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

[Aurelien Jacobs]

On Sat, Dec 23, 2017 at 09:52:11PM +0100, Aurelien Jacobs wrote:
> On Sat, Dec 23, 2017 at 05:47:04PM -0300, James Almer wrote:
> > On 12/23/2017 5:44 PM, Aurelien Jacobs wrote:
> > > On Sat, Dec 23, 2017 at 03:35:28PM -0300, James Almer wrote:
> > >> 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.
> > > 
> > > Oh, I forgot to reply to this. There isn't any register left available
> > > on x86_32, hence why I kept those load inside the loop.
> > 
> > You're not using a gprs to store the mask nor need to. You're using mmx
> > regs and have 5 left.
> 
> Oh, indeed ! Not sure why it didn't even cross my mind...
> I will have a look at this.

Here it is with the scale_mask load out of the loop.

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