ExplodedGraph.cpp revision 9d0064e802e81d0833e8ccab8978b17c0bac3625 
1//=-- ExplodedGraph.cpp - 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//
13//===----------------------------------------------------------------------===//
14
15#include "clang/StaticAnalyzer/Core/PathSensitive/ExplodedGraph.h"
16#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
17#include "clang/AST/Stmt.h"
18#include "clang/AST/ParentMap.h"
19#include "llvm/ADT/DenseSet.h"
20#include "llvm/ADT/DenseMap.h"
21#include "llvm/ADT/SmallVector.h"
22#include <vector>
23
24using namespace clang;
25using namespace ento;
26
27//===----------------------------------------------------------------------===//
28// Node auditing.
29//===----------------------------------------------------------------------===//
30
31// An out of line virtual method to provide a home for the class vtable.
32ExplodedNode::Auditor::~Auditor() {}
33
34#ifndef NDEBUG
35static ExplodedNode::Auditor* NodeAuditor = 0;
36#endif
37
38void ExplodedNode::SetAuditor(ExplodedNode::Auditor* A) {
39#ifndef NDEBUG
40  NodeAuditor = A;
41#endif
42}
43
44//===----------------------------------------------------------------------===//
45// Cleanup.
46//===----------------------------------------------------------------------===//
47
48typedef std::vector<ExplodedNode*> NodeList;
49static inline NodeList*& getNodeList(void *&p) { return (NodeList*&) p; }
50
51static const unsigned CounterTop = 1000;
52
53ExplodedGraph::ExplodedGraph()
54  : NumNodes(0), recentlyAllocatedNodes(0),
55    freeNodes(0), reclaimNodes(false),
56    reclaimCounter(CounterTop) {}
57
58ExplodedGraph::~ExplodedGraph() {
59  if (reclaimNodes) {
60    delete getNodeList(recentlyAllocatedNodes);
61    delete getNodeList(freeNodes);
62  }
63}
64
65//===----------------------------------------------------------------------===//
66// Node reclamation.
67//===----------------------------------------------------------------------===//
68
69void ExplodedGraph::reclaimRecentlyAllocatedNodes() {
70  if (!recentlyAllocatedNodes)
71    return;
72
73  // Only periodically relcaim nodes so that we can build up a set of
74  // nodes that meet the reclamation criteria.  Freshly created nodes
75  // by definition have no successor, and thus cannot be reclaimed (see below).
76  assert(reclaimCounter > 0);
77  if (--reclaimCounter != 0)
78    return;
79  reclaimCounter = CounterTop;
80
81  NodeList &nl = *getNodeList(recentlyAllocatedNodes);
82
83  // Reclaimn all nodes that match *all* the following criteria:
84  //
85  // (1) 1 predecessor (that has one successor)
86  // (2) 1 successor (that has one predecessor)
87  // (3) The ProgramPoint is for a PostStmt.
88  // (4) There is no 'tag' for the ProgramPoint.
89  // (5) The 'store' is the same as the predecessor.
90  // (6) The 'GDM' is the same as the predecessor.
91  // (7) The LocationContext is the same as the predecessor.
92  // (8) The PostStmt is for a non-consumed Stmt or Expr.
93
94  for (NodeList::iterator i = nl.begin(), e = nl.end() ; i != e; ++i) {
95    ExplodedNode *node = *i;
96
97    // Conditions 1 and 2.
98    if (node->pred_size() != 1 || node->succ_size() != 1)
99      continue;
100
101    ExplodedNode *pred = *(node->pred_begin());
102    if (pred->succ_size() != 1)
103      continue;
104
105    ExplodedNode *succ = *(node->succ_begin());
106    if (succ->pred_size() != 1)
107      continue;
108
109    // Condition 3.
110    ProgramPoint progPoint = node->getLocation();
111    if (!isa<PostStmt>(progPoint) ||
112        (isa<CallEnter>(progPoint) || isa<CallExit>(progPoint)))
113      continue;
114    // Condition 4.
115    PostStmt ps = cast<PostStmt>(progPoint);
116    if (ps.getTag())
117      continue;
118
119    if (isa<BinaryOperator>(ps.getStmt()))
120      continue;
121
122    // Conditions 5, 6, and 7.
123    const ProgramState *state = node->getState();
124    const ProgramState *pred_state = pred->getState();
125    if (state->store != pred_state->store || state->GDM != pred_state->GDM ||
126        progPoint.getLocationContext() != pred->getLocationContext())
127      continue;
128
129    // Condition 8.
130    if (const Expr *Ex = dyn_cast<Expr>(ps.getStmt())) {
131      ParentMap &PM = progPoint.getLocationContext()->getParentMap();
132      if (!PM.isConsumedExpr(Ex))
133        continue;
134    }
135
136    // If we reach here, we can remove the node.  This means:
137    // (a) changing the predecessors successor to the successor of this node
138    // (b) changing the successors predecessor to the predecessor of this node
139    // (c) Putting 'node' onto freeNodes.
