[Bug target/96918] Failure to optimize vector shift left+shift right+or to pshuf

[crazylht at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96918

--- Comment #9 from Hongtao.liu <crazylht at gmail dot com> ---
Or the backend add combine helper insn to match

Failed to match this instruction:
(set (reg:V8HI 90)
    (rotate:V8HI (reg:V8HI 91)
        (const_int 8 [0x8])))