idris-0.9.5: src/IRTS/Defunctionalise.hs
module IRTS.Defunctionalise(module IRTS.Defunctionalise,
module IRTS.Lang) where
import IRTS.Lang
import Core.TT
import Debug.Trace
import Data.Maybe
import Data.List
data DExp = DV LVar
| DApp Bool Name [DExp] -- True = tail call
| DLet Name DExp DExp -- name just for pretty printing
| DProj DExp Int
| DC Int Name [DExp]
| DCase DExp [DAlt]
| DConst Const
| DForeign FLang FType String [(FType, DExp)]
| DOp PrimFn [DExp]
| DNothing -- erased value, can be compiled to anything since it'll never
-- be inspected
| DError String
deriving Eq
data DAlt = DConCase Int Name [Name] DExp
| DConstCase Const DExp
| DDefaultCase DExp
deriving (Show, Eq)
data DDecl = DFun Name [Name] DExp -- name, arg names, definition
| DConstructor Name Int Int -- constructor name, tag, arity
deriving (Show, Eq)
type DDefs = Ctxt DDecl
defunctionalise :: Int -> LDefs -> DDefs
defunctionalise nexttag defs
= let all = toAlist defs
-- sort newcons so that EVAL and APPLY cons get sequential tags
newcons = sortBy conord $ concatMap toCons (getFn all)
eval = mkEval newcons
app = mkApply newcons
condecls = declare nexttag newcons in
addAlist (eval : app : condecls ++ (map (addApps defs) all)) emptyContext
where conord (n, _, _) (n', _, _) = compare n n'
getFn :: [(Name, LDecl)] -> [(Name, Int)]
getFn xs = mapMaybe fnData xs
where fnData (n, LFun _ args _) = Just (n, length args)
fnData _ = Nothing
-- To defunctionalise:
--
-- 1 Create a data constructor for each function
-- 2 Create a data constructor for each underapplication of a function
-- 3 Convert underapplications to their corresponding constructors
-- 4 Create an EVAL function which calls the appropriate function for data constructors
-- created as part of step 1
-- 5 Create an APPLY function which adds an argument to each underapplication (or calls
-- APPLY again for an exact application)
-- 6 Wrap overapplications in chains of APPLY
-- 7 Wrap unknown applications (i.e. applications of local variables) in chains of APPLY
-- 8 Add explicit EVAL to case, primitives, and foreign calls
addApps :: LDefs -> (Name, LDecl) -> (Name, DDecl)
addApps defs o@(n, LConstructor _ t a) = (n, DConstructor n t a)
addApps defs (n, LFun _ args e) = (n, DFun n args (aa args e))
where
aa :: [Name] -> LExp -> DExp
aa env (LV (Glob n)) | n `elem` env = DV (Glob n)
| otherwise = aa env (LApp False (LV (Glob n)) [])
-- aa env e@(LApp tc (MN 0 "EVAL") [a]) = e
aa env (LApp tc (LV (Glob n)) args)
= let args' = map (aa env) args in
case lookupCtxt Nothing n defs of
[LConstructor _ i ar] -> DApp tc n args'
[LFun _ as _] -> let arity = length as in
fixApply tc n args' arity
[] -> chainAPPLY (DV (Glob n)) args'
aa env (LLazyApp n args)
= let args' = map (aa env) args in
case lookupCtxt Nothing n defs of
[LConstructor _ i ar] -> DApp False n args'
[LFun _ as _] -> let arity = length as in
fixLazyApply n args' arity
[] -> chainAPPLY (DV (Glob n)) args'
aa env (LForce e) = eEVAL (aa env e)
aa env (LLet n v sc) = DLet n (aa env v) (aa (n : env) sc)
aa env (LCon i n args) = DC i n (map (aa env) args)
aa env (LProj t i) = DProj (eEVAL (aa env t)) i
aa env (LCase e alts) = DCase (eEVAL (aa env e)) (map (aaAlt env) alts)
aa env (LConst c) = DConst c
aa env (LForeign l t n args) = DForeign l t n (map (aaF env) args)
aa env (LOp LFork args) = DOp LFork (map (aa env) args)
aa env (LOp f args) = DOp f (map (eEVAL . (aa env)) args)
aa env LNothing = DNothing
aa env (LError e) = DError e
aaF env (t, e) = (t, eEVAL (aa env e))
aaAlt env (LConCase i n args e) = DConCase i n args (aa (args ++ env) e)
aaAlt env (LConstCase c e) = DConstCase c (aa env e)
aaAlt env (LDefaultCase e) = DDefaultCase (aa env e)
fixApply tc n args ar
| length args == ar = DApp tc n args
| length args < ar = DApp tc (mkUnderCon n (ar - length args)) args
| length args > ar = chainAPPLY (DApp tc n (take ar args)) (drop ar args)
fixLazyApply n args ar
| length args == ar = DApp False (mkFnCon n) args
| length args < ar = DApp False (mkUnderCon n (ar - length args)) args
| length args > ar = chainAPPLY (DApp False n (take ar args)) (drop ar args)
chainAPPLY f [] = f
chainAPPLY f (a : as) = chainAPPLY (DApp False (MN 0 "APPLY") [f, a]) as
eEVAL x = DApp False (MN 0 "EVAL") [x]
data EvalApply a = EvalCase a
| ApplyCase a
deriving Show
-- For a function name, generate a list of
