path: root/libsolidity/codegen/ExpressionCompiler.cpp

/*
    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/>.
*/
/**
 * @author Christian <c@ethdev.com>
 * @date 2014
 * Solidity AST to EVM bytecode compiler for expressions.
 */

#include <utility>
#include <numeric>
#include <boost/range/adaptor/reversed.hpp>
#include <boost/algorithm/string/replace.hpp>
#include <libdevcore/Common.h>
#include <libdevcore/SHA3.h>
#include <libsolidity/ast/AST.h>
#include <libsolidity/codegen/ExpressionCompiler.h>
#include <libsolidity/codegen/CompilerContext.h>
#include <libsolidity/codegen/CompilerUtils.h>
#include <libsolidity/codegen/LValue.h>
#include <libevmasm/GasMeter.h>

using namespace std;

namespace dev
{
namespace solidity
{

void ExpressionCompiler::compile(Expression const& _expression)
{
    _expression.accept(*this);
}

void ExpressionCompiler::appendStateVariableInitialization(VariableDeclaration const& _varDecl)
{
    if (!_varDecl.value())
        return;
    TypePointer type = _varDecl.value()->annotation().type;
    solAssert(!!type, "Type information not available.");
    CompilerContext::LocationSetter locationSetter(m_context, _varDecl);
    _varDecl.value()->accept(*this);

    if (_varDecl.annotation().type->dataStoredIn(DataLocation::Storage))
    {
        // reference type, only convert value to mobile type and do final conversion in storeValue.
        auto mt = type->mobileType();
        solAssert(mt, "");
        utils().convertType(*type, *mt);
        type = mt;
    }
    else
    {
        utils().convertType(*type, *_varDecl.annotation().type);
        type = _varDecl.annotation().type;
    }
    StorageItem(m_context, _varDecl).storeValue(*type, _varDecl.location(), true);
}

void ExpressionCompiler::appendConstStateVariableAccessor(VariableDeclaration const& _varDecl)
{
    solAssert(_varDecl.isConstant(), "");
    _varDecl.value()->accept(*this);
    utils().convertType(*_varDecl.value()->annotation().type, *_varDecl.annotation().type);

    // append return
    m_context << dupInstruction(_varDecl.annotation().type->sizeOnStack() + 1);
    m_context.appendJump(eth::AssemblyItem::JumpType::OutOfFunction);
}

void ExpressionCompiler::appendStateVariableAccessor(VariableDeclaration const& _varDecl)
{
    solAssert(!_varDecl.isConstant(), "");
    CompilerContext::LocationSetter locationSetter(m_context, _varDecl);
    FunctionType accessorType(_varDecl);

    TypePointers paramTypes = accessorType.parameterTypes();
    m_context.adjustStackOffset(1 + CompilerUtils::sizeOnStack(paramTypes));

    // retrieve the position of the variable
    auto const& location = m_context.storageLocationOfVariable(_varDecl);
    m_context << location.first << u256(location.second);

    TypePointer returnType = _varDecl.annotation().type;

    for (size_t i = 0; i < paramTypes.size(); ++i)
    {
        if (auto mappingType = dynamic_cast<MappingType const*>(returnType.get()))
        {
            solAssert(CompilerUtils::freeMemoryPointer >= 0x40, "");
            solUnimplementedAssert(
                !paramTypes[i]->isDynamicallySized(),
                "Accessors for mapping with dynamically-sized keys not yet implemented."
            );
            // pop offset
            m_context << Instruction::POP;
            // move storage offset to memory.
            utils().storeInMemory(32);
            // move key to memory.
            utils().copyToStackTop(paramTypes.size() - i, 1);
            utils().storeInMemory(0);
            m_context << u256(64) << u256(0) << Instruction::KECCAK256;
            // push offset
            m_context << u256(0);
            returnType = mappingType->valueType();
        }
        else if (auto arrayType = dynamic_cast<ArrayType const*>(returnType.get()))
        {
            // pop offset
            m_context << Instruction::POP;
            utils().copyToStackTop(paramTypes.size() - i + 1, 1);
            ArrayUtils(m_context).accessIndex(*arrayType);
            returnType = arrayType->baseType();
        }
        else
            solAssert(false, "Index access is allowed only for \"mapping\" and \"array\" types.");
    }
    // remove index arguments.
    if (paramTypes.size() == 1)
        m_context << Instruction::SWAP2 << Instruction::POP << Instruction::SWAP1;
    else if (paramTypes.size() >= 2)
    {
        m_context << swapInstruction(paramTypes.size());
        m_context << Instruction::POP;
        m_context << swapInstruction(paramTypes.size());
        utils().popStackSlots(paramTypes.size() - 1);
    }
    unsigned retSizeOnStack = 0;
    solAssert(accessorType.returnParameterTypes().size() >= 1, "");
    auto const& returnTypes = accessorType.returnParameterTypes();
    if (StructType const* structType = dynamic_cast<StructType const*>(returnType.get()))
    {
        // remove offset
        m_context << Instruction::POP;
        auto const& names = accessorType.returnParameterNames();
        // struct
        for (size_t i = 0; i < names.size(); ++i)
        {
            if (returnTypes[i]->category() == Type::Category::Mapping)
                continue;
            if (auto arrayType = dynamic_cast<ArrayType const*>(returnTypes[i].get()))
                if (!arrayType->isByteArray())
                    continue;
            pair<u256, unsigned> const& offsets = structType->storageOffsetsOfMember(names[i]);
            m_context << Instruction::DUP1 << u256(offsets.first) << Instruction::ADD << u256(offsets.second);
            TypePointer memberType = structType->memberType(names[i]);
            StorageItem(m_context, *memberType).retrieveValue(SourceLocation(), true);
            utils().convertType(*memberType, *returnTypes[i]);
            utils().moveToStackTop(returnTypes[i]->sizeOnStack());
            retSizeOnStack += returnTypes[i]->sizeOnStack();
        }
        // remove slot
        m_context << Instruction::POP;
    }
    else
    {
        // simple value or array
        solAssert(returnTypes.size() == 1, "");
        StorageItem(m_context, *returnType).retrieveValue(SourceLocation(), true);
        utils().convertType(*returnType, *returnTypes.front());
        retSizeOnStack = returnTypes.front()->sizeOnStack();
    }
    solAssert(retSizeOnStack == utils().sizeOnStack(returnTypes), "");
    if (retSizeOnStack > 15)
        BOOST_THROW_EXCEPTION(
            CompilerError() <<
            errinfo_sourceLocation(_varDecl.location()) <<
            errinfo_comment("Stack too deep.")
        );
    m_context << dupInstruction(retSizeOnStack + 1);
    m_context.appendJump(eth::AssemblyItem::JumpType::OutOfFunction);
}

bool ExpressionCompiler::visit(Conditional const& _condition)
{
    CompilerContext::LocationSetter locationSetter(m_context, _condition);
    _condition.condition().accept(*this);
    eth::AssemblyItem trueTag = m_context.appendConditionalJump();
    _condition.falseExpression().accept(*this);
    utils().convertType(*_condition.falseExpression().annotation().type, *_condition.annotation().type);
    eth::AssemblyItem endTag = m_context.appendJumpToNew();
    m_context << trueTag;
    int offset = _condition.annotation().type->sizeOnStack();
    m_context.adjustStackOffset(-offset);
    _condition.trueExpression().accept(*this);
    utils().convertType(*_condition.trueExpression().annotation().type, *_condition.annotation().type);
    m_context << endTag;
    return false;
}

bool ExpressionCompiler::visit(Assignment const& _assignment)
{
    CompilerContext::LocationSetter locationSetter(m_context, _assignment);
    Token::Value op = _assignment.assignmentOperator();
    Token::Value binOp = op == Token::Assign ? op : Token::AssignmentToBinaryOp(op);
    Type const& leftType = *_assignment.leftHandSide().annotation().type;
    if (leftType.category() == Type::Category::Tuple)
    {
        solAssert(*_assignment.annotation().type == TupleType(), "");
        solAssert(op == Token::Assign, "");
    }
    else
        solAssert(*_assignment.annotation().type == leftType, "");
    bool cleanupNeeded = false;
    if (op != Token::Assign)
        cleanupNeeded = cleanupNeededForOp(leftType.category(), binOp);
    _assignment.rightHandSide().accept(*this);
    // Perform some conversion already. This will convert storage types to memory and literals
    // to their actual type, but will not convert e.g. memory to storage.
    TypePointer rightIntermediateType;
    if (op != Token::Assign && Token::isShiftOp(binOp))
        rightIntermediateType = _assignment.rightHandSide().annotation().type->mobileType();
    else
        rightIntermediateType = _assignment.rightHandSide().annotation().type->closestTemporaryType(
            _assignment.leftHandSide().annotation().type
        );
    solAssert(rightIntermediateType, "");
    utils().convertType(*_assignment.rightHandSide().annotation().type, *rightIntermediateType, cleanupNeeded);

