1 //=-- ExplodedGraph.cpp - Local, Path-Sens. "Exploded Graph" -*- C++ -*------=//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the template classes ExplodedNode and ExplodedGraph,
11 // which represent a path-sensitive, intra-procedural "exploded graph."
13 //===----------------------------------------------------------------------===//
15 #include "clang/StaticAnalyzer/Core/PathSensitive/ExplodedGraph.h"
16 #include "clang/AST/ParentMap.h"
17 #include "clang/AST/Stmt.h"
18 #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
19 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
20 #include "llvm/ADT/DenseMap.h"
21 #include "llvm/ADT/DenseSet.h"
22 #include "llvm/ADT/SmallVector.h"
23 #include "llvm/ADT/Statistic.h"
26 using namespace clang;
29 //===----------------------------------------------------------------------===//
31 //===----------------------------------------------------------------------===//
33 // An out of line virtual method to provide a home for the class vtable.
34 ExplodedNode::Auditor::~Auditor() {}
37 static ExplodedNode::Auditor* NodeAuditor = 0;
40 void ExplodedNode::SetAuditor(ExplodedNode::Auditor* A) {
46 //===----------------------------------------------------------------------===//
48 //===----------------------------------------------------------------------===//
50 ExplodedGraph::ExplodedGraph()
51 : NumNodes(0), ReclaimNodeInterval(0) {}
53 ExplodedGraph::~ExplodedGraph() {}
55 //===----------------------------------------------------------------------===//
57 //===----------------------------------------------------------------------===//
59 bool ExplodedGraph::isInterestingLValueExpr(const Expr *Ex) {
62 return isa<DeclRefExpr>(Ex) ||
63 isa<MemberExpr>(Ex) ||
64 isa<ObjCIvarRefExpr>(Ex);
67 bool ExplodedGraph::shouldCollect(const ExplodedNode *node) {
68 // First, we only consider nodes for reclamation of the following
71 // (1) 1 predecessor (that has one successor)
72 // (2) 1 successor (that has one predecessor)
74 // If a node has no successor it is on the "frontier", while a node
75 // with no predecessor is a root.
77 // After these prerequisites, we discard all "filler" nodes that
78 // are used only for intermediate processing, and are not essential
79 // for analyzer history:
81 // (a) PreStmtPurgeDeadSymbols
83 // We then discard all other nodes where *all* of the following conditions
86 // (3) The ProgramPoint is for a PostStmt, but not a PostStore.
87 // (4) There is no 'tag' for the ProgramPoint.
88 // (5) The 'store' is the same as the predecessor.
89 // (6) The 'GDM' is the same as the predecessor.
90 // (7) The LocationContext is the same as the predecessor.
91 // (8) Expressions that are *not* lvalue expressions.
92 // (9) The PostStmt isn't for a non-consumed Stmt or Expr.
93 // (10) The successor is not a CallExpr StmtPoint (so that we would
94 // be able to find it when retrying a call with no inlining).
95 // FIXME: It may be safe to reclaim PreCall and PostCall nodes as well.
97 // Conditions 1 and 2.
98 if (node->pred_size() != 1 || node->succ_size() != 1)
101 const ExplodedNode *pred = *(node->pred_begin());
102 if (pred->succ_size() != 1)
105 const ExplodedNode *succ = *(node->succ_begin());
106 if (succ->pred_size() != 1)
109 // Now reclaim any nodes that are (by definition) not essential to
110 // analysis history and are not consulted by any client code.
111 ProgramPoint progPoint = node->getLocation();
112 if (progPoint.getAs<PreStmtPurgeDeadSymbols>())
113 return !progPoint.getTag();
116 if (!progPoint.getAs<PostStmt>() || progPoint.getAs<PostStore>())
120 if (progPoint.getTag())
123 // Conditions 5, 6, and 7.
124 ProgramStateRef state = node->getState();
125 ProgramStateRef pred_state = pred->getState();
126 if (state->store != pred_state->store || state->GDM != pred_state->GDM ||
127 progPoint.getLocationContext() != pred->getLocationContext())
130 // All further checks require expressions. As per #3, we know that we have
132 const Expr *Ex = dyn_cast<Expr>(progPoint.castAs<PostStmt>().getStmt());
137 // Do not collect nodes for "interesting" lvalue expressions since they are
138 // used extensively for generating path diagnostics.
139 if (isInterestingLValueExpr(Ex))
143 // Do not collect nodes for non-consumed Stmt or Expr to ensure precise
144 // diagnostic generation; specifically, so that we could anchor arrows
145 // pointing to the beginning of statements (as written in code).
