liquidhaskell-boot-0.9.6.3: src/Language/Haskell/Liquid/Transforms/ANF.hs
--------------------------------------------------------------------------------
-- | Convert GHC Core into Administrative Normal Form (ANF) --------------------
--------------------------------------------------------------------------------
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE NoMonomorphismRestriction #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ViewPatterns #-}
module Language.Haskell.Liquid.Transforms.ANF (anormalize) where
import Debug.Trace (trace)
import Prelude hiding (error)
import Language.Haskell.Liquid.GHC.TypeRep
import Liquid.GHC.API as Ghc hiding ( mkTyArg
, showPpr
, DsM
, panic)
import qualified Liquid.GHC.API as Ghc
import Control.Monad (forM)
import Control.Monad.State.Lazy
import System.Console.CmdArgs.Verbosity (whenLoud)
import qualified Language.Fixpoint.Types as F
import Language.Haskell.Liquid.UX.Config as UX
import qualified Language.Haskell.Liquid.Misc as Misc
import Language.Haskell.Liquid.GHC.Misc as GM
import Language.Haskell.Liquid.Transforms.Rec
import Language.Haskell.Liquid.Transforms.InlineAux
import Language.Haskell.Liquid.Transforms.Rewrite
import Language.Haskell.Liquid.Types.Errors
import qualified Language.Haskell.Liquid.GHC.SpanStack as Sp
import qualified Language.Haskell.Liquid.GHC.Resugar as Rs
import Data.Maybe (fromMaybe)
import Data.List (sortBy, (\\))
import qualified Text.Printf as Printf
import Data.Hashable
import Data.HashMap.Strict (HashMap)
import qualified Data.HashMap.Strict as HM
--------------------------------------------------------------------------------
-- | A-Normalize a module ------------------------------------------------------
--------------------------------------------------------------------------------
anormalize :: UX.Config -> HscEnv -> ModGuts -> IO [CoreBind]
--------------------------------------------------------------------------------
anormalize cfg hscEnv modGuts = do
whenLoud $ do
putStrLn "***************************** GHC CoreBinds ***************************"
putStrLn $ GM.showCBs untidy (mg_binds modGuts)
putStrLn "***************************** REC CoreBinds ***************************"
putStrLn $ GM.showCBs untidy orig_cbs
putStrLn "***************************** RWR CoreBinds ***************************"
putStrLn $ GM.showCBs untidy rwr_cbs
fromMaybe err . snd <$> initDsWithModGuts hscEnv modGuts act -- hscEnv m grEnv tEnv emptyFamInstEnv act
where
err = panic Nothing "Oops, cannot A-Normalize GHC Core!"
act = Misc.concatMapM (normalizeTopBind γ0) rwr_cbs
γ0 = emptyAnfEnv cfg
rwr_cbs = rewriteBinds cfg orig_cbs
orig_cbs = transformRecExpr inl_cbs
inl_cbs = inlineAux cfg (mg_module modGuts) $ mg_binds modGuts
untidy = UX.untidyCore cfg
--------------------------------------------------------------------------------
-- | A-Normalize a @CoreBind@ --------------------------------------------------
--------------------------------------------------------------------------------
-- Can't make the below default for normalizeBind as it
-- fails tests/pos/lets.hs due to GHCs odd let-bindings
normalizeTopBind :: AnfEnv -> Bind CoreBndr -> Ghc.DsM [CoreBind]
normalizeTopBind γ (NonRec x e)
= do e' <- runDsM $ evalStateT (stitch γ e) (DsST [])
return [normalizeTyVars $ NonRec x e']
normalizeTopBind γ (Rec xes)
= do xes' <- runDsM $ execStateT (normalizeBind γ (Rec xes)) (DsST [])
return $ map normalizeTyVars (st_binds xes')
normalizeTyVars :: Bind Id -> Bind Id
normalizeTyVars (NonRec x e) = NonRec (setVarType x t') $ normalizeForAllTys e
where
t' = subst msg as as' bt
msg = "WARNING: unable to renameVars on " ++ GM.showPpr x
as' = fst $ splitForAllTyCoVars $ exprType e
(as, bt) = splitForAllTyCoVars (varType x)
normalizeTyVars (Rec xes) = Rec xes'
where
nrec = normalizeTyVars <$> (uncurry NonRec <$> xes)
xes' = (\case NonRec x e -> (x, e); _ -> impossible Nothing "This cannot happen") <$> nrec
subst :: String -> [TyVar] -> [TyVar] -> Type -> Type
subst msg as as' bt
| length as == length as'
= mkForAllTys (mkTyArg <$> as') $ substTy su bt
| otherwise
= trace msg $ mkForAllTys (mkTyArg <$> as) bt
where su = mkTvSubstPrs $ zip as (mkTyVarTys as')
