+ CharRep -> 4
+ Int8Rep -> 1
+ IntRep -> wORD_SIZE
+ AddrRep -> wORD_SIZE
+ FloatRep -> wORD_SIZE
+ DoubleRep -> dOUBLE_SIZE * wORD_SIZE
+ Word64Rep -> wORD64_SIZE * wORD_SIZE
+ Int64Rep -> iNT64_SIZE * wORD_SIZE
+ WeakPtrRep -> wORD_SIZE
+ ForeignObjRep -> wORD_SIZE
+ StablePtrRep -> wORD_SIZE
+ StableNameRep -> wORD_SIZE
+ ArrayRep -> wORD_SIZE
+ ByteArrayRep -> wORD_SIZE
+ _ -> panic "getPrimRepSize: ouch - this wasn't supposed to happen!"