List<LogicalVariable> used = new ArrayList<LogicalVariable>();
VariableUtilities.getUsedVariables(op1, used);
Mutable<ILogicalOperator> b0Ref = op2.getInputs().get(0);
ILogicalOperator b0 = b0Ref.getValue();
List<LogicalVariable> b0Scm = new ArrayList<LogicalVariable>();
VariableUtilities.getLiveVariables(b0, b0Scm);
if (b0Scm.containsAll(used)) {
// push assign on left branch
op2Ref.setValue(b0);
b0Ref.setValue(op1);
opRef.setValue(op2);
return true;
} else {
Mutable<ILogicalOperator> b1Ref = op2.getInputs().get(1);
ILogicalOperator b1 = b1Ref.getValue();
List<LogicalVariable> b1Scm = new ArrayList<LogicalVariable>();
VariableUtilities.getLiveVariables(b1, b1Scm);
if (b1Scm.containsAll(used)) {
// push assign on right branch
op2Ref.setValue(b1);