[FFmpeg-devel] [PATCH] avfilter: add hflip x86 SIMD

[Paul B Mahol]

On 12/3/17, Martin Vignali <martin.vignali at gmail.com> wrote:
>>
>> In any case, if clang or gcc can generate better code, then the hand
>> written version needs to be optimized to be as fast or faster.
>>
>>
>>
> Quick test : pass checkasm (but probably only because width = 256)
> hflip_byte_c: 26.4
> hflip_byte_ssse3: 20.4
>
>
> INIT_XMM ssse3
> cglobal hflip_byte, 3, 5, 2, src, dst, w, x, v, src2
>     mova    m0, [pb_flip_byte]
>     xor     xq, xq ; <======
>     mov     wd, dword wm
>     sub     wq, mmsize * 2
> ;remove the cmp here <======
>     jl .skip
>
>     .loop0: ; process two xmm in the loop
>         neg     xq
>         movu    m1, [srcq + xq - mmsize + 1]
>         movu    m2, [srcq + xq - mmsize * 2 + 1] <======
>         pshufb  m1, m0
>         pshufb  m2, m0 <======
>         neg     xq
>         movu    [dstq + xq], m1
>         movu    [dstq + xq + mmsize], m2 <======
>         add     xq, mmsize * 2 <======
>         cmp     xq, wq
>         jl .loop0
>      RET ; add RET here
>
> ; MISSING one xmm process if need
>
> .skip:
>     add     wq, mmsize
>     .loop1:
>         neg    xq
>         mov    vb, [srcq + xq]
>         neg    xq
>         mov    [dstq + xq], vb
>         add    xq, 1
>         cmp    xq, wq
>         jl .loop1
> RET

So what is wrong now?