Dead code elimination would get rid of the extra instructions, but
skipping this saves iterations through the optimization loop.
>From shader-db:
N Min Max Median Avg Stddev
x 14672 3 16 3 3.1334515 0.59904168
+ 14672 1 16 3 2.8955153 0.77732963
Difference at 95.0% confidence
-0.237936 +/- 0.0158798
-7.59342% +/- 0.506783%
(Student's t, pooled s = 0.693935)
Embarassingly, the classic shadow mapping shader:
void main() { }
used to require three iterations through the optimization loop.
With this patch, it only requires one (which makes no progress).
Signed-off-by: Kenneth Graunke <kenn...@whitecape.org>
Cc: Matt Turner <matts...@gmail.com>
---
src/mesa/drivers/dri/i965/brw_fs.cpp | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp
b/src/mesa/drivers/dri/i965/brw_fs.cpp
index 65a4b66..a3268fb 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -3025,10 +3025,12 @@ fs_visitor::run()
emit_shader_time_begin();
calculate_urb_setup();
- if (brw->gen < 6)
- emit_interpolation_setup_gen4();
- else
- emit_interpolation_setup_gen6();
+ if (fp->Base.InputsRead > 0) {
+ if (brw->gen < 6)
+ emit_interpolation_setup_gen4();
+ else
+ emit_interpolation_setup_gen6();
+ }
/* We handle discards by keeping track of the still-live pixels in f0.1.
* Initialize it with the dispatched pixels.
--
1.8.3.2
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