solidity/Assembly.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/>.
*/
/** @file Assembly.cpp
 * @author Gav Wood <i@gavwood.com>
 * @date 2014
 */

#include "Assembly.h"

#include <libethsupport/Log.h>
#include <libethcore/CommonEth.h>

using namespace std;
using namespace eth;

int AssemblyItem::deposit() const
{
	switch (m_type)
	{
	case Operation:
		return c_instructionInfo.at((Instruction)(byte)m_data).ret - c_instructionInfo.at((Instruction)(byte)m_data).args;
	case Push: case PushString: case PushTag: case PushData:
		return 1;
	case Tag:
		return 0;
	default:;
	}
	return 0;
}

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

		for (AssemblyItem const& i: m_items)
			switch (i.m_type)
			{
			case Operation:
				ret++;
				break;
			case PushString:
				ret += 33;
				break;
			case Push:
				ret += 1 + max<unsigned>(1, eth::bytesRequired(i.m_data));
				break;
			case PushTag:
			case PushData:
				ret += 1 + br;
			case Tag:;
			default:;
			}
		if (eth::bytesRequired(ret) <= br)
			return ret;
	}
}

void Assembly::append(Assembly const& _a)
{
	for (AssemblyItem i: _a.m_items)
	{
		if (i.type() == Tag || i.type() == PushTag)
			i.m_data += m_usedTags;
		append(i);
	}
	m_usedTags += _a.m_usedTags;
	for (auto const& i: _a.m_data)
		m_data.insert(i);
	for (auto const& i: _a.m_strings)
		m_strings.insert(i);

	assert(!_a.m_baseDeposit);
	assert(!_a.m_totalDeposit);
}

void Assembly::append(Assembly const& _a, int _deposit)
{
	if (_deposit > _a.m_deposit)
		throw InvalidDeposit();
	else
	{
		append(_a);
		while (_deposit++ < _a.m_deposit)
			append(Instruction::POP);
	}
}

ostream& eth::operator<<(ostream& _out, AssemblyItemsConstRef _i)
{
	for (AssemblyItem const& i: _i)
		switch (i.type())
		{
		case Operation:
			_out << " " << c_instructionInfo.at((Instruction)(byte)i.data()).name;
			break;
		case Push:
			_out << " PUSH" << i.data();
			break;
		case PushString:
			_out << " PUSH'[" << h256(i.data()).abridged() << "]";
			break;
		case PushTag:
			_out << " PUSH[tag" << i.data() << "]";
			break;
		case Tag:
			_out << " tag" << i.data() << ":";
			break;
		case PushData:
			_out << " PUSH*[" << h256(i.data()).abridged() << "]";
			break;
		case UndefinedItem:
			_out << " ???";
		default:;
		}
	return _out;
}

ostream& Assembly::streamOut(ostream& _out) const
{
	_out << ".code:" << endl;
	for (AssemblyItem const& i: m_items)
		switch (i.m_type)
		{
		case Operation:
			_out << "  " << c_instructionInfo.at((Instruction)(byte)i.m_data).name << endl;
			break;
		case Push:
			_out << "  PUSH " << i.m_data << endl;
			break;
		case PushString:
			_out << "  PUSH \"" << m_strings.at((h256)i.m_data) << "\"" << endl;
			break;
		case PushTag:
			_out << "  PUSH [tag" << i.m_data << "]" << endl;
			break;
		case Tag:
			_out << "tag" << i.m_data << ": " << endl;
			break;
		case PushData:
			_out << "  PUSH [" << h256(i.m_data).abridged() << "]" << endl;
			break;
		default:;
		}

	if (m_data.size())
	{
		_out << ".data:" << endl;
		for (auto const& i: m_data)
			_out << "  " << i.first.abridged() << ": " << toHex(i.second) << endl;
	}
	return _out;
}

