"H.J. Lu" <hjl.to...@gmail.com> writes:
>> So, to emit HLE prefix, it is possible to do:
>> foo2 (int *p, int oldv, int newv)
>> __atomic_compare_exchange_n (p, &oldv, newv, 0, __ATOMIC_ACQUIRE |
>> __ATOMIC_USE_HLE, __ATOMIC_ACQUIRE);
>> return oldv;
> This is wrong since HLE ACQUIRE/RELEASE has nothing to do with
> C++ atomic acquire/release. You can have HLE RELEASE with C++
> atomic acquire.
It makes sense to combine the two. On x86 C++ atomic acquire/release
means the compiler cannot move references outside. For HLE
we really want the same, otherwise some of the memory references
inside the transaction may not be transactional.
So I think HLE_ACQUIRE should imply C++ acquire
and HLE_RELEASE imply C++ release.
a...@linux.intel.com -- Speaking for myself only