Add memoization to SSAValueTracker::isSSAWithDependencies

Author: rodiazet

libyul/optimiser/SSAValueTracker.cpp

@@ -61,25 +61,38 @@ bool SSAValueTracker::isSSAWithDependencies(Expression const* _expression) const
 	if (_expression == nullptr)
 		return true;
 
+	// Check cache first
+	auto cacheIt = m_isSSACache.find(_expression);
+	if (cacheIt != m_isSSACache.end())
+		return cacheIt->second;
+
+	bool result;
 	if (auto const* functionCall = std::get_if<FunctionCall>(_expression))
 	{
+		result = true;
 		for (auto const& argument: functionCall->arguments)
 			if (!isSSAWithDependencies(&argument))
-				return false;
-
-		return true;
+			{
+				result = false;
+				break;
+			}
 	}
 	else if (auto const* identifier = std::get_if<Identifier>(_expression))
 	{
 		auto const it = m_values.find(identifier->name);
 		if (it == m_values.end())
-			return false;
-		return isSSAWithDependencies(it->second);
+			result = false;
+		else
+			result = isSSAWithDependencies(it->second);
 	}
 	else
+	{
 		solAssert(std::holds_alternative<Literal>(*_expression), "Impossible expression type");
+		result = true;
+	}
 
-	return true;
+	m_isSSACache[_expression] = result;
+	return result;
 }
 
 std::set<YulName> SSAValueTracker::ssaVariables(Block const& _ast)

libyul/optimiser/SSAValueTracker.h

@@ -25,7 +25,7 @@
 #include <libyul/optimiser/ASTWalker.h>
 #include <libyul/AST.h> // Needed for m_zero below.
 
-#include <map>
+#include <unordered_map>
 #include <set>
 
 namespace solidity::yul
@@ -47,7 +47,7 @@ class SSAValueTracker: public ASTWalker
 	void operator()(VariableDeclaration const& _varDecl) override;
 	void operator()(Assignment const& _assignment) override;
 
-	std::map<YulName, Expression const*> const& values() const { return m_values; }
+	std::unordered_map<YulName, Expression const*> const& values() const { return m_values; }
 	Expression const* value(YulName _name) const { return m_values.at(_name); }
 
 	static std::set<YulName> ssaVariables(Block const& _ast);
@@ -62,7 +62,9 @@ class SSAValueTracker: public ASTWalker
 	/// Special expression whose address will be used in m_values.
 	/// YulName does not need to be reset because SSAValueTracker is short-lived.
 	Expression const m_zero{Literal{{}, LiteralKind::Number, LiteralValue(u256{0})}};
-	std::map<YulName, Expression const*> m_values;
+	std::unordered_map<YulName, Expression const*> m_values;
+	/// Cache for isSSAWithDependencies to avoid redundant traversals
+	mutable std::unordered_map<Expression const*, bool> m_isSSACache;
 };
 
 }