Simon Peyton Jones pushed to branch wip/T26681 at Glasgow Haskell Compiler / GHC Commits: 824fe52d by Simon Peyton Jones at 2026-01-06T15:34:59+00:00 Add missing InVar->OutVar lookup in SetLevels As #26681 showed, the SetLevels pass was failing to map an InVar to an OutVar. Very silly! I'm amazed it hasn't broken before now. I have improved the type singatures (to mention InVar and OutVar) so it's more obvious what needs to happen. - - - - - 3 changed files: - compiler/GHC/Core/Opt/SetLevels.hs - + testsuite/tests/simplCore/should_compile/T26681.hs - testsuite/tests/simplCore/should_compile/all.T Changes: ===================================== compiler/GHC/Core/Opt/SetLevels.hs ===================================== @@ -91,6 +91,7 @@ import GHC.Core.Utils import GHC.Core.Opt.Arity ( exprBotStrictness_maybe, isOneShotBndr ) import GHC.Core.FVs -- all of it import GHC.Core.Subst +import GHC.Core.TyCo.Subst( lookupTyVar ) import GHC.Core.Make ( sortQuantVars ) import GHC.Core.Type ( Type, tyCoVarsOfType , mightBeUnliftedType, closeOverKindsDSet @@ -466,8 +467,8 @@ lvlCase env scrut_fvs scrut' case_bndr ty alts ty' = substTyUnchecked (le_subst env) ty incd_lvl = incMinorLvl (le_ctxt_lvl env) - dest_lvl = maxFvLevel (const True) env scrut_fvs - -- Don't abstract over type variables, hence const True + dest_lvl = maxFvLevel includeTyVars env scrut_fvs + -- Don't abstract over type variables, hence includeTyVars lvl_alt alts_env (AnnAlt con bs rhs) = do { rhs' <- lvlMFE new_env True rhs @@ -719,8 +720,11 @@ hasFreeJoin :: LevelEnv -> DVarSet -> Bool -- (In the latter case it won't be a join point any more.) -- Not treating top-level ones specially had a massive effect -- on nofib/minimax/Prog.prog -hasFreeJoin env fvs - = not (maxFvLevel isJoinId env fvs == tOP_LEVEL) +hasFreeJoin env fvs = anyDVarSet bad_join fvs + where + bad_join v = isJoinId v && + maxIn True env v tOP_LEVEL /= tOP_LEVEL + {- Note [Saving work] ~~~~~~~~~~~~~~~~~~~~~ @@ -1607,10 +1611,10 @@ destLevel env fvs fvs_ty is_function is_bot | otherwise = max_fv_id_level where - max_fv_id_level = maxFvLevel isId env fvs -- Max over Ids only; the - -- tyvars will be abstracted + max_fv_id_level = maxFvLevel idsOnly env fvs -- Max over Ids only; the + -- tyvars will be abstracted - as_far_as_poss = maxFvLevel' isId env fvs_ty + as_far_as_poss = maxFvLevel' idsOnly env fvs_ty -- See Note [Floating and kind casts] {- Note [Floating and kind casts] @@ -1768,28 +1772,47 @@ extendCaseBndrEnv le@(LE { le_subst = subst, le_env = id_env }) , le_env = add_id id_env (case_bndr, scrut_var) } extendCaseBndrEnv env _ _ = env -maxFvLevel :: (Var -> Bool) -> LevelEnv -> DVarSet -> Level -maxFvLevel max_me env var_set - = nonDetStrictFoldDVarSet (maxIn max_me env) tOP_LEVEL var_set +includeTyVars, idsOnly :: Bool +idsOnly = False +includeTyVars = True + +maxFvLevel :: Bool -> LevelEnv -> DVarSet -> Level +maxFvLevel include_tyvars env var_set + = nonDetStrictFoldDVarSet (maxIn include_tyvars env) tOP_LEVEL var_set -- It's OK to use a non-deterministic fold here because maxIn commutes. -maxFvLevel' :: (Var -> Bool) -> LevelEnv -> TyCoVarSet -> Level +maxFvLevel' :: Bool -> LevelEnv -> TyCoVarSet -> Level -- Same but for TyCoVarSet -maxFvLevel' max_me env var_set - = nonDetStrictFoldUniqSet (maxIn max_me env) tOP_LEVEL var_set +maxFvLevel' include_tyvars env var_set + = nonDetStrictFoldUniqSet (maxIn include_tyvars env) tOP_LEVEL