path: root/libjulia/backends/evm/EVMCodeTransform.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/>.
*/
/**
 * Common code generator for translating Julia / inline assembly to EVM and EVM1.5.
 */

#include <libjulia/backends/evm/EVMCodeTransform.h>

#include <libsolidity/inlineasm/AsmAnalysisInfo.h>
#include <libsolidity/inlineasm/AsmData.h>

#include <libsolidity/interface/Exceptions.h>

#include <boost/range/adaptor/reversed.hpp>

using namespace std;
using namespace dev;
using namespace dev::julia;
using namespace dev::solidity;
using namespace dev::solidity::assembly;

void CodeTransform::operator()(VariableDeclaration const& _varDecl)
{
    solAssert(m_scope, "");

    int const numVariables = _varDecl.variables.size();
    int height = m_assembly.stackHeight();
    if (_varDecl.value)
    {
        boost::apply_visitor(*this, *_varDecl.value);
        expectDeposit(numVariables, height);
    }
    else
    {
        int variablesLeft = numVariables;
        while (variablesLeft--)
            m_assembly.appendConstant(u256(0));
    }
    for (auto const& variable: _varDecl.variables)
    {
        auto& var = boost::get<Scope::Variable>(m_scope->identifiers.at(variable.name));
        m_context->variableStackHeights[&var] = height++;
    }
    checkStackHeight(&_varDecl);
}

void CodeTransform::operator()(Assignment const& _assignment)
{
    visitExpression(*_assignment.value);
    m_assembly.setSourceLocation(_assignment.location);
    generateAssignment(_assignment.variableName);
    checkStackHeight(&_assignment);
}

void CodeTransform::operator()(StackAssignment const& _assignment)
{
    m_assembly.setSourceLocation(_assignment.location);
    generateAssignment(_assignment.variableName);
    checkStackHeight(&_assignment);
}

void CodeTransform::operator()(Label const& _label)
{
    m_assembly.setSourceLocation(_label.location);
    solAssert(m_scope, "");
    solAssert(m_scope->identifiers.count(_label.name), "");
    Scope::Label& label = boost::get<Scope::Label>(m_scope->identifiers.at(_label.name));
    m_assembly.appendLabel(labelID(label));
    checkStackHeight(&_label);
}

void CodeTransform::operator()(FunctionCall const& _call)
{
    solAssert(m_scope, "");

    m_assembly.setSourceLocation(_call.location);
    EVMAssembly::LabelID returnLabel(-1); // only used for evm 1.0
    if (!m_evm15)
    {
        returnLabel = m_assembly.newLabelId();
        m_assembly.appendLabelReference(returnLabel);
        m_stackAdjustment++;
    }

    Scope::Function* function = nullptr;
    solAssert(m_scope->lookup(_call.functionName.name, Scope::NonconstVisitor(
        [=](Scope::Variable&) { solAssert(false, "Expected function name."); },
        [=](Scope::Label&) { solAssert(false, "Expected function name."); },
        [&](Scope::Function& _function) { function = &_function; }
    )), "Function name not found.");
    solAssert(function, "");
    solAssert(function->arguments.size() == _call.arguments.size(), "");
    for (auto const& arg: _call.arguments | boost::adaptors::reversed)
        visitExpression(arg);
    m_assembly.setSourceLocation(_call.location);
    if (m_evm15)
        m_assembly.appendJumpsub(functionEntryID(*function), function->arguments.size(), function->returns.size());
    else
    {
        m_assembly.appendJumpTo(functionEntryID(*function), function->returns.size() - function->arguments.size() - 1);
        m_assembly.appendLabel(returnLabel);
        m_stackAdjustment--;
    }
    checkStackHeight(&_call);
}

void CodeTransform::operator()(FunctionalInstruction const& _instruction)
{
    if (m_evm15 && (
        _instruction.instruction.instruction == solidity::Instruction::JUMP ||
        _instruction.instruction.instruction == solidity::Instruction::JUMPI
    ))
    {
        bool const isJumpI = _instruction.instruction.instruction == solidity::Instruction::JUMPI;
        if (isJumpI)
        {
            solAssert(_instruction.arguments.size() == 2, "");
            visitExpression(_instruction.arguments.at(1));
        }
        else
        {
            solAssert(_instruction.arguments.size() == 1, "");
        }
        m_assembly.setSourceLocation(_instruction.location);
        auto label = labelFromIdentifier(boost::get<assembly::Identifier>(_instruction.arguments.at(0)));
        if (isJumpI)
            m_assembly.appendJumpToIf(label);
        else
            m_assembly.appendJumpTo(label);
    }
    else
    {
        for (auto const& arg: _instruction.arguments | boost::adaptors::reversed)
            visitExpression(arg);
        (*this)(_instruction.instruction);
    }
    checkStackHeight(&_instruction);
}

