1//===- ExplodedGraph.h - Local, Path-Sens. "Exploded Graph" -----*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file defines the template classes ExplodedNode and ExplodedGraph,
10// which represent a path-sensitive, intra-procedural "exploded graph."
11// See "Precise interprocedural dataflow analysis via graph reachability"
12// by Reps, Horwitz, and Sagiv
13// (http://portal.acm.org/citation.cfm?id=199462) for the definition of an
14// exploded graph.
15//
16//===----------------------------------------------------------------------===//
17
18#ifndef LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_EXPLODEDGRAPH_H
19#define LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_EXPLODEDGRAPH_H
20
21#include "clang/Analysis/AnalysisDeclContext.h"
22#include "clang/Analysis/ProgramPoint.h"
23#include "clang/Analysis/Support/BumpVector.h"
24#include "clang/Basic/LLVM.h"
25#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
26#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState_Fwd.h"
27#include "clang/StaticAnalyzer/Core/PathSensitive/SVals.h"
28#include "llvm/ADT/ArrayRef.h"
29#include "llvm/ADT/DenseMap.h"
30#include "llvm/ADT/DepthFirstIterator.h"
31#include "llvm/ADT/FoldingSet.h"
32#include "llvm/ADT/GraphTraits.h"
33#include "llvm/ADT/Optional.h"
34#include "llvm/ADT/STLExtras.h"
35#include "llvm/ADT/SetVector.h"
36#include "llvm/Support/Allocator.h"
37#include "llvm/Support/Compiler.h"
38#include <cassert>
39#include <cstdint>
40#include <memory>
41#include <utility>
42#include <vector>
43
44namespace clang {
45
46class CFG;
47class Decl;
48class Expr;
49class ParentMap;
50class Stmt;
51
52namespace ento {
53
54class ExplodedGraph;
55
56//===----------------------------------------------------------------------===//
57// ExplodedGraph "implementation" classes. These classes are not typed to
58// contain a specific kind of state. Typed-specialized versions are defined
59// on top of these classes.
60//===----------------------------------------------------------------------===//
61
62// ExplodedNode is not constified all over the engine because we need to add
63// successors to it at any time after creating it.
64
65class ExplodedNode : public llvm::FoldingSetNode {
66 friend class BranchNodeBuilder;
67 friend class CoreEngine;
68 friend class EndOfFunctionNodeBuilder;
69 friend class ExplodedGraph;
70 friend class IndirectGotoNodeBuilder;
71 friend class NodeBuilder;
72 friend class SwitchNodeBuilder;
73
74 /// Efficiently stores a list of ExplodedNodes, or an optional flag.
75 ///
76 /// NodeGroup provides opaque storage for a list of ExplodedNodes, optimizing
77 /// for the case when there is only one node in the group. This is a fairly
78 /// common case in an ExplodedGraph, where most nodes have only one
79 /// predecessor and many have only one successor. It can also be used to
80 /// store a flag rather than a node list, which ExplodedNode uses to mark
81 /// whether a node is a sink. If the flag is set, the group is implicitly
82 /// empty and no nodes may be added.
83 class NodeGroup {
84 // Conceptually a discriminated union. If the low bit is set, the node is
85 // a sink. If the low bit is not set, the pointer refers to the storage
86 // for the nodes in the group.
87 // This is not a PointerIntPair in order to keep the storage type opaque.
88 uintptr_t P;
89
90 public:
91 NodeGroup(bool Flag = false) : P(Flag) {
92 assert(getFlag() == Flag);
93 }
94
95 ExplodedNode * const *begin() const;
96
97 ExplodedNode * const *end() const;
98
99 unsigned size() const;
100
101 bool empty() const { return P == 0 || getFlag() != 0; }
102
103 /// Adds a node to the list.
104 ///
105 /// The group must not have been created with its flag set.
106 void addNode(ExplodedNode *N, ExplodedGraph &G);
107
108 /// Replaces the single node in this group with a new node.
109 ///
110 /// Note that this should only be used when you know the group was not
111 /// created with its flag set, and that the group is empty or contains
112 /// only a single node.
