[cpp-threads] Brief example ITANIUM Implementation forC/C++MemoryModel

[Peter Dimov]

Alexander Terekhov:

> IOW,
>
> P1: Y.store(1, seq_cst);
> P2: Z.store(1, seq_cst); a = Y.load(relaxed);
> P3: b = Y.load(relaxed); fence(seq_cst); c = Z.load(relaxed);
>
> may legitimately yield a=0, b=1, c=0

Do you insist on P2's load being relaxed? As it stands, your example may 
well allow this outcome. With:

    P2: Z.store(1, seq_cst); a = Y.load(seq_cst);

I suspect that it doesn't, but I'm too lazy right now to write down all 
possible total orders and prove (or disprove) it. :-)

> P1: Y.store(1, seq_cst);
> P2: Z.store(1, seq_cst); a = Y.load(relaxed);
> P3: b = Y.load(relaxed); c = Z.load(seq_cst);

It does, AFAIK, even with the modified P2.