#3738: INLINE function loses unfolding
---------------------------------+------------------------------------------
Reporter: rl | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 6.13 | Keywords:
Os: Unknown/Multiple | Testcase:
Architecture: Unknown/Multiple | Failure: Runtime performance bug
---------------------------------+------------------------------------------
Small program:
{{{
foo :: Num a => [a] -> a
{-# INLINE foo #-}
foo = go 0
where
go m (n:ns) = m `seq` go (m+n) ns
go m [] = m
bar :: [Int] -> Int
{-# INLINE bar #-}
bar = foo
}}}
Here is what `bar` looks like in the interface file:
{{{
a6de4c46e53e565ed25ab5a38910e9cb
$wgo :: GHC.Prim.Int# -> [GHC.Types.Int] -> GHC.Prim.Int#
{- Arity: 2, HasNoCafRefs, Strictness: LS -}
6838e3faa095285614477ebc92f54987
bar :: [GHC.Types.Int] -> GHC.Types.Int
{- Arity: 1, HasNoCafRefs, Strictness: Sm, Inline: INLINE,
Unfolding: InlineRule: (arity 0 False) (Foo.bar_foo) -}
5d06906ae99b9aefa1c6d251c3f2fc46
bar_foo :: [GHC.Types.Int] -> GHC.Types.Int
{- Arity: 1, HasNoCafRefs, Strictness: Sm,
Unfolding: InlineRule: (arity 0 True) (\ w :: [GHC.Types.Int] ->
case @ GHC.Types.Int
Foo.$wgo 0 w of ww { DEFAULT ->
GHC.Types.I# ww }) -}
}}}
Note that the loop has disappeared from `bar`'s unfolding. Also, `bar_foo`
doesn't have an INLINE pragma.
Incidentally, GHC specialises `foo` here and the specialisation doesn't
get an INLINE pragma, either:
{{{
foo :: forall a. GHC.Num.Num a => [a] -> a
{- Arity: 1, HasNoCafRefs, Strictness: L, Inline: INLINE,
Unfolding: InlineRule: (arity 1 False) ... -}
foo_$sfoo :: [GHC.Types.Int] -> GHC.Types.Int
{- Arity: 1, HasNoCafRefs, Strictness: Sm,
Unfolding: InlineRule: (arity 0 False) ... -}
"SPEC Foo.foo [GHC.Types.Int]" ALWAYS forall $dNum :: GHC.Num.Num
GHC.Types.Int
Foo.foo @ GHC.Types.Int $dNum = Foo.foo_$sfoo
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3738>
GHC <http://www.haskell.org/ghc/>
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