[Mesa-dev] [PATCH] i965/blorp: do not use unnecessary hw-blending support

[Kenneth Graunke]

On 01/27/2014 11:06 AM, Pohjolainen, Topi wrote:
> On Mon, Jan 27, 2014 at 10:20:54AM -0800, Eric Anholt wrote:
>> Topi Pohjolainen <topi.pohjolainen at intel.com> writes:
>>
>>> This is really not needed as blorp blit programs already sample
>>> XRGB normally and get alpha channel set to 1.0 automatically by
>>> the sampler engine. This is simply copied directly to the payload
>>> of the render target write message and hence there is no need for
>>> any additional blending support from the pixel processing pipeline.
>>>
>>> Fixes recently modified piglit test gl-3.2-layered-rendering-blit
>>> on IVB. No regressions on IVB.
>>
>> What about when you have a RGB-but-not-alpha gl format that's been
>> promoted to an ARGB Mesa and BRW surface format?  I don't think blorp's
>> samplers have any overrides going on there.
> 
> I relied on the restriction that only blits from RGBX to RGBA and vice
> versa are allowed. Otherwise the formats must match.

I think Eric's right.  Technically, it works for BlitFramebuffer because
of what you say...but...we allow nearly arbitrary format conversions for
CopyTexSubImage today, so I think dropping this could break things
there.  Plus, we hope to add that for BlitFramebuffer too (it's trivial).

So, I think this code may need to stay after all...sorry for the confusion.

--Ken

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