On Mon, 14 Jul 2014 20:33:08 +0200, Ilia Mirkin <imir...@alum.mit.edu>
wrote:
On Mon, Jul 14, 2014 at 2:20 PM, Glenn Kennard <glenn.kenn...@gmail.com>
wrote:
diff --git a/src/gallium/drivers/r600/r600_pipe.c
b/src/gallium/drivers/r600/r600_pipe.c
index ca6399f..d967f0f 100644
--- a/src/gallium/drivers/r600/r600_pipe.c
+++ b/src/gallium/drivers/r600/r600_pipe.c
@@ -303,6 +303,9 @@ static int r600_get_param(struct pipe_screen*
pscreen, enum pipe_cap param)
case PIPE_CAP_SEAMLESS_CUBE_MAP_PER_TEXTURE:
case PIPE_CAP_CUBE_MAP_ARRAY:
case PIPE_CAP_TGSI_VS_LAYER_VIEWPORT:
+ case PIPE_CAP_TEXTURE_GATHER_SM5:
+ return family >= CHIP_CEDAR ? 1 : 0;
No clue what the hardware supports, and this CAP is actually not used
by the state tracker. However I believe it is meant to imply that you
can support the ARB_gs5 texture gather, including shadow comparisons
and non-constant offsets. This is not yet turned on by core mesa, but
do the textureGather tests still pass if you add
MESA_EXTENSION_OVERRIDE=GL_ARB_gpu_shader5? (You can do a piglit-run
with -t gather.) I'm not 100% sure, but I _think_ it also implies that
you can deal with selecting any component from a 4-component
texture... the ARB_gs5 spec says:
Since this extension requires support for gathering from
multi-component
textures, the minimum value of
MAX_PROGRAM_TEXTURE_GATHER_COMPONENTS_ARB
is increased to 4.
My understanding is that the hardware is meant to be able to support
GL4 one way or aonther, but sounds like more work needs to be done in
order to claim the SM5 compatibility cap...
Good catch, i missed that. It should return 0 for
PIPE_CAP_TEXTURE_GATHER_SM5, and 1 for number
of components, which lets it expose the ARB_texture_gather extension for
now, leaving SM5 support for
a later patch - the hardware apparently doesn't support texture sampler
swizzling natively for the GATHER4
instruction so some logic is required to compile shader variants whenever
the swizzle changes.
Also, have you looked at Dave Airlie's impl? Not sure what's been
going on there...
http://cgit.freedesktop.org/~airlied/mesa/log/?h=r600g-texture-gather
. He seemed to enable 4 components for >= CEDAR.
No, didn't pop up when i searched the archives for any prior work on this.
Interesting! It looks like the GL_ARB_texture_gather portion in that
branch is almost exactly equivalent to my patch.
It also has some of the additional parts needed for GL_ARB_gpu_shader5
such as non-constant offsets, but i don't see where it would trigger
shader recompiles if texture sampler swizzle changes? Does it pass piglit?
David, any opinions on how to move forward with this feature?
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