[Mesa-dev] [PATCH 1/2] ff_fragment_shader: Don't do unnecessary (and dangerous) uniform setup.

[Paul Berry]

Previously, right after calling _mesa_glsl_link_shader(), the fixed
function fragment shader code made several calls with the ostensible
purpose of setting up uniforms for the fragment shader it just
created.

These calls are unnecessary, since _mesa_glsl_link_shader() calls
driver->LinkShader(), which takes care of calling these functions (or
their equivalent).  Also, they are dangerous to call after
_mesa_glsl_link_shader() has returned, because on back-ends such as
i965 which do precompilation, _mesa_glsl_link_shader() may have
already cached pointers to the existing uniform structures; attempting
to set up the uniforms again invalidates those cached pointers.

It was only by sheer coincidence that this wasn't manifesting itself
as a bug.  It turns out that i965's precompile mechanism was always
setting bit 0 of brw_wm_prog_key::proj_attrib_mask to 0 for fixed
function fragment shaders, but during normal usage this bit usually
gets set to 1.  As a result, the precompiled shader (with its invalid
uniform pointers) was not being used.

I'm about to introduce some changes that cause bit 0 of
proj_attrib_mask to be set consistently between precompilation and
normal usage, so to avoid regressions I need to get rid of the
dangerous duplicate uniform setup code first.
---
 src/mesa/main/ff_fragment_shader.cpp | 16 ----------------
 1 file changed, 16 deletions(-)

diff --git a/src/mesa/main/ff_fragment_shader.cpp b/src/mesa/main/ff_fragment_shader.cpp
index 186988b..01a4542 100644
--- a/src/mesa/main/ff_fragment_shader.cpp
+++ b/src/mesa/main/ff_fragment_shader.cpp
@@ -1350,22 +1350,6 @@ create_new_program(struct gl_context *ctx, struct state_key *key)
 
    _mesa_glsl_link_shader(ctx, p.shader_program);
 
-   /* Set the sampler uniforms, and relink to get them into the linked
-    * program.
-    */
-   struct gl_shader *const fs =
-      p.shader_program->_LinkedShaders[MESA_SHADER_FRAGMENT];
-   struct gl_program *const fp = fs->Program;
-
-   _mesa_generate_parameters_list_for_uniforms(p.shader_program, fs,
-					       fp->Parameters);
-
-   _mesa_associate_uniform_storage(ctx, p.shader_program, fp->Parameters);
-
-   _mesa_update_shader_textures_used(p.shader_program, fp);
-   if (ctx->Driver.SamplerUniformChange)
-      ctx->Driver.SamplerUniformChange(ctx, fp->Target, fp);
-
    if (!p.shader_program->LinkStatus)
       _mesa_problem(ctx, "Failed to link fixed function fragment shader: %s\n",
 		    p.shader_program->InfoLog);
-- 
1.8.2