path: root/libevmasm/Assembly.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/>.
*/
/** @file Assembly.cpp
 * @author Gav Wood <i@gavwood.com>
 * @date 2014
 */

#include "Assembly.h"

#include <libevmasm/CommonSubexpressionEliminator.h>
#include <libevmasm/ControlFlowGraph.h>
#include <libevmasm/PeepholeOptimiser.h>
#include <libevmasm/JumpdestRemover.h>
#include <libevmasm/BlockDeduplicator.h>
#include <libevmasm/ConstantOptimiser.h>
#include <libevmasm/GasMeter.h>

#include <fstream>
#include <json/json.h>

using namespace std;
using namespace dev;
using namespace dev::eth;

void Assembly::append(Assembly const& _a)
{
    auto newDeposit = m_deposit + _a.deposit();
    for (AssemblyItem i: _a.m_items)
    {
        switch (i.type())
        {
        case Tag:
        case PushTag:
            i.setData(i.data() + m_usedTags);
            break;
        case PushSub:
        case PushSubSize:
            i.setData(i.data() + m_subs.size());
            break;
        default:
            break;
        }
        append(i);
    }
    m_deposit = newDeposit;
    m_usedTags += _a.m_usedTags;
    // This does not transfer the names of named tags on purpose. The tags themselves are
    // transferred, but their names are only available inside the assembly.
    for (auto const& i: _a.m_data)
        m_data.insert(i);
    for (auto const& i: _a.m_strings)
        m_strings.insert(i);
    m_subs += _a.m_subs;
    for (auto const& lib: _a.m_libraries)
        m_libraries.insert(lib);
}

void Assembly::append(Assembly const& _a, int _deposit)
{
    assertThrow(_deposit <= _a.m_deposit, InvalidDeposit, "");

    append(_a);
    while (_deposit++ < _a.m_deposit)
        append(Instruction::POP);
}

AssemblyItem const& Assembly::append(AssemblyItem const& _i)
{
    assertThrow(m_deposit >= 0, AssemblyException, "Stack underflow.");
    m_deposit += _i.deposit();
    m_items.push_back(_i);
    if (m_items.back().location().isEmpty() && !m_currentSourceLocation.isEmpty())
        m_items.back().setLocation(m_currentSourceLocation);
    return back();
}

void Assembly::injectStart(AssemblyItem const& _i)
{
    m_items.insert(m_items.begin(), _i);
}

unsigned Assembly::bytesRequired(unsigned subTagSize) const
{
    for (unsigned tagSize = subTagSize; true; ++tagSize)
    {
        unsigned ret = 1;
        for (auto const& i: m_data)
            ret += i.second.size();

        for (AssemblyItem const& i: m_items)
            ret += i.bytesRequired(tagSize);
        if (dev::bytesRequired(ret) <= tagSize)
            return ret;
    }
}

namespace
{

string locationFromSources(StringMap const& _sourceCodes, SourceLocation const& _location)
{
    if (_location.isEmpty() || _sourceCodes.empty() || _location.start >= _location.end || _location.start < 0)
        return "";

    auto it = _sourceCodes.find(*_location.sourceName);
    if (it == _sourceCodes.end())
        return "";

    string const& source = it->second;
    if (size_t(_location.start) >= source.size())
        return "";

    string cut = source.substr(_location.start, _location.end - _location.start);
    auto newLinePos = cut.find_first_of("\n");
    if (newLinePos != string::npos)
        cut = cut.substr(0, newLinePos) + "...";

    return cut;
}

class Functionalizer
{
public:
    Functionalizer (ostream& _out, string const& _prefix, StringMap const& _sourceCodes):
        m_out(_out), m_prefix(_prefix), m_sourceCodes(_sourceCodes)
    {}

    void feed(AssemblyItem const& _item)
    {
        if (!_item.location().isEmpty() && _item.location() != m_location)
        {
            flush();
            m_location = _item.location();
            printLocation();
        }
        if (!(
            _item.canBeFunctional() &&
            _item.returnValues() <= 1 &&
            _item.arguments() <= int(m_pending.size())
        ))
        {
            flush();
            m_out << m_prefix << (_item.type() == Tag ? "" : "  ") << _item.toAssemblyText() << endl;
            return;
        }
        string expression = _item.toAssemblyText();
        if (_item.arguments() > 0)
        {
            expression += "(";
            for (int i = 0; i < _item.arguments(); ++i)
            {
                expression += m_pending.back();
                m_pending.pop_back();
                if (i + 1 < _item.arguments())
                    expression += ", ";
            }
            expression += ")";
        }