    _assignment.leftHandSide().accept(*this);
    solAssert(!!m_currentLValue, "LValue not retrieved.");

    if (op == Token::Assign)
        m_currentLValue->storeValue(*rightIntermediateType, _assignment.location());
    else  // compound assignment
    {
        solAssert(leftType.isValueType(), "Compound operators only available for value types.");
        unsigned lvalueSize = m_currentLValue->sizeOnStack();
        unsigned itemSize = _assignment.annotation().type->sizeOnStack();
        if (lvalueSize > 0)
        {
            utils().copyToStackTop(lvalueSize + itemSize, itemSize);
            utils().copyToStackTop(itemSize + lvalueSize, lvalueSize);
            // value lvalue_ref value lvalue_ref
        }
        m_currentLValue->retrieveValue(_assignment.location(), true);
        utils().convertType(leftType, leftType, cleanupNeeded);

        if (Token::isShiftOp(binOp))
            appendShiftOperatorCode(binOp, leftType, *rightIntermediateType);
        else
        {
            solAssert(leftType == *rightIntermediateType, "");
            appendOrdinaryBinaryOperatorCode(binOp, leftType);
        }
        if (lvalueSize > 0)
        {
            if (itemSize + lvalueSize > 16)
                BOOST_THROW_EXCEPTION(
                    CompilerError() <<
                    errinfo_sourceLocation(_assignment.location()) <<
                    errinfo_comment("Stack too deep, try removing local variables.")
                );
            // value [lvalue_ref] updated_value
            for (unsigned i = 0; i < itemSize; ++i)
                m_context << swapInstruction(itemSize + lvalueSize) << Instruction::POP;
        }
        m_currentLValue->storeValue(*_assignment.annotation().type, _assignment.location());
    }
    m_currentLValue.reset();
    return false;
}

bool ExpressionCompiler::visit(TupleExpression const& _tuple)
{
    if (_tuple.isInlineArray())
    {
        ArrayType const& arrayType = dynamic_cast<ArrayType const&>(*_tuple.annotation().type);
        
        solAssert(!arrayType.isDynamicallySized(), "Cannot create dynamically sized inline array.");
        m_context << max(u256(32u), arrayType.memorySize());
        utils().allocateMemory();
        m_context << Instruction::DUP1;
    
        for (auto const& component: _tuple.components())
        {
            component->accept(*this);
            utils().convertType(*component->annotation().type, *arrayType.baseType(), true);
            utils().storeInMemoryDynamic(*arrayType.baseType(), true);              
        }
        
        m_context << Instruction::POP;
    }
    else
    {
        vector<unique_ptr<LValue>> lvalues;
        for (auto const& component: _tuple.components())
            if (component)
            {
                component->accept(*this);
                if (_tuple.annotation().lValueRequested)
                {
                    solAssert(!!m_currentLValue, "");
                    lvalues.push_back(move(m_currentLValue));
                }
            }
            else if (_tuple.annotation().lValueRequested)
                lvalues.push_back(unique_ptr<LValue>());
        if (_tuple.annotation().lValueRequested)
        {
            if (_tuple.components().size() == 1)
                m_currentLValue = move(lvalues[0]);
            else
                m_currentLValue.reset(new TupleObject(m_context, move(lvalues)));
        }
    }
    return false;
}

bool ExpressionCompiler::visit(UnaryOperation const& _unaryOperation)
{
    CompilerContext::LocationSetter locationSetter(m_context, _unaryOperation);
    if (_unaryOperation.annotation().type->category() == Type::Category::RationalNumber)
    {
        m_context << _unaryOperation.annotation().type->literalValue(nullptr);
        return false;
    }

    _unaryOperation.subExpression().accept(*this);

    switch (_unaryOperation.getOperator())
    {
    case Token::Not: // !
        m_context << Instruction::ISZERO;
        break;
    case Token::BitNot: // ~
        m_context << Instruction::NOT;
        break;
    case Token::Delete: // delete
        solAssert(!!m_currentLValue, "LValue not retrieved.");
        m_currentLValue->setToZero(_unaryOperation.location());
        m_currentLValue.reset();
        break;
    case Token::Inc: // ++ (pre- or postfix)
    case Token::Dec: // -- (pre- or postfix)
        solAssert(!!m_currentLValue, "LValue not retrieved.");
        m_currentLValue->retrieveValue(_unaryOperation.location());
        if (!_unaryOperation.isPrefixOperation())
        {
            // store value for later
            solUnimplementedAssert(_unaryOperation.annotation().type->sizeOnStack() == 1, "Stack size != 1 not implemented.");
            m_context << Instruction::DUP1;
            if (m_currentLValue->sizeOnStack() > 0)
                for (unsigned i = 1 + m_currentLValue->sizeOnStack(); i > 0; --i)
                    m_context << swapInstruction(i);
        }
        m_context << u256(1);
        if (_unaryOperation.getOperator() == Token::Inc)
            m_context << Instruction::ADD;
        else
            m_context << Instruction::SWAP1 << Instruction::SUB;
        // Stack for prefix: [ref...] (*ref)+-1
        // Stack for postfix: *ref [ref...] (*ref)+-1
        for (unsigned i = m_currentLValue->sizeOnStack(); i > 0; --i)
            m_context << swapInstruction(i);
        m_currentLValue->storeValue(
            *_unaryOperation.annotation().type, _unaryOperation.location(),
            !_unaryOperation.isPrefixOperation());
        m_currentLValue.reset();
        break;
    case Token::Add: // +
        // unary add, so basically no-op
        break;
    case Token::Sub: // -
        m_context << u256(0) << Instruction::SUB;
        break;
    default:
        solAssert(false, "Invalid unary operator: " + string(Token::toString(_unaryOperation.getOperator())));
    }
    return false;
}

bool ExpressionCompiler::visit(BinaryOperation const& _binaryOperation)
{
    CompilerContext::LocationSetter locationSetter(m_context, _binaryOperation);
    Expression const& leftExpression = _binaryOperation.leftExpression();
    Expression const& rightExpression = _binaryOperation.rightExpression();
    solAssert(!!_binaryOperation.annotation().commonType, "");
    TypePointer const& commonType = _binaryOperation.annotation().commonType;
    Token::Value const c_op = _binaryOperation.getOperator();

    if (c_op == Token::And || c_op == Token::Or) // special case: short-circuiting
        appendAndOrOperatorCode(_binaryOperation);
    else if (commonType->category() == Type::Category::RationalNumber)
        m_context << commonType->literalValue(nullptr);
    else
    {
        bool cleanupNeeded = cleanupNeededForOp(commonType->category(), c_op);

        TypePointer leftTargetType = commonType;
        TypePointer rightTargetType = Token::isShiftOp(c_op) ? rightExpression.annotation().type->mobileType() : commonType;
        solAssert(rightTargetType, "");

        // for commutative operators, push the literal as late as possible to allow improved optimization
        auto isLiteral = [](Expression const& _e)
        {
            return dynamic_cast<Literal const*>(&_e) || _e.annotation().type->category() == Type::Category::RationalNumber;
        };
        bool swap = m_optimize && Token::isCommutativeOp(c_op) && isLiteral(rightExpression) && !isLiteral(leftExpression);
        if (swap)
        {
            leftExpression.accept(*this);
            utils().convertType(*leftExpression.annotation().type, *leftTargetType, cleanupNeeded);
            rightExpression.accept(*this);
            utils().convertType(*rightExpression.annotation().type, *rightTargetType, cleanupNeeded);
        }
        else
        {
            rightExpression.accept(*this);
            utils().convertType(*rightExpression.annotation().type, *rightTargetType, cleanupNeeded);
            leftExpression.accept(*this);
            utils().convertType(*leftExpression.annotation().type, *leftTargetType, cleanupNeeded);
        }
        if (Token::isShiftOp(c_op))
            // shift only cares about the signedness of both sides
            appendShiftOperatorCode(c_op, *leftTargetType, *rightTargetType);
        else if (Token::isCompareOp(c_op))
            appendCompareOperatorCode(c_op, *commonType);
        else
            appendOrdinaryBinaryOperatorCode(c_op, *commonType);
    }

    // do not visit the child nodes, we already did that explicitly
    return false;
}

bool ExpressionCompiler::visit(FunctionCall const& _functionCall)
{
    CompilerContext::LocationSetter locationSetter(m_context, _functionCall);
    if (_functionCall.annotation().kind == FunctionCallKind::TypeConversion)
    {
        solAssert(_functionCall.arguments().size() == 1, "");
        solAssert(_functionCall.names().empty(), "");
        Expression const& firstArgument = *_functionCall.arguments().front();
        firstArgument.accept(*this);
        utils().convertType(*firstArgument.annotation().type, *_functionCall.annotation().type);
        return false;
    }

