alloc_tree_mod_elem
tm = alloc_tree_mod_elem(eb, slot, op);
tm_list[i] = alloc_tree_mod_elem(eb, i + dst_slot,
tm_list[i] = alloc_tree_mod_elem(old_root, i,
tm_list_rem[i] = alloc_tree_mod_elem(src, i + src_offset,
tm_list_add[i] = alloc_tree_mod_elem(dst, i + dst_offset,
tm_list[i] = alloc_tree_mod_elem(eb, i,