[FFmpeg-devel] [PATCH] RFC: v210enc optimisations and initial AVX-512

[Henrik Gramner]

On Fri, Oct 21, 2022 at 5:41 AM Kieran Kunhya <kierank at obe.tv> wrote:
>
> Hi,
>
> Please see attached an attempt to optimise the 8-bit input to v210enc to
> reduce the number of shuffles.
> This comes at the cost of having to extract the middle element and perform
> a DWORD shift on it and then reinserting it.
> I have added a few comments but any other ideas are welcome.

Random untested idea:

A: db 32,  0, 48, -1,  1, 33,  2, -1, 49,  3, 34, -1,  4, 50,  5, -1
   db 35,  6, 51, -1,  7, 36,  8, -1, 52,  9, 37, -1, 10, 53, 11, -1
   db 38, 12, 54, -1, 13, 39, 14, -1, 55, 15, 40, -1, 16, 56, 17, -1
   db 41, 18, 57, -1, 19, 42, 20, -1, 58, 21, 43, -1, 22, 59, 23, -1
B: db  1,  0, 16,  0
C: dd 0x0003fc00

[...]

mova              m2, [A]
vpbroadcastd      m3, [B]
vpbroadcastd      m6, [C]

[...]

.loop:
    movu         ym1, [yq]
    vinserti32x4  m1, [uq], 2
    vinserti32x4  m1, [vq], 3
    CLIPUB        m1, m4, m5
    vpermb        m1, m2, m1
    pmaddubsw     m0, m1, m3
    pslld         m1, 2
    vpternlogd    m0, m1, m6, 0xca
    movu      [dstq], m0

I guess it could also be scaled to ymm if you're a big Skylake fan :P
(in which case you'd probably want to reorder the shuffle indices so
that chroma comes first, i.e. movq [u] + movhps [v] + vinserti32x4
[y])