[Bug target/94687] PPC vector fails to optimize shift (used bits)

[shawn at git dot icu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94687

--- Comment #2 from Shawn Landden <shawn at git dot icu> ---
LLVM fixed this by lowering to vector shuffle: https://dev.gnupg.org/D501