        m_pending.push_back(expression);
        if (_item.returnValues() != 1)
            flush();
    }

    void flush()
    {
        for (string const& expression: m_pending)
            m_out << m_prefix << "  " << expression << endl;
        m_pending.clear();
    }

    void printLocation()
    {
        if (!m_location.sourceName && m_location.isEmpty())
            return;
        m_out << m_prefix << "    /*";
        if (m_location.sourceName)
            m_out << " \"" + *m_location.sourceName + "\"";
        if (!m_location.isEmpty())
            m_out << ":" << to_string(m_location.start) + ":" + to_string(m_location.end);
        m_out << "  " << locationFromSources(m_sourceCodes, m_location);
        m_out << " */" << endl;
    }

private:
    strings m_pending;
    SourceLocation m_location;

    ostream& m_out;
    string const& m_prefix;
    StringMap const& m_sourceCodes;
};

}

void Assembly::assemblyStream(ostream& _out, string const& _prefix, StringMap const& _sourceCodes) const
{
    Functionalizer f(_out, _prefix, _sourceCodes);

    for (auto const& i: m_items)
        f.feed(i);
    f.flush();

    if (!m_data.empty() || !m_subs.empty())
    {
        _out << _prefix << "stop" << endl;
        for (auto const& i: m_data)
            if (u256(i.first) >= m_subs.size())
                _out << _prefix << "data_" << toHex(u256(i.first)) << " " << toHex(i.second) << endl;

        for (size_t i = 0; i < m_subs.size(); ++i)
        {
            _out << endl << _prefix << "sub_" << i << ": assembly {\n";
            m_subs[i]->assemblyStream(_out, _prefix + "    ", _sourceCodes);
            _out << _prefix << "}" << endl;
        }
    }

    if (m_auxiliaryData.size() > 0)
        _out << endl << _prefix << "auxdata: 0x" << toHex(m_auxiliaryData) << endl;
}

string Assembly::assemblyString(StringMap const& _sourceCodes) const
{
    ostringstream tmp;
    assemblyStream(tmp, "", _sourceCodes);
    return tmp.str();
}

Json::Value Assembly::createJsonValue(string _name, int _begin, int _end, string _value, string _jumpType)
{
    Json::Value value;
    value["name"] = _name;
    value["begin"] = _begin;
    value["end"] = _end;
    if (!_value.empty())
        value["value"] = _value;
    if (!_jumpType.empty())
        value["jumpType"] = _jumpType;
    return value;
}

string Assembly::toStringInHex(u256 _value)
{
    std::stringstream hexStr;
    hexStr << hex << _value;
    return hexStr.str();
}

Json::Value Assembly::assemblyJSON(StringMap const& _sourceCodes) const
{
    Json::Value root;

    Json::Value& collection = root[".code"] = Json::arrayValue;
    for (AssemblyItem const& i: m_items)
    {
        switch (i.type())
        {
        case Operation:
            collection.append(
                createJsonValue(instructionInfo(i.instruction()).name, i.location().start, i.location().end, i.getJumpTypeAsString()));
            break;
        case Push:
            collection.append(
                createJsonValue("PUSH", i.location().start, i.location().end, toStringInHex(i.data()), i.getJumpTypeAsString()));
            break;
        case PushString:
            collection.append(
                createJsonValue("PUSH tag", i.location().start, i.location().end, m_strings.at((h256)i.data())));
            break;
        case PushTag:
            if (i.data() == 0)
                collection.append(
                    createJsonValue("PUSH [ErrorTag]", i.location().start, i.location().end, ""));
            else
                collection.append(
                    createJsonValue("PUSH [tag]", i.location().start, i.location().end, dev::toString(i.data())));
            break;
        case PushSub:
            collection.append(
                createJsonValue("PUSH [$]", i.location().start, i.location().end, dev::toString(h256(i.data()))));
            break;
        case PushSubSize:
            collection.append(
                createJsonValue("PUSH #[$]", i.location().start, i.location().end, dev::toString(h256(i.data()))));
            break;
        case PushProgramSize:
            collection.append(
                createJsonValue("PUSHSIZE", i.location().start, i.location().end));
            break;
        case PushLibraryAddress:
            collection.append(
                createJsonValue("PUSHLIB", i.location().start, i.location().end, m_libraries.at(h256(i.data())))
            );
            break;
        case PushDeployTimeAddress:
            collection.append(
                createJsonValue("PUSHDEPLOYADDRESS", i.location().start, i.location().end)
            );
            break;
        case Tag:
            collection.append(
                createJsonValue("tag", i.location().start, i.location().end, dev::toString(i.data())));
            collection.append(
                createJsonValue("JUMPDEST", i.location().start, i.location().end));
            break;
        case PushData:
            collection.append(createJsonValue("PUSH data", i.location().start, i.location().end, toStringInHex(i.data())));
            break;
        default:
            BOOST_THROW_EXCEPTION(InvalidOpcode());
        }
    }

