path: root/Compiler.cpp

/*
    This file is part of cpp-ethereum.

    cpp-ethereum 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.

    cpp-ethereum 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 cpp-ethereum.  If not, see <http://www.gnu.org/licenses/>.
*/
/**
 * @author Christian <c@ethdev.com>
 * @date 2014
 * Solidity compiler.
 */

#include <algorithm>
#include <libsolidity/AST.h>
#include <libsolidity/Compiler.h>
#include <libsolidity/ExpressionCompiler.h>

using namespace std;

namespace dev {
namespace solidity {

bytes Compiler::compile(ContractDefinition& _contract)
{
    Compiler compiler;
    compiler.compileContract(_contract);
    return compiler.m_context.getAssembledBytecode();
}

void Compiler::compileContract(ContractDefinition& _contract)
{
    m_context = CompilerContext(); // clear it just in case

    //@todo constructor
    //@todo register state variables

    for (ASTPointer<FunctionDefinition> const& function: _contract.getDefinedFunctions())
        m_context.addFunction(*function);

    appendFunctionSelector(_contract.getDefinedFunctions());
    for (ASTPointer<FunctionDefinition> const& function: _contract.getDefinedFunctions())
        function->accept(*this);

    packIntoContractCreator();
}

void Compiler::packIntoContractCreator()
{
    CompilerContext creatorContext;
    eth::AssemblyItem sub = creatorContext.addSubroutine(m_context.getAssembly());
    // stack contains sub size
    creatorContext << eth::Instruction::DUP1 << sub << u256(0) << eth::Instruction::CODECOPY;
    creatorContext << u256(0) << eth::Instruction::RETURN;
    swap(m_context, creatorContext);
}

void Compiler::appendFunctionSelector(vector<ASTPointer<FunctionDefinition>> const& _functions)
{
    // sort all public functions and store them together with a tag for their argument decoding section
    map<string, pair<FunctionDefinition const*, eth::AssemblyItem>> publicFunctions;
    for (ASTPointer<FunctionDefinition> const& f: _functions)
        if (f->isPublic())
            publicFunctions.insert(make_pair(f->getName(), make_pair(f.get(), m_context.newTag())));

    //@todo remove constructor

    if (publicFunctions.size() > 255)
        BOOST_THROW_EXCEPTION(CompilerError() << errinfo_comment("More than 255 public functions for contract."));

    //@todo check for calldatasize?
    // retrieve the first byte of the call data
    m_context << u256(0) << eth::Instruction::CALLDATALOAD << u256(0) << eth::Instruction::BYTE;
    // check that it is not too large
    m_context << eth::Instruction::DUP1 << u256(publicFunctions.size() - 1) << eth::Instruction::LT;
    eth::AssemblyItem returnTag = m_context.appendConditionalJump();

    // otherwise, jump inside jump table (each entry of the table has size 4)
    m_context << u256(4) << eth::Instruction::MUL;
    eth::AssemblyItem jumpTableStart = m_context.pushNewTag();
    m_context << eth::Instruction::ADD << eth::Instruction::JUMP;

    // jump table @todo it could be that the optimizer destroys this
    m_context << jumpTableStart;
    for (pair<string, pair<FunctionDefinition const*, eth::AssemblyItem>> const& f: publicFunctions)
        m_context.appendJumpTo(f.second.second) << eth::Instruction::JUMPDEST;

    m_context << returnTag << eth::Instruction::STOP;

    for (pair<string, pair<FunctionDefinition const*, eth::AssemblyItem>> const& f: publicFunctions)
    {
        FunctionDefinition const& function = *f.second.first;
        m_context << f.second.second;

        eth::AssemblyItem returnTag = m_context.pushNewTag();
        appendCalldataUnpacker(function);
        m_context.appendJumpTo(m_context.getFunctionEntryLabel(function));
        m_context << returnTag;

        appendReturnValuePacker(function);
    }
}

void Compiler::appendCalldataUnpacker(FunctionDefinition const& _function)
{
    // We do not check the calldata size, everything is zero-padded.
    unsigned dataOffset = 1;

    //@todo this can be done more efficiently, saving some CALLDATALOAD calls
    for (ASTPointer<VariableDeclaration> const& var: _function.getParameters())
    {
        unsigned const numBytes = var->getType()->getCalldataEncodedSize();
        if (numBytes == 0)
            BOOST_THROW_EXCEPTION(CompilerError()
                                  << errinfo_sourceLocation(var->getLocation())
                                  << errinfo_comment("Type not yet supported."));
        if (numBytes == 32)
            m_context << u256(dataOffset) << eth::Instruction::CALLDATALOAD;
        else
            m_context << (u256(1) << ((32 - numBytes) * 8)) << u256(dataOffset)
                      << eth::Instruction::CALLDATALOAD << eth::Instruction::DIV;
        dataOffset += numBytes;
    }
}

void Compiler::appendReturnValuePacker(FunctionDefinition const& _function)
{
    //@todo this can be also done more efficiently
    unsigned dataOffset = 0;
    vector<ASTPointer<VariableDeclaration>> const& parameters = _function.getReturnParameters();
    for (unsigned i = 0; i < parameters.size(); ++i)
    {
        unsigned numBytes = parameters[i]->getType()->getCalldataEncodedSize();
        if (numBytes == 0)
            BOOST_THROW_EXCEPTION(CompilerError()
                                  << errinfo_sourceLocation(parameters[i]->getLocation())
                                  << errinfo_comment("Type not yet supported."));
        m_context << eth::dupInstruction(parameters.size() - i);
        if (numBytes != 32)
            m_context << (u256(1) << ((32 - numBytes) * 8)) << eth::Instruction::MUL;
        m_context << u256(dataOffset) << eth::Instruction::MSTORE;
        dataOffset += numBytes;
    }
    // note that the stack is not cleaned up here
    m_context << u256(dataOffset) << u256(0) << eth::Instruction::RETURN;
}

bool Compiler::visit(FunctionDefinition& _function)
{
    //@todo to simplify this, the calling convention could by changed such that
    // caller puts: [retarg0] ... [retargm] [return address] [arg0] ... [argn]
    // although note that this reduces the size of the visible stack

    m_context.startNewFunction();
    m_returnTag = m_context.newTag();
    m_breakTags.clear();
    m_continueTags.clear();

    m_context << m_context.getFunctionEntryLabel(_function);

