lib/StaticAnalyzer/Core/ExplodedGraph.cpp

   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/PathSensitive/ExplodedGraph.h"
  16 #include "clang/StaticAnalyzer/PathSensitive/GRState.h"
  17 #include "clang/AST/Stmt.h"
  18 #include "llvm/ADT/DenseSet.h"
  19 #include "llvm/ADT/DenseMap.h"
  20 #include "llvm/ADT/SmallVector.h"
  21 #include <vector>
  22
  23 using namespace clang;
  24 using namespace ento;
  25
  26 //===----------------------------------------------------------------------===//
  27 // Node auditing.
  28 //===----------------------------------------------------------------------===//
  29
  30 // An out of line virtual method to provide a home for the class vtable.
  31 ExplodedNode::Auditor::~Auditor() {}
  32
  33 #ifndef NDEBUG
  34 static ExplodedNode::Auditor* NodeAuditor = 0;
  35 #endif
  36
  37 void ExplodedNode::SetAuditor(ExplodedNode::Auditor* A) {
  38 #ifndef NDEBUG
  39   NodeAuditor = A;
  40 #endif
  41 }
  42
  43 //===----------------------------------------------------------------------===//
  44 // ExplodedNode.
  45 //===----------------------------------------------------------------------===//
  46
  47 static inline BumpVector<ExplodedNode*>& getVector(void* P) {
  48   return *reinterpret_cast<BumpVector<ExplodedNode*>*>(P);
  49 }
  50
  51 void ExplodedNode::addPredecessor(ExplodedNode* V, ExplodedGraph &G) {
  52   assert (!V->isSink());
  53   Preds.addNode(V, G);
  54   V->Succs.addNode(this, G);
  55 #ifndef NDEBUG
  56   if (NodeAuditor) NodeAuditor->AddEdge(V, this);
  57 #endif
  58 }
  59
  60 void ExplodedNode::NodeGroup::addNode(ExplodedNode* N, ExplodedGraph &G) {
  61   assert((reinterpret_cast<uintptr_t>(N) & Mask) == 0x0);
  62   assert(!getFlag());
  63
  64   if (getKind() == Size1) {
  65     if (ExplodedNode* NOld = getNode()) {
  66       BumpVectorContext &Ctx = G.getNodeAllocator();
  67       BumpVector<ExplodedNode*> *V =
  68         G.getAllocator().Allocate<BumpVector<ExplodedNode*> >();
  69       new (V) BumpVector<ExplodedNode*>(Ctx, 4);
  70
  71       assert((reinterpret_cast<uintptr_t>(V) & Mask) == 0x0);
  72       V->push_back(NOld, Ctx);
  73       V->push_back(N, Ctx);
  74       P = reinterpret_cast<uintptr_t>(V) | SizeOther;
  75       assert(getPtr() == (void*) V);
  76       assert(getKind() == SizeOther);
  77     }
  78     else {
  79       P = reinterpret_cast<uintptr_t>(N);
  80       assert(getKind() == Size1);
  81     }
  82   }
  83   else {
  84     assert(getKind() == SizeOther);
  85     getVector(getPtr()).push_back(N, G.getNodeAllocator());
  86   }
  87 }
  88
  89 unsigned ExplodedNode::NodeGroup::size() const {
  90   if (getFlag())
  91     return 0;
  92
  93   if (getKind() == Size1)
  94     return getNode() ? 1 : 0;
  95   else
  96     return getVector(getPtr()).size();
  97 }
  98
  99 ExplodedNode **ExplodedNode::NodeGroup::begin() const {
 100   if (getFlag())
 101     return NULL;
 102
 103   if (getKind() == Size1)
 104     return (ExplodedNode**) (getPtr() ? &P : NULL);
 105   else
 106     return const_cast<ExplodedNode**>(&*(getVector(getPtr()).begin()));
 107 }
 108
 109 ExplodedNode** ExplodedNode::NodeGroup::end() const {
 110   if (getFlag())
 111     return NULL;
 112
 113   if (getKind() == Size1)
 114     return (ExplodedNode**) (getPtr() ? &P+1 : NULL);
 115   else {
 116     // Dereferencing end() is undefined behaviour. The vector is not empty, so
 117     // we can dereference the last elem and then add 1 to the result.
 118     return const_cast<ExplodedNode**>(getVector(getPtr()).end());
 119   }
 120 }
 121
 122 ExplodedNode *ExplodedGraph::getNode(const ProgramPoint& L,
 123                                      const GRState* State, bool* IsNew) {
 124   // Profile 'State' to determine if we already have an existing node.
 125   llvm::FoldingSetNodeID profile;
 126   void* InsertPos = 0;
 127
 128   NodeTy::Profile(profile, L, State);
 129   NodeTy* V = Nodes.FindNodeOrInsertPos(profile, InsertPos);
 130
 131   if (!V) {
 132     // Allocate a new node.
 133     V = (NodeTy*) getAllocator().Allocate<NodeTy>();
 134     new (V) NodeTy(L, State);
 135
 136     // Insert the node into the node set and return it.
