IAVF_FILTER_ADD
f->flags |= (IAVF_FILTER_ADD | IAVF_FILTER_USED);
v->flags = IAVF_FILTER_ADD;
if (f->flags & IAVF_FILTER_ADD)
if (f->flags & IAVF_FILTER_ADD) {
if (f->flags & IAVF_FILTER_ADD)
if (f->flags & IAVF_FILTER_ADD) {
f->flags &= ~IAVF_FILTER_ADD;