[Bug c/106818] code is genereated differently with or without 'extern'

[pangbw at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106818

--- Comment #1 from baoshan <pangbw at gmail dot com> ---
With 'extern', four 'sb' are ued to store value into "p->i";
while without 'extern', only one 'sw' is used.