mirror of
https://github.com/ethereum/solidity
synced 2023-10-03 13:03:40 +00:00
338 lines
10 KiB
C++
338 lines
10 KiB
C++
/*
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This file is part of solidity.
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solidity is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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solidity is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with solidity. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <libyul/optimiser/ReasoningBasedSimplifier.h>
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#include <libyul/optimiser/SSAValueTracker.h>
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#include <libyul/optimiser/Semantics.h>
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#include <libyul/AST.h>
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#include <libyul/Utilities.h>
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#include <libyul/Dialect.h>
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#include <libyul/backends/evm/EVMDialect.h>
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#include <libsmtutil/SMTPortfolio.h>
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#include <libsmtutil/Helpers.h>
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#include <libsolutil/Visitor.h>
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#include <libsolutil/CommonData.h>
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#include <utility>
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#include <memory>
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using namespace std;
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using namespace solidity;
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using namespace solidity::util;
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using namespace solidity::yul;
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using namespace solidity::smtutil;
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void ReasoningBasedSimplifier::run(OptimiserStepContext& _context, Block& _ast)
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{
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set<YulString> ssaVars = SSAValueTracker::ssaVariables(_ast);
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ReasoningBasedSimplifier{_context.dialect, ssaVars}(_ast);
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}
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std::optional<string> ReasoningBasedSimplifier::invalidInCurrentEnvironment()
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{
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// SMTLib2 interface is always available, but we would like to have synchronous answers.
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if (smtutil::SMTPortfolio{}.solvers() <= 1)
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return string{"No SMT solvers available."};
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else
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return nullopt;
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}
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void ReasoningBasedSimplifier::operator()(VariableDeclaration& _varDecl)
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{
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if (_varDecl.variables.size() != 1 || !_varDecl.value)
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return;
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YulString varName = _varDecl.variables.front().name;
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if (!m_ssaVariables.count(varName))
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return;
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bool const inserted = m_variables.insert({varName, m_solver->newVariable("yul_" + varName.str(), defaultSort())}).second;
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yulAssert(inserted, "");
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m_solver->addAssertion(m_variables.at(varName) == encodeExpression(*_varDecl.value));
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}
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void ReasoningBasedSimplifier::operator()(If& _if)
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{
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if (!SideEffectsCollector{m_dialect, *_if.condition}.movable())
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return;
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smtutil::Expression condition = encodeExpression(*_if.condition);
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m_solver->push();
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m_solver->addAssertion(condition == constantValue(0));
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CheckResult result = m_solver->check({}).first;
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m_solver->pop();
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if (result == CheckResult::UNSATISFIABLE)
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{
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Literal trueCondition = m_dialect.trueLiteral();
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trueCondition.location = locationOf(*_if.condition);
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_if.condition = make_unique<yul::Expression>(move(trueCondition));
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}
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else
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{
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m_solver->push();
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m_solver->addAssertion(condition != constantValue(0));
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CheckResult result2 = m_solver->check({}).first;
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m_solver->pop();
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if (result2 == CheckResult::UNSATISFIABLE)
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{
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Literal falseCondition = m_dialect.zeroLiteralForType(m_dialect.boolType);
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falseCondition.location = locationOf(*_if.condition);
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_if.condition = make_unique<yul::Expression>(move(falseCondition));
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_if.body = yul::Block{};
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// Nothing left to be done.
