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better than just using 'volatile'. >> >> Maybe that has changed. We've upgraded minimum compilers since. > > I just checked a few test-cases, and I don't think anything has changed. > > All the trivial things where __atomic_load_n(__ATOMIC_RELAXED) *could* > do better than just our old code using "cast pointer to volatile" > resulted in no better code generation. I think compilers are *very* conservative in implementing any optimization related to atomics, to the extent that normal atomics load/stores are effectively volatile atomic load/stores and thus the optimization you are referring to here does not get performed. However there is some limited optimizations being done to fences, at least = I know in LLVM multiple fences do get merged. E.g. if you have=20 atomic_thread_fence(memory_order_acquire); atomic_thread_fence(memory_order_acq_rel); the first fence is abosrbed into the second. > > So we're sticking to that "cast to volatile" not because it's great, > but because it continues to be reliable and no worse than the fancy > modern versions. > > But at least it's explicit in the code, not hidden away in code that > *looks* like it just dereferences another field in a structure. The implicit load/store is arguably the biggest design failure of C11 atomi= cs. However we can still typedef like atomic_t or use "cast to _Atomic". But as= you said, currently this does not really yield any benefits over "cast to volat= ile". Best, Gary