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Make DataFlowAnalyzer aware of storage / memory slot after sload / mload.

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This commit is contained in:
chriseth
2020-07-01 13:45:25 +02:00
parent a1c33249f1
commit e0b1d8b9bd
11 changed files with 197 additions and 0 deletions
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libyul/optimiser/DataFlowAnalyzer.cpp
+37
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@@ -253,6 +253,21 @@ void DataFlowAnalyzer::handleAssignment(set<YulString> const& _variables, Expres
// assignment to slot contents denoted by "name"
m_memory.eraseValue(name);
}
if (_value && _variables.size() == 1)
{
YulString variable = *_variables.begin();
if (!movableChecker.referencedVariables().count(variable))
{
// This might erase additional knowledge about the slot.
// On the other hand, if we knew the value in the slot
// already, then the sload() / mload() would have been replaced by a variable anyway.
if (auto key = isSimpleLoad(evmasm::Instruction::MLOAD, *_value))
m_memory.set(*key, variable);
else if (auto key = isSimpleLoad(evmasm::Instruction::SLOAD, *_value))
m_storage.set(*key, variable);
}
}
}
void DataFlowAnalyzer::pushScope(bool _functionScope)
@@ -401,3 +416,25 @@ std::optional<pair<YulString, YulString>> DataFlowAnalyzer::isSimpleStore(
return {};
}
std::optional<YulString> DataFlowAnalyzer::isSimpleLoad(
evmasm::Instruction _load,
Expression const& _expression
) const
{
yulAssert(
_load == evmasm::Instruction::MLOAD ||
_load == evmasm::Instruction::SLOAD,
""
);
if (holds_alternative<FunctionCall>(_expression))
{
FunctionCall const& funCall = std::get<FunctionCall>(_expression);
if (EVMDialect const* dialect = dynamic_cast<EVMDialect const*>(&m_dialect))
if (auto const* builtin = dialect->builtin(funCall.functionName.name))
if (builtin->instruction == _load)
if (holds_alternative<Identifier>(funCall.arguments.at(0)))
return std::get<Identifier>(funCall.arguments.at(0)).name;
}
return {};
}