solidity/libyul/optimiser/Rematerialiser.cpp
2019-11-19 17:23:18 +01:00

113 lines
3.3 KiB
C++

/*(
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 replaces variables by their most recently assigned expressions.
*/
#include <libyul/optimiser/Rematerialiser.h>
#include <libyul/optimiser/Metrics.h>
#include <libyul/optimiser/ASTCopier.h>
#include <libyul/optimiser/NameCollector.h>
#include <libyul/Exceptions.h>
#include <libyul/AsmData.h>
using namespace std;
using namespace dev;
using namespace yul;
void Rematerialiser::run(Dialect const& _dialect, Block& _ast, set<YulString> _varsToAlwaysRematerialize)
{
Rematerialiser{_dialect, _ast, std::move(_varsToAlwaysRematerialize)}(_ast);
}
void Rematerialiser::run(
Dialect const& _dialect,
FunctionDefinition& _function,
set<YulString> _varsToAlwaysRematerialize
)
{
Rematerialiser{_dialect, _function, std::move(_varsToAlwaysRematerialize)}(_function);
}
Rematerialiser::Rematerialiser(
Dialect const& _dialect,
Block& _ast,
set<YulString> _varsToAlwaysRematerialize
):
DataFlowAnalyzer(_dialect),
m_referenceCounts(ReferencesCounter::countReferences(_ast)),
m_varsToAlwaysRematerialize(std::move(_varsToAlwaysRematerialize))
{
}
Rematerialiser::Rematerialiser(
Dialect const& _dialect,
FunctionDefinition& _function,
set<YulString> _varsToAlwaysRematerialize
):
DataFlowAnalyzer(_dialect),
m_referenceCounts(ReferencesCounter::countReferences(_function)),
m_varsToAlwaysRematerialize(std::move(_varsToAlwaysRematerialize))
{
}
void Rematerialiser::visit(Expression& _e)
{
if (holds_alternative<Identifier>(_e))
{
Identifier& identifier = std::get<Identifier>(_e);
YulString name = identifier.name;
if (m_value.count(name))
{
assertThrow(m_value.at(name), OptimizerException, "");
auto const& value = *m_value.at(name);
size_t refs = m_referenceCounts[name];
size_t cost = CodeCost::codeCost(m_dialect, value);
if (refs <= 1 || cost == 0 || (refs <= 5 && cost <= 1) || m_varsToAlwaysRematerialize.count(name))
{
assertThrow(m_referenceCounts[name] > 0, OptimizerException, "");
for (auto const& ref: m_references.forward[name])
assertThrow(inScope(ref), OptimizerException, "");
// update reference counts
m_referenceCounts[name]--;
for (auto const& ref: ReferencesCounter::countReferences(value))
m_referenceCounts[ref.first] += ref.second;
_e = (ASTCopier{}).translate(value);
}
}
}
DataFlowAnalyzer::visit(_e);
}
void LiteralRematerialiser::visit(Expression& _e)
{
if (holds_alternative<Identifier>(_e))
{
Identifier& identifier = std::get<Identifier>(_e);
YulString name = identifier.name;
if (m_value.count(name))
{
Expression const* value = m_value.at(name);
assertThrow(value, OptimizerException, "");
if (holds_alternative<Literal>(*value))
_e = *value;
}
}
DataFlowAnalyzer::visit(_e);
}