mirror of
https://github.com/ethereum/solidity
synced 2023-10-03 13:03:40 +00:00
131 lines
4.1 KiB
C++
131 lines
4.1 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 subsequent assignments to variable declarations
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* and assignments.
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*/
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#include <libyul/optimiser/SSATransform.h>
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#include <libyul/optimiser/NameCollector.h>
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#include <libyul/optimiser/NameDispenser.h>
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#include <libyul/AsmData.h>
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#include <libdevcore/CommonData.h>
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using namespace std;
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using namespace dev;
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using namespace langutil;
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using namespace yul;
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using namespace dev::solidity;
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void SSATransform::operator()(Identifier& _identifier)
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{
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if (m_currentVariableValues.count(_identifier.name))
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_identifier.name = m_currentVariableValues[_identifier.name];
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}
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void SSATransform::operator()(ForLoop& _for)
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{
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// This will clear the current value in case of a reassignment inside the
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// init part, although the new variable would still be in scope inside the whole loop.
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// This small inefficiency is fine if we move the pre part of all for loops out
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// of the for loop.
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(*this)(_for.pre);
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Assignments assignments;
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assignments(_for.body);
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assignments(_for.post);
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for (auto const& var: assignments.names())
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m_currentVariableValues.erase(var);
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visit(*_for.condition);
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(*this)(_for.body);
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(*this)(_for.post);
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}
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void SSATransform::operator()(Block& _block)
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{
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set<YulString> variablesToClearAtEnd;
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// Creates a new variable (and returns its declaration) with value _value
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// and replaces _value by a reference to that new variable.
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auto replaceByNew = [&](SourceLocation _loc, YulString _varName, YulString _type, shared_ptr<Expression>& _value) -> VariableDeclaration
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{
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YulString newName = m_nameDispenser.newName(_varName);
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m_currentVariableValues[_varName] = newName;
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variablesToClearAtEnd.emplace(_varName);
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shared_ptr<Expression> v = make_shared<Expression>(Identifier{_loc, newName});
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_value.swap(v);
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return VariableDeclaration{_loc, {TypedName{_loc, std::move(newName), std::move(_type)}}, std::move(v)};
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};
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iterateReplacing(
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_block.statements,
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[&](Statement& _s) -> boost::optional<vector<Statement>>
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{
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if (_s.type() == typeid(VariableDeclaration))
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{
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VariableDeclaration& varDecl = boost::get<VariableDeclaration>(_s);
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if (varDecl.value)
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visit(*varDecl.value);
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if (varDecl.variables.size() != 1 || !m_variablesToReplace.count(varDecl.variables.front().name))
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return {};
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// Replace "let a := v" by "let a_1 := v let a := v"
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VariableDeclaration newVarDecl = replaceByNew(
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varDecl.location,
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varDecl.variables.front().name,
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varDecl.variables.front().type,
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varDecl.value
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);
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return vector<Statement>{std::move(newVarDecl), std::move(varDecl)};
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}
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else if (_s.type() == typeid(Assignment))
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{
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Assignment& assignment = boost::get<Assignment>(_s);
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visit(*assignment.value);
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if (assignment.variableNames.size() != 1)
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return {};
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assertThrow(m_variablesToReplace.count(assignment.variableNames.front().name), OptimizerException, "");
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// Replace "a := v" by "let a_1 := v a := v"
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VariableDeclaration newVarDecl = replaceByNew(
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assignment.location,
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assignment.variableNames.front().name,
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{}, // TODO determine type
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assignment.value
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);
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return vector<Statement>{std::move(newVarDecl), std::move(assignment)};
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}
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else
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visit(_s);
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return {};
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}
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);
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for (auto const& var: variablesToClearAtEnd)
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m_currentVariableValues.erase(var);
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}
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void SSATransform::run(Block& _ast, NameDispenser& _nameDispenser)
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{
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Assignments assignments;
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assignments(_ast);
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SSATransform{_nameDispenser, assignments.names()}(_ast);
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}
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