    if (!m_data.empty() || !m_subs.empty())
    {
        Json::Value& data = root[".data"] = Json::objectValue;
        for (auto const& i: m_data)
            if (u256(i.first) >= m_subs.size())
                data[toStringInHex((u256)i.first)] = toHex(i.second);

        for (size_t i = 0; i < m_subs.size(); ++i)
        {
            std::stringstream hexStr;
            hexStr << hex << i;
            data[hexStr.str()] = m_subs[i]->assemblyJSON(_sourceCodes);
        }
    }

    if (m_auxiliaryData.size() > 0)
        root[".auxdata"] = toHex(m_auxiliaryData);

    return root;
}

AssemblyItem Assembly::namedTag(string const& _name)
{
    assertThrow(!_name.empty(), AssemblyException, "Empty named tag.");
    if (!m_namedTags.count(_name))
        m_namedTags[_name] = size_t(newTag().data());
    return AssemblyItem(Tag, m_namedTags.at(_name));
}

AssemblyItem Assembly::newPushLibraryAddress(string const& _identifier)
{
    h256 h(dev::keccak256(_identifier));
    m_libraries[h] = _identifier;
    return AssemblyItem(PushLibraryAddress, h);
}

Assembly& Assembly::optimise(bool _enable, EVMVersion _evmVersion, bool _isCreation, size_t _runs)
{
    OptimiserSettings settings;
    settings.isCreation = _isCreation;
    settings.runJumpdestRemover = true;
    settings.runPeephole = true;
    if (_enable)
    {
        settings.runDeduplicate = true;
        settings.runCSE = true;
        settings.runConstantOptimiser = true;
    }
    settings.evmVersion = _evmVersion;
    settings.expectedExecutionsPerDeployment = _runs;
    optimise(settings);
    return *this;
}


Assembly& Assembly::optimise(OptimiserSettings const& _settings)
{
    optimiseInternal(_settings, {});
    return *this;
}

map<u256, u256> Assembly::optimiseInternal(
    OptimiserSettings const& _settings,
    std::set<size_t> const& _tagsReferencedFromOutside
)
{
    // Run optimisation for sub-assemblies.
    for (size_t subId = 0; subId < m_subs.size(); ++subId)
    {
        OptimiserSettings settings = _settings;
        // Disable creation mode for sub-assemblies.
        settings.isCreation = false;
        map<u256, u256> subTagReplacements = m_subs[subId]->optimiseInternal(
            settings,
            JumpdestRemover::referencedTags(m_items, subId)
        );
        // Apply the replacements (can be empty).
        BlockDeduplicator::applyTagReplacement(m_items, subTagReplacements, subId);
    }

    map<u256, u256> tagReplacements;
    // Iterate until no new optimisation possibilities are found.
    for (unsigned count = 1; count > 0;)
    {
        count = 0;

        if (_settings.runJumpdestRemover)
        {
            JumpdestRemover jumpdestOpt(m_items);
            if (jumpdestOpt.optimise(_tagsReferencedFromOutside))
                count++;
        }

        if (_settings.runPeephole)
        {
            PeepholeOptimiser peepOpt(m_items);
            while (peepOpt.optimise())
            {
                count++;
                assertThrow(count < 64000, OptimizerException, "Peephole optimizer seems to be stuck.");
            }
        }

        // This only modifies PushTags, we have to run again to actually remove code.
        if (_settings.runDeduplicate)
        {
            BlockDeduplicator dedup(m_items);
            if (dedup.deduplicate())
            {
                tagReplacements.insert(dedup.replacedTags().begin(), dedup.replacedTags().end());
                count++;
            }
        }

        if (_settings.runCSE)
        {
            // Control flow graph optimization has been here before but is disabled because it
            // assumes we only jump to tags that are pushed. This is not the case anymore with
            // function types that can be stored in storage.
            AssemblyItems optimisedItems;

            bool usesMSize = (find(m_items.begin(), m_items.end(), AssemblyItem(Instruction::MSIZE)) != m_items.end());

