inspection-testing-0.4.5.0: src/Test/Inspection/Core.hs
-- | This module implements some analyses of Core expressions necessary for
-- "Test.Inspection". Normally, users of this package can ignore this module.
{-# LANGUAGE CPP, FlexibleContexts #-}
module Test.Inspection.Core
( slice
, pprSlice
, pprSliceDifference
, eqSlice
, freeOfType
, freeOfTerm
, doesNotAllocate
, doesNotContainTypeClasses
) where
#if MIN_VERSION_ghc(9,0,0)
import GHC.Core
import GHC.Core.Utils
import GHC.Core.TyCo.Rep
import GHC.Core.Type
import GHC.Types.Var as Var
import GHC.Types.Id
import GHC.Types.Name
import GHC.Types.Var.Env
import GHC.Utils.Outputable as Outputable
import GHC.Core.Ppr
import GHC.Core.Coercion
import GHC.Utils.Misc
import GHC.Core.DataCon
import GHC.Core.TyCon (TyCon, isClassTyCon)
#else
import CoreSyn
import CoreUtils
import TyCoRep
import Type
import Var
import Id
import Name
import VarEnv
import Outputable
import PprCore
import Coercion
import Util
import DataCon
import TyCon (TyCon, isClassTyCon)
#endif
import qualified Data.Set as S
import Control.Monad.State.Strict
import Control.Monad.Trans.Maybe
import Data.List (nub)
import Data.Maybe
type Slice = [(Var, CoreExpr)]
-- | Selects those bindings that define the given variable (with this variable first)
slice :: [(Var, CoreExpr)] -> Var -> Slice
slice binds v
| Just e <- lookup v binds
= (v,e) : [(v',e) | (v',e) <- binds, v' /= v, v' `S.member` used ]
| otherwise
= error "slice: cannot find given variable in bindings"
where
used = execState (goV v) S.empty
local = S.fromList (map fst binds)
goV v | v `S.member` local = do
seen <- gets (v `S.member`)
unless seen $ do
modify (S.insert v)
let Just e = lookup v binds
go e
| otherwise = return ()
go (Var v) = goV v
go (Lit _ ) = pure ()
go (App e arg) | isTyCoArg arg = go e
go (App e arg) = go e >> go arg
go (Lam _ e) = go e
go (Let bind body) = mapM_ go (rhssOfBind bind) >> go body
go (Case s _ _ alts) = go s >> mapM_ goA alts
go (Cast e _) = go e
go (Tick _ e) = go e
go (Type _) = pure ()
go (Coercion _) = pure ()
goA (_, _, e) = go e
-- | Pretty-print a slice
pprSlice :: Slice -> SDoc
pprSlice slice =
withLessDetail $ pprCoreBindings [ NonRec v e | (v,e) <- slice ]
-- | Pretty-print two slices, after removing variables occurring in both
pprSliceDifference :: Slice -> Slice -> SDoc
pprSliceDifference slice1 slice2 =
hang (text "LHS" Outputable.<> colon) 4 (pprSlice slice1') $$
hang (text "RHS" Outputable.<> colon) 4 (pprSlice slice2')
where
both = S.intersection (S.fromList (map fst slice1)) (S.fromList (map fst slice2))
slice1' = filter (\(v,_) -> v `S.notMember` both) slice1
slice2' = filter (\(v,_) -> v `S.notMember` both) slice2
withLessDetail :: SDoc -> SDoc
#if MIN_VERSION_GLASGOW_HASKELL(8,2,0,0) && !MIN_VERSION_GLASGOW_HASKELL(9,0,0,0)
withLessDetail sdoc = sdocWithDynFlags $ \dflags ->
withPprStyle (defaultUserStyle dflags) sdoc
#else
withLessDetail sdoc = withPprStyle defaultUserStyle sdoc
#endif
type VarPair = (Var, Var)
type VarPairSet = S.Set VarPair
-- | This is a heuristic, which only works if both slices
-- have auxiliary variables in the right order.
-- (This is mostly to work-around the buggy CSE in GHC-8.0)
-- It also breaks if there is shadowing.
