solidity/libevmasm/Assembly.cpp

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/*
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
*/
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#include <libevmasm/Assembly.h>
#include <libevmasm/CommonSubexpressionEliminator.h>
#include <libevmasm/ControlFlowGraph.h>
#include <libevmasm/PeepholeOptimiser.h>
#include <libevmasm/JumpdestRemover.h>
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#include <libevmasm/BlockDeduplicator.h>
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#include <libevmasm/ConstantOptimiser.h>
#include <libevmasm/GasMeter.h>
#include <fstream>
#include <json/json.h>
using namespace std;
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using namespace solidity;
using namespace solidity::evmasm;
using namespace solidity::langutil;
using namespace solidity::util;
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AssemblyItem const& Assembly::append(AssemblyItem const& _i)
{
assertThrow(m_deposit >= 0, AssemblyException, "Stack underflow.");
m_deposit += _i.deposit();
m_items.emplace_back(_i);
if (!m_items.back().location().isValid() && m_currentSourceLocation.isValid())
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m_items.back().setLocation(m_currentSourceLocation);
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m_items.back().m_modifierDepth = m_currentModifierDepth;
return m_items.back();
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}
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);
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if (util::bytesRequired(ret) <= tagSize)
return ret;
}
}
namespace
{
string locationFromSources(StringMap const& _sourceCodes, SourceLocation const& _location)
{
if (!_location.hasText() || _sourceCodes.empty())
return "";
auto it = _sourceCodes.find(_location.source->name());
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) + "...";
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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().isValid() && _item.location() != m_location)
{
flush();
m_location = _item.location();
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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.isValid())
return;
m_out << m_prefix << " /*";
if (m_location.source)
m_out << " \"" + m_location.source->name() + "\"";
if (m_location.hasText())
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())
{
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_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;
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for (size_t i = 0; i < m_subs.size(); ++i)
{
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_out << endl << _prefix << "sub_" << i << ": assembly {\n";
m_subs[i]->assemblyStream(_out, _prefix + " ", _sourceCodes);
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_out << _prefix << "}" << endl;
}
}
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if (m_auxiliaryData.size() > 0)
_out << endl << _prefix << "auxdata: 0x" << toHex(m_auxiliaryData) << endl;
}
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string Assembly::assemblyString(StringMap const& _sourceCodes) const
{
ostringstream tmp;
assemblyStream(tmp, "", _sourceCodes);
return tmp.str();
}
Json::Value Assembly::createJsonValue(string _name, int _source, int _begin, int _end, string _value, string _jumpType)
{
Json::Value value;
value["name"] = _name;
value["source"] = _source;
value["begin"] = _begin;
value["end"] = _end;
if (!_value.empty())
value["value"] = _value;
if (!_jumpType.empty())
value["jumpType"] = _jumpType;
return value;
}
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string Assembly::toStringInHex(u256 _value)
{
std::stringstream hexStr;
hexStr << std::uppercase << hex << _value;
return hexStr.str();
}
Json::Value Assembly::assemblyJSON(map<string, unsigned> const& _sourceIndices) const
{
Json::Value root;
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Json::Value& collection = root[".code"] = Json::arrayValue;
for (AssemblyItem const& i: m_items)
{
unsigned sourceIndex = unsigned(-1);
if (i.location().source)
{
auto iter = _sourceIndices.find(i.location().source->name());
if (iter != _sourceIndices.end())
sourceIndex = iter->second;
}
switch (i.type())
{
case Operation:
collection.append(
createJsonValue(
instructionInfo(i.instruction()).name,
sourceIndex,
i.location().start,
i.location().end,
i.getJumpTypeAsString())
);
break;
case Push:
collection.append(
createJsonValue("PUSH", sourceIndex, i.location().start, i.location().end, toStringInHex(i.data()), i.getJumpTypeAsString()));
break;
case PushString:
collection.append(
createJsonValue("PUSH tag", sourceIndex, i.location().start, i.location().end, m_strings.at((h256)i.data())));
break;
case PushTag:
if (i.data() == 0)
collection.append(
createJsonValue("PUSH [ErrorTag]", sourceIndex, i.location().start, i.location().end, ""));
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else
collection.append(
createJsonValue("PUSH [tag]", sourceIndex, i.location().start, i.location().end, toString(i.data())));
break;
case PushSub:
collection.append(
createJsonValue("PUSH [$]", sourceIndex, i.location().start, i.location().end, toString(h256(i.data()))));
break;
case PushSubSize:
collection.append(
createJsonValue("PUSH #[$]", sourceIndex, i.location().start, i.location().end, toString(h256(i.data()))));
