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[Git][ghc/ghc][wip/T27261] Trim the continuation in mkDupableContWithDmds
by sheaf (＠sheaf) 25 May '26

25 May '26

sheaf pushed to branch wip/T27261 at Glasgow Haskell Compiler / GHC Commits: 56d6e3bb by Simon Peyton Jones at 2026-05-25T11:33:08+02:00 Trim the continuation in mkDupableContWithDmds When there are no remaining argument demands, it means the application is bottoming. In this case, we can trim the continuation to avoid the panic that was observed in #27261. See Note [Trimming the continuation for bottoming functions] in GHC.Core.Opt.Simplify.Iteration. - - - - - 5 changed files: - compiler/GHC/Core/Opt/Simplify/Iteration.hs - compiler/GHC/Core/Opt/Simplify/Utils.hs - + testsuite/tests/simplCore/should_compile/T27261.hs - + testsuite/tests/simplCore/should_compile/T27261_aux.hs - testsuite/tests/simplCore/should_compile/all.T Changes: ===================================== compiler/GHC/Core/Opt/Simplify/Iteration.hs ===================================== @@ -62,6 +62,7 @@ import GHC.Types.Var ( isTyCoVar ) import GHC.Builtin.Types.Prim( realWorldStatePrimTy ) import GHC.Builtin.Names( runRWKey, seqHashKey ) +import qualified GHC.Data.List.Infinite as Inf import GHC.Data.Maybe ( isNothing, orElse, mapMaybe ) import GHC.Data.FastString import GHC.Unit.Module ( moduleName ) @@ -2444,24 +2445,9 @@ rebuildCall env arg_info _cont ---------- Bottoming applications -------------- rebuildCall env (ArgInfo { ai_fun = fun, ai_args = rev_args, ai_dmds = [] }) cont - -- When we run out of strictness args, it means - -- that the call is definitely bottom; see GHC.Core.Opt.Simplify.Utils.mkArgInfo - -- Then we want to discard the entire strict continuation. E.g. - -- * case (error "hello") of { ... } - -- * (error "Hello") arg - -- * f (error "Hello") where f is strict - -- etc - -- Then, especially in the first of these cases, we'd like to discard - -- the continuation, leaving just the bottoming expression. But the - -- type might not be right, so we may have to add a coerce. - | not (contIsTrivial cont) -- Only do this if there is a non-trivial - -- continuation to discard, else we do it - -- again and again! - = seqType cont_ty `seq` -- See Note [Avoiding space leaks in OutType] - return (emptyFloats env, castBottomExpr res cont_ty) - where - res = argInfoExpr fun rev_args - cont_ty = contResultType cont + -- When we run out of demands, it means that the call is definitely bottom. + -- See (TC2) in Note [Trimming the continuation for bottoming functions] + = rebuild env (argInfoExpr fun rev_args) (mkBottomCont cont) ---------- Simplify type applications -------------- rebuildCall env info (ApplyToTy { sc_arg_ty = arg_ty, sc_hole_ty = hole_ty, sc_cont = cont }) @@ -4045,6 +4031,41 @@ When we have then we can just duplicate those alts because the A and C cases will disappear immediately. This is more direct than creating join points and inlining them away. See #4930. + +Note [Trimming the continuation for bottoming functions] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Suppose + f :: Int -> Int -> Int + f x = error "urk" + + foo = f 3 4 + +f's demand signature say "after one arg I return bottom". We can drop +the remaining arguments, thus + + foo = case f 3 of {} + +This trimming can also be done with other continuations: + * case (error "hello") of { ... } + * f (error "Hello") where f is strict + etc + +We implement the trimming in three parts: + +(TC1) In `mkArgInfo`, for a bottoming function, we make a list of `RemainingArgDmds` + with a finite list of elements (in the example above, just one). + + For comparison, note that, for non-bottoming functions, the `RemainingArgDmds` + always finishes with an infinite list of `topDmd`. + +(TC2) In `rebuildCall`, when we run out of `RemainingArgDmds` we discard the + remaining continuation. + + After discarding the continuation, the types might not match, in which case + we leave behind a (case <hole> of {}) wrapper. See the call to `mkBottomCont`. + +(TC3) In `mkDupableContWithDmds`, we similarly discard the continuation when + we run out of `RemainingArgDmds`. -} -------------------- @@ -4079,10 +4100,10 @@ mkDupableCont env cont = mkDupableContWithDmds (zapSubstEnv env) (repeat topDmd) cont mkDupableContWithDmds - :: SimplEnvIS -> [Demand] -- Demands on arguments; always infinite + :: SimplEnvIS -> RemainingArgDmds -> SimplCont -> SimplM ( SimplFloats, SimplCont) -mkDupableContWithDmds env _ cont +mkDupableContWithDmds env remaining_dmds cont -- Check the invariant | assertPpr (checkSimplEnvIS env) (pprBadSimplEnvIS env) False = pprPanic "mkDupableContWithDmds" empty @@ -4090,6 +4111,13 @@ mkDupableContWithDmds env _ cont | contIsDupable cont = return (emptyFloats env, cont) + -- No more demands => function is definitely bottom + -- => simply trim the continuation + -- c.f. the null-demands case in `rebuildCall` + -- See (TC3) in Note [Trimming the continuation for bottoming functions] + | null remaining_dmds + = return (emptyFloats env, mkBottomCont cont) + mkDupableContWithDmds _ _ (Stop {}) = panic "mkDupableCont" -- Handled by previous eqn mkDupableContWithDmds env dmds (CastIt { sc_co = co, sc_opt = opt, sc_cont = cont }) @@ -4134,7 +4162,8 @@ mkDupableContWithDmds env _ , thumbsUpPlanA cont = -- Use Plan A of Note [Duplicating StrictArg] -- pprTrace "Using plan A" (ppr (ai_fun fun) $$ text "args" <+> ppr (ai_args fun) $$ text "cont" <+> ppr cont) $ - do { let _ :| dmds = expectNonEmpty $ ai_dmds fun + do { let _ :| dmds = expectNonEmpty (ai_dmds fun) -- See Invariant of StrictArg; + -- ai_dmds is never empty ; (floats1, cont') <- mkDupableContWithDmds env dmds cont -- Use the demands from the function to add the right -- demand info on any bindings we make for further args @@ -4180,7 +4209,10 @@ mkDupableContWithDmds env dmds -- let a = ...arg... -- in [...hole...] a -- NB: sc_dup /= OkToDup; that is caught earlier by contIsDupable - do { let dmd:|cont_dmds = expectNonEmpty dmds + do { let dmd:|cont_dmds = + -- We took care to handle an empty demand list at the start, + -- ensuring this call to 'expectNonEmpty' does not panic (#27261). + expectNonEmpty dmds ; (floats1, cont') <- mkDupableContWithDmds env cont_dmds cont ; let env' = env `setInScopeFromF` floats1 ; arg' <- simplArg env' Nothing hole_ty se arg arg_mco @@ -4251,7 +4283,7 @@ mkDupableStrictBind env arg_bndr join_rhs res_ty ; let arg_info = ArgInfo { ai_fun = join_bndr , ai_rules = [], ai_args = [] , ai_encl = False, ai_dmds = repeat topDmd - , ai_discs = repeat 0 } + , ai_discs = Inf.repeat 0 } ; return ( addJoinFloats (emptyFloats env) $ unitJoinFloat $ NonRec join_bndr $ ===================================== compiler/GHC/Core/Opt/Simplify/Utils.hs ===================================== @@ -25,13 +25,13 @@ module GHC.Core.Opt.Simplify.Utils ( StaticEnv(..), isSimplified, contIsStop, contIsDupable, contResultType, contHoleType, contHoleScaling, - contIsTrivial, contArgs, contIsRhs, + contIsTrivial, contArgs, contIsRhs, mkBottomCont, hasArgs, countArgs, contOutArgs, dropContArgs, mkBoringStop, mkRhsStop, mkLazyArgStop, interestingCallContext, -- ArgInfo - ArgInfo(..), ArgSpec(..), mkArgInfo, + ArgInfo(..), ArgSpec(..), RemainingArgDmds, mkArgInfo, addValArgTo, addTyArgTo, argInfoExpr, argSpecArg, pushOutArgs, pushArgSpecs, @@ -54,8 +54,10 @@ import GHC.Core.Opt.Stats ( Tick(..) ) import qualified GHC.Core.Subst import GHC.Core.Ppr import GHC.Core.TyCo.Ppr ( pprParendType ) +import GHC.Core.TyCo.Compare ( eqTypeIgnoringMultiplicity ) import GHC.Core.FVs import GHC.Core.Utils +import GHC.Core.Make( mkWildValBinder ) import GHC.Core.Opt.Arity import GHC.Core.Unfold import GHC.Core.Unfold.Make @@ -75,6 +77,8 @@ import GHC.Types.Var.Set import GHC.Types.Basic import GHC.Types.Name.Env +import GHC.Data.List.Infinite ( Infinite(..) ) +import qualified GHC.Data.List.Infinite as Inf import GHC.Data.OrdList ( isNilOL ) import GHC.Data.FastString ( fsLit ) @@ -205,10 +209,10 @@ data SimplCont | StrictArg -- (StrictArg (f e1 ..en) K)[e] = K[ f e1 .. en e ] { sc_dup :: DupFlag - , sc_fun :: ArgInfo -- Specifies f, e1..en, Whether f has rules, etc + , sc_fun :: ArgInfo -- Specifies f, e1..en, whether f has rules, etc -- plus demands and discount flags for *this* arg -- and further args - -- So ai_dmds and ai_discs are never empty + -- Invariant: ai_dmds and ai_discs are never empty , sc_fun_ty :: OutType -- Type of the function (f e1 .. en), -- presumably (arg_ty -> res_ty) -- where res_ty is expected by sc_cont @@ -348,32 +352,41 @@ doesn't matter because we'll never compute them all. data ArgInfo = ArgInfo { - ai_fun :: OutId, -- The function - ai_args :: [ArgSpec], -- ...applied to these args (which are in *reverse* order) + ai_fun :: OutId, -- ^ The function + ai_args :: [ArgSpec], -- ^ ...applied to these args (which are in *reverse* order) -- NB: all these argumennts are already simplified - ai_rules :: [CoreRule], -- Rules for this function - ai_encl :: Bool, -- Flag saying whether this function - -- or an enclosing one has rules (recursively) - -- True => be keener to inline in all args + ai_rules :: [CoreRule], -- ^ Rules for this function + ai_encl :: Bool, + -- ^ Flag saying whether this function or an enclosing one has rules + -- (recursively) + -- + -- @True@ means: be keener to inline in all args - ai_dmds :: [Demand], -- Demands on remaining value arguments (beyond ai_args) - -- Usually infinite, but if it is finite it guarantees - -- that the function diverges after being given - -- that number of args + ai_dmds :: RemainingArgDmds, + -- ^ Demands on remaining value arguments (beyond 'ai_args') - ai_discs :: [Int] -- Discounts for remaining value arguments (beyond