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Merge pull request #11349 from ethereum/create-solver-class-from-reasoning-based-simplifier

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Create solver class from reasoning based simplifier
This commit is contained in:
chriseth 2021-05-10 14:12:22 +02:00 committed by GitHub
commit 643140e2d6
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GPG Key ID: 4AEE18F83AFDEB23
5 changed files with 271 additions and 146 deletions
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2
libyul/CMakeLists.txt
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@ -166,6 +166,8 @@ add_library(yul
optimiser/RedundantAssignEliminator.h
optimiser/Rematerialiser.cpp
optimiser/Rematerialiser.h
optimiser/SMTSolver.cpp
optimiser/SMTSolver.h
optimiser/SSAReverser.cpp
optimiser/SSAReverser.h
optimiser/SSATransform.cpp

132
libyul/optimiser/ReasoningBasedSimplifier.cpp
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@ -16,8 +16,8 @@
*/
#include <libyul/optimiser/ReasoningBasedSimplifier.h>
#include <libyul/optimiser/SMTSolver.h>
#include <libyul/optimiser/OptimizerUtilities.h>
#include <libyul/optimiser/SSAValueTracker.h>
#include <libyul/optimiser/Semantics.h>
#include <libyul/AST.h>
@ -56,14 +56,7 @@ std::optional<string> ReasoningBasedSimplifier::invalidInCurrentEnvironment()
void ReasoningBasedSimplifier::operator()(VariableDeclaration& _varDecl)
{
if (_varDecl.variables.size() != 1 || !_varDecl.value)
return;
YulString varName = _varDecl.variables.front().name;
if (!m_ssaVariables.count(varName))
return;
bool const inserted = m_variables.insert({varName, m_solver->newVariable("yul_" + varName.str(), defaultSort())}).second;
yulAssert(inserted, "");
m_solver->addAssertion(m_variables.at(varName) == encodeExpression(*_varDecl.value));
SMTSolver::encodeVariableDeclaration(_varDecl);
}
void ReasoningBasedSimplifier::operator()(If& _if)
@ -111,37 +104,11 @@ ReasoningBasedSimplifier::ReasoningBasedSimplifier(
Dialect const& _dialect,
set<YulString> const& _ssaVariables
):
m_dialect(_dialect),
m_ssaVariables(_ssaVariables),
m_solver(make_unique<smtutil::SMTPortfolio>())
SMTSolver(_ssaVariables, _dialect),
m_dialect(_dialect)
{
}
smtutil::Expression ReasoningBasedSimplifier::encodeExpression(yul::Expression const& _expression)
{
return std::visit(GenericVisitor{
[&](FunctionCall const& _functionCall)
{
if (auto instruction = toEVMInstruction(m_dialect, _functionCall.functionName.name))
return encodeEVMBuiltin(*instruction, _functionCall.arguments);
return newRestrictedVariable();
},
[&](Identifier const& _identifier)
{
if (
m_ssaVariables.count(_identifier.name) &&
m_variables.count(_identifier.name)
)
return m_variables.at(_identifier.name);
else
return newRestrictedVariable();
},
[&](Literal const& _literal)
{
return literalValue(_literal);
}
}, _expression);
}
smtutil::Expression ReasoningBasedSimplifier::encodeEVMBuiltin(
evmasm::Instruction _instruction,
@ -172,10 +139,10 @@ smtutil::Expression ReasoningBasedSimplifier::encodeEVMBuiltin(
constantValue(0),
// No `wrap()` needed here, because -2**255 / -1 results
// in 2**255 which is "converted" to its two's complement
// representation 2**255 in `signedToUnsigned`
signedToUnsigned(smtutil::signedDivisionEVM(
unsignedToSigned(arguments.at(0)),
unsignedToSigned(arguments.at(1))
// representation 2**255 in `signedToTwosComplement`
signedToTwosComplement(smtutil::signedDivisionEVM(
twosComplementToSigned(arguments.at(0)),
twosComplementToSigned(arguments.at(1))
))
);
case evmasm::Instruction::MOD:
