[Mesa-dev] [PATCH 4/5] gallium: Add PIPE_SHADER_CAP_DOUBLES

[Tom Stellard]

On Wed, Jun 18, 2014 at 09:54:28AM +1000, Dave Airlie wrote:
> On 18 June 2014 05:08, Roland Scheidegger <sroland at vmware.com> wrote:
> > This looks ok to me though since tgsi currently doesn't have any double
> > opcodes (well the docs have them...) it doesn't really apply to most
> > drivers (at least I assume you don't want to add support for it for tgsi).
> 
> I've mostly forward ported the old gallium double code, and have
> written most of ARB_gpu_shader_fp64 on top,
> 
> Though the question I did want to ask Tom is if he is just going to
> expose hw that has doubles, or does
> he plan on emulating doubles.
> 

My intention was that this CAP would be enabled for drivers with either
native double support or with double emulation implemented in the driver.
I'm not currently planning to implement double emulation, so I would
only enable this for hardware with native double support.

> For a lot of GLSL4.0 GPUs from AMD fglrx emulates doubles using
> massive magic shaders, I'm unsure
> if we should have a lowering pass above/below the TGSI line for these
> types of situations and what that
> would mean for this CAP.
>

If someone implemented double lowering above the TGSI line, then it
should only been done with drivers that report 0 for this CAP.

-Tom

> Dave.
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