eqSlice :: Bool {- ^ ignore types and hpc ticks -} -> Slice -> Slice -> Bool
eqSlice _ slice1 slice2 | null slice1 || null slice2 = null slice1 == null slice2
-- Mostly defensive programming (slices should not be empty)
eqSlice it slice1 slice2
= step (S.singleton (fst (head slice1), fst (head slice2))) S.empty
where
step :: VarPairSet -> VarPairSet -> Bool
step wanted done
| wanted `S.isSubsetOf` done
= True -- done
| (x,y) : _ <- S.toList (wanted `S.difference` done)
, (Just _, wanted') <- runState (runMaybeT (equate x y)) wanted
= step wanted' (S.insert (x,y) done)
| otherwise
= False
equate :: Var -> Var -> MaybeT (State VarPairSet) ()
equate x y
| Just e1 <- lookup x slice1
, Just x' <- essentiallyVar e1
, x' `elem` map fst slice1
= lift $ modify (S.insert (x',y))
| Just e2 <- lookup y slice2
, Just y' <- essentiallyVar e2
, y' `elem` map fst slice2
= lift $ modify (S.insert (x,y'))
| Just e1 <- lookup x slice1
, Just e2 <- lookup y slice2
= go (mkRnEnv2 emptyInScopeSet) e1 e2
equate _ _ = mzero
equated :: Var -> Var -> MaybeT (State VarPairSet) ()
equated x y | x == y = return ()
equated x y = lift $ modify (S.insert (x,y))
essentiallyVar :: CoreExpr -> Maybe Var
essentiallyVar (App e a) | it, isTyCoArg a = essentiallyVar e
essentiallyVar (Lam v e) | it, isTyCoVar v = essentiallyVar e
essentiallyVar (Cast e _) | it = essentiallyVar e
#if MIN_VERSION_ghc(9,0,0)
essentiallyVar (Case s _ _ [(_, _, e)]) | it, isUnsafeEqualityProof s = essentiallyVar e
#endif
essentiallyVar (Var v) = Just v
essentiallyVar (Tick HpcTick{} e) | it = essentiallyVar e
essentiallyVar _ = Nothing
go :: RnEnv2 -> CoreExpr -> CoreExpr -> MaybeT (State (S.Set (Var,Var))) ()
go env (Var v1) (Var v2) | rnOccL env v1 == rnOccR env v2 = pure ()
| otherwise = equated v1 v2
go _ (Lit lit1) (Lit lit2) = guard $ lit1 == lit2
go env (Type t1) (Type t2) = guard $ eqTypeX env t1 t2
go env (Coercion co1) (Coercion co2) = guard $ eqCoercionX env co1 co2
go env (Cast e1 _) e2 | it = go env e1 e2
go env e1 (Cast e2 _) | it = go env e1 e2
#if MIN_VERSION_ghc(9,0,0)
go env (Case s _ _ [(_, _, e1)]) e2 | it, isUnsafeEqualityProof s = go env e1 e2
go env e1 (Case s _ _ [(_, _, e2)]) | it, isUnsafeEqualityProof s = go env e1 e2
#endif
go env (Cast e1 co1) (Cast e2 co2) = do guard (eqCoercionX env co1 co2)
go env e1 e2
go env (App e1 a) e2 | it, isTyCoArg a = go env e1 e2
go env e1 (App e2 a) | it, isTyCoArg a = go env e1 e2
go env (App f1 a1) (App f2 a2) = go env f1 f2 >> go env a1 a2
go env (Tick HpcTick{} e1) e2 | it = go env e1 e2
go env e1 (Tick HpcTick{} e2) | it = go env e1 e2
go env (Tick n1 e1) (Tick n2 e2) = guard (go_tick env n1 n2) >> go env e1 e2
go env (Lam b e1) e2 | it, isTyCoVar b = go env e1 e2
go env e1 (Lam b e2) | it, isTyCoVar b = go env e1 e2
go env (Lam b1 e1) (Lam b2 e2)
= do guard (it || eqTypeX env (varType b1) (varType b2))
-- False for Id/TyVar combination
go (rnBndr2 env b1 b2) e1 e2
go env (Let (NonRec v1 r1) e1) (Let (NonRec v2 r2) e2)
= do go env r1 r2 -- No need to check binder types, since RHSs match
go (rnBndr2 env v1 v2) e1 e2
go env (Let (Rec ps1) e1) (Let (Rec ps2) e2)
= do guard $ equalLength ps1 ps2
sequence_ $ zipWith (go env') rs1 rs2
go env' e1 e2
where
(bs1,rs1) = unzip ps1
(bs2,rs2) = unzip ps2
env' = rnBndrs2 env bs1 bs2
go env (Case e1 b1 t1 a1) (Case e2 b2 t2 a2)
| null a1 -- See Note [Empty case alternatives] in TrieMap
= do guard (null a2)
go env e1 e2
guard (it || eqTypeX env t1 t2)
| otherwise
= do guard $ equalLength a1 a2
go env e1 e2
sequence_ $ zipWith (go_alt (rnBndr2 env b1 b2)) a1 a2
go _ _ _ = guard False
-----------
go_alt env (c1, bs1, e1) (c2, bs2, e2)
= guard (c1 == c2) >> go (rnBndrs2 env bs1 bs2) e1 e2
go_tick :: RnEnv2 -> Tickish Id -> Tickish Id -> Bool
go_tick env (Breakpoint lid lids) (Breakpoint rid rids)
= lid == rid && map (rnOccL env) lids == map (rnOccR env) rids
go_tick _ l r = l == r
-- | Returns @True@ if the given core expression mentions no type constructor
-- anywhere that has the given name.
freeOfType :: Slice -> [Name] -> Maybe (Var, CoreExpr)
freeOfType slice tcNs =
fmap (\(a,b,_) -> (a,b))
$ allTyCons (\tc -> getName tc `notElem` tcNs) slice
-- | Check if all type constructors in a slice satisfy the given predicate.