ai_args) - -- non-zero => be keener to inline - -- Always infinite + ai_discs :: Infinite Int + -- ^ Discounts for remaining value arguments (beyond 'ai_args') + -- + -- A non-zero value means: be keener to inline } -data ArgSpec - = ValArg { as_dmd :: Demand -- Demand placed on this argument - , as_arg :: OutExpr -- Apply to this (coercion or value); c.f. ApplyToVal - , as_hole_ty :: OutType } -- Type of the function (presumably t1 -> t2) +-- | 'RemainingArgDmds' gives the demands on any remaining value arguments. +-- +-- It is usually infinite (with 'topDmd's in the tail), but if it is finite it +-- guarantees that the function diverges after being applied to that number +-- of arguments. +type RemainingArgDmds = [Demand] - | TyArg { as_arg_ty :: OutType -- Apply to this type; c.f. ApplyToTy - , as_hole_ty :: OutType } -- Type of the function (presumably forall a. blah) +data ArgSpec + -- | A value argument + = ValArg { as_dmd :: Demand -- ^ Demand placed on this argument + , as_arg :: OutExpr -- ^ Apply to this (coercion or value); c.f. 'ApplyToVal' + , as_hole_ty :: OutType } -- ^ Type of the function (presumably @t1 -> t2@ for 'ValArg' or @forall a. blah@ for 'TyArg') + -- | A type argument + | TyArg { as_arg_ty :: OutType -- ^ Apply to this type; c.f. 'ApplyToTy' + , as_hole_ty :: OutType } -- ^ Type of the function (presumably @t1 -> t2@ for 'ValArg' or @forall a. blah@ for 'TyArg') instance Outputable ArgInfo where ppr (ArgInfo { ai_fun = fun, ai_args = args, ai_dmds = dmds, ai_rules = rules }) @@ -389,7 +402,7 @@ instance Outputable ArgSpec where addValArgTo :: ArgInfo -> OutExpr -> OutType -> ArgInfo addValArgTo ai arg hole_ty - | ArgInfo { ai_dmds = dmd:dmds, ai_discs = _:discs } <- ai + | ArgInfo { ai_dmds = dmd:dmds, ai_discs = Inf _ discs } <- ai -- Pop the top demand and and discounts off , let arg_spec = ValArg { as_arg = arg, as_hole_ty = hole_ty, as_dmd = dmd } = ai { ai_args = arg_spec : ai_args ai @@ -492,12 +505,23 @@ contIsDupable (TickIt _ k) = contIsDupable k contIsTrivial :: SimplCont -> Bool contIsTrivial (Stop {}) = True contIsTrivial (ApplyToTy { sc_cont = k }) = contIsTrivial k --- This one doesn't look right. A value application is not trivial --- contIsTrivial (ApplyToVal { sc_arg = Coercion _, sc_cont = k }) = contIsTrivial k contIsTrivial (CastIt { sc_cont = k }) = contIsTrivial k contIsTrivial _ = False ------------------- +contStop :: SimplCont -> SimplCont +-- ^ Get the 'Stop' at the tail of the continuation +-- +-- Always returns a continuation of form @(Stop ...)@. +contStop stop@(Stop {}) = stop +contStop (CastIt { sc_cont = k }) = contStop k +contStop (StrictBind { sc_cont = k }) = contStop k +contStop (StrictArg { sc_cont = k }) = contStop k +contStop (Select { sc_cont = k }) = contStop k +contStop (ApplyToTy { sc_cont = k }) = contStop k +contStop (ApplyToVal { sc_cont = k }) = contStop k +contStop (TickIt _ k) = contStop k + contResultType :: SimplCont -> OutType contResultType (Stop ty _ _) = ty contResultType (CastIt { sc_cont = k }) = contResultType k @@ -651,6 +675,35 @@ contEvalContext bndrs cont = go cont -- Perhaps reconstruct the demand on the scrutinee by looking at field -- and case binder dmds, see addCaseBndrDmd. No priority right now. +------------------- +mkBottomCont ::SimplCont -> SimplCont +-- ^ Given a continuation `cont`, return a `cont` /of the same type/, +-- looking like @(case \<hole\> of {})@. +-- +-- This is used when we are going to fill in the @<hole>@ with bottom. +-- See (TC2,3) in Note [Trimming the continuation for bottoming functions] +-- +-- Don't bother to trim, making a @case <hole> of {}@, if we have only +-- an essentially-trivial continuation; e.g. @(<hole> \@ty |> co)@. +mkBottomCont cont = go cont + where + go k@(Stop {}) = k + go (TickIt t k') = TickIt t (go k') + go k@(CastIt { sc_cont = k' }) = k { sc_cont = go k' } + go k@(ApplyToTy { sc_cont = k' }) = k { sc_cont = go k' } + go k@(Select { sc_alts = [], sc_cont = Stop {} }) = k -- Optimisation only + go k | Stop res_ty _ _ <- stop_cont + , hole_ty `eqTypeIgnoringMultiplicity` res_ty + = stop_cont + | otherwise + = Select { sc_alts = [] + , sc_bndr = mkWildValBinder OneTy hole_ty + , sc_env = Simplified OkDup + , sc_cont = stop_cont } + where + hole_ty = contHoleType k + stop_cont = contStop k + ------------------- mkArgInfo :: SimplEnv -> Id -> [CoreRule] -> SimplCont -> ArgInfo mkArgInfo env fun rules_for_fun cont @@ -672,16 +725,17 @@ mkArgInfo env fun rules_for_fun cont fun_has_rules = not (null rules_for_fun) - vanilla_discounts, arg_discounts :: [Int] - vanilla_discounts = repeat 0 + vanilla_discounts, arg_discounts :: Infinite Int + vanilla_discounts = Inf.repeat 0 arg_discounts = case idUnfolding fun of CoreUnfolding {uf_guidance = UnfIfGoodArgs {ug_args = discounts}} - -> discounts ++ vanilla_discounts + -> discounts Inf.