On 08/06/2010 01:17 PM, H. Peter Anvin wrote:On 08/06/2010 07:53 AM, Jeremy Fitzhardinge wrote:On 08/06/2010 05:43 AM, Jan Beulich wrote:You certainly mean "the compiler currently treats this as being:" - I
don't think there's a guarantee it'll always be doing so.
for (;;) {I therefore think it needs to be written this way.
if (inc.tickets.head == inc.tickets.tail)
goto out;
...
}
out: barrier();
}
(Which would probably be a reasonable way to clarify the code.)
Agreed.
A call/return to an actual out-of-line function is a barrier (and will
always be a barrier, as it is the fundamental ABI sequence points),
but to an inline function it is not.
Yes. So the goto explicitly puts the barrier into the control flow which
should stop the compiler from doing anything unexpected.