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returndatacopy and bugfix.

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This commit is contained in:
chriseth 2022-11-28 15:27:24 +01:00
parent b09a8c62bb
commit 1013419597
3 changed files with 34 additions and 34 deletions
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58
libyul/optimiser/UnusedStoreEliminator.cpp
View File

@ -78,12 +78,10 @@ void UnusedStoreEliminator::run(OptimiserStepContext& _context, Block& _ast)
ignoreMemory
};
rse(_ast);
if (
auto evmDialect = dynamic_cast<EVMDialect const*>(&_context.dialect);
evmDialect && evmDialect->providesObjectAccess()
)
{
}
auto evmDialect = dynamic_cast<EVMDialect const*>(&_context.dialect);
if (evmDialect && evmDialect->providesObjectAccess())
rse.clearActive(Location::Memory);
else
rse.markActiveAsUsed(Location::Memory);
rse.markActiveAsUsed(Location::Storage);
@ -168,25 +166,30 @@ void UnusedStoreEliminator::visit(Statement const& _statement)
yulAssert(isCandidateForRemoval == (isStorageWrite || (!m_ignoreMemory && isMemoryWrite)));
if (isCandidateForRemoval)
{
// TODO what is this special case?
//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;
// }
// }
if (*instruction == Instruction::RETURNDATACOPY)
{
// Out-of-bounds access to the returndata buffer results in a revert,
// so we are careful not to remove a potentially reverting call to a builtin.
// The only way the Solidity compiler uses `returndatacopy` is
// `returndatacopy(X, 0, returndatasize())`, so we only allow to remove this pattern
// (which is guaranteed to never cause an out-of-bounds revert).
bool allowReturndatacopyToBeRemoved = false;
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
)
allowReturndatacopyToBeRemoved = true;
}
if (!allowReturndatacopyToBeRemoved)
return;
}
m_allStores.insert(&_statement);
vector<Operation> operations = operationsFromFunctionCall(*funCall);
yulAssert(operations.size() == 1, "");
@ -198,11 +201,6 @@ void UnusedStoreEliminator::visit(Statement const& _statement)
}
}
void UnusedStoreEliminator::finalizeFunctionDefinition(FunctionDefinition const&)
{
markActiveAsUsed();
}
vector<UnusedStoreEliminator::Operation> UnusedStoreEliminator::operationsFromFunctionCall(
FunctionCall const& _functionCall
) const

7
libyul/optimiser/UnusedStoreEliminator.h
View File

@ -98,14 +98,17 @@ public:
private:
std::set<Statement const*>& activeMemoryStores() { return m_activeStores["m"_yulstring]; }
std::set<Statement const*>& activeStorageStores() { return m_activeStores["m"_yulstring]; }
std::set<Statement const*>& activeStorageStores() { return m_activeStores["s"_yulstring]; }
void shortcutNestedLoop(ActiveStores const&) override
{
// We might only need to do this for newly introduced stores in the loop.
markActiveAsUsed();
}
void finalizeFunctionDefinition(FunctionDefinition const&) override;
void finalizeFunctionDefinition(FunctionDefinition const&) override
{
markActiveAsUsed();
}
std::vector<Operation> operationsFromFunctionCall(FunctionCall const& _functionCall) const;
void applyOperation(Operation const& _operation);

3
test/libyul/yulOptimizerTests/unusedStoreEliminator/covering_calldatacopy_fixed.yul
View File

@ -39,8 +39,7 @@
// }
// if calldataload(2)
// {
// let _17 := 7
// let _18 := 2
// mstore8(2, 7)
// calldatacopy(0, 0, 3)
// }
// if calldataload(3)