Re: [FFmpeg-devel] [PATCH] lavc/rv34dsp: optimise R-V V idct_dc_add

[flow gg <hlefthleft@gmail.com>]

Unfortunately I only test to obtain benchmarks and basic correctness. I
always feel the need for a professional to write the tests.

Rémi Denis-Courmont <remi@remlab.net> 于2024年5月23日周四 04:35写道：

>
>
> Le 22 mai 2024 23:28:54 GMT+03:00, "Rémi Denis-Courmont" <remi@remlab.net>
> a écrit :
> >This removes one stray LI and reworks the vector arithmetic to avoid
> >changing the vector configuration. On K230, this takes the 46.5 cycle
> >count down from 46.5 to 43.5.
> >---
> > libavcodec/riscv/rv34dsp_rvv.S | 13 ++++++-------
> > 1 file changed, 6 insertions(+), 7 deletions(-)
> >
> >diff --git a/libavcodec/riscv/rv34dsp_rvv.S
> b/libavcodec/riscv/rv34dsp_rvv.S
> >index f1f6345012..e8aff7e570 100644
> >--- a/libavcodec/riscv/rv34dsp_rvv.S
> >+++ b/libavcodec/riscv/rv34dsp_rvv.S
> >@@ -36,16 +36,15 @@ func ff_rv34_idct_dc_add_rvv, zve32x
> >         vsetivli      zero, 4, e8, mf4, ta, ma
> >         vlse32.v      v0, (a0), a1
> >         li            t1, 169
> >+        li            t2, 128
> >         mul           t1, t1, a2
> >-        li            a2, 255
> >+        vsetivli      zero, 4*4, e8, m1, ta, ma
> >+        vwsubu.vx     v2, v0, t2
> >         addi          t1, t1, 512
> >         srai          t1, t1, 10
> >-        vsetivli      zero, 4*4, e16, m2, ta, ma
> >-        vzext.vf2     v2, v0
> >-        vadd.vx       v2, v2, t1
> >-        vmax.vx       v2, v2, zero
> >-        vsetvli       zero, zero, e8, m1, ta, ma
> >-        vnclipu.wi    v0, v2, 0
> >+        vwadd.wx      v2, v2, t1
>
> Hmm, this should not work, as t1 has more than 8 bits. Maybe checkasm is
> sloppy here.
>
> >+        vnclip.wi     v0, v2, 0
> >+        vxor.vx       v0, v0, t2
> >         vsetivli      zero, 4, e8, mf4, ta, ma
> >         vsse32.v      v0, (a0), a1
> >
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