solidity/libyul/optimiser/DeadCodeEliminator.cpp

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/*
This file is part of solidity.
solidity is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
solidity is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with solidity. If not, see <http://www.gnu.org/licenses/>.
*/
/**
* Optimisation stage that removes unreachable code.
*/
#include <libyul/optimiser/DeadCodeEliminator.h>
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#include <libyul/optimiser/Semantics.h>
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#include <libyul/optimiser/OptimiserStep.h>
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#include <libyul/AsmData.h>
#include <libevmasm/SemanticInformation.h>
#include <libevmasm/AssemblyItem.h>
#include <algorithm>
using namespace std;
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using namespace solidity;
using namespace solidity::util;
using namespace solidity::yul;
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void DeadCodeEliminator::run(OptimiserStepContext& _context, Block& _ast)
{
DeadCodeEliminator{_context.dialect}(_ast);
}
void DeadCodeEliminator::operator()(ForLoop& _for)
{
yulAssert(_for.pre.statements.empty(), "DeadCodeEliminator needs ForLoopInitRewriter as a prerequisite.");
ASTModifier::operator()(_for);
}
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void DeadCodeEliminator::operator()(Block& _block)
{
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TerminationFinder::ControlFlow controlFlowChange;
size_t index;
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tie(controlFlowChange, index) = TerminationFinder{m_dialect}.firstUnconditionalControlFlowChange(_block.statements);
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// Erase everything after the terminating statement that is not a function definition.
if (controlFlowChange != TerminationFinder::ControlFlow::FlowOut && index != std::numeric_limits<size_t>::max())
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_block.statements.erase(
remove_if(
_block.statements.begin() + static_cast<ptrdiff_t>(index) + 1,
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_block.statements.end(),
[] (Statement const& _s) { return !holds_alternative<yul::FunctionDefinition>(_s); }
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),
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_block.statements.end()
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);
ASTModifier::operator()(_block);
}