nir/lower_double_ops: Rework the if (progress) tree

Fixes: d7d35a9522 "nir/lower_doubles: Use the new NIR lowering..."
Reviewed-by: Dave Airlie <airlied@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5170>

src/compiler/nir/nir_lower_double_ops.c

@@ -753,7 +753,14 @@ nir_lower_doubles_impl(nir_function_impl *impl,
        * inlining.
        */
       nir_opt_deref_impl(impl);
-   }
+   } else if (progress) {
+      nir_metadata_preserve(impl, nir_metadata_block_index |
+                                  nir_metadata_dominance);
+    } else {
+#ifndef NDEBUG
+      impl->valid_metadata &= ~nir_metadata_not_properly_reset;
+#endif
+    }
 
    return progress;
 }