    // stack upon entry: [return address] [arg0] [arg1] ... [argn]
    // reserve additional slots: [retarg0] ... [retargm] [localvar0] ... [localvarp]

    unsigned const numArguments = _function.getParameters().size();
    unsigned const numReturnValues = _function.getReturnParameters().size();
    unsigned const numLocalVariables = _function.getLocalVariables().size();

    for (ASTPointer<VariableDeclaration> const& variable: _function.getParameters() + _function.getReturnParameters())
        m_context.addVariable(*variable);
    for (VariableDeclaration const* localVariable: _function.getLocalVariables())
        m_context.addVariable(*localVariable);
    m_context.initializeLocalVariables(numReturnValues + numLocalVariables);

    _function.getBody().accept(*this);

    m_context << m_returnTag;

    // Now we need to re-shuffle the stack. For this we keep a record of the stack layout
    // that shows the target positions of the elements, where "-1" denotes that this element needs
    // to be removed from the stack.
    // Note that the fact that the return arguments are of increasing index is vital for this
    // algorithm to work.

    vector<int> stackLayout;
    stackLayout.push_back(numReturnValues); // target of return address
    stackLayout += vector<int>(numArguments, -1); // discard all arguments
    for (unsigned i = 0; i < numReturnValues; ++i)
        stackLayout.push_back(i);
    stackLayout += vector<int>(numLocalVariables, -1);

    while (stackLayout.back() != int(stackLayout.size() - 1))
        if (stackLayout.back() < 0)
        {
            m_context << eth::Instruction::POP;
            stackLayout.pop_back();
        }
        else
        {
            m_context << eth::swapInstruction(stackLayout.size() - stackLayout.back() - 1);
            swap(stackLayout[stackLayout.back()], stackLayout.back());
        }
    //@todo assert that everything is in place now

    m_context << eth::Instruction::JUMP;

    return false;
}

bool Compiler::visit(IfStatement& _ifStatement)
{
    ExpressionCompiler::compileExpression(m_context, _ifStatement.getCondition());
    eth::AssemblyItem trueTag = m_context.appendConditionalJump();
    if (_ifStatement.getFalseStatement())
        _ifStatement.getFalseStatement()->accept(*this);
    eth::AssemblyItem endTag = m_context.appendJump();
    m_context << trueTag;
    _ifStatement.getTrueStatement().accept(*this);
    m_context << endTag;
    return false;
}

bool Compiler::visit(WhileStatement& _whileStatement)
{
    eth::AssemblyItem loopStart = m_context.newTag();
    eth::AssemblyItem loopEnd = m_context.newTag();
    m_continueTags.push_back(loopStart);
    m_breakTags.push_back(loopEnd);

    m_context << loopStart;
    ExpressionCompiler::compileExpression(m_context, _whileStatement.getCondition());
    m_context << eth::Instruction::ISZERO;
    m_context.appendConditionalJumpTo(loopEnd);

    _whileStatement.getBody().accept(*this);

    m_context.appendJumpTo(loopStart);
    m_context << loopEnd;

    m_continueTags.pop_back();
    m_breakTags.pop_back();
    return false;
}

bool Compiler::visit(Continue&)
{
    if (!m_continueTags.empty())
        m_context.appendJumpTo(m_continueTags.back());
    return false;
}

bool Compiler::visit(Break&)
{
    if (!m_breakTags.empty())
        m_context.appendJumpTo(m_breakTags.back());
    return false;
}

bool Compiler::visit(Return& _return)
{
    //@todo modifications are needed to make this work with functions returning multiple values
    if (Expression* expression = _return.getExpression())
    {
        ExpressionCompiler::compileExpression(m_context, *expression);
        VariableDeclaration const& firstVariable = *_return.getFunctionReturnParameters().getParameters().front();
        ExpressionCompiler::cleanHigherOrderBitsIfNeeded(*expression->getType(), *firstVariable.getType());
        int stackPosition = m_context.getStackPositionOfVariable(firstVariable);
        m_context << eth::swapInstruction(stackPosition) << eth::Instruction::POP;
    }
    m_context.appendJumpTo(m_returnTag);
    return false;
}

bool Compiler::visit(VariableDefinition& _variableDefinition)
{
    if (Expression* expression = _variableDefinition.getExpression())
    {
        ExpressionCompiler::compileExpression(m_context, *expression);
        ExpressionCompiler::cleanHigherOrderBitsIfNeeded(*expression->getType(),
                                                         *_variableDefinition.getDeclaration().getType());
        int stackPosition = m_context.getStackPositionOfVariable(_variableDefinition.getDeclaration());
        m_context << eth::swapInstruction(stackPosition) << eth::Instruction::POP;
    }
    return false;
}

bool Compiler::visit(ExpressionStatement& _expressionStatement)
{
    Expression& expression = _expressionStatement.getExpression();
    ExpressionCompiler::compileExpression(m_context, expression);
    if (expression.getType()->getCategory() != Type::Category::VOID)
        m_context << eth::Instruction::POP;
    return false;
}

}
}