            auto iter = m_items.begin();
            while (iter != m_items.end())
            {
                KnownState emptyState;
                CommonSubexpressionEliminator eliminator(emptyState);
                auto orig = iter;
                iter = eliminator.feedItems(iter, m_items.end(), usesMSize);
                bool shouldReplace = false;
                AssemblyItems optimisedChunk;
                try
                {
                    optimisedChunk = eliminator.getOptimizedItems();
                    shouldReplace = (optimisedChunk.size() < size_t(iter - orig));
                }
                catch (StackTooDeepException const&)
                {
                    // This might happen if the opcode reconstruction is not as efficient
                    // as the hand-crafted code.
                }
                catch (ItemNotAvailableException const&)
                {
                    // This might happen if e.g. associativity and commutativity rules
                    // reorganise the expression tree, but not all leaves are available.
                }

                if (shouldReplace)
                {
                    count++;
                    optimisedItems += optimisedChunk;
                }
                else
                    copy(orig, iter, back_inserter(optimisedItems));
            }
            if (optimisedItems.size() < m_items.size())
            {
                m_items = move(optimisedItems);
                count++;
            }
        }
    }

    if (_settings.runConstantOptimiser)
        ConstantOptimisationMethod::optimiseConstants(
            _settings.isCreation,
            _settings.isCreation ? 1 : _settings.expectedExecutionsPerDeployment,
            _settings.evmVersion,
            *this,
            m_items
        );

    return tagReplacements;
}

LinkerObject const& Assembly::assemble() const
{
    if (!m_assembledObject.bytecode.empty())
        return m_assembledObject;

    size_t subTagSize = 1;
    for (auto const& sub: m_subs)
    {
        sub->assemble();
        for (size_t tagPos: sub->m_tagPositionsInBytecode)
            if (tagPos != size_t(-1) && tagPos > subTagSize)
                subTagSize = tagPos;
    }

    LinkerObject& ret = m_assembledObject;

    size_t bytesRequiredForCode = bytesRequired(subTagSize);
    m_tagPositionsInBytecode = vector<size_t>(m_usedTags, -1);
    map<size_t, pair<size_t, size_t>> tagRef;
    multimap<h256, unsigned> dataRef;
    multimap<size_t, size_t> subRef;
    vector<unsigned> sizeRef; ///< Pointers to code locations where the size of the program is inserted
    unsigned bytesPerTag = dev::bytesRequired(bytesRequiredForCode);
    byte tagPush = (byte)Instruction::PUSH1 - 1 + bytesPerTag;

    unsigned bytesRequiredIncludingData = bytesRequiredForCode + 1 + m_auxiliaryData.size();
    for (auto const& sub: m_subs)
        bytesRequiredIncludingData += sub->assemble().bytecode.size();

    unsigned bytesPerDataRef = dev::bytesRequired(bytesRequiredIncludingData);
    byte dataRefPush = (byte)Instruction::PUSH1 - 1 + bytesPerDataRef;
    ret.bytecode.reserve(bytesRequiredIncludingData);

    for (AssemblyItem const& i: m_items)
    {
        // store position of the invalid jump destination
        if (i.type() != Tag && m_tagPositionsInBytecode[0] == size_t(-1))
            m_tagPositionsInBytecode[0] = ret.bytecode.size();

