1 files changed, 14 insertions, 3 deletions
diff --git a/compiler/GHC/Cmm/MachOp.hs b/compiler/GHC/Cmm/MachOp.hs
index 7bb84972a6..d134fdc346 100644
--- a/compiler/GHC/Cmm/MachOp.hs
+++ b/compiler/GHC/Cmm/MachOp.hs
@@ -24,6 +24,7 @@ module GHC.Cmm.MachOp
     , machOpMemcpyishAlign
 
     -- Atomic read-modify-write
+    , MemoryOrdering(..)
     , AtomicMachOp(..)
    )
 where
@@ -662,10 +663,12 @@ data CallishMachOp
   | MO_BSwap Width
   | MO_BRev Width
 
-  -- Atomic read-modify-write.
+  -- | Atomic read-modify-write. Arguments are @[dest, n]@.
   | MO_AtomicRMW Width AtomicMachOp
-  | MO_AtomicRead Width
-  | MO_AtomicWrite Width
+  -- | Atomic read. Arguments are @[addr]@.
+  | MO_AtomicRead Width MemoryOrdering
+  -- | Atomic write. Arguments are @[addr, value]@.
+  | MO_AtomicWrite Width MemoryOrdering
   -- | Atomic compare-and-swap. Arguments are @[dest, expected, new]@.
   -- Sequentially consistent.
   -- Possible future refactoring: should this be an'MO_AtomicRMW' variant?
@@ -680,6 +683,14 @@ data CallishMachOp
   | MO_ResumeThread
   deriving (Eq, Show)
 
+-- | C11 memory ordering semantics.
+data MemoryOrdering
+  = MemOrderRelaxed  -- ^ relaxed ordering
+  | MemOrderAcquire  -- ^ acquire ordering
+  | MemOrderRelease  -- ^ release ordering
+  | MemOrderSeqCst   -- ^ sequentially consistent
+  deriving (Eq, Ord, Show)
+
 -- | The operation to perform atomically.
 data AtomicMachOp =
       AMO_Add