140    pred->replaceSuccessor(succ);
141    succ->replacePredecessor(pred);
142    if (!freeNodes)
143      freeNodes = new NodeList();
144    getNodeList(freeNodes)->push_back(node);
145    Nodes.RemoveNode(node);
146    --NumNodes;
147    node->~ExplodedNode();
148  }
149
150  nl.clear();
151}
152
153//===----------------------------------------------------------------------===//
154// ExplodedNode.
155//===----------------------------------------------------------------------===//
156
157static inline BumpVector<ExplodedNode*>& getVector(void *P) {
158  return *reinterpret_cast<BumpVector<ExplodedNode*>*>(P);
159}
160
161void ExplodedNode::addPredecessor(ExplodedNode *V, ExplodedGraph &G) {
162  assert (!V->isSink());
163  Preds.addNode(V, G);
164  V->Succs.addNode(this, G);
165#ifndef NDEBUG
166  if (NodeAuditor) NodeAuditor->AddEdge(V, this);
167#endif
168}
169
170void ExplodedNode::NodeGroup::replaceNode(ExplodedNode *node) {
171  assert(getKind() == Size1);
172  P = reinterpret_cast<uintptr_t>(node);
173  assert(getKind() == Size1);
174}
175
176void ExplodedNode::NodeGroup::addNode(ExplodedNode *N, ExplodedGraph &G) {
177  assert((reinterpret_cast<uintptr_t>(N) & Mask) == 0x0);
178  assert(!getFlag());
179
180  if (getKind() == Size1) {
181    if (ExplodedNode *NOld = getNode()) {
182      BumpVectorContext &Ctx = G.getNodeAllocator();
183      BumpVector<ExplodedNode*> *V =
184        G.getAllocator().Allocate<BumpVector<ExplodedNode*> >();
185      new (V) BumpVector<ExplodedNode*>(Ctx, 4);
186
187      assert((reinterpret_cast<uintptr_t>(V) & Mask) == 0x0);
188      V->push_back(NOld, Ctx);
189      V->push_back(N, Ctx);
190      P = reinterpret_cast<uintptr_t>(V) | SizeOther;
191      assert(getPtr() == (void*) V);
192      assert(getKind() == SizeOther);
193    }
194    else {
195      P = reinterpret_cast<uintptr_t>(N);
196      assert(getKind() == Size1);
197    }
198  }
199  else {
200    assert(getKind() == SizeOther);
201    getVector(getPtr()).push_back(N, G.getNodeAllocator());
202  }
203}
204
205unsigned ExplodedNode::NodeGroup::size() const {
206  if (getFlag())
207    return 0;
208
209  if (getKind() == Size1)
210    return getNode() ? 1 : 0;
211  else
212    return getVector(getPtr()).size();
213}
214
215ExplodedNode **ExplodedNode::NodeGroup::begin() const {
216  if (getFlag())
217    return NULL;
218
219  if (getKind() == Size1)
220    return (ExplodedNode**) (getPtr() ? &P : NULL);
221  else
222    return const_cast<ExplodedNode**>(&*(getVector(getPtr()).begin()));
223}
224
225ExplodedNode** ExplodedNode::NodeGroup::end() const {
226  if (getFlag())
227    return NULL;
228
229  if (getKind() == Size1)
230    return (ExplodedNode**) (getPtr() ? &P+1 : NULL);
231  else {
232    // Dereferencing end() is undefined behaviour. The vector is not empty, so
233    // we can dereference the last elem and then add 1 to the result.
234    return const_cast<ExplodedNode**>(getVector(getPtr()).end());
235  }
236}
237
238ExplodedNode *ExplodedGraph::getNode(const ProgramPoint &L,
239                                     const ProgramState *State,
240                                     bool IsSink,
241                                     bool* IsNew) {
242  // Profile 'State' to determine if we already have an existing node.
243  llvm::FoldingSetNodeID profile;
244  void *InsertPos = 0;
245
246  NodeTy::Profile(profile, L, State, IsSink);
247  NodeTy* V = Nodes.FindNodeOrInsertPos(profile, InsertPos);
248
249  if (!V) {
250    if (freeNodes && !getNodeList(freeNodes)->empty()) {
251      NodeList *nl = getNodeList(freeNodes);
252      V = nl->back();
253      nl->pop_back();
254    }
255    else {
256      // Allocate a new node.
257      V = (NodeTy*) getAllocator().Allocate<NodeTy>();
258    }
259
260    new (V) NodeTy(L, State, IsSink);
261
262    if (reclaimNodes) {
263      if (!recentlyAllocatedNodes)
264        recentlyAllocatedNodes = new NodeList();
265      getNodeList(recentlyAllocatedNodes)->push_back(V);
266    }
267
268    // Insert the node into the node set and return it.