var_set -- It's OK to use a non-deterministic fold here because maxIn commutes. -maxIn :: (Var -> Bool) -> LevelEnv -> InVar -> Level -> Level -maxIn max_me (LE { le_lvl_env = lvl_env, le_env = id_env }) in_var lvl +maxIn :: Bool -> LevelEnv -> InVar -> Level -> Level +-- True <=> include tyvars +maxIn include_tyvars env@(LE { le_subst = subst, le_env = id_env }) in_var lvl + | isId in_var = case lookupVarEnv id_env in_var of + Nothing -> maxOut env in_var lvl Just (abs_vars, _) -> foldr max_out lvl abs_vars - Nothing -> max_out in_var lvl - where - max_out out_var lvl - | max_me out_var = case lookupVarEnv lvl_env out_var of - Just lvl' -> maxLvl lvl' lvl - Nothing -> lvl - | otherwise = lvl -- Ignore some vars depending on max_me + where + max_out out_var lvl + | isTyVar out_var && not include_tyvars + = lvl + | otherwise = maxOut env out_var lvl + + | include_tyvars -- TyVars + = case lookupTyVar subst in_var of + Just ty -> nonDetStrictFoldVarSet (maxOut env) lvl (tyCoVarsOfType ty) + Nothing -> maxOut env in_var lvl + + | otherwise -- Ignore free tyvars + = lvl + +maxOut :: LevelEnv -> OutVar -> Level -> Level +maxOut (LE { le_lvl_env = lvl_env }) out_var lvl + = case lookupVarEnv lvl_env out_var of + Just lvl' -> maxLvl lvl' lvl + Nothing -> lvl lookupVar :: LevelEnv -> Id -> LevelledExpr lookupVar le v = case lookupVarEnv (le_env le) v of ===================================== testsuite/tests/simplCore/should_compile/T26681.hs ===================================== @@ -0,0 +1,47 @@ +{-# LANGUAGE BangPatterns #-} +{-# LANGUAGE DataKinds #-} +{-# LANGUAGE GADTs #-} +{-# LANGUAGE PolyKinds #-} +{-# LANGUAGE ScopedTypeVariables #-} +{-# LANGUAGE StandaloneKindSignatures #-} +{-# LANGUAGE TypeApplications #-} +{-# LANGUAGE TypeFamilies #-} +{-# LANGUAGE TypeOperators #-} + +module T26681 where + +import Data.Kind (Type) +import Data.Type.Equality +import GHC.TypeLits +import qualified Unsafe.Coerce + + +{-# NOINLINE unsafeCoerceRefl #-} +unsafeCoerceRefl :: a :~: b +unsafeCoerceRefl = Unsafe.Coerce.unsafeCoerce Refl + +type family MapJust l where + MapJust '[] = '[] + MapJust (x : xs) = Just x : MapJust xs + +type family Tail l where + Tail (_ : xs) = xs + +lemMapJustCons :: MapJust sh :~: Just n : sh' -> sh :~: n : Tail sh +lemMapJustCons Refl = unsafeCoerceRefl + + +type ListX :: [Maybe Nat] -> (Maybe Nat -> Type) -> Type +data ListX sh f where + ConsX :: !(f n) -> ListX (n : sh) f + + +data JustN n where + JustN :: JustN (Just n) + +data UnconsListSRes f sh1 = forall n sh. (n : sh ~ sh1) => UnconsListSRes + +listsUncons :: forall sh1 f. ListX (MapJust sh1) JustN -> UnconsListSRes f sh1 +listsUncons (ConsX JustN) + | Refl <- lemMapJustCons @sh1 Refl + = UnconsListSRes ===================================== testsuite/tests/simplCore/should_compile/all.T ===================================== @@ -563,3 +563,4 @@ test('T26115', [grep_errmsg(r'DFun')], compile, ['-O -ddump-simpl -dsuppress-uni test('T26116', normal, compile, ['-O -ddump-rules']) test('T26117', [grep_errmsg(r'==')], compile, ['-O -ddump-simpl -dsuppress-uniques']) test('T26349', normal, compile, ['-O -ddump-rules']) +test('T26681', normal, compile, ['-O']) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/824fe52dea5322a3d76251895ca02f66... -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/824fe52dea5322a3d76251895ca02f66... You're receiving this email because of your account on gitlab.haskell.org.