[Mesa-dev] Summer of Code ideas (maybe just an idea wishlist?)

Jan Vesely jan.vesely at rutgers.edu
Thu Mar 26 19:39:34 PDT 2015


On Thu, 2015-03-26 at 22:27 -0400, Ilia Mirkin wrote:
> On Thu, Mar 26, 2015 at 10:17 PM, Jan Vesely <jan.vesely at rutgers.edu> wrote:
> > On Thu, 2015-03-26 at 21:11 -0400, Rob Clark wrote:
> >> On Thu, Mar 26, 2015 at 8:59 PM, Ilia Mirkin <imirkin at alum.mit.edu> wrote:
> >> > On Thu, Mar 26, 2015 at 8:50 PM, Rob Clark <robdclark at gmail.com> wrote:
> >> >> On Thu, Mar 26, 2015 at 3:10 PM, Ilia Mirkin <imirkin at alum.mit.edu> wrote:
> >> >>> On Thu, Mar 26, 2015 at 3:02 PM, Jason Ekstrand <jason at jlekstrand.net> wrote:
> >> >>>> On Thu, Mar 26, 2015 at 12:00 PM, Aditya Avinash
> >> >>>> <adityaavinash1 at gmail.com> wrote:
> >> >>>>> I mean, implementing fp64 on single precision systems.
> >> >>>>
> >> >>>> Ok, That makes more sense!  Having lowering passes for various FP64
> >> >>>> operations would be great.
> >> >>>
> >> >>> We should make sure that there are customers of such work. It only
> >> >>> makes sense to do this when everything else but FP64 are supported for
> >> >>> GL 4.0 (including tess). r600 (eg/ni) is an obvious customer, although
> >> >>> that may be easier to do in sb (I believe GlennK has been looking at
> >> >>> it, not sure how far he's gotten). Other than that... not sure. Could
> >> >>> be that Adreno A420 can do tess && has no native fp64 support, still
> >> >>> need to figure that out (hasn't been RE'd yet).
> >> >>
> >> >> fwiw, fp64 lowering is almost certainly useful for a3xx when we get to
> >> >> the point of doing compute..
> >> >
> >> > Why does compute need fp64? Do the blob drivers expose the fp64 capability?
> >> >
> >>
> >> opencl (beyond embedded profile) requires fp64.. blob driver on a3xx
> >> only supports embedded profile opencl (roughly everything *except*
> >> fp64)..
> >
> > fp64 is required only for OpenCL 1.2+, embedded also makes int64, and
> > atomic functions optional + precision of some built-in operations is
> > relaxed.
> 
> I'm reading the OpenCL 2.0 spec... it says
> 
> Double precision is an optional feature so the mandated minimum double
> precision floating point capability is 0.
> 
> and also in the bit about changes from OpenCL 1.2:
> 
> Double precision is now an optional core feature instead of an extension
> 
> What makes you say that fp64 is required by CL 1.2+?

I reread the specs, and you are correct, its not required. I don't know
why I remembered so. thanks for pointing it out.

jan

> 
>   -ilia


-- 
Jan Vesely <jan.vesely at rutgers.edu>
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