[Mesa-stable] [Mesa-dev] [PATCH 1/5] st/nine: Clamp RCP when 0*inf!=0

[Axel Davy]

On 9/9/18 9:40 PM, Ilia Mirkin wrote:
> On Sun, Sep 9, 2018 at 3:19 PM, Axel Davy <davyaxel0 at gmail.com> wrote:
>> Tests showed Intel on windows does always clamp
>> RCP, RSQ and LOG (thus preventing inf/nan generation),
>> for all shader versions (some vendor behaviours vary
>> with shader versions).
> By the way, this happens because on Intel, the ALU is put into a
> special mode where it just doesn't generate NaN's at all under any
> conditions. I don't think that other vendors operate this way.
>

I've found the code source of my tests, and completed them to have a 
better picture.

The conclusion is that the clamping can be safely removed all the time 
when mul_zero_wins.

I produced a commit in that purpose:

https://github.com/iXit/Mesa-3D/commit/ed82c87da2799a40d8f7b87f8ff99d6f20a9f601


I'll send it to mesa-dev when our testers can check there is no regression.

In the commit I detail the test results.


I still want to get "st/nine: Clamp RCP when 0*inf!=0" merged, 
especially for stable.


Yours,


Axel