nir: Properly invalidate metadata in nir_split_var_copies().

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Jason Ekstrand <jason.ekstrand@intel.com>
Reviewed-by: Eduardo Lima Mitev <elima@igalia.com>
Cc: mesa-stable@lists.freedesktop.org
(cherry picked from commit 8bb44510fc)

src/glsl/nir/nir_split_var_copies.c

@@ -271,6 +271,11 @@ split_var_copies_impl(nir_function_impl *impl)
 
    ralloc_free(state.dead_ctx);
 
+   if (state.progress) {
+      nir_metadata_preserve(impl, nir_metadata_block_index |
+                                  nir_metadata_dominance);
+   }
+
    return state.progress;
 }