1//===-- DataflowAnalysisContext.cpp -----------------------------*- 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 a DataflowAnalysisContext class that owns objects that
10// encompass the state of a program and stores context that is used during
11// dataflow analysis.
12//
13//===----------------------------------------------------------------------===//
14
15#include "clang/Analysis/FlowSensitive/DataflowAnalysisContext.h"
16#include "clang/Analysis/FlowSensitive/ASTOps.h"
17#include "clang/Analysis/FlowSensitive/Formula.h"
18#include "clang/Analysis/FlowSensitive/Logger.h"
19#include "clang/Analysis/FlowSensitive/SimplifyConstraints.h"
20#include "clang/Analysis/FlowSensitive/Value.h"
21#include "llvm/ADT/SetOperations.h"
22#include "llvm/ADT/SetVector.h"
23#include "llvm/Support/CommandLine.h"
24#include "llvm/Support/Debug.h"
25#include "llvm/Support/FileSystem.h"
26#include "llvm/Support/Path.h"
27#include "llvm/Support/raw_ostream.h"
28#include <cassert>
29#include <memory>
30#include <string>
31#include <utility>
32#include <vector>
33
34static llvm::cl::opt<std::string> DataflowLog(
35 "dataflow-log", llvm::cl::Hidden, llvm::cl::ValueOptional,
36 llvm::cl::desc("Emit log of dataflow analysis. With no arg, writes textual "
37 "log to stderr. With an arg, writes HTML logs under the "
38 "specified directory (one per analyzed function)."));
39
40namespace clang {
41namespace dataflow {
42
43FieldSet DataflowAnalysisContext::getModeledFields(QualType Type) {
44 // During context-sensitive analysis, a struct may be allocated in one
45 // function, but its field accessed in a function lower in the stack than
46 // the allocation. Since we only collect fields used in the function where
47 // the allocation occurs, we can't apply that filter when performing
48 // context-sensitive analysis. But, this only applies to storage locations,
49 // since field access it not allowed to fail. In contrast, field *values*
50 // don't need this allowance, since the API allows for uninitialized fields.
51 if (Opts.ContextSensitiveOpts)
52 return getObjectFields(Type);
53
54 return llvm::set_intersection(S1: getObjectFields(Type), S2: ModeledFields);
55}
56
57void DataflowAnalysisContext::addModeledFields(const FieldSet &Fields) {
58 ModeledFields.set_union(Fields);
59}
60
61StorageLocation &DataflowAnalysisContext::createStorageLocation(QualType Type) {
62 if (!Type.isNull() && Type->isRecordType()) {
63 llvm::DenseMap<const ValueDecl *, StorageLocation *> FieldLocs;
64 for (const FieldDecl *Field : getModeledFields(Type))
65 if (Field->getType()->isReferenceType())
66 FieldLocs.insert(KV: {Field, nullptr});
67 else
68 FieldLocs.insert(KV: {Field, &createStorageLocation(
69 Type: Field->getType().getNonReferenceType())});
70
71 RecordStorageLocation::SyntheticFieldMap SyntheticFields;
72 for (const auto &Entry : getSyntheticFields(Type))
73 SyntheticFields.insert(
74 KV: {Entry.getKey(),
75 &createStorageLocation(Type: Entry.getValue().getNonReferenceType())});
76
77 return createRecordStorageLocation(Type, FieldLocs: std::move(FieldLocs),
78 SyntheticFields: std::move(SyntheticFields));
79 }
80 return arena().create<ScalarStorageLocation>(args&: Type);
81}
82
83// Returns the keys for a given `StringMap`.
84// Can't use `StringSet` as the return type as it doesn't support `operator==`.
