On Wednesday, 13 February 2019, Ilia Mirkin <imir...@alum.mit.edu> wrote:
> On Wed, Feb 13, 2019 at 1:29 PM Elie Tournier <tournier.e...@gmail.com> > wrote: > > > > > > > > On Wednesday, 13 February 2019, Ilia Mirkin <imir...@alum.mit.edu> > wrote: > >> > >> On Wed, Feb 13, 2019 at 12:47 PM Elie Tournier <tournier.e...@gmail.com> > wrote: > >> > > >> > On Fri, Jan 25, 2019 at 11:52:56AM -0800, Stéphane Marchesin wrote: > >> > > On Fri, Jan 25, 2019 at 2:25 AM Gert Wollny <gw.foss...@gmail.com> > wrote: > >> > > > > >> > > > Am Donnerstag, den 24.01.2019, 22:25 -0800 schrieb Stéphane > Marchesin: > >> > > > > > >> > > > > Yes, it's for running virgl on top of GLES. To emulate fp64 in > GL on > >> > > > > the guest side, we need fp64 on the host... > >> > > > > >> > > > BTW: we could also get it emulated from the guest side. When Elie > (in > >> > > > CC) initially proposed the fp64 emulation series it was for r600 > and > >> > > > TGSI was emitted. The created shaders are horribly long and it is > >> > > > certainly not performant, but if it's just for getting OpenGL 4.0 > >> > > > exposed it should be good enough. > >> > > > >> > > Yes, Ilia suggested this on IRC yesterday. My impression is that not > >> > > many applications/games need high performance fp64 (it's likely > mostly > >> > > compute stuff, which is not our target). I could be wrong though. If > >> > > anyone knows differently, please tell us :) > >> > > > >> > > > > >> > > > I'm not sure though how much work it would be to add this to the > soft > >> > > > fp64 as it has now landed for NIR, though. > >> > > > >> > > Yes, with virgl not using NIR, I am not sure how much work soft fp64 > >> > > will require. > >> > > >> > I spent a bit of time on the project recently. > >> > My thinking so far: > >> > * FP64 is bad . But everyone knows that. :) > >> > * Using the current soft fp64 require to emulate int64. > >> > * Soft fp64 and int64 involve function call which is, iiuc, not really > >> > supported in TGSI. > >> > * Soft fp64 is tied to NIR. Some pass/hack need to be port to GLSLIR. > >> > > >> > So the project will require a lot of work. > >> > >> But what's the alternative? Let's say you make a spec to expose > >> "proper" fp64 in GLES. No one outside mesa will implement this (why > >> bother). Certainly not the Adreno/Mali proprietary stacks of the > >> world. > > > > > > I'm not saying that we should get an extension. > > My point was, it's a lot of work. > >> > >> > >> And if you are on a stack that implements this in GLES, you might as > >> well be using desktop GL anyways... > >> > >> So going back to the original -- what use-case are you trying to cover > >> that's not already covered some other way? > > > > > > iiuc, Stephane want to run GL desktop on top of GLES. > > In order to expose a bigger version of GL, he need fp64 support. > > Right, I get that high-level desire. But it seems like if the > extension route is taken, this will only happen for cases where a > desktop GL driver is readily available as well already, so why the > requirement to run on GLES? No, the host will only support GLES. To be fair, I would prefer to avoid the extension route. > > -ilia >
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