 137     Nodes.InsertNode(V, InsertPos);
 138
 139     ++NumNodes;
 140
 141     if (IsNew) *IsNew = true;
 142   }
 143   else
 144     if (IsNew) *IsNew = false;
 145
 146   return V;
 147 }
 148
 149 std::pair<ExplodedGraph*, InterExplodedGraphMap*>
 150 ExplodedGraph::Trim(const NodeTy* const* NBeg, const NodeTy* const* NEnd,
 151                llvm::DenseMap<const void*, const void*> *InverseMap) const {
 152
 153   if (NBeg == NEnd)
 154     return std::make_pair((ExplodedGraph*) 0,
 155                           (InterExplodedGraphMap*) 0);
 156
 157   assert (NBeg < NEnd);
 158
 159   llvm::OwningPtr<InterExplodedGraphMap> M(new InterExplodedGraphMap());
 160
 161   ExplodedGraph* G = TrimInternal(NBeg, NEnd, M.get(), InverseMap);
 162
 163   return std::make_pair(static_cast<ExplodedGraph*>(G), M.take());
 164 }
 165
 166 ExplodedGraph*
 167 ExplodedGraph::TrimInternal(const ExplodedNode* const* BeginSources,
 168                             const ExplodedNode* const* EndSources,
 169                             InterExplodedGraphMap* M,
 170                    llvm::DenseMap<const void*, const void*> *InverseMap) const {
 171
 172   typedef llvm::DenseSet<const ExplodedNode*> Pass1Ty;
 173   Pass1Ty Pass1;
 174
 175   typedef llvm::DenseMap<const ExplodedNode*, ExplodedNode*> Pass2Ty;
 176   Pass2Ty& Pass2 = M->M;
 177
 178   llvm::SmallVector<const ExplodedNode*, 10> WL1, WL2;
 179
 180   // ===- Pass 1 (reverse DFS) -===
 181   for (const ExplodedNode* const* I = BeginSources; I != EndSources; ++I) {
 182     assert(*I);
 183     WL1.push_back(*I);
 184   }
 185
 186   // Process the first worklist until it is empty.  Because it is a std::list
 187   // it acts like a FIFO queue.
 188   while (!WL1.empty()) {
 189     const ExplodedNode *N = WL1.back();
 190     WL1.pop_back();
 191
 192     // Have we already visited this node?  If so, continue to the next one.
 193     if (Pass1.count(N))
 194       continue;
 195
 196     // Otherwise, mark this node as visited.
 197     Pass1.insert(N);
 198
 199     // If this is a root enqueue it to the second worklist.
 200     if (N->Preds.empty()) {
 201       WL2.push_back(N);
 202       continue;
 203     }
 204
 205     // Visit our predecessors and enqueue them.
 206     for (ExplodedNode** I=N->Preds.begin(), **E=N->Preds.end(); I!=E; ++I)
 207       WL1.push_back(*I);
 208   }
 209
 210   // We didn't hit a root? Return with a null pointer for the new graph.
 211   if (WL2.empty())
 212     return 0;
 213
 214   // Create an empty graph.
 215   ExplodedGraph* G = MakeEmptyGraph();
 216
 217   // ===- Pass 2 (forward DFS to construct the new graph) -===
 218   while (!WL2.empty()) {
 219     const ExplodedNode* N = WL2.back();
 220     WL2.pop_back();
 221
 222     // Skip this node if we have already processed it.
 223     if (Pass2.find(N) != Pass2.end())
 224       continue;
 225
 226     // Create the corresponding node in the new graph and record the mapping
 227     // from the old node to the new node.
 228     ExplodedNode* NewN = G->getNode(N->getLocation(), N->State, NULL);
 229     Pass2[N] = NewN;
 230
 231     // Also record the reverse mapping from the new node to the old node.
 232     if (InverseMap) (*InverseMap)[NewN] = N;
 233
 234     // If this node is a root, designate it as such in the graph.
 235     if (N->Preds.empty())
 236       G->addRoot(NewN);
 237
 238     // In the case that some of the intended predecessors of NewN have already
 239     // been created, we should hook them up as predecessors.
 240
 241     // Walk through the predecessors of 'N' and hook up their corresponding
 242     // nodes in the new graph (if any) to the freshly created node.
 243     for (ExplodedNode **I=N->Preds.begin(), **E=N->Preds.end(); I!=E; ++I) {
 244       Pass2Ty::iterator PI = Pass2.find(*I);
 245       if (PI == Pass2.end())
 246         continue;
 247
 248       NewN->addPredecessor(PI->second, *G);
 249     }
 250
 251     // In the case that some of the intended successors of NewN have already
 252     // been created, we should hook them up as successors.  Otherwise, enqueue
 253     // the new nodes from the original graph that should have nodes created
 254     // in the new graph.
 255     for (ExplodedNode **I=N->Succs.begin(), **E=N->Succs.end(); I!=E; ++I) {
 256       Pass2Ty::iterator PI = Pass2.find(*I);
 257       if (PI != Pass2.end()) {
 258         PI->second->addPredecessor(NewN, *G);
 259         continue;
 260       }
 261
 262       // Enqueue nodes to the worklist that were marked during pass 1.
 263       if (Pass1.count(*I))
 264         WL2.push_back(*I);
 265     }
 266
 267     // Finally, explictly mark all nodes without any successors as sinks.
 268     if (N->isSink())
 269       NewN->markAsSink();
 270   }
 271
 272   return G;
 273 }
 274
 275 ExplodedNode*
 276 InterExplodedGraphMap::getMappedNode(const ExplodedNode* N) const {
 277   llvm::DenseMap<const ExplodedNode*, ExplodedNode*>::const_iterator I =
 278     M.find(N);
 279
 280   return I == M.end() ? 0 : I->second;
 281 }
 282