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/*
* Copyright (C) 2019 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include <wtf/GraphNodeWorklist.h>
template<typename Graph>
class SpanningTree {
WTF_MAKE_FAST_ALLOCATED;
public:
SpanningTree(Graph& graph)
: m_graph(graph)
, m_data(graph.template newMap<Data>())
{
ExtendedGraphNodeWorklist<typename Graph::Node, unsigned, typename Graph::Set> worklist;
worklist.push(m_graph.root(), 0);
size_t number = 0;
while (GraphNodeWith<typename Graph::Node, unsigned> item = worklist.pop()) {
typename Graph::Node block = item.node;
unsigned successorIndex = item.data;
// We initially push with successorIndex = 0 regardless of whether or not we have any
// successors. This is so that we can assign our prenumber. Subsequently we get pushed
// with higher successorIndex values. We finally push successorIndex == # successors
// to calculate our post number.
ASSERT(!successorIndex || successorIndex <= m_graph.successors(block).size());
if (!successorIndex)
m_data[block].pre = number++;
if (successorIndex < m_graph.successors(block).size()) {
unsigned nextSuccessorIndex = successorIndex + 1;
// We need to push this even if this is out of bounds so we can compute
// the post number.
worklist.forcePush(block, nextSuccessorIndex);
typename Graph::Node successorBlock = m_graph.successors(block)[successorIndex];
worklist.push(successorBlock, 0);
} else
m_data[block].post = number++;
}
}
// Returns true if a is a descendent of b.
// Note a is a descendent of b if they're equal.
bool isDescendent(typename Graph::Node a, typename Graph::Node b)
{
return m_data[b].pre <= m_data[a].pre
&& m_data[b].post >= m_data[a].post;
}
private:
struct Data {
WTF_MAKE_STRUCT_FAST_ALLOCATED;
size_t pre;
size_t post;
};
Graph& m_graph;
typename Graph::template Map<Data> m_data;
};
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