[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 #2 from Hongtao.liu <crazylht at gmail dot com> ---
Microbenchmark show on Skylake client
---
benchmark       Skylake client          
ashift          improvement
v16qi           13%
v32qi           5%
v64qi           7%

ashiftrt        
v16qi           5%
v32qi           7%
v64qi           6%

lshiftrt        
v16qi           16%
v32qi           13%
v64qi           6%
---