Merge "Update prebuilt Clang to r353983." into p9.0HEADp9.0-backupp9.0

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diff --git a/clang-r353983/include/llvm/ADT/DAGDeltaAlgorithm.h b/clang-r353983/include/llvm/ADT/DAGDeltaAlgorithm.h
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+//===- 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 minization 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