https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91131
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Index: gcc/gimplify.c
===================================================================
--- gcc/gimplify.c (revision 273355)
+++ gcc/gimplify.c (working copy)
@@ -5005,7 +5004,7 @@ gimplify_init_constructor (tree *expr_p,
one field to assign, initialize the target from a temporary. */
if (TREE_THIS_VOLATILE (object)
&& !TREE_ADDRESSABLE (type)
- && num_nonzero_elements > 0
+ && (num_nonzero_elements > 0 || !cleared)
&& vec_safe_length (elts) > 1)
{
tree temp = create_tmp_var (TYPE_MAIN_VARIANT (type));
note your use of packed might end up doing more than one store depending
on the architecture.
