glsl: remove dead uniforms in the nir linker

This is now possible as we do uniform linking via a nir based linker.

Shader-db results for IRIS (SKL):

total instructions in shared programs: 14947192 -> 14946397 (<.01%)
instructions in affected programs: 39498 -> 38703 (-2.01%)
helped: 230
HURT: 18

total cycles in shared programs: 324868402 -> 324847058 (<.01%)
cycles in affected programs: 706701 -> 685357 (-3.02%)
helped: 599
HURT: 449

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Anholt <eric@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4797>

diff --git a/src/compiler/glsl/gl_nir_linker.c b/src/compiler/glsl/gl_nir_linker.c
index 2fa1290bad4eacea5fa7262153e5c57247fa6455..7c38f28cd3c6fcfa536171d25d62ebe3fbd0b456 100644 (file)
--- a/src/compiler/glsl/gl_nir_linker.c
+++ b/src/compiler/glsl/gl_nir_linker.c
@@ -654,6 +654,14 @@ check_image_resources(struct gl_context *ctx, struct gl_shader_program *prog)
 bool
 gl_nir_link_glsl(struct gl_context *ctx, struct gl_shader_program *prog)
 {
+   for (unsigned i = 0; i < MESA_SHADER_STAGES; i++) {
+      struct gl_linked_shader *shader = prog->_LinkedShaders[i];
+      if (shader) {
+         nir_remove_dead_variables(shader->Program->nir, nir_var_uniform,
+                                   &can_remove_uniform);
+      }
+   }
+
    if (!gl_nir_link_uniforms(ctx, prog, true))
       return false;