New simplifier via broken expressions.

libyul/optimiser/ExpressionSimplifier.cpp

@@ -22,6 +22,7 @@
 
 #include <libyul/optimiser/SimplificationRules.h>
 #include <libyul/optimiser/Semantics.h>
+#include <libyul/optimiser/SSAValueTracker.h>
 
 #include <libsolidity/inlineasm/AsmData.h>
 
@@ -36,13 +37,24 @@ using namespace dev::solidity;
 void ExpressionSimplifier::visit(Expression& _expression)
 {
 	ASTModifier::visit(_expression);
-	while (auto match = SimplificationRules::findFirstMatch(_expression))
+	while (auto match = SimplificationRules::findFirstMatch(_expression, m_ssaValues))
 	{
 		// Do not apply the rule if it removes non-constant parts of the expression.
 		// TODO: The check could actually be less strict than "movable".
 		// We only require "Does not cause side-effects".
+		// Note: References to variables that are only assigned once are always movable,
+		// so if the value of the variable is not movable, the expression that references
+		// the variable still is.
+
 		if (match->removesNonConstants && !MovableChecker(_expression).movable())
 			return;
 		_expression = match->action().toExpression(locationOf(_expression));
 	}
 }
+
+void ExpressionSimplifier::run(Block& _ast)
+{
+	SSAValueTracker ssaValues;
+	ssaValues(_ast);
+	ExpressionSimplifier{ssaValues.values()}(_ast);
+}