mirror of
https://github.com/ethereum/solidity
synced 2023-10-03 13:03:40 +00:00
95 lines
2.7 KiB
C++
95 lines
2.7 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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* Optimiser component that turns complex expressions into multiple variable
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* declarations.
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*/
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#pragma once
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#include <libyul/AsmDataForward.h>
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#include <libyul/optimiser/ASTWalker.h>
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#include <libyul/optimiser/NameDispenser.h>
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#include <vector>
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namespace solidity::yul
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{
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struct Dialect;
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struct OptimiserStepContext;
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class TypeInfo;
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/**
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* Optimiser component that modifies an AST in place, turning complex
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* expressions into simple expressions and multiple variable declarations.
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*
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* Code of the form
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*
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* sstore(mul(x, 4), mload(y))
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*
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* is transformed into
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*
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* let a1 := mload(y)
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* let a2 := mul(x, 4)
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* sstore(a2, a1)
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*
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* The transformation is not applied to loop conditions, because the loop control flow
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* does not allow "outlining" the inner expressions in all cases.
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*
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* The final program should be in a form such that with the exception of a loop condition,
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* function calls can only appear in the right-hand side of a variable declaration,
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* assignments or expression statements and all arguments have to be constants or variables.
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*/
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class ExpressionSplitter: public ASTModifier
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{
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public:
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static constexpr char const* name{"ExpressionSplitter"};
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static void run(OptimiserStepContext&, Block& _ast);
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void operator()(FunctionCall&) override;
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void operator()(If&) override;
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void operator()(Switch&) override;
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void operator()(ForLoop&) override;
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void operator()(Block& _block) override;
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private:
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explicit ExpressionSplitter(
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Dialect const& _dialect,
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NameDispenser& _nameDispenser,
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TypeInfo& _typeInfo
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):
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m_dialect(_dialect),
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m_nameDispenser(_nameDispenser),
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m_typeInfo(_typeInfo)
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{ }
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/// Replaces the expression by a variable if it is a function call or functional
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/// instruction. The declaration of the variable is appended to m_statementsToPrefix.
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/// Recurses via visit().
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void outlineExpression(Expression& _expr);
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/// List of statements that should go in front of the currently visited AST element,
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/// at the statement level.
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std::vector<Statement> m_statementsToPrefix;
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Dialect const& m_dialect;
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NameDispenser& m_nameDispenser;
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TypeInfo& m_typeInfo;
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};
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}
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