[FFmpeg-devel] [PATCH 7/9] sbcenc: add MMX optimizations

[James Almer]

On 12/23/2017 3:01 PM, Aurelien Jacobs wrote:
> This was originally based on libsbc, and was fully integrated into ffmpeg.
> 
> Rough speed test:
> C version:    speed= 592x
> MMX version:  speed= 785x
> ---
>  libavcodec/sbcdsp.c          |   3 +
>  libavcodec/sbcdsp.h          |   2 +
>  libavcodec/x86/Makefile      |   2 +
>  libavcodec/x86/sbcdsp.asm    | 284 +++++++++++++++++++++++++++++++++++++++++++
>  libavcodec/x86/sbcdsp_init.c |  51 ++++++++
>  5 files changed, 342 insertions(+)
>  create mode 100644 libavcodec/x86/sbcdsp.asm
>  create mode 100644 libavcodec/x86/sbcdsp_init.c

[...]

> +;*******************************************************************
> +;void ff_sbc_calc_scalefactors(int32_t sb_sample_f[16][2][8],
> +;                              uint32_t scale_factor[2][8],
> +;                              int blocks, int channels, int subbands)
> +;*******************************************************************
> +INIT_MMX mmx
> +cglobal sbc_calc_scalefactors, 5, 7, 3, sb_sample_f, scale_factor, blocks, channels, subbands, ptr, blk
> +    ; subbands = 4 * subbands * channels
> +    shl  subbandsd, 2
> +    cmp  channelsd, 2
> +    jl   .loop_1
> +    shl  subbandsd, 1
> +
> +.loop_1:
> +    sub           subbandsq, 8
> +    lea           ptrq, [sb_sample_fq + subbandsq]
> +
> +    ; blk = (blocks - 1) * 64;
> +    lea           blkq, [blocksq - 1]
> +    shl           blkd, 6
> +
> +    movq          m0, [scale_mask]

I insist, this can be easily loaded outside the loop. You have enough
spare regs to store a copy.

In any case, the patch looks good regardless of the above.