semantic-tag-file-name
semantic-tag-file-name is a compiled Lisp function in `tag.el
'.
(semantic-tag-file-name TAG)
Return the name of the file from which TAG originated.
Return nil if that information can't be obtained.
If TAG is from a loaded buffer, then that buffer's filename is used.
If TAG is unlinked, but has a :filename property, then that is used.