-- Returns the binder, expression and failing constructors triple on failure.
allTyCons :: (TyCon -> Bool) -> Slice -> Maybe (Var, CoreExpr, [TyCon])
allTyCons ignore slice =
listToMaybe
[(v, e, nub tcs) | (v, e) <- slice, let tcs = go e, not (null tcs)]
where
goV v = goT (varType v)
go (Var v) = goV v
go (Lit _) = []
go (App e a) = go e ++ go a
go (Lam b e) = goV b ++ go e
go (Let bind body) = concatMap goB (flattenBinds [bind]) ++ go body
go (Case s b _ alts) = go s ++ goV b ++ concatMap goA alts
go (Cast e _) = go e
go (Tick _ e) = go e
go (Type t) = (goT t)
go (Coercion _) = []
goB (b, e) = goV b ++ go e
goA (_,pats, e) = concatMap goV pats ++ go e
goT (TyVarTy _) = []
goT (AppTy t1 t2) = goT t1 ++ goT t2
goT (TyConApp tc ts) = [tc | not (ignore tc)] ++ concatMap goT ts
-- ↑ This is the crucial bit
goT (ForAllTy _ t) = goT t
#if MIN_VERSION_GLASGOW_HASKELL(8,2,0,0)
goT (FunTy
#if MIN_VERSION_GLASGOW_HASKELL(9,0,0,0)
_
#endif
# if MIN_VERSION_GLASGOW_HASKELL(8,9,0,0)
_
# endif
t1 t2) = goT t1 ++ goT t2
#endif
goT (LitTy _) = []
goT (CastTy t _) = goT t
goT (CoercionTy _) = []
--
-- | Returns @True@ if the given core expression mentions no term variable
-- anywhere that has the given name.
freeOfTerm :: Slice -> [Name] -> Maybe (Var, CoreExpr)
freeOfTerm slice needles = listToMaybe [ (v,e) | (v,e) <- slice, not (go e) ]
where
isNeedle n = n `elem` needles
goV v | isNeedle (Var.varName v) = False
| Just dc <- isDataConId_maybe v
, isNeedle (dataConName dc) = False
| otherwise = True
go (Var v) = goV v
go (Lit _ ) = True
go (App e a) = go e && go a
go (Lam _ e) = go e
go (Let bind body) = all goB (flattenBinds [bind]) && go body
go (Case s _ _ alts) = go s && all goA alts
go (Cast e _) = go e
go (Tick _ e) = go e
go (Type _) = True
go (Coercion _) = True
goB (_, e) = go e
goA (ac, _, e) = goAltCon ac && go e
goAltCon (DataAlt dc) | isNeedle (dataConName dc) = False
goAltCon _ = True
-- | True if the given variable binding does not allocate, if called fully
-- satisfied.
--
-- It currently does not look through function calls, which of course could
-- allocate. It should probably at least look through local function calls.
--
-- The variable is important to know the arity of the function.
doesNotAllocate :: Slice -> Maybe (Var, CoreExpr)
doesNotAllocate slice = listToMaybe [ (v,e) | (v,e) <- slice, not (go (idArity v) e) ]
where
go _ (Var v)
| isDataConWorkId v, idArity v > 0 = False
go a (Var v) = a >= idArity v
go _ (Lit _ ) = True
go a (App e arg) | isTypeArg arg = go a e
go a (App e arg) = go (a+1) e && goArg arg
go a (Lam b e) | isTyVar b = go a e
go 0 (Lam _ _) = False
go a (Lam _ e) = go (a-1) e
go a (Let bind body) = all goB (flattenBinds [bind]) && go a body
go a (Case s _ _ alts) = go 0 s && all (goA a) alts
go a (Cast e _) = go a e
go a (Tick _ e) = go a e
go _ (Type _) = True
go _ (Coercion _) = True
goArg e | exprIsTrivial e = go 0 e
| isUnliftedType (exprType e) = go 0 e
| otherwise = False
goB (b, e)
#if MIN_VERSION_GLASGOW_HASKELL(8,2,0,0)
| isJoinId b = go (idArity b) e
#endif
-- Not sure when a local function definition allocates…
| isFunTy (idType b) = go (idArity b) e
| isUnliftedType (idType b) = go (idArity b) e
| otherwise = False
-- A let binding allocates if any variable is not a join point and not
-- unlifted
goA a (_,_, e) = go a e
doesNotContainTypeClasses :: Slice -> [Name] -> Maybe (Var, CoreExpr, [TyCon])
doesNotContainTypeClasses slice tcNs
= allTyCons (\tc -> not (isClassTyCon tc) || any (getName tc ==) tcNs) slice