[Bug target/65407] New: Extra mask register move in gcc.target/i386/avx512f-kandnw-1.c

["ubizjak at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65407

            Bug ID: 65407
           Summary: Extra mask register move in
                    gcc.target/i386/avx512f-kandnw-1.c
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ubizjak at gmail dot com

The compilation generates extra mask register move (kmov) when compiling
gcc.target/i386/avx512f-kandnw-1.c on x86_64-linux-gnu with

-O2 -mavx512f:

...
        vmovaps %zmm0, -112(%rbp)
>>      kandnw  %k1, %k0, %k0
>>      kmovw   %k0, %k2
        vmovaps -112(%rbp), %zmm1
        vmovaps -112(%rbp), %zmm2
        vmovaps -112(%rbp), %zmm0
        vaddps  %zmm1, %zmm2, %zmm0{%k2}
...

The register allocator could simply generate:

        kandnw  %k1, %k0, %k2

instead of the above two marked insns.