AssemblyItem const& Assembly::append(AssemblyItem const& _i)
{
	m_deposit += _i.deposit();
	m_items.push_back(_i);
	return back();
}

inline bool matches(AssemblyItemsConstRef _a, AssemblyItemsConstRef _b)
{
	if (_a.size() != _b.size())
		return false;
	for (unsigned i = 0; i < _a.size(); ++i)
		if (!_a[i].match(_b[i]))
			return false;
	return true;
}

struct OptimiserChannel: public LogChannel { static const char* name() { return "OPT"; } static const int verbosity = 12; };
#define copt eth::LogOutputStream<OptimiserChannel, true>()

void Assembly::optimise()
{
	map<Instruction, function<u256(u256, u256)>> c_simple =
	{
		{ Instruction::SUB, [](u256 a, u256 b)->u256{return a - b;} },
		{ Instruction::DIV, [](u256 a, u256 b)->u256{return a / b;} },
		{ Instruction::SDIV, [](u256 a, u256 b)->u256{u256 r; (s256&)r = (s256&)a / (s256&)b; return r;} },
		{ Instruction::MOD, [](u256 a, u256 b)->u256{return a % b;} },
		{ Instruction::SMOD, [](u256 a, u256 b)->u256{u256 r; (s256&)r = (s256&)a % (s256&)b; return r;} },
		{ Instruction::EXP, [](u256 a, u256 b)->u256{return boost::multiprecision::pow(a, (unsigned)b);} },
		{ Instruction::LT, [](u256 a, u256 b)->u256{return a < b ? 1 : 0;} },
		{ Instruction::GT, [](u256 a, u256 b)->u256{return a > b ? 1 : 0;} },
		{ Instruction::SLT, [](u256 a, u256 b)->u256{return *(s256*)&a < *(s256*)&b ? 1 : 0;} },
		{ Instruction::SGT, [](u256 a, u256 b)->u256{return *(s256*)&a > *(s256*)&b ? 1 : 0;} },
		{ Instruction::EQ, [](u256 a, u256 b)->u256{return a == b ? 1 : 0;} },
	};
	map<Instruction, function<u256(u256, u256)>> c_associative =
	{
		{ Instruction::ADD, [](u256 a, u256 b)->u256{return a + b;} },
		{ Instruction::MUL, [](u256 a, u256 b)->u256{return a * b;} },
	};
	std::vector<pair<AssemblyItems, function<AssemblyItems(AssemblyItemsConstRef)>>> rules =
	{
		{ { Push, Instruction::POP }, [](AssemblyItemsConstRef) -> AssemblyItems { return {}; } },
		{ { PushTag, Instruction::POP }, [](AssemblyItemsConstRef) -> AssemblyItems { return {}; } },
		{ { PushString, Instruction::POP }, [](AssemblyItemsConstRef) -> AssemblyItems { return {}; } },
		{ { Push, PushTag, Instruction::JUMPI }, [](AssemblyItemsConstRef m) -> AssemblyItems { if (m[0].data()) return { m[1], Instruction::JUMP }; else return {}; } },
		{ { Instruction::NOT, Instruction::NOT }, [](AssemblyItemsConstRef) -> AssemblyItems { return {}; } },
	};

	for (auto const& i: c_simple)
		rules.push_back({ { Push, Push, i.first }, [&](AssemblyItemsConstRef m) -> AssemblyItems { return { i.second(m[1].data(), m[0].data()) }; } });
	for (auto const& i: c_associative)
	{
		rules.push_back({ { Push, Push, i.first }, [&](AssemblyItemsConstRef m) -> AssemblyItems { return { i.second(m[1].data(), m[0].data()) }; } });
		rules.push_back({ { Push, i.first, Push, i.first }, [&](AssemblyItemsConstRef m) -> AssemblyItems { return { i.second(m[2].data(), m[0].data()), i.first }; } });
		rules.push_back({ { PushTag, Instruction::JUMP, Tag }, [&](AssemblyItemsConstRef m) -> AssemblyItems { if (m[0].m_data == m[2].m_data) return {}; else return m.toVector(); }});
	}

	copt << *this;

