Re: desperately seeking RULES help

9 Jun 2008

      Here it is:

{-# OPTIONS_GHC -O2 -Wall -fglasgow-exts -ddump-simpl #-}
-- compile with: ghc -fno-method-sharing -c F.hs
module F(test) where

-- | Domain of a linear map.
class AsInt a where
 toInt'   :: a -> Int
 fromInt' :: Int -> a

{-# INLINE[1] toInt #-}
toInt :: (AsInt a) => a -> Int
toInt = toInt'

{-# INLINE[1] fromInt #-}
fromInt :: (AsInt a) => Int -> a
fromInt = fromInt'

{-# RULES
"toInt/fromInt"   forall m . toInt (fromInt m) = m
 #-}

{-# INLINE onInt #-}
onInt :: AsInt a => (Int -> Int) -> (a -> a)
onInt f x = fromInt (f (toInt x))

test :: AsInt a => (Int -> Int) -> (Int -> Int) -> (a -> a)
test h g = onInt h . onInt g

{-
Glasgow Haskell Compiler, Version 6.8.2.20080211, for Haskell 98,
stage 2 booted by GHC version 6.6.1

F.test =
  \ (@ a_a6C)
    ($dAsInt_a6M :: F.AsInt a_a6C)
    (h_a67 :: GHC.Base.Int -> GHC.Base.Int)
    (g_a68 :: GHC.Base.Int -> GHC.Base.Int)
    (eta_s77 :: a_a6C) ->
    case $dAsInt_a6M of tpl_B1 { F.:DAsInt tpl1_B2 tpl2_B3 ->
    tpl2_B3 (h_a67 (g_a68 (tpl1_B2 eta_s77)))
    }
-}

On Mon, Jun 9, 2008 at 11:00 AM, Claus Reinke  wrote:
...
could you please send the complete options/commandline and
the expect final form of 'test'? i did play with Conal's example
as well, but couldn't find a combination to make it work.
perhaps i'm looking at the wrong output, but it seems i either get
non-inlined 'onInt's in various forms or multiple matches out of the same
dictionary, but with generic method names rather than the original
'fromInt'/'toInt'.
claus
...
Thanks a million, Lennart!  -fno-method-sharing was the missing piece.  -
Conal
On Sat, Jun 7, 2008 at 5:07 AM, Lennart Augustsson

wrote:
...
Here's something that actually works.  You need to pass
-fno-method-sharing on the command line.
Instead of using rules on methods it uses rules on global functions,
and these global functions don't get inlined until late (after the
rule has fired).
-- Lennart
module F where
-- | Domain of a linear map.
class AsInt a where
 toInt'   :: a -> Int
 fromInt' :: Int -> a
{-# INLINE[1] toInt #-}
toInt :: (AsInt a) => a -> Int
toInt = toInt'
{-# INLINE[1] fromInt #-}
fromInt :: (AsInt a) => Int -> a
fromInt = fromInt'
{-# RULES
"toInt/fromInt"   forall m . toInt (fromInt m) = m
 #-}
{-# INLINE onInt #-}
onInt :: AsInt a => (Int -> Int) -> (a -> a)
onInt f x = fromInt (f (toInt x))
test :: AsInt a => (Int -> Int) -> (Int -> Int) -> (a -> a)
test h g = onInt h . onInt g
...
I'm trying to do some fusion in ghc, and I'd greatly appreciate help
with
the code below (which is simplified from fusion on linear maps).  I've
2008/6/7 Conal Elliott :
tried
...
every variation I can think of, and always something prevents the
fusion.
Help, please!  Thanks, - Conal
{-# OPTIONS_GHC -O2 -Wall -fglasgow-exts -ddump-simpl
-ddump-simpl-stats
#-}
-- {-# OPTIONS_GHC -ddump-simpl-iterations #-}
module F where
-- | Domain of a linear map.
class AsInt a where
  toInt   :: a -> Int
  fromInt :: Int -> a
{-# RULES
"toInt/fromInt"   forall m. toInt (fromInt m) = m
 #-}
{-# INLINE onInt #-}
onInt :: AsInt a => (Int -> Int) -> (a -> a)
onInt f = fromInt . f . toInt
test :: AsInt a => (Int -> Int) -> (Int -> Int) -> (a -> a)
test h g = onInt h . onInt g
-- The desired result:
--
--   test h g
--     == onInt h . onInt g
--     == (fromInt . h . toInt) . (fromInt . g . toInt)
--     == \ a -> (fromInt . h . toInt) ((fromInt . g . toInt) a)
--     == \ a -> (fromInt . h . toInt) (fromInt (g (toInt a)))
--     == \ a -> fromInt (h (toInt (fromInt (g (toInt a)))))
--     == \ a -> fromInt (h (g (toInt a)))
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--------------------------------------------------------------------------------
...
_______________________________________________
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http://www.haskell.org/mailman/listinfo/glasgow-haskell-users