id,summary,reporter,owner,description,type,status,priority,milestone,component,version,resolution,keywords,cc,os,architecture,failure,difficulty,testcase,blockedby,blocking,related
5298,Inlined functions aren't fully specialised,reinerp,,"When a function is inlined, it can expose other functions as candidates for specialisation, but GHC doesn't specialise them.

For instance, given the two modules

{{{
module A where

{-# INLINABLE fac #-}
fac :: Num a => a -> a
fac 0 = 1
fac n = n * fac (n-1)

{-# INLINE f #-}
f :: Num a => a -> a
f a = fac a
}}}


{{{
module B where

import A

g :: Int -> Int
g x = f x
}}}

we see that f is inlined, but fac isn't specialised for Ints:

{{{
B.g :: Int -> Int
[GblId,
 Arity=1,

 Unf=Unf{Src=<vanilla>, TopLvl=True, Arity=1, Value=True,
         ConLike=True, Cheap=True, Expandable=True,
         Guidance=IF_ARGS [0] 30 0}]
B.g =
  \ (x_ary :: Int) ->
    A.fac @ Int $fNumInt x_ary
}}}

Removing the INLINE pragma on f doesn't help.

Either of the following changes will cause fac to be specialised:

 * adding {-# SPECIALISE f :: Int -> Int #-} to module B
 * defining ""g x = fac x"" instead

This happens with both GHC 7.0.3 and GHC HEAD",bug,new,low,7.6.2,Compiler,7.0.3,,,hackage.haskell.org@… pho@… jpm@…,Unknown/Multiple,Unknown/Multiple,Runtime performance bug,,,,,