Subversion Repositories QNX 8.QNX8 LLVM/Clang compiler suite

//===- DAGDeltaAlgorithm.h - A DAG Minimization Algorithm ------*- 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

//===----------------------------------------------------------------------===//

#ifndef LLVM_ADT_DAGDELTAALGORITHM_H

#define LLVM_ADT_DAGDELTAALGORITHM_H

#include <set>

#include <utility>

#include <vector>

namespace llvm {

/// DAGDeltaAlgorithm - Implements a "delta debugging" algorithm for minimizing

/// directed acyclic graphs using a predicate function.

///

/// The result of the algorithm is a subset of the input change set which is

/// guaranteed to satisfy the predicate, assuming that the input set did. For

/// well formed predicates, the result set is guaranteed to be such that

/// removing any single element not required by the dependencies on the other

/// elements would falsify the predicate.

///

/// The DAG should be used to represent dependencies in the changes which are

/// likely to hold across the predicate function. That is, for a particular

/// changeset S and predicate P:

///

///   P(S) => P(S union pred(S))

///

/// The minimization algorithm uses this dependency information to attempt to

/// eagerly prune large subsets of changes. As with \see DeltaAlgorithm, the DAG

/// is not required to satisfy this property, but the algorithm will run

/// substantially fewer tests with appropriate dependencies. \see DeltaAlgorithm

/// for more information on the properties which the predicate function itself

/// should satisfy.

class DAGDeltaAlgorithm {

  virtual void anchor();

public:

  using change_ty = unsigned;

  using edge_ty = std::pair<change_ty, change_ty>;

  // FIXME: Use a decent data structure.

  using changeset_ty = std::set<change_ty>;

  using changesetlist_ty = std::vector<changeset_ty>;

public:

  virtual ~DAGDeltaAlgorithm() = default;

  /// Run - Minimize the DAG formed by the \p Changes vertices and the

  /// \p Dependencies edges by executing \see ExecuteOneTest() on subsets of

  /// changes and returning the smallest set which still satisfies the test

  /// predicate and the input \p Dependencies.

  ///

  /// \param Changes The list of changes.

  ///

  /// \param Dependencies The list of dependencies amongst changes. For each

  /// (x,y) in \p Dependencies, both x and y must be in \p Changes. The

  /// minimization algorithm guarantees that for each tested changed set S,

  /// \f$ x \in S \f$ implies \f$ y \in S \f$. It is an error to have cyclic

  /// dependencies.

  changeset_ty Run(const changeset_ty &Changes,

                   const std::vector<edge_ty> &Dependencies);

  /// UpdatedSearchState - Callback used when the search state changes.

  virtual void UpdatedSearchState(const changeset_ty &Changes,

                                  const changesetlist_ty &Sets,

                                  const changeset_ty &Required) {}

  /// ExecuteOneTest - Execute a single test predicate on the change set \p S.

  virtual bool ExecuteOneTest(const changeset_ty &S) = 0;

};

} // end namespace llvm

#endif // LLVM_ADT_DAGDELTAALGORITHM_H