-- | eta-expand CoreBinds with quantified types
normalizeForAllTys :: CoreExpr -> CoreExpr
normalizeForAllTys e = case e of
Lam b _ | isTyVar b
-> e
_ -> mkLams tvs (mkTyApps e (map mkTyVarTy tvs))
where
(tvs, _) = splitForAllTyCoVars (exprType e)
newtype DsM a = DsM {runDsM :: Ghc.DsM a}
deriving (Functor, Monad, MonadUnique, Applicative)
newtype DsST = DsST { st_binds :: [CoreBind] }
type DsMW = StateT DsST DsM
------------------------------------------------------------------
normalizeBind :: AnfEnv -> CoreBind -> DsMW ()
------------------------------------------------------------------
normalizeBind γ (NonRec x e)
= do e' <- normalize γ e
add [NonRec x e']
normalizeBind γ (Rec xes)
= do es' <- mapM (stitch γ) es
add [Rec (zip xs es')]
where
(xs, es) = unzip xes
--------------------------------------------------------------------
normalizeName :: AnfEnv -> CoreExpr -> DsMW CoreExpr
--------------------------------------------------------------------
-- normalizeNameDebug γ e
-- = liftM (tracePpr ("normalizeName" ++ showPpr e)) $ normalizeName γ e
normalizeName γ e@(Lit l)
| shouldNormalize l
= normalizeLiteral γ e
| otherwise
= return e
normalizeName γ (Var x)
= return $ Var (lookupAnfEnv γ x x)
normalizeName _ e@(Type _)
= return e
normalizeName γ e@(Coercion _)
= do x <- lift $ freshNormalVar γ $ exprType e
add [NonRec x e]
return $ Var x
normalizeName γ (Tick tt e)
= do e' <- normalizeName (γ `at` tt) e
return $ Tick tt e'
normalizeName γ e
= do e' <- normalize γ e
x <- lift $ freshNormalVar γ $ exprType e
add [NonRec x e']
return $ Var x
shouldNormalize :: Literal -> Bool
shouldNormalize (LitNumber {}) = True
shouldNormalize (LitString {}) = True
shouldNormalize _ = False
add :: [CoreBind] -> DsMW ()
add w = modify $ \s -> s { st_binds = st_binds s ++ w}
--------------------------------------------------------------------------------
normalizeLiteral :: AnfEnv -> CoreExpr -> DsMW CoreExpr
--------------------------------------------------------------------------------
normalizeLiteral γ e =
do x <- lift $ freshNormalVar γ $ exprType e
add [NonRec x e]
return $ Var x
--------------------------------------------------------------------------------
normalize :: AnfEnv -> CoreExpr -> DsMW CoreExpr
--------------------------------------------------------------------------------
normalize γ e
| UX.patternFlag γ
, Just p <- Rs.lift e
= normalizePattern γ p
normalize γ (Lam x e) | isTyVar x
= do e' <- normalize γ e
return $ Lam x e'
normalize γ (Lam x e)
= do e' <- stitch γ e
return $ Lam x e'
normalize γ (Let b e)
= do normalizeBind γ b
normalize γ e
-- Need to float bindings all the way up to the top
-- Due to GHCs odd let-bindings (see tests/pos/lets.hs)
normalize γ (Case e x t as)
= do n <- normalizeName γ e
x' <- lift $ freshNormalVar γ τx -- rename "wild" to avoid shadowing
let γ' = extendAnfEnv γ x x'
as' <- forM as $ \(Alt c xs e') -> fmap (Alt c xs) (stitch (incrCaseDepth c γ') e')
as'' <- lift $ expandDefaultCase γ τx as'
return $ Case n x' t as''
where τx = GM.expandVarType x
normalize γ (Var x)
= return $ Var (lookupAnfEnv γ x x)
normalize _ e@(Lit _)
= return e
normalize _ e@(Type _)
= return e
normalize γ (Cast e τ)
= do e' <- normalizeName γ e
return $ Cast e' τ
normalize γ (App e1 e2@(Type _))
= do e1' <- normalize γ e1
e2' <- normalize γ e2
return $ App e1' e2'
normalize γ (App e1 e2)
= do e1' <- normalize γ e1
n2 <- normalizeName γ e2
return $ App e1' n2
normalize γ (Tick tt e)
= do e' <- normalize (γ `at` tt) e
return $ Tick tt e'
normalize _ (Coercion c)
= return $ Coercion c
--------------------------------------------------------------------------------
stitch :: AnfEnv -> CoreExpr -> DsMW CoreExpr
--------------------------------------------------------------------------------
stitch γ e
= do bs' <- get
modify $ \s -> s { st_binds = [] }
e' <- normalize γ e
bs <- st_binds <$> get
put bs'
-- See Note [Shape of normalized terms]
let (tvs, e'') = collectTyBinders e'
return $ mkLams tvs (mkCoreLets bs e'')
-- Note [Shape of normalized terms]
--
-- The termination checker in
-- Language.Haskell.Liquid.Constraint.Termination.collectArguments expects the
-- type binders to come before lets:
--
-- > \ (@a) -> let ... in \ b c d -> ...
