st/mesa: Let NIR lower UBO and SSBO access when we have it

Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>

src/mesa/state_tracker/st_extensions.c

@@ -329,7 +329,13 @@ void st_init_limits(struct pipe_screen *screen,
       if (!screen->get_param(screen, PIPE_CAP_NIR_COMPACT_ARRAYS))
          options->LowerCombinedClipCullDistance = true;
 
-      options->LowerBufferInterfaceBlocks = true;
+      bool prefer_nir = PIPE_SHADER_IR_NIR ==
+         screen->get_shader_param(screen, sh, PIPE_SHADER_CAP_PREFERRED_IR);
+
+      /* NIR can do the lowering on our behalf and we'll get better results
+       * because it can actually optimize SSBO access.
+       */
+      options->LowerBufferInterfaceBlocks = !prefer_nir;
    }
 
    c->MaxUserAssignableUniformLocations =

src/mesa/state_tracker/st_glsl_to_nir.cpp

@@ -415,6 +415,10 @@ st_glsl_to_nir(struct st_context *st, struct gl_program *prog,
 
    st_nir_opts(nir, is_scalar);
 
+   NIR_PASS_V(nir, gl_nir_lower_buffers, shader_program);
+   /* Do a round of constant folding to clean up address calculations */
+   NIR_PASS_V(nir, nir_opt_constant_folding);
+
    if (lower_64bit) {
       bool lowered_64bit_ops = false;
       bool progress = false;