mesa: add gl_constants::GLSLOptimizeConservatively

to reduce the amount of GLSL optimizations for drivers that can do better.

Reviewed-by: Eric Anholt <[email protected]>

2 files changed, 14 insertions, 3 deletions

diff --git a/src/mesa/main/ff_fragment_shader.cpp b/src/mesa/main/ff_fragment_shader.cpp
index fd2c71f93ee..48b84e8fd73 100644
--- a/src/mesa/main/ff_fragment_shader.cpp
+++ b/src/mesa/main/ff_fragment_shader.cpp
@@ -1254,9 +1254,13 @@ create_new_program(struct gl_context *ctx, struct state_key *key)
    const struct gl_shader_compiler_options *options =
       &ctx->Const.ShaderCompilerOptions[MESA_SHADER_FRAGMENT];
 
-   while (do_common_optimization(p.shader->ir, false, false, options,
-                                 ctx->Const.NativeIntegers))
-      ;
+   /* Conservative approach: Don't optimize here, the linker does it too. */
+   if (!ctx->Const.GLSLOptimizeConservatively) {
+      while (do_common_optimization(p.shader->ir, false, false, options,
+                                    ctx->Const.NativeIntegers))
+         ;
+   }
+
    reparent_ir(p.shader->ir, p.shader->ir);
 
    p.shader->CompileStatus = true;
diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
index c7535a37761..2693a8068c0 100644
--- a/src/mesa/main/mtypes.h
+++ b/src/mesa/main/mtypes.h
@@ -3643,6 +3643,13 @@ struct gl_constants
    bool GLSLFrontFacingIsSysVal;
 
    /**
+    * Run the minimum amount of GLSL optimizations to be able to link
+    * shaders optimally (eliminate dead varyings and uniforms) and just do
+    * all the necessary lowering.
+    */
+   bool GLSLOptimizeConservatively;
+
+   /**
     * Always use the GetTransformFeedbackVertexCount() driver hook, rather
     * than passing the transform feedback object to the drawing function.
     */