1//===- DAGDeltaAlgorithm.h - A DAG Minimization Algorithm ------*- C++ -*--===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7//===----------------------------------------------------------------------===// 8 9#ifndef LLVM_ADT_DAGDELTAALGORITHM_H 10#define LLVM_ADT_DAGDELTAALGORITHM_H 11 12#include <set> 13#include <utility> 14#include <vector> 15 16namespace llvm { 17 18/// DAGDeltaAlgorithm - Implements a "delta debugging" algorithm for minimizing 19/// directed acyclic graphs using a predicate function. 20/// 21/// The result of the algorithm is a subset of the input change set which is 22/// guaranteed to satisfy the predicate, assuming that the input set did. For 23/// well formed predicates, the result set is guaranteed to be such that 24/// removing any single element not required by the dependencies on the other 25/// elements would falsify the predicate. 26/// 27/// The DAG should be used to represent dependencies in the changes which are 28/// likely to hold across the predicate function. That is, for a particular 29/// changeset S and predicate P: 30/// 31/// P(S) => P(S union pred(S)) 32/// 33/// The minization algorithm uses this dependency information to attempt to 34/// eagerly prune large subsets of changes. As with \see DeltaAlgorithm, the DAG 35/// is not required to satisfy this property, but the algorithm will run 36/// substantially fewer tests with appropriate dependencies. \see DeltaAlgorithm 37/// for more information on the properties which the predicate function itself 38/// should satisfy. 39class DAGDeltaAlgorithm { 40 virtual void anchor(); 41 42public: 43 using change_ty = unsigned; 44 using edge_ty = std::pair<change_ty, change_ty>; 45 46 // FIXME: Use a decent data structure. 47 using changeset_ty = std::set<change_ty>; 48 using changesetlist_ty = std::vector<changeset_ty>; 49 50public: 51 virtual ~DAGDeltaAlgorithm() = default; 52 53 /// Run - Minimize the DAG formed by the \p Changes vertices and the 54 /// \p Dependencies edges by executing \see ExecuteOneTest() on subsets of 55 /// changes and returning the smallest set which still satisfies the test 56 /// predicate and the input \p Dependencies. 57 /// 58 /// \param Changes The list of changes. 59 /// 60 /// \param Dependencies The list of dependencies amongst changes. For each 61 /// (x,y) in \p Dependencies, both x and y must be in \p Changes. The 62 /// minimization algorithm guarantees that for each tested changed set S, 63 /// \f$ x \in S \f$ implies \f$ y \in S \f$. It is an error to have cyclic 64 /// dependencies. 65 changeset_ty Run(const changeset_ty &Changes, 66 const std::vector<edge_ty> &Dependencies); 67 68 /// UpdatedSearchState - Callback used when the search state changes. 69 virtual void UpdatedSearchState(const changeset_ty &Changes, 70 const changesetlist_ty &Sets, 71 const changeset_ty &Required) {} 72 73 /// ExecuteOneTest - Execute a single test predicate on the change set \p S. 74 virtual bool ExecuteOneTest(const changeset_ty &S) = 0; 75}; 76 77} // end namespace llvm 78 79#endif // LLVM_ADT_DAGDELTAALGORITHM_H 80