++ vanilla_discounts _ -> vanilla_discounts - vanilla_dmds, arg_dmds :: [Demand] + vanilla_dmds :: RemainingArgDmds vanilla_dmds = repeat topDmd + arg_dmds :: RemainingArgDmds arg_dmds | not (seInline env) = vanilla_dmds -- See Note [Do not expose strictness if sm_inline=False] @@ -689,26 +743,22 @@ mkArgInfo env fun rules_for_fun cont = -- add_type_str fun_ty $ case splitDmdSig (idDmdSig fun) of (demands, result_info) - | not (demands `lengthExceeds` n_val_args) - -> -- Enough args, use the strictness given. - -- For bottoming functions we used to pretend that the arg - -- is lazy, so that we don't treat the arg as an - -- interesting context. This avoids substituting - -- top-level bindings for (say) strings into - -- calls to error. But now we are more careful about - -- inlining lone variables, so its ok - -- (see GHC.Core.Op.Simplify.Utils.analyseCont) - if isDeadEndDiv result_info then - demands -- Finite => result is bottom - else - demands ++ vanilla_dmds + | not (demands `lengthExceeds` n_val_args) + -> remaining_dmds -- Enough args, use the strictness given. | otherwise -> warnPprTrace True "More demands than arity" (ppr fun <+> ppr (idArity fun) <+> ppr n_val_args <+> ppr demands) $ vanilla_dmds -- Not enough args, or no strictness - add_type_strictness :: Type -> [Demand] -> [Demand] - -- If the function arg types are strict, record that in the 'strictness bits' + where + remaining_dmds :: RemainingArgDmds + -- isDeadEndDiv: if remaining_dmds is finite, result is bottom + -- See (TC1) in Note [Trimming the continuation for bottoming functions] + remaining_dmds | isDeadEndDiv result_info = demands + | otherwise = demands ++ vanilla_dmds + + add_type_strictness :: Type -> RemainingArgDmds -> RemainingArgDmds + -- If the function arg /types/ are strict, record that in the RemainingArgDmds -- No need to instantiate because unboxed types (which dominate the strict -- types) can't instantiate type variables. -- add_type_strictness is done repeatedly (for each call); @@ -915,16 +965,16 @@ the incentive to disappear when we inline `f`! lazyArgContext :: ArgInfo -> CallCtxt -- Use this for lazy arguments lazyArgContext (ArgInfo { ai_encl = encl_rules, ai_discs = discs }) - | encl_rules = RuleArgCtxt - | disc:_ <- discs, disc > 0 = DiscArgCtxt -- Be keener here - | otherwise = BoringCtxt -- Nothing interesting + | encl_rules = RuleArgCtxt + | Inf disc _ <- discs, disc > 0 = DiscArgCtxt -- Be keener here + | otherwise = BoringCtxt -- Nothing interesting strictArgContext :: ArgInfo -> CallCtxt strictArgContext (ArgInfo { ai_encl = encl_rules, ai_discs = discs }) -- Use this for strict arguments - | encl_rules = RuleArgCtxt - | disc:_ <- discs, disc > 0 = DiscArgCtxt -- Be keener here - | otherwise = RhsCtxt NonRecursive + | encl_rules = RuleArgCtxt + | Inf disc _ <- discs, disc > 0 = DiscArgCtxt -- Be keener here + | otherwise = RhsCtxt NonRecursive -- Why RhsCtxt? if we see f (g x), and f is strict, we -- want to be a bit more eager to inline g, because it may -- expose an eval (on x perhaps) that can be eliminated or ===================================== testsuite/tests/simplCore/should_compile/T27261.hs ===================================== @@ -0,0 +1,17 @@ +{-# OPTIONS_GHC -fno-full-laziness #-} + +module T27261 (foo) where + +import T27261_aux (myError) + +foo :: [String] -> (() -> Int) -> Int +foo cs = + \ k -> ( case bar of + Just str -> let cs2 = case cs of { [] -> cs; _ -> "stack entry" : cs } + in myError cs2 str + Nothing -> \ c -> c () ) + ( \ _ -> k () ) + +bar :: Maybe String +bar = Nothing +{-# NOINLINE bar #-} ===================================== testsuite/tests/simplCore/should_compile/T27261_aux.hs ===================================== @@ -0,0 +1,7 @@ +{-# LANGUAGE BangPatterns #-} + +module T27261_aux (myError) where + +myError :: [String] -> String -> a +myError !_ _ = undefined +{-# NOINLINE myError #-} ===================================== testsuite/tests/simplCore/should_compile/all.T ===================================== @@ -601,3 +601,4 @@ test('T25718a', normal, compile, ['-O -ddump-simpl -dsuppress-uniques -dsuppress test('T25718b', normal, compile, ['-O -ddump-simpl -dsuppress-uniques -dsuppress-all -dno-typeable-binds']) test('T25718c', normal, compile, ['-O -ddump-simpl -dsuppress-uniques -dsuppress-all -dno-typeable-binds']) test('T19166', normal, compile, ['-O -ddump-simpl -dsuppress-uniques -dsuppress-all -dno-typeable-binds']) +test('T27261', [extra_files(['T27261_aux.hs'])], multimod_compile, ['T27261', '-v0 -O']) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/56d6e3bb1d438b880c2d1a255f82dd6… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/56d6e3bb1d438b880c2d1a255f82dd6… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/sjakobi/set-ops] Ensure that SetOps.{minusList,unionListsOrd} can be specialized
by Simon Jakobi (＠sjakobi2) 25 May '26