--
-- Therefore, stitch makes sure to insert new lets after the type binders
--
-- > \ (@a) -> let lqanf... = ... in let ... in \ b c d -> ...
--
_mkCoreLets' :: [CoreBind] -> CoreExpr -> CoreExpr
_mkCoreLets' bs e = mkCoreLets bs1 e1
where
(e1, bs1) = GM.tracePpr "MKCORELETS" (e, bs)
--------------------------------------------------------------------------------
normalizePattern :: AnfEnv -> Rs.Pattern -> DsMW CoreExpr
--------------------------------------------------------------------------------
normalizePattern γ p@(Rs.PatBind {}) = do
-- don't normalize the >>= itself, we have a special typing rule for it
e1' <- normalize γ (Rs.patE1 p)
e2' <- stitch γ (Rs.patE2 p)
return $ Rs.lower p { Rs.patE1 = e1', Rs.patE2 = e2' }
normalizePattern γ p@(Rs.PatReturn {}) = do
e' <- normalize γ (Rs.patE p)
return $ Rs.lower p { Rs.patE = e' }
normalizePattern _ p@(Rs.PatProject {}) =
return (Rs.lower p)
normalizePattern γ p@(Rs.PatSelfBind {}) = do
normalize γ (Rs.patE p)
normalizePattern γ p@(Rs.PatSelfRecBind {}) = do
e' <- normalize γ (Rs.patE p)
return $ Rs.lower p { Rs.patE = e' }
--------------------------------------------------------------------------------
expandDefault :: AnfEnv -> Bool
--------------------------------------------------------------------------------
expandDefault γ = aeCaseDepth γ <= maxCaseExpand γ
--------------------------------------------------------------------------------
expandDefaultCase :: AnfEnv
-> Type
-> [CoreAlt]
-> DsM [CoreAlt]
--------------------------------------------------------------------------------
expandDefaultCase γ tyapp zs@(Alt DEFAULT _ _ : _) | expandDefault γ
= expandDefaultCase' γ tyapp zs
expandDefaultCase γ tyapp@(TyConApp tc _) z@(Alt DEFAULT _ _:dcs)
= case tyConDataCons_maybe tc of
Just ds -> do let ds' = ds \\ [ d | Alt (DataAlt d) _ _ <- dcs]
let n = length ds'
if n == 1
then expandDefaultCase' γ tyapp z
else if maxCaseExpand γ /= 2
then return z
else return (trace (expandMessage False γ n) z)
Nothing -> return z --
expandDefaultCase _ _ z
= return z
expandDefaultCase'
:: AnfEnv -> Type -> [CoreAlt] -> DsM [CoreAlt]
expandDefaultCase' γ t (Alt DEFAULT _ e : dcs)
| Just dtss <- GM.defaultDataCons t ((\(Alt dc _ _) -> dc) <$> dcs) = do
dcs' <- warnCaseExpand γ <$> forM dtss (cloneCase γ e)
return $ sortCases (dcs' ++ dcs)
expandDefaultCase' _ _ z
= return z
cloneCase :: AnfEnv -> CoreExpr -> (DataCon, [TyVar], [Type]) -> DsM CoreAlt
cloneCase γ e (d, as, ts) = do
xs <- mapM (freshNormalVar γ) ts
return (Alt (DataAlt d) (as ++ xs) e)
sortCases :: [CoreAlt] -> [CoreAlt]
sortCases = sortBy Ghc.cmpAlt
warnCaseExpand :: AnfEnv -> [a] -> [a]
warnCaseExpand γ xs
| 10 < n = trace (expandMessage True γ n) xs
| otherwise = xs
where
n = length xs
expandMessage :: Bool -> AnfEnv -> Int -> String
expandMessage expand γ n = unlines [msg1, msg2]
where
msg1 = Printf.printf "WARNING: (%s) %s DEFAULT with %d cases at depth %d" (showPpr sp) v1 n d
msg2 = Printf.printf "%s expansion with --max-case-expand=%d" v2 d'
(v1, v2, d')
| expand = ("Expanding" , "Disable", d-1) :: (String, String, Int)
| otherwise = ("Not expanding", "Enable" , d+1)
d = aeCaseDepth γ
sp = Sp.srcSpan (aeSrcSpan γ)
--------------------------------------------------------------------------------
-- | ANF Environments ----------------------------------------------------------
--------------------------------------------------------------------------------
freshNormalVar :: AnfEnv -> Type -> DsM Id
freshNormalVar γ t = do
u <- getUniqueM
let i = getKey u
let sp = Sp.srcSpan (aeSrcSpan γ)
return (mkUserLocal (anfOcc i) u Ghc.ManyTy t sp)
anfOcc :: Int -> OccName
anfOcc = mkVarOccFS . GM.symbolFastString . F.intSymbol F.anfPrefix
data AnfEnv = AnfEnv
{ aeVarEnv :: HashMap StableId Id
-- ^ A mapping between a 'StableId' (see below) and an 'Id'.
