mirror of
https://github.com/ethereum/solidity
synced 2023-10-03 13:03:40 +00:00
116 lines
3.4 KiB
C++
116 lines
3.4 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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#include <libyul/optimiser/LoopInvariantCodeMotion.h>
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#include <libyul/optimiser/CallGraphGenerator.h>
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#include <libyul/optimiser/NameCollector.h>
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#include <libyul/optimiser/Semantics.h>
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#include <libyul/optimiser/SSAValueTracker.h>
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#include <libyul/AsmData.h>
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#include <libdevcore/CommonData.h>
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#include <utility>
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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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void LoopInvariantCodeMotion::run(OptimiserStepContext& _context, Block& _ast)
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{
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map<YulString, SideEffects> functionSideEffects =
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SideEffectsPropagator::sideEffects(_context.dialect, CallGraphGenerator::callGraph(_ast));
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set<YulString> ssaVars = SSAValueTracker::ssaVariables(_ast);
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LoopInvariantCodeMotion{_context.dialect, ssaVars, functionSideEffects}(_ast);
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}
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void LoopInvariantCodeMotion::operator()(Block& _block)
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{
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util::iterateReplacing(
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_block.statements,
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[&](Statement& _s) -> optional<vector<Statement>>
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{
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visit(_s);
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if (holds_alternative<ForLoop>(_s))
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return rewriteLoop(get<ForLoop>(_s));
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else
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return {};
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}
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);
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}
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bool LoopInvariantCodeMotion::canBePromoted(
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VariableDeclaration const& _varDecl,
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set<YulString> const& _varsDefinedInCurrentScope
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) const
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{
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// A declaration can be promoted iff
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// 1. Its LHS is a SSA variable
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// 2. Its RHS only references SSA variables declared outside of the current scope
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// 3. Its RHS is movable
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for (auto const& var: _varDecl.variables)
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if (!m_ssaVariables.count(var.name))
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return false;
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if (_varDecl.value)
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{
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for (auto const& ref: ReferencesCounter::countReferences(*_varDecl.value, ReferencesCounter::OnlyVariables))
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if (_varsDefinedInCurrentScope.count(ref.first) || !m_ssaVariables.count(ref.first))
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return false;
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if (!SideEffectsCollector{m_dialect, *_varDecl.value, &m_functionSideEffects}.movable())
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return false;
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}
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return true;
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}
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optional<vector<Statement>> LoopInvariantCodeMotion::rewriteLoop(ForLoop& _for)
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{
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assertThrow(_for.pre.statements.empty(), OptimizerException, "");
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vector<Statement> replacement;
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for (Block* block: {&_for.post, &_for.body})
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{
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set<YulString> varsDefinedInScope;
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util::iterateReplacing(
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block->statements,
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[&](Statement& _s) -> optional<vector<Statement>>
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{
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if (holds_alternative<VariableDeclaration>(_s))
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{
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VariableDeclaration const& varDecl = std::get<VariableDeclaration>(_s);
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if (canBePromoted(varDecl, varsDefinedInScope))
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{
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replacement.emplace_back(std::move(_s));
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// Do not add the variables declared here to varsDefinedInScope because we are moving them.
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return vector<Statement>{};
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}
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for (auto const& var: varDecl.variables)
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varsDefinedInScope.insert(var.name);
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}
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return {};
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}
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);
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}
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if (replacement.empty())
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return {};
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else
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{
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replacement.emplace_back(std::move(_for));
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return { std::move(replacement) };
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}
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}
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