[Bug target/104371] [x86] Failure to use optimize pxor+pcmpeqb+pmovmskb+cmp 0xFFFF pattern to ptest

[crazylht at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104371

--- Comment #4 from Hongtao.liu <crazylht at gmail dot com> ---
Failed to match this instruction:
(set (reg:CCZ 17 flags)
    (compare:CCZ (unspec:SI [
                (eq:V16QI (subreg:V16QI (reg:V2DI 94) 0)
                    (const_vector:V16QI [
                            (const_int 0 [0]) repeated x16
                        ]))
            ] UNSPEC_MOVMSK)
        (const_int 65535 [0xffff])))

This can be optimized to ptest as long as only CCZ is cared.