	unsigned total = 0;
	for (unsigned count = 1; count > 0; total += count)
	{
		count = 0;
		map<u256, unsigned> tags;
		for (unsigned i = 0; i < m_items.size(); ++i)
		{
			for (auto const& r: rules)
			{
				auto vr = AssemblyItemsConstRef(&m_items).cropped(i, r.first.size());
				if (matches(&r.first, vr))
				{
					auto rw = r.second(vr);
					if (rw.size() < vr.size())
					{
						copt << vr << "matches" << AssemblyItemsConstRef(&r.first) << "becomes...";
						for (unsigned j = 0; j < vr.size(); ++j)
							if (j < rw.size())
								m_items[i + j] = rw[j];
							else
								m_items.erase(m_items.begin() + i + rw.size());
						copt << AssemblyItemsConstRef(&rw);
						count++;
						copt << "Now:\n" << m_items;
					}
				}
			}
			if (m_items[i].type() == Operation && m_items[i].data() == (byte)Instruction::JUMP)
			{
				bool o = false;
				while (m_items.size() > i + 1 && m_items[i + 1].type() != Tag)
				{
					m_items.erase(m_items.begin() + i + 1);
					o = true;
				}
				if (o)
				{
					copt << "Jump with no tag. Now:\n" << m_items;
					++count;
				}
			}
		}

		for (unsigned i = 0; i < m_items.size(); ++i)
			if (m_items[i].type() == Tag)
				tags.insert(make_pair(m_items[i].data(), i));

		for (auto const& i: m_items)
			if (i.type() == PushTag)
				tags.erase(i.data());

		if (tags.size())
		{
			auto t = *tags.begin();
			unsigned i = t.second;
			if (i && m_items[i - 1].type() == Operation && m_items[i - 1].data() == (byte)Instruction::JUMP)
				while (i < m_items.size() && (m_items[i].type() != Tag || tags.count(m_items[i].data())))
				{
					if (m_items[i].type() == Tag && tags.count(m_items[i].data()))
						tags.erase(m_items[i].data());
					m_items.erase(m_items.begin() + i);
				}
			else
			{
				m_items.erase(m_items.begin() + i);
				tags.erase(t.first);
			}
			copt << "Unused tag. Now:\n" << m_items;
			++count;
		}
	}

	copt << total << " optimisations done.";
}

bytes Assembly::assemble() const
{
	bytes ret;

	unsigned totalBytes = bytesRequired();
	ret.reserve(totalBytes);
	vector<unsigned> tagPos(m_usedTags);
	map<unsigned, unsigned> tagRef;
	multimap<h256, unsigned> dataRef;
	unsigned bytesPerTag = eth::bytesRequired(totalBytes);
	byte tagPush = (byte)Instruction::PUSH1 - 1 + bytesPerTag;

	for (AssemblyItem const& i: m_items)
		switch (i.m_type)
		{
		case Operation:
			ret.push_back((byte)i.m_data);
			break;
		case PushString:
		{
			ret.push_back((byte)Instruction::PUSH32);
			unsigned ii = 0;
			for (auto j: m_strings.at((h256)i.m_data))
				if (++ii > 32)
					break;
				else
					ret.push_back((byte)j);
			while (ii++ < 32)
				ret.push_back(0);
			break;
		}
		case Push:
		{
			byte b = max<unsigned>(1, eth::bytesRequired(i.m_data));
			ret.push_back((byte)Instruction::PUSH1 - 1 + b);
			ret.resize(ret.size() + b);
			bytesRef byr(&ret.back() + 1 - b, b);
			toBigEndian(i.m_data, byr);
			break;
		}
		case PushTag:
		{
			ret.push_back(tagPush);
			tagRef[ret.size()] = (unsigned)i.m_data;
			ret.resize(ret.size() + bytesPerTag);
			break;
		}
		case PushData:
		{
			ret.push_back(tagPush);
			dataRef.insert(make_pair((h256)i.m_data, ret.size()));
			ret.resize(ret.size() + bytesPerTag);
			break;
		}
		case Tag:
			tagPos[(unsigned)i.m_data] = ret.size();
			break;
		default:;
		}

	for (auto const& i: tagRef)
	{
		bytesRef r(ret.data() + i.first, bytesPerTag);
		toBigEndian(tagPos[i.second], r);
	}

	if (m_data.size())
	{
		ret.push_back(0);
		for (auto const& i: m_data)
		{
			auto its = dataRef.equal_range(i.first);
			if (its.first != its.second)
			{
				for (auto it = its.first; it != its.second; ++it)
				{
					bytesRef r(ret.data() + it->second, bytesPerTag);
					toBigEndian(ret.size(), r);
				}
				for (auto b: i.second)
					ret.push_back(b);
			}
		}
	}
	return ret;
}