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64 lines
2.4 KiB
C++
64 lines
2.4 KiB
C++
// -*- mode: C++; c-file-style: "cc-mode" -*-
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//*************************************************************************
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// DESCRIPTION: Verilator: DAG Path Checking
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//
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// Code available from: https://verilator.org
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//
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//*************************************************************************
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//
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// Copyright 2003-2021 by Wilson Snyder. This program is free software; you
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// can redistribute it and/or modify it under the terms of either the GNU
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// Lesser General Public License Version 3 or the Perl Artistic License
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// Version 2.0.
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// SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
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//
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//*************************************************************************
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#ifndef VERILATOR_V3GRAPHPATHCHECKER_H_
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#define VERILATOR_V3GRAPHPATHCHECKER_H_
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#include "V3Error.h"
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#include "V3Graph.h"
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#include "V3GraphAlg.h"
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//######################################################################
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/// Implement pathExistsFrom() with some caching to prune the search.
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/// Far more aggressive caching/pruning is possible; for now the use cases
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/// don't rely so heavily on this class that it's necessary.
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///
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/// The graph (or at least, the subset the algorithm sees through
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/// edgeFuncp) must not change during the lifetime of the checker.
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class GraphPathChecker final : GraphAlg<const V3Graph> {
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// Count "generations" which increases on operations that scan through
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// the graph. Each node is marked with the last generation that scanned
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// it, to enable asserting there are no cycles, and to avoid recursing
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// through the same node twice while searching for a path.
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vluint64_t m_generation = 0;
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public:
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// CONSTRUCTORS
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explicit GraphPathChecker(const V3Graph* graphp,
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V3EdgeFuncP edgeFuncp = V3GraphEdge::followAlwaysTrue);
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~GraphPathChecker();
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// METHODS
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bool pathExistsFrom(const V3GraphVertex* fromp, const V3GraphVertex* top);
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// If have edges A->B, B->C, and A->C then A->C is considered a
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// "transitive" edge (implied by A->B and B->C) and it could be safely
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// removed. Detect such an edge.
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bool isTransitiveEdge(const V3GraphEdge* edgep);
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private:
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bool pathExistsInternal(const V3GraphVertex* ap, const V3GraphVertex* bp,
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unsigned* costp = nullptr);
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void initHalfCriticalPaths(GraphWay way, bool checkOnly);
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void incGeneration() { ++m_generation; }
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VL_DEBUG_FUNC; // Declare debug()
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VL_UNCOPYABLE(GraphPathChecker);
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};
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#endif // Guard
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