269    Nodes.InsertNode(V, InsertPos);
270
271    ++NumNodes;
272
273    if (IsNew) *IsNew = true;
274  }
275  else
276    if (IsNew) *IsNew = false;
277
278  return V;
279}
280
281std::pair<ExplodedGraph*, InterExplodedGraphMap*>
282ExplodedGraph::Trim(const NodeTy* const* NBeg, const NodeTy* const* NEnd,
283               llvm::DenseMap<const void*, const void*> *InverseMap) const {
284
285  if (NBeg == NEnd)
286    return std::make_pair((ExplodedGraph*) 0,
287                          (InterExplodedGraphMap*) 0);
288
289  assert (NBeg < NEnd);
290
291  llvm::OwningPtr<InterExplodedGraphMap> M(new InterExplodedGraphMap());
292
293  ExplodedGraph* G = TrimInternal(NBeg, NEnd, M.get(), InverseMap);
294
295  return std::make_pair(static_cast<ExplodedGraph*>(G), M.take());
296}
297
298ExplodedGraph*
299ExplodedGraph::TrimInternal(const ExplodedNode* const* BeginSources,
300                            const ExplodedNode* const* EndSources,
301                            InterExplodedGraphMap* M,
302                   llvm::DenseMap<const void*, const void*> *InverseMap) const {
303
304  typedef llvm::DenseSet<const ExplodedNode*> Pass1Ty;
305  Pass1Ty Pass1;
306
307  typedef llvm::DenseMap<const ExplodedNode*, ExplodedNode*> Pass2Ty;
308  Pass2Ty& Pass2 = M->M;
309
310  SmallVector<const ExplodedNode*, 10> WL1, WL2;
311
312  // ===- Pass 1 (reverse DFS) -===
313  for (const ExplodedNode* const* I = BeginSources; I != EndSources; ++I) {
314    assert(*I);
315    WL1.push_back(*I);
316  }
317
318  // Process the first worklist until it is empty.  Because it is a std::list
319  // it acts like a FIFO queue.
320  while (!WL1.empty()) {
321    const ExplodedNode *N = WL1.back();
322    WL1.pop_back();
323
324    // Have we already visited this node?  If so, continue to the next one.
325    if (Pass1.count(N))
326      continue;
327
328    // Otherwise, mark this node as visited.
329    Pass1.insert(N);
330
331    // If this is a root enqueue it to the second worklist.
332    if (N->Preds.empty()) {
333      WL2.push_back(N);
334      continue;
335    }
336
337    // Visit our predecessors and enqueue them.
338    for (ExplodedNode** I=N->Preds.begin(), **E=N->Preds.end(); I!=E; ++I)
339      WL1.push_back(*I);
340  }
341
342  // We didn't hit a root? Return with a null pointer for the new graph.
343  if (WL2.empty())
344    return 0;
345
346  // Create an empty graph.
347  ExplodedGraph* G = MakeEmptyGraph();
348
349  // ===- Pass 2 (forward DFS to construct the new graph) -===
350  while (!WL2.empty()) {
351    const ExplodedNode *N = WL2.back();
352    WL2.pop_back();
353
354    // Skip this node if we have already processed it.
355    if (Pass2.find(N) != Pass2.end())
356      continue;
357
358    // Create the corresponding node in the new graph and record the mapping
359    // from the old node to the new node.
360    ExplodedNode *NewN = G->getNode(N->getLocation(), N->State, N->isSink(), 0);
361    Pass2[N] = NewN;
362
363    // Also record the reverse mapping from the new node to the old node.
364    if (InverseMap) (*InverseMap)[NewN] = N;
365
366    // If this node is a root, designate it as such in the graph.
367    if (N->Preds.empty())
368      G->addRoot(NewN);
369
370    // In the case that some of the intended predecessors of NewN have already
371    // been created, we should hook them up as predecessors.
372
373    // Walk through the predecessors of 'N' and hook up their corresponding
374    // nodes in the new graph (if any) to the freshly created node.
375    for (ExplodedNode **I=N->Preds.begin(), **E=N->Preds.end(); I!=E; ++I) {
376      Pass2Ty::iterator PI = Pass2.find(*I);
377      if (PI == Pass2.end())
378        continue;
379
380      NewN->addPredecessor(PI->second, *G);
381    }
382
383    // In the case that some of the intended successors of NewN have already
384    // been created, we should hook them up as successors.  Otherwise, enqueue
385    // the new nodes from the original graph that should have nodes created
386    // in the new graph.
387    for (ExplodedNode **I=N->Succs.begin(), **E=N->Succs.end(); I!=E; ++I) {
388      Pass2Ty::iterator PI = Pass2.find(*I);
389      if (PI != Pass2.end()) {
390        PI->second->addPredecessor(NewN, *G);
391        continue;
392      }
393
394      // Enqueue nodes to the worklist that were marked during pass 1.
395      if (Pass1.count(*I))
396        WL2.push_back(*I);
397    }
398  }
399
400  return G;
401}
402
403void InterExplodedGraphMap::anchor() { }
404
405ExplodedNode*
406InterExplodedGraphMap::getMappedNode(const ExplodedNode *N) const {
407  llvm::DenseMap<const ExplodedNode*, ExplodedNode*>::const_iterator I =
408    M.find(N);
409
410  return I == M.end() ? 0 : I->second;
411}
412
413