+getPrimRepSizeInBytes CharRep = 4
+getPrimRepSizeInBytes IntRep = wORD_SIZE
+getPrimRepSizeInBytes WordRep = wORD_SIZE
+getPrimRepSizeInBytes AddrRep = wORD_SIZE
+getPrimRepSizeInBytes FloatRep = wORD_SIZE
+getPrimRepSizeInBytes DoubleRep = dOUBLE_SIZE * wORD_SIZE
+getPrimRepSizeInBytes Int8Rep = 1
+getPrimRepSizeInBytes Int16Rep = 2
+getPrimRepSizeInBytes Int32Rep = 4
+getPrimRepSizeInBytes Int64Rep = 8
+getPrimRepSizeInBytes Word8Rep = 1
+getPrimRepSizeInBytes Word16Rep = 2
+getPrimRepSizeInBytes Word32Rep = 4
+getPrimRepSizeInBytes Word64Rep = 8
+getPrimRepSizeInBytes WeakPtrRep = wORD_SIZE
+getPrimRepSizeInBytes ForeignObjRep = wORD_SIZE
+getPrimRepSizeInBytes StablePtrRep = wORD_SIZE
+getPrimRepSizeInBytes StableNameRep = wORD_SIZE
+getPrimRepSizeInBytes ArrayRep = wORD_SIZE
+getPrimRepSizeInBytes ByteArrayRep = wORD_SIZE
+getPrimRepSizeInBytes _ = panic "getPrimRepSize: ouch - this wasn't supposed to happen!"