(); }
436  inline const_iterator end()   const { return Impl.end();   }
437};
438
439} // end GR namespace
440
441} // end clang namespace
442
443// GraphTraits
444
445namespace llvm {
446  template<> struct GraphTraits<clang::ento::ExplodedNode*> {
447    typedef clang::ento::ExplodedNode NodeType;
448    typedef NodeType::succ_iterator  ChildIteratorType;
449    typedef llvm::df_iterator<NodeType*>      nodes_iterator;
450
451    static inline NodeType* getEntryNode(NodeType* N) {
452      return N;
453    }
454
455    static inline ChildIteratorType child_begin(NodeType* N) {
456      return N->succ_begin();
457    }
458
459    static inline ChildIteratorType child_end(NodeType* N) {
460      return N->succ_end();
461    }
462
463    static inline nodes_iterator nodes_begin(NodeType* N) {
464      return df_begin(N);
465    }
466
467    static inline nodes_iterator nodes_end(NodeType* N) {
468      return df_end(N);
469    }
470  };
471
472  template<> struct GraphTraits<const clang::ento::ExplodedNode*> {
473    typedef const clang::ento::ExplodedNode NodeType;
474    typedef NodeType::const_succ_iterator   ChildIteratorType;
475    typedef llvm::df_iterator<NodeType*>       nodes_iterator;
476
477    static inline NodeType* getEntryNode(NodeType* N) {
478      return N;
479    }
480
481    static inline ChildIteratorType child_begin(NodeType* N) {
482      return N->succ_begin();
483    }
484
485    static inline ChildIteratorType child_end(NodeType* N) {
486      return N->succ_end();
487    }
488
489    static inline nodes_iterator nodes_begin(NodeType* N) {
490      return df_begin(N);
491    }
492
493    static inline nodes_iterator nodes_end(NodeType* N) {
494      return df_end(N);
495    }
496  };
497
498} // end llvm namespace
499
500#endif
501