Re: [RFC] LKMM: Add volatile_if()

Peter Zijlstra
2021-06-04T19:18:12Z

On Fri, Jun 04, 2021 at 12:24:07PM -0500, Segher Boessenkool wrote:
> On Fri, Jun 04, 2021 at 10:10:29AM -0700, Linus Torvalds wrote:
> > The compiler *cannot* just say "oh, I'll do that 'volatile asm
> > barrier' whether the condition is true or not". That would be a
> > fundamental compiler bug.
>
> Yes.

So we can all agree on something like this?

#define volatile_if(x) \
if (({ _Bool __x = (x); BUILD_BUG_ON(__builtin_constant_p(__x)); __x; }) && \
({ barrier(); 1; }))

Do we keep volatile_if() or do we like ctrl_dep_if() better?