nir/load_libclc: Don't add generic variants that already exist

At some point in the future, adding generic variants to libclc will
hopefully no longer be needed.  At that point, we don't want the NIR
code adding duplicates.  Check if the generic version already exists
and, if it does, don't re-add it.

Signed-off-by: Karol Herbst <kherbst@redhat.com>
Reviewed-by: Karol Herbst <kherbst@redhat.com>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/18675>

src/compiler/spirv/nir_load_libclc.c

@@ -266,6 +266,9 @@ libclc_add_generic_variants(nir_shader *shader)
       assert(generic_name[offset_1] == '1');
       generic_name[offset_1] = '4';
 
+      if (nir_shader_get_function_for_name(shader, generic_name))
+         continue;
+
       nir_function *gfunc = nir_function_create(shader, generic_name);
       gfunc->num_params = func->num_params;
       gfunc->params = ralloc_array(shader, nir_parameter, gfunc->num_params);