Solver.h

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//===- Solver.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 an interface for a SAT solver that can be used by
//  dataflow analyses.
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_CLANG_ANALYSIS_FLOWSENSITIVE_SOLVER_H
#define LLVM_CLANG_ANALYSIS_FLOWSENSITIVE_SOLVER_H
 
#include "clang/Analysis/FlowSensitive/Formula.h"
#include "clang/Basic/LLVM.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include <optional>
#include <vector>
 
namespace clang {
namespace dataflow {
 
/// An interface for a SAT solver that can be used by dataflow analyses.
class Solver {
public:
  struct Result {
    enum class Status {
      /// Indicates that there exists a satisfying assignment for a boolean
      /// formula.
      Satisfiable,
 
      /// Indicates that there is no satisfying assignment for a boolean
      /// formula.
      Unsatisfiable,
 
      /// Indicates that the solver gave up trying to find a satisfying
      /// assignment for a boolean formula.
      TimedOut,
    };
 
    /// A boolean value is set to true or false in a truth assignment.
    enum class Assignment : uint8_t { AssignedFalse = 0, AssignedTrue = 1 };
 
    /// Constructs a result indicating that the queried boolean formula is
    /// satisfiable. The result will hold a solution found by the solver.
    static Result Satisfiable(llvm::DenseMap<Atom, Assignment> Solution) {
      return Result(Status::Satisfiable, std::move(Solution));
    }
 
    /// Constructs a result indicating that the queried boolean formula is
    /// unsatisfiable.
    static Result Unsatisfiable() { return Result(Status::Unsatisfiable, {}); }
 
    /// Constructs a result indicating that satisfiability checking on the
    /// queried boolean formula was not completed.
    static Result TimedOut() { return Result(Status::TimedOut, {}); }
 
    /// Returns the status of satisfiability checking on the queried boolean
    /// formula.
    Status getStatus() const { return SATCheckStatus; }
 
    /// Returns a truth assignment to boolean values that satisfies the queried
    /// boolean formula if available. Otherwise, an empty optional is returned.
    std::optional<llvm::DenseMap<Atom, Assignment>> getSolution() const {
      return Solution;
    }
 
  private:
    Result(Status SATCheckStatus,
           std::optional<llvm::DenseMap<Atom, Assignment>> Solution)
        : SATCheckStatus(SATCheckStatus), Solution(std::move(Solution)) {}
 
    Status SATCheckStatus;
    std::optional<llvm::DenseMap<Atom, Assignment>> Solution;
  };
 
  virtual ~Solver() = default;
 
  /// Checks if the conjunction of `Vals` is satisfiable and returns the
  /// corresponding result.
  ///
  /// Requirements:
  ///
  ///  All elements in `Vals` must not be null.
  virtual Result solve(llvm::ArrayRef<const Formula *> Vals) = 0;
};
 
llvm::raw_ostream &operator<<(llvm::raw_ostream &, const Solver::Result &);
llvm::raw_ostream &operator<<(llvm::raw_ostream &, Solver::Result::Assignment);
 
} // namespace dataflow
} // namespace clang
 
#endif // LLVM_CLANG_ANALYSIS_FLOWSENSITIVE_SOLVER_H