113 void replaceNode(ExplodedNode *node);
114
115 /// Returns whether this group was created with its flag set.
116 bool getFlag() const {
117 return (P & 1);
118 }
119 };
120
121 /// Location - The program location (within a function body) associated
122 /// with this node.
123 const ProgramPoint Location;
124
125 /// State - The state associated with this node.
126 ProgramStateRef State;
127
128 /// Preds - The predecessors of this node.
129 NodeGroup Preds;
130
131 /// Succs - The successors of this node.
132 NodeGroup Succs;
133
134 int64_t Id;
135
136public:
137 explicit ExplodedNode(const ProgramPoint &loc, ProgramStateRef state,
138 int64_t Id, bool IsSink)
139 : Location(loc), State(std::move(state)), Succs(IsSink), Id(Id) {
140 assert(isSink() == IsSink);
141 }
142
143 /// getLocation - Returns the edge associated with the given node.
144 ProgramPoint getLocation() const { return Location; }
145
146 const LocationContext *getLocationContext() const {
147 return getLocation().getLocationContext();
148 }
149
150 const StackFrameContext *getStackFrame() const {
151 return getLocation().getStackFrame();
152 }
153
154 const Decl &getCodeDecl() const { return *getLocationContext()->getDecl(); }
155
156 CFG &getCFG() const { return *getLocationContext()->getCFG(); }
157
158 const CFGBlock *getCFGBlock() const;
159
160 const ParentMap &getParentMap() const {
161 return getLocationContext()->getParentMap();
162 }
163
164 template <typename T>
165 T &getAnalysis() const {
166 return *getLocationContext()->getAnalysis<T>();
167 }
168
169 const ProgramStateRef &getState() const { return State; }
170
171 template <typename T>
172 Optional<T> getLocationAs() const LLVM_LVALUE_FUNCTION {
173 return Location.getAs<T>();
174 }
175
176 /// Get the value of an arbitrary expression at this node.
177 SVal getSVal(const Stmt *S) const {
178 return getState()->getSVal(S, getLocationContext());
179 }
180
181 static void Profile(llvm::FoldingSetNodeID &ID,
182 const ProgramPoint &Loc,
183 const ProgramStateRef &state,
184 bool IsSink) {
185 ID.Add(Loc);
186 ID.AddPointer(state.get());
187 ID.AddBoolean(IsSink);
188 }
189
190 void Profile(llvm::FoldingSetNodeID& ID) const {
191 // We avoid copy constructors by not using accessors.
192 Profile(ID, Location, State, isSink());
193 }
194
195 /// addPredeccessor - Adds a predecessor to the current node, and
196 /// in tandem add this node as a successor of the other node.
197 void addPredecessor(ExplodedNode *V, ExplodedGraph &G);
198
199 unsigned succ_size() const { return Succs.size(); }
200 unsigned pred_size() const { return Preds.size(); }
201 bool succ_empty() const { return Succs.empty(); }
202 bool pred_empty() const { return Preds.empty(); }
203
204 bool isSink() const { return Succs.getFlag(); }
205
206 bool hasSinglePred() const {
207 return (pred_size() == 1);
208 }
209
210 ExplodedNode *getFirstPred() {
211 return pred_empty() ? nullptr : *(pred_begin());
212 }
213
214 const ExplodedNode *getFirstPred() const {
215 return const_cast<ExplodedNode*>(this)->getFirstPred();
216 }
217
218 ExplodedNode *getFirstSucc() {
219 return succ_empty() ? nullptr : *(succ_begin());
220 }
221
222 const ExplodedNode *getFirstSucc() const {
223 return const_cast<ExplodedNode*>(this)->getFirstSucc();
224 }
225
226 // Iterators over successor and predecessor vertices.
