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/*
This file is part of solidity.
solidity is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
solidity is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with solidity. If not, see <http://www.gnu.org/licenses/>.
*/
/**
* @author Alex Beregszaszi
* Removes unused JUMPDESTs.
*/
#include "JumpdestRemover.h"
#include <libsolidity/interface/Exceptions.h>
#include <libevmasm/AssemblyItem.h>
using namespace std;
using namespace dev::eth;
using namespace dev;
bool JumpdestRemover::optimise(set<size_t> const& _tagsReferencedFromOutside)
{
set<size_t> references{referencedTags(m_items, -1)};
references.insert(_tagsReferencedFromOutside.begin(), _tagsReferencedFromOutside.end());
size_t initialSize = m_items.size();
/// Remove tags which are never referenced.
auto pend = remove_if(
m_items.begin(),
m_items.end(),
[&](AssemblyItem const& _item)
{
if (_item.type() != Tag)
return false;
auto asmIdAndTag = _item.splitForeignPushTag();
solAssert(asmIdAndTag.first == size_t(-1), "Sub-assembly tag used as label.");
size_t tag = asmIdAndTag.second;
return !references.count(tag);
}
);
m_items.erase(pend, m_items.end());
return m_items.size() != initialSize;
}
set<size_t> JumpdestRemover::referencedTags(AssemblyItems const& _items, size_t _subId)
{
set<size_t> ret;
for (auto const& item: _items)
if (item.type() == PushTag)
{
auto subAndTag = item.splitForeignPushTag();
if (subAndTag.first == _subId)
ret.insert(subAndTag.second);
}
return ret;
}
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