    FunctionTypePointer functionType;
    if (_functionCall.annotation().kind == FunctionCallKind::StructConstructorCall)
    {
        auto const& type = dynamic_cast<TypeType const&>(*_functionCall.expression().annotation().type);
        auto const& structType = dynamic_cast<StructType const&>(*type.actualType());
        functionType = structType.constructorType();
    }
    else
        functionType = dynamic_pointer_cast<FunctionType const>(_functionCall.expression().annotation().type);

    TypePointers parameterTypes = functionType->parameterTypes();
    vector<ASTPointer<Expression const>> const& callArguments = _functionCall.arguments();
    vector<ASTPointer<ASTString>> const& callArgumentNames = _functionCall.names();
    if (!functionType->takesArbitraryParameters())
        solAssert(callArguments.size() == parameterTypes.size(), "");

    vector<ASTPointer<Expression const>> arguments;
    if (callArgumentNames.empty())
        // normal arguments
        arguments = callArguments;
    else
        // named arguments
        for (auto const& parameterName: functionType->parameterNames())
        {
            bool found = false;
            for (size_t j = 0; j < callArgumentNames.size() && !found; j++)
                if ((found = (parameterName == *callArgumentNames[j])))
                    // we found the actual parameter position
                    arguments.push_back(callArguments[j]);
            solAssert(found, "");
        }

    if (_functionCall.annotation().kind == FunctionCallKind::StructConstructorCall)
    {
        TypeType const& type = dynamic_cast<TypeType const&>(*_functionCall.expression().annotation().type);
        auto const& structType = dynamic_cast<StructType const&>(*type.actualType());

        m_context << max(u256(32u), structType.memorySize());
        utils().allocateMemory();
        m_context << Instruction::DUP1;

        for (unsigned i = 0; i < arguments.size(); ++i)
        {
            arguments[i]->accept(*this);
            utils().convertType(*arguments[i]->annotation().type, *functionType->parameterTypes()[i]);
            utils().storeInMemoryDynamic(*functionType->parameterTypes()[i]);
        }
        m_context << Instruction::POP;
    }
    else
    {
        FunctionType const& function = *functionType;
        if (function.bound())
            // Only delegatecall and internal functions can be bound, this might be lifted later.
            solAssert(function.kind() == FunctionType::Kind::DelegateCall || function.kind() == FunctionType::Kind::Internal, "");
        switch (function.kind())
        {
        case FunctionType::Kind::Internal:
        {
            // Calling convention: Caller pushes return address and arguments
            // Callee removes them and pushes return values

            eth::AssemblyItem returnLabel = m_context.pushNewTag();
            for (unsigned i = 0; i < arguments.size(); ++i)
            {
                arguments[i]->accept(*this);
                utils().convertType(*arguments[i]->annotation().type, *function.parameterTypes()[i]);
            }
            _functionCall.expression().accept(*this);
            unsigned parameterSize = CompilerUtils::sizeOnStack(function.parameterTypes());
            if (function.bound())
            {
                // stack: arg2, ..., argn, label, arg1
                unsigned depth = parameterSize + 1;
                utils().moveIntoStack(depth, function.selfType()->sizeOnStack());
                parameterSize += function.selfType()->sizeOnStack();
            }

            if (m_context.runtimeContext())
                // We have a runtime context, so we need the creation part.
                utils().rightShiftNumberOnStack(32, false);
            else
                // Extract the runtime part.
                m_context << ((u256(1) << 32) - 1) << Instruction::AND;

            m_context.appendJump(eth::AssemblyItem::JumpType::IntoFunction);
            m_context << returnLabel;

            unsigned returnParametersSize = CompilerUtils::sizeOnStack(function.returnParameterTypes());
            // callee adds return parameters, but removes arguments and return label
            m_context.adjustStackOffset(returnParametersSize - parameterSize - 1);
            break;
        }
        case FunctionType::Kind::External:
        case FunctionType::Kind::CallCode:
        case FunctionType::Kind::DelegateCall:
        case FunctionType::Kind::BareCall:
        case FunctionType::Kind::BareCallCode:
        case FunctionType::Kind::BareDelegateCall:
            _functionCall.expression().accept(*this);
            appendExternalFunctionCall(function, arguments);
            break;
        case FunctionType::Kind::Creation:
        {
            _functionCall.expression().accept(*this);
            solAssert(!function.gasSet(), "Gas limit set for contract creation.");
            solAssert(function.returnParameterTypes().size() == 1, "");
            TypePointers argumentTypes;
            for (auto const& arg: arguments)
            {
                arg->accept(*this);
                argumentTypes.push_back(arg->annotation().type);
            }
            ContractDefinition const* contract =
                &dynamic_cast<ContractType const&>(*function.returnParameterTypes().front()).contractDefinition();
            m_context.callLowLevelFunction(
                "$copyContractCreationCodeToMemory_" + contract->type()->identifier(),
                0,
                1,
                [contract](CompilerContext& _context)
                {
                    // copy the contract's code into memory
                    eth::Assembly const& assembly = _context.compiledContract(*contract);
                    CompilerUtils(_context).fetchFreeMemoryPointer();
                    // pushes size
                    auto subroutine = _context.addSubroutine(make_shared<eth::Assembly>(assembly));
                    _context << Instruction::DUP1 << subroutine;
                    _context << Instruction::DUP4 << Instruction::CODECOPY;
                    _context << Instruction::ADD;
                }
            );
            utils().encodeToMemory(argumentTypes, function.parameterTypes());
            // now on stack: memory_end_ptr
            // need: size, offset, endowment
            utils().toSizeAfterFreeMemoryPointer();
            if (function.valueSet())
                m_context << dupInstruction(3);
            else
                m_context << u256(0);
            m_context << Instruction::CREATE;
            // Check if zero (out of stack or not enough balance).
            m_context << Instruction::DUP1 << Instruction::ISZERO;
            m_context.appendConditionalRevert();
            if (function.valueSet())
                m_context << swapInstruction(1) << Instruction::POP;
            break;
        }
        case FunctionType::Kind::SetGas:
        {
            // stack layout: contract_address function_id [gas] [value]
            _functionCall.expression().accept(*this);