void CodeTransform::operator()(assembly::Identifier const& _identifier)
{
    m_assembly.setSourceLocation(_identifier.location);
    // First search internals, then externals.
    solAssert(m_scope, "");
    if (m_scope->lookup(_identifier.name, Scope::NonconstVisitor(
        [=](Scope::Variable& _var)
        {
            if (int heightDiff = variableHeightDiff(_var, false))
                m_assembly.appendInstruction(solidity::dupInstruction(heightDiff));
            else
                // Store something to balance the stack
                m_assembly.appendConstant(u256(0));
        },
        [=](Scope::Label& _label)
        {
            m_assembly.appendLabelReference(labelID(_label));
        },
        [=](Scope::Function&)
        {
            solAssert(false, "Function not removed during desugaring.");
        }
    )))
    {
        return;
    }
    solAssert(
        m_identifierAccess.generateCode,
        "Identifier not found and no external access available."
    );
    m_identifierAccess.generateCode(_identifier, IdentifierContext::RValue, m_assembly);
    checkStackHeight(&_identifier);
}

void CodeTransform::operator()(assembly::Literal const& _literal)
{
    m_assembly.setSourceLocation(_literal.location);
    if (_literal.kind == assembly::LiteralKind::Number)
        m_assembly.appendConstant(u256(_literal.value));
    else if (_literal.kind == assembly::LiteralKind::Boolean)
    {
        if (_literal.value == "true")
            m_assembly.appendConstant(u256(1));
        else
            m_assembly.appendConstant(u256(0));
    }
    else
    {
        solAssert(_literal.value.size() <= 32, "");
        m_assembly.appendConstant(u256(h256(_literal.value, h256::FromBinary, h256::AlignLeft)));
    }
    checkStackHeight(&_literal);
}

void CodeTransform::operator()(assembly::Instruction const& _instruction)
{
    solAssert(!m_evm15 || _instruction.instruction != solidity::Instruction::JUMP, "Bare JUMP instruction used for EVM1.5");
    solAssert(!m_evm15 || _instruction.instruction != solidity::Instruction::JUMPI, "Bare JUMPI instruction used for EVM1.5");
    m_assembly.setSourceLocation(_instruction.location);
    m_assembly.appendInstruction(_instruction.instruction);
    checkStackHeight(&_instruction);
}

void CodeTransform::operator()(Switch const& _switch)
{
    //@TODO use JUMPV in EVM1.5?

    visitExpression(*_switch.expression);
    int expressionHeight = m_assembly.stackHeight();
    map<Case const*, AbstractAssembly::LabelID> caseBodies;
    AbstractAssembly::LabelID end = m_assembly.newLabelId();
    for (Case const& c: _switch.cases)
    {
        if (c.value)
        {
            (*this)(*c.value);
            m_assembly.setSourceLocation(c.location);
            AbstractAssembly::LabelID bodyLabel = m_assembly.newLabelId();
            caseBodies[&c] = bodyLabel;
            solAssert(m_assembly.stackHeight() == expressionHeight + 1, "");
            m_assembly.appendInstruction(solidity::dupInstruction(2));
            m_assembly.appendInstruction(solidity::Instruction::EQ);
            m_assembly.appendJumpToIf(bodyLabel);
        }
        else
            // default case
            (*this)(c.body);
    }
    m_assembly.setSourceLocation(_switch.location);
    m_assembly.appendJumpTo(end);

    size_t numCases = caseBodies.size();
    for (auto const& c: caseBodies)
    {
        m_assembly.setSourceLocation(c.first->location);
        m_assembly.appendLabel(c.second);
        (*this)(c.first->body);
        // Avoid useless "jump to next" for the last case.
        if (--numCases > 0)
        {
            m_assembly.setSourceLocation(c.first->location);
            m_assembly.appendJumpTo(end);
        }
    }

    m_assembly.setSourceLocation(_switch.location);
    m_assembly.appendLabel(end);
    m_assembly.appendInstruction(solidity::Instruction::POP);
    checkStackHeight(&_switch);
}

void CodeTransform::operator()(FunctionDefinition const& _function)
{
    solAssert(m_scope, "");
    solAssert(m_scope->identifiers.count(_function.name), "");
    Scope::Function& function = boost::get<Scope::Function>(m_scope->identifiers.at(_function.name));

