kk: Fix compute system value and algebric lowering in pre-compiles

Changes are the result of two issues:

- In library form, workgroup size is not lowered. Only once the
  pre-compiles are distinct variants with entry-points can we
  lower uses of the workgroup size input.

- Some unimplemented instructions like `ufind_msb` would make their
  way through to the final shader, if they are generated by other
  algebraic optimizations. `nir_opt_algebraic` needs to be run in a
  loop to ensure they are eliminated.

Reviewed-by: Aitor Camacho <aitor@lunarg.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/41568>

src/kosmickrisp/clc/kk_clc.c

@@ -277,6 +277,11 @@ main(int argc, char **argv)
          NIR_PASS(_, s, nir_lower_vars_to_explicit_types, nir_var_mem_shared,
                   glsl_get_cl_type_size_align);
 
+         /* Workgroup size cannot be lowered when the shader is in library form,
+          * so we need to lower compute system values again now that it is a
+          * variant with a distinct entry-point. */
+         NIR_PASS(_, s, nir_lower_compute_system_values, NULL);
+
          NIR_PASS(_, s, nir_lower_explicit_io, nir_var_mem_shared,
                   nir_address_format_62bit_generic);
 
@@ -296,8 +301,14 @@ main(int argc, char **argv)
          NIR_PASS(_, s, nir_convert_from_ssa, true, true);
          NIR_PASS(_, s, nir_trivialize_registers);
 
-         /* nir_lower_explicit_io will create unpack_64 we need to lower */
-         NIR_PASS(_, s, nir_opt_algebraic);
+         /* nir_lower_explicit_io will create unpack_64 we need to lower.
+          * Perform in a loop to make sure any optimizations that result in
+          * instructions we don't implement are fully lowered */
+         bool progress = false;
+         do {
+            progress = false;
+            NIR_PASS(progress, s, nir_opt_algebraic);
+         } while (progress);
 
          nir_shader_gather_info(s, nir_shader_get_entrypoint(s));
          struct nir_to_msl_options options = {};