            arguments.front()->accept(*this);
            utils().convertType(*arguments.front()->annotation().type, IntegerType(256), true);
            // Note that function is not the original function, but the ".gas" function.
            // Its values of gasSet and valueSet is equal to the original function's though.
            unsigned stackDepth = (function.gasSet() ? 1 : 0) + (function.valueSet() ? 1 : 0);
            if (stackDepth > 0)
                m_context << swapInstruction(stackDepth);
            if (function.gasSet())
                m_context << Instruction::POP;
            break;
        }
        case FunctionType::Kind::SetValue:
            // stack layout: contract_address function_id [gas] [value]
            _functionCall.expression().accept(*this);
            // Note that function is not the original function, but the ".value" function.
            // Its values of gasSet and valueSet is equal to the original function's though.
            if (function.valueSet())
                m_context << Instruction::POP;
            arguments.front()->accept(*this);
            break;
        case FunctionType::Kind::Send:
        case FunctionType::Kind::Transfer:
            _functionCall.expression().accept(*this);
            // Provide the gas stipend manually at first because we may send zero ether.
            // Will be zeroed if we send more than zero ether.
            m_context << u256(eth::GasCosts::callStipend);
            arguments.front()->accept(*this);
            utils().convertType(
                *arguments.front()->annotation().type,
                *function.parameterTypes().front(), true
            );
            // gas <- gas * !value
            m_context << Instruction::SWAP1 << Instruction::DUP2;
            m_context << Instruction::ISZERO << Instruction::MUL << Instruction::SWAP1;
            appendExternalFunctionCall(
                FunctionType(
                    TypePointers{},
                    TypePointers{},
                    strings(),
                    strings(),
                    FunctionType::Kind::BareCall,
                    false,
                    nullptr,
                    StateMutability::NonPayable,
                    true,
                    true
                ),
                {}
            );
            if (function.kind() == FunctionType::Kind::Transfer)
            {
                // Check if zero (out of stack or not enough balance).
                m_context << Instruction::ISZERO;
                m_context.appendConditionalRevert();
            }
            break;
        case FunctionType::Kind::Selfdestruct:
            arguments.front()->accept(*this);
            utils().convertType(*arguments.front()->annotation().type, *function.parameterTypes().front(), true);
            m_context << Instruction::SELFDESTRUCT;
            break;
        case FunctionType::Kind::Revert:
            m_context.appendRevert();
            break;
        case FunctionType::Kind::SHA3:
        {
            TypePointers argumentTypes;
            for (auto const& arg: arguments)
            {
                arg->accept(*this);
                argumentTypes.push_back(arg->annotation().type);
            }
            utils().fetchFreeMemoryPointer();
            utils().encodeToMemory(argumentTypes, TypePointers(), function.padArguments(), true);
            utils().toSizeAfterFreeMemoryPointer();
            m_context << Instruction::KECCAK256;
            break;
        }
        case FunctionType::Kind::Log0:
        case FunctionType::Kind::Log1:
        case FunctionType::Kind::Log2:
        case FunctionType::Kind::Log3:
        case FunctionType::Kind::Log4:
        {
            unsigned logNumber = int(function.kind()) - int(FunctionType::Kind::Log0);
            for (unsigned arg = logNumber; arg > 0; --arg)
            {
                arguments[arg]->accept(*this);
                utils().convertType(*arguments[arg]->annotation().type, *function.parameterTypes()[arg], true);
            }
            arguments.front()->accept(*this);
            utils().fetchFreeMemoryPointer();
            utils().encodeToMemory(
                {arguments.front()->annotation().type},
                {function.parameterTypes().front()},
                false,
                true);
            utils().toSizeAfterFreeMemoryPointer();
            m_context << logInstruction(logNumber);
            break;
        }
        case FunctionType::Kind::Event:
        {
            _functionCall.expression().accept(*this);
            auto const& event = dynamic_cast<EventDefinition const&>(function.declaration());
            unsigned numIndexed = 0;
            // All indexed arguments go to the stack
            for (unsigned arg = arguments.size(); arg > 0; --arg)
                if (event.parameters()[arg - 1]->isIndexed())
                {
                    ++numIndexed;
                    arguments[arg - 1]->accept(*this);
                    if (auto const& arrayType = dynamic_pointer_cast<ArrayType const>(function.parameterTypes()[arg - 1]))
                    {
                        utils().fetchFreeMemoryPointer();
                        utils().encodeToMemory(
                            {arguments[arg - 1]->annotation().type},
                            {arrayType},
                            false,
                            true
                        );
                        utils().toSizeAfterFreeMemoryPointer();
                        m_context << Instruction::KECCAK256;
                    }
                    else
                        utils().convertType(
                            *arguments[arg - 1]->annotation().type,
                            *function.parameterTypes()[arg - 1],
                            true
                        );
                }
            if (!event.isAnonymous())
            {
                m_context << u256(h256::Arith(dev::keccak256(function.externalSignature())));
                ++numIndexed;
            }
            solAssert(numIndexed <= 4, "Too many indexed arguments.");
            // Copy all non-indexed arguments to memory (data)
            // Memory position is only a hack and should be removed once we have free memory pointer.
            TypePointers nonIndexedArgTypes;
            TypePointers nonIndexedParamTypes;
            for (unsigned arg = 0; arg < arguments.size(); ++arg)
                if (!event.parameters()[arg]->isIndexed())
                {
                    arguments[arg]->accept(*this);
                    nonIndexedArgTypes.push_back(arguments[arg]->annotation().type);
                    nonIndexedParamTypes.push_back(function.parameterTypes()[arg]);
                }
            utils().fetchFreeMemoryPointer();
            utils().encodeToMemory(nonIndexedArgTypes, nonIndexedParamTypes);
            // need: topic1 ... topicn memsize memstart
            utils().toSizeAfterFreeMemoryPointer();
            m_context << logInstruction(numIndexed);
            break;
        }
        case FunctionType::Kind::BlockHash:
        {
            arguments[0]->accept(*this);
            utils().convertType(*arguments[0]->annotation().type, *function.parameterTypes()[0], true);
            m_context << Instruction::BLOCKHASH;
            break;
        }
        case FunctionType::Kind::AddMod:
        case FunctionType::Kind::MulMod:
        {
            for (unsigned i = 0; i < 3; i ++)
            {
                arguments[2 - i]->accept(*this);
                utils().convertType(*arguments[2 - i]->annotation().type, IntegerType(256));
            }
            if (function.kind() == FunctionType::Kind::AddMod)
                m_context << Instruction::ADDMOD;
            else
                m_context << Instruction::MULMOD;
            break;
        }
        case FunctionType::Kind::ECRecover:
        case FunctionType::Kind::SHA256:
        case FunctionType::Kind::RIPEMD160:
        {
            _functionCall.expression().accept(*this);
            static const map<FunctionType::Kind, u256> contractAddresses{{FunctionType::Kind::ECRecover, 1},
                                                               {FunctionType::Kind::SHA256, 2},
                                                               {FunctionType::Kind::RIPEMD160, 3}};
            m_context << contractAddresses.find(function.kind())->second;
            for (unsigned i = function.sizeOnStack(); i > 0; --i)
                m_context << swapInstruction(i);
            appendExternalFunctionCall(function, arguments);
            break;
        }
        case FunctionType::Kind::ByteArrayPush:
        case FunctionType::Kind::ArrayPush:
        {
            _functionCall.expression().accept(*this);
            solAssert(function.parameterTypes().size() == 1, "");
            solAssert(!!function.parameterTypes()[0], "");
            TypePointer paramType = function.parameterTypes()[0];
            shared_ptr<ArrayType> arrayType =
                function.kind() == FunctionType::Kind::ArrayPush ?
                make_shared<ArrayType>(DataLocation::Storage, paramType) :
                make_shared<ArrayType>(DataLocation::Storage);
            // get the current length
            ArrayUtils(m_context).retrieveLength(*arrayType);
            m_context << Instruction::DUP1;
            // stack: ArrayReference currentLength currentLength
            m_context << u256(1) << Instruction::ADD;
            // stack: ArrayReference currentLength newLength
            m_context << Instruction::DUP3 << Instruction::DUP2;
            ArrayUtils(m_context).resizeDynamicArray(*arrayType);
            m_context << Instruction::SWAP2 << Instruction::SWAP1;
            // stack: newLength ArrayReference oldLength
            ArrayUtils(m_context).accessIndex(*arrayType, false);

            // stack: newLength storageSlot slotOffset
            arguments[0]->accept(*this);
            // stack: newLength storageSlot slotOffset argValue
            TypePointer type = arguments[0]->annotation().type->closestTemporaryType(arrayType->baseType());
            solAssert(type, "");
            utils().convertType(*arguments[0]->annotation().type, *type);
            utils().moveToStackTop(1 + type->sizeOnStack());
            utils().moveToStackTop(1 + type->sizeOnStack());
            // stack: newLength argValue storageSlot slotOffset
            if (function.kind() == FunctionType::Kind::ArrayPush)
                StorageItem(m_context, *paramType).storeValue(*type, _functionCall.location(), true);
            else
                StorageByteArrayElement(m_context).storeValue(*type, _functionCall.location(), true);
            break;
        }
        case FunctionType::Kind::ObjectCreation:
        {
            // Will allocate at the end of memory (MSIZE) and not write at all unless the base
            // type is dynamically sized.
            ArrayType const& arrayType = dynamic_cast<ArrayType const&>(*_functionCall.annotation().type);
            _functionCall.expression().accept(*this);
            solAssert(arguments.size() == 1, "");

            // Fetch requested length.
            arguments[0]->accept(*this);
            utils().convertType(*arguments[0]->annotation().type, IntegerType(256));

            // Stack: requested_length
            // Allocate at max(MSIZE, freeMemoryPointer)
            utils().fetchFreeMemoryPointer();
            m_context << Instruction::DUP1 << Instruction::MSIZE;
            m_context << Instruction::LT;
            auto initialise = m_context.appendConditionalJump();
            // Free memory pointer does not point to empty memory, use MSIZE.
            m_context << Instruction::POP;
            m_context << Instruction::MSIZE;
            m_context << initialise;

            // Stack: requested_length memptr
            m_context << Instruction::SWAP1;
            // Stack: memptr requested_length
            // store length
            m_context << Instruction::DUP1 << Instruction::DUP3 << Instruction::MSTORE;
            // Stack: memptr requested_length
            // update free memory pointer
            m_context << Instruction::DUP1 << arrayType.baseType()->memoryHeadSize();
            m_context << Instruction::MUL << u256(32) << Instruction::ADD;
            m_context << Instruction::DUP3 << Instruction::ADD;
            utils().storeFreeMemoryPointer();
            // Stack: memptr requested_length

            // Check if length is zero
            m_context << Instruction::DUP1 << Instruction::ISZERO;
            auto skipInit = m_context.appendConditionalJump();