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return;
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}
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}
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m_solver->push();
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m_solver->addAssertion(condition != constantValue(0));
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ASTModifier::operator()(_if.body);
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m_solver->pop();
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}
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ReasoningBasedSimplifier::ReasoningBasedSimplifier(
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Dialect const& _dialect,
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set<YulString> const& _ssaVariables
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):
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m_dialect(_dialect),
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m_ssaVariables(_ssaVariables),
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m_solver(make_unique<smtutil::SMTPortfolio>())
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{
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}
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smtutil::Expression ReasoningBasedSimplifier::encodeExpression(yul::Expression const& _expression)
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{
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return std::visit(GenericVisitor{
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[&](FunctionCall const& _functionCall)
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{
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if (auto const* dialect = dynamic_cast<EVMDialect const*>(&m_dialect))
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if (auto const* builtin = dialect->builtin(_functionCall.functionName.name))
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if (builtin->instruction)
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return encodeEVMBuiltin(*builtin->instruction, _functionCall.arguments);
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return newRestrictedVariable();
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},
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[&](Identifier const& _identifier)
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{
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if (
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m_ssaVariables.count(_identifier.name) &&
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m_variables.count(_identifier.name)
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)
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return m_variables.at(_identifier.name);
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else
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return newRestrictedVariable();
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},
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[&](Literal const& _literal)
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{
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return literalValue(_literal);
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}
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}, _expression);
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}
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smtutil::Expression ReasoningBasedSimplifier::encodeEVMBuiltin(
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evmasm::Instruction _instruction,
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vector<yul::Expression> const& _arguments
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)
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{
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vector<smtutil::Expression> arguments = applyMap(
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_arguments,
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[this](yul::Expression const& _expr) { return encodeExpression(_expr); }
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);
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switch (_instruction)
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{
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case evmasm::Instruction::ADD:
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return wrap(arguments.at(0) + arguments.at(1));
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case evmasm::Instruction::MUL:
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return wrap(arguments.at(0) * arguments.at(1));
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case evmasm::Instruction::SUB:
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return wrap(arguments.at(0) - arguments.at(1));
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case evmasm::Instruction::DIV:
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return smtutil::Expression::ite(
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arguments.at(1) == constantValue(0),
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constantValue(0),
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arguments.at(0) / arguments.at(1)
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);
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case evmasm::Instruction::SDIV:
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return smtutil::Expression::ite(
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arguments.at(1) == constantValue(0),
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constantValue(0),
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// No `wrap()` needed here, because -2**255 / -1 results
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// in 2**255 which is "converted" to its two's complement
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// representation 2**255 in `signedToUnsigned`
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signedToUnsigned(smtutil::signedDivisionEVM(
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unsignedToSigned(arguments.at(0)),
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unsignedToSigned(arguments.at(1))
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))
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);
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case evmasm::Instruction::MOD:
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return smtutil::Expression::ite(
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arguments.at(1) == constantValue(0),
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constantValue(0),
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arguments.at(0) % arguments.at(1)
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);
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case evmasm::Instruction::SMOD:
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return smtutil::Expression::ite(
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arguments.at(1) == constantValue(0),
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constantValue(0),
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signedToUnsigned(signedModuloEVM(
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unsignedToSigned(arguments.at(0)),
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unsignedToSigned(arguments.at(1))
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))
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);
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case evmasm::Instruction::LT:
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return booleanValue(arguments.at(0) < arguments.at(1));
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case evmasm::Instruction::SLT:
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return booleanValue(unsignedToSigned(arguments.at(0)) < unsignedToSigned(arguments.at(1)));
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case evmasm::Instruction::GT:
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return booleanValue(arguments.at(0) > arguments.at(1));
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case evmasm::Instruction::SGT:
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return booleanValue(unsignedToSigned(arguments.at(0)) > unsignedToSigned(arguments.at(1)));
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case evmasm::Instruction::EQ:
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return booleanValue(arguments.at(0) == arguments.at(1));
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case evmasm::Instruction::ISZERO:
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return booleanValue(arguments.at(0) == constantValue(0));
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case evmasm::Instruction::AND:
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return smtutil::Expression::ite(
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(arguments.at(0) == 0 || arguments.at(0) == 1) &&
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(arguments.at(1) == 0 || arguments.at(1) == 1),
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booleanValue(arguments.at(0) == 1 && arguments.at(1) == 1),
