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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/>.
*/
/**
* Optimisation stage that removes unused variables and functions.
*/
#pragma once
#include <libyul/optimiser/ASTWalker.h>
#include <libyul/YulString.h>
#include <map>
#include <set>
namespace dev
{
namespace yul
{
/**
* Optimisation stage that removes unused variables and functions.
*
* TODO: Also remove intermediate variable assignments from movable expressions
* which are not referenced until after the next assignment to the same variable.
*
* Note that this does not remove circular references.
*
* Prerequisite: Disambiguator
*/
class UnusedPruner: public ASTModifier
{
public:
explicit UnusedPruner(Block& _ast, std::set<YulString> const& _externallyUsedFunctions = {});
using ASTModifier::operator();
virtual void operator()(Block& _block) override;
// @returns true iff the code changed in the previous run.
bool shouldRunAgain() const { return m_shouldRunAgain; }
// Run the pruner until the code does not change anymore.
static void runUntilStabilised(Block& _ast, std::set<YulString> const& _externallyUsedFunctions = {});
private:
bool used(YulString _name) const;
void subtractReferences(std::map<YulString, size_t> const& _subtrahend);
bool m_shouldRunAgain = false;
std::map<YulString, size_t> m_references;
};
}
}
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