Re: [FFmpeg-devel] [PATCH 3/6] lavc/ac3dsp: RISC-V V ac3_sum_square_butterfly_int32

["Rémi Denis-Courmont" <remi@remlab.net>]

Le torstaina 15. kesäkuuta 2023, 13.36.42 EEST Peiting Shen a écrit :
> From: Shen Peiting <shenpeiting@eswincomputing.com>
> 
> Scalar calculating int32 sum_square optimized by using RVV instructions
> 
> Benchmarks on Spike(cycles):
> len=128
> ac3_sum_square_butterfly_int32_c: 8497
> ac3_sum_square_butterfly_int32_rvv: 258
> len=1280
> ac3_sum_square_butterfly_int32_c: 84529
> ac3_sum_square_butterfly_int32_rvv: 2274
> 
> Co-Authored by: Yang Xiaojun <yangxiaojun@eswincomputing.com>
> Co-Authored by: Huang Xing <huangxing1@eswincomputing.com>
> Co-Authored by: Zeng Fanchen <zengfanchen@eswincomputing.com>
> Signed-off-by: Shen Peiting <shenpeiting@eswincomputing.com>
> ---
>  libavcodec/riscv/ac3dsp_init.c |  8 +++++
>  libavcodec/riscv/ac3dsp_rvv.S  | 53 ++++++++++++++++++++++++++++++++++
>  2 files changed, 61 insertions(+)
> 
> diff --git a/libavcodec/riscv/ac3dsp_init.c b/libavcodec/riscv/ac3dsp_init.c
> index a4e75a7541..4fd4abe83e 100644
> --- a/libavcodec/riscv/ac3dsp_init.c
> +++ b/libavcodec/riscv/ac3dsp_init.c
> @@ -26,6 +26,10 @@
> 
>  void ff_ac3_exponent_min_rvv(uint8_t *exp, int num_reuse_blocks, int
> nb_coefs); void ff_float_to_fixed24_rvv(int32_t *dst, const float *src,
> unsigned int len); +void ff_ac3_sum_square_butterfly_int32_rvv(int64_t
> sum[4],
> +                                            const int32_t *coef0,
> +                                            const int32_t *coef1,
> +                                            int len);
> 
>  av_cold void ff_ac3dsp_init_riscv(AC3DSPContext *c)
>  {
> @@ -35,6 +39,10 @@ av_cold void ff_ac3dsp_init_riscv(AC3DSPContext *c)
>          c->ac3_exponent_min = ff_ac3_exponent_min_rvv;
>          c->float_to_fixed24 = ff_float_to_fixed24_rvv;
>      }
> +#if (__riscv_xlen >= 64)
> +    if (flags & AV_CPU_FLAG_RVV_I64)
> +        c->sum_square_butterfly_int32 =
> ff_ac3_sum_square_butterfly_int32_rvv; +#endif
>  #endif
>  }
> 
> diff --git a/libavcodec/riscv/ac3dsp_rvv.S b/libavcodec/riscv/ac3dsp_rvv.S
> index d98e72c12c..4e0d238f85 100644
> --- a/libavcodec/riscv/ac3dsp_rvv.S
> +++ b/libavcodec/riscv/ac3dsp_rvv.S
> @@ -63,3 +63,56 @@ func ff_float_to_fixed24_rvv, zve32x
>      bgtz            a2, 1b
>      ret
>  endfunc
> +
> +
> +func ff_ac3_sum_square_butterfly_int32_rvv, zve64x
> +    vsetvli         t0, a3, e32, m2
> +    vle32.v         v0, (a1)
> +    vle32.v         v2, (a2)
> +    vadd.vv         v4, v0, v2
> +    vsub.vv         v6, v0, v2
> +    vwmul.vv        v8, v0, v0
> +    vwmul.vv        v12, v2, v2
> +    vwmul.vv        v16, v4, v4
> +    vwmul.vv        v20, v6, v6
> +    sub             a3, a3, t0
> +    slli            t0, t0, 2
> +    add             a1, a1, t0
> +    add             a2, a2, t0
> +    beq             a3, x0, 2f
> +1:
> +    vsetvli         t0, a3, e32, m2
> +    vle32.v         v0, (a1)
> +    vle32.v         v2, (a2)
> +    vadd.vv         v4, v0, v2
> +    vsub.vv         v6, v0, v2
> +    vwmacc.vv       v8, v0, v0
> +    vwmacc.vv       v12, v2, v2
> +    vwmacc.vv       v16, v4, v4
> +    vwmacc.vv       v20, v6, v6
> +    sub             a3, a3, t0
> +    slli            t0, t0, 2
> +    add             a1, a1, t0
> +    add             a2, a2, t0
> +    bnez            a3, 1b
> +2:
> +    vsetvli         t0, x0, e64, m4
> +    vmv.s.x         v24, x0
> +    vmv.s.x         v25, x0
> +    vmv.s.x         v26, x0
> +    vmv.s.x         v27, x0
> +    vredsum.vs      v24, v8, v24
> +    vredsum.vs      v25, v12, v25
> +    vredsum.vs      v26, v16, v26
> +    vredsum.vs      v27, v20, v27

As far as I can tell this is a reserved encoding (c.f. RVV 1.0 §3.4.2), and I 
believe that QEMU throws an Illegal instruction in this case. (I would check 
but there are no checkasm test case for this function.) Does this actual work 
on your simulator? Because if so, then your simulator is probably broken/
buggy.

> +    vsetivli        t0, 1, e64, m1
> +    vse64.v         v24, (a0)
> +    addi            a0, a0, 8
> +    vse64.v         v25, (a0)
> +    addi            a0, a0, 8
> +    vse64.v         v26, (a0)
> +    addi            a0, a0, 8
> +    vse64.v         v27, (a0)
> +    addi            a0, a0, 8
> +    ret
> +endfunc


-- 
雷米‧德尼-库尔蒙
http://www.remlab.net/



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