, aeSrcSpan :: Sp.SpanStack
, aeCfg :: UX.Config
, aeCaseDepth :: !Int
}
-- | A \"stable\" 'Id'. When transforming 'Core' into ANF notation, we need to keep around a mapping between
-- a particular 'Var' (typically an 'Id') and an 'Id'. Previously this was accomplished using a 'VarEnv',
-- a GHC data structure where keys are 'Unique's. Working with 'Unique' in GHC is not always robust enough
-- when it comes to LH. First of all, the /way/ 'Unique's are constructed might change between GHC versions,
-- and they are not stable between rebuilds/compilations. In the case of this module, in GHC 9 the test
-- BST.hs was failing because two different 'Id's, namely \"wild_X2\" and \"dOrd_X2\" were being given the
-- same 'Unique' by GHC (i.e. \"X2\") which was causing the relevant entry to be overwritten in the 'AnfEnv'
-- causing a unification error.
--
-- A 'StableId' is simply a wrapper over an 'Id' with a different 'Eq' instance that really guarantee
-- uniqueness (for our purposes, anyway).
newtype StableId = StableId Id
instance Eq StableId where
(StableId id1) == (StableId id2) =
-- We first use the default 'Eq' instance, which works on uniques (basically, integers) and is
-- efficient. If we get 'False' it means those 'Unique' are really different, but if we get 'True',
-- we need to be /really/ sure that's the case by using the 'stableNameCmp' function on the 'Name's.
-- Nothing to do when id1 == id2 as the uniques are /really/ different.
(id1 == id2) && (stableNameCmp (getName id1) (getName id2) == EQ) -- Avoid unique clashing.
-- For the 'Hashable' instance, we rely on the 'Unique'. This means in pratice there is a tiny chance
-- of collision, but this should only marginally affects the efficiency of the data structure.
instance Hashable StableId where
hashWithSalt s (StableId id1) = hashWithSalt s (getKey $ getUnique id1)
-- Shows this 'StableId' by also outputting the associated unique.
instance Show StableId where
show (StableId id1) = nameStableString (getName id1) <> "_" <> show (getUnique id1)
instance UX.HasConfig AnfEnv where
getConfig = aeCfg
emptyAnfEnv :: UX.Config -> AnfEnv
emptyAnfEnv cfg = AnfEnv
{ aeVarEnv = mempty
, aeSrcSpan = Sp.empty
, aeCfg = cfg
, aeCaseDepth = 1
}
lookupAnfEnv :: AnfEnv -> Id -> Id -> Id
lookupAnfEnv γ x (StableId -> y) = HM.lookupDefault x y (aeVarEnv γ)
extendAnfEnv :: AnfEnv -> Id -> Id -> AnfEnv
extendAnfEnv γ (StableId -> x) y = γ { aeVarEnv = HM.insert x y (aeVarEnv γ) }
incrCaseDepth :: AltCon -> AnfEnv -> AnfEnv
incrCaseDepth DEFAULT γ = γ { aeCaseDepth = 1 + aeCaseDepth γ }
incrCaseDepth _ γ = γ
at :: AnfEnv -> CoreTickish -> AnfEnv
at γ tt = γ { aeSrcSpan = Sp.push (Sp.Tick tt) (aeSrcSpan γ)}