mirror of
https://github.com/ethereum/solidity
synced 2023-10-03 13:03:40 +00:00
82 lines
1.8 KiB
C++
82 lines
1.8 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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#pragma once
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#include <libyul/optimiser/ASTWalker.h>
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namespace yul
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{
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class AssignmentCounter;
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/**
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* Reverses the SSA transformation.
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*
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* In particular, the SSA transform will rewrite
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*
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* a := E
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*
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* to
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*
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* let a_1 := E
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* a := a_1
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*
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* To undo this kind of transformation, the SSAReverser changes this back to
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*
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* a := E
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* let a_1 := a
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*
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* In the special case
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* let a := E
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* a := a
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*
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* the redundant assignment "a := a" is removed.
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*
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*
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* Secondly, the SSA transform will rewrite
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*
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* let a := E
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* to
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*
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* let a_1 := E
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* let a := a_1
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*
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* To undo this kind of transformation, the SSAReverser changes this back to
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*
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* let a := E
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* let a_1 := a
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*
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* After that the CSE can replace references of a_1 by references to a,
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* after which the unused pruner can remove the declaration of a_1.
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*
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* Prerequisites: Disambiguator
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*
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*/
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class SSAReverser: public ASTModifier
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{
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public:
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using ASTModifier::operator();
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void operator()(Block& _block) override;
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static void run(Block& _block);
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private:
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SSAReverser(AssignmentCounter const& _assignmentCounter): m_assignmentCounter(_assignmentCounter) {}
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AssignmentCounter const& m_assignmentCounter;
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};
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}
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