[Mesa-dev] [PATCH 4/5] gallium/u_blitter: use TXF if possible

[Nicolai Hähnle]

On 31.05.2017 01:15, Marek Olšák wrote:
> On Wed, May 31, 2017 at 12:59 AM, Roland Scheidegger <sroland at vmware.com> wrote:
>> Am 31.05.2017 um 00:46 schrieb Marek Olšák:
>>> From: Marek Olšák <marek.olsak at amd.com>
>>>
>>> This fixes piglit:
>>>      arb_texture_view-rendering-r32ui
>>>
>>> TEX (image_sample) flushes denorms to 0 with FP32 textures on GCN, but such
>>> a texture can contain integer data written using an integer render view.
>>> If we do a transfer blit with TEX, denorms are flushed to 0. Luckily,
>>> TXF (image_load) doesn't do that.
>>>
>>> TXF also doesn't need to load the sampler state, so blit shaders don't have
>>> to do s_load_dwordx4.
>>>
>>> TXF doesn't do CLAMP_TO_EDGE, so it can only be used if the src box is
>>> in bounds, or if we clamp manually (this commit doesn't).
>>
>> Not that I think using TXF isn't a good idea, but shouldn't you make
>> sure you end up with a blit which is guaranteed to preserve all bits
>> here by using an appropriate format in the first place?
>> That TXF isn't going to denorm flush with f32 formats merely sounds like
>> an implementation detail of radeonsi to me, but I wouldn't say you could
>> really count on it here for the blitter.
> 
> That's true. Sadly, radeonsi can't change the format here due to
> a possible negative performance impact.

And using TXF makes sense anyway. Series is:

Reviewed-by: Nicolai Hähnle <nicolai.haehnle at amd.com>


> 
> Marek
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