module Language.Core.ElimDeadCode(elimDeadCode) where
import Language.Core.Core
import Language.Core.Printer()
import Language.Core.CoreUtils
import Control.Monad.Reader
import Data.List
import Data.Maybe
import qualified Data.Map as M
import qualified Data.Set as S
elimDeadCode :: Bool -> Module -> Module
elimDeadCode exports (Module mn tdefs vdefgs) = runReader (do
_st <- asks (\ (_,b,c) -> (b,c))
(usedVars, usedDcons, usedTcons) <- findUsed emptySet
(mkStartSet exports mn vdefgs)
id $ do
let isUsed (Vdef (v,_,_)) = v `S.member` usedVars
let newVdefgs = filterVdefgs isUsed vdefgs
let newTdefs = filter (tdefIsUsed usedTcons usedDcons) tdefs in
return $ Module mn newTdefs newVdefgs) ((mkVarEnv vdefgs), mkTyEnv tdefs, mkParentEnv tdefs)
tdefIsUsed :: S.Set (Qual Tcon) -> S.Set (Qual Dcon) -> Tdef -> Bool
tdefIsUsed tcs dcs (Data qtc _ cdefs) =
(qtc `S.member` tcs || any (\ (Constr qdc _ _) -> qdc `S.member` dcs) cdefs)
tdefIsUsed tcs _ (Newtype qtc qtc_co _ _) =
qtc `S.member` tcs || qtc_co `S.member` tcs
mkVarEnv :: [Vdefg] -> M.Map (Qual Var) Exp
mkVarEnv vgs =
let vdefs = flattenBinds vgs in
M.fromList [(v, e) | (Vdef (v, _, e)) <- vdefs]
mkTyEnv :: [Tdef] -> M.Map (Qual Tcon) [Ty]
mkTyEnv tdefs =
M.fromList ([(qtc, [ty]) | (Newtype qtc _ _ ty) <- tdefs]
++ [(qtc, [ty]) | (Newtype _ qtc _ ty) <- tdefs]
++ concatMap (\ td -> case td of
Data qtc _ cdefs -> [(qtc, concatMap
(\ (Constr _ _ ts) -> ts) cdefs)]
_ -> []) tdefs)
mkParentEnv :: [Tdef] -> M.Map (Qual Dcon) (Qual Tcon)
mkParentEnv tdefs = M.fromList [(qdc,qtc) | Data qtc _ cdefs <- tdefs,
Constr qdc _ _ <- cdefs]
findUsed :: DeadSet -> DeadSet -> DeadM DeadSet
findUsed _old@(oldVars,oldDcs,oldTcs) _new@(newVars,newDcs,newTcs) = do
let (todoVars, todoDcs, todoTcs) = ((S.\\) newVars oldVars, (S.\\) newDcs oldDcs, (S.\\) newTcs oldTcs)
let nextOld = (oldVars `S.union` todoVars, oldDcs `S.union` newDcs,
oldTcs `S.union` todoTcs)
nextStuff <- getVarsAndConsIn (todoVars, todoDcs, todoTcs)
if (S.null todoVars && S.null todoTcs)
then return nextOld
else findUsed nextOld nextStuff
getVarsAndConsIn :: (S.Set (Qual Var), S.Set (Qual Dcon), S.Set (Qual Tcon)) -> DeadM DeadSet
getVarsAndConsIn (vs, dcs, tcs) = do
vs1 <- mapM varsAndConsInOne (S.toList vs)
ts1 <- mapM varsAndConsInOne' (S.toList tcs)
ts2 <- mapM dconParent (S.toList dcs)
let (vs'::[S.Set (Qual Var)], dcs'::[S.Set (Qual Dcon)],
ts'::[S.Set (Qual Tcon)]) = unzip3 (vs1 ++ ts1 ++ ts2)
return (foldl' S.union S.empty vs', foldl' S.union S.empty dcs',
foldl' S.union S.empty ts')
dconParent :: Qual Dcon -> DeadM DeadSet
dconParent dc = do
parent <- findDconParent dc
return $ maybe emptySet (\ tc -> (S.empty,S.singleton dc,S.singleton tc))
parent
varsAndConsInOne :: Qual Var -> DeadM DeadSet
varsAndConsInOne vr = do
def <- findDefn vr
return $ maybe emptySet usedNamesExp def
varsAndConsInOne' :: Qual Tcon -> DeadM DeadSet
varsAndConsInOne' tc = do
ty <- findRepTy tc
return $ maybe emptySet (some usedNamesTy) ty
emptySet :: DeadSet
emptySet = (S.empty, S.empty, S.empty)
