ExplodedGraph.cpp revision 46e778145c56cd9b42cb399795a294b29cb78b62 
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/CallEvent.h"
17#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
18#include "clang/AST/Stmt.h"
19#include "clang/AST/ParentMap.h"
20#include "llvm/ADT/DenseSet.h"
21#include "llvm/ADT/DenseMap.h"
22#include "llvm/ADT/SmallVector.h"
23#include "llvm/ADT/Statistic.h"
24#include <vector>
25
26using namespace clang;
27using namespace ento;
28
29//===----------------------------------------------------------------------===//
30// Node auditing.
31//===----------------------------------------------------------------------===//
32
33// An out of line virtual method to provide a home for the class vtable.
34ExplodedNode::Auditor::~Auditor() {}
35
36#ifndef NDEBUG
37static ExplodedNode::Auditor* NodeAuditor = 0;
38#endif
39
40void ExplodedNode::SetAuditor(ExplodedNode::Auditor* A) {
41#ifndef NDEBUG
42  NodeAuditor = A;
43#endif
44}
45
46//===----------------------------------------------------------------------===//
47// Cleanup.
48//===----------------------------------------------------------------------===//
49
50static const unsigned CounterTop = 1000;
51
52ExplodedGraph::ExplodedGraph()
53  : NumNodes(0), reclaimNodes(false), reclaimCounter(CounterTop) {}
54
55ExplodedGraph::~ExplodedGraph() {}
56
57//===----------------------------------------------------------------------===//
58// Node reclamation.
59//===----------------------------------------------------------------------===//
60
61bool ExplodedGraph::shouldCollect(const ExplodedNode *node) {
62  // Reclaim all nodes that match *all* the following criteria:
63  //
64  // (1) 1 predecessor (that has one successor)
65  // (2) 1 successor (that has one predecessor)
66  // (3) The ProgramPoint is for a PostStmt.
67  // (4) There is no 'tag' for the ProgramPoint.
68  // (5) The 'store' is the same as the predecessor.
69  // (6) The 'GDM' is the same as the predecessor.
70  // (7) The LocationContext is the same as the predecessor.
71  // (8) The PostStmt is for a non-consumed Stmt or Expr.
72  // (9) The successor is not a CallExpr StmtPoint (so that we would be able to
73  //     find it when retrying a call with no inlining).
74  // FIXME: It may be safe to reclaim PreCall and PostCall nodes as well.
75
76  // Conditions 1 and 2.
77  if (node->pred_size() != 1 || node->succ_size() != 1)
78    return false;
79
80  const ExplodedNode *pred = *(node->pred_begin());
81  if (pred->succ_size() != 1)
82    return false;
83
84  const ExplodedNode *succ = *(node->succ_begin());
85  if (succ->pred_size() != 1)
86    return false;
87
88  // Condition 3.
89  ProgramPoint progPoint = node->getLocation();
90  if (!isa<PostStmt>(progPoint))
91    return false;
92
93  // Condition 4.
94  PostStmt ps = cast<PostStmt>(progPoint);
95  if (ps.getTag())
96    return false;
97
98  if (isa<BinaryOperator>(ps.getStmt()))
99    return false;
100
101  // Conditions 5, 6, and 7.
102  ProgramStateRef state = node->getState();
103  ProgramStateRef pred_state = pred->getState();
104  if (state->store != pred_state->store || state->GDM != pred_state->GDM ||
105      progPoint.getLocationContext() != pred->getLocationContext())
106    return false;
107
108  // Condition 8.
109  if (const Expr *Ex = dyn_cast<Expr>(ps.getStmt())) {
110    ParentMap &PM = progPoint.getLocationContext()->getParentMap();
111    if (!PM.isConsumedExpr(Ex))
112      return false;
113  }
114
115  // Condition 9.
116  const ProgramPoint SuccLoc = succ->getLocation();
117  if (const StmtPoint *SP = dyn_cast<StmtPoint>(&SuccLoc))
118    if (CallEvent::mayBeInlined(SP->getStmt()))
119      return false;
120
121  return true;
122}
123
124void ExplodedGraph::collectNode(ExplodedNode *node) {
125  // Removing a node means:
126  // (a) changing the predecessors successor to the successor of this node
127  // (b) changing the successors predecessor to the predecessor of this node
128  // (c) Putting 'node' onto freeNodes.
129  assert(node->pred_size() == 1 || node->succ_size() == 1);
130  ExplodedNode *pred = *(node->pred_begin());
131  ExplodedNode *succ = *(node->succ_begin());
132  pred->replaceSuccessor(succ);
133  succ->replacePredecessor(pred);
134  FreeNodes.push_back(node);
135  Nodes.RemoveNode(node);
136  --NumNodes;
137  node->~ExplodedNode();
138}
139
140void ExplodedGraph::reclaimRecentlyAllocatedNodes() {
141  if (ChangedNodes.empty())
142    return;
143
144  // Only periodically relcaim nodes so that we can build up a set of
145  // nodes that meet the reclamation criteria.  Freshly created nodes
146  // by definition have no successor, and thus cannot be reclaimed (see below).
