[Bug target/88461] AVX512: gcc should keep value in kN registers if possible

[bugzi...@poradnik-webmastera.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88461

--- Comment #1 from Daniel Fruzynski <bugzi...@poradnik-webmastera.com> ---
For comparison, this is code generated by icc 19.0.1:

[asm]
test(unsigned short*, int):
        vmovdqu   xmm0, XMMWORD PTR [rdi]                       #6.48
        vptestnmw k0, xmm0, xmm0                                #7.18
        kmovw     k2, esi                                       #11.9
        kshiftlw  k1, k0, 1                                     #9.9
        kandnw    k3, k1, k2                                    #11.9
        kmovb     k4, k3                                        #13.12
        kmovw     eax, k4                                       #13.12
        ret                                                     #13.12
[/asm]