85template <typename T>
86static llvm::DenseSet<llvm::StringRef> getKeys(const llvm::StringMap<T> &Map) {
87 return llvm::DenseSet<llvm::StringRef>(llvm::from_range, Map.keys());
88}
89
90RecordStorageLocation &DataflowAnalysisContext::createRecordStorageLocation(
91 QualType Type, RecordStorageLocation::FieldToLoc FieldLocs,
92 RecordStorageLocation::SyntheticFieldMap SyntheticFields) {
93 assert(Type->isRecordType());
94 assert(containsSameFields(getModeledFields(Type), FieldLocs));
95 assert(getKeys(getSyntheticFields(Type)) == getKeys(SyntheticFields));
96
97 RecordStorageLocationCreated = true;
98 return arena().create<RecordStorageLocation>(args&: Type, args: std::move(FieldLocs),
99 args: std::move(SyntheticFields));
100}
101
102StorageLocation &
103DataflowAnalysisContext::getStableStorageLocation(const ValueDecl &D) {
104 if (auto *Loc = DeclToLoc.lookup(Val: &D))
105 return *Loc;
106 auto &Loc = createStorageLocation(Type: D.getType().getNonReferenceType());
107 DeclToLoc[&D] = &Loc;
108 return Loc;
109}
110
111StorageLocation &
112DataflowAnalysisContext::getStableStorageLocation(const Expr &E) {
113 const Expr &CanonE = ignoreCFGOmittedNodes(E);
114
115 if (auto *Loc = ExprToLoc.lookup(Val: &CanonE))
116 return *Loc;
117 auto &Loc = createStorageLocation(Type: CanonE.getType());
118 ExprToLoc[&CanonE] = &Loc;
119 return Loc;
120}
121
122PointerValue &
123DataflowAnalysisContext::getOrCreateNullPointerValue(QualType PointeeType) {
124 auto CanonicalPointeeType =
125 PointeeType.isNull() ? PointeeType : PointeeType.getCanonicalType();
126 auto Res = NullPointerVals.try_emplace(Key: CanonicalPointeeType, Args: nullptr);
127 if (Res.second) {
128 auto &PointeeLoc = createStorageLocation(Type: CanonicalPointeeType);
129 Res.first->second = &arena().create<PointerValue>(args&: PointeeLoc);
130 }
131 return *Res.first->second;
132}
133
134void DataflowAnalysisContext::addInvariant(const Formula &Constraint) {
135 if (Invariant == nullptr)
136 Invariant = &Constraint;
137 else
138 Invariant = &arena().makeAnd(LHS: *Invariant, RHS: Constraint);
139}
140
141void DataflowAnalysisContext::addFlowConditionConstraint(
142 Atom Token, const Formula &Constraint) {
143 auto Res = FlowConditionConstraints.try_emplace(Key: Token, Args: &Constraint);
144 if (!Res.second) {
145 Res.first->second =
146 &arena().makeAnd(LHS: *Res.first->second, RHS: Constraint);
147 }
148}
149
150Atom DataflowAnalysisContext::forkFlowCondition(Atom Token) {
151 Atom ForkToken = arena().makeFlowConditionToken();
152 FlowConditionDeps[ForkToken].insert(V: Token);
153 addFlowConditionConstraint(Token: ForkToken, Constraint: arena().makeAtomRef(A: Token));
154 return ForkToken;
155}
156
157Atom
158DataflowAnalysisContext::joinFlowConditions(Atom FirstToken,
159 Atom SecondToken) {
160 Atom Token = arena().makeFlowConditionToken();
161 auto &TokenDeps = FlowConditionDeps[Token];
162 TokenDeps.insert(V: FirstToken);
163 TokenDeps.insert(V: SecondToken);
164 addFlowConditionConstraint(Token,
165 Constraint: arena().makeOr(LHS: arena().makeAtomRef(A: FirstToken),
166 RHS: arena().makeAtomRef(A: SecondToken)));
167 return Token;
168}
169
170Solver::Result DataflowAnalysisContext::querySolver(
171 llvm::SetVector<const Formula *> Constraints) {
172 return S.solve(Vals: Constraints.getArrayRef());
173}
174
175bool DataflowAnalysisContext::flowConditionImplies(Atom Token,
176 const Formula &F) {
177 if (F.isLiteral(b: true))
178 return true;
179
180 // Returns true if and only if truth assignment of the flow condition implies
181 // that `F` is also true. We prove whether or not this property holds by
182 // reducing the problem to satisfiability checking. In other words, we attempt
183 // to show that assuming `F` is false makes the constraints induced by the
184 // flow condition unsatisfiable.