            // We only have to initialise if the base type is a not a value type.
            if (dynamic_cast<ReferenceType const*>(arrayType.baseType().get()))
            {
                m_context << Instruction::DUP2 << u256(32) << Instruction::ADD;
                utils().zeroInitialiseMemoryArray(arrayType);
            }
            m_context << skipInit;
            m_context << Instruction::POP;
            break;
        }
        case FunctionType::Kind::Assert:
        case FunctionType::Kind::Require:
        {
            arguments.front()->accept(*this);
            utils().convertType(*arguments.front()->annotation().type, *function.parameterTypes().front(), false);
            // jump if condition was met
            m_context << Instruction::ISZERO << Instruction::ISZERO;
            auto success = m_context.appendConditionalJump();
            if (function.kind() == FunctionType::Kind::Assert)
                // condition was not met, flag an error
                m_context.appendInvalid();
            else
                m_context.appendRevert();
            // the success branch
            m_context << success;
            break;
        }
        default:
            solAssert(false, "Invalid function type.");
        }
    }
    return false;
}

bool ExpressionCompiler::visit(NewExpression const&)
{
    // code is created for the function call (CREATION) only
    return false;
}

bool ExpressionCompiler::visit(MemberAccess const& _memberAccess)
{
    CompilerContext::LocationSetter locationSetter(m_context, _memberAccess);
    // Check whether the member is a bound function.
    ASTString const& member = _memberAccess.memberName();
    if (auto funType = dynamic_cast<FunctionType const*>(_memberAccess.annotation().type.get()))
        if (funType->bound())
        {
            _memberAccess.expression().accept(*this);
            utils().convertType(
                *_memberAccess.expression().annotation().type,
                *funType->selfType(),
                true
            );
            if (funType->kind() == FunctionType::Kind::Internal)
            {
                FunctionDefinition const& funDef = dynamic_cast<decltype(funDef)>(funType->declaration());
                utils().pushCombinedFunctionEntryLabel(funDef);
                utils().moveIntoStack(funType->selfType()->sizeOnStack(), 1);
            }
            else
            {
                solAssert(funType->kind() == FunctionType::Kind::DelegateCall, "");
                auto contract = dynamic_cast<ContractDefinition const*>(funType->declaration().scope());
                solAssert(contract && contract->isLibrary(), "");
                m_context.appendLibraryAddress(contract->fullyQualifiedName());
                m_context << funType->externalIdentifier();
                utils().moveIntoStack(funType->selfType()->sizeOnStack(), 2);
            }
            return false;
        }

    // Special processing for TypeType because we do not want to visit the library itself
    // for internal functions, or enum/struct definitions.
    if (TypeType const* type = dynamic_cast<TypeType const*>(_memberAccess.expression().annotation().type.get()))
    {
        if (dynamic_cast<ContractType const*>(type->actualType().get()))
        {
            solAssert(_memberAccess.annotation().type, "_memberAccess has no type");
            if (auto funType = dynamic_cast<FunctionType const*>(_memberAccess.annotation().type.get()))
            {
                switch (funType->kind())
                {
                case FunctionType::Kind::Internal:
                    // We do not visit the expression here on purpose, because in the case of an
                    // internal library function call, this would push the library address forcing
                    // us to link against it although we actually do not need it.
                    if (auto const* function = dynamic_cast<FunctionDefinition const*>(_memberAccess.annotation().referencedDeclaration))
                        utils().pushCombinedFunctionEntryLabel(*function);
                    else
                        solAssert(false, "Function not found in member access");
                    break;
                case FunctionType::Kind::Event:
                    if (!dynamic_cast<EventDefinition const*>(_memberAccess.annotation().referencedDeclaration))
                        solAssert(false, "event not found");
                    // no-op, because the parent node will do the job
                    break;
                case FunctionType::Kind::External:
                case FunctionType::Kind::Creation:
                case FunctionType::Kind::DelegateCall:
                case FunctionType::Kind::CallCode:
                case FunctionType::Kind::Send:
                case FunctionType::Kind::BareCall:
                case FunctionType::Kind::BareCallCode:
                case FunctionType::Kind::BareDelegateCall:
                case FunctionType::Kind::Transfer:
                    _memberAccess.expression().accept(*this);
                    m_context << funType->externalIdentifier();
                    break;
                case FunctionType::Kind::Log0:
                case FunctionType::Kind::Log1:
                case FunctionType::Kind::Log2:
                case FunctionType::Kind::Log3:
                case FunctionType::Kind::Log4:
                case FunctionType::Kind::ECRecover:
                case FunctionType::Kind::SHA256:
                case FunctionType::Kind::RIPEMD160:
                default:
                    solAssert(false, "unsupported member function");
                }
            }
            else if (dynamic_cast<TypeType const*>(_memberAccess.annotation().type.get()))
            {
                // no-op
            }
            else if (auto variable = dynamic_cast<VariableDeclaration const*>(_memberAccess.annotation().referencedDeclaration))
                appendVariable(*variable, static_cast<Expression const&>(_memberAccess));
            else
                _memberAccess.expression().accept(*this);
        }
        else if (auto enumType = dynamic_cast<EnumType const*>(type->actualType().get()))
        {
            _memberAccess.expression().accept(*this);
            m_context << enumType->memberValue(_memberAccess.memberName());
        }
        else
            _memberAccess.expression().accept(*this);
        return false;
    }

    _memberAccess.expression().accept(*this);
    switch (_memberAccess.expression().annotation().type->category())
    {
    case Type::Category::Contract:
    {
        bool alsoSearchInteger = false;
        ContractType const& type = dynamic_cast<ContractType const&>(*_memberAccess.expression().annotation().type);
        if (type.isSuper())
        {
            solAssert(!!_memberAccess.annotation().referencedDeclaration, "Referenced declaration not resolved.");
            utils().pushCombinedFunctionEntryLabel(m_context.superFunction(
                dynamic_cast<FunctionDefinition const&>(*_memberAccess.annotation().referencedDeclaration),
                type.contractDefinition()
            ));
        }
        else
        {
            // ordinary contract type
            if (Declaration const* declaration = _memberAccess.annotation().referencedDeclaration)
            {
                u256 identifier;
                if (auto const* variable = dynamic_cast<VariableDeclaration const*>(declaration))
                    identifier = FunctionType(*variable).externalIdentifier();
                else if (auto const* function = dynamic_cast<FunctionDefinition const*>(declaration))
                    identifier = FunctionType(*function).externalIdentifier();
                else
                    solAssert(false, "Contract member is neither variable nor function.");
                utils().convertType(type, IntegerType(0, IntegerType::Modifier::Address), true);
                m_context << identifier;
            }
            else
                // not found in contract, search in members inherited from address
                alsoSearchInteger = true;
        }
        if (!alsoSearchInteger)
            break;
    }
    case Type::Category::Integer:
        if (member == "balance")
        {
            utils().convertType(
                *_memberAccess.expression().annotation().type,
                IntegerType(0, IntegerType::Modifier::Address),
                true
            );
            m_context << Instruction::BALANCE;
        }
        else if ((set<string>{"send", "transfer", "call", "callcode", "delegatecall"}).count(member))
            utils().convertType(
                *_memberAccess.expression().annotation().type,
                IntegerType(0, IntegerType::Modifier::Address),
                true
            );
        else
            solAssert(false, "Invalid member access to integer");
        break;
    case Type::Category::Function:
        solAssert(!!_memberAccess.expression().annotation().type->memberType(member),
                 "Invalid member access to function.");
        break;
    case Type::Category::Magic:
        // we can ignore the kind of magic and only look at the name of the member
        if (member == "coinbase")
            m_context << Instruction::COINBASE;
        else if (member == "timestamp")
            m_context << Instruction::TIMESTAMP;
        else if (member == "difficulty")
            m_context << Instruction::DIFFICULTY;
        else if (member == "number")
            m_context << Instruction::NUMBER;
        else if (member == "gaslimit")
            m_context << Instruction::GASLIMIT;
        else if (member == "sender")
            m_context << Instruction::CALLER;
        else if (member == "value")
            m_context << Instruction::CALLVALUE;
        else if (member == "origin")
            m_context << Instruction::ORIGIN;
        else if (member == "gas")
            m_context << Instruction::GAS;
        else if (member == "gasprice")
            m_context << Instruction::GASPRICE;
        else if (member == "data")
            m_context << u256(0) << Instruction::CALLDATASIZE;
        else if (member == "sig")
            m_context << u256(0) << Instruction::CALLDATALOAD
                << (u256(0xffffffff) << (256 - 32)) << Instruction::AND;
        else
            solAssert(false, "Unknown magic member.");
        break;
    case Type::Category::Struct:
    {
        StructType const& type = dynamic_cast<StructType const&>(*_memberAccess.expression().annotation().type);
        switch (type.location())
        {
        case DataLocation::Storage:
        {
            pair<u256, unsigned> const& offsets = type.storageOffsetsOfMember(member);
            m_context << offsets.first << Instruction::ADD << u256(offsets.second);
            setLValueToStorageItem(_memberAccess);
            break;
        }
        case DataLocation::Memory:
        {
            m_context << type.memoryOffsetOfMember(member) << Instruction::ADD;
            setLValue<MemoryItem>(_memberAccess, *_memberAccess.annotation().type);
            break;
        }
        default:
            solAssert(false, "Illegal data location for struct.");
        }
        break;
    }
    case Type::Category::Enum:
    {
        EnumType const& type = dynamic_cast<EnumType const&>(*_memberAccess.expression().annotation().type);
        m_context << type.memberValue(_memberAccess.memberName());
        break;
    }
    case Type::Category::Array:
    {
        auto const& type = dynamic_cast<ArrayType const&>(*_memberAccess.expression().annotation().type);
        if (member == "length")
        {
            if (!type.isDynamicallySized())
            {
                utils().popStackElement(type);
                m_context << type.length();
            }
            else
                switch (type.location())
                {
                case DataLocation::CallData:
                    m_context << Instruction::SWAP1 << Instruction::POP;
                    break;
                case DataLocation::Storage:
                    setLValue<StorageArrayLength>(_memberAccess, type);
                    break;
                case DataLocation::Memory:
                    m_context << Instruction::MLOAD;
                    break;
                }
        }
        else if (member == "push")
        {
            solAssert(
                type.isDynamicallySized() && type.location() == DataLocation::Storage,
                "Tried to use .push() on a non-dynamically sized array"
            );
        }
        else
            solAssert(false, "Illegal array member.");
        break;
    }
    case Type::Category::FixedBytes:
    {
        auto const& type = dynamic_cast<FixedBytesType const&>(*_memberAccess.expression().annotation().type);
        utils().popStackElement(type);
        if (member == "length")
            m_context << u256(type.numBytes());
        else
            solAssert(false, "Illegal fixed bytes member.");
        break;
    }
    default:
        solAssert(false, "Member access to unknown type.");
    }
    return false;
}

