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//===- Z3CrosscheckVisitor.h - Crosscheck reports with Z3 -------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file defines the visitor and utilities around it for Z3 report
// refutation.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CLANG_STATICANALYZER_CORE_BUGREPORTER_Z3CROSSCHECKVISITOR_H
#define LLVM_CLANG_STATICANALYZER_CORE_BUGREPORTER_Z3CROSSCHECKVISITOR_H
#include "clang/StaticAnalyzer/Core/BugReporter/BugReporterVisitors.h"
namespace clang::ento {
/// The bug visitor will walk all the nodes in a path and collect all the
/// constraints. When it reaches the root node, will create a refutation
/// manager and check if the constraints are satisfiable.
class Z3CrosscheckVisitor final : public BugReporterVisitor {
public:
struct Z3Result {
std::optional<bool> IsSAT = std::nullopt;
unsigned Z3QueryTimeMilliseconds = 0;
unsigned UsedRLimit = 0;
};
Z3CrosscheckVisitor(Z3CrosscheckVisitor::Z3Result &Result,
const AnalyzerOptions &Opts);
void Profile(llvm::FoldingSetNodeID &ID) const override;
PathDiagnosticPieceRef VisitNode(const ExplodedNode *N,
BugReporterContext &BRC,
PathSensitiveBugReport &BR) override;
void finalizeVisitor(BugReporterContext &BRC, const ExplodedNode *EndPathNode,
PathSensitiveBugReport &BR) override;
private:
void addConstraints(const ExplodedNode *N,
bool OverwriteConstraintsOnExistingSyms);
/// Holds the constraints in a given path.
ConstraintMap Constraints;
Z3Result &Result;
const AnalyzerOptions &Opts;
};
/// The oracle will decide if a report should be accepted or rejected based on
/// the results of the Z3 solver and the statistics of the queries of a report
/// equivalenece class.
class Z3CrosscheckOracle {
public:
explicit Z3CrosscheckOracle(const AnalyzerOptions &Opts) : Opts(Opts) {}
enum Z3Decision {
AcceptReport, // The report was SAT.
RejectReport, // The report was UNSAT or UNDEF.
RejectEQClass, // The heuristic suggests to skip the current eqclass.
};
/// Updates the internal state with the new Z3Result and makes a decision how
/// to proceed:
/// - Accept the report if the Z3Result was SAT.
/// - Suggest dropping the report equvalence class based on the accumulated
/// statistics.
/// - Otherwise, reject the report if the Z3Result was UNSAT or UNDEF.
///
/// Conditions for dropping the equivalence class:
/// - Accumulative time spent in Z3 checks is more than 700ms in the eqclass.
/// - Hit the 300ms query timeout in the report eqclass.
/// - Hit the 400'000 rlimit in the report eqclass.
///
/// All these thresholds are configurable via the analyzer options.
///
/// Refer to
/// https://discourse.llvm.org/t/analyzer-rfc-taming-z3-query-times/79520 to
/// see why this heuristic was chosen.
Z3Decision interpretQueryResult(const Z3CrosscheckVisitor::Z3Result &Meta);
private:
const AnalyzerOptions &Opts;
unsigned AccumulatedZ3QueryTimeInEqClass = 0; // ms
};
} // namespace clang::ento
#endif // LLVM_CLANG_STATICANALYZER_CORE_BUGREPORTER_Z3CROSSCHECKVISITOR_H