clang 19.0.0git
WatchedLiteralsSolver.h
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1//===- WatchedLiteralsSolver.h ----------------------------------*- 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//
9// This file defines a SAT solver implementation that can be used by dataflow
10// analyses.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_CLANG_ANALYSIS_FLOWSENSITIVE_WATCHEDLITERALSSOLVER_H
15#define LLVM_CLANG_ANALYSIS_FLOWSENSITIVE_WATCHEDLITERALSSOLVER_H
16
19#include "llvm/ADT/ArrayRef.h"
20
21namespace clang {
22namespace dataflow {
23
24/// A SAT solver that is an implementation of Algorithm D from Knuth's The Art
25/// of Computer Programming Volume 4: Satisfiability, Fascicle 6. It is based on
26/// the Davis-Putnam-Logemann-Loveland (DPLL) algorithm [1], keeps references to
27/// a single "watched" literal per clause, and uses a set of "active" variables
28/// for unit propagation.
29//
30// [1] https://en.wikipedia.org/wiki/DPLL_algorithm
32 // Count of the iterations of the main loop of the solver. This spans *all*
33 // calls to the underlying solver across the life of this object. It is
34 // reduced with every (non-trivial) call to the solver.
35 //
36 // We give control over the abstract count of iterations instead of concrete
37 // measurements like CPU cycles or time to ensure deterministic results.
38 std::int64_t MaxIterations = std::numeric_limits<std::int64_t>::max();
39
40public:
42
43 // `Work` specifies a computational limit on the solver. Units of "work"
44 // roughly correspond to attempts to assign a value to a single
45 // variable. Since the algorithm is exponential in the number of variables,
46 // this is the most direct (abstract) unit to target.
47 explicit WatchedLiteralsSolver(std::int64_t WorkLimit)
48 : MaxIterations(WorkLimit) {}
49
50 Result solve(llvm::ArrayRef<const Formula *> Vals) override;
51
52 bool reachedLimit() const override { return MaxIterations == 0; }
53};
54
55} // namespace dataflow
56} // namespace clang
57
58#endif // LLVM_CLANG_ANALYSIS_FLOWSENSITIVE_WATCHEDLITERALSSOLVER_H
An interface for a SAT solver that can be used by dataflow analyses.
Definition: Solver.h:28
A SAT solver that is an implementation of Algorithm D from Knuth's The Art of Computer Programming Vo...
Result solve(llvm::ArrayRef< const Formula * > Vals) override
Checks if the conjunction of Vals is satisfiable and returns the corresponding result.
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