[Bug target/95524] Subtimal codegen for shift by constant for v16qi/v32qi under -march=skylake

[crazylht at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95524

--- Comment #1 from Hongtao.liu <crazylht at gmail dot com> ---
Microbenchmark show

interleave_ashiftrt : 69023847
magic_ashiftrt :      62488066

Seems 10% improvement.