[struct Atomic] Use dependent layout

Author: lorentey

Sources/Atomics/Atomic.swift

@@ -13,8 +13,7 @@
 #if compiler(>=5.9) && $RawLayout
 import Builtin
 
-// FIXME: What we actually want to say is @_rawLayout(like: Value.AtomicRepresentation)
-@_rawLayout(like: DoubleWord.AtomicRepresentation)
+@_rawLayout(like: Value.AtomicRepresentation)
 @frozen
 public struct Atomic<Value: AtomicValue>: ~Copyable
 where Value.AtomicRepresentation.Value == Value

Sources/Atomics/AtomicBool.swift.gyb

@@ -190,6 +190,9 @@ extension Bool.AtomicRepresentation {
 }
 
 % for construct in ["Atomic", "UnsafeAtomic", "ManagedAtomic"]:
+%  if construct == "Atomic":
+#if compiler(>=5.9) && $RawLayout
+%  end
 extension ${construct} where Value == Bool {
 % for (name, iname, op, label, doc) in boolOperations:
   /// Perform an atomic ${doc} operation and return the original value, applying
@@ -234,4 +237,7 @@ extension ${construct} where Value == Bool {
   }
 % end
 }
+%  if construct == "Atomic":
+#endif
+%  end
 % end

Sources/Atomics/autogenerated/AtomicBool.swift

@@ -229,6 +229,7 @@ extension Bool.AtomicRepresentation {
   }
 }
 
+#if compiler(>=5.9) && $RawLayout
 extension Atomic where Value == Bool {
   /// Perform an atomic logical AND operation and return the original value, applying
   /// the specified memory ordering.
@@ -339,6 +340,7 @@ extension Atomic where Value == Bool {
     return original != operand
   }
 }
+#endif
 extension UnsafeAtomic where Value == Bool {
   /// Perform an atomic logical AND operation and return the original value, applying
   /// the specified memory ordering.