-- data constuctors, and whether to handle them in EVAL or APPLY
toCons :: (Name, Int) -> [(Name, Int, EvalApply DAlt)]
toCons (n, i)
= (mkFnCon n, i,
EvalCase (DConCase (-1) (mkFnCon n) (take i (genArgs 0))
(eEVAL (DApp False n (map (DV . Glob) (take i (genArgs 0)))))))
: mkApplyCase n 0 i
mkApplyCase fname n ar | n == ar = []
mkApplyCase fname n ar
= let nm = mkUnderCon fname (ar - n) in
(nm, n, ApplyCase (DConCase (-1) nm (take n (genArgs 0))
(DApp False (mkUnderCon fname (ar - (n + 1)))
(map (DV . Glob) (take n (genArgs 0) ++
[MN 0 "arg"])))))
: mkApplyCase fname (n + 1) ar
mkEval :: [(Name, Int, EvalApply DAlt)] -> (Name, DDecl)
mkEval xs = (MN 0 "EVAL", DFun (MN 0 "EVAL") [MN 0 "arg"]
(mkBigCase (MN 0 "EVAL") 256 (DV (Glob (MN 0 "arg")))
(mapMaybe evalCase xs ++
[DDefaultCase (DV (Glob (MN 0 "arg")))])))
where
evalCase (n, t, EvalCase x) = Just x
evalCase _ = Nothing
mkApply :: [(Name, Int, EvalApply DAlt)] -> (Name, DDecl)
mkApply xs = (MN 0 "APPLY", DFun (MN 0 "APPLY") [MN 0 "fn", MN 0 "arg"]
(mkBigCase (MN 0 "APPLY")
256 (DApp False (MN 0 "EVAL")
[DV (Glob (MN 0 "fn"))])
(mapMaybe applyCase xs)))
where
applyCase (n, t, ApplyCase x) = Just x
applyCase _ = Nothing
declare :: Int -> [(Name, Int, EvalApply DAlt)] -> [(Name, DDecl)]
declare t xs = dec' t xs [] where
dec' t [] acc = reverse acc
dec' t ((n, ar, _) : xs) acc = dec' (t + 1) xs ((n, DConstructor n t ar) : acc)
genArgs i = MN i "P_c" : genArgs (i + 1)
mkFnCon n = MN 0 ("P_" ++ show n)
mkUnderCon n 0 = n
mkUnderCon n missing = MN missing ("U_" ++ show n)
instance Show DExp where
show e = show' [] e where
show' env (DV (Loc i)) = "var " ++ env!!i
show' env (DV (Glob n)) = show n
show' env (DApp _ e args) = show e ++ "(" ++
showSep ", " (map (show' env) args) ++")"
show' env (DLet n v e) = "let " ++ show n ++ " = " ++ show' env v ++ " in " ++
show' (env ++ [show n]) e
show' env (DC i n args) = show n ++ ")" ++ showSep ", " (map (show' env) args) ++ ")"
show' env (DProj t i) = show t ++ "!" ++ show i
show' env (DCase e alts) = "case " ++ show' env e ++ " of {\n\t" ++
showSep "\n\t| " (map (showAlt env) alts)
show' env (DConst c) = show c
show' env (DForeign lang ty n args)
= "foreign " ++ n ++ "(" ++ showSep ", " (map (show' env) (map snd args)) ++ ")"
show' env (DOp f args) = show f ++ "(" ++ showSep ", " (map (show' env) args) ++ ")"
show' env (DError str) = "error " ++ show str
show' env DNothing = "____"
showAlt env (DConCase _ n args e)
= show n ++ "(" ++ showSep ", " (map show args) ++ ") => "
++ show' env e
showAlt env (DConstCase c e) = show c ++ " => " ++ show' env e
showAlt env (DDefaultCase e) = "_ => " ++ show' env e
-- Divide up a large case expression so that each has a maximum of
-- 'max' branches
mkBigCase cn max arg branches
| length branches <= max = DCase arg branches
| otherwise = -- DCase arg branches -- until I think of something...
-- divide the branches into groups of at most max (by tag),
-- generate a new case and shrink, recursively
let bs = sortBy tagOrd branches
(all, def) = case (last bs) of
DDefaultCase t -> (init all, Just (DDefaultCase t))
_ -> (all, Nothing)
bss = groupsOf max all
cs = map mkCase bss in
DCase arg branches
where mkCase bs = DCase arg bs
tagOrd (DConCase t _ _ _) (DConCase t' _ _ _) = compare t t'
tagOrd (DConstCase c _) (DConstCase c' _) = compare c c'
tagOrd (DDefaultCase _) (DDefaultCase _) = EQ
tagOrd (DConCase _ _ _ _) (DDefaultCase _) = LT
tagOrd (DConCase _ _ _ _) (DConstCase _ _) = LT
tagOrd (DConstCase _ _) (DDefaultCase _) = LT
tagOrd (DDefaultCase _) (DConCase _ _ _ _) = GT
tagOrd (DConstCase _ _) (DConCase _ _ _ _) = GT
tagOrd (DDefaultCase _) (DConstCase _ _) = GT
groupsOf :: Int -> [DAlt] -> [[DAlt]]
groupsOf x [] = []
groupsOf x xs = let (batch, rest) = span (tagLT (x + tagHead xs)) xs in
batch : groupsOf x rest
where tagHead (DConstCase (I i) _ : _) = i
tagHead (DConCase t _ _ _ : _) = t
tagHead (DDefaultCase _ : _) = -1 -- must be the end
tagLT i (DConstCase (I j) _) = i < j
tagLT i (DConCase j _ _ _) = i < j
tagLT i (DDefaultCase _) = False
dumpDefuns :: DDefs -> String
dumpDefuns ds = showSep "\n" $ map showDef (toAlist ds)
where showDef (x, DFun fn args exp)
= show fn ++ "(" ++ showSep ", " (map show args) ++ ") = \n\t" ++
show exp ++ "\n"
showDef (x, DConstructor n t a) = "Constructor " ++ show n ++ " " ++ show t