solidity/libyul/optimiser/StructuralSimplifier.h

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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/>.
*/
#pragma once
#include <libyul/optimiser/ASTWalker.h>
#include <libyul/optimiser/DataFlowAnalyzer.h>
#include <libdevcore/Common.h>
namespace yul
{
/**
* Structural simplifier. Performs the following simplification steps:
* - replace if with empty body with pop(condition)
* - replace if with true condition with its body
* - remove if with false condition
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* - remove empty default switch case
* - remove empty switch case if no default case exists
* - replace switch with no cases with pop(expression)
* - turn switch with single case into if
* - replace switch with only default case with pop(expression) and body
* - replace switch with const expr with matching case body
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* - replace for with false condition by its initialization part
*
* Prerequisite: Disambiguator, ForLoopInitRewriter.
*
* Important: Can only be used on EVM code.
*/
class StructuralSimplifier: public DataFlowAnalyzer
{
public:
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explicit StructuralSimplifier(Dialect const& _dialect): DataFlowAnalyzer(_dialect) {}
using DataFlowAnalyzer::operator();
void operator()(Block& _block) override;
private:
void simplify(std::vector<Statement>& _statements);
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bool expressionAlwaysTrue(Expression const& _expression);
bool expressionAlwaysFalse(Expression const& _expression);
boost::optional<dev::u256> hasLiteralValue(Expression const& _expression) const;
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boost::optional<std::vector<Statement>> reduceNoCaseSwitch(Switch& _switchStmt) const;
};
}