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Merge pull request #92 from grin-compiler/32-trf-gub
Extended Syntax: generalized unboxing
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grin/src/Transformations/ExtendedSyntax/Optimising/GeneralizedUnboxing.hs
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{-# LANGUAGE LambdaCase, TupleSections, OverloadedStrings #-} | ||
module Transformations.ExtendedSyntax.Optimising.GeneralizedUnboxing where | ||
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import Data.Set (Set) | ||
import Data.Vector (Vector) | ||
import Data.Map.Strict (Map) | ||
import Data.Function (fix) | ||
import Data.Bifunctor (second) | ||
import Data.Functor.Infix ((<$$>)) | ||
import Data.Functor.Foldable as Foldable | ||
import Data.Maybe (catMaybes, mapMaybe, isJust) | ||
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import Lens.Micro.Platform | ||
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import qualified Data.Map.Strict as Map | ||
import qualified Data.Set as Set | ||
import qualified Data.Vector as Vector | ||
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import Transformations.ExtendedSyntax.Util (anaM, apoM) | ||
import Transformations.ExtendedSyntax.Names | ||
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import Grin.ExtendedSyntax.Grin | ||
import Grin.ExtendedSyntax.TypeEnv | ||
import Grin.ExtendedSyntax.Pretty | ||
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generalizedUnboxing :: TypeEnv -> Exp -> (Exp, ExpChanges) | ||
generalizedUnboxing te exp = if (null funs) | ||
then (exp, NoChange) | ||
else second | ||
(const NewNames) -- New functions are created, but NameM monad is not used | ||
(evalNameM exp (transformCalls funs te =<< transformReturns funs te exp)) | ||
where | ||
funs = functionsToUnbox te exp | ||
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-- TODO: Support tagless nodes. | ||
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tailCalls :: Exp -> Maybe [Name] | ||
tailCalls = cata collect where | ||
collect :: ExpF (Maybe [Name]) -> Maybe [Name] | ||
collect = \case | ||
DefF _ _ result -> result | ||
EBindF _ _ result -> result | ||
ECaseF _ alts -> nonEmpty $ concat $ catMaybes alts | ||
AltF _ _ result -> result | ||
SAppF f _ -> Just [f] | ||
e -> Nothing | ||
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nonEmpty :: [a] -> Maybe [a] | ||
nonEmpty [] = Nothing | ||
nonEmpty xs = Just xs | ||
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doesReturnAKnownProduct :: TypeEnv -> Name -> Bool | ||
doesReturnAKnownProduct = isJust <$$> returnsAUniqueTag | ||
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returnsAUniqueTag :: TypeEnv -> Name -> Maybe (Tag, Type) | ||
returnsAUniqueTag te name = do | ||
(tag, vs) <- te ^? function . at name . _Just . _1 . _T_NodeSet . to Map.toList . to singleton . _Just | ||
typ <- singleton (Vector.toList vs) | ||
pure (tag, T_SimpleType typ) | ||
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singleton :: [a] -> Maybe a | ||
singleton = \case | ||
[] -> Nothing | ||
[a] -> Just a | ||
_ -> Nothing | ||
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transitive :: (Ord a) => (a -> Set a) -> Set a -> Set a | ||
transitive f res0 = | ||
let res1 = res0 `Set.union` (Set.unions $ map f $ Set.toList res0) | ||
in if res1 == res0 | ||
then res0 | ||
else transitive f res1 | ||
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-- TODO: Remove the fix combinator, explore the function | ||
-- dependency graph and rewrite disqualify steps based on that. | ||
functionsToUnbox :: TypeEnv -> Exp -> Set Name | ||
functionsToUnbox te (Program exts defs) = result where | ||
funName (Def n _ _) = n | ||
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tailCallsMap :: Map Name [Name] | ||
tailCallsMap = Map.fromList $ mapMaybe (\e -> (,) (funName e) <$> tailCalls e) defs | ||
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tranisitiveTailCalls :: Map Name (Set Name) | ||
tranisitiveTailCalls = Map.fromList $ map (\k -> (k, transitive inTailCalls (Set.singleton k))) $ Map.keys tailCallsMap | ||
where | ||
inTailCalls :: Name -> Set Name | ||
inTailCalls n = maybe mempty Set.fromList $ Map.lookup n tailCallsMap | ||
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nonCandidateTailCallMap = Map.withoutKeys tranisitiveTailCalls result0 | ||
candidateCalledByNonCandidate = (Set.unions $ Map.elems nonCandidateTailCallMap) `Set.intersection` result0 | ||