    int const localStackAdjustment = m_evm15 ? 0 : 1;
    int height = localStackAdjustment;
    solAssert(m_info.scopes.at(&_function.body), "");
    Scope* varScope = m_info.scopes.at(m_info.virtualBlocks.at(&_function).get()).get();
    solAssert(varScope, "");
    for (auto const& v: _function.arguments | boost::adaptors::reversed)
    {
        auto& var = boost::get<Scope::Variable>(varScope->identifiers.at(v.name));
        m_context->variableStackHeights[&var] = height++;
    }

    m_assembly.setSourceLocation(_function.location);
    int stackHeightBefore = m_assembly.stackHeight();
    AbstractAssembly::LabelID afterFunction = m_assembly.newLabelId();

    if (m_evm15)
    {
        m_assembly.appendJumpTo(afterFunction, -stackHeightBefore);
        m_assembly.appendBeginsub(functionEntryID(function), _function.arguments.size());
    }
    else
    {
        m_assembly.appendJumpTo(afterFunction, -stackHeightBefore + height);
        m_assembly.appendLabel(functionEntryID(function));
    }
    m_stackAdjustment += localStackAdjustment;

    for (auto const& v: _function.returns)
    {
        auto& var = boost::get<Scope::Variable>(varScope->identifiers.at(v.name));
        m_context->variableStackHeights[&var] = height++;
        // Preset stack slots for return variables to zero.
        m_assembly.appendConstant(u256(0));
    }

    CodeTransform(m_assembly, m_info, m_julia, m_evm15, m_identifierAccess, localStackAdjustment, m_context)
        (_function.body);

    {
        // The stack layout here is:
        // <return label>? <arguments...> <return values...>
        // But we would like it to be:
        // <return values...> <return label>?
        // So we have to append some SWAP and POP instructions.

        // This vector holds the desired target positions of all stack slots and is
        // modified parallel to the actual stack.
        vector<int> stackLayout;
        if (!m_evm15)
            stackLayout.push_back(_function.returns.size()); // Move return label to the top
        stackLayout += vector<int>(_function.arguments.size(), -1); // discard all arguments
        for (size_t i = 0; i < _function.returns.size(); ++i)
            stackLayout.push_back(i); // Move return values down, but keep order.

        solAssert(stackLayout.size() <= 17, "Stack too deep");
        while (!stackLayout.empty() && stackLayout.back() != int(stackLayout.size() - 1))
            if (stackLayout.back() < 0)
            {
                m_assembly.appendInstruction(solidity::Instruction::POP);
                stackLayout.pop_back();
            }
            else
            {
                m_assembly.appendInstruction(swapInstruction(stackLayout.size() - stackLayout.back() - 1));
                swap(stackLayout[stackLayout.back()], stackLayout.back());
            }
        for (int i = 0; size_t(i) < stackLayout.size(); ++i)
            solAssert(i == stackLayout[i], "Error reshuffling stack.");
    }

    if (m_evm15)
        m_assembly.appendReturnsub(_function.returns.size(), stackHeightBefore);
    else
        m_assembly.appendJump(stackHeightBefore - _function.returns.size());
    m_stackAdjustment -= localStackAdjustment;
    m_assembly.appendLabel(afterFunction);
    checkStackHeight(&_function);
}

void CodeTransform::operator()(ForLoop const& _forLoop)
{
    Scope* originalScope = m_scope;
    // We start with visiting the block, but not finalizing it.
    m_scope = m_info.scopes.at(&_forLoop.pre).get();
    int stackStartHeight = m_assembly.stackHeight();

    visitStatements(_forLoop.pre.statements);

    // TODO: When we implement break and continue, the labels and the stack heights at that point
    // have to be stored in a stack.
    AbstractAssembly::LabelID loopStart = m_assembly.newLabelId();
    AbstractAssembly::LabelID loopEnd = m_assembly.newLabelId();
    AbstractAssembly::LabelID postPart = m_assembly.newLabelId();

    m_assembly.setSourceLocation(_forLoop.location);
    m_assembly.appendLabel(loopStart);

    visitExpression(*_forLoop.condition);
    m_assembly.setSourceLocation(_forLoop.location);
    m_assembly.appendInstruction(solidity::Instruction::ISZERO);
    m_assembly.appendJumpToIf(loopEnd);

    (*this)(_forLoop.body);

    m_assembly.setSourceLocation(_forLoop.location);
    m_assembly.appendLabel(postPart);

