On 22.06.2017 03:38, Rob Clark wrote:
On Wed, Jun 21, 2017 at 8:15 PM, Marek Olšák <[email protected]> wrote:
On Wed, Jun 21, 2017 at 10:37 PM, Rob Clark <[email protected]> wrote:
On Tue, Jun 20, 2017 at 6:54 PM, Marek Olšák <[email protected]> wrote:
Hi,
This series updates pipe loaders so that flags such as drirc options
can be passed to create_screen(). I have compile-tested everything
except clover.
The first pipe_screen flag is a drirc option to fix incorrect grass
rendering in Rocket League for radeonsi. Rocket League expects DirectX
behavior for partial derivative computations after discard/kill, but
radeonsi implements the more efficient but stricter OpenGL behavior
and that will remain our default behavior. The new screen flag forces
radeonsi to use the DX behavior for that game.
do we really want this to be a *global* option for the screen?
Yes. Shaders are pipe_screen (global) objects in radeonsi, so a
compiler option also has to be global. We can't look at the context
during the TGSI->LLVM translation.
well, I didn't really mean per-screen vs per-context, as much as
per-screen vs per-shader (or maybe more per-screen vs
per-instruction?)
I honestly don't think it's worth the trouble. Applications that are
properly coded against GLSL can benefit from the relaxed semantics, and
applications that get it wrong in one shader are rather likely to get it
wrong everywhere.
Since GLSL simply says derivatives are undefined after non-uniform
discard, and this option makes it defined instead, setting this flag can
never break the behavior of a correctly written shader.
Cheers,
Nicolai
I'm just thinking, some drivers use lowering passes that internally
generate kill's. I *guess* it would only matter if they also had
ddx/ddy instructions, but not sure.
not really sure if this would actually be a problem or not..
Whether or not this affects you depends on how your hardware
implements kill/discard. Not just ddx/ddy, texture instructions
computing derivatives internally are affected by kill/discard too.
I guess most of the lowering passes that introduce kill's are more
like legacy gl things (clip-planes, glBitmap(), maybe some others but
pretty sure it is all legacy type stuff), so maybe it isn't likely to
matter. I'm not totally sure about the expected interactions between
kill and other instructions, so not totally sure about whether I
should care.. but figured I should point it out.. and if it doesn't
matter, it doesn't matter.
BR,
-R
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