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
134public:
135 explicit ExplodedNode(const ProgramPoint &loc, ProgramStateRef state,
136 bool IsSink)
137 : Location(loc), State(std::move(state)), Succs(IsSink) {
138 assert(isSink() == IsSink);
139 }
140
141 /// getLocation - Returns the edge associated with the given node.
142 ProgramPoint getLocation() const { return Location; }
143
144 const LocationContext *getLocationContext() const {
145 return getLocation().getLocationContext();
146 }
147
148 const StackFrameContext *getStackFrame() const {
149 return getLocation().getStackFrame();
150 }
151
152 const Decl &getCodeDecl() const { return *getLocationContext()->getDecl(); }
153
154 CFG &getCFG() const { return *getLocationContext()->getCFG(); }
155
156 ParentMap &getParentMap() const {return getLocationContext()->getParentMap();}
157
158 template <typename T>
159 T &getAnalysis() const {
160 return *getLocationContext()->getAnalysis<T>();
161 }
162
163 const ProgramStateRef &getState() const { return State; }
164
165 template <typename T>
166 Optional<T> getLocationAs() const LLVM_LVALUE_FUNCTION {
167 return Location.getAs<T>();
168 }
169
170 /// Get the value of an arbitrary expression at this node.
171 SVal getSVal(const Stmt *S) const {
172 return getState()->getSVal(S, getLocationContext());
173 }
174
175 static void Profile(llvm::FoldingSetNodeID &ID,
176 const ProgramPoint &Loc,
177 const ProgramStateRef &state,
178 bool IsSink) {
179 ID.Add(Loc);
180 ID.AddPointer(state.get());
181 ID.AddBoolean(IsSink);
182 }
183
184 void Profile(llvm::FoldingSetNodeID& ID) const {
185 // We avoid copy constructors by not using accessors.
186 Profile(ID, Location, State, isSink());
187 }
188
189 /// addPredeccessor - Adds a predecessor to the current node, and
190 /// in tandem add this node as a successor of the other node.
191 void addPredecessor(ExplodedNode *V, ExplodedGraph &G);
192
193 unsigned succ_size() const { return Succs.size(); }
194 unsigned pred_size() const { return Preds.size(); }
195 bool succ_empty() const { return Succs.empty(); }
196 bool pred_empty() const { return Preds.empty(); }
197
198 bool isSink() const { return Succs.getFlag(); }
199
200 bool hasSinglePred() const {
201 return (pred_size() == 1);
202 }
203
204 ExplodedNode *getFirstPred() {
205 return pred_empty() ? nullptr : *(pred_begin());
206 }
207
208 const ExplodedNode *getFirstPred() const {
209 return const_cast<ExplodedNode*>(this)->getFirstPred();
210 }
211
212 ExplodedNode *getFirstSucc() {
213 return succ_empty() ? nullptr : *(succ_begin());
214 }
215
216 const ExplodedNode *getFirstSucc() const {
217 return const_cast<ExplodedNode*>(this)->getFirstSucc();
218 }
219
220 // Iterators over successor and predecessor vertices.
221 using succ_iterator = ExplodedNode * const *;
222 using const_succ_iterator = const ExplodedNode * const *;
223 using pred_iterator = ExplodedNode * const *;
224 using const_pred_iterator = const ExplodedNode * const *;
225
226 pred_iterator pred_begin() { return Preds.begin(); }
227 pred_iterator pred_end() { return Preds.end(); }
228
229 const_pred_iterator pred_begin() const {
230 return const_cast<ExplodedNode*>(this)->pred_begin();
231 }
232 const_pred_iterator pred_end() const {
233 return const_cast<ExplodedNode*>(this)->pred_end();
234 }
235
236 succ_iterator succ_begin() { return Succs.begin(); }
237 succ_iterator succ_end() { return Succs.end(); }
238
239 const_succ_iterator succ_begin() const {
240 return const_cast<ExplodedNode*>(this)->succ_begin();
241 }
242 const_succ_iterator succ_end() const {
243 return const_cast<ExplodedNode*>(this)->succ_end();
244 }
245
246 int64_t getID(ExplodedGraph *G) const;
247
248 /// The node is trivial if it has only one successor, only one predecessor,
249 /// it's predecessor has only one successor,
250 /// and its program state is the same as the program state of the previous
251 /// node.
252 /// Trivial nodes may be skipped while printing exploded graph.
