http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47409
--- Comment #18 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Francesco Zappa Nardelli from comment #16)
> Dear all
>
> a possibly related issue. Consider
>
> struct S1 {
> long f;
> };
> volatile struct S1 g;
>
> struct S1 func_1 () {
> return g;
> }
>
> void main () {
> func_1 ();
> }
>
> This program, if compiled with a recent gcc svn:
>
> $ gcc -v
> Target: x86_64-unknown-linux-gnu
> gcc version 4.9.0 20130625 (experimental) (GCC)
>
> correctly loads the long at g.f at -O0. However the assembly generated at
> -O2:
>
> func_1:
> movq g(%rip), %rax
> ret
> main:
> rep; ret
>
> does not perform the volatile load access, which, as far as I understand, is
> incorrect.
It does starting with GCC 4.8.2 and was a bug in older GCC versions.
Richard.
> -francesco