227 using succ_iterator = ExplodedNode * const *;
228 using succ_range = llvm::iterator_range<succ_iterator>;
229
230 using const_succ_iterator = const ExplodedNode * const *;
231 using const_succ_range = llvm::iterator_range<const_succ_iterator>;
232
233 using pred_iterator = ExplodedNode * const *;
234 using pred_range = llvm::iterator_range<pred_iterator>;
235
236 using const_pred_iterator = const ExplodedNode * const *;
237 using const_pred_range = llvm::iterator_range<const_pred_iterator>;
238
239 pred_iterator pred_begin() { return Preds.begin(); }
240 pred_iterator pred_end() { return Preds.end(); }
241 pred_range preds() { return {Preds.begin(), Preds.end()}; }
242
243 const_pred_iterator pred_begin() const {
244 return const_cast<ExplodedNode*>(this)->pred_begin();
245 }
246 const_pred_iterator pred_end() const {
247 return const_cast<ExplodedNode*>(this)->pred_end();
248 }
249 const_pred_range preds() const { return {Preds.begin(), Preds.end()}; }
250
251 succ_iterator succ_begin() { return Succs.begin(); }
252 succ_iterator succ_end() { return Succs.end(); }
253 succ_range succs() { return {Succs.begin(), Succs.end()}; }
254
255 const_succ_iterator succ_begin() const {
256 return const_cast<ExplodedNode*>(this)->succ_begin();
257 }
258 const_succ_iterator succ_end() const {
259 return const_cast<ExplodedNode*>(this)->succ_end();
260 }
261 const_succ_range succs() const { return {Succs.begin(), Succs.end()}; }
262
263 int64_t getID() const { return Id; }
264
265 /// The node is trivial if it has only one successor, only one predecessor,
266 /// it's predecessor has only one successor,
267 /// and its program state is the same as the program state of the previous
268 /// node.
269 /// Trivial nodes may be skipped while printing exploded graph.
270 bool isTrivial() const;
271
272 /// If the node's program point corresponds to a statement, retrieve that
273 /// statement. Useful for figuring out where to put a warning or a note.
274 /// If the statement belongs to a body-farmed definition,
275 /// retrieve the call site for that definition.
276 const Stmt *getStmtForDiagnostics() const;
277
278 /// Find the next statement that was executed on this node's execution path.
279 /// Useful for explaining control flow that follows the current node.
280 /// If the statement belongs to a body-farmed definition, retrieve the
281 /// call site for that definition.
282 const Stmt *getNextStmtForDiagnostics() const;
283
284 /// Find the statement that was executed immediately before this node.
285 /// Useful when the node corresponds to a CFG block entrance.
286 /// If the statement belongs to a body-farmed definition, retrieve the
287 /// call site for that definition.
288 const Stmt *getPreviousStmtForDiagnostics() const;
289
290 /// Find the statement that was executed at or immediately before this node.
291 /// Useful when any nearby statement will do.
292 /// If the statement belongs to a body-farmed definition, retrieve the
293 /// call site for that definition.
294 const Stmt *getCurrentOrPreviousStmtForDiagnostics() const;
295
296private:
297 void replaceSuccessor(ExplodedNode *node) { Succs.replaceNode(node); }
298 void replacePredecessor(ExplodedNode *node) { Preds.replaceNode(node); }
299};
300
301using InterExplodedGraphMap =
302 llvm::DenseMap<const ExplodedNode *, const ExplodedNode *>;
303
304class ExplodedGraph {
305protected:
306 friend class CoreEngine;
307
308 // Type definitions.
309 using NodeVector = std::vector<ExplodedNode *>;
310
311 /// The roots of the simulation graph. Usually there will be only
312 /// one, but clients are free to establish multiple subgraphs within a single
313 /// SimulGraph. Moreover, these subgraphs can often merge when paths from
314 /// different roots reach the same state at the same program location.
315 NodeVector Roots;
316
317 /// The nodes in the simulation graph which have been
318 /// specially marked as the endpoint of an abstract simulation path.
319 NodeVector EndNodes;
320
321 /// Nodes - The nodes in the graph.
322 llvm::FoldingSet<ExplodedNode> Nodes;
323
324 /// BVC - Allocator and context for allocating nodes and their predecessor
325 /// and successor groups.
326 BumpVectorContext BVC;
327
328 /// NumNodes - The number of nodes in the graph.
