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Implement knowledge base.

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chriseth
2019-06-20 18:43:37 +02:00
parent 1f9d11c644
commit 8572600401
3 changed files with 90 additions and 5 deletions
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libyul/optimiser/KnowledgeBase.cpp
+60 -3
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@@ -20,12 +20,69 @@
#include <libyul/optimiser/KnowledgeBase.h>
using namespace yul;
#include <libyul/AsmData.h>
#include <libyul/Utilities.h>
#include <libyul/optimiser/SimplificationRules.h>
#include <libyul/optimiser/Semantics.h>
bool KnowledgeBase::knownToBeDifferent(YulString, YulString) const
#include <libdevcore/CommonData.h>
using namespace yul;
using namespace dev;
bool KnowledgeBase::knownToBeDifferent(YulString _a, YulString _b)
{
// TODO try to use the simplification rules together with the
// Try to use the simplification rules together with the
// current values to turn `sub(_a, _b)` into a nonzero constant.
// If that fails, try `eq(_a, _b)`.
Expression expr1 = simplify(FunctionCall{{}, {{}, "sub"_yulstring}, make_vector<Expression>(Identifier{{}, _a}, Identifier{{}, _b})});
if (expr1.type() == typeid(Literal))
return valueOfLiteral(boost::get<Literal>(expr1)) != 0;
Expression expr2 = simplify(FunctionCall{{}, {{}, "eq"_yulstring}, make_vector<Expression>(Identifier{{}, _a}, Identifier{{}, _b})});
if (expr2.type() == typeid(Literal))
return valueOfLiteral(boost::get<Literal>(expr2)) == 0;
return false;
}
bool KnowledgeBase::knownToBeDifferentByAtLeast32(YulString _a, YulString _b)
{
// Try to use the simplification rules together with the
// current values to turn `sub(_a, _b)` into a constant whose absolute value is at least 32.
Expression expr1 = simplify(FunctionCall{{}, {{}, "sub"_yulstring}, make_vector<Expression>(Identifier{{}, _a}, Identifier{{}, _b})});
if (expr1.type() == typeid(Literal))
{
u256 val = valueOfLiteral(boost::get<Literal>(expr1));
return val >= 32 && val <= u256(0) - 32;
}
return false;
}
Expression KnowledgeBase::simplify(Expression _expression)
{
bool startedRecursion = (m_recursionCounter == 0);
dev::ScopeGuard{[&] { if (startedRecursion) m_recursionCounter = 0; }};
if (startedRecursion)
m_recursionCounter = 100;
else if (m_recursionCounter == 1)
return _expression;
else
--m_recursionCounter;
if (_expression.type() == typeid(FunctionCall))
for (Expression& arg: boost::get<FunctionCall>(_expression).arguments)
arg = simplify(arg);
else if (_expression.type() == typeid(FunctionalInstruction))
for (Expression& arg: boost::get<FunctionalInstruction>(_expression).arguments)
arg = simplify(arg);
if (auto match = SimplificationRules::findFirstMatch(_expression, m_dialect, m_variableValues))
return simplify(match->action().toExpression(locationOf(_expression)));
return _expression;
}