146 ParentMap &PM = progPoint.getLocationContext()->getParentMap();
147 if (!PM.isConsumedExpr(Ex))
151 const ProgramPoint SuccLoc = succ->getLocation();
152 if (Optional<StmtPoint> SP = SuccLoc.getAs<StmtPoint>())
153 if (CallEvent::isCallStmt(SP->getStmt()))
159 void ExplodedGraph::collectNode(ExplodedNode *node) {
160 // Removing a node means:
161 // (a) changing the predecessors successor to the successor of this node
162 // (b) changing the successors predecessor to the predecessor of this node
163 // (c) Putting 'node' onto freeNodes.
164 assert(node->pred_size() == 1 || node->succ_size() == 1);
165 ExplodedNode *pred = *(node->pred_begin());
166 ExplodedNode *succ = *(node->succ_begin());
167 pred->replaceSuccessor(succ);
168 succ->replacePredecessor(pred);
169 FreeNodes.push_back(node);
170 Nodes.RemoveNode(node);
172 node->~ExplodedNode();
175 void ExplodedGraph::reclaimRecentlyAllocatedNodes() {
176 if (ChangedNodes.empty())
179 // Only periodically reclaim nodes so that we can build up a set of
180 // nodes that meet the reclamation criteria. Freshly created nodes
181 // by definition have no successor, and thus cannot be reclaimed (see below).
182 assert(ReclaimCounter > 0);
183 if (--ReclaimCounter != 0)
185 ReclaimCounter = ReclaimNodeInterval;
187 for (NodeVector::iterator it = ChangedNodes.begin(), et = ChangedNodes.end();
189 ExplodedNode *node = *it;
190 if (shouldCollect(node))
193 ChangedNodes.clear();
196 //===----------------------------------------------------------------------===//
198 //===----------------------------------------------------------------------===//
200 // An NodeGroup's storage type is actually very much like a TinyPtrVector:
201 // it can be either a pointer to a single ExplodedNode, or a pointer to a
202 // BumpVector allocated with the ExplodedGraph's allocator. This allows the
203 // common case of single-node NodeGroups to be implemented with no extra memory.
205 // Consequently, each of the NodeGroup methods have up to four cases to handle:
206 // 1. The flag is set and this group does not actually contain any nodes.
207 // 2. The group is empty, in which case the storage value is null.
208 // 3. The group contains a single node.
209 // 4. The group contains more than one node.
210 typedef BumpVector<ExplodedNode *> ExplodedNodeVector;
211 typedef llvm::PointerUnion<ExplodedNode *, ExplodedNodeVector *> GroupStorage;
213 void ExplodedNode::addPredecessor(ExplodedNode *V, ExplodedGraph &G) {
214 assert (!V->isSink());
216 V->Succs.addNode(this, G);
218 if (NodeAuditor) NodeAuditor->AddEdge(V, this);
222 void ExplodedNode::NodeGroup::replaceNode(ExplodedNode *node) {
225 GroupStorage &Storage = reinterpret_cast<GroupStorage&>(P);
226 assert(Storage.is<ExplodedNode *>());
228 assert(Storage.is<ExplodedNode *>());
231 void ExplodedNode::NodeGroup::addNode(ExplodedNode *N, ExplodedGraph &G) {
234 GroupStorage &Storage = reinterpret_cast<GroupStorage&>(P);
235 if (Storage.isNull()) {
237 assert(Storage.is<ExplodedNode *>());
241 ExplodedNodeVector *V = Storage.dyn_cast<ExplodedNodeVector *>();
244 // Switch from single-node to multi-node representation.
245 ExplodedNode *Old = Storage.get<ExplodedNode *>();
247 BumpVectorContext &Ctx = G.getNodeAllocator();
248 V = G.getAllocator().Allocate<ExplodedNodeVector>();
249 new (V) ExplodedNodeVector(Ctx, 4);
250 V->push_back(Old, Ctx);
254 assert(Storage.is<ExplodedNodeVector *>());
257 V->push_back(N, G.getNodeAllocator());
260 unsigned ExplodedNode::NodeGroup::size() const {
264 const GroupStorage &Storage = reinterpret_cast<const GroupStorage &>(P);
265 if (Storage.isNull())
267 if (ExplodedNodeVector *V = Storage.dyn_cast<ExplodedNodeVector *>())
272 ExplodedNode * const *ExplodedNode::NodeGroup::begin() const {
276 const GroupStorage &Storage = reinterpret_cast<const GroupStorage &>(P);
277 if (Storage.isNull())
279 if (ExplodedNodeVector *V = Storage.dyn_cast<ExplodedNodeVector *>())
281 return Storage.getAddrOfPtr1();
284 ExplodedNode * const *ExplodedNode::NodeGroup::end() const {
288 const GroupStorage &Storage = reinterpret_cast<const GroupStorage &>(P);
289 if (Storage.isNull())
291 if (ExplodedNodeVector *V = Storage.dyn_cast<ExplodedNodeVector *>())
293 return Storage.getAddrOfPtr1() + 1;
296 ExplodedNode *ExplodedGraph::getNode(const ProgramPoint &L,
297 ProgramStateRef State,
300 // Profile 'State' to determine if we already have an existing node.