147  assert(reclaimCounter > 0);
148  if (--reclaimCounter != 0)
149    return;
150  reclaimCounter = CounterTop;
151
152  for (NodeVector::iterator it = ChangedNodes.begin(), et = ChangedNodes.end();
153       it != et; ++it) {
154    ExplodedNode *node = *it;
155    if (shouldCollect(node))
156      collectNode(node);
157  }
158  ChangedNodes.clear();
159}
160
161//===----------------------------------------------------------------------===//
162// ExplodedNode.
163//===----------------------------------------------------------------------===//
164
165typedef BumpVector<ExplodedNode *> ExplodedNodeVector;
166typedef llvm::PointerUnion<ExplodedNode *, ExplodedNodeVector *> GroupStorage;
167
168void ExplodedNode::addPredecessor(ExplodedNode *V, ExplodedGraph &G) {
169  assert (!V->isSink());
170  Preds.addNode(V, G);
171  V->Succs.addNode(this, G);
172#ifndef NDEBUG
173  if (NodeAuditor) NodeAuditor->AddEdge(V, this);
174#endif
175}
176
177void ExplodedNode::NodeGroup::replaceNode(ExplodedNode *node) {
178  GroupStorage &Storage = reinterpret_cast<GroupStorage&>(P);
179  assert(Storage.is<ExplodedNode *>());
180  Storage = node;
181  assert(Storage.is<ExplodedNode *>());
182}
183
184void ExplodedNode::NodeGroup::addNode(ExplodedNode *N, ExplodedGraph &G) {
185  assert(!getFlag());
186
187  GroupStorage &Storage = reinterpret_cast<GroupStorage&>(P);
188  if (Storage.isNull()) {
189    Storage = N;
190    assert(Storage.is<ExplodedNode *>());
191    return;
192  }
193
194  ExplodedNodeVector *V = Storage.dyn_cast<ExplodedNodeVector *>();
195
196  if (!V) {
197    // Switch from single-node to multi-node representation.
198    ExplodedNode *Old = Storage.get<ExplodedNode *>();
199
200    BumpVectorContext &Ctx = G.getNodeAllocator();
201    V = G.getAllocator().Allocate<ExplodedNodeVector>();
202    new (V) ExplodedNodeVector(Ctx, 4);
203    V->push_back(Old, Ctx);
204
205    Storage = V;
206    assert(!getFlag());
207    assert(Storage.is<ExplodedNodeVector *>());
208  }
209
210  V->push_back(N, G.getNodeAllocator());
211}
212
213unsigned ExplodedNode::NodeGroup::size() const {
214  if (getFlag())
215    return 0;
216
217  const GroupStorage &Storage = reinterpret_cast<const GroupStorage &>(P);
218  if (Storage.isNull())
219    return 0;
220  if (ExplodedNodeVector *V = Storage.dyn_cast<ExplodedNodeVector *>())
221    return V->size();
222  return 1;
223}
224
225ExplodedNode * const *ExplodedNode::NodeGroup::begin() const {
226  if (getFlag())
227    return 0;
228
229  const GroupStorage &Storage = reinterpret_cast<const GroupStorage &>(P);
230  if (Storage.isNull())
231    return 0;
232  if (ExplodedNodeVector *V = Storage.dyn_cast<ExplodedNodeVector *>())
233    return V->begin();
234  return Storage.getAddrOfPtr1();
235}
236
237ExplodedNode * const *ExplodedNode::NodeGroup::end() const {
238  if (getFlag())
239    return 0;
240
241  const GroupStorage &Storage = reinterpret_cast<const GroupStorage &>(P);
242  if (Storage.isNull())
243    return 0;
244  if (ExplodedNodeVector *V = Storage.dyn_cast<ExplodedNodeVector *>())
245    return V->end();
246  return Storage.getAddrOfPtr1() + 1;
247}
248
249ExplodedNode *ExplodedGraph::getNode(const ProgramPoint &L,
250                                     ProgramStateRef State,
251                                     bool IsSink,
252                                     bool* IsNew) {
253  // Profile 'State' to determine if we already have an existing node.
254  llvm::FoldingSetNodeID profile;
255  void *InsertPos = 0;
256
257  NodeTy::Profile(profile, L, State, IsSink);
258  NodeTy* V = Nodes.FindNodeOrInsertPos(profile, InsertPos);
259
260  if (!V) {
261    if (!FreeNodes.empty()) {
262      V = FreeNodes.back();
263      FreeNodes.pop_back();
264    }
265    else {
266      // Allocate a new node.
267      V = (NodeTy*) getAllocator().Allocate<NodeTy>();
268    }
269
270    new (V) NodeTy(L, State, IsSink);
271
272    if (reclaimNodes)
273      ChangedNodes.push_back(V);
274
275    // Insert the node into the node set and return it.
