Removing scope rules for pre block in 'For Loops'

libyul/optimiser/CommonSubexpressionEliminator.h

@@ -32,7 +32,7 @@ struct Dialect;
  * Optimisation stage that replaces expressions known to be the current value of a variable
  * in scope by a reference to that variable.
  *
- * Prerequisite: Disambiguator
+ * Prerequisite: Disambiguator, ForLoopInitRewriter.
  */
 class CommonSubexpressionEliminator: public DataFlowAnalyzer
 {

libyul/optimiser/DataFlowAnalyzer.cpp

@@ -112,10 +112,9 @@ void DataFlowAnalyzer::operator()(FunctionDefinition& _fun)
 
 void DataFlowAnalyzer::operator()(ForLoop& _for)
 {
-	// Special scope handling of the pre block.
-	pushScope(false);
-	for (auto& statement: _for.pre.statements)
-		visit(statement);
+	// If the pre block was not empty,
+	// we would have to deal with more complicated scoping rules.
+	assertThrow(_for.pre.statements.empty(), OptimizerException, "");
 
 	AssignmentsSinceContinue assignmentsSinceCont;
 	assignmentsSinceCont(_for.body);
@@ -130,8 +129,6 @@ void DataFlowAnalyzer::operator()(ForLoop& _for)
 	clearValues(assignmentsSinceCont.names());
 	(*this)(_for.post);
 	clearValues(assignments.names());
-
-	popScope();
 }
 
 void DataFlowAnalyzer::operator()(Block& _block)

libyul/optimiser/DataFlowAnalyzer.h

@@ -39,7 +39,7 @@ struct Dialect;
  *
  * A special zero constant expression is used for the default value of variables.
  *
- * Prerequisite: Disambiguator
+ * Prerequisite: Disambiguator, ForLoopInitRewriter.
  */
 class DataFlowAnalyzer: public ASTModifier
 {

libyul/optimiser/ExpressionSimplifier.h

@@ -36,7 +36,7 @@ struct Dialect;
  * It tracks the current values of variables using the DataFlowAnalyzer
  * and takes them into account for replacements.
  *
- * Prerequisite: Disambiguator.
+ * Prerequisite: Disambiguator, ForLoopInitRewriter.
  */
 class ExpressionSimplifier: public DataFlowAnalyzer
 {

libyul/optimiser/RedundantAssignEliminator.cpp

@@ -118,12 +118,9 @@ void RedundantAssignEliminator::operator()(ForLoop const& _forLoop)
 	ForLoopInfo outerForLoopInfo;
 	swap(outerForLoopInfo, m_forLoopInfo);
 
-	set<YulString> outerDeclaredVariables;
-	swap(m_declaredVariables, outerDeclaredVariables);
-
-	// We need to visit the statements directly because of the
-	// scoping rules.
-	walkVector(_forLoop.pre.statements);
+	// If the pre block was not empty,
+	// we would have to deal with more complicated scoping rules.
+	assertThrow(_forLoop.pre.statements.empty(), OptimizerException, "");
 
 	// We just run the loop twice to account for the
 	// back edge.
@@ -156,10 +153,6 @@ void RedundantAssignEliminator::operator()(ForLoop const& _forLoop)
 	merge(m_assignments, move(m_forLoopInfo.pendingBreakStmts));
 	m_forLoopInfo.pendingBreakStmts.clear();
 
-	for (auto const& var: m_declaredVariables)
-		finalize(var, State::Unused);
-	swap(m_declaredVariables, outerDeclaredVariables);
-
 	// Restore potential outer for-loop states.
 	swap(m_forLoopInfo, outerForLoopInfo);
 }

libyul/optimiser/RedundantAssignEliminator.h

@@ -95,7 +95,7 @@ struct Dialect;
  * This step is usually run right after the SSA transform to complete
  * the generation of the pseudo-SSA.
  *
- * Prerequisite: Disambiguator.
+ * Prerequisite: Disambiguator, ForLoopInitRewriter.
  */
 class RedundantAssignEliminator: public ASTWalker
 {

libyul/optimiser/Rematerialiser.h

@@ -33,7 +33,7 @@ namespace yul
  *  - the variable is referenced at most 5 times and the value is rather cheap
  *    ("cost" of at most 1 like a constant up to 0xff)
  *
- * Prerequisite: Disambiguator
+ * Prerequisite: Disambiguator, ForLoopInitRewriter.
  */
 class Rematerialiser: public DataFlowAnalyzer
 {

libyul/optimiser/StructuralSimplifier.h

@@ -36,7 +36,7 @@ namespace yul
  * - replace switch with const expr with matching case body
  * - replace for with false condition by its initialization part
  *
- * Prerequisites: Disambiguator
+ * Prerequisite: Disambiguator, ForLoopInitRewriter.
  *
  * Important: Can only be used on EVM code.
  */