Hey Johan,

on https://ghc.haskell.org/trac/ghc/ticket/7883 Ryan helped articulate what he'd want wrt memory ordering semantics.

One point is that It might be totally valid and reasonable to provide *both* variants, though if we only were to do one, the strong ordering guarantees might be a better default, albeit your use case and others does benefit from using the weakest / simplest primops possible,

On Thu, May 15, 2014 at 6:01 AM, Johan Tibell <johan.tibell@gmail.com> wrote:

I will update the wiki page (and later CmmSink) with the guarantees we expect CallishMachOps to provide. We do need to pick what kind of guarantee we want to provide. Options are here: http://en.cppreference.com/w/cpp/atomic/memory_order

Do we want to have these CallishMachOps to imply a full memory fence CPU instruction or some more relaxed ordering (e.g. only atomicity)?

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