result = result0 `Set.difference` candidateCalledByNonCandidate | ||
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result0 = Set.fromList $ step initial | ||
initial = map funName $ filter (doesReturnAKnownProduct te . funName) defs | ||
disqualify candidates = filter | ||
(\candidate -> case Map.lookup candidate tailCallsMap of | ||
Nothing -> True | ||
Just calls -> all (`elem` candidates) calls) | ||
candidates | ||
step = fix $ \rec x0 -> | ||
let x1 = disqualify x0 in | ||
if x0 == x1 | ||
then x0 | ||
else rec x1 | ||
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updateTypeEnv :: Set Name -> TypeEnv -> TypeEnv | ||
updateTypeEnv funs te = te & function %~ unboxFun | ||
where | ||
unboxFun = Map.fromList . map changeFun . Map.toList | ||
changeFun (n, ts@(ret, params)) = | ||
if Set.member n funs | ||
then (,) (n <> ".unboxed") | ||
$ maybe ts ((\t -> (t, params)) . T_SimpleType) $ | ||
ret ^? _T_NodeSet | ||
. to Map.elems | ||
. to singleton | ||
. _Just | ||
. to Vector.toList | ||
. to singleton | ||
. _Just | ||
else (n, ts) | ||
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transformReturns :: Set Name -> TypeEnv -> Exp -> NameM Exp | ||
transformReturns toUnbox te exp = apoM builder (Nothing, exp) where | ||
builder :: (Maybe (Tag, Type), Exp) -> NameM (ExpF (Either Exp (Maybe (Tag, Type), Exp))) | ||
builder (mTagType, exp0) = case exp0 of | ||
Def name params body | ||
| Set.member name toUnbox -> pure $ DefF name params (Right (returnsAUniqueTag te name, body)) | ||
| otherwise -> pure $ DefF name params (Left body) | ||
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-- Always skip the lhs of a bind. | ||
EBind lhs pat rhs -> pure $ EBindF (Left lhs) pat (Right (mTagType, rhs)) | ||
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-- Remove the tag from the value | ||
SReturn (ConstTagNode tag [arg]) -> pure $ SReturnF (Var arg) | ||
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-- Rewrite a node variable | ||
simpleExp | ||
-- fromJust works, as when we enter the processing of body of the | ||
-- expression only happens with the provided tag. | ||
| canUnbox simpleExp | ||
, Just (tag, typ) <- mTagType | ||
-> do | ||
freshName <- deriveNewName $ "unboxed." <> (showTS $ PP tag) | ||
asPatName <- deriveWildCard | ||
pure . SBlockF . Left $ EBind simpleExp (AsPat tag [freshName] asPatName) (SReturn $ Var freshName) | ||
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rest -> pure (Right . (,) mTagType <$> project rest) | ||
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-- NOTE: SApp is handled by transformCalls | ||
canUnbox :: SimpleExp -> Bool | ||
canUnbox = \case | ||
SApp n ps -> n `Set.notMember` toUnbox | ||
SReturn{} -> True | ||
SFetch{} -> True | ||
_ -> False | ||
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transformCalls :: Set Name -> TypeEnv -> Exp -> NameM Exp | ||
transformCalls toUnbox typeEnv exp = anaM builderM (True, Nothing, exp) where | ||
builderM :: (Bool, Maybe Name, Exp) -> NameM (ExpF (Bool, Maybe Name, Exp)) | ||
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builderM (isRightExp, mDefName, e) = case e of | ||
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Def name params body | ||
-> pure $ DefF (if Set.member name toUnbox then name <> ".unboxed" else name) params (True, Just name, body) | ||
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-- track the control flow | ||
EBind lhs pat rhs -> pure $ EBindF (False, mDefName, lhs) pat (isRightExp, mDefName, rhs) | ||
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SApp name params | ||
| Set.member name toUnbox | ||
, Just defName <- mDefName | ||
, unboxedName <- name <> ".unboxed" | ||
, Just (tag, fstType) <- returnsAUniqueTag typeEnv name | ||
-> if Set.member defName toUnbox && isRightExp | ||
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-- from candidate to candidate: tailcalls do not need a transform | ||
then pure $ SAppF unboxedName params | ||
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-- from outside to candidate | ||
else do | ||
freshName <- deriveNewName $ "unboxed." <> (showTS $ PP tag) | ||
pure . SBlockF . (isRightExp, mDefName,) $ | ||
EBind (SApp unboxedName params) (VarPat freshName) (SReturn $ ConstTagNode tag [freshName]) | ||
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rest -> pure ((isRightExp, mDefName,) <$> project rest) |
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