[Bug target/104315] [AArch64] Failure to optimize 8-bit bitreverse pattern

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104315

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
generalizing the bswap detection to track bits instead of bytes might be a way
to handle this (there's the related issue of us failing to "copy propagate"
bits
with the associated possible simplifications on users of such propagated bits).