25 May '26

Simon Jakobi pushed to branch wip/sjakobi/set-ops at Glasgow Haskell Compiler / GHC Commits: 092fcbbe by Simon Jakobi at 2026-05-25T09:06:36+02:00 Ensure that SetOps.{minusList,unionListsOrd} can be specialized ...by marking them INLINABLE. Haddock allocates 0.1–0.3% less as a result. This also removes some redundant constraints on unionListsOrd. - - - - - 1 changed file: - compiler/GHC/Data/List/SetOps.hs Changes: ===================================== compiler/GHC/Data/List/SetOps.hs ===================================== @@ -60,12 +60,13 @@ getNth xs n = assertPpr (xs `lengthExceeds` n) (ppr n $$ ppr xs) $ -- -- Uses a set internally to record duplicates. This makes it slightly slower for -- very small lists but avoids quadratic behaviour for large lists. -unionListsOrd :: (HasDebugCallStack, Outputable a, Ord a) => [a] -> [a] -> [a] +unionListsOrd :: Ord a => [a] -> [a] -> [a] unionListsOrd xs ys - -- Since both arguments don't have internal duplicates we can just take all of xs - -- and every element of ys that's not already in xs. + -- Since both arguments don't have internal duplicates we can just take all of ys + -- and every element of xs that's not already in ys. = let set_ys = S.fromList ys in (filter (\e -> not $ S.member e set_ys) xs) ++ ys +{-# INLINABLE unionListsOrd #-} -- Ensure the function can be specialized. -- | Assumes that the arguments contain no duplicates unionLists :: (HasDebugCallStack, Outputable a, Eq a) => [a] -> [a] -> [a] @@ -108,6 +109,7 @@ minusList xs [y] = filter (/= y) xs minusList xs ys = filter (`S.notMember` yss) xs where yss = S.fromList ys +{-# INLINABLE minusList #-} -- Ensure the function can be specialized. {- ************************************************************************ View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/092fcbbe8965e7f89b75a5e78469596… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/092fcbbe8965e7f89b75a5e78469596… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/semaphore-v2] 8 commits: Use "grimily" instead of "grimly"
by Zubin (＠wz1000) 25 May '26

25 May '26

Zubin pushed to branch wip/semaphore-v2 at Glasgow Haskell Compiler / GHC Commits: 6f9d7c71 by Markus Läll at 2026-05-21T15:25:34-04:00 Use "grimily" instead of "grimly" Fixes https://gitlab.haskell.org/ghc/ghc/-/issues/27221 - - - - - 50e999ca by fendor at 2026-05-21T15:26:18-04:00 Speed up 'closure' computation in `ghc-pkg` Cache the set of already seen `UnitId`s and use `Set` operations to speed up 'closure' computation. Further simplify the implementation of 'closure' to account for the actual usage. As a consequence, we rename 'closure' to 'brokenPackages' to reflect its purpose better after the simplification. - - - - - 7ecc6184 by sheaf at 2026-05-21T15:27:10-04:00 TcMPluginHandling: be more lenient when no plugins This change ensures that, if a function such as 'typecheckModule' was invoked with 'NoTcMPlugins', GHC doesn't spuriously complain about TcM plugins having already been stopped, as there were none to start with. - - - - - 72c8de5c by Simon Jakobi at 2026-05-23T18:41:42-04:00 Implement List.elem via foldr ...in order to allow specialization to Eq instances. The implementation of notElem is updated for consistency.` Corresponding CLC proposal: https://github.com/haskell/core-libraries-committee/issues/412 Addresses #27096. - - - - - 3268c610 by Alan Zimmerman at 2026-05-23T18:42:30-04:00 EPA: Fix span for qualified multiline string Fix the span for a qualified multiline string like Text.""" I'm a multiline Text value ! """ to extend to the end of the entire string, not just the first line. Closes #27274 - - - - - 1f096790 by Alan Zimmerman at 2026-05-23T18:43:20-04:00 EPA: Fix exact printing namespace-specified wildcards Ensures correct printing of imports of the form import Data.Bool (data True(data ..)) import Data.Bool (data True(type ..)) Closes #27291 - - - - - 56ada7c0 by Mrjtjmn at 2026-05-23T18:44:19-04:00 Fix ambiguous syntax of BangPatterns in users guide Update documentation for the BangPatterns extension to specify how surrounding whitespace affects interpretation of `!`. * Only when there is whitespace before `!` and no whitespace after, it is recognized as a BangPattern. * Other cases `⟨varid⟩!⟨varid⟩`, `⟨varid⟩ ! ⟨varid⟩`, `⟨varid⟩! ⟨varid⟩` are treated as infix operators. - - - - - 56cdb867 by Zubin Duggal at 2026-05-25T12:35:45+05:30 Update to semaphore-compat 2.0.0 using v2 of the protocol On Linux and other POSIX platforms, GHC's -jsem jobserver client now speaks v2 of the semaphore-compat protocol, which uses Unix domain sockets in place of POSIX named semaphores. This avoids the libc-ABI issues that affected the old implementation. Windows is unaffected and continues to use the v1 protocol (Win32 named semaphores); its reported protocol version remains v1. When GHC receives a -jsem name whose protocol version it does not support, it emits a -Wsemaphore-version-mismatch warning and falls back to -j<N> rather than crashing. ghc --info exposes the supported version in a new "Semaphore version" entry so cabal-install can detect a mismatch before invoking GHC. Users on a cabal-install that predates the v2 update will continue to build successfully on Linux/POSIX, but will lose the cross-process -jsem coordination and fall back to -j<N> per GHC invocation. Users must upgrade to a cabal-install that supports protocol v2 to recover full parallelism. Also fix a leak in cleanupSem (#27253): cleanupSem used to snapshot heldTokens and release them before killing the loop, while the loop's in-flight acquire/release children could still be mutating it. Cleanup now runs inside the loop's own exit handler, after draining the active child via a new activeChild TVar, so the snapshot has no concurrent mutator. See also: - GHC proposal amendment: https://github.com/ghc-proposals/ghc-proposals/pull/673 - cabal-install patch: https://github.com/haskell/cabal/pull/11628 - semaphore-compat MR: https://gitlab.haskell.org/ghc/semaphore-compat/-/merge_requests/8 Bump semaphore-compat submodule to 2.0.0 Fixes #25087 and #27253 - - - - - 43 changed files: - + changelog.d/elem-via-foldr-27096 - + changelog.d/ghc-pkg-faster-closure - + changelog.d/jobserver-leak-fix - + changelog.d/semaphore-v2 - compiler/GHC/CmmToLlvm/Base.hs - compiler/GHC/Core/Opt/Monad.hs - compiler/GHC/Driver/Errors/Ppr.hs - compiler/GHC/Driver/Errors/Types.hs - compiler/GHC/Driver/Flags.hs - compiler/GHC/Driver/MakeAction.hs - compiler/GHC/Driver/MakeSem.hs - compiler/GHC/Driver/Session.hs - compiler/GHC/HsToCore/Foreign/JavaScript.hs - compiler/GHC/Iface/Binary.hs - compiler/GHC/Parser/Lexer.x - compiler/GHC/Stg/Pipeline.hs - compiler/GHC/StgToJS/Ids.hs - compiler/GHC/Tc/Types.hs - compiler/GHC/Tc/Utils/Monad.hs - compiler/GHC/Types/Error/Codes.hs - compiler/GHC/Types/Hint.hs - compiler/GHC/Types/Hint/Ppr.hs - compiler/GHC/Types/Name/Cache.hs - compiler/GHC/Types/Unique.hs - compiler/GHC/Types/Unique/Supply.hs - docs/users_guide/exts/stolen_syntax.rst - docs/users_guide/using-warnings.rst - docs/users_guide/using.rst - hadrian/src/Flavour.hs - libraries/base/changelog.md - libraries/base/tests/perf/ElemNoFusion_O1.stderr - libraries/base/tests/perf/ElemNoFusion_O2.stderr - libraries/ghc-internal/src/GHC/Internal/List.hs - libraries/semaphore-compat - testsuite/tests/diagnostic-codes/codes.stdout - + testsuite/tests/ghc-api/T27273.hs - testsuite/tests/ghc-api/all.T - testsuite/tests/printer/Makefile - + testsuite/tests/printer/PprQualifiedStrings.hs - + testsuite/tests/printer/Test27291.hs - testsuite/tests/printer/all.T - utils/check-exact/ExactPrint.hs - utils/ghc-pkg/Main.hs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/1170e99240b04e9e4013d31ccea9f8… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/1170e99240b04e9e4013d31ccea9f8… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/wasm-fix-serviceworker] wasm: ensure post-linker output is synchronous ESM
by Cheng Shao (＠TerrorJack) 24 May '26

