Re: Memory ordering

On 12/3/2024 11:27 AM, MitchAlsup1 wrote:

On Tue, 3 Dec 2024 13:59:18 +0000, jseigh wrote:
 

The compiler is allow to reorder code as long as it knows the
reordering can't be observed or detected.

 With exceptions enabled, this would allow for almost no code
movement at all.
 

                                          If there are places
in the code it doesn't know this can't happen it won't optimize
across it, more or less.

 The problem is HOW to TELL the COMPILER that these memory references
are "more special" than normal--when languages give few mechanisms.

The compiler? Well, what about std::memory_order_*?
Heck even C++ has fences that deal with the compiler _only_... Say:
https://en.cppreference.com/w/cpp/atomic/atomic_signal_fence
vs:
https://en.cppreference.com/w/cpp/atomic/atomic_thread_fence
;^)