@ -188,19 +155,19 @@ smtutil::Expression ReasoningBasedSimplifier::encodeEVMBuiltin(
return smtutil::Expression::ite(
arguments.at(1) == constantValue(0),
constantValue(0),
signedToUnsigned(signedModuloEVM(
unsignedToSigned(arguments.at(0)),
unsignedToSigned(arguments.at(1))
signedToTwosComplement(signedModuloEVM(
twosComplementToSigned(arguments.at(0)),
twosComplementToSigned(arguments.at(1))
))
);
case evmasm::Instruction::LT:
return booleanValue(arguments.at(0) < arguments.at(1));
case evmasm::Instruction::SLT:
return booleanValue(unsignedToSigned(arguments.at(0)) < unsignedToSigned(arguments.at(1)));
return booleanValue(twosComplementToSigned(arguments.at(0)) < twosComplementToSigned(arguments.at(1)));
case evmasm::Instruction::GT:
return booleanValue(arguments.at(0) > arguments.at(1));
case evmasm::Instruction::SGT:
return booleanValue(unsignedToSigned(arguments.at(0)) > unsignedToSigned(arguments.at(1)));
return booleanValue(twosComplementToSigned(arguments.at(0)) > twosComplementToSigned(arguments.at(1)));
case evmasm::Instruction::EQ:
return booleanValue(arguments.at(0) == arguments.at(1));
case evmasm::Instruction::ISZERO:
@ -259,76 +226,3 @@ smtutil::Expression ReasoningBasedSimplifier::encodeEVMBuiltin(
}
return newRestrictedVariable();
}
smtutil::Expression ReasoningBasedSimplifier::int2bv(smtutil::Expression _arg) const
{
return smtutil::Expression::int2bv(std::move(_arg), 256);
}
smtutil::Expression ReasoningBasedSimplifier::bv2int(smtutil::Expression _arg) const
{
return smtutil::Expression::bv2int(std::move(_arg));
}
smtutil::Expression ReasoningBasedSimplifier::newVariable()
{
return m_solver->newVariable(uniqueName(), defaultSort());
}
smtutil::Expression ReasoningBasedSimplifier::newRestrictedVariable()
{
smtutil::Expression var = newVariable();
m_solver->addAssertion(0 <= var && var < smtutil::Expression(bigint(1) << 256));
return var;
}
string ReasoningBasedSimplifier::uniqueName()
{
return "expr_" + to_string(m_varCounter++);
}
shared_ptr<Sort> ReasoningBasedSimplifier::defaultSort() const
{
return SortProvider::intSort();
}
smtutil::Expression ReasoningBasedSimplifier::booleanValue(smtutil::Expression _value) const
{
return smtutil::Expression::ite(_value, constantValue(1), constantValue(0));
}
smtutil::Expression ReasoningBasedSimplifier::constantValue(size_t _value) const
{
return _value;
}
smtutil::Expression ReasoningBasedSimplifier::literalValue(Literal const& _literal) const
{
return smtutil::Expression(valueOfLiteral(_literal));
}
smtutil::Expression ReasoningBasedSimplifier::unsignedToSigned(smtutil::Expression _value)
{
return smtutil::Expression::ite(
_value < smtutil::Expression(bigint(1) << 255),
_value,
_value - smtutil::Expression(bigint(1) << 256)
);
}
smtutil::Expression ReasoningBasedSimplifier::signedToUnsigned(smtutil::Expression _value)
{
return smtutil::Expression::ite(
_value >= 0,
_value,
_value + smtutil::Expression(bigint(1) << 256)
);
}
smtutil::Expression ReasoningBasedSimplifier::wrap(smtutil::Expression _value)
{
smtutil::Expression rest = newRestrictedVariable();
smtutil::Expression multiplier = newVariable();
m_solver->addAssertion(_value == multiplier * smtutil::Expression(bigint(1) << 256) + rest);
return rest;
}

31
libyul/optimiser/ReasoningBasedSimplifier.h
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@ -16,6 +16,7 @@
*/
#pragma once
#include <libyul/optimiser/SMTSolver.h>
#include <libyul/optimiser/ASTWalker.h>
#include <libyul/optimiser/OptimiserStep.h>
#include <libyul/Dialect.h>
@ -46,7 +47,7 @@ namespace solidity::yul
*
* Prerequisite: Disambiguator, SSATransform.