24 May '26

Cheng Shao pushed to branch wip/wasm-fix-serviceworker at Glasgow Haskell Compiler / GHC Commits: 1f50c9cd by Cheng Shao at 2026-05-24T16:38:15+00:00 wasm: ensure post-linker output is synchronous ESM This patch fixes wasm backend's post-linker output script to ensure it's synchronous ESM and doesn't use top-level await, which doesn't work in ServiceWorkers. Fixes #27257. - - - - - 2 changed files: - + changelog.d/wasm-fix-serviceworker - utils/jsffi/prelude.mjs Changes: ===================================== changelog.d/wasm-fix-serviceworker ===================================== @@ -0,0 +1,4 @@ +section: wasm-backend +synopsis: Ensure post-linker output is synchronous ESM and fix loading in ServiceWorker +issues: #27257 +mrs: !16093 ===================================== utils/jsffi/prelude.mjs ===================================== @@ -39,19 +39,13 @@ export class JSValManager { // To benchmark different setImmediate() implementations in the // browser, use https://github.com/jphpsf/setImmediate-shim-demo as a // starting point. -export const setImmediate = await (async () => { - // node, bun, or other scripts might have set this up in the browser +export const setImmediate = (() => { + // node, deno, bun, or other scripts might have set this up in the + // browser if (globalThis.setImmediate) { return globalThis.setImmediate; } - // deno - if (globalThis.Deno) { - try { - return (await import("node:timers")).setImmediate; - } catch {} - } - // https://developer.mozilla.org/en-US/docs/Web/API/Scheduler/postTask if (globalThis.scheduler) { return (cb, ...args) => scheduler.postTask(() => cb(...args)); View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/1f50c9cd4953ed2956406aef9c0041a… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/1f50c9cd4953ed2956406aef9c0041a… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc] Pushed new branch wip/wasm-fix-serviceworker
by Cheng Shao (＠TerrorJack) 24 May '26

24 May '26

Cheng Shao pushed new branch wip/wasm-fix-serviceworker at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/wasm-fix-serviceworker You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc] Pushed new branch wip/sjakobi/checkTyEqRhs
by Simon Jakobi (＠sjakobi2) 23 May '26

23 May '26

Simon Jakobi pushed new branch wip/sjakobi/checkTyEqRhs at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/sjakobi/checkTyEqRhs You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc] Pushed new branch wip/sjakobi/mkSysLocalOrCoVarM
by Simon Jakobi (＠sjakobi2) 23 May '26

23 May '26

Simon Jakobi pushed new branch wip/sjakobi/mkSysLocalOrCoVarM at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/sjakobi/mkSysLocalOrCoVarM You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][master] Fix ambiguous syntax of BangPatterns in users guide
by Marge Bot (＠marge-bot) 23 May '26

