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

[Axel Davy]

On 9/12/18 11:44 PM, Roland Scheidegger wrote:
> Am 12.09.2018 um 23:43 schrieb Roland Scheidegger:
>
>>> I small precision I want to add: This is not the only place clamping
>>> makes a difference.
>>>
>>> Indeed else MUL_ZERO_WINS would be safe to use and remove all the clamping.
>>>
>>>
>>> The rasterizers can produce NaN when given Inf in the vertex shader on
>>> some devices for example,
>>>
>>> and I think on some devices inf and FLT_MAX give different color in the
>>> pixel shader.
>>>
>>>
>>> Thus why I want to test carefully what do the other vendors for all the
>>> shader versions (we know already there are
>>>
>>> behaviour changes for some) and check with the behaviours mentionned
>>> above, before removing the clamps when MUL_ZERO_WINS.
>> Yes it's all quite a mess. d3d9 rules are awkward (if they are even
>> documented), whereas gl may do whatever (personally I would consider at
>> least for core contexts everything not following ieee754 rules a bug,
>> well maybe not for gles...).
> Forgot to mention, of course unless forced with things like mul_zero_wins.
>
> Roland
>
>
>
Yes, it is indeed quite messy. The online official documentation says a 
thing,

and the drivers do differently. However all windows driver do mul_zero_wins.


Axel