[cpp-threads] Brief example ITANIUM Implementation for C/C++ Memory Model

[Alexander Terekhov]

On Wed, Dec 24, 2008 at 6:58 AM, Hans Boehm <Hans.Boehm at hp.com> wrote:
>
> On Tue, 23 Dec 2008, Alexander Terekhov wrote:
>
>> Following the lead of
>>
>> http://www.rdrop.com/users/paulmck/scalability/paper/N2745r.2008.12.16a.html
>> (cmpxchg aside for a moment aside, "Store Seq Cst" is surely busted)
>>
>> here's a brief example ITANIUM implementation for C/C++ Memory Model:
>>
>> (cmpxchg aside for a moment)
>>
>> Load Relaxed:  ld
>> Load Consume:  ld
>> Load Acquire:  ld.acq
>> Load Seq_Cst:  mf,ld.acq
>> Store Relaxed: st
>> Store Release: st.rel
>> Store Seq Cst: st.rel,mf
>> Consume Fence: <ignore>
>> Acquire Fence: mf
>> Release Fence: mf
>> Acq_Rel Fence: mf
>> Seq_Cst Fence: mf
>>
>> Any objections and/or questions?
>
> None, except that Load relaxed is also ld.acq, in order to prevent
> reordering of loads from the same location.

Do you have an example illustrating the need of .acq for relaxed loads?

TIA.

regards,
alexander.