-dOUBLE_SIZE = (DOUBLE_SIZE :: Int)
-wORD64_SIZE = (WORD64_SIZE :: Int)
-iNT64_SIZE = (INT64_SIZE :: Int)
+dOUBLE_SIZE = (SIZEOF_DOUBLE `quot` SIZEOF_HSWORD :: Int)
+wORD64_SIZE = (8 `quot` SIZEOF_HSWORD :: Int)
+iNT64_SIZE = wORD64_SIZE
+\end{code}
+
+This tells the native code generator the size of the spill
+area is has available.
+
+\begin{code}
+rESERVED_C_STACK_BYTES = (RESERVED_C_STACK_BYTES :: Int)
+\end{code}
+
+The amount of (Haskell) stack to leave free for saving registers when
+returning to the scheduler.
+
+\begin{code}
+rESERVED_STACK_WORDS = (RESERVED_STACK_WORDS :: Int)
+\end{code}
+
+Size of a word, in bytes
+
+\begin{code}
+wORD_SIZE = (SIZEOF_HSWORD :: Int)