[FFmpeg-devel] [PATCH] riscv: fix scalar product initialisation

[Rémi Denis-Courmont]

Le maanantaina 3. lokakuuta 2022, 18.06.42 EEST remi at remlab.net a écrit :
> From: Rémi Denis-Courmont <remi at remlab.net>
> 
> VSETVLI xd, x0, ...' has rather nonobvious semantics:
> - If xd is x0, then it preserves the current vector length.
> - If xd is not x0, it sets the vector length to the supported maximum.
> 
> Also somewhat confusingly, while VMV.X.S always does its thing
> regardless of the selected vector length, VMV.S.X does _nothing_ if the
> selected vector length is zero.
> 
> So the current code breaks fails to initialise the accumulator if we
> are unlucky to have a selected vector length of zero on entry. Fix it
> by forcing the vector length to one.

Ping.

The issue becomes systematically reproducible with the checkasm support.

-- 
雷米‧德尼-库尔蒙
http://www.remlab.net/