https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122751
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> --- My view was always that we want bswap-pass like analysis of 'bytes' also in vectors and then pattern-match useful alterations. Of course the bswap analysis does not represent 'sign-extend' at the moment. There's also the symbolic execution stuff.
