T6084.hs

{-# LANGUAGE MagicHash, BangPatterns #-}
module Main where

import GHC.Exts

{-# NOINLINE f #-}
f :: (Int# -> Float# -> Double# -> Float# -> Double# -> String) -> String
f g = g 3# 4.0# 5.0## 6.0# 6.9## ++ " World!"

{-# NOINLINE p #-}
p :: Int# -> Float# -> Double# -> Float# -> Double# -> String
p i j k l m = "Hello"

{-# NOINLINE q #-}
q :: Int# -> Int# -> Float# -> Double# -> Float# -> Double# -> String
q _ i j k l m = "Hello " ++ show (F# l) ++ " " ++ show (D# m)

{-# NOINLINE r #-}
r :: Int# -> Float# -> Double# -> Float# -> Double# -> String
r i = let !(I# z) = length [I# 1# .. I# i] in \j k l m -> p z j k l m
  -- ghc won't eta-expand around the length, because it has unknown cost

main = do
  putStrLn (f p)    -- fast call
  putStrLn (f r)    -- slow call: function but wrong arity
  let g = last [q 1#]
  putStrLn (f g)    -- slow call: thunk

  putStrLn (f g)
= putStrLn (f (last [q 1#]))
= putStrLn (f (q 1#))
= putStrLn ((q 1#) 3# 4.0# 5.0## 6.0# 6.9## ++ " World!")
= putStrLn (q 1# 3# 4.0# 5.0## 6.0# 6.9## ++ " World!")
= putStrLn ("Hello " ++ show (F# 6.0#) ++ " " ++ show (D# 6.9##) ++ " World!")
= putStrLn ("Hello 6.0 6.9 World!")

../inplace/bin/ghc-stage1 -fasm -keep-llvm-file -fforce-recomp T6084.hs -O2 -o T6084-asm && ./T6084-asm
[1 of 1] Compiling Main ( T6084.hs, T6084.o )
Linking T6084-asm ...
Hello World!
Hello World!
Hello 4.0 5.0 World!

../inplace/bin/ghc-stage1 -fllvm -keep-llvm-file -fforce-recomp T6084.hs -O2 -o T6084-llvm && ./T6084-llvm
[1 of 1] Compiling Main ( T6084.hs, T6084.o )
Linking T6084-llvm ...
Hello World!
Hello World!
Hello 4.0 5.0 World!

NOTE to self: do not pass -keep-llvm-file, it will silently force -fllvm

../inplace/bin/ghc-stage1 -fllvm -fforce-recomp T6084.hs -O2 -o T6084-llvm && ./T6084-llvm
[1 of 1] Compiling Main ( T6084.hs, T6084.o )
Linking T6084-llvm ...
Hello World!
Hello World!
Hello 4.0 5.0 World!

../inplace/bin/ghc-stage1 -fasm -fforce-recomp T6084.hs -O2 -o T6084-asm && ./T6084-asm
[1 of 1] Compiling Main ( T6084.hs, T6084.o )
Linking T6084-asm ...
Hello World!
Hello World!
Hello 6.0 6.9 World!