301 llvm::FoldingSetNodeID profile;
304 NodeTy::Profile(profile, L, State, IsSink);
305 NodeTy* V = Nodes.FindNodeOrInsertPos(profile, InsertPos);
308 if (!FreeNodes.empty()) {
309 V = FreeNodes.back();
310 FreeNodes.pop_back();
313 // Allocate a new node.
314 V = (NodeTy*) getAllocator().Allocate<NodeTy>();
317 new (V) NodeTy(L, State, IsSink);
319 if (ReclaimNodeInterval)
320 ChangedNodes.push_back(V);
322 // Insert the node into the node set and return it.
323 Nodes.InsertNode(V, InsertPos);
326 if (IsNew) *IsNew = true;
329 if (IsNew) *IsNew = false;
335 ExplodedGraph::trim(ArrayRef<const NodeTy *> Sinks,
336 InterExplodedGraphMap *ForwardMap,
337 InterExplodedGraphMap *InverseMap) const{
342 typedef llvm::DenseSet<const ExplodedNode*> Pass1Ty;
345 typedef InterExplodedGraphMap Pass2Ty;
346 InterExplodedGraphMap Pass2Scratch;
347 Pass2Ty &Pass2 = ForwardMap ? *ForwardMap : Pass2Scratch;
349 SmallVector<const ExplodedNode*, 10> WL1, WL2;
351 // ===- Pass 1 (reverse DFS) -===
352 for (ArrayRef<const NodeTy *>::iterator I = Sinks.begin(), E = Sinks.end();
358 // Process the first worklist until it is empty.
359 while (!WL1.empty()) {
360 const ExplodedNode *N = WL1.pop_back_val();
362 // Have we already visited this node? If so, continue to the next one.
366 // Otherwise, mark this node as visited.
369 // If this is a root enqueue it to the second worklist.
370 if (N->Preds.empty()) {
375 // Visit our predecessors and enqueue them.
376 for (ExplodedNode::pred_iterator I = N->Preds.begin(), E = N->Preds.end();
381 // We didn't hit a root? Return with a null pointer for the new graph.
385 // Create an empty graph.
386 ExplodedGraph* G = MakeEmptyGraph();
388 // ===- Pass 2 (forward DFS to construct the new graph) -===
389 while (!WL2.empty()) {
390 const ExplodedNode *N = WL2.pop_back_val();
392 // Skip this node if we have already processed it.
393 if (Pass2.find(N) != Pass2.end())
396 // Create the corresponding node in the new graph and record the mapping
397 // from the old node to the new node.
398 ExplodedNode *NewN = G->getNode(N->getLocation(), N->State, N->isSink(), 0);
401 // Also record the reverse mapping from the new node to the old node.
402 if (InverseMap) (*InverseMap)[NewN] = N;
404 // If this node is a root, designate it as such in the graph.
405 if (N->Preds.empty())
408 // In the case that some of the intended predecessors of NewN have already
409 // been created, we should hook them up as predecessors.
411 // Walk through the predecessors of 'N' and hook up their corresponding
412 // nodes in the new graph (if any) to the freshly created node.
413 for (ExplodedNode::pred_iterator I = N->Preds.begin(), E = N->Preds.end();
415 Pass2Ty::iterator PI = Pass2.find(*I);
416 if (PI == Pass2.end())
419 NewN->addPredecessor(const_cast<ExplodedNode *>(PI->second), *G);
422 // In the case that some of the intended successors of NewN have already
423 // been created, we should hook them up as successors. Otherwise, enqueue
424 // the new nodes from the original graph that should have nodes created
426 for (ExplodedNode::succ_iterator I = N->Succs.begin(), E = N->Succs.end();
428 Pass2Ty::iterator PI = Pass2.find(*I);
429 if (PI != Pass2.end()) {
430 const_cast<ExplodedNode *>(PI->second)->addPredecessor(NewN, *G);
434 // Enqueue nodes to the worklist that were marked during pass 1.