bool ExpressionCompiler::visit(IndexAccess const& _indexAccess)
{
    CompilerContext::LocationSetter locationSetter(m_context, _indexAccess);
    _indexAccess.baseExpression().accept(*this);

    Type const& baseType = *_indexAccess.baseExpression().annotation().type;

    if (baseType.category() == Type::Category::Mapping)
    {
        // stack: storage_base_ref
        TypePointer keyType = dynamic_cast<MappingType const&>(baseType).keyType();
        solAssert(_indexAccess.indexExpression(), "Index expression expected.");
        if (keyType->isDynamicallySized())
        {
            _indexAccess.indexExpression()->accept(*this);
            utils().fetchFreeMemoryPointer();
            // stack: base index mem
            // note: the following operations must not allocate memory!
            utils().encodeToMemory(
                TypePointers{_indexAccess.indexExpression()->annotation().type},
                TypePointers{keyType},
                false,
                true
            );
            m_context << Instruction::SWAP1;
            utils().storeInMemoryDynamic(IntegerType(256));
            utils().toSizeAfterFreeMemoryPointer();
        }
        else
        {
            m_context << u256(0); // memory position
            appendExpressionCopyToMemory(*keyType, *_indexAccess.indexExpression());
            m_context << Instruction::SWAP1;
            solAssert(CompilerUtils::freeMemoryPointer >= 0x40, "");
            utils().storeInMemoryDynamic(IntegerType(256));
            m_context << u256(0);
        }
        m_context << Instruction::KECCAK256;
        m_context << u256(0);
        setLValueToStorageItem(_indexAccess);
    }
    else if (baseType.category() == Type::Category::Array)
    {
        ArrayType const& arrayType = dynamic_cast<ArrayType const&>(baseType);
        solAssert(_indexAccess.indexExpression(), "Index expression expected.");

        _indexAccess.indexExpression()->accept(*this);
        utils().convertType(*_indexAccess.indexExpression()->annotation().type, IntegerType(256), true);
        // stack layout: <base_ref> [<length>] <index>
        ArrayUtils(m_context).accessIndex(arrayType);
        switch (arrayType.location())
        {
        case DataLocation::Storage:
            if (arrayType.isByteArray())
            {
                solAssert(!arrayType.isString(), "Index access to string is not allowed.");
                setLValue<StorageByteArrayElement>(_indexAccess);
            }
            else
                setLValueToStorageItem(_indexAccess);
            break;
        case DataLocation::Memory:
            setLValue<MemoryItem>(_indexAccess, *_indexAccess.annotation().type, !arrayType.isByteArray());
            break;
        case DataLocation::CallData:
            //@todo if we implement this, the value in calldata has to be added to the base offset
            solUnimplementedAssert(!arrayType.baseType()->isDynamicallySized(), "Nested arrays not yet implemented.");
            if (arrayType.baseType()->isValueType())
                CompilerUtils(m_context).loadFromMemoryDynamic(
                    *arrayType.baseType(),
                    true,
                    !arrayType.isByteArray(),
                    false
                );
            break;
        }
    }
    else if (baseType.category() == Type::Category::FixedBytes)
    {
        FixedBytesType const& fixedBytesType = dynamic_cast<FixedBytesType const&>(baseType);
        solAssert(_indexAccess.indexExpression(), "Index expression expected.");

        _indexAccess.indexExpression()->accept(*this);
        utils().convertType(*_indexAccess.indexExpression()->annotation().type, IntegerType(256), true);
        // stack layout: <value> <index>
        // check out-of-bounds access
        m_context << u256(fixedBytesType.numBytes());
        m_context << Instruction::DUP2 << Instruction::LT << Instruction::ISZERO;
        // out-of-bounds access throws exception
        m_context.appendConditionalInvalid();

        m_context << Instruction::BYTE;
        utils().leftShiftNumberOnStack(256 - 8);
    }
    else if (baseType.category() == Type::Category::TypeType)
    {
        solAssert(baseType.sizeOnStack() == 0, "");
        solAssert(_indexAccess.annotation().type->sizeOnStack() == 0, "");
        // no-op - this seems to be a lone array type (`structType[];`)
    }
    else
        solAssert(false, "Index access only allowed for mappings or arrays.");

    return false;
}

void ExpressionCompiler::endVisit(Identifier const& _identifier)
{
    CompilerContext::LocationSetter locationSetter(m_context, _identifier);
    Declaration const* declaration = _identifier.annotation().referencedDeclaration;
    if (MagicVariableDeclaration const* magicVar = dynamic_cast<MagicVariableDeclaration const*>(declaration))
    {
        switch (magicVar->type()->category())
        {
        case Type::Category::Contract:
            // "this" or "super"
            if (!dynamic_cast<ContractType const&>(*magicVar->type()).isSuper())
                m_context << Instruction::ADDRESS;
            break;
        case Type::Category::Integer:
            // "now"
            m_context << Instruction::TIMESTAMP;
            break;
        default:
            break;
        }
    }
    else if (FunctionDefinition const* functionDef = dynamic_cast<FunctionDefinition const*>(declaration))
        utils().pushCombinedFunctionEntryLabel(m_context.resolveVirtualFunction(*functionDef));
    else if (auto variable = dynamic_cast<VariableDeclaration const*>(declaration))
        appendVariable(*variable, static_cast<Expression const&>(_identifier));
    else if (auto contract = dynamic_cast<ContractDefinition const*>(declaration))
    {
        if (contract->isLibrary())
            m_context.appendLibraryAddress(contract->fullyQualifiedName());
    }
    else if (dynamic_cast<EventDefinition const*>(declaration))
    {
        // no-op
    }
    else if (dynamic_cast<EnumDefinition const*>(declaration))
    {
        // no-op
    }
    else if (dynamic_cast<StructDefinition const*>(declaration))
    {
        // no-op
    }
    else
    {
        solAssert(false, "Identifier type not expected in expression context.");
    }
}

void ExpressionCompiler::endVisit(Literal const& _literal)
{
    CompilerContext::LocationSetter locationSetter(m_context, _literal);
    TypePointer type = _literal.annotation().type;
    
    switch (type->category())
    {
    case Type::Category::RationalNumber:
    case Type::Category::Bool:
    case Type::Category::Integer:
        m_context << type->literalValue(&_literal);
        break;
    case Type::Category::StringLiteral:
        break; // will be done during conversion
    default:
        solUnimplemented("Only integer, boolean and string literals implemented for now.");
    }
}

void ExpressionCompiler::appendAndOrOperatorCode(BinaryOperation const& _binaryOperation)
{
    Token::Value const c_op = _binaryOperation.getOperator();
    solAssert(c_op == Token::Or || c_op == Token::And, "");

