[Mesa-dev] [PATCH] glsl: lower constant arrays to uniform arrays before optimisation loop

[Timothy Arceri]

Previously the last stage would not get optimised until the backend did
its GLSL IR opt loop. I plan on removing that from i965 shortly which
caused huge regressions in Deus-ex and Tomb Raider which have large
constant arrays. Moving lowering before the opt loop in the GLSL linker
fixes this and unexpectedly improves some compute shaders also.

shader-db results BDW:

instructions helped:   shaders/closed/steam/deus-ex-mankind-divided/374.shader_test CS SIMD16: 204 -> 194 (-4.90%)
instructions helped:   shaders/closed/steam/deus-ex-mankind-divided/318.shader_test CS SIMD8: 1010 -> 741 (-26.63%)
instructions helped:   shaders/closed/steam/deus-ex-mankind-divided/144.shader_test CS SIMD8: 542 -> 385 (-28.97%)

cycles helped:   shaders/closed/steam/deus-ex-mankind-divided/318.shader_test CS SIMD8: 1831382 -> 1818492 (-0.70%)
cycles helped:   shaders/closed/steam/deus-ex-mankind-divided/144.shader_test CS SIMD8: 216238 -> 206180 (-4.65%)
cycles helped:   shaders/closed/steam/deus-ex-mankind-divided/374.shader_test CS SIMD16: 18484 -> 16644 (-9.95%)

total instructions in shared programs: 13060313 -> 13059877 (-0.00%)
instructions in affected programs: 1756 -> 1320 (-24.83%)
helped: 3
HURT: 0

total cycles in shared programs: 256586698 -> 256561910 (-0.01%)
cycles in affected programs: 2066104 -> 2041316 (-1.20%)
helped: 3
HURT: 0
---
 src/compiler/glsl/linker.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/compiler/glsl/linker.cpp b/src/compiler/glsl/linker.cpp
index d187b66..5233d43 100644
--- a/src/compiler/glsl/linker.cpp
+++ b/src/compiler/glsl/linker.cpp
@@ -5051,6 +5051,8 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
          lower_tess_level(prog->_LinkedShaders[i]);
       }
 
+      lower_const_arrays_to_uniforms(prog->_LinkedShaders[i]->ir, i);
+
       if (ctx->Const.GLSLOptimizeConservatively) {
          /* Run it just once. */
          do_common_optimization(prog->_LinkedShaders[i]->ir, true, false,
@@ -5064,7 +5066,6 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
             ;
       }
 
-      lower_const_arrays_to_uniforms(prog->_LinkedShaders[i]->ir, i);
       propagate_invariance(prog->_LinkedShaders[i]->ir);
    }
 
-- 
2.9.3