    (*this)(_forLoop.post);

    m_assembly.setSourceLocation(_forLoop.location);
    m_assembly.appendJumpTo(loopStart);
    m_assembly.appendLabel(loopEnd);

    finalizeBlock(_forLoop.pre, stackStartHeight);
    m_scope = originalScope;
}

void CodeTransform::operator()(Block const& _block)
{
    Scope* originalScope = m_scope;
    m_scope = m_info.scopes.at(&_block).get();

    int blockStartStackHeight = m_assembly.stackHeight();
    visitStatements(_block.statements);

    finalizeBlock(_block, blockStartStackHeight);
    m_scope = originalScope;
}

AbstractAssembly::LabelID CodeTransform::labelFromIdentifier(Identifier const& _identifier)
{
    AbstractAssembly::LabelID label = AbstractAssembly::LabelID(-1);
    if (!m_scope->lookup(_identifier.name, Scope::NonconstVisitor(
        [=](Scope::Variable&) { solAssert(false, "Expected label"); },
        [&](Scope::Label& _label)
        {
            label = labelID(_label);
        },
        [=](Scope::Function&) { solAssert(false, "Expected label"); }
    )))
    {
        solAssert(false, "Identifier not found.");
    }
    return label;
}

AbstractAssembly::LabelID CodeTransform::labelID(Scope::Label const& _label)
{
    if (!m_context->labelIDs.count(&_label))
        m_context->labelIDs[&_label] = m_assembly.newLabelId();
    return m_context->labelIDs[&_label];
}

AbstractAssembly::LabelID CodeTransform::functionEntryID(Scope::Function const& _function)
{
    if (!m_context->functionEntryIDs.count(&_function))
        m_context->functionEntryIDs[&_function] = m_assembly.newLabelId();
    return m_context->functionEntryIDs[&_function];
}

void CodeTransform::visitExpression(Statement const& _expression)
{
    int height = m_assembly.stackHeight();
    boost::apply_visitor(*this, _expression);
    expectDeposit(1, height);
}

void CodeTransform::visitStatements(vector<Statement> const& _statements)
{
    for (auto const& statement: _statements)
        boost::apply_visitor(*this, statement);
}

void CodeTransform::finalizeBlock(Block const& _block, int blockStartStackHeight)
{
    m_assembly.setSourceLocation(_block.location);

    // pop variables
    solAssert(m_info.scopes.at(&_block).get() == m_scope, "");
    for (size_t i = 0; i < m_scope->numberOfVariables(); ++i)
        m_assembly.appendInstruction(solidity::Instruction::POP);

    int deposit = m_assembly.stackHeight() - blockStartStackHeight;
    solAssert(deposit == 0, "Invalid stack height at end of block.");
    checkStackHeight(&_block);
}

void CodeTransform::generateAssignment(Identifier const& _variableName)
{
    solAssert(m_scope, "");
    auto var = m_scope->lookup(_variableName.name);
    if (var)
    {
        Scope::Variable const& _var = boost::get<Scope::Variable>(*var);
        if (int heightDiff = variableHeightDiff(_var, true))
            m_assembly.appendInstruction(solidity::swapInstruction(heightDiff - 1));
        m_assembly.appendInstruction(solidity::Instruction::POP);
    }
    else
    {
        solAssert(
            m_identifierAccess.generateCode,
            "Identifier not found and no external access available."
        );
        m_identifierAccess.generateCode(_variableName, IdentifierContext::LValue, m_assembly);
    }
}

int CodeTransform::variableHeightDiff(solidity::assembly::Scope::Variable const& _var, bool _forSwap)
{
    solAssert(m_context->variableStackHeights.count(&_var), "");
    int heightDiff = m_assembly.stackHeight() - m_context->variableStackHeights[&_var];
    if (heightDiff <= (_forSwap ? 1 : 0) || heightDiff > (_forSwap ? 17 : 16))
    {
        solUnimplemented(
            "Variable inaccessible, too deep inside stack (" + boost::lexical_cast<string>(heightDiff) + ")"
        );
        return 0;
    }
    else
        return heightDiff;
}

void CodeTransform::expectDeposit(int _deposit, int _oldHeight)
{
    solAssert(m_assembly.stackHeight() == _oldHeight + _deposit, "Invalid stack deposit.");
}

void CodeTransform::checkStackHeight(void const* _astElement)
{
    solAssert(m_info.stackHeightInfo.count(_astElement), "Stack height for AST element not found.");
    solAssert(
        m_info.stackHeightInfo.at(_astElement) == m_assembly.stackHeight() - m_stackAdjustment,
        "Stack height mismatch between analysis and code generation phase: Analysis: " +
        to_string(m_info.stackHeightInfo.at(_astElement)) +
        " code gen: " +
        to_string(m_assembly.stackHeight() - m_stackAdjustment)
    );
}