mkStartSet :: Bool -> AnMname -> [Vdefg] -> DeadSet
mkStartSet exports mn vds =
(S.fromList (filter ((== Just mn) . getModule) (if exports then exportedNames vds else [mainVar])),
S.empty, S.empty)
exportedNames :: [Vdefg] -> [Qual Var]
exportedNames vdefgs =
let vds = flattenBinds vdefgs in
filter isQual (ns vds)
where isQual = isJust . fst
ns = map (\ (Vdef (n,_,_)) -> n)
type DeadSet = (S.Set (Qual Var), S.Set (Qual Dcon), S.Set (Qual Tcon))
type DeadM = Reader (M.Map (Qual Var) Exp, M.Map (Qual Tcon) [Ty],
M.Map (Qual Dcon) (Qual Tcon))
aVar :: Qual Var -> DeadSet
aVar v = (S.singleton v,S.empty,S.empty)
aCon :: Qual Dcon -> DeadSet
aCon c = (S.empty,S.singleton c,S.empty)
aTcon :: Qual Tcon -> DeadSet
aTcon t = (S.empty,S.empty,S.singleton t)
findDefn :: Qual Var -> DeadM (Maybe Exp)
findDefn vr = asks ((M.lookup vr) . fst3)
findRepTy :: Qual Tcon -> DeadM (Maybe [Ty])
findRepTy tc = asks ((M.lookup tc) . snd3)
findDconParent :: Qual Dcon -> DeadM (Maybe (Qual Tcon))
findDconParent dc = asks ((M.lookup dc) . thrd3)
unionThree :: DeadSet -> DeadSet -> DeadSet
unionThree (a,b,c) (d,e,f) = (a `S.union` d, b `S.union` e, c `S.union` f)
usedNamesVdefg :: Vdefg -> DeadSet
usedNamesVdefg (Rec vds) = some usedNamesVdef vds
usedNamesVdefg (Nonrec vdef) = usedNamesVdef vdef
usedNamesVdef :: Vdef -> DeadSet
usedNamesVdef (Vdef (_,t,e)) = usedNamesTy t `unionThree` usedNamesExp e
usedNamesExp :: Exp -> DeadSet
usedNamesExp (Var v) = aVar v
usedNamesExp (Dcon d) = aCon d
usedNamesExp (Lit _) = emptySet
usedNamesExp (App a b) = someExps [a,b]
usedNamesExp (Appt e t) = usedNamesExp e `unionThree` usedNamesTy t
usedNamesExp (Lam _ e) = usedNamesExp e
usedNamesExp (Let vd e) = usedNamesVdefg vd `unionThree` usedNamesExp e
usedNamesExp (Case e _ t alts) = usedNamesExp e `unionThree`
usedNamesTy t `unionThree` usedNamesAlts alts
usedNamesExp (Cast e t) = usedNamesExp e `unionThree` usedNamesTy t
usedNamesExp (Note _ e) = usedNamesExp e
usedNamesExp (External _ t) = usedNamesTy t
usedNamesTy :: Ty -> DeadSet
usedNamesTy (Tvar _) = emptySet
usedNamesTy (Tcon t) = aTcon t
usedNamesTy (Tapp t u) = usedNamesTy t `unionThree` usedNamesTy u
usedNamesTy (Tforall _ t) = usedNamesTy t
usedNamesTy (TransCoercion t u) = usedNamesTy t `unionThree` usedNamesTy u
usedNamesTy (SymCoercion t) = usedNamesTy t
usedNamesTy (UnsafeCoercion t u) = usedNamesTy t `unionThree` usedNamesTy u
usedNamesTy (InstCoercion t u) = usedNamesTy t `unionThree` usedNamesTy u
usedNamesTy (LeftCoercion t) = usedNamesTy t
usedNamesTy (RightCoercion t) = usedNamesTy t
usedNamesAlts :: [Alt] -> DeadSet
usedNamesAlts = some go'
where go' (Acon dc _ _ e) = (aCon dc) `unionThree` (usedNamesExp e)
go' (Alit _ e) = usedNamesExp e
go' (Adefault e) = usedNamesExp e
some :: (a -> DeadSet) -> [a] -> DeadSet
some g = (foldl' (\ (a,b,c) (d,e,f) -> (a `S.union` d,b `S.union` e,c `S.union` f))
emptySet) . map g
someExps :: [Exp] -> DeadSet
someExps = some usedNamesExp
fst3 :: (a,b,c) -> a
fst3 (a,_,_) = a
snd3 :: (a,b,c) -> b
snd3 (_,b,_) = b
thrd3 :: (a,b,c) -> c
thrd3 (_,_,c)= c