276    Nodes.InsertNode(V, InsertPos);
277    ++NumNodes;
278
279    if (IsNew) *IsNew = true;
280  }
281  else
282    if (IsNew) *IsNew = false;
283
284  return V;
285}
286
287std::pair<ExplodedGraph*, InterExplodedGraphMap*>
288ExplodedGraph::Trim(const NodeTy* const* NBeg, const NodeTy* const* NEnd,
289               llvm::DenseMap<const void*, const void*> *InverseMap) const {
290
291  if (NBeg == NEnd)
292    return std::make_pair((ExplodedGraph*) 0,
293                          (InterExplodedGraphMap*) 0);
294
295  assert (NBeg < NEnd);
296
297  OwningPtr<InterExplodedGraphMap> M(new InterExplodedGraphMap());
298
299  ExplodedGraph* G = TrimInternal(NBeg, NEnd, M.get(), InverseMap);
300
301  return std::make_pair(static_cast<ExplodedGraph*>(G), M.take());
302}
303
304ExplodedGraph*
305ExplodedGraph::TrimInternal(const ExplodedNode* const* BeginSources,
306                            const ExplodedNode* const* EndSources,
307                            InterExplodedGraphMap* M,
308                   llvm::DenseMap<const void*, const void*> *InverseMap) const {
309
310  typedef llvm::DenseSet<const ExplodedNode*> Pass1Ty;
311  Pass1Ty Pass1;
312
313  typedef llvm::DenseMap<const ExplodedNode*, ExplodedNode*> Pass2Ty;
314  Pass2Ty& Pass2 = M->M;
315
316  SmallVector<const ExplodedNode*, 10> WL1, WL2;
317
318  // ===- Pass 1 (reverse DFS) -===
319  for (const ExplodedNode* const* I = BeginSources; I != EndSources; ++I) {
320    assert(*I);
321    WL1.push_back(*I);
322  }
323
324  // Process the first worklist until it is empty.  Because it is a std::list
325  // it acts like a FIFO queue.
326  while (!WL1.empty()) {
327    const ExplodedNode *N = WL1.back();
328    WL1.pop_back();
329
330    // Have we already visited this node?  If so, continue to the next one.
331    if (Pass1.count(N))
332      continue;
333
334    // Otherwise, mark this node as visited.
335    Pass1.insert(N);
336
337    // If this is a root enqueue it to the second worklist.
338    if (N->Preds.empty()) {
339      WL2.push_back(N);
340      continue;
341    }
342
343    // Visit our predecessors and enqueue them.
344    for (ExplodedNode::pred_iterator I = N->Preds.begin(), E = N->Preds.end();
345         I != E; ++I)
346      WL1.push_back(*I);
347  }
348
349  // We didn't hit a root? Return with a null pointer for the new graph.
350  if (WL2.empty())
351    return 0;
352
353  // Create an empty graph.
354  ExplodedGraph* G = MakeEmptyGraph();
355
356  // ===- Pass 2 (forward DFS to construct the new graph) -===
357  while (!WL2.empty()) {
358    const ExplodedNode *N = WL2.back();
359    WL2.pop_back();
360
361    // Skip this node if we have already processed it.
362    if (Pass2.find(N) != Pass2.end())
363      continue;
364
365    // Create the corresponding node in the new graph and record the mapping
366    // from the old node to the new node.
367    ExplodedNode *NewN = G->getNode(N->getLocation(), N->State, N->isSink(), 0);
368    Pass2[N] = NewN;
369
370    // Also record the reverse mapping from the new node to the old node.
371    if (InverseMap) (*InverseMap)[NewN] = N;
372
373    // If this node is a root, designate it as such in the graph.
374    if (N->Preds.empty())
375      G->addRoot(NewN);
376
377    // In the case that some of the intended predecessors of NewN have already
378    // been created, we should hook them up as predecessors.
379
380    // Walk through the predecessors of 'N' and hook up their corresponding
381    // nodes in the new graph (if any) to the freshly created node.
382    for (ExplodedNode::pred_iterator I = N->Preds.begin(), E = N->Preds.end();
383         I != E; ++I) {
384      Pass2Ty::iterator PI = Pass2.find(*I);
385      if (PI == Pass2.end())
386        continue;
387
388      NewN->addPredecessor(PI->second, *G);
389    }
390
391    // In the case that some of the intended successors of NewN have already
392    // been created, we should hook them up as successors.  Otherwise, enqueue
393    // the new nodes from the original graph that should have nodes created
394    // in the new graph.
395    for (ExplodedNode::succ_iterator I = N->Succs.begin(), E = N->Succs.end();
396         I != E; ++I) {
397      Pass2Ty::iterator PI = Pass2.find(*I);
398      if (PI != Pass2.end()) {
399        PI->second->addPredecessor(NewN, *G);
400        continue;
401      }
402
403      // Enqueue nodes to the worklist that were marked during pass 1.
404      if (Pass1.count(*I))
405        WL2.push_back(*I);
406    }
407  }
408
409  return G;
410}
411
412void InterExplodedGraphMap::anchor() { }
413
414ExplodedNode*
415InterExplodedGraphMap::getMappedNode(const ExplodedNode *N) const {
416  llvm::DenseMap<const ExplodedNode*, ExplodedNode*>::const_iterator I =
417    M.find(N);
418
419  return I == M.end() ? 0 : I->second;
420}
421
422