break;
case PushProgramSize:
collection.append(
createJsonValue("PUSHSIZE", sourceIndex, i.location().start, i.location().end));
break;
case PushLibraryAddress:
collection.append(
createJsonValue("PUSHLIB", sourceIndex, i.location().start, i.location().end, m_libraries.at(h256(i.data())))
);
break;
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case PushDeployTimeAddress:
collection.append(
createJsonValue("PUSHDEPLOYADDRESS", sourceIndex, i.location().start, i.location().end)
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);
break;
case PushImmutable:
collection.append(createJsonValue(
"PUSHIMMUTABLE",
sourceIndex,
i.location().start,
i.location().end,
m_immutables.at(h256(i.data()))
));
break;
case AssignImmutable:
collection.append(createJsonValue(
"ASSIGNIMMUTABLE",
sourceIndex,
i.location().start,
i.location().end,
m_immutables.at(h256(i.data()))
));
break;
case Tag:
collection.append(
createJsonValue("tag", sourceIndex, i.location().start, i.location().end, toString(i.data())));
collection.append(
createJsonValue("JUMPDEST", sourceIndex, i.location().start, i.location().end));
break;
case PushData:
collection.append(createJsonValue("PUSH data", sourceIndex, i.location().start, i.location().end, toStringInHex(i.data())));
break;
default:
assertThrow(false, InvalidOpcode, "");
}
}
if (!m_data.empty() || !m_subs.empty())
{
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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(_sourceIndices);
}
}
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if (m_auxiliaryData.size() > 0)
root[".auxdata"] = toHex(m_auxiliaryData);
return root;
}
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AssemblyItem Assembly::namedTag(string const& _name)
{
assertThrow(!_name.empty(), AssemblyException, "Empty named tag.");
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if (!m_namedTags.count(_name))
m_namedTags[_name] = size_t(newTag().data());
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return AssemblyItem{Tag, m_namedTags.at(_name)};
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}
AssemblyItem Assembly::newPushLibraryAddress(string const& _identifier)
{
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h256 h(util::keccak256(_identifier));
m_libraries[h] = _identifier;
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return AssemblyItem{PushLibraryAddress, h};
}
AssemblyItem Assembly::newPushImmutable(string const& _identifier)
{
h256 h(util::keccak256(_identifier));
m_immutables[h] = _identifier;
return AssemblyItem{PushImmutable, h};
}
AssemblyItem Assembly::newImmutableAssignment(string const& _identifier)
{
h256 h(util::keccak256(_identifier));
m_immutables[h] = _identifier;
return AssemblyItem{AssignImmutable, 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> _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)
{
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JumpdestRemover jumpdestOpt{m_items};
if (jumpdestOpt.optimise(_tagsReferencedFromOutside))
count++;
}
if (_settings.runPeephole)
{
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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)
{
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BlockDeduplicator dedup{m_items};
if (dedup.deduplicate())
{
for (auto const& replacement: dedup.replacedTags())
{
assertThrow(
replacement.first <= size_t(-1) && replacement.second <= size_t(-1),
OptimizerException,
"Invalid tag replacement."
);
assertThrow(
!tagReplacements.count(replacement.first),
OptimizerException,
"Replacement already known."
);
tagReplacements[replacement.first] = replacement.second;
if (_tagsReferencedFromOutside.erase(size_t(replacement.first)))
_tagsReferencedFromOutside.insert(size_t(replacement.second));
}
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;
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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;
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CommonSubexpressionEliminator eliminator{emptyState};
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auto orig = iter;
iter = eliminator.feedItems(iter, m_items.end(), usesMSize);
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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&)
{
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// This might happen if e.g. associativity and commutativity rules
// reorganise the expression tree, but not all leaves are available.
}
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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
);
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return tagReplacements;
}
LinkerObject const& Assembly::assemble() const
{
// Return the already assembled object, if present.
if (!m_assembledObject.bytecode.empty())
return m_assembledObject;
// Otherwise ensure the object is actually clear.
assertThrow(m_assembledObject.linkReferences.empty(), AssemblyException, "Unexpected link references.");
LinkerObject& ret = m_assembledObject;
size_t subTagSize = 1;
map<u256, pair<string, vector<size_t>>> immutableReferencesBySub;
for (auto const& sub: m_subs)
{
auto const& linkerObject = sub->assemble();
if (!linkerObject.immutableReferences.empty())
{
assertThrow(
immutableReferencesBySub.empty(),
AssemblyException,
"More than one sub-assembly references immutables."
