Re: [PATCH 18/18] arm64: lto: Strengthen READ_ONCE() to acquire when CLANG_LTO=y

[Arnd Bergmann]

On Wed, Jul 1, 2020 at 12:19 PM Will Deacon <will@xxxxxxxxxx> wrote:
> On Tue, Jun 30, 2020 at 09:25:03PM +0200, Arnd Bergmann wrote:
> > On Tue, Jun 30, 2020 at 7:39 PM Will Deacon <will@xxxxxxxxxx> wrote:
> > Once we make gcc-4.9 the minimum version,
> > this could be further improved to
> >
> >        __auto_type __x = &(x);
>
> Is anybody working on moving to 4.9? I've seen the mails from Linus
> championing it, but I thought there was a RHEL in support that people
> might care about?

I don't think there was a serious discussion about it so far, and
we only just moved to gcc-4.8.

I think moving to gnu11 (gcc-4.9 or clang) instead of gnu99 has other
benefits as well, so we may well want to do it anyway when something
else comes up.

For __auto_type(), we could do it like

#if (clang or gcc-4.9+)
#define auto_typeof(x) __auto_type
#else
#define auto_typeof(x) typeof(x)
#endif

which could be used in a lot of macros.

     Arnd