+%************************************************************************
+%* *
+\subsection{PrimRep}
+%* *
+%************************************************************************
+
+A PrimRep is an abstraction of a type. It contains information that
+the code generator needs in order to pass arguments, return results,
+and store values of this type.
+
+A PrimRep is somewhat similar to a CgRep (see codeGen/SMRep) and a
+MachRep (see cmm/MachOp), although each of these types has a distinct
+and clearly defined purpose:
+
+ - A PrimRep is a CgRep + information about signedness + information
+ about primitive pointers (AddrRep). Signedness and primitive
+ pointers are required when passing a primitive type to a foreign
+ function, but aren't needed for call/return conventions of Haskell
+ functions.
+
+ - A MachRep is a basic machine type (non-void, doesn't contain
+ information on pointerhood or signedness, but contains some
+ reps that don't have corresponding Haskell types).
+
+\begin{code}
+data PrimRep
+ = VoidRep
+ | PtrRep
+ | IntRep -- signed, word-sized
+ | WordRep -- unsinged, word-sized
+ | Int64Rep -- signed, 64 bit (32-bit words only)
+ | Word64Rep -- unsigned, 64 bit (32-bit words only)
+ | AddrRep -- a pointer, but not to a Haskell value
+ | FloatRep
+ | DoubleRep
+\end{code}