329 int64_t NumNodes = 0;
330
331 /// A list of recently allocated nodes that can potentially be recycled.
332 NodeVector ChangedNodes;
333
334 /// A list of nodes that can be reused.
335 NodeVector FreeNodes;
336
337 /// Determines how often nodes are reclaimed.
338 ///
339 /// If this is 0, nodes will never be reclaimed.
340 unsigned ReclaimNodeInterval = 0;
341
342 /// Counter to determine when to reclaim nodes.
343 unsigned ReclaimCounter;
344
345public:
346 ExplodedGraph();
347 ~ExplodedGraph();
348
349 /// Retrieve the node associated with a (Location,State) pair,
350 /// where the 'Location' is a ProgramPoint in the CFG. If no node for
351 /// this pair exists, it is created. IsNew is set to true if
352 /// the node was freshly created.
353 ExplodedNode *getNode(const ProgramPoint &L, ProgramStateRef State,
354 bool IsSink = false,
355 bool* IsNew = nullptr);
356
357 /// Create a node for a (Location, State) pair,
358 /// but don't store it for deduplication later. This
359 /// is useful when copying an already completed
360 /// ExplodedGraph for further processing.
361 ExplodedNode *createUncachedNode(const ProgramPoint &L,
362 ProgramStateRef State,
363 int64_t Id,
364 bool IsSink = false);
365
366 std::unique_ptr<ExplodedGraph> MakeEmptyGraph() const {
367 return std::make_unique<ExplodedGraph>();
368 }
369
370 /// addRoot - Add an untyped node to the set of roots.
371 ExplodedNode *addRoot(ExplodedNode *V) {
372 Roots.push_back(V);
373 return V;
374 }
375
376 /// addEndOfPath - Add an untyped node to the set of EOP nodes.
377 ExplodedNode *addEndOfPath(ExplodedNode *V) {
378 EndNodes.push_back(V);
379 return V;
380 }
381
382 unsigned num_roots() const { return Roots.size(); }
383 unsigned num_eops() const { return EndNodes.size(); }
384
385 bool empty() const { return NumNodes == 0; }
386 unsigned size() const { return NumNodes; }
387
388 void reserve(unsigned NodeCount) { Nodes.reserve(NodeCount); }
389
390 // Iterators.
391 using NodeTy = ExplodedNode;
392 using AllNodesTy = llvm::FoldingSet<ExplodedNode>;
393 using roots_iterator = NodeVector::iterator;
394 using const_roots_iterator = NodeVector::const_iterator;
395 using eop_iterator = NodeVector::iterator;
396 using const_eop_iterator = NodeVector::const_iterator;
397 using node_iterator = AllNodesTy::iterator;
398 using const_node_iterator = AllNodesTy::const_iterator;
399
400 node_iterator nodes_begin() { return Nodes.begin(); }
401
402 node_iterator nodes_end() { return Nodes.end(); }
403
404 const_node_iterator nodes_begin() const { return Nodes.begin(); }
405
406 const_node_iterator nodes_end() const { return Nodes.end(); }
407
408 roots_iterator roots_begin() { return Roots.begin(); }
409
410 roots_iterator roots_end() { return Roots.end(); }
411
412 const_roots_iterator roots_begin() const { return Roots.begin(); }
413
414 const_roots_iterator roots_end() const { return Roots.end(); }
415
416 eop_iterator eop_begin() { return EndNodes.begin(); }
417
418 eop_iterator eop_end() { return EndNodes.end(); }
419
420 const_eop_iterator eop_begin() const { return EndNodes.begin(); }
421
422 const_eop_iterator eop_end() const { return EndNodes.end(); }
423
424 llvm::BumpPtrAllocator & getAllocator() { return BVC.getAllocator(); }
425 BumpVectorContext &getNodeAllocator() { return BVC; }
426
427 using NodeMap = llvm::DenseMap<const ExplodedNode *, ExplodedNode *>;
428
429 /// Creates a trimmed version of the graph that only contains paths leading
430 /// to the given nodes.
431 ///
432 /// \param Nodes The nodes which must appear in the final graph. Presumably
433 /// these are end-of-path nodes (i.e. they have no successors).
