Naming, value types and tests for Addr# atomics

The atomic Exchange and CAS operations on integral types are updated to
take and return more natural `Word#` rather than `Int#` values.  These
are bit-block not arithmetic operations, and the sign bit plays no
special role.

Standardises the names to `atomic<OpType><ValType>Addr#`, where `OpType` is one
of `Cas` or `Exchange` and `ValType` is presently either `Word` or `Addr`.
Eventually, variants for `Word32` and `Word64` can and should be added,
once #11953 and related issues (e.g. #13825) are resolved.

Adds tests for `Addr#` CAS that mirror existing tests for
`MutableByteArray#`.

2 files changed, 23 insertions, 15 deletions

diff --git a/compiler/GHC/Builtin/primops.txt.pp b/compiler/GHC/Builtin/primops.txt.pp
index 2ee69382dc..c292b9ecdc 100644
--- a/compiler/GHC/Builtin/primops.txt.pp
+++ b/compiler/GHC/Builtin/primops.txt.pp
@@ -2079,39 +2079,47 @@ primop  WriteOffAddrOp_Word64 "writeWord64OffAddr#" GenPrimOp
    with has_side_effects = True
         can_fail         = True
 
-primop  InterlockedExchange_Addr "atomicExchangeAddr#" GenPrimOp
+primop  InterlockedExchange_Addr "atomicExchangeAddrAddr#" GenPrimOp
    Addr# -> Addr# -> State# s -> (# State# s, Addr# #)
    {The atomic exchange operation. Atomically exchanges the value at the first address
     with the Addr# given as second argument. Implies a read barrier.}
    with has_side_effects = True
+        can_fail         = True
 
-primop  InterlockedExchange_Int "atomicExchangeInt#" GenPrimOp
-   Addr# -> Int# -> State# s -> (# State# s, Int# #)
+primop  InterlockedExchange_Word "atomicExchangeWordAddr#" GenPrimOp
+   Addr# -> Word# -> State# s -> (# State# s, Word# #)
    {The atomic exchange operation. Atomically exchanges the value at the address
     with the given value. Returns the old value. Implies a read barrier.}
    with has_side_effects = True
+        can_fail         = True
 
-primop  AtomicCompareExchange_Int "atomicCasInt#" GenPrimOp
-   Addr# -> Int# -> Int# -> State# s -> (# State# s, Int# #)
+primop  CasAddrOp_Addr "atomicCasAddrAddr#" GenPrimOp
+   Addr# -> Addr# -> Addr# -> State# s -> (# State# s, Addr# #)
    { Compare and swap on a word-sized memory location.
 
-     Use as atomicCasInt# location expected desired
+     Use as: \s -> atomicCasAddrAddr# location expected desired s
 
-     This version always returns the old value read. This follows the normal protocol for CAS operations (and matches the underlying instruction on most architectures).
+     This version always returns the old value read. This follows the normal
+     protocol for CAS operations (and matches the underlying instruction on
+     most architectures).
 
      Implies a full memory barrier.}
    with has_side_effects = True
+        can_fail         = True
 
-primop  AtomicCompareExchange_Addr "atomicCasAddr#" GenPrimOp
-   Addr# -> Addr# -> Addr# -> State# s -> (# State# s, Addr# #)
-   { Compare and swap on a word-sized memory location.
+primop  CasAddrOp_Word "atomicCasWordAddr#" GenPrimOp
+   Addr# -> Word# -> Word# -> State# s -> (# State# s, Word# #)
+   { Compare and swap on a word-sized and aligned memory location.
 
-     Use as atomicCasAddr# location expected desired
+     Use as: \s -> atomicCasWordAddr# location expected desired s
 
-     This version always returns the old value read. This follows the normal protocol for CAS operations (and matches the underlying instruction on most architectures).
+     This version always returns the old value read. This follows the normal
+     protocol for CAS operations (and matches the underlying instruction on
+     most architectures).
 
      Implies a full memory barrier.}
    with has_side_effects = True
+        can_fail         = True
 
 ------------------------------------------------------------------------
 section "Mutable variables"
diff --git a/compiler/GHC/StgToCmm/Prim.hs b/compiler/GHC/StgToCmm/Prim.hs
index a6f2dcb6da..099a3850dc 100644
--- a/compiler/GHC/StgToCmm/Prim.hs
+++ b/compiler/GHC/StgToCmm/Prim.hs
@@ -848,11 +848,11 @@ emitPrimOp dflags primop = case primop of
 -- Atomic operations
   InterlockedExchange_Addr -> \[src, value] -> opIntoRegs $ \[res] ->
     emitPrimCall [res] (MO_Xchg (wordWidth platform)) [src, value]
-  InterlockedExchange_Int -> \[src, value] -> opIntoRegs $ \[res] ->
+  InterlockedExchange_Word -> \[src, value] -> opIntoRegs $ \[res] ->
     emitPrimCall [res] (MO_Xchg (wordWidth platform)) [src, value]
-  AtomicCompareExchange_Int -> \[dst, expected, new] -> opIntoRegs $ \[res] ->
+  CasAddrOp_Addr -> \[dst, expected, new] -> opIntoRegs $ \[res] ->
     emitPrimCall [res] (MO_Cmpxchg (wordWidth platform)) [dst, expected, new]
-  AtomicCompareExchange_Addr -> \[dst, expected, new] -> opIntoRegs $ \[res] ->
+  CasAddrOp_Word -> \[dst, expected, new] -> opIntoRegs $ \[res] ->
     emitPrimCall [res] (MO_Cmpxchg (wordWidth platform)) [dst, expected, new]
 
 -- SIMD primops