On Saturday, 25 January 2014 at 10:00:58 UTC, Johannes Pfau wrote:
(For example it isn't valid in D to access a shared variable
with
normal operations anyway, AFAIK. You need to use the atomicOp
things
and these will the worry about the hardware part, using the
correct
instructions and so on)
Is it invalid to access shared data on stack too? How about
closures?
See also:
http://www.drdobbs.com/parallel/volatile-vs-volatile/212701484
So volatile is a completely different thing in C#/JAVA and
C/C++. This
is why I'm confused, C compilers are not supposed to guarantee
that
another thread can see all changes to a volatile variable,
volatile must
just prevent compiler optimizations. So if Itanium C compilers
automatically use the barrier/fence instructions for volatile
that's
IMHO a compiler performance bug.
The standard says "memory" and doesn't address cache and
processor optimizations, so it probably allows different
interpretations. Even if there's no fence, disallowed compiler
optimizations are still a performance hit - on all platforms.
