nir: Remove deref chain support from lower_alpha_test

Acked-by: Rob Clark <robdclark@gmail.com>
Acked-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Acked-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/compiler/nir/nir_lower_alpha_test.c

@@ -41,6 +41,8 @@ nir_lower_alpha_test(nir_shader *shader, enum compare_func func,
 {
    assert(shader->info.stage == MESA_SHADER_FRAGMENT);
 
+   nir_assert_unlowered_derefs(shader, nir_lower_load_store_derefs);
+
    nir_foreach_function(function, shader) {
       nir_function_impl *impl = function->impl;
       nir_builder b;
@@ -55,9 +57,6 @@ nir_lower_alpha_test(nir_shader *shader, enum compare_func func,
                nir_variable *out = NULL;
 
                switch (intr->intrinsic) {
-               case nir_intrinsic_store_var:
-                  out = intr->variables[0]->var;
-                  break;
                case nir_intrinsic_store_deref:
                   out = nir_deref_instr_get_variable(nir_src_as_deref(intr->src[0]));
                   break;