253 bool isTrivial() const;
254
255private:
256 void replaceSuccessor(ExplodedNode *node) { Succs.replaceNode(node); }
257 void replacePredecessor(ExplodedNode *node) { Preds.replaceNode(node); }
258};
259
260using InterExplodedGraphMap =
261 llvm::DenseMap<const ExplodedNode *, const ExplodedNode *>;
262
263class ExplodedGraph {
264protected:
265 friend class CoreEngine;
266
267 // Type definitions.
268 using NodeVector = std::vector<ExplodedNode *>;
269
270 /// The roots of the simulation graph. Usually there will be only
271 /// one, but clients are free to establish multiple subgraphs within a single
272 /// SimulGraph. Moreover, these subgraphs can often merge when paths from
273 /// different roots reach the same state at the same program location.
274 NodeVector Roots;
275
276 /// The nodes in the simulation graph which have been
277 /// specially marked as the endpoint of an abstract simulation path.
278 NodeVector EndNodes;
279
280 /// Nodes - The nodes in the graph.
281 llvm::FoldingSet<ExplodedNode> Nodes;
282
283 /// BVC - Allocator and context for allocating nodes and their predecessor
284 /// and successor groups.
285 BumpVectorContext BVC;
286
287 /// NumNodes - The number of nodes in the graph.
288 unsigned NumNodes = 0;
289
290 /// A list of recently allocated nodes that can potentially be recycled.
291 NodeVector ChangedNodes;
292
293 /// A list of nodes that can be reused.
294 NodeVector FreeNodes;
295
296 /// Determines how often nodes are reclaimed.
297 ///
298 /// If this is 0, nodes will never be reclaimed.
299 unsigned ReclaimNodeInterval = 0;
300
301 /// Counter to determine when to reclaim nodes.
302 unsigned ReclaimCounter;
303
304public:
305 ExplodedGraph();
306 ~ExplodedGraph();
307
308 /// Retrieve the node associated with a (Location,State) pair,
309 /// where the 'Location' is a ProgramPoint in the CFG. If no node for
310 /// this pair exists, it is created. IsNew is set to true if
311 /// the node was freshly created.
312 ExplodedNode *getNode(const ProgramPoint &L, ProgramStateRef State,
313 bool IsSink = false,
314 bool* IsNew = nullptr);
315
316 /// Create a node for a (Location, State) pair,
317 /// but don't store it for deduplication later. This
318 /// is useful when copying an already completed
319 /// ExplodedGraph for further processing.
320 ExplodedNode *createUncachedNode(const ProgramPoint &L,
321 ProgramStateRef State,
322 bool IsSink = false);
323
324 std::unique_ptr<ExplodedGraph> MakeEmptyGraph() const {
325 return llvm::make_unique<ExplodedGraph>();
326 }
327
328 /// addRoot - Add an untyped node to the set of roots.
329 ExplodedNode *addRoot(ExplodedNode *V) {
330 Roots.push_back(V);
331 return V;
332 }
333
334 /// addEndOfPath - Add an untyped node to the set of EOP nodes.
335 ExplodedNode *addEndOfPath(ExplodedNode *V) {
336 EndNodes.push_back(V);
337 return V;
338 }
339
340 unsigned num_roots() const { return Roots.size(); }
341 unsigned num_eops() const { return EndNodes.size(); }
342
343 bool empty() const { return NumNodes == 0; }
344 unsigned size() const { return NumNodes; }
345
346 void reserve(unsigned NodeCount) { Nodes.reserve(NodeCount); }
347
348 // Iterators.
349 using NodeTy = ExplodedNode;
350 using AllNodesTy = llvm::FoldingSet<ExplodedNode>;
351 using roots_iterator = NodeVector::iterator;
352 using const_roots_iterator = NodeVector::const_iterator;
353 using eop_iterator = NodeVector::iterator;
354 using const_eop_iterator = NodeVector::const_iterator;
355 using node_iterator = AllNodesTy::iterator;
356 using const_node_iterator = AllNodesTy::const_iterator;
357
358 node_iterator nodes_begin() { return Nodes.begin(); }
359
360 node_iterator nodes_end() { return Nodes.end(); }
361
362 const_node_iterator nodes_begin() const { return Nodes.begin(); }
363
364 const_node_iterator nodes_end() const { return Nodes.end(); }
365
366 roots_iterator roots_begin() { return Roots.begin(); }
367
368 roots_iterator roots_end() { return Roots.end(); }
369
370 const_roots_iterator roots_begin() const { return Roots.begin(); }
371
372 const_roots_iterator roots_end() const { return Roots.end(); }
373
374 eop_iterator eop_begin() { return EndNodes.begin(); }
375
376 eop_iterator eop_end() { return EndNodes.end(); }
377
378 const_eop_iterator eop_begin() const { return EndNodes.begin(); }
379
380 const_eop_iterator eop_end() const { return EndNodes.end(); }
381
382 llvm::BumpPtrAllocator & getAllocator() { return BVC.getAllocator(); }
383 BumpVectorContext &getNodeAllocator() { return BVC; }
384
385 using NodeMap = llvm::DenseMap<const ExplodedNode *, ExplodedNode *>;
386
387 /// Creates a trimmed version of the graph that only contains paths leading
388 /// to the given nodes.
