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

[Kenneth Graunke]

On 01/27/2014 02:46 AM, Topi Pohjolainen wrote:
> 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.
> 
> This is effectively revert of c0554141a9b831b4e614747104dcbbe0fe489b9d:
> 
>     i965/blorp: Support overriding destination alpha to 1.0.
> 
>     Currently, Blorp requires the source and destination formats to be
>     equal.  However, we'd really like to be able to blit between XRGB and
>     ARGB formats; our BLT engine paths have supported this for a long time.
> 
>     For ARGB -> XRGB, nothing needs to occur: the missing alpha is already
>     interpreted as 1.0.  For XRGB -> ARGB, we need to smash the alpha
>     channel to 1.0 when writing the destination colors.  This is fairly
>     straightforward with blending.
> 
>     For now, this code is never used, as the source and destination formats
>     still must be equal.  The next patch will relax that restriction.
> 
>     NOTE: This is a candidate for the 9.1 branch.
> 
> CC: Ian Romanick <ian.d.romanick at intel.com>
> CC: Kenneth Graunke <kenneth at whitecape.org>
> CC: Martin Steigerwald <martin at lichtvoll.de>
> Signed-off-by: Topi Pohjolainen <topi.pohjolainen at intel.com>

I'm still not sure why deleting this would fix your test, but it does
and this code is definitely not necessary to make ARGB -> XRGB blits work.

Cc: mesa-stable at lists.freedesktop.org (perhaps?)
Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>

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