question: public void insertPushNull ( int opcode , JumpInsnNode position , InsnList list ) { int branchId = getBranchID ( currentMethodNode , position ) ; logger . info ( "Inserting instrumentation for NULL check at branch " + branchId + " in method " + currentMethodNode . name ) ; MethodInsnNode nullCheck = new MethodInsnNode ( Opcodes . INVOKESTATIC , Type . getInternalName ( BooleanHelper . class ) , "isNull" , Type . getMethodDescriptor ( Type . INT_TYPE , new Type [ ] { Type . getType ( Object . class ) , Type . INT_TYPE } ) , false ) ; list . insertBefore ( position , new InsnNode ( Opcodes . DUP ) ) ; list . insertBefore ( position , new LdcInsnNode ( opcode ) ) ; list . insertBefore ( position , nullCheck ) ; insertBranchIdPlaceholder ( currentMethodNode , position , branchId ) ; MethodInsnNode push = new MethodInsnNode ( Opcodes . INVOKESTATIC , Type . getInternalName ( BooleanHelper . class ) , "pushPredicate" , Type . getMethodDescriptor ( Type . VOID_TYPE , new Type [ ] { Type . INT_TYPE , Type . INT_TYPE } ) , false ) ; list . insertBefore ( position , push ) ; }
target:  Insert a call to the isNull helper function