[Mesa-dev] [PATCH 1/2] nir: retain pixel_center_integer information when lowering gl_FragCoord

[Kenneth Graunke]

On Tuesday, February 13, 2018 10:00:44 PM PST Timothy Arceri wrote:
> On 14/02/18 16:24, Jason Ekstrand wrote:
> > First off, you should add an index to the intrinsic if you're going to 
> > do this and it should probably be set elsewhere.  Otherwise, it becomes 
> > this magic secret radeonsi thing.
> 
> Ah yes that's how it's done, I thought there was a better way to do this 
> thanks.
> 
> Although what do you mean by set it elsewhere? This is where the 
> intrinsic is created and the system variable goes away I don't see how 
> it can be set elsewhere.

Basically, add a shader_info::pixel_center_integer flag, and have
glsl_to_nir() look for the decorated fragcoord variable and set that.

Honestly, it might make sense to set a global shader_info field in
the GLSL frontend itself, and stop storing decorations on the fragcoord
variable in the first place.  Make NIR and the backends follow the new
SPIR-V convention and make the GLSL frontend deal with GLSL oddities.

It looks like the radeonsi backend sees this and sets a global flag,
so global would probably be a better fit anyway...
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