185 llvm::SetVector<const Formula *> Constraints;
186 Constraints.insert(X: &arena().makeAtomRef(A: Token));
187 Constraints.insert(X: &arena().makeNot(Val: F));
188 addTransitiveFlowConditionConstraints(Token, Out&: Constraints);
189 return isUnsatisfiable(Constraints: std::move(Constraints));
190}
191
192bool DataflowAnalysisContext::flowConditionAllows(Atom Token,
193 const Formula &F) {
194 if (F.isLiteral(b: false))
195 return false;
196
197 llvm::SetVector<const Formula *> Constraints;
198 Constraints.insert(X: &arena().makeAtomRef(A: Token));
199 Constraints.insert(X: &F);
200 addTransitiveFlowConditionConstraints(Token, Out&: Constraints);
201 return isSatisfiable(Constraints: std::move(Constraints));
202}
203
204bool DataflowAnalysisContext::equivalentFormulas(const Formula &Val1,
205 const Formula &Val2) {
206 llvm::SetVector<const Formula *> Constraints;
207 Constraints.insert(X: &arena().makeNot(Val: arena().makeEquals(LHS: Val1, RHS: Val2)));
208 return isUnsatisfiable(Constraints: std::move(Constraints));
209}
210
211void DataflowAnalysisContext::addTransitiveFlowConditionConstraints(
212 Atom Token, llvm::SetVector<const Formula *> &Constraints) {
213 llvm::DenseSet<Atom> AddedTokens;
214 std::vector<Atom> Remaining = {Token};
215
216 if (Invariant)
217 Constraints.insert(X: Invariant);
218 // Define all the flow conditions that might be referenced in constraints.
219 while (!Remaining.empty()) {
220 auto Token = Remaining.back();
221 Remaining.pop_back();
222 if (!AddedTokens.insert(V: Token).second)
223 continue;
224
225 auto ConstraintsIt = FlowConditionConstraints.find(Val: Token);
226 if (ConstraintsIt == FlowConditionConstraints.end()) {
227 Constraints.insert(X: &arena().makeAtomRef(A: Token));
228 } else {
229 // Bind flow condition token via `iff` to its set of constraints:
230 // FC <=> (C1 ^ C2 ^ ...), where Ci are constraints
231 Constraints.insert(X: &arena().makeEquals(LHS: arena().makeAtomRef(A: Token),
232 RHS: *ConstraintsIt->second));
233 }
234
235 if (auto DepsIt = FlowConditionDeps.find(Val: Token);
236 DepsIt != FlowConditionDeps.end())
237 for (Atom A : DepsIt->second)
238 Remaining.push_back(x: A);
239 }
240}
241
242static void printAtomList(const llvm::SmallVector<Atom> &Atoms,
243 llvm::raw_ostream &OS) {
244 OS << "(";
245 for (size_t i = 0; i < Atoms.size(); ++i) {
246 OS << Atoms[i];
247 if (i + 1 < Atoms.size())
248 OS << ", ";
249 }
250 OS << ")\n";
251}
252
253void DataflowAnalysisContext::dumpFlowCondition(Atom Token,
254 llvm::raw_ostream &OS) {
255 llvm::SetVector<const Formula *> Constraints;
256 Constraints.insert(X: &arena().makeAtomRef(A: Token));
257 addTransitiveFlowConditionConstraints(Token, Constraints);
258
259 OS << "Flow condition token: " << Token << "\n";
260 SimplifyConstraintsInfo Info;
261 llvm::SetVector<const Formula *> OriginalConstraints = Constraints;
262 simplifyConstraints(Constraints, arena&: arena(), Info: &Info);
263 if (!Constraints.empty()) {
264 OS << "Constraints:\n";
265 for (const auto *Constraint : Constraints) {
266 Constraint->print(OS);
267 OS << "\n";
268 }
269 }
270 if (!Info.TrueAtoms.empty()) {