434 /// \param[out] ForwardMap A optional map from nodes in this graph to nodes in
435 /// the returned graph.
436 /// \param[out] InverseMap An optional map from nodes in the returned graph to
437 /// nodes in this graph.
438 /// \returns The trimmed graph
439 std::unique_ptr<ExplodedGraph>
440 trim(ArrayRef<const NodeTy *> Nodes,
441 InterExplodedGraphMap *ForwardMap = nullptr,
442 InterExplodedGraphMap *InverseMap = nullptr) const;
443
444 /// Enable tracking of recently allocated nodes for potential reclamation
445 /// when calling reclaimRecentlyAllocatedNodes().
446 void enableNodeReclamation(unsigned Interval) {
447 ReclaimCounter = ReclaimNodeInterval = Interval;
448 }
449
450 /// Reclaim "uninteresting" nodes created since the last time this method
451 /// was called.
452 void reclaimRecentlyAllocatedNodes();
453
454 /// Returns true if nodes for the given expression kind are always
455 /// kept around.
456 static bool isInterestingLValueExpr(const Expr *Ex);
457
458private:
459 bool shouldCollect(const ExplodedNode *node);
460 void collectNode(ExplodedNode *node);
461};
462
463class ExplodedNodeSet {
464 using ImplTy = llvm::SmallSetVector<ExplodedNode *, 4>;
465 ImplTy Impl;
466
467public:
468 ExplodedNodeSet(ExplodedNode *N) {
469 assert(N && !static_cast<ExplodedNode*>(N)->isSink());
470 Impl.insert(N);
471 }
472
473 ExplodedNodeSet() = default;
474
475 void Add(ExplodedNode *N) {
476 if (N && !static_cast<ExplodedNode*>(N)->isSink()) Impl.insert(N);
477 }
478
479 using iterator = ImplTy::iterator;
480 using const_iterator = ImplTy::const_iterator;
481
482 unsigned size() const { return Impl.size(); }
483 bool empty() const { return Impl.empty(); }
484 bool erase(ExplodedNode *N) { return Impl.remove(N); }
485
486 void clear() { Impl.clear(); }
487
488 void insert(const ExplodedNodeSet &S) {
489 assert(&S != this);
490 if (empty())
491 Impl = S.Impl;
492 else
493 Impl.insert(S.begin(), S.end());
494 }
495
496 iterator begin() { return Impl.begin(); }
497 iterator end() { return Impl.end(); }
498
499 const_iterator begin() const { return Impl.begin(); }
500 const_iterator end() const { return Impl.end(); }
501};
502
503} // namespace ento
504
505} // namespace clang
506
507// GraphTraits
508
509namespace llvm {
510 template <> struct GraphTraits<clang::ento::ExplodedGraph *> {
511 using GraphTy = clang::ento::ExplodedGraph *;
512 using NodeRef = clang::ento::ExplodedNode *;
513 using ChildIteratorType = clang::ento::ExplodedNode::succ_iterator;
514 using nodes_iterator = llvm::df_iterator<GraphTy>;
515
516 static NodeRef getEntryNode(const GraphTy G) {
517 return *G->roots_begin();
518 }
519
520 static bool predecessorOfTrivial(NodeRef N) {
521 return N->succ_size() == 1 && N->getFirstSucc()->isTrivial();
522 }
523
524 static ChildIteratorType child_begin(NodeRef N) {
525 if (predecessorOfTrivial(N))
526 return child_begin(*N->succ_begin());
527 return N->succ_begin();
528 }
529
530 static ChildIteratorType child_end(NodeRef N) {
531 if (predecessorOfTrivial(N))
532 return child_end(N->getFirstSucc());
533 return N->succ_end();
534 }
535
536 static nodes_iterator nodes_begin(const GraphTy G) {
537 return df_begin(G);
538 }
539
540 static nodes_iterator nodes_end(const GraphTy G) {
541 return df_end(G);
542 }
543 };
544} // namespace llvm
545
546#endif // LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_EXPLODEDGRAPH_H
547