Use rematerializer if variable is unreferenced or value is "cheap".

libyul/optimiser/Metrics.cpp

@@ -21,6 +21,9 @@
 #include <libyul/optimiser/Metrics.h>
 
 #include <libyul/AsmData.h>
+#include <libyul/Exceptions.h>
+
+#include <libevmasm/Instruction.h>
 
 using namespace dev;
 using namespace yul;
@@ -60,3 +63,64 @@ void CodeSize::visit(Expression const& _expression)
 	++m_size;
 	ASTWalker::visit(_expression);
 }
+
+
+size_t CodeCost::codeCost(Expression const& _expr)
+{
+	CodeCost cc;
+	cc.visit(_expr);
+	return cc.m_cost;
+}
+
+
+void CodeCost::operator()(FunctionCall const& _funCall)
+{
+	yulAssert(m_cost >= 1, "Should assign cost one in visit(Expression).");
+	m_cost += 49;
+	ASTWalker::operator()(_funCall);
+}
+
+void CodeCost::operator()(FunctionalInstruction const& _instr)
+{
+	using namespace dev::solidity;
+	yulAssert(m_cost >= 1, "Should assign cost one in visit(Expression).");
+	Tier gasPriceTier = instructionInfo(_instr.instruction).gasPriceTier;
+	if (gasPriceTier < Tier::VeryLow)
+		m_cost -= 1;
+	else if (gasPriceTier < Tier::High)
+		m_cost += 1;
+	else
+		m_cost += 49;
+	ASTWalker::operator()(_instr);
+}
+void CodeCost::operator()(Literal const& _literal)
+{
+	yulAssert(m_cost >= 1, "Should assign cost one in visit(Expression).");
+	size_t cost = 0;
+	switch (_literal.kind)
+	{
+	case LiteralKind::Boolean:
+		break;
+	case LiteralKind::Number:
+		for (u256 n = u256(_literal.value.str()); n >= 0x100; n >>= 8)
+			cost++;
+		break;
+	case LiteralKind::String:
+		cost = _literal.value.str().size();
+		break;
+	}
+
+	m_cost += cost;
+}
+
+void CodeCost::visit(Statement const& _statement)
+{
+	++m_cost;
+	ASTWalker::visit(_statement);
+}
+
+void CodeCost::visit(Expression const& _expression)
+{
+	++m_cost;
+	ASTWalker::visit(_expression);
+}