[Mesa-dev] [PATCH] i965: Disable channel expressions for scalar GS, TCS, TES.

[Kenneth Graunke]

On Broadwell, I get the following shader-db statistics:

Tessellation Control Shaders:

   total instructions in shared programs: 57327 -> 57012 (-0.55%)
   instructions in affected programs: 27334 -> 27019 (-1.15%)
   helped: 45
   HURT: 0

   total cycles in shared programs: 265692 -> 255188 (-3.95%)
   cycles in affected programs: 263122 -> 252618 (-3.99%)
   helped: 184
   HURT: 26

Tessellation Evaluation Shaders:

   total instructions in shared programs: 23236 -> 23157 (-0.34%)
   instructions in affected programs: 2791 -> 2712 (-2.83%)
   helped: 27
   HURT: 0

   total cycles in shared programs: 151858 -> 149704 (-1.42%)
   cycles in affected programs: 151858 -> 149704 (-1.42%)
   helped: 101
   HURT: 114

Geometry Shaders:

   Orbital Explorer goes from 6442 -> 6356 instructions.
   Two Shadow of Mordor shaders increase by a single instruction.

Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
---
 src/mesa/drivers/dri/i965/brw_link.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/mesa/drivers/dri/i965/brw_link.cpp b/src/mesa/drivers/dri/i965/brw_link.cpp
index bb7e1eb..f5df6fb 100644
--- a/src/mesa/drivers/dri/i965/brw_link.cpp
+++ b/src/mesa/drivers/dri/i965/brw_link.cpp
@@ -147,7 +147,9 @@ process_glsl_ir(gl_shader_stage stage,
       progress = false;
 
       if (compiler->scalar_stage[shader->Stage]) {
-         brw_do_channel_expressions(shader->ir);
+         if (shader->Stage == MESA_SHADER_VERTEX ||
+             shader->Stage == MESA_SHADER_FRAGMENT)
+            brw_do_channel_expressions(shader->ir);
          brw_do_vector_splitting(shader->ir);
       }
 
-- 
2.8.0