1 //===- DAGDeltaAlgorithm.h - A DAG Minimization Algorithm ------*- C++ -*--===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 //===----------------------------------------------------------------------===// 7 8 #ifndef LLVM_ADT_DAGDELTAALGORITHM_H 9 #define LLVM_ADT_DAGDELTAALGORITHM_H 10 11 #include <set> 12 #include <utility> 13 #include <vector> 14 15 namespace llvm { 16 17 /// DAGDeltaAlgorithm - Implements a "delta debugging" algorithm for minimizing 18 /// directed acyclic graphs using a predicate function. 19 /// 20 /// The result of the algorithm is a subset of the input change set which is 21 /// guaranteed to satisfy the predicate, assuming that the input set did. For 22 /// well formed predicates, the result set is guaranteed to be such that 23 /// removing any single element not required by the dependencies on the other 24 /// elements would falsify the predicate. 25 /// 26 /// The DAG should be used to represent dependencies in the changes which are 27 /// likely to hold across the predicate function. That is, for a particular 28 /// changeset S and predicate P: 29 /// 30 /// P(S) => P(S union pred(S)) 31 /// 32 /// The minimization algorithm uses this dependency information to attempt to 33 /// eagerly prune large subsets of changes. As with \see DeltaAlgorithm, the DAG 34 /// is not required to satisfy this property, but the algorithm will run 35 /// substantially fewer tests with appropriate dependencies. \see DeltaAlgorithm 36 /// for more information on the properties which the predicate function itself 37 /// should satisfy. 38 class DAGDeltaAlgorithm { 39 virtual void anchor(); 40 41 public: 42 using change_ty = unsigned; 43 using edge_ty = std::pair<change_ty, change_ty>; 44 45 // FIXME: Use a decent data structure. 46 using changeset_ty = std::set<change_ty>; 47 using changesetlist_ty = std::vector<changeset_ty>; 48 49 public: 50 virtual ~DAGDeltaAlgorithm() = default; 51 52 /// Run - Minimize the DAG formed by the \p Changes vertices and the 53 /// \p Dependencies edges by executing \see ExecuteOneTest() on subsets of 54 /// changes and returning the smallest set which still satisfies the test 55 /// predicate and the input \p Dependencies. 56 /// 57 /// \param Changes The list of changes. 58 /// 59 /// \param Dependencies The list of dependencies amongst changes. For each 60 /// (x,y) in \p Dependencies, both x and y must be in \p Changes. The 61 /// minimization algorithm guarantees that for each tested changed set S, 62 /// \f$ x \in S \f$ implies \f$ y \in S \f$. It is an error to have cyclic 63 /// dependencies. 64 changeset_ty Run(const changeset_ty &Changes, 65 const std::vector<edge_ty> &Dependencies); 66 67 /// UpdatedSearchState - Callback used when the search state changes. 68 virtual void UpdatedSearchState(const changeset_ty &Changes, 69 const changesetlist_ty &Sets, 70 const changeset_ty &Required) {} 71 72 /// ExecuteOneTest - Execute a single test predicate on the change set \p S. 73 virtual bool ExecuteOneTest(const changeset_ty &S) = 0; 74 }; 75 76 } // end namespace llvm 77 78 #endif // LLVM_ADT_DAGDELTAALGORITHM_H 79