How to use MO_AtomicRMW in cmm files?

I'm writing a CMM module, which needs to execute call MO_AtomicRMW W64 AMO_Add. But looking at compiler/GHC/Cmm/Parser.y there seems to be no way to obtain MO_AtomicRMW, only MO_AtomicRead or MO_AtomicWrite. Am I missing something?

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