mirror of
https://github.com/ethereum/solidity
synced 2023-10-03 13:03:40 +00:00
110 lines
3.0 KiB
C++
110 lines
3.0 KiB
C++
/*
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This file is part of solidity.
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solidity is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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solidity is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with solidity. If not, see <http://www.gnu.org/licenses/>.
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*/
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/**
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* Optimisation stage that replaces variables by their most recently assigned expressions.
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*/
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#pragma once
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#include <libyul/optimiser/DataFlowAnalyzer.h>
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#include <libyul/optimiser/OptimiserStep.h>
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namespace solidity::yul
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{
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/**
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* Optimisation stage that replaces variable references by those expressions
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* that are most recently assigned to the referenced variables,
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* but only if the expression is movable and one of the following holds:
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* - the variable is referenced exactly once (and definition-to-reference does not cross a loop boundary)
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* - the value is extremely cheap ("cost" of zero like ``caller()``)
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* - the variable is referenced at most 5 times and the value is rather cheap
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* ("cost" of at most 1 like a constant up to 0xff) and we are not in a loop
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*
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* Prerequisite: Disambiguator, ForLoopInitRewriter.
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*/
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class Rematerialiser: public DataFlowAnalyzer
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{
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public:
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static constexpr char const* name{"Rematerialiser"};
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static void run(
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OptimiserStepContext& _context,
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Block& _ast
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) { run(_context.dialect, _ast); }
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static void run(
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Dialect const& _dialect,
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Block& _ast,
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std::set<YulString> _varsToAlwaysRematerialize = {}
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);
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static void run(
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Dialect const& _dialect,
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FunctionDefinition& _function,
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std::set<YulString> _varsToAlwaysRematerialize = {}
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);
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protected:
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Rematerialiser(
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Dialect const& _dialect,
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Block& _ast,
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std::set<YulString> _varsToAlwaysRematerialize = {}
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);
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Rematerialiser(
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Dialect const& _dialect,
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FunctionDefinition& _function,
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std::set<YulString> _varsToAlwaysRematerialize = {}
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);
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using DataFlowAnalyzer::operator();
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using ASTModifier::visit;
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void visit(Expression& _e) override;
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std::map<YulString, size_t> m_referenceCounts;
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std::set<YulString> m_varsToAlwaysRematerialize;
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};
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/**
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* If a variable is referenced that is known to have a literal
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* value at that point, replace it by a literal.
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*
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* This is mostly used so that other components do not have to rely
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* on the data flow analyzer.
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*
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* Prerequisite: Disambiguator, ForLoopInitRewriter.
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*/
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class LiteralRematerialiser: public DataFlowAnalyzer
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{
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public:
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static constexpr char const* name{"LiteralRematerialiser"};
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static void run(
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OptimiserStepContext& _context,
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Block& _ast
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) { LiteralRematerialiser{_context.dialect}(_ast); }
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using ASTModifier::visit;
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void visit(Expression& _e) override;
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private:
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LiteralRematerialiser(Dialect const& _dialect):
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DataFlowAnalyzer(_dialect)
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{}
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};
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}
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