solidity/libyul/optimiser/SSAValueTracker.h

65 lines
2.0 KiB
C++

/*
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
/**
* Component that collects variables that are never assigned to and their
* initial values.
*/
#pragma once
#include <libyul/optimiser/ASTWalker.h>
#include <libyul/AsmData.h>
#include <map>
#include <set>
namespace solidity::yul
{
/**
* Class that walks the AST and stores the initial value of each variable
* that is never assigned to.
*
* A special zero constant expression is used for the default value of variables.
*
* Prerequisite: Disambiguator
*/
class SSAValueTracker: public ASTWalker
{
public:
using ASTWalker::operator();
void operator()(FunctionDefinition const& _funDef) override;
void operator()(VariableDeclaration const& _varDecl) override;
void operator()(Assignment const& _assignment) override;
std::map<YulString, Expression const*> const& values() const { return m_values; }
Expression const* value(YulString _name) const { return m_values.at(_name); }
static std::set<YulString> ssaVariables(Block const& _ast);
private:
void setValue(YulString _name, Expression const* _value);
/// Special expression whose address will be used in m_values.
/// YulString does not need to be reset because SSAValueTracker is short-lived.
Expression const m_zero{Literal{{}, LiteralKind::Number, YulString{"0"}, {}}};
std::map<YulString, Expression const*> m_values;
};
}