On Tue, Mar 31, 2026 at 1:28 PM Zuxy Meng via ffmpeg-devel
<[email protected]> wrote:
>
> From: zuxy <[email protected]>
>
> More about deprecating MMX than any performance gain; nearly identical
> performance numbers on my Zen 4 (1.36x vs c), but llvm-mca predicts
Does the performance gain stem solely from the removal of MMX or from
the addition of SSE2?
> >60% perf gain on Intel CPUs newer than Skylake.
>
> Signed-off-by: Zuxy Meng <[email protected]>
> ---
> libavcodec/x86/h264_intrapred.asm | 44 ++++++++++++----------------
> libavcodec/x86/h264_intrapred_init.c | 9 ++++--
> 2 files changed, 25 insertions(+), 28 deletions(-)
>
> diff --git a/libavcodec/x86/h264_intrapred.asm
> b/libavcodec/x86/h264_intrapred.asm
> index a8a630dbe6..2e4a46ae76 100644
> --- a/libavcodec/x86/h264_intrapred.asm
> +++ b/libavcodec/x86/h264_intrapred.asm
> @@ -606,37 +606,31 @@ INIT_MMX ssse3
> PRED8x8_H
>
>
> ;-----------------------------------------------------------------------------
> -; void ff_pred8x8_top_dc_8_mmxext(uint8_t *src, ptrdiff_t stride)
> +; void ff_pred8x8_top_dc_8_sse2(uint8_t *src, ptrdiff_t stride)
>
> ;-----------------------------------------------------------------------------
> -INIT_MMX mmxext
> +INIT_XMM sse2
> cglobal pred8x8_top_dc_8, 2,5
> sub r0, r1
> - movq mm0, [r0]
> - pxor mm1, mm1
> - pxor mm2, mm2
> + movq xmm0, [r0]
> + pxor xmm1, xmm1
> lea r2, [r0+r1*2]
> - punpckhbw mm1, mm0
> - punpcklbw mm0, mm2
> - psadbw mm1, mm2 ; s1
> + punpcklbw xmm0, xmm1
> + psadbw xmm0, xmm1 ; s0,0,0,0,s1,0,0,0 (w)
> lea r3, [r2+r1*2]
> - psadbw mm0, mm2 ; s0
> - psrlw mm1, 1
> - psrlw mm0, 1
> - pavgw mm1, mm2
> - lea r4, [r3+r1*2]
> - pavgw mm0, mm2
> - pshufw mm1, mm1, 0
> - pshufw mm0, mm0, 0 ; dc0 (w)
> - packuswb mm0, mm1 ; dc0,dc1 (b)
> - movq [r0+r1*1], mm0
> - movq [r0+r1*2], mm0
> + psrlw xmm0, 1
> + pavgw xmm0, xmm1
> + pshuflw xmm0, xmm0, 0 ; dc0,dc0,dc0,dc0,dc1,0,0,0
> + pshufhw xmm0, xmm0, 0 ; dc0,dc1 (w)
> + packuswb xmm0, xmm1 ; dc0,dc1 (b)
> + movq [r0+r1*1], xmm0
> + movq [r0+r1*2], xmm0
> lea r0, [r3+r1*2]
> - movq [r2+r1*1], mm0
> - movq [r2+r1*2], mm0
> - movq [r3+r1*1], mm0
> - movq [r3+r1*2], mm0
> - movq [r0+r1*1], mm0
> - movq [r0+r1*2], mm0
> + movq [r2+r1*1], xmm0
> + movq [r2+r1*2], xmm0
> + movq [r3+r1*1], xmm0
> + movq [r3+r1*2], xmm0
> + movq [r0+r1*1], xmm0
> + movq [r0+r1*2], xmm0
> RET
>
>
> ;-----------------------------------------------------------------------------
> diff --git a/libavcodec/x86/h264_intrapred_init.c
> b/libavcodec/x86/h264_intrapred_init.c
> index aa9bc721f0..0476980a57 100644
> --- a/libavcodec/x86/h264_intrapred_init.c
> +++ b/libavcodec/x86/h264_intrapred_init.c
> @@ -113,7 +113,7 @@ PRED16x16(plane_svq3, 8, ssse3)
> PRED16x16(tm_vp8, 8, sse2)
> PRED16x16(tm_vp8, 8, avx2)
>
> -PRED8x8(top_dc, 8, mmxext)
> +PRED8x8(top_dc, 8, sse2)
> PRED8x8(dc_rv40, 8, mmxext)
> PRED8x8(dc, 8, mmxext)
> PRED8x8(vertical, 8, sse2)
> @@ -187,7 +187,6 @@ av_cold void ff_h264_pred_init_x86(H264PredContext *h,
> int codec_id,
> }
> if (codec_id == AV_CODEC_ID_SVQ3 || codec_id ==
> AV_CODEC_ID_H264) {
> if (chroma_format_idc <= 1) {
> - h->pred8x8[TOP_DC_PRED8x8 ] =
> ff_pred8x8_top_dc_8_mmxext;
> h->pred8x8[DC_PRED8x8 ] = ff_pred8x8_dc_8_mmxext;
> }
> }
> @@ -210,8 +209,12 @@ av_cold void ff_h264_pred_init_x86(H264PredContext *h,
> int codec_id,
> h->pred8x8l [VERT_RIGHT_PRED ] =
> ff_pred8x8l_vertical_right_8_sse2;
> h->pred8x8l [VERT_LEFT_PRED ] =
> ff_pred8x8l_vertical_left_8_sse2;
> h->pred8x8l [HOR_DOWN_PRED ] =
> ff_pred8x8l_horizontal_down_8_sse2;
> - if (chroma_format_idc <= 1)
> + if (chroma_format_idc <= 1) {
> h->pred8x8 [VERT_PRED8x8 ] = ff_pred8x8_vertical_8_sse2;
> + if (codec_id == AV_CODEC_ID_SVQ3 || codec_id ==
> AV_CODEC_ID_H264) {
> + h->pred8x8 [TOP_DC_PRED8x8] = ff_pred8x8_top_dc_8_sse2;
> + }
> + }
> if (codec_id == AV_CODEC_ID_VP7 || codec_id == AV_CODEC_ID_VP8) {
> h->pred16x16[PLANE_PRED8x8 ] = ff_pred16x16_tm_vp8_8_sse2;
> h->pred8x8 [PLANE_PRED8x8 ] = ff_pred8x8_tm_vp8_8_sse2;
> --
> 2.43.0
_______________________________________________
ffmpeg-devel mailing list -- [email protected]
To unsubscribe send an email to [email protected]
