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Special case code generation for for loops.

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This commit is contained in:
Daniel Kirchner 2022-08-10 15:48:06 +02:00
parent 3677c7a3ba
commit e6015626cf
8 changed files with 97 additions and 5 deletions
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1
Changelog.md
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@ -4,6 +4,7 @@ Language Features:
Compiler Features:
* Code Generator: Remove redundant overflow checks in specific for loops.
Bugfixes:

65
libsolidity/analysis/PostTypeChecker.cpp
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@ -130,6 +130,17 @@ void PostTypeChecker::endVisit(ModifierInvocation const& _modifierInvocation)
callEndVisit(_modifierInvocation);
}
bool PostTypeChecker::visit(ForStatement const& _forStatement)
{
return callVisit(_forStatement);
}
void PostTypeChecker::endVisit(ForStatement const& _forStatement)
{
callEndVisit(_forStatement);
}
namespace
{
struct ConstStateVarCircularReferenceChecker: public PostTypeChecker::Checker
@ -422,6 +433,59 @@ struct ReservedErrorSelector: public PostTypeChecker::Checker
}
};
class LValueChecker: public ASTConstVisitor
{
public:
LValueChecker(Identifier const& _identifier): m_declaration(_identifier.annotation().referencedDeclaration) {}
bool willBeWrittenTo() const { return m_willBeWrittenTo; }
void endVisit(Identifier const& _identifier) override
{
if (
_identifier.annotation().referencedDeclaration == m_declaration &&
_identifier.annotation().willBeWrittenTo
)
m_willBeWrittenTo = true;
}
private:
Declaration const* m_declaration;
bool m_willBeWrittenTo = false;
};
struct SimpleCounterForLoopChecker: public PostTypeChecker::Checker
{
SimpleCounterForLoopChecker(ErrorReporter& _errorReporter): Checker(_errorReporter) {}
bool visit(ForStatement const& _forStatement) override
{
_forStatement.annotation().isSimpleCounterLoop = isSimpleCounterLoop(_forStatement);
return true;
}
bool isSimpleCounterLoop(ForStatement const& _forStatement) const
{
auto const* cond = dynamic_cast<BinaryOperation const*>(_forStatement.condition());
if (!cond || cond->getOperator() != Token::LessThan)
return false;
if (!_forStatement.loopExpression())
return false;
auto const* post = dynamic_cast<UnaryOperation const*>(&_forStatement.loopExpression()->expression());
if (!post || post->getOperator() != Token::Inc)
return false;
auto const* lhsIdentifier = dynamic_cast<Identifier const*>(&cond->leftExpression());
auto const* lhsType = dynamic_cast<IntegerType const*>(cond->leftExpression().annotation().type);
auto const *commonType = dynamic_cast<IntegerType const*>(cond->annotation().commonType);
if (lhsIdentifier && lhsType && commonType && *lhsType == *commonType)
{
LValueChecker lValueChecker{*lhsIdentifier};
_forStatement.body().accept(lValueChecker);
if (!lValueChecker.willBeWrittenTo())
return true;
}
return false;
}
};
}
@ -433,4 +497,5 @@ PostTypeChecker::PostTypeChecker(langutil::ErrorReporter& _errorReporter): m_err
m_checkers.push_back(make_shared<EventOutsideEmitErrorOutsideRevertChecker>(_errorReporter));
m_checkers.push_back(make_shared<NoVariablesInInterfaceChecker>(_errorReporter));
m_checkers.push_back(make_shared<ReservedErrorSelector>(_errorReporter));
m_checkers.push_back(make_shared<SimpleCounterForLoopChecker>(_errorReporter));
}

3
libsolidity/analysis/PostTypeChecker.h
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@ -97,6 +97,9 @@ private:
bool visit(ModifierInvocation const& _modifierInvocation) override;
void endVisit(ModifierInvocation const& _modifierInvocation) override;
bool visit(ForStatement const& _forStatement) override;
void endVisit(ForStatement const& _forStatement) override;
template <class T>
bool callVisit(T const& _node)
{

1
libsolidity/ast/ASTAnnotations.h
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@ -235,6 +235,7 @@ struct TryCatchClauseAnnotation: ASTAnnotation, ScopableAnnotation
struct ForStatementAnnotation: StatementAnnotation, ScopableAnnotation
{
util::SetOnce<bool> isSimpleCounterLoop;
};
struct ReturnAnnotation: StatementAnnotation

10
libsolidity/ast/ASTJsonExporter.cpp
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@ -710,12 +710,18 @@ bool ASTJsonExporter::visit(WhileStatement const& _node)
bool ASTJsonExporter::visit(ForStatement const& _node)
{
setJsonNode(_node, "ForStatement", {
std::vector<pair<string, Json::Value>> attributes = {
make_pair("initializationExpression", toJsonOrNull(_node.initializationExpression())),
make_pair("condition", toJsonOrNull(_node.condition())),
make_pair("loopExpression", toJsonOrNull(_node.loopExpression())),
make_pair("body", toJson(_node.body()))
});
};
if (_node.annotation().isSimpleCounterLoop.set())
attributes.emplace_back(make_pair("isSimpleCounterLoop", *_node.annotation().isSimpleCounterLoop));
setJsonNode(_node, "ForStatement", std::move(attributes));
return false;
}

6
libsolidity/codegen/ContractCompiler.cpp
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@ -1246,7 +1246,13 @@ bool ContractCompiler::visit(ForStatement const& _forStatement)
// for's loop expression if existing
if (_forStatement.loopExpression())
{
Arithmetic previousArithmetic = m_context.arithmetic();
if (*_forStatement.annotation().isSimpleCounterLoop)
m_context.setArithmetic(Arithmetic::Wrapping);
_forStatement.loopExpression()->accept(*this);
m_context.setArithmetic(previousArithmetic);
}
m_context.appendJumpTo(loopStart);

13
libsolidity/codegen/ir/IRGeneratorForStatements.cpp
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@ -618,7 +618,9 @@ bool IRGeneratorForStatements::visit(ForStatement const& _forStatement)
_forStatement.body(),
_forStatement.condition(),
_forStatement.initializationExpression(),
_forStatement.loopExpression()
_forStatement.loopExpression(),
false,
*_forStatement.annotation().isSimpleCounterLoop
);
return false;
@ -3139,7 +3141,8 @@ void IRGeneratorForStatements::generateLoop(
Expression const* _conditionExpression,
Statement const* _initExpression,
ExpressionStatement const* _loopExpression,
bool _isDoWhile
bool _isDoWhile,
bool _isSimpleCounterLoop
)
{
string firstRun;
@ -3156,7 +3159,13 @@ void IRGeneratorForStatements::generateLoop(
_initExpression->accept(*this);
appendCode() << "} 1 {\n";
if (_loopExpression)
{
Arithmetic previousArithmetic = m_context.arithmetic();
if (_isSimpleCounterLoop)
m_context.setArithmetic(Arithmetic::Wrapping);
_loopExpression->accept(*this);
m_context.setArithmetic(previousArithmetic);
}
appendCode() << "}\n";
appendCode() << "{\n";

3
libsolidity/codegen/ir/IRGeneratorForStatements.h
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@ -235,7 +235,8 @@ private:
Expression const* _conditionExpression,
Statement const* _initExpression = nullptr,
ExpressionStatement const* _loopExpression = nullptr,
bool _isDoWhile = false
bool _isDoWhile = false,
bool _isSimpleCounterLoop = false
);
static Type const& type(Expression const& _expression);