solidity/libyul/optimiser/ConditionalUnsimplifier.cpp

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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/>.
*/
// SPDX-License-Identifier: GPL-3.0
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#include <libyul/optimiser/ConditionalUnsimplifier.h>
#include <libyul/optimiser/Semantics.h>
#include <libyul/AsmData.h>
#include <libyul/Utilities.h>
#include <libyul/optimiser/NameCollector.h>
#include <libsolutil/CommonData.h>
#include <libsolutil/Visitor.h>
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using namespace std;
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using namespace solidity;
using namespace solidity::yul;
using namespace solidity::util;
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void ConditionalUnsimplifier::operator()(Switch& _switch)
{
visit(*_switch.expression);
if (!holds_alternative<Identifier>(*_switch.expression))
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{
ASTModifier::operator()(_switch);
return;
}
YulString expr = std::get<Identifier>(*_switch.expression).name;
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for (auto& _case: _switch.cases)
{
if (_case.value)
{
(*this)(*_case.value);
if (
!_case.body.statements.empty() &&
holds_alternative<Assignment>(_case.body.statements.front())
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)
{
Assignment const& assignment = std::get<Assignment>(_case.body.statements.front());
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if (
assignment.variableNames.size() == 1 &&
assignment.variableNames.front().name == expr &&
holds_alternative<Literal>(*assignment.value) &&
valueOfLiteral(std::get<Literal>(*assignment.value)) == valueOfLiteral(*_case.value)
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)
_case.body.statements.erase(_case.body.statements.begin());
}
}
(*this)(_case.body);
}
}
void ConditionalUnsimplifier::operator()(Block& _block)
{
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walkVector(_block.statements);
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iterateReplacingWindow<2>(
_block.statements,
[&](Statement& _stmt1, Statement& _stmt2) -> std::optional<vector<Statement>>
{
if (holds_alternative<If>(_stmt1))
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{
If& _if = std::get<If>(_stmt1);
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if (
holds_alternative<Identifier>(*_if.condition) &&
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!_if.body.statements.empty()
)
{
YulString condition = std::get<Identifier>(*_if.condition).name;
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if (
holds_alternative<Assignment>(_stmt2) &&
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TerminationFinder(m_dialect).controlFlowKind(_if.body.statements.back()) !=
TerminationFinder::ControlFlow::FlowOut
)
{
Assignment const& assignment = std::get<Assignment>(_stmt2);
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if (
assignment.variableNames.size() == 1 &&
assignment.variableNames.front().name == condition &&
holds_alternative<Literal>(*assignment.value) &&
valueOfLiteral(std::get<Literal>(*assignment.value)) == 0
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)
return {make_vector<Statement>(std::move(_stmt1))};
}
}
}
return {};
}
);
}