mirror of
https://github.com/ethereum/solidity
synced 2023-10-03 13:03:40 +00:00
128 lines
3.9 KiB
C++
128 lines
3.9 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 expressions known to be the current value of a variable
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* in scope by a reference to that variable.
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*/
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#include <libyul/optimiser/CommonSubexpressionEliminator.h>
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#include <libyul/optimiser/SyntacticalEquality.h>
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#include <libyul/optimiser/CallGraphGenerator.h>
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#include <libyul/optimiser/Semantics.h>
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#include <libyul/SideEffects.h>
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#include <libyul/Exceptions.h>
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#include <libyul/AST.h>
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#include <libyul/Dialect.h>
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#include <libyul/Utilities.h>
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using namespace std;
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using namespace solidity;
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using namespace solidity::yul;
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using namespace solidity::util;
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void CommonSubexpressionEliminator::run(OptimiserStepContext& _context, Block& _ast)
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{
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CommonSubexpressionEliminator cse{
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_context.dialect,
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SideEffectsPropagator::sideEffects(_context.dialect, CallGraphGenerator::callGraph(_ast))
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};
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cse(_ast);
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}
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CommonSubexpressionEliminator::CommonSubexpressionEliminator(
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Dialect const& _dialect,
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map<YulString, SideEffects> _functionSideEffects
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):
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DataFlowAnalyzer(_dialect, std::move(_functionSideEffects))
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{
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}
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void CommonSubexpressionEliminator::operator()(FunctionDefinition& _fun)
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{
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ScopedSaveAndRestore returnVariables(m_returnVariables, {});
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for (auto const& v: _fun.returnVariables)
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m_returnVariables.insert(v.name);
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DataFlowAnalyzer::operator()(_fun);
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}
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void CommonSubexpressionEliminator::visit(Expression& _e)
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{
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bool descend = true;
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// If this is a function call to a function that requires literal arguments,
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// do not try to simplify there.
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if (holds_alternative<FunctionCall>(_e))
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{
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FunctionCall& funCall = std::get<FunctionCall>(_e);
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if (BuiltinFunction const* builtin = m_dialect.builtin(funCall.functionName.name))
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{
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for (size_t i = funCall.arguments.size(); i > 0; i--)
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// We should not modify function arguments that have to be literals
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// Note that replacing the function call entirely is fine,
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// if the function call is movable.
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if (!builtin->literalArgument(i - 1))
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visit(funCall.arguments[i - 1]);
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descend = false;
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}
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}
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// We visit the inner expression first to first simplify inner expressions,
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// which hopefully allows more matches.
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// Note that the DataFlowAnalyzer itself only has code for visiting Statements,
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// so this basically invokes the AST walker directly and thus post-visiting
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// is also fine with regards to data flow analysis.
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if (descend)
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DataFlowAnalyzer::visit(_e);
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if (Identifier const* identifier = get_if<Identifier>(&_e))
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{
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YulString identifierName = identifier->name;
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if (m_value.count(identifierName))
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{
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assertThrow(m_value.at(identifierName).value, OptimizerException, "");
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if (Identifier const* value = get_if<Identifier>(m_value.at(identifierName).value))
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if (inScope(value->name))
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_e = Identifier{debugDataOf(_e), value->name};
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}
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}
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else
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{
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// TODO this search is rather inefficient.
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for (auto const& [variable, value]: m_value)
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{
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assertThrow(value.value, OptimizerException, "");
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// Prevent using the default value of return variables
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// instead of literal zeros.
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if (
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m_returnVariables.count(variable) &&
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holds_alternative<Literal>(*value.value) &&
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valueOfLiteral(get<Literal>(*value.value)) == 0
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)
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continue;
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if (SyntacticallyEqual{}(_e, *value.value) && inScope(variable))
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{
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_e = Identifier{debugDataOf(_e), variable};
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break;
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}
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}
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}
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}
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