[Mesa-dev] [PATCH 1/2] nir: add an isinf opcode, and an option to use it.

[Jason Ekstrand]

On Thu, Mar 16, 2017 at 8:33 PM, Roland Scheidegger <sroland at vmware.com>
wrote:

> Am 17.03.2017 um 02:29 schrieb Dave Airlie:
> > On 17 March 2017 at 11:09, Jason Ekstrand <jason at jlekstrand.net> wrote:
> >> On March 16, 2017 5:04:37 PM Dave Airlie <airlied at gmail.com> wrote:
> >>
> >>> From: Dave Airlie <airlied at redhat.com>
> >>>
> >>> In order to get isinf(NaN) correct, at least radv can't
> >>> use an unordered equals which feq has to be for us, this
> >>> passes isinf to the backend and let's it sort it out as it
> >>> pleases.
> >>
> >>
> >> I think comparisons are something that were going to need to sort out
> better
> >> in general.  SPIR-V's rules are stricter than GL (at least the way we
> >> interpret it).  Could you please be more specific about the issue?
> >
> > IsInf(NaN) unordered appears to end up at true, when the spec for isinf
> > says it should be false.
> >
> > well SPIR-V has the unorder and ordered stuff for OpenCL kernels, just
> > not sure what want in NIR in this area. If I default to using ordered
> compares
> > for NIR I get isnan and funord fails last I tried.
>
> FWIW tgsi uses ordered for all comparisons except not equal.
> Ok well maybe not all drivers do, but that's what I'd consider what it
> should be (radeonsi does that too at a quick glance). Because, well, you
> guessed it, d3d10... GL of course won't mandate anything with its super
> relaxed nan rules. But this pretty much matches what you get with
> ordinary comparison operators in c, so may uneducated guess is it would
> be a good match for nir too...
>

That was more-or-less my plan.

On Thu, Mar 16, 2017 at 6:32 PM, Dave Airlie <airlied at gmail.com> wrote:

> > Another option would be to make this lower_isinf and add a quick lowering
> > line to nir_opt_algebraic.  That's more idiomatic for nir.
>
> If I do that though won't that mean I have to set lower_isinf for all
> current NIR
> users?
>

No, just us.  We're the only ones that consume SPIR-V. :-)
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/mesa-dev/attachments/20170316/a9f70317/attachment.html>