);
immutableReferencesBySub = linkerObject.immutableReferences;
}
for (size_t tagPos: sub->m_tagPositionsInBytecode)
if (tagPos != size_t(-1) && tagPos > subTagSize)
subTagSize = tagPos;
}
bool setsImmutables = false;
bool pushesImmutables = false;
for (auto const& i: m_items)
if (i.type() == AssignImmutable)
{
i.setImmutableOccurrences(immutableReferencesBySub[i.data()].second.size());
setsImmutables = true;
}
else if (i.type() == PushImmutable)
pushesImmutables = true;
if (setsImmutables || pushesImmutables)
assertThrow(
setsImmutables != pushesImmutables,
AssemblyException,
"Cannot push and assign immutables in the same assembly subroutine."
);
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
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unsigned bytesPerTag = util::bytesRequired(bytesRequiredForCode);
uint8_t tagPush = (uint8_t)Instruction::PUSH1 - 1 + bytesPerTag;
unsigned bytesRequiredIncludingData = bytesRequiredForCode + 1 + m_auxiliaryData.size();
for (auto const& sub: m_subs)
bytesRequiredIncludingData += sub->assemble().bytecode.size();
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unsigned bytesPerDataRef = util::bytesRequired(bytesRequiredIncludingData);
uint8_t dataRefPush = (uint8_t)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((uint8_t)i.instruction());
break;
case PushString:
{
ret.bytecode.push_back((uint8_t)Instruction::PUSH32);
unsigned ii = 0;
for (auto j: m_strings.at((h256)i.data()))
if (++ii > 32)
break;
else
ret.bytecode.push_back((uint8_t)j);
while (ii++ < 32)
ret.bytecode.push_back(0);
break;
}
case Push:
{
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uint8_t b = max<unsigned>(1, util::bytesRequired(i.data()));
ret.bytecode.push_back((uint8_t)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:
assertThrow(i.data() <= size_t(-1), AssemblyException, "");
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:
{
assertThrow(i.data() <= size_t(-1), AssemblyException, "");
auto s = m_subs.at(size_t(i.data()))->assemble().bytecode.size();
i.setPushedValue(u256(s));
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uint8_t b = max<unsigned>(1, util::bytesRequired(s));
ret.bytecode.push_back((uint8_t)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(uint8_t(Instruction::PUSH20));
ret.linkReferences[ret.bytecode.size()] = m_libraries.at(i.data());
ret.bytecode.resize(ret.bytecode.size() + 20);
break;
case PushImmutable:
ret.bytecode.push_back(uint8_t(Instruction::PUSH32));
ret.immutableReferences[i.data()].first = m_immutables.at(i.data());
ret.immutableReferences[i.data()].second.emplace_back(ret.bytecode.size());
ret.bytecode.resize(ret.bytecode.size() + 32);
break;
case AssignImmutable:
for (auto const& offset: immutableReferencesBySub[i.data()].second)
{
ret.bytecode.push_back(uint8_t(Instruction::DUP1));
// TODO: should we make use of the constant optimizer methods for pushing the offsets?
bytes offsetBytes = toCompactBigEndian(u256(offset));
ret.bytecode.push_back(uint8_t(Instruction::PUSH1) - 1 + offsetBytes.size());
ret.bytecode += offsetBytes;
ret.bytecode.push_back(uint8_t(Instruction::MSTORE));
}
immutableReferencesBySub.erase(i.data());
ret.bytecode.push_back(uint8_t(Instruction::POP));
break;
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case PushDeployTimeAddress:
ret.bytecode.push_back(uint8_t(Instruction::PUSH20));
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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.");
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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((uint8_t)Instruction::JUMPDEST);
break;
default:
assertThrow(false, InvalidOpcode, "Unexpected opcode while assembling.");
}
}
assertThrow(
immutableReferencesBySub.empty(),
AssemblyException,
"Some immutables were read from but never assigned."
);
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if (!m_subs.empty() || !m_data.empty() || !m_auxiliaryData.empty())
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// Append an INVALID here to help tests find miscompilation.
ret.bytecode.push_back(uint8_t(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.");
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assertThrow(util::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;
}