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bv2int(int2bv(arguments.at(0)) & int2bv(arguments.at(1)))
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);
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case evmasm::Instruction::OR:
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return smtutil::Expression::ite(
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(arguments.at(0) == 0 || arguments.at(0) == 1) &&
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(arguments.at(1) == 0 || arguments.at(1) == 1),
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booleanValue(arguments.at(0) == 1 || arguments.at(1) == 1),
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bv2int(int2bv(arguments.at(0)) | int2bv(arguments.at(1)))
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);
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case evmasm::Instruction::XOR:
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return bv2int(int2bv(arguments.at(0)) ^ int2bv(arguments.at(1)));
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case evmasm::Instruction::NOT:
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return smtutil::Expression(u256(-1)) - arguments.at(0);
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case evmasm::Instruction::SHL:
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return smtutil::Expression::ite(
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arguments.at(0) > 255,
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constantValue(0),
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bv2int(int2bv(arguments.at(1)) << int2bv(arguments.at(0)))
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);
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case evmasm::Instruction::SHR:
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return smtutil::Expression::ite(
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arguments.at(0) > 255,
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constantValue(0),
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bv2int(int2bv(arguments.at(1)) >> int2bv(arguments.at(0)))
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);
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case evmasm::Instruction::SAR:
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return smtutil::Expression::ite(
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arguments.at(0) > 255,
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constantValue(0),
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bv2int(smtutil::Expression::ashr(int2bv(arguments.at(1)), int2bv(arguments.at(0))))
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);
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case evmasm::Instruction::ADDMOD:
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return smtutil::Expression::ite(
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arguments.at(2) == constantValue(0),
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constantValue(0),
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(arguments.at(0) + arguments.at(1)) % arguments.at(2)
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);
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case evmasm::Instruction::MULMOD:
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return smtutil::Expression::ite(
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arguments.at(2) == constantValue(0),
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constantValue(0),
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(arguments.at(0) * arguments.at(1)) % arguments.at(2)
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);
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// TODO SIGNEXTEND
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default:
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break;
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}
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return newRestrictedVariable();
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}
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smtutil::Expression ReasoningBasedSimplifier::int2bv(smtutil::Expression _arg) const
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{
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return smtutil::Expression::int2bv(std::move(_arg), 256);
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}
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smtutil::Expression ReasoningBasedSimplifier::bv2int(smtutil::Expression _arg) const
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{
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return smtutil::Expression::bv2int(std::move(_arg));
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}
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smtutil::Expression ReasoningBasedSimplifier::newVariable()
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{
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return m_solver->newVariable(uniqueName(), defaultSort());
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}
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smtutil::Expression ReasoningBasedSimplifier::newRestrictedVariable()
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{
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smtutil::Expression var = newVariable();
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m_solver->addAssertion(0 <= var && var < smtutil::Expression(bigint(1) << 256));
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return var;
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}
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string ReasoningBasedSimplifier::uniqueName()
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{
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return "expr_" + to_string(m_varCounter++);
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}
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shared_ptr<Sort> ReasoningBasedSimplifier::defaultSort() const
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{
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return SortProvider::intSort();
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}
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smtutil::Expression ReasoningBasedSimplifier::booleanValue(smtutil::Expression _value) const
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{
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return smtutil::Expression::ite(_value, constantValue(1), constantValue(0));
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}
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smtutil::Expression ReasoningBasedSimplifier::constantValue(size_t _value) const
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{
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return _value;
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}
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smtutil::Expression ReasoningBasedSimplifier::literalValue(Literal const& _literal) const
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{
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return smtutil::Expression(valueOfLiteral(_literal));
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}
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smtutil::Expression ReasoningBasedSimplifier::unsignedToSigned(smtutil::Expression _value)
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{
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return smtutil::Expression::ite(
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_value < smtutil::Expression(bigint(1) << 255),
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_value,
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_value - smtutil::Expression(bigint(1) << 256)
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);
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}
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smtutil::Expression ReasoningBasedSimplifier::signedToUnsigned(smtutil::Expression _value)
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{
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return smtutil::Expression::ite(
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_value >= 0,
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_value,
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_value + smtutil::Expression(bigint(1) << 256)
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);
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}
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smtutil::Expression ReasoningBasedSimplifier::wrap(smtutil::Expression _value)
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{
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smtutil::Expression rest = newRestrictedVariable();
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smtutil::Expression multiplier = newVariable();
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m_solver->addAssertion(_value == multiplier * smtutil::Expression(bigint(1) << 256) + rest);
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return rest;
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}
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