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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
#pragma once
#include <libyul/optimiser/ASTWalker.h>
#include <libyul/optimiser/Semantics.h>
#include <libyul/optimiser/OptimiserStep.h>
namespace solidity::yul
{
/**
* Loop-invariant code motion.
*
* This optimization moves movable SSA variable declarations outside the loop.
*
* Only statements at the top level in a loop's body or post block are considered, i.e variable
* declarations inside conditional branches will not be moved out of the loop.
*
* Requirements:
* - The Disambiguator, ForLoopInitRewriter and FunctionHoister must be run upfront.
* - Expression splitter and SSA transform should be run upfront to obtain better result.
*/
class LoopInvariantCodeMotion: public ASTModifier
{
public:
static constexpr char const* name{"LoopInvariantCodeMotion"};
static void run(OptimiserStepContext& _context, Block& _ast);
void operator()(Block& _block) override;
private:
explicit LoopInvariantCodeMotion(
Dialect const& _dialect,
std::set<YulString> const& _ssaVariables,
std::map<YulString, SideEffects> const& _functionSideEffects,
bool _containsMSize
):
m_containsMSize(_containsMSize),
m_dialect(_dialect),
m_ssaVariables(_ssaVariables),
m_functionSideEffects(_functionSideEffects)
{ }
/// @returns true if the given variable declaration can be moved to in front of the loop.
bool canBePromoted(
VariableDeclaration const& _varDecl,
std::set<YulString> const& _varsDefinedInCurrentScope,
SideEffects const& _forLoopSideEffects
) const;
std::optional<std::vector<Statement>> rewriteLoop(ForLoop& _for);
bool m_containsMSize = true;
Dialect const& m_dialect;
std::set<YulString> const& m_ssaVariables;
std::map<YulString, SideEffects> const& m_functionSideEffects;
};
}