st/mesa: disable EXT_separate_shader_objects

The extension disallows elimination of set-but-unused varyings.

Reviewed-by: Ian Romanick <[email protected]>

2 files changed, 11 insertions, 1 deletions

diff --git a/docs/relnotes/9.2.html b/docs/relnotes/9.2.html
index 1f49191148e..6809506873d 100644
--- a/docs/relnotes/9.2.html
+++ b/docs/relnotes/9.2.html
@@ -68,6 +68,9 @@ Note: some of the new features are only available with certain drivers.
 2007.</li>
 <li>Removed GL_MESA_resize_buffers because it was only really implemented by
 the (unsupported) GDI driver.</li>
+<li>GL_EXT_separate_shader_objects has been removed from all Gallium drivers,
+    because it disallows a critical GLSL shader optimization.
+    GL_ARB_separate_shader_objects doesn't have this issue.
 </ul>
 
 </div>
diff --git a/src/mesa/state_tracker/st_extensions.c b/src/mesa/state_tracker/st_extensions.c
index c0ec06a18a1..df0761a80a6 100644
--- a/src/mesa/state_tracker/st_extensions.c
+++ b/src/mesa/state_tracker/st_extensions.c
@@ -554,7 +554,14 @@ void st_init_extensions(struct st_context *st)
    ctx->Extensions.EXT_pixel_buffer_object = GL_TRUE;
    ctx->Extensions.EXT_point_parameters = GL_TRUE;
    ctx->Extensions.EXT_provoking_vertex = GL_TRUE;
-   ctx->Extensions.EXT_separate_shader_objects = GL_TRUE;
+
+   /* IMPORTANT:
+    *    Don't enable EXT_separate_shader_objects. It disallows a certain
+    *    optimization in the GLSL compiler and therefore is considered
+    *    harmful.
+    */
+   ctx->Extensions.EXT_separate_shader_objects = GL_FALSE;
+
    ctx->Extensions.EXT_texture_env_dot3 = GL_TRUE;
    ctx->Extensions.EXT_vertex_array_bgra = GL_TRUE;