[Mesa-dev] [PATCH v3 06/29] glsl: add ARB_gpu_shader_fp64 to the glsl extensions. (v2)

[Matt Turner]

On Sun, Feb 8, 2015 at 2:51 PM, Dave Airlie <airlied at gmail.com> wrote:
> On 9 February 2015 at 08:44, Aditya Avinash <adityaavinash1 at gmail.com> wrote:
>> Ya. I just want to know that part "only some r600".
>> I believe some of the nv0 cards doesn't support double. You have any ideas
>> or suggestions to make it possible?
>
> For AMD
> http://en.wikipedia.org/wiki/List_of_AMD_graphics_processing_units
>
> has what cards directly support double precision for r600/700/evergreen
>
> The plan is to implement a soffloat library like the fglrx drivers do for the
> GPUs that don't do doubles just to satisfy the GL4.0 requirement.

i965 hardware needs varying degrees of help to do doubles (the
round-down instruction doesn't work on doubles, for instance), so
we'll need some amount of this.

But I'm curious about what you think the cost:benefit is to writing
what sounds like a potentially significant amount of code [1] to
support doubles on old cards? For a feature that no one seems to use,
no less.

Actually, looking at the link you gave, Wikipedia says they just
support GL 3.3. Does fglrx expose ARB_gpu_shader_fp64 but not GL 4.0
on them?

[1] Take for instance a WIP implementation of floor:
http://cgit.freedesktop.org/~tpalli/mesa/commit/?h=fp64_floor&id=2e3909057e269b3466ceef8d2573abf82078e5c6