    _binaryOperation.leftExpression().accept(*this);
    m_context << Instruction::DUP1;
    if (c_op == Token::And)
        m_context << Instruction::ISZERO;
    eth::AssemblyItem endLabel = m_context.appendConditionalJump();
    m_context << Instruction::POP;
    _binaryOperation.rightExpression().accept(*this);
    m_context << endLabel;
}

void ExpressionCompiler::appendCompareOperatorCode(Token::Value _operator, Type const& _type)
{
    solAssert(_type.sizeOnStack() == 1, "Comparison of multi-slot types.");
    if (_operator == Token::Equal || _operator == Token::NotEqual)
    {
        if (FunctionType const* funType = dynamic_cast<decltype(funType)>(&_type))
        {
            if (funType->kind() == FunctionType::Kind::Internal)
            {
                // We have to remove the upper bits (construction time value) because they might
                // be "unknown" in one of the operands and not in the other.
                m_context << ((u256(1) << 32) - 1) << Instruction::AND;
                m_context << Instruction::SWAP1;
                m_context << ((u256(1) << 32) - 1) << Instruction::AND;
            }
        }
        m_context << Instruction::EQ;
        if (_operator == Token::NotEqual)
            m_context << Instruction::ISZERO;
    }
    else
    {
        bool isSigned = false;
        if (auto type = dynamic_cast<IntegerType const*>(&_type))
            isSigned = type->isSigned();

        switch (_operator)
        {
        case Token::GreaterThanOrEqual:
            m_context <<
                (isSigned ? Instruction::SLT : Instruction::LT) <<
                Instruction::ISZERO;
            break;
        case Token::LessThanOrEqual:
            m_context <<
                (isSigned ? Instruction::SGT : Instruction::GT) <<
                Instruction::ISZERO;
            break;
        case Token::GreaterThan:
            m_context << (isSigned ? Instruction::SGT : Instruction::GT);
            break;
        case Token::LessThan:
            m_context << (isSigned ? Instruction::SLT : Instruction::LT);
            break;
        default:
            solAssert(false, "Unknown comparison operator.");
        }
    }
}

void ExpressionCompiler::appendOrdinaryBinaryOperatorCode(Token::Value _operator, Type const& _type)
{
    if (Token::isArithmeticOp(_operator))
        appendArithmeticOperatorCode(_operator, _type);
    else if (Token::isBitOp(_operator))
        appendBitOperatorCode(_operator);
    else
        solAssert(false, "Unknown binary operator.");
}

void ExpressionCompiler::appendArithmeticOperatorCode(Token::Value _operator, Type const& _type)
{
    IntegerType const& type = dynamic_cast<IntegerType const&>(_type);
    bool const c_isSigned = type.isSigned();

    if (_type.category() == Type::Category::FixedPoint)
        solUnimplemented("Not yet implemented - FixedPointType.");

    switch (_operator)
    {
    case Token::Add:
        m_context << Instruction::ADD;
        break;
    case Token::Sub:
        m_context << Instruction::SUB;
        break;
    case Token::Mul:
        m_context << Instruction::MUL;
        break;
    case Token::Div:
    case Token::Mod:
    {
        // Test for division by zero
        m_context << Instruction::DUP2 << Instruction::ISZERO;
        m_context.appendConditionalInvalid();

        if (_operator == Token::Div)
            m_context << (c_isSigned ? Instruction::SDIV : Instruction::DIV);
        else
            m_context << (c_isSigned ? Instruction::SMOD : Instruction::MOD);
        break;
    }
    case Token::Exp:
        m_context << Instruction::EXP;
        break;
    default:
        solAssert(false, "Unknown arithmetic operator.");
    }
}

void ExpressionCompiler::appendBitOperatorCode(Token::Value _operator)
{
    switch (_operator)
    {
    case Token::BitOr:
        m_context << Instruction::OR;
        break;
    case Token::BitAnd:
        m_context << Instruction::AND;
        break;
    case Token::BitXor:
        m_context << Instruction::XOR;
        break;
    default:
        solAssert(false, "Unknown bit operator.");
    }
}

void ExpressionCompiler::appendShiftOperatorCode(Token::Value _operator, Type const& _valueType, Type const& _shiftAmountType)
{
    // stack: shift_amount value_to_shift

    bool c_valueSigned = false;
    if (auto valueType = dynamic_cast<IntegerType const*>(&_valueType))
        c_valueSigned = valueType->isSigned();
    else
        solAssert(dynamic_cast<FixedBytesType const*>(&_valueType), "Only integer and fixed bytes type supported for shifts.");

    // The amount can be a RationalNumberType too.
    bool c_amountSigned = false;
    if (auto amountType = dynamic_cast<RationalNumberType const*>(&_shiftAmountType))
    {
        // This should be handled by the type checker.
        solAssert(amountType->integerType(), "");
        solAssert(!amountType->integerType()->isSigned(), "");
    }
    else if (auto amountType = dynamic_cast<IntegerType const*>(&_shiftAmountType))
        c_amountSigned = amountType->isSigned();
    else
        solAssert(false, "Invalid shift amount type.");

    // shift by negative amount throws exception
    if (c_amountSigned)
    {
        m_context << u256(0) << Instruction::DUP3 << Instruction::SLT;
        m_context.appendConditionalInvalid();
    }

    switch (_operator)
    {
    case Token::SHL:
        m_context << Instruction::SWAP1 << u256(2) << Instruction::EXP << Instruction::MUL;
        break;
    case Token::SAR:
        m_context << Instruction::SWAP1 << u256(2) << Instruction::EXP << Instruction::SWAP1 << (c_valueSigned ? Instruction::SDIV : Instruction::DIV);
        break;
    case Token::SHR:
    default:
        solAssert(false, "Unknown shift operator.");
    }
}

void ExpressionCompiler::appendExternalFunctionCall(
    FunctionType const& _functionType,
    vector<ASTPointer<Expression const>> const& _arguments
)
{
    solAssert(
        _functionType.takesArbitraryParameters() ||
        _arguments.size() == _functionType.parameterTypes().size(), ""
    );

    // Assumed stack content here:
    // <stack top>
    // value [if _functionType.valueSet()]
    // gas [if _functionType.gasSet()]
    // self object [if bound - moved to top right away]
    // function identifier [unless bare]
    // contract address

    unsigned selfSize = _functionType.bound() ? _functionType.selfType()->sizeOnStack() : 0;
    unsigned gasValueSize = (_functionType.gasSet() ? 1 : 0) + (_functionType.valueSet() ? 1 : 0);
    unsigned contractStackPos = m_context.currentToBaseStackOffset(1 + gasValueSize + selfSize + (_functionType.isBareCall() ? 0 : 1));
    unsigned gasStackPos = m_context.currentToBaseStackOffset(gasValueSize);
    unsigned valueStackPos = m_context.currentToBaseStackOffset(1);

    // move self object to top
    if (_functionType.bound())
        utils().moveToStackTop(gasValueSize, _functionType.selfType()->sizeOnStack());

    auto funKind = _functionType.kind();
    bool returnSuccessCondition = funKind == FunctionType::Kind::BareCall || funKind == FunctionType::Kind::BareCallCode || funKind == FunctionType::Kind::BareDelegateCall;
    bool isCallCode = funKind == FunctionType::Kind::BareCallCode || funKind == FunctionType::Kind::CallCode;
    bool isDelegateCall = funKind == FunctionType::Kind::BareDelegateCall || funKind == FunctionType::Kind::DelegateCall;

    unsigned retSize = 0;
    if (returnSuccessCondition)
        retSize = 0; // return value actually is success condition
    else
        for (auto const& retType: _functionType.returnParameterTypes())
        {
            solAssert(!retType->isDynamicallySized(), "Unable to return dynamic type from external call.");
            retSize += retType->calldataEncodedSize();
        }

    // Evaluate arguments.
    TypePointers argumentTypes;
    TypePointers parameterTypes = _functionType.parameterTypes();
    bool manualFunctionId = false;
    if (
        (funKind == FunctionType::Kind::BareCall || funKind == FunctionType::Kind::BareCallCode || funKind == FunctionType::Kind::BareDelegateCall) &&
        !_arguments.empty()
    )
    {
        solAssert(_arguments.front()->annotation().type->mobileType(), "");
        manualFunctionId =
            _arguments.front()->annotation().type->mobileType()->calldataEncodedSize(false) ==
            CompilerUtils::dataStartOffset;
    }
    if (manualFunctionId)
    {
        // If we have a Bare* and the first type has exactly 4 bytes, use it as
        // function identifier.
        _arguments.front()->accept(*this);
        utils().convertType(
            *_arguments.front()->annotation().type,
            IntegerType(8 * CompilerUtils::dataStartOffset),
            true
        );
        for (unsigned i = 0; i < gasValueSize; ++i)
            m_context << swapInstruction(gasValueSize - i);
        gasStackPos++;
        valueStackPos++;
    }
    if (_functionType.bound())
    {
        argumentTypes.push_back(_functionType.selfType());
        parameterTypes.insert(parameterTypes.begin(), _functionType.selfType());
    }
    for (size_t i = manualFunctionId ? 1 : 0; i < _arguments.size(); ++i)
    {
        _arguments[i]->accept(*this);
        argumentTypes.push_back(_arguments[i]->annotation().type);
    }

    if (funKind == FunctionType::Kind::ECRecover)
    {
        // Clears 32 bytes of currently free memory and advances free memory pointer.
        // Output area will be "start of input area" - 32.
        // The reason is that a failing ECRecover cannot be detected, it will just return
        // zero bytes (which we cannot detect).
        solAssert(0 < retSize && retSize <= 32, "");
        utils().fetchFreeMemoryPointer();
        m_context << u256(0) << Instruction::DUP2 << Instruction::MSTORE;
        m_context << u256(32) << Instruction::ADD;
        utils().storeFreeMemoryPointer();
    }

