Gas meter for Yul expressions.

libyul/optimiser/Metrics.cpp

@@ -22,10 +22,13 @@
 
 #include <libyul/AsmData.h>
 #include <libyul/Exceptions.h>
+#include <libyul/Utilities.h>
 
 #include <libevmasm/Instruction.h>
+#include <libevmasm/GasMeter.h>
 
 #include <libdevcore/Visitor.h>
+#include <libdevcore/CommonData.h>
 
 using namespace std;
 using namespace dev;
@@ -151,6 +154,54 @@ void CodeCost::visit(Expression const& _expression)
 	ASTWalker::visit(_expression);
 }
 
+pair<size_t, size_t> GasMeter::gasCosts(
+	Expression const& _expression,
+	langutil::EVMVersion _evmVersion,
+	bool _isCreation
+)
+{
+	GasMeter gm(_evmVersion, _isCreation);
+	gm.visit(_expression);
+	return {gm.m_runGas, gm.m_dataGas};
+}
+
+void GasMeter::operator()(FunctionCall const&)
+{
+	yulAssert(false, "Functions not implemented.");
+}
+
+void GasMeter::operator()(FunctionalInstruction const& _fun)
+{
+	ASTWalker::operator()(_fun);
+	if (_fun.instruction == eth::Instruction::EXP)
+		m_runGas += dev::eth::GasCosts::expGas + dev::eth::GasCosts::expByteGas(m_evmVersion);
+	else
+		m_runGas += dev::eth::GasMeter::runGas(_fun.instruction);
+	m_dataGas += singleByteDataGas();
+}
+
+void GasMeter::operator()(Literal const& _lit)
+{
+	m_runGas += dev::eth::GasMeter::runGas(dev::eth::Instruction::PUSH1);
+	m_dataGas +=
+		singleByteDataGas() +
+		size_t(dev::eth::GasMeter::dataGas(dev::toCompactBigEndian(valueOfLiteral(_lit), 1), m_isCreation));
+}
+
+void GasMeter::operator()(Identifier const&)
+{
+	m_runGas += dev::eth::GasMeter::runGas(dev::eth::Instruction::DUP1);
+	m_dataGas += singleByteDataGas();
+}
+
+size_t GasMeter::singleByteDataGas() const
+{
+	if (m_isCreation)
+		return dev::eth::GasCosts::txDataNonZeroGas;
+	else
+		return dev::eth::GasCosts::createDataGas;
+}
+
 void AssignmentCounter::operator()(Assignment const& _assignment)
 {
 	for (auto const& variable: _assignment.variableNames)

libyul/optimiser/Metrics.h

@@ -21,6 +21,7 @@
 #pragma once
 
 #include <libyul/optimiser/ASTWalker.h>
+#include <liblangutil/EVMVersion.h>
 
 namespace yul
 {
@@ -84,6 +85,42 @@ private:
 	size_t m_cost = 0;
 };
 
+/**
+ * Gas meter for expressions only involving literals, identifiers and
+ * EVM instructions.
+ *
+ * Assumes that EXP is not used with exponents larger than a single byte.
+ */
+class GasMeter: public ASTWalker
+{
+public:
+	/// @returns the runtime costs and the data cost of
+	/// evaluating the given expression.
+	static std::pair<size_t, size_t> gasCosts(
+		Expression const& _expression,
+		langutil::EVMVersion _evmVersion,
+		bool _isCreation = false
+	);
+
+private:
+	GasMeter(langutil::EVMVersion _evmVersion, bool _isCreation):
+		m_evmVersion(_evmVersion),
+		m_isCreation{_isCreation}
+	{}
+
+	void operator()(FunctionCall const& _funCall) override;
+	void operator()(FunctionalInstruction const& _instr) override;
+	void operator()(Literal const& _literal) override;
+	void operator()(Identifier const& _identifier) override;
+
+private:
+	size_t singleByteDataGas() const;
+
+	langutil::EVMVersion m_evmVersion;
+	bool m_isCreation = false;
+	size_t m_runGas = 0;
+	size_t m_dataGas = 0;
+};
 /**
  * Counts the number of assignments to every variable.
  * Only works after running the Disambiguator.