389 ///
390 /// \param Nodes The nodes which must appear in the final graph. Presumably
391 /// these are end-of-path nodes (i.e. they have no successors).
392 /// \param[out] ForwardMap A optional map from nodes in this graph to nodes in
393 /// the returned graph.
394 /// \param[out] InverseMap An optional map from nodes in the returned graph to
395 /// nodes in this graph.
396 /// \returns The trimmed graph
397 std::unique_ptr<ExplodedGraph>
398 trim(ArrayRef<const NodeTy *> Nodes,
399 InterExplodedGraphMap *ForwardMap = nullptr,
400 InterExplodedGraphMap *InverseMap = nullptr) const;
401
402 /// Enable tracking of recently allocated nodes for potential reclamation
403 /// when calling reclaimRecentlyAllocatedNodes().
404 void enableNodeReclamation(unsigned Interval) {
405 ReclaimCounter = ReclaimNodeInterval = Interval;
406 }
407
408 /// Reclaim "uninteresting" nodes created since the last time this method
409 /// was called.
410 void reclaimRecentlyAllocatedNodes();
411
412 /// Returns true if nodes for the given expression kind are always
413 /// kept around.
414 static bool isInterestingLValueExpr(const Expr *Ex);
415
416private:
417 bool shouldCollect(const ExplodedNode *node);
418 void collectNode(ExplodedNode *node);
419};
420
421class ExplodedNodeSet {
422 using ImplTy = llvm::SmallSetVector<ExplodedNode *, 4>;
423 ImplTy Impl;
424
425public:
426 ExplodedNodeSet(ExplodedNode *N) {
427 assert(N && !static_cast<ExplodedNode*>(N)->isSink());
428 Impl.insert(N);
429 }
430
431 ExplodedNodeSet() = default;
432
433 void Add(ExplodedNode *N) {
434 if (N && !static_cast<ExplodedNode*>(N)->isSink()) Impl.insert(N);
435 }
436
437 using iterator = ImplTy::iterator;
438 using const_iterator = ImplTy::const_iterator;
439
440 unsigned size() const { return Impl.size(); }
441 bool empty() const { return Impl.empty(); }
442 bool erase(ExplodedNode *N) { return Impl.remove(N); }
443
444 void clear() { Impl.clear(); }
445
446 void insert(const ExplodedNodeSet &S) {
447 assert(&S != this);
448 if (empty())
449 Impl = S.Impl;
450 else
451 Impl.insert(S.begin(), S.end());
452 }
453
454 iterator begin() { return Impl.begin(); }
455 iterator end() { return Impl.end(); }
456
457 const_iterator begin() const { return Impl.begin(); }
458 const_iterator end() const { return Impl.end(); }
459};
460
461} // namespace ento
462
463} // namespace clang
464
465// GraphTraits
466
467namespace llvm {
468 template <> struct GraphTraits<clang::ento::ExplodedGraph *> {
469 using GraphTy = clang::ento::ExplodedGraph *;
470 using NodeRef = clang::ento::ExplodedNode *;
471 using ChildIteratorType = clang::ento::ExplodedNode::succ_iterator;
472 using nodes_iterator = llvm::df_iterator<GraphTy>;
473
474 static NodeRef getEntryNode(const GraphTy G) {
475 return *G->roots_begin();
476 }
477
478 static bool predecessorOfTrivial(NodeRef N) {
479 return N->succ_size() == 1 && N->getFirstSucc()->isTrivial();
480 }
481
482 static ChildIteratorType child_begin(NodeRef N) {
483 if (predecessorOfTrivial(N))
484 return child_begin(*N->succ_begin());
485 return N->succ_begin();
486 }
487
488 static ChildIteratorType child_end(NodeRef N) {
489 if (predecessorOfTrivial(N))
490 return child_end(N->getFirstSucc());
491 return N->succ_end();
492 }
493
494 static nodes_iterator nodes_begin(const GraphTy G) {
495 return df_begin(G);
496 }
497
498 static nodes_iterator nodes_end(const GraphTy G) {
499 return df_end(G);
500 }
501 };
502} // namespace llvm
503
504#endif // LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_EXPLODEDGRAPH_H
505