solidity/libyul/optimiser/ConditionalSimplifier.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/OptimiserStep.h>
#include <libyul/Dialect.h>
#include <libsolutil/Common.h>
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namespace solidity::yul
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{
/**
* Conditional simplifier.
*
* Inserts assignments to condition variables if the value can be determined
* from the control-flow.
*
* Destroys SSA form.
*
* Currently, this tool is very limited, mostly because we do not yet have support
* for boolean types. Since conditions only check for expressions being nonzero,
* we cannot assign a specific value.
*
* Current features:
* - switch cases: insert "<condition> := <caseLabel>"
* - after if statement with terminating control-flow, insert "<condition> := 0"
*
* Future features:
* - allow replacements by "1"
* - take termination of user-defined functions into account
*
* Works best with SSA form and if dead code removal has run before.
*
* Prerequisite: Disambiguator.
*/
class ConditionalSimplifier: public ASTModifier
{
public:
static constexpr char const* name{"ConditionalSimplifier"};
static void run(OptimiserStepContext& _context, Block& _ast)
{
ConditionalSimplifier{_context.dialect}(_ast);
}
using ASTModifier::operator();
void operator()(Switch& _switch) override;
void operator()(Block& _block) override;
private:
explicit ConditionalSimplifier(Dialect const& _dialect):
m_dialect(_dialect)
{}
Dialect const& m_dialect;
};
}