gistfile1.hs

{-# LANGUAGE BangPatterns #-}

fib' :: Int -> Int -> Int -> Int
fib' !0  !a  !_ = a
fib' !n !a !b = fib' (n-1) (b) (a+b)

fib :: Int -> Int
fib !n = fib' n 0 1

main = print $ fib (1000*1000*1000)


-- Generated:
{-
[section "data" {
     Main.$wfib'_closure:
         const Main.$wfib'_info;
 },
 Main.$wfib'_entry() //  [R4, R3, R2]
         { info_tbl: [(c3Jp,
                       label: Main.$wfib'_info
                       rep:HeapRep static { Fun {arity: 3 fun_type: ArgSpec 16} })]
           stack_info: arg_space: 8 updfr_space: Just 8
         }
     {offset
       c3Jp:
           _s3IV::I64 = R4;
           _s3IU::I64 = R3;
           _s3IT::I64 = R2;
           goto c3Jr;
       c3Jr:
           if (_s3IT::I64 != 0) goto c3Jn; else goto c3Jo;
       c3Jn:
           _s3IY::I64 = _s3IU::I64 + _s3IV::I64;
           _s3IU::I64 = _s3IV::I64;
           _s3IV::I64 = _s3IY::I64;
           _s3IT::I64 = _s3IT::I64 - 1;
           goto c3Jr;
       c3Jo:
           R1 = _s3IU::I64;
           call (P64[Sp])(R1) args: 8, res: 0, upd: 8;
     }
 }]

-}