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fixup! Implementation of Lengauer-Tarjan algorithm to find dominators

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Kamil Śliwak 2023-08-11 19:51:19 +02:00 committed by r0qs
parent e4bac1340d
commit b7ec9d3fdd
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GPG Key ID: 61503DBA6667276C
1 changed files with 14 additions and 11 deletions
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25
libyul/backends/evm/Dominator.h
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@ -27,6 +27,11 @@
#include <libyul/backends/evm/ControlFlowGraph.h>
#include <libsolutil/Visitor.h>
#include <range/v3/algorithm.hpp>
#include <range/v3/view/drop.hpp>
#include <range/v3/view/reverse.hpp>
#include <range/v3/view/transform.hpp>
#include <deque>
#include <map>
#include <vector>
@ -117,8 +122,8 @@ public:
solAssert(!m_immediateDominator.empty());
//Ignoring the entry node since no one dominates it.
for (size_t i = 1; i < m_immediateDominator.size(); ++i)
m_dominatorTree[m_immediateDominator[i]].emplace_back(i);
for (size_t idomIdx: m_immediateDominator | ranges::views::drop(1))
m_dominatorTree[idomIdx].emplace_back(idomIdx);
}
// Path compression updates the ancestors of vertices along
@ -177,6 +182,8 @@ public:
return _v;
};
auto toIdx = [&](Vertex const& v) { return m_vertexIndex[v]; };
// step 1
std::set<Vertex> visited;
// predecessors(w): The set of vertices ``v`` such that (``v``, ``w``) is an edge of the graph.
@ -210,9 +217,8 @@ public:
dfs(_entry, dfs);
// Process the vertices in decreasing order of the dfs number
for (auto it = m_vertex.rbegin(); it != m_vertex.rend(); ++it)
for (size_t w: m_vertex | ranges::views::reverse | ranges::views::transform(toIdx))
{
Vertex const& w = m_vertexIndex[*it];
// step 3
// NOTE: this is an optimization, i.e. performing the step 3 before step 2.
// The goal is to process the bucket in the beginning of the loop for the vertex ``w``
@ -220,9 +226,8 @@ public:
// Inverting those steps ensures that a bucket is only processed once and
// it does not need to be erased.
// The optimization proposal is available here: https://jgaa.info/accepted/2006/GeorgiadisTarjanWerneck2006.10.1.pdf pg.77
for_each(
bucket[w].begin(),
bucket[w].end(),
ranges::for_each(
bucket[w],
[&](size_t v)
{
size_t u = eval(v);
@ -243,12 +248,10 @@ public:
// step 4
idom[0] = 0;
for (auto it = m_vertex.begin() + 1; it != m_vertex.end(); ++it)
{
size_t w = m_vertexIndex[*it];
for (size_t w: m_vertex | ranges::views::drop(1) | ranges::views::transform(toIdx))
if (idom[w] != semi[w])
idom[w] = idom[idom[w]];
}
return idom;
}
private: