solidity/libyul/optimiser/SimplificationRules.cpp
2020-05-27 11:57:08 +02:00

260 lines
8.2 KiB
C++

/*
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/>.
*/
/**
* Module for applying replacement rules against Expressions.
*/
#include <libyul/optimiser/SimplificationRules.h>
#include <libyul/optimiser/ASTCopier.h>
#include <libyul/optimiser/Semantics.h>
#include <libyul/optimiser/SyntacticalEquality.h>
#include <libyul/optimiser/DataFlowAnalyzer.h>
#include <libyul/backends/evm/EVMDialect.h>
#include <libyul/AsmData.h>
#include <libyul/Utilities.h>
#include <libevmasm/RuleList.h>
using namespace std;
using namespace solidity;
using namespace solidity::evmasm;
using namespace solidity::langutil;
using namespace solidity::yul;
SimplificationRules::Rule const* SimplificationRules::findFirstMatch(
Expression const& _expr,
Dialect const& _dialect,
map<YulString, AssignedValue> const& _ssaValues
)
{
auto instruction = instructionAndArguments(_dialect, _expr);
if (!instruction)
return nullptr;
static std::map<std::optional<EVMVersion>, std::unique_ptr<SimplificationRules>> evmRules;
std::optional<EVMVersion> version;
if (yul::EVMDialect const* evmDialect = dynamic_cast<yul::EVMDialect const*>(&_dialect))
version = evmDialect->evmVersion();
if (!evmRules[version])
evmRules[version] = std::make_unique<SimplificationRules>(version);
SimplificationRules& rules = *evmRules[version];
assertThrow(rules.isInitialized(), OptimizerException, "Rule list not properly initialized.");
for (auto const& rule: rules.m_rules[uint8_t(instruction->first)])
{
rules.resetMatchGroups();
if (rule.pattern.matches(_expr, _dialect, _ssaValues))
if (!rule.feasible || rule.feasible())
return &rule;
}
return nullptr;
}
bool SimplificationRules::isInitialized() const
{
return !m_rules[uint8_t(evmasm::Instruction::ADD)].empty();
}
std::optional<std::pair<evmasm::Instruction, vector<Expression> const*>>
SimplificationRules::instructionAndArguments(Dialect const& _dialect, Expression const& _expr)
{
if (holds_alternative<FunctionCall>(_expr))
if (auto const* dialect = dynamic_cast<EVMDialect const*>(&_dialect))
if (auto const* builtin = dialect->builtin(std::get<FunctionCall>(_expr).functionName.name))
if (builtin->instruction)
return make_pair(*builtin->instruction, &std::get<FunctionCall>(_expr).arguments);
return {};
}
void SimplificationRules::addRules(std::vector<Rule> const& _rules)
{
for (auto const& r: _rules)
addRule(r);
}
void SimplificationRules::addRule(Rule const& _rule)
{
m_rules[uint8_t(_rule.pattern.instruction())].push_back(_rule);
}
SimplificationRules::SimplificationRules(std::optional<langutil::EVMVersion> _evmVersion)
{
// Multiple occurrences of one of these inside one rule must match the same equivalence class.
// Constants.
Pattern A(PatternKind::Constant);
Pattern B(PatternKind::Constant);
Pattern C(PatternKind::Constant);
// Anything.
Pattern W;
Pattern X;
Pattern Y;
Pattern Z;
A.setMatchGroup(1, m_matchGroups);
B.setMatchGroup(2, m_matchGroups);
C.setMatchGroup(3, m_matchGroups);
W.setMatchGroup(4, m_matchGroups);
X.setMatchGroup(5, m_matchGroups);
Y.setMatchGroup(6, m_matchGroups);
Z.setMatchGroup(7, m_matchGroups);
addRules(simplificationRuleList(_evmVersion, A, B, C, W, X, Y, Z));
assertThrow(isInitialized(), OptimizerException, "Rule list not properly initialized.");
}
yul::Pattern::Pattern(evmasm::Instruction _instruction, initializer_list<Pattern> _arguments):
m_kind(PatternKind::Operation),
m_instruction(_instruction),
m_arguments(_arguments)
{
}
void Pattern::setMatchGroup(unsigned _group, map<unsigned, Expression const*>& _matchGroups)
{
m_matchGroup = _group;
m_matchGroups = &_matchGroups;
}
bool Pattern::matches(
Expression const& _expr,
Dialect const& _dialect,
map<YulString, AssignedValue> const& _ssaValues
) const
{
Expression const* expr = &_expr;
// Resolve the variable if possible.
// Do not do it for "Any" because we can check identity better for variables.
if (m_kind != PatternKind::Any && holds_alternative<Identifier>(_expr))
{
YulString varName = std::get<Identifier>(_expr).name;
if (_ssaValues.count(varName))
if (Expression const* new_expr = _ssaValues.at(varName).value)
expr = new_expr;
}
assertThrow(expr, OptimizerException, "");
if (m_kind == PatternKind::Constant)
{
if (!holds_alternative<Literal>(*expr))
return false;
Literal const& literal = std::get<Literal>(*expr);
if (literal.kind != LiteralKind::Number)
return false;
if (m_data && *m_data != u256(literal.value.str()))
return false;
assertThrow(m_arguments.empty(), OptimizerException, "");
}
else if (m_kind == PatternKind::Operation)
{
auto instrAndArgs = SimplificationRules::instructionAndArguments(_dialect, *expr);
if (!instrAndArgs || m_instruction != instrAndArgs->first)
return false;
assertThrow(m_arguments.size() == instrAndArgs->second->size(), OptimizerException, "");
for (size_t i = 0; i < m_arguments.size(); ++i)
if (!m_arguments[i].matches(instrAndArgs->second->at(i), _dialect, _ssaValues))
return false;
}
else
{
assertThrow(m_arguments.empty(), OptimizerException, "\"Any\" should not have arguments.");
}
if (m_matchGroup)
{
// We support matching multiple expressions that require the same value
// based on identical ASTs, which have to be movable.
// TODO: add tests:
// - { let x := mload(0) let y := and(x, x) }
// - { let x := 4 let y := and(x, y) }
// This code uses `_expr` again for "Any", because we want the comparison to be done
// on the variables and not their values.
// The assumption is that CSE or local value numbering has been done prior to this step.
if (m_matchGroups->count(m_matchGroup))
{
assertThrow(m_kind == PatternKind::Any, OptimizerException, "Match group repetition for non-any.");
Expression const* firstMatch = (*m_matchGroups)[m_matchGroup];
assertThrow(firstMatch, OptimizerException, "Match set but to null.");
return
SyntacticallyEqual{}(*firstMatch, _expr) &&
SideEffectsCollector(_dialect, _expr).movable();
}
else if (m_kind == PatternKind::Any)
(*m_matchGroups)[m_matchGroup] = &_expr;
else
{
assertThrow(m_kind == PatternKind::Constant, OptimizerException, "Match group set for operation.");
// We do not use _expr here, because we want the actual number.
(*m_matchGroups)[m_matchGroup] = expr;
}
}
return true;
}
evmasm::Instruction Pattern::instruction() const
{
assertThrow(m_kind == PatternKind::Operation, OptimizerException, "");
return m_instruction;
}
Expression Pattern::toExpression(SourceLocation const& _location) const
{
if (matchGroup())
return ASTCopier().translate(matchGroupValue());
if (m_kind == PatternKind::Constant)
{
assertThrow(m_data, OptimizerException, "No match group and no constant value given.");
return Literal{_location, LiteralKind::Number, YulString{util::formatNumber(*m_data)}, {}};
}
else if (m_kind == PatternKind::Operation)
{
vector<Expression> arguments;
for (auto const& arg: m_arguments)
arguments.emplace_back(arg.toExpression(_location));
string name = instructionInfo(m_instruction).name;
transform(begin(name), end(name), begin(name), [](auto _c) { return tolower(_c); });
return FunctionCall{
_location,
Identifier{_location, YulString{name}},
std::move(arguments)
};
}
assertThrow(false, OptimizerException, "Pattern of kind 'any', but no match group.");
}
u256 Pattern::d() const
{
return valueOfNumberLiteral(std::get<Literal>(matchGroupValue()));
}
Expression const& Pattern::matchGroupValue() const
{
assertThrow(m_matchGroup > 0, OptimizerException, "");
assertThrow(!!m_matchGroups, OptimizerException, "");
assertThrow((*m_matchGroups)[m_matchGroup], OptimizerException, "");
return *(*m_matchGroups)[m_matchGroup];
}