On 01/11/2017 05:32 PM, Marek Olšák wrote:
On Wed, Jan 11, 2017 at 4:33 PM, Erik Faye-Lund <[email protected]> wrote:
On Wed, Jan 11, 2017 at 4:14 PM, Nicolai Hähnle <[email protected]> wrote:
On 11.01.2017 13:17, Marek Olšák wrote:
On Tue, Jan 10, 2017 at 6:48 PM, Jason Ekstrand <[email protected]>
wrote:
I'll be honest, I'm not a fan... Given that D3D10 has one defined
behavior,
D3D9 has another, and GL doesn't specify, I don't really think we should
be
making a global change to all drivers to do the D3D9 behavior just to fix
one app. Sure, other apps probably have the same bug, but are we going
to
have apps that expect the D3D10 behavior that we've now explicitly made
not
work?
If we're going to hack around an app bug, I would really rather see it
behind a driconf option rather than a global change to driver behavior.
Even better, it'd be cool if we could see the app get fixed. (Yes, I know
that's not likely).
I think we are not in a position to refuse this workaround, or put
more precisely, to have a different behavior from everybody else. By
"we", I mean i965, radeonsi, svga. All closed drivers use abs. Many
Mesa drivers also use abs internally (r300, r600, nv30, nv50/nvc0).
This is not really a workaround for a specific application, even
though it's strongly motivated by that. It's a fix to align the few
remaining drivers with all others.
We talked with the publisher about this a very long time ago. While I
don't remember the details (Nicolai?), I think they refused to fix it
because radeonsi appeared to be the only driver not doing abs.
If I remember correctly, it wasn't so much a refusal as a lack of
follow-through. They even had an option in their framework to add the
abs(...) when translating shaders, but somehow didn't turn it on
unconditionally for some reason...
VP even says so here:
https://github.com/virtual-programming/specops-linux/issues/20
They recommend against patching mesa to do abs, though.
We should still patch Mesa to align the behavior with closed drivers
and gallium drivers like r600g and nouveau. In other words, it's too
late to tell us not to patch Mesa, because r600g and nouveau have been
"patched" since the beginning.
We only need to decide whether we should do it in the GLSL compiler or
radeonsi, i.e. whether we should exclude i965 and svga.
I do agree with that.
Marek
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