https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63940
--- Comment #2 from Andreas Schwab <schwab@linux-m68k.org> ---
This looks bogus (from cxx_eval_binary_expression):
if (lhs == orig_lhs && rhs == orig_rhs)
return t;
Just because both operands are self-evaluating doesn't mean we can return the
unfolded expression.