    // Touch the end of the output area so that we do not pay for memory resize during the call
    // (which we would have to subtract from the gas left)
    // We could also just use MLOAD; POP right before the gas calculation, but the optimizer
    // would remove that, so we use MSTORE here.
    if (!_functionType.gasSet() && retSize > 0)
    {
        m_context << u256(0);
        utils().fetchFreeMemoryPointer();
        // This touches too much, but that way we save some rounding arithmetics
        m_context << u256(retSize) << Instruction::ADD << Instruction::MSTORE;
    }

    // Copy function identifier to memory.
    utils().fetchFreeMemoryPointer();
    if (!_functionType.isBareCall() || manualFunctionId)
    {
        m_context << dupInstruction(2 + gasValueSize + CompilerUtils::sizeOnStack(argumentTypes));
        utils().storeInMemoryDynamic(IntegerType(8 * CompilerUtils::dataStartOffset), false);
    }
    // If the function takes arbitrary parameters, copy dynamic length data in place.
    // Move arguments to memory, will not update the free memory pointer (but will update the memory
    // pointer on the stack).
    utils().encodeToMemory(
        argumentTypes,
        parameterTypes,
        _functionType.padArguments(),
        _functionType.takesArbitraryParameters(),
        isCallCode || isDelegateCall
    );

    // Stack now:
    // <stack top>
    // input_memory_end
    // value [if _functionType.valueSet()]
    // gas [if _functionType.gasSet()]
    // function identifier [unless bare]
    // contract address

    // Output data will replace input data, unless we have ECRecover (then, output
    // area will be 32 bytes just before input area).
    // put on stack: <size of output> <memory pos of output> <size of input> <memory pos of input>
    m_context << u256(retSize);
    utils().fetchFreeMemoryPointer(); // This is the start of input
    if (funKind == FunctionType::Kind::ECRecover)
    {
        // In this case, output is 32 bytes before input and has already been cleared.
        m_context << u256(32) << Instruction::DUP2 << Instruction::SUB << Instruction::SWAP1;
        // Here: <input end> <output size> <outpos> <input pos>
        m_context << Instruction::DUP1 << Instruction::DUP5 << Instruction::SUB;
        m_context << Instruction::SWAP1;
    }
    else
    {
        m_context << Instruction::DUP1 << Instruction::DUP4 << Instruction::SUB;
        m_context << Instruction::DUP2;
    }

    // CALL arguments: outSize, outOff, inSize, inOff (already present up to here)
    // [value,] addr, gas (stack top)
    if (isDelegateCall)
        solAssert(!_functionType.valueSet(), "Value set for delegatecall");
    else if (_functionType.valueSet())
        m_context << dupInstruction(m_context.baseToCurrentStackOffset(valueStackPos));
    else
        m_context << u256(0);
    m_context << dupInstruction(m_context.baseToCurrentStackOffset(contractStackPos));

    bool existenceChecked = false;
    // Check the the target contract exists (has code) for non-low-level calls.
    if (funKind == FunctionType::Kind::External || funKind == FunctionType::Kind::CallCode || funKind == FunctionType::Kind::DelegateCall)
    {
        m_context << Instruction::DUP1 << Instruction::EXTCODESIZE << Instruction::ISZERO;
        m_context.appendConditionalRevert();
        existenceChecked = true;
    }

    if (_functionType.gasSet())
        m_context << dupInstruction(m_context.baseToCurrentStackOffset(gasStackPos));
    else
    {
        // send all gas except the amount needed to execute "SUB" and "CALL"
        // @todo this retains too much gas for now, needs to be fine-tuned.
        u256 gasNeededByCaller = eth::GasCosts::callGas + 10;
        if (_functionType.valueSet())
            gasNeededByCaller += eth::GasCosts::callValueTransferGas;
        if (!existenceChecked)
            gasNeededByCaller += eth::GasCosts::callNewAccountGas; // we never know
        m_context << gasNeededByCaller << Instruction::GAS << Instruction::SUB;
    }
    if (isDelegateCall)
        m_context << Instruction::DELEGATECALL;
    else if (isCallCode)
        m_context << Instruction::CALLCODE;
    else
        m_context << Instruction::CALL;

    unsigned remainsSize =
        2 + // contract address, input_memory_end
        _functionType.valueSet() +
        _functionType.gasSet() +
        (!_functionType.isBareCall() || manualFunctionId);

    if (returnSuccessCondition)
        m_context << swapInstruction(remainsSize);
    else
    {
        //Propagate error condition (if CALL pushes 0 on stack).
        m_context << Instruction::ISZERO;
        m_context.appendConditionalRevert();
    }

    utils().popStackSlots(remainsSize);

    if (returnSuccessCondition)
    {
        // already there
    }
    else if (funKind == FunctionType::Kind::RIPEMD160)
    {
        // fix: built-in contract returns right-aligned data
        utils().fetchFreeMemoryPointer();
        utils().loadFromMemoryDynamic(IntegerType(160), false, true, false);
        utils().convertType(IntegerType(160), FixedBytesType(20));
    }
    else if (funKind == FunctionType::Kind::ECRecover)
    {
        // Output is 32 bytes before input / free mem pointer.
        // Failing ecrecover cannot be detected, so we clear output before the call.
        m_context << u256(32);
        utils().fetchFreeMemoryPointer();
        m_context << Instruction::SUB << Instruction::MLOAD;
    }
    else if (!_functionType.returnParameterTypes().empty())
    {
        utils().fetchFreeMemoryPointer();
        bool memoryNeeded = false;
        for (auto const& retType: _functionType.returnParameterTypes())
        {
            utils().loadFromMemoryDynamic(*retType, false, true, true);
            if (dynamic_cast<ReferenceType const*>(retType.get()))
                memoryNeeded = true;
        }
        if (memoryNeeded)
            utils().storeFreeMemoryPointer();
        else
            m_context << Instruction::POP;
    }
}

void ExpressionCompiler::appendExpressionCopyToMemory(Type const& _expectedType, Expression const& _expression)
{
    solUnimplementedAssert(_expectedType.isValueType(), "Not implemented for non-value types.");
    _expression.accept(*this);
    utils().convertType(*_expression.annotation().type, _expectedType, true);
    utils().storeInMemoryDynamic(_expectedType);
}

void ExpressionCompiler::appendVariable(VariableDeclaration const& _variable, Expression const& _expression)
{
    if (!_variable.isConstant())
        setLValueFromDeclaration(_variable, _expression);
    else
    {
        _variable.value()->accept(*this);
        utils().convertType(*_variable.value()->annotation().type, *_variable.annotation().type);
    }
}

void ExpressionCompiler::setLValueFromDeclaration(Declaration const& _declaration, Expression const& _expression)
{
    if (m_context.isLocalVariable(&_declaration))
        setLValue<StackVariable>(_expression, dynamic_cast<VariableDeclaration const&>(_declaration));
    else if (m_context.isStateVariable(&_declaration))
        setLValue<StorageItem>(_expression, dynamic_cast<VariableDeclaration const&>(_declaration));
    else
        BOOST_THROW_EXCEPTION(InternalCompilerError()
            << errinfo_sourceLocation(_expression.location())
            << errinfo_comment("Identifier type not supported or identifier not found."));
}

void ExpressionCompiler::setLValueToStorageItem(Expression const& _expression)
{
    setLValue<StorageItem>(_expression, *_expression.annotation().type);
}

bool ExpressionCompiler::cleanupNeededForOp(Type::Category _type, Token::Value _op)
{
    if (Token::isCompareOp(_op) || Token::isShiftOp(_op))
        return true;
    else if (_type == Type::Category::Integer && (_op == Token::Div || _op == Token::Mod))
        return true;
    else
        return false;
}

CompilerUtils ExpressionCompiler::utils()
{
    return CompilerUtils(m_context);
}

}
}