[Bug target/84524] -O3 causes behavior change

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84524

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
It reproduces even with __attribute__((noipa)) on foo, so the problem is just
in that function.  In assembly we can see:
        vpsllw  $8, %zmm6, %zmm5
        addq    $64, %rdi
        vpmovzxwd       %ymm5, %zmm0
        vpcmpgtw        %zmm5, %zmm2, %k1
        vpslld  $1, %zmm0, %zmm1
        vextracti64x4   $0x1, %zmm5, %ymm0
        vpmovzxwd       %ymm0, %zmm0
        vpslld  $1, %zmm0, %zmm0
        vpermt2w        %zmm0, %zmm4, %zmm1
        vpsllw  $9, %zmm6, %zmm0
        vpaddw  %zmm7, %zmm6, %zmm6
        vpxorq  %zmm3, %zmm1, %zmm0
        vpmovzxwd       %ymm0, %zmm1
        vpcmpgtw        %zmm0, %zmm2, %k1
        vpslld  $1, %zmm1, %zmm5
        vextracti64x4   $0x1, %zmm0, %ymm1
the compares into %k1 are useless, nothing really uses the %k1 afterwards, but
it should be used for conditional moves (the cond ? (v << 1) ^ 0x1021 : (v <<
9)
conditional moves).  Looking into this.