271 OS << "True atoms: ";
272 printAtomList(Atoms: Info.TrueAtoms, OS);
273 }
274 if (!Info.FalseAtoms.empty()) {
275 OS << "False atoms: ";
276 printAtomList(Atoms: Info.FalseAtoms, OS);
277 }
278 if (!Info.EquivalentAtoms.empty()) {
279 OS << "Equivalent atoms:\n";
280 for (const llvm::SmallVector<Atom> &Class : Info.EquivalentAtoms)
281 printAtomList(Atoms: Class, OS);
282 }
283
284 OS << "\nFlow condition constraints before simplification:\n";
285 for (const auto *Constraint : OriginalConstraints) {
286 Constraint->print(OS);
287 OS << "\n";
288 }
289}
290
291const AdornedCFG *
292DataflowAnalysisContext::getAdornedCFG(const FunctionDecl *F) {
293 // Canonicalize the key:
294 F = F->getDefinition();
295 if (F == nullptr)
296 return nullptr;
297 auto It = FunctionContexts.find(Val: F);
298 if (It != FunctionContexts.end())
299 return &It->second;
300
301 if (F->doesThisDeclarationHaveABody()) {
302 auto ACFG = AdornedCFG::build(Func: *F);
303 // FIXME: Handle errors.
304 assert(ACFG);
305 auto Result = FunctionContexts.insert(KV: {F, std::move(*ACFG)});
306 return &Result.first->second;
307 }
308
309 return nullptr;
310}
311
312static std::unique_ptr<Logger> makeLoggerFromCommandLine() {
313 if (DataflowLog.empty())
314 return Logger::textual(llvm::errs());
315
316 llvm::StringRef Dir = DataflowLog;
317 if (auto EC = llvm::sys::fs::create_directories(path: Dir))
318 llvm::errs() << "Failed to create log dir: " << EC.message() << "\n";
319 // All analysis runs within a process will log to the same directory.
320 // Share a counter so they don't all overwrite each other's 0.html.
321 // (Don't share a logger, it's not threadsafe).
322 static std::atomic<unsigned> Counter = {0};
323 auto StreamFactory =
324 [Dir(Dir.str())]() mutable -> std::unique_ptr<llvm::raw_ostream> {
325 llvm::SmallString<256> File(Dir);
326 llvm::sys::path::append(path&: File,
327 a: std::to_string(val: Counter.fetch_add(i: 1)) + ".html");
328 std::error_code EC;
329 auto OS = std::make_unique<llvm::raw_fd_ostream>(args&: File, args&: EC);
330 if (EC) {
331 llvm::errs() << "Failed to create log " << File << ": " << EC.message()
332 << "\n";
333 return std::make_unique<llvm::raw_null_ostream>();
334 }
335 return OS;
336 };
337 return Logger::html(std::move(StreamFactory));
338}
339
340DataflowAnalysisContext::DataflowAnalysisContext(
341 Solver &S, std::unique_ptr<Solver> &&OwnedSolver, Options Opts)
342 : S(S), OwnedSolver(std::move(OwnedSolver)), A(std::make_unique<Arena>()),
343 Opts(Opts) {
344 // If the -dataflow-log command-line flag was set, synthesize a logger.
345 // This is ugly but provides a uniform method for ad-hoc debugging dataflow-
346 // based tools.
347 if (Opts.Log == nullptr) {
348 if (DataflowLog.getNumOccurrences() > 0) {
349 LogOwner = makeLoggerFromCommandLine();
350 this->Opts.Log = LogOwner.get();
351 // FIXME: if the flag is given a value, write an HTML log to a file.
352 } else {
353 this->Opts.Log = &Logger::null();
354 }
355 }
356}
357
358DataflowAnalysisContext::~DataflowAnalysisContext() = default;
359
360} // namespace dataflow
361} // namespace clang
362