| //===- WatchedLiteralsSolver.h ----------------------------------*- 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 a SAT solver implementation that can be used by dataflow |
| // analyses. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_CLANG_ANALYSIS_FLOWSENSITIVE_WATCHEDLITERALSSOLVER_H |
| #define LLVM_CLANG_ANALYSIS_FLOWSENSITIVE_WATCHEDLITERALSSOLVER_H |
| |
| #include "clang/Analysis/FlowSensitive/Formula.h" |
| #include "clang/Analysis/FlowSensitive/Solver.h" |
| #include "llvm/ADT/ArrayRef.h" |
| #include <limits> |
| |
| namespace clang { |
| namespace dataflow { |
| |
| /// A SAT solver that is an implementation of Algorithm D from Knuth's The Art |
| /// of Computer Programming Volume 4: Satisfiability, Fascicle 6. It is based on |
| /// the Davis-Putnam-Logemann-Loveland (DPLL) algorithm, keeps references to a |
| /// single "watched" literal per clause, and uses a set of "active" variables |
| /// for unit propagation. |
| class WatchedLiteralsSolver : public Solver { |
| // Count of the iterations of the main loop of the solver. This spans *all* |
| // calls to the underlying solver across the life of this object. It is |
| // reduced with every (non-trivial) call to the solver. |
| // |
| // We give control over the abstract count of iterations instead of concrete |
| // measurements like CPU cycles or time to ensure deterministic results. |
| std::int64_t MaxIterations = std::numeric_limits<std::int64_t>::max(); |
| |
| public: |
| WatchedLiteralsSolver() = default; |
| |
| // `Work` specifies a computational limit on the solver. Units of "work" |
| // roughly correspond to attempts to assign a value to a single |
| // variable. Since the algorithm is exponential in the number of variables, |
| // this is the most direct (abstract) unit to target. |
| explicit WatchedLiteralsSolver(std::int64_t WorkLimit) |
| : MaxIterations(WorkLimit) {} |
| |
| Result solve(llvm::ArrayRef<const Formula *> Vals) override; |
| |
| // The solver reached its maximum number of iterations. |
| bool reachedLimit() const { return MaxIterations == 0; } |
| }; |
| |
| } // namespace dataflow |
| } // namespace clang |
| |
| #endif // LLVM_CLANG_ANALYSIS_FLOWSENSITIVE_WATCHEDLITERALSSOLVER_H |