-- Argument and return registers
| VanillaReg -- pointers, unboxed ints and chars
- PrimRep -- PtrRep, IntRep, CharRep, StablePtrRep or ForeignObjRep
+ PrimRep -- PtrRep, IntRep, CharRep, StablePtrRep or ForeignObjRep
-- (in case we need to distinguish)
FAST_INT -- its number (1 .. mAX_Vanilla_REG)