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Do not remove potentially reverting returndatacopy cases.

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This commit is contained in:
Daniel Kirchner
2022-05-23 11:01:03 +02:00
committed by chriseth
parent 30335c13ff
commit 9fa907aac2
6 changed files with 73 additions and 1 deletions
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libyul/optimiser/UnusedStoreEliminator.cpp
+19 -1
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@@ -157,7 +157,25 @@ void UnusedStoreEliminator::visit(Statement const& _statement)
yulAssert(isCandidateForRemoval == (isStorageWrite || (!m_ignoreMemory && isMemoryWrite)));
if (isCandidateForRemoval)
{
m_stores[YulString{}].insert({&_statement, State::Undecided});
State initialState = State::Undecided;
if (*instruction == Instruction::RETURNDATACOPY)
{
initialState = State::Used;
auto startOffset = identifierNameIfSSA(funCall->arguments.at(1));
auto length = identifierNameIfSSA(funCall->arguments.at(2));
KnowledgeBase knowledge(m_dialect, [this](YulString _var) { return util::valueOrNullptr(m_ssaValues, _var); });
if (length && startOffset)
{
FunctionCall const* lengthCall = get_if<FunctionCall>(m_ssaValues.at(*length).value);
if (
knowledge.knownToBeZero(*startOffset) &&
lengthCall &&
toEVMInstruction(m_dialect, lengthCall->functionName.name) == Instruction::RETURNDATASIZE
)
initialState = State::Undecided;
}
}
m_stores[YulString{}].insert({&_statement, initialState});
vector<Operation> operations = operationsFromFunctionCall(*funCall);
yulAssert(operations.size() == 1, "");
m_storeOperations[&_statement] = move(operations.front());