[FFmpeg-devel] [PATCH] lavc/vp8dsp: R-V V put_bilin_h v unroll

[Rémi Denis-Courmont]

Le torstaina 30. toukokuuta 2024, 18.26.53 EEST uk7b at foxmail.com a écrit :
> From: sunyuechi <sunyuechi at iscas.ac.cn>
> 
> Since len < 64, the registers are sufficient, so it can be
> directly unrolled (a4 is even).
> 
> Another benefit of unrolling is that it reduces one load operation
> vertically compared to horizontally.
> 
>                                  old                 new
>                              C908   X60          C908   X60
> vp8_put_bilin4_h_c         :    6.2    5.5     :    6.2    5.5
> vp8_put_bilin4_h_rvv_i32   :    2.2    2.0     :    1.5    1.5
> vp8_put_bilin4_v_c         :    6.5    5.7     :    6.2    5.7
> vp8_put_bilin4_v_rvv_i32   :    2.2    2.0     :    1.2    1.5
> vp8_put_bilin8_h_c         :   24.2   21.5     :   24.2   21.5
> vp8_put_bilin8_h_rvv_i32   :    5.2    4.7     :    3.5    3.5
> vp8_put_bilin8_v_c         :   24.5   21.7     :   24.5   21.7
> vp8_put_bilin8_v_rvv_i32   :    5.2    4.7     :    3.5    3.2
> vp8_put_bilin16_h_c        :   48.0   42.7     :   48.0   42.7
> vp8_put_bilin16_h_rvv_i32  :    5.7    5.0     :    5.2    4.5
> vp8_put_bilin16_v_c        :   48.2   43.0     :   48.2   42.7
> vp8_put_bilin16_v_rvv_i32  :    5.7    5.2     :    4.5    4.2
> ---
>  libavcodec/riscv/vp8dsp_rvv.S | 34 +++++++++++++++++++++++++++++-----
>  1 file changed, 29 insertions(+), 5 deletions(-)
> 
> diff --git a/libavcodec/riscv/vp8dsp_rvv.S b/libavcodec/riscv/vp8dsp_rvv.S
> index 3360a38cac..5bea6cba9c 100644
> --- a/libavcodec/riscv/vp8dsp_rvv.S
> +++ b/libavcodec/riscv/vp8dsp_rvv.S
> @@ -172,11 +172,35 @@ func ff_put_vp8_bilin4_\type\()_rvv, zve32x
>          li              t4, 4
>          sub             t1, t1, \mn
>  1:
> -        addi            a4, a4, -1
> -        bilin_load      v0, \type, \mn

Does this not render the type parameter of bilin_load useless (always h)?
(Not a blocker for this patch.)

> -        vse8.v          v0, (a0)
> -        add             a2, a2, a3
> -        add             a0, a0, a1
> +        add             t0, a2, a3
> +        add             t2, a0, a1
> +        addi            a4, a4, -2
> +.ifc \type,v
> +        add             t3, t0, a3
> +.else
> +        addi            t5, a2, 1
> +        addi            t3, t0, 1
> +        vle8.v          v2, (t5)

Not sure if I already asked this but is this really faster than slide1? 
Normally we want to minimise the work of the memory bus.

> +.endif
> +        vle8.v          v0, (a2)
> +        vle8.v          v4, (t0)
> +        vle8.v          v6, (t3)
> +        vwmulu.vx       v28, v0, t1
> +        vwmulu.vx       v26, v4, t1
> +.ifc \type,v
> +        vwmaccu.vx      v28, \mn, v4
> +.else
> +        vwmaccu.vx      v28, \mn, v2
> +.endif
> +        vwmaccu.vx      v26, \mn, v6
> +        vwaddu.wx       v24, v28, t4
> +        vwaddu.wx       v22, v26, t4
> +        vnsra.wi        v30, v24, 3
> +        vnsra.wi        v0, v22, 3
> +        vse8.v          v30, (a0)
> +        vse8.v          v0, (t2)
> +        add             a2, t0, a3
> +        add             a0, t2, a1
>          bnez            a4, 1b
> 
>          ret

-- 
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