        switch (i.type())
        {
        case Operation:
            ret.bytecode.push_back((byte)i.instruction());
            break;
        case PushString:
        {
            ret.bytecode.push_back((byte)Instruction::PUSH32);
            unsigned ii = 0;
            for (auto j: m_strings.at((h256)i.data()))
                if (++ii > 32)
                    break;
                else
                    ret.bytecode.push_back((byte)j);
            while (ii++ < 32)
                ret.bytecode.push_back(0);
            break;
        }
        case Push:
        {
            byte b = max<unsigned>(1, dev::bytesRequired(i.data()));
            ret.bytecode.push_back((byte)Instruction::PUSH1 - 1 + b);
            ret.bytecode.resize(ret.bytecode.size() + b);
            bytesRef byr(&ret.bytecode.back() + 1 - b, b);
            toBigEndian(i.data(), byr);
            break;
        }
        case PushTag:
        {
            ret.bytecode.push_back(tagPush);
            tagRef[ret.bytecode.size()] = i.splitForeignPushTag();
            ret.bytecode.resize(ret.bytecode.size() + bytesPerTag);
            break;
        }
        case PushData:
            ret.bytecode.push_back(dataRefPush);
            dataRef.insert(make_pair((h256)i.data(), ret.bytecode.size()));
            ret.bytecode.resize(ret.bytecode.size() + bytesPerDataRef);
            break;
        case PushSub:
            ret.bytecode.push_back(dataRefPush);
            subRef.insert(make_pair(size_t(i.data()), ret.bytecode.size()));
            ret.bytecode.resize(ret.bytecode.size() + bytesPerDataRef);
            break;
        case PushSubSize:
        {
            auto s = m_subs.at(size_t(i.data()))->assemble().bytecode.size();
            i.setPushedValue(u256(s));
            byte b = max<unsigned>(1, dev::bytesRequired(s));
            ret.bytecode.push_back((byte)Instruction::PUSH1 - 1 + b);
            ret.bytecode.resize(ret.bytecode.size() + b);
            bytesRef byr(&ret.bytecode.back() + 1 - b, b);
            toBigEndian(s, byr);
            break;
        }
        case PushProgramSize:
        {
            ret.bytecode.push_back(dataRefPush);
            sizeRef.push_back(ret.bytecode.size());
            ret.bytecode.resize(ret.bytecode.size() + bytesPerDataRef);
            break;
        }
        case PushLibraryAddress:
            ret.bytecode.push_back(byte(Instruction::PUSH20));
            ret.linkReferences[ret.bytecode.size()] = m_libraries.at(i.data());
            ret.bytecode.resize(ret.bytecode.size() + 20);
            break;
        case PushDeployTimeAddress:
            ret.bytecode.push_back(byte(Instruction::PUSH20));
            ret.bytecode.resize(ret.bytecode.size() + 20);
            break;
        case Tag:
            assertThrow(i.data() != 0, AssemblyException, "Invalid tag position.");
            assertThrow(i.splitForeignPushTag().first == size_t(-1), AssemblyException, "Foreign tag.");
            assertThrow(ret.bytecode.size() < 0xffffffffL, AssemblyException, "Tag too large.");
            assertThrow(m_tagPositionsInBytecode[size_t(i.data())] == size_t(-1), AssemblyException, "Duplicate tag position.");
            m_tagPositionsInBytecode[size_t(i.data())] = ret.bytecode.size();
            ret.bytecode.push_back((byte)Instruction::JUMPDEST);
            break;
        default:
            BOOST_THROW_EXCEPTION(InvalidOpcode());
        }
    }

    if (!m_subs.empty() || !m_data.empty() || !m_auxiliaryData.empty())
        // Append an INVALID here to help tests find miscompilation.
        ret.bytecode.push_back(byte(Instruction::INVALID));

    for (size_t i = 0; i < m_subs.size(); ++i)
    {
        auto references = subRef.equal_range(i);
        if (references.first == references.second)
            continue;
        for (auto ref = references.first; ref != references.second; ++ref)
        {
            bytesRef r(ret.bytecode.data() + ref->second, bytesPerDataRef);
            toBigEndian(ret.bytecode.size(), r);
        }
        ret.append(m_subs[i]->assemble());
    }
    for (auto const& i: tagRef)
    {
        size_t subId;
        size_t tagId;
        tie(subId, tagId) = i.second;
        assertThrow(subId == size_t(-1) || subId < m_subs.size(), AssemblyException, "Invalid sub id");
        std::vector<size_t> const& tagPositions =
            subId == size_t(-1) ?
            m_tagPositionsInBytecode :
            m_subs[subId]->m_tagPositionsInBytecode;
        assertThrow(tagId < tagPositions.size(), AssemblyException, "Reference to non-existing tag.");
        size_t pos = tagPositions[tagId];
        assertThrow(pos != size_t(-1), AssemblyException, "Reference to tag without position.");
        assertThrow(dev::bytesRequired(pos) <= bytesPerTag, AssemblyException, "Tag too large for reserved space.");
        bytesRef r(ret.bytecode.data() + i.first, bytesPerTag);
        toBigEndian(pos, r);
    }
    for (auto const& dataItem: m_data)
    {
        auto references = dataRef.equal_range(dataItem.first);
        if (references.first == references.second)
            continue;
        for (auto ref = references.first; ref != references.second; ++ref)
        {
            bytesRef r(ret.bytecode.data() + ref->second, bytesPerDataRef);
            toBigEndian(ret.bytecode.size(), r);
        }
        ret.bytecode += dataItem.second;
    }

    ret.bytecode += m_auxiliaryData;

    for (unsigned pos: sizeRef)
    {
        bytesRef r(ret.bytecode.data() + pos, bytesPerDataRef);
        toBigEndian(ret.bytecode.size(), r);
    }
    return ret;
}