*/
class ReasoningBasedSimplifier: public ASTModifier
class ReasoningBasedSimplifier: public ASTModifier, SMTSolver
{
public:
static constexpr char const* name{"ReasoningBasedSimplifier"};
@ -63,36 +64,12 @@ private:
std::set<YulString> const& _ssaVariables
);
smtutil::Expression encodeExpression(
Expression const& _expression
);
virtual smtutil::Expression encodeEVMBuiltin(
smtutil::Expression encodeEVMBuiltin(
evmasm::Instruction _instruction,
std::vector<Expression> const& _arguments
);
smtutil::Expression int2bv(smtutil::Expression _arg) const;
smtutil::Expression bv2int(smtutil::Expression _arg) const;
smtutil::Expression newVariable();
virtual smtutil::Expression newRestrictedVariable();
std::string uniqueName();
virtual std::shared_ptr<smtutil::Sort> defaultSort() const;
virtual smtutil::Expression booleanValue(smtutil::Expression _value) const;
virtual smtutil::Expression constantValue(size_t _value) const;
virtual smtutil::Expression literalValue(Literal const& _literal) const;
virtual smtutil::Expression unsignedToSigned(smtutil::Expression _value);
virtual smtutil::Expression signedToUnsigned(smtutil::Expression _value);
virtual smtutil::Expression wrap(smtutil::Expression _value);
) override;
Dialect const& m_dialect;
std::set<YulString> const& m_ssaVariables;
std::unique_ptr<smtutil::SolverInterface> m_solver;
std::map<YulString, smtutil::Expression> m_variables;
size_t m_varCounter = 0;
};
}

160
libyul/optimiser/SMTSolver.cpp Normal file
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@ -0,0 +1,160 @@
/*
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/>.
*/
#include <libyul/optimiser/SMTSolver.h>
#include <libyul/optimiser/OptimizerUtilities.h>
#include <libyul/AST.h>
#include <libyul/Utilities.h>
#include <libsolutil/Visitor.h>
#include <libsolutil/CommonData.h>
#include <libsmtutil/SMTPortfolio.h>
#include <libsmtutil/Helpers.h>
using namespace solidity::yul;
using namespace solidity::util;
using namespace solidity::smtutil;
using namespace solidity;
using namespace std;
SMTSolver::SMTSolver(set<YulString> const& _ssaVariables, Dialect const& _dialect):
m_ssaVariables(_ssaVariables),
m_solver(make_unique<smtutil::SMTPortfolio>()),
m_dialect(_dialect)
{ }
smtutil::Expression SMTSolver::encodeExpression(Expression const& _expression)
{
return std::visit(GenericVisitor{
[&](FunctionCall const& _functionCall)
{
if (auto instruction = toEVMInstruction(m_dialect, _functionCall.functionName.name))
return encodeEVMBuiltin(*instruction, _functionCall.arguments);
return newRestrictedVariable();
},
[&](Identifier const& _identifier)
{
if (
m_ssaVariables.count(_identifier.name) &&
m_variables.count(_identifier.name)
)
return m_variables.at(_identifier.name);
else
return newRestrictedVariable();
},
[&](Literal const& _literal)
{
return literalValue(_literal);
}
}, _expression);
}
smtutil::Expression SMTSolver::int2bv(smtutil::Expression _arg)
{
return smtutil::Expression::int2bv(std::move(_arg), 256);
}
smtutil::Expression SMTSolver::bv2int(smtutil::Expression _arg)
{
return smtutil::Expression::bv2int(std::move(_arg));
}
smtutil::Expression SMTSolver::newVariable()
{
return m_solver->newVariable(uniqueName(), defaultSort());
}
smtutil::Expression SMTSolver::newRestrictedVariable(bigint _maxValue)
{
smtutil::Expression var = newVariable();
m_solver->addAssertion(0 <= var && var <= smtutil::Expression(_maxValue));
return var;
}
string SMTSolver::uniqueName()
{
return "expr_" + to_string(m_varCounter++);
}
shared_ptr<Sort> SMTSolver::defaultSort() const
{
return SortProvider::intSort();
}
smtutil::Expression SMTSolver::booleanValue(smtutil::Expression _value)
