i965: Reenable the fragment shader precompile.

Precompiling the shader at link time often allows us to avoid compiling
it at the first use.  This moves the expensive compilation and
optimization process to game or level load time, rather than at draw
time, where we really can't avoid any cycles and don't want to risk
stalling the GPU.

The downside is that we have to guess the non-orthagonal state the
program will have set when it draws with the shader.  Previously, we
guessed wrong for nearly every shader, so it wasn't useful.  With the
recent SamplerUnits rework and this series, we've either eliminated
state or made smarter guesses, and usually get it right now.

In the L4D2 time demo, I now have 39 fragment shader recompiles and no
vertex shader recompiles.  Before this series and the SamplerUnits
rework, I had 206 fragment shader recompiles and 192 vertex shader
recompiles.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Anholt <eric@anholt.net>

diff --git a/src/mesa/drivers/dri/intel/intel_screen.c b/src/mesa/drivers/dri/intel/intel_screen.c
index 103fcd257c1154571ca8156dbd53b050397830d3..ef5a87a94587e1920864b67fb27c5e1fa40d7359 100644 (file)
--- a/src/mesa/drivers/dri/intel/intel_screen.c
+++ b/src/mesa/drivers/dri/intel/intel_screen.c
@@ -85,7 +85,7 @@ PUBLIC const char __driConfigOptions[] =
         DRI_CONF_DESC(en, "Enable stub ARB_occlusion_query support on 915/945.")
       DRI_CONF_OPT_END
 
-      DRI_CONF_OPT_BEGIN(shader_precompile, bool, false)
+      DRI_CONF_OPT_BEGIN(shader_precompile, bool, true)
         DRI_CONF_DESC(en, "Perform code generation at shader link time.")
       DRI_CONF_OPT_END
    DRI_CONF_SECTION_END