23 May '26

Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC Commits: 56ada7c0 by Mrjtjmn at 2026-05-23T18:44:19-04:00 Fix ambiguous syntax of BangPatterns in users guide Update documentation for the BangPatterns extension to specify how surrounding whitespace affects interpretation of `!`. * Only when there is whitespace before `!` and no whitespace after, it is recognized as a BangPattern. * Other cases `⟨varid⟩!⟨varid⟩`, `⟨varid⟩ ! ⟨varid⟩`, `⟨varid⟩! ⟨varid⟩` are treated as infix operators. - - - - - 1 changed file: - docs/users_guide/exts/stolen_syntax.rst Changes: ===================================== docs/users_guide/exts/stolen_syntax.rst ===================================== @@ -50,7 +50,7 @@ The following syntax is stolen: Stolen by: :extension:`Arrows` -``?varid`` +``?⟨varid⟩`` .. index:: single: implicit parameters @@ -77,17 +77,20 @@ The following syntax is stolen: Stolen by: :extension:`QuasiQuotes` -⟨varid⟩``#``, ⟨char⟩``#``, ⟨string⟩``#``, ⟨integer⟩``#``, ⟨float⟩``#``, ⟨float⟩``##`` +``⟨varid⟩#``, ``⟨char⟩#``, ``⟨string⟩#``, ``⟨integer⟩#``, ``⟨float⟩#``, ``⟨float⟩##`` Stolen by: :extension:`MagicHash` -⟨integer⟩, ``#(Int|Word)(8|16|32|64)?`` +``⟨integer⟩#(Int|Word)(8|16|32|64)?`` Stolen by: :extension:`ExtendedLiterals` ``(#``, ``#)`` Stolen by: :extension:`UnboxedTuples` -⟨varid⟩, ``!``, ⟨varid⟩ - Stolen by: :extension:`BangPatterns` +``⟨varid⟩ !⟨varid⟩`` + Stolen by: :extension:`BangPatterns`. Only when there are whitespaces before + ``!`` and no whitespace after ``!``, it is interpreted as :extension:`BangPatterns`. Other + cases such as ``⟨varid⟩!⟨varid⟩``, ``⟨varid⟩ ! ⟨varid⟩``, and ``⟨varid⟩! ⟨varid⟩``, are + interpreted as infix operators. ``pattern`` Stolen by: :extension:`PatternSynonyms` View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/56ada7c0b3d9ff67fe0fa9999cd9d4e… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/56ada7c0b3d9ff67fe0fa9999cd9d4e… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][master] EPA: Fix exact printing namespace-specified wildcards
by Marge Bot (＠marge-bot) 23 May '26

23 May '26

Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC Commits: 1f096790 by Alan Zimmerman at 2026-05-23T18:43:20-04:00 EPA: Fix exact printing namespace-specified wildcards Ensures correct printing of imports of the form import Data.Bool (data True(data ..)) import Data.Bool (data True(type ..)) Closes #27291 - - - - - 4 changed files: - testsuite/tests/printer/Makefile - + testsuite/tests/printer/Test27291.hs - testsuite/tests/printer/all.T - utils/check-exact/ExactPrint.hs Changes: ===================================== testsuite/tests/printer/Makefile ===================================== @@ -907,6 +907,11 @@ Test25885: $(CHECK_PPR) $(LIBDIR) Test25885.hs $(CHECK_EXACT) $(LIBDIR) Test25885.hs +.PHONY: Test27291 +Test27291: + $(CHECK_PPR) $(LIBDIR) Test27291.hs + $(CHECK_EXACT) $(LIBDIR) Test27291.hs + .PHONY: TestLevelImports TestLevelImports: $(CHECK_PPR) $(LIBDIR) TestLevelImports.hs ===================================== testsuite/tests/printer/Test27291.hs ===================================== @@ -0,0 +1,35 @@ +{-# LANGUAGE ExplicitNamespaces #-} + +module Test27291 + ( C(type ..) -- exports class C and data family D + , C(data ..) -- exports class C and method m + , D(type ..) -- exports data family D + , type T (..) -- exports type T and all its data constructors D, D2 + , type T (type ..) -- exports type T + , type K (type ..) -- exports type K and its constructor K1 + ) where + +import Control.Applicative qualified as A (type Applicative (data ..)) +import Data.Either qualified as E (type Either (data ..)) + +import Data.Bool (data True (..)) +import Data.Bool (data True( data .. ) ) +import Data.Bool (data True( type ..)) + +import DodgyImports03_helper (C( .. )) +import DodgyImports03_helper (C (data .. )) +import DodgyImports03_helper (C( type ..) ) + +import DodgyImports03_helper (T ( .. ) ) +import DodgyImports03_helper (T(data ..)) +import DodgyImports03_helper (T(type ..)) + +import Control.Applicative (type Applicative (type ..)) -- dodgy: no associated types +import Data.Either (type Either (type ..)) -- dodgy: not a class + +import Data.Proxy (type Proxy(data ..)) -- ok +import Data.Proxy (type Proxy(type ..)) -- dodgy: not a class + +import T25901_sub_g_helper qualified as T1 (T (data ..)) -- T and MkT +import T25901_sub_g_helper qualified as T2 (T (type ..)) -- T only +import T25901_sub_g_helper qualified as T3 (type T (..)) -- T and MkT ===================================== testsuite/tests/printer/all.T ===================================== @@ -217,6 +217,7 @@ test('T24237', normal, compile_fail, ['']) test('Test25454', [ignore_stderr, req_ppr_deps], makefile_test, ['Test25454']) test('Test25885', [ignore_stderr, req_ppr_deps], makefile_test, ['Test25885']) +test('Test27291', [ignore_stderr, req_ppr_deps], makefile_test, ['Test27291']) test('TestLevelImports', [ignore_stderr, req_ppr_deps], makefile_test, ['TestLevelImports']) test('TestNamedDefaults', [ignore_stderr, req_ppr_deps], makefile_test, ['TestNamedDefaults']) ===================================== utils/check-exact/ExactPrint.hs ===================================== @@ -4587,9 +4587,9 @@ instance ExactPrint (IE GhcPs) where return (IEThingAbs depr' thing' doc') exact (IEThingAll x ns_spec thing doc) = do depr' <- markAnnotated (ieta_warning x) - ns_spec' <- markAnnotated ns_spec thing' <- markAnnotated thing op' <- markEpToken (ieta_tok_lpar x) + ns_spec' <- markAnnotated ns_spec dd' <- markEpToken (ieta_tok_wc x) cp' <- markEpToken (ieta_tok_rpar x) doc' <- markAnnotated doc View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/1f09679081816acb86fd02eb332f0df… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/1f09679081816acb86fd02eb332f0df… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][master] EPA: Fix span for qualified multiline string
by Marge Bot (＠marge-bot) 23 May '26

