mirror of
https://github.com/ethereum/solidity
synced 2023-10-03 13:03:40 +00:00
99 lines
3.1 KiB
C++
99 lines
3.1 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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* Base class to perform data flow analysis during AST walks.
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* Tracks assignments and is used as base class for both Rematerialiser and
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* Common Subexpression Eliminator.
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*/
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#pragma once
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#include <libyul/optimiser/ASTWalker.h>
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#include <libyul/YulString.h>
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#include <libyul/AsmData.h>
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#include <libdevcore/InvertibleMap.h>
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#include <map>
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#include <set>
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namespace yul
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{
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struct Dialect;
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/**
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* Base class to perform data flow analysis during AST walks.
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* Tracks assignments and is used as base class for both Rematerialiser and
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* Common Subexpression Eliminator.
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*
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* A special zero constant expression is used for the default value of variables.
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*
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* Prerequisite: Disambiguator, ForLoopInitRewriter.
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*/
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class DataFlowAnalyzer: public ASTModifier
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{
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public:
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explicit DataFlowAnalyzer(Dialect const& _dialect): m_dialect(_dialect) {}
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using ASTModifier::operator();
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void operator()(Assignment& _assignment) override;
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void operator()(VariableDeclaration& _varDecl) override;
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void operator()(If& _if) override;
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void operator()(Switch& _switch) override;
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void operator()(FunctionDefinition&) override;
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void operator()(ForLoop&) override;
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void operator()(Block& _block) override;
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protected:
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/// Registers the assignment.
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void handleAssignment(std::set<YulString> const& _names, Expression* _value);
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/// Creates a new inner scope.
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void pushScope(bool _functionScope);
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/// Removes the innermost scope and clears all variables in it.
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void popScope();
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/// Clears information about the values assigned to the given variables,
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/// for example at points where control flow is merged.
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void clearValues(std::set<YulString> _names);
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/// Returns true iff the variable is in scope.
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bool inScope(YulString _variableName) const;
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/// Current values of variables, always movable.
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std::map<YulString, Expression const*> m_value;
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/// m_references.forward[a].contains(b) <=> the current expression assigned to a references b
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/// m_references.backward[b].contains(a) <=> the current expression assigned to a references b
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InvertibleRelation<YulString> m_references;
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struct Scope
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{
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explicit Scope(bool _isFunction): isFunction(_isFunction) {}
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std::set<YulString> variables;
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bool isFunction;
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};
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/// Special expression whose address will be used in m_value.
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/// YulString does not need to be reset because DataFlowAnalyzer is short-lived.
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Expression const m_zero{Literal{{}, LiteralKind::Number, YulString{"0"}, {}}};
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/// List of scopes.
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std::vector<Scope> m_variableScopes;
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Dialect const& m_dialect;
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};
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}
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