[Bug c++/98461] Suboptimal codegen for negating a movemask

[crazylht at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98461

--- Comment #1 from Hongtao.liu <crazylht at gmail dot com> ---
in rtl phase, gcc successfully simplify 
(and:V4DI (not:V4DI (reg:V4DI 91)) 
          (constm1_rtx)
to

(not:V4DI (reg:V4DI 91)).

But combine failed to match 

(set (reg:SI 88)
    (unspec:SI [
            (subreg:V32QI (not:V4DI (reg:V4DI 91)) 0)
        ] UNSPEC_MOVMSK))

So add combine splitter?