23 May '26

Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC Commits: 3268c610 by Alan Zimmerman at 2026-05-23T18:42:30-04:00 EPA: Fix span for qualified multiline string Fix the span for a qualified multiline string like Text.""" I'm a multiline Text value ! """ to extend to the end of the entire string, not just the first line. Closes #27274 - - - - - 5 changed files: - compiler/GHC/Parser/Lexer.x - testsuite/tests/printer/Makefile - + testsuite/tests/printer/PprQualifiedStrings.hs - testsuite/tests/printer/all.T - utils/check-exact/ExactPrint.hs Changes: ===================================== compiler/GHC/Parser/Lexer.x ===================================== @@ -2274,8 +2274,9 @@ tok_quoted_label span buf len _buf2 = do tok_qstrings :: Action -> Action tok_qstrings lex_str span0 buf0 len0 endBuf0 = do let modName = ModuleName $ lexemeToFastString buf0 modNameLen - (src, meta, s) <- unITstring <$> lex_str strSpan strBuf strLen endBuf0 - pure $ L span0 $ ITstring src meta{strMetaQualified = Just modName} s + (span1, src, meta, s) <- unITstring <$> lex_str strSpan strBuf strLen endBuf0 + let span2 = mkPsSpan (psSpanStart span0) (psSpanEnd span1) + pure $ L span2 $ ITstring src meta{strMetaQualified = Just modName} s where -- The buffer/span starting at the string literal (strBuf, strSpanStart) = @@ -2298,7 +2299,7 @@ tok_qstrings lex_str span0 buf0 len0 endBuf0 = do strSpan = mkPsSpan strSpanStart (psSpanEnd span0) unITstring = \case - L _ (ITstring src meta s) -> (src, meta, s) + L span1 (ITstring src meta s) -> (span1, src, meta, s) tok -> panic $ "tok_qstrings got unexpected token: " ++ show tok tok_char :: Action ===================================== testsuite/tests/printer/Makefile ===================================== @@ -922,3 +922,8 @@ TestNamedDefaults: PprModifiers: $(CHECK_PPR) $(LIBDIR) PprModifiers.hs $(CHECK_EXACT) $(LIBDIR) PprModifiers.hs + +.PHONY: PprQualifiedStrings +PprQualifiedStrings: + $(CHECK_PPR) $(LIBDIR) PprQualifiedStrings.hs + $(CHECK_EXACT) $(LIBDIR) PprQualifiedStrings.hs ===================================== testsuite/tests/printer/PprQualifiedStrings.hs ===================================== @@ -0,0 +1,75 @@ +{-# LANGUAGE MultilineStrings #-} +{-# LANGUAGE QualifiedStrings #-} +{-# LANGUAGE TemplateHaskell #-} + +-- These are harvested from ../qualified-strings + +module PprQualifiedStrings where + +import Data.Typeable (Typeable, typeOf) +import qualified Example.ByteStringAscii as Ascii +import qualified Example.ByteStringUtf8 as Utf8 +import qualified Example.Text as Text + +exprs :: IO () +exprs = do + inspect "I'm a String" -- would be an ambiguous type error with OverloadedStrings + inspect Text."I'm a Text" + inspect Ascii."I'm an ASCII bytestring: 語" + inspect Utf8."I'm a UTF8 bytestring: 語" + + inspect """ + I'm a multiline + String value + ! + """ + + inspect Text.""" + I'm a multiline + Text value + ! + """ + + inspect Text . """ + I'm a multiline + Text value + """ + + inspect Text . + """ + I'm a multiline + Text value + """ + +pats :: IO () +pats = do + let text = Text."foo" :: Text + case text of + Text."foo" -> putStrLn "Text.\"foo\" matched" + _ -> putStrLn "Text.\"foo\" did not match" + + let ascii = Ascii."語" :: ByteString + case ascii of + Ascii."語" -> putStrLn "Ascii.\"語\" matched" + _ -> putStrLn "Ascii.\"語\" did not match" + + let utf = Utf8."語" :: ByteString + case utf of + Utf8."語" -> putStrLn "Utf8.\"語\" matched" + _ -> putStrLn "Utf8.\"語\" did not match" + +th :: IO () +th = + $(do + foldr (\stmt acc -> [| $stmt >> $acc |]) [| pure () |] $ + [ [| inspect Text."I'm a Text" |] + , [| inspect Ascii."I'm an ASCII bytestring: 語" |] + , [| inspect Utf8."I'm a Utf8 bytestring: 語" |] + , [| + inspect Text.""" + I'm a multiline + Text string + """ + |] + ] + ) ===================================== testsuite/tests/printer/all.T ===================================== @@ -221,3 +221,4 @@ test('Test25885', [ignore_stderr, req_ppr_deps], makefile_test, ['Test25885']) test('TestLevelImports', [ignore_stderr, req_ppr_deps], makefile_test, ['TestLevelImports']) test('TestNamedDefaults', [ignore_stderr, req_ppr_deps], makefile_test, ['TestNamedDefaults']) test('PprModifiers', [ignore_stderr,req_ppr_deps], makefile_test, ['PprModifiers']) +test('PprQualifiedStrings', [ignore_stderr,req_ppr_deps], makefile_test, ['PprQualifiedStrings']) ===================================== utils/check-exact/ExactPrint.hs ===================================== @@ -3145,6 +3145,12 @@ instance ExactPrint (HsExpr GhcPs) where body' <- markAnnotated body return (HsQual noExtField ctxt' body') + exact (HsQualLit _ (QualLit _ modu (HsQualString src fs))) = do + modu' <- markAnnotated modu + printStringAdvanceA "." + printSourceTextAA src (show (unpackFS fs)) + return (HsQualLit noExtField (QualLit noExtField modu' (HsQualString src fs))) + exact x = error $ "exact HsExpr for:" ++ showAst x -- --------------------------------------------------------------------- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/3268c610d7011d3b0d2a9357f59ab7a… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/3268c610d7011d3b0d2a9357f59ab7a… You're receiving this email because of your account on gitlab.haskell.org.

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