{
return smtutil::Expression::ite(_value, constantValue(1), constantValue(0));
}
smtutil::Expression SMTSolver::constantValue(bigint _value)
{
return _value;
}
smtutil::Expression SMTSolver::literalValue(Literal const& _literal)
{
return smtutil::Expression(valueOfLiteral(_literal));
}
smtutil::Expression SMTSolver::twosComplementToSigned(smtutil::Expression _value)
{
return smtutil::Expression::ite(
_value < smtutil::Expression(bigint(1) << 255),
_value,
_value - smtutil::Expression(bigint(1) << 256)
);
}
smtutil::Expression SMTSolver::signedToTwosComplement(smtutil::Expression _value)
{
return smtutil::Expression::ite(
_value >= 0,
_value,
_value + smtutil::Expression(bigint(1) << 256)
);
}
smtutil::Expression SMTSolver::wrap(smtutil::Expression _value)
{
smtutil::Expression rest = newRestrictedVariable();
smtutil::Expression multiplier = newVariable();
m_solver->addAssertion(_value == multiplier * smtutil::Expression(bigint(1) << 256) + rest);
return rest;
}
void SMTSolver::encodeVariableDeclaration(VariableDeclaration const& _varDecl)
{
if (
_varDecl.variables.size() == 1 &&
_varDecl.value &&
m_ssaVariables.count(_varDecl.variables.front().name)
)
{
YulString const& variableName = _varDecl.variables.front().name;
bool const inserted = m_variables.insert({
variableName,
m_solver->newVariable("yul_" + variableName.str(), defaultSort())
}).second;
yulAssert(inserted, "");
m_solver->addAssertion(
m_variables.at(variableName) == encodeExpression(*_varDecl.value)
);
}
}

92
libyul/optimiser/SMTSolver.h Normal file
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@ -0,0 +1,92 @@
/*
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/>.
*/
#pragma once
#include <libyul/AST.h>
#include <libyul/Dialect.h>
#include <libyul/Exceptions.h>
// because of instruction
#include <libyul/backends/evm/EVMDialect.h>
#include <libsmtutil/SolverInterface.h>
#include <memory>
namespace solidity::smtutil
{
class SolverInterface;
class Expression;
struct Sort;
}
namespace solidity::yul
{
/**
* Base class for SMT based optimization steps.
*
* Works best when used with AST in SSA form.
*/
class SMTSolver
{
protected:
SMTSolver(
std::set<YulString> const& _ssaVariables,
Dialect const& _dialect
);
/// Helper function that encodes VariableDeclaration
void encodeVariableDeclaration(VariableDeclaration const& _varDecl);
/// The encoding for a builtin. The type of encoding determines what we are
/// solving for.
virtual smtutil::Expression encodeEVMBuiltin(
evmasm::Instruction _instruction,
std::vector<Expression> const& _arguments
) = 0;
smtutil::Expression encodeExpression(Expression const& _expression);
static smtutil::Expression int2bv(smtutil::Expression _arg);
static smtutil::Expression bv2int(smtutil::Expression _arg);
smtutil::Expression newVariable();
virtual smtutil::Expression newRestrictedVariable(bigint _maxValue = (bigint(1) << 256) - 1);
std::string uniqueName();
virtual std::shared_ptr<smtutil::Sort> defaultSort() const;
static smtutil::Expression booleanValue(smtutil::Expression _value);
static smtutil::Expression constantValue(bigint _value);
static smtutil::Expression literalValue(Literal const& _literal);
static smtutil::Expression twosComplementToSigned(smtutil::Expression _value);
static smtutil::Expression signedToTwosComplement(smtutil::Expression _value);
smtutil::Expression wrap(smtutil::Expression _value);
std::set<YulString> const& m_ssaVariables;
std::unique_ptr<smtutil::SolverInterface> m_solver;
std::map<YulString, smtutil::Expression> m_variables;
Dialect const& m_dialect;
private:
size_t m_varCounter = 0;
};
}