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[Git][ghc/ghc][wip/T27557] Fix three bugs related to required type args and INLINE pragmas
by Simon Peyton Jones (＠simonpj) 04 Aug '26

04 Aug '26

Simon Peyton Jones pushed to branch wip/T27557 at Glasgow Haskell Compiler / GHC Commits: 5086333f by Simon Peyton Jones at 2026-08-04T11:07:24+01:00 Fix three bugs related to required type args and INLINE pragmas * `GHC.Core.Opt.Arity.mkEtaForAllMCo` got the visibility flags back to front, leading to a Lint error (#27557) * The arity in an InlineSaturation is the VisArity not the Arity; the two can differ when we have "required" type arguments. This made the INLINE pragma argument counting go wrong in `makeCorePair` (#27590). * When a simple binding has a type signature, we take special path in `tcPolyCheck`, leading to an outer `AbsBinds` that has no dictionaries, even when the binding is in fact overloaded. That confused the inline-arity computation in `makeCorePair` (#27589). The latter two are fixed using the new function `GHC.HsToCore.Binds.findSatArity`. That actually simplifies the API of `makeCorePair`, which is nice. The first bug is fixed by swapping the visiblity flags in `GHC.Core.Opt.Arity.mkEtaForAllMCo` Getting the INLINE behaviour right led to some perf changes: * Runtime /halved/ on T7954 due to better specialisation * Compile time increased by 6% in T21839c because a bit more inlining happened, as it always should have done. Geometric mean effect on our compile time benchmarks is +0.1%. Metric Decrease: T7954 Metric Increase: T21839c - - - - - 21 changed files: - + changelog.d/T27557 - + changelog.d/T27589 - compiler/GHC/Core/Opt/Arity.hs - compiler/GHC/Hs/Expr.hs - compiler/GHC/HsToCore/Binds.hs - compiler/GHC/HsToCore/Match.hs - compiler/GHC/HsToCore/Ticks.hs - compiler/GHC/Tc/Gen/Bind.hs - compiler/GHC/Tc/Gen/Sig.hs - compiler/GHC/Types/Arity.hs - compiler/GHC/Types/InlinePragma.hs - compiler/GHC/Types/Var.hs - libraries/base/tests/perf/ElemFusionUnknownList_O1.stderr - libraries/base/tests/perf/ElemFusionUnknownList_O2.stderr - + testsuite/tests/simplCore/should_compile/T27589.hs - + testsuite/tests/simplCore/should_compile/T27589.stderr - + testsuite/tests/simplCore/should_compile/T27590.hs - + testsuite/tests/simplCore/should_compile/T27590.stderr - testsuite/tests/simplCore/should_compile/all.T - + testsuite/tests/typecheck/should_compile/T27557.hs - testsuite/tests/typecheck/should_compile/all.T Changes: ===================================== changelog.d/T27557 ===================================== @@ -0,0 +1,8 @@ +section: compiler +issues: #27577 +mrs: !16433 +synopsis: + Fix a Core Lint error involving RequiredTypeArguments +description: + Fixes an issue with a coercion being used for eta expansion storing + the wrong visibility information, which caused a Core Lint error. ===================================== changelog.d/T27589 ===================================== @@ -0,0 +1,10 @@ +section: compiler +issues: #27589 #27590 +mrs: !16433 +synopsis: + Fixes to arity computations +description: + The arity computation for INLINE pragmas now correctly takes into + account required type arguments. Separately, the arity computation + in ``tcPolyCheck`` now consistently handles dictionary arguments, fixing + a short-cut codepath which didn't ===================================== compiler/GHC/Core/Opt/Arity.hs ===================================== @@ -2370,11 +2370,15 @@ mkEtaForAllMCo (Bndr tcv vis) ty mco | otherwise -> mk_fco (mkRepReflCo ty) MCo co -> mk_fco co where - mk_fco co = MCo (mkForAllCo tcv vis coreTyLamForAllTyFlag MRefl co) + mk_fco co = MCo (mkForAllCo tcv coreTyLamForAllTyFlag vis MRefl co) -- coreTyLamForAllTyFlag: See Note [The EtaInfo mechanism], particularly -- the (EtaInfo Invariant). (sym co) wraps a lambda that always has -- a ForAllTyFlag of coreTyLamForAllTyFlag; see Note [Required foralls in Core] -- in GHC.Core.TyCo.Rep + -- + -- Orientation: remember, the output of mkEtaForAllCo goes into an `EI bs mco`, + -- and is SymCo'd in `etaInfoAbs`. Hence the orientation of the visibility + -- flags. A bit of a brain-strain (#27557). {- ************************************************************************ ===================================== compiler/GHC/Hs/Expr.hs ===================================== @@ -1687,10 +1687,11 @@ isSingletonMatchGroup matches | otherwise = False -matchGroupArity :: MatchGroup (GhcPass id) body -> Arity +matchGroupVisArity :: MatchGroup (GhcPass id) body -> VisArity -- This is called before type checking, when mg_arg_tys is not set -matchGroupArity MG { mg_alts = L _ [] } = 1 -- See Note [Empty mg_alts] -matchGroupArity MG { mg_alts = L _ (alt1 : _) } = count isVisArgLPat (hsLMatchPats alt1) +-- Returns the "visible arity" of the MatchGroup i.e. including required type arguments. +matchGroupVisArity MG { mg_alts = L _ [] } = 1 -- See Note [Empty mg_alts] +matchGroupVisArity MG { mg_alts = L _ (alt1 : _) } = count isVisArgLPat (hsLMatchPats alt1) hsLMatchPats :: LMatch (GhcPass id) body -> [LPat (GhcPass id)] hsLMatchPats (L _ (Match { m_pats = L _ pats })) = pats ===================================== compiler/GHC/HsToCore/Binds.hs ===================================== @@ -69,7 +69,7 @@ import GHC.Types.InlinePragma import GHC.Types.Name import GHC.Types.Var.Set import GHC.Types.Var.Env -import GHC.Types.Var( EvVar, mkLocalVar ) +import GHC.Types.Var( EvVar, mkLocalVar, isRuntimePiTyBinder ) import GHC.Types.SrcLoc import GHC.Types.Basic import GHC.Types.Unique.Set( nonDetEltsUniqSet ) @@ -196,7 +196,7 @@ dsHsBind dflags (VarBind { var_id = var = do { core_expr <- dsLExpr expr -- Dictionary bindings are always VarBinds, -- so we only need do this here - ; let core_bind@(id,_) = makeCorePair dflags var False 0 core_expr + ; let core_bind@(id,_) = makeCorePair dflags var False core_expr force_var = if xopt LangExt.Strict dflags then [id] else [] @@ -211,11 +211,11 @@ dsHsBind dflags b@(FunBind { fun_id = L loc fun ; let body' = mkOptTickBox tick body rhs = core_wrap (mkLams args body') - core_binds@(id,_) = makeCorePair dflags fun False 0 rhs + core_binds@(id,_) = makeCorePair dflags fun False rhs force_var -- Bindings are strict when -XStrict is enabled | xopt LangExt.Strict dflags - , matchGroupArity matches == 0 -- no need to force lambdas + , matchGroupVisArity matches == 0 -- no need to force lambdas = [id] | isBangedHsBind b = [id] @@ -303,7 +303,7 @@ dsAbsBinds dflags tyvars dicts exports ; let global_id' = addIdSpecialisations global_id rules main_bind = makeCorePair dflags global_id' (isDefaultMethod prags) - (dictArity dicts) rhs + rhs ; return (force_vars', fromOL spec_binds ++ [main_bind]) } } @@ -386,7 +386,7 @@ dsAbsBinds dflags tyvars dicts exports mk_aux_bind (lcl_id, rhs) = let lcl_w_inline = lookupVarEnv inline_env lcl_id `orElse` lcl_id in - makeCorePair dflags lcl_w_inline False 0 rhs + makeCorePair dflags lcl_w_inline False rhs inline_env :: IdEnv Id -- Maps a monomorphic local Id to one with -- the inline pragma from the source @@ -437,9 +437,9 @@ dsAbsBinds dflags tyvars dicts exports -- the unfolding in the interface file is made in `GHC.Iface.Tidy.addExternal` -- using this information. ------------------------ -makeCorePair :: DynFlags -> Id -> Bool -> Arity -> CoreExpr +makeCorePair :: DynFlags -> Id -> Bool -> CoreExpr -> (Id, CoreExpr) -makeCorePair dflags gbl_id is_default_method dict_arity rhs +makeCorePair dflags gbl_id is_default_method rhs | is_default_method -- Default methods are *always* inlined -- See Note [INLINE and default methods] in GHC.Tc.TyCl.Instance = (gbl_id `setIdUnfolding` mkCompulsoryUnfolding' simpl_opts rhs, rhs) @@ -456,22 +456,43 @@ makeCorePair dflags gbl_id is_default_method dict_arity rhs inline_prag = idInlinePragma gbl_id inlinable_unf = mkInlinableUnfolding simpl_opts StableUserSrc rhs inline_pair - | AppliedToAtLeast arity <- inlinePragmaSaturation inline_prag + | AppliedToAtLeast vis_arity <- inlinePragmaSaturation inline_prag -- Add an Unfolding for an INLINE (but not for NOINLINE) -- And eta-expand the RHS; see Note [Eta-expanding INLINE things] - , let real_arity = dict_arity + arity - -- NB: The arity passed to mkInlineUnfoldingWithArity - -- must take account of the dictionaries - = ( gbl_id `setIdUnfolding` mkInlineUnfoldingWithArity simpl_opts StableUserSrc real_arity rhs - , etaExpand real_arity rhs) + , let runtime_arity = findSatArity vis_arity (idType gbl_id) + -- NB: runtime_arity: the arity passed to mkInlineUnfoldingWithArity + -- must take account of dictionaries and required type args + = ( gbl_id `setIdUnfolding` mkInlineUnfoldingWithArity simpl_opts StableUserSrc + runtime_arity rhs + , etaExpand runtime_arity rhs) | otherwise = pprTrace "makeCorePair: arity missing" (ppr gbl_id) $ (gbl_id `setIdUnfolding` mkInlineUnfoldingNoArity simpl_opts StableUserSrc rhs, rhs) -dictArity :: [Var] -> Arity --- Don't count coercion variables in arity -dictArity dicts = count isId dicts +findSatArity :: VisArity -> Type -> Arity +-- Given the VisArity, find the value Arity of the function. +-- This is the number of runtime-value arguments the function must be applied +-- to before the INLINE pragma fires and inlines the function +-- We must: +-- add one for each invisible dictionary arg; and +-- subtract one for each required type argment +findSatArity vis_arity ty + = go vis_arity pi_bndrs + where + (pi_bndrs, _) = splitPiTys ty + + go vis_arity (bndr : bndrs) + | isInvisiblePiTyBinder bndr = add_bndr bndr (go vis_arity bndrs) + | vis_arity == 0 = 0 + | otherwise = add_bndr bndr (go (vis_arity-1) bndrs) + go vis_arity [] + | vis_arity == 0 = 0 + | otherwise = pprPanic "findSatArity" (ppr vis_arity $$ ppr ty) + + add_bndr :: PiTyBinder -> Arity -> Arity + add_bndr bndr ar | isRuntimePiTyBinder bndr = ar+1 + | otherwise = ar {- Note [Desugaring AbsBinds] ===================================== compiler/GHC/HsToCore/Match.hs ===================================== @@ -737,21 +737,21 @@ Call @match@ with all of this information! -- There are three possible cases for matchWrapper's scrutinees argument: -- -- 1. Nothing Used for FunBind, HsLam, HsLamcase, where there is no explicit scrutinee --- The MatchGroup may have matchGroupArity of 0 or more. Examples: --- f p1 q1 = ... -- matchGroupArity 2 +-- The MatchGroup may have matchGroupVisArity of 0 or more. Examples: +-- f p1 q1 = ... -- matchGroupVisArity 2 -- f p2 q2 = ... -- -- \cases | g1 -> ... -- matchGroupArity 0 -- | g2 -> ... -- -- 2. Just [e] Used for HsCase, RecordUpd; exactly one scrutinee --- The MatchGroup has matchGroupArity of exactly 1. Example: --- case e of p1 -> e1 -- matchGroupArity 1 +-- The MatchGroup has matchGroupVisArity of exactly 1. Example: +-- case e of p1 -> e1 -- matchGroupVisArity 1 -- p2 -> e2 -- -- 3. Just es Used for HsCmdLamCase; zero or more scrutinees -- The MatchGroup has matchGroupArity of (length es). Example: --- \cases p1 q1 -> returnA -< ... -- matchGroupArity 2 +-- \cases p1 q1 -> returnA -< ... -- matchGroupVisArity 2 -- p2 q2 -> ... matchWrapper ===================================== compiler/GHC/HsToCore/Ticks.hs ===================================== @@ -288,7 +288,7 @@ addTickLHsBind (L pos (funBind@(FunBind { fun_id = L _ id, fun_matches = matches -- We don't want to generate code for blacklisted positions -- We don't want redundant ticks on simple pattern bindings -- We don't want to tick non-exported bindings in TickExportedFunctions - let simple = matchGroupArity matches == 0 + let simple = matchGroupVisArity matches == 0 -- A binding is a "simple pattern binding" if it is a -- funbind with zero patterns toplev = null decl_path ===================================== compiler/GHC/Tc/Gen/Bind.hs ===================================== @@ -808,7 +808,7 @@ checkMonomorphismRestriction mbis lbinds restricted (VarBind { var_ext = x }) = dataConCantHappen x restricted b@(PatSynBind {}) = pprPanic "isRestrictedGroup/unrestricted" (ppr b) - restricted_match mg = matchGroupArity mg == 0 + restricted_match mg = matchGroupVisArity mg == 0 -- No args => like a pattern binding -- Some args => a function binding ===================================== compiler/GHC/Tc/Gen/Sig.hs ===================================== @@ -599,26 +599,26 @@ mkPragEnv sigs binds Nothing -> sig -- See Note [Pattern synonym inline arity] -- ar_env maps a local to the arity of its definition - ar_env :: NameEnv Arity - ar_env = foldr lhsBindArity emptyNameEnv binds + ar_env :: NameEnv VisArity + ar_env = foldr lhsBindVisArity emptyNameEnv binds -addInlinePragArity :: Arity -> LSig GhcRn -> LSig GhcRn +addInlinePragArity :: VisArity -> LSig GhcRn -> LSig GhcRn addInlinePragArity ar (L l (InlineSig x nm inl)) = L l (InlineSig x nm (add_inl_arity ar inl)) addInlinePragArity ar (L l (SpecSig x nm ty inl)) = L l (SpecSig x nm ty (add_inl_arity ar inl)) addInlinePragArity ar (L l (SpecSigE n x e inl)) = L l (SpecSigE n x e (add_inl_arity ar inl)) addInlinePragArity _ sig = sig -add_inl_arity :: Arity -> InlinePragma GhcRn -> InlinePragma GhcRn +add_inl_arity :: VisArity -> InlinePragma GhcRn -> InlinePragma GhcRn add_inl_arity ar prag@(InlinePragma { inl_inline = inl_spec }) | Inline {} <- inl_spec -- Add arity only for real INLINE pragmas, not INLINABLE = prag `setInlinePragmaSaturation` AppliedToAtLeast ar | otherwise = prag -lhsBindArity :: LHsBind GhcRn -> NameEnv Arity -> NameEnv Arity -lhsBindArity (L _ (FunBind { fun_id = id, fun_matches = ms })) env - = extendNameEnv env (unLoc id) (matchGroupArity ms) -lhsBindArity _ env = env -- PatBind/VarBind +lhsBindVisArity :: LHsBind GhcRn -> NameEnv Arity -> NameEnv Arity +lhsBindVisArity (L _ (FunBind { fun_id = id, fun_matches = ms })) env + = extendNameEnv env (unLoc id) (matchGroupVisArity ms) +lhsBindVisArity _ env = env -- PatBind/VarBind ----------------- ===================================== compiler/GHC/Types/Arity.hs ===================================== @@ -84,7 +84,14 @@ like Haskell, there is more than one way to count those arguments. forall a b. (Num a, Ord b) => a -> b -> a has arity <= 4 * `VisArity` is the syntactic notion of arity. It is the number of /visible/ - arguments, i.e. arguments that occur visibly in the source code. + arguments, i.e. arguments that occur visibly in the source code. For example: + f1 :: forall a. a -> a + f1 x = x + f2 :: forall a -> a -> a + f2 t x = x + Both have Arity 1 because there is one /value/ argument. + But f1 has VisArity 1 while f2 has VisArity 2, becuase f2 has a required + type argument. In a function call `f x y z`, we can confidently say that f's vis-arity >= 3, simply because we see three arguments [x,y,z]. We write (>=) rather than (==) ===================================== compiler/GHC/Types/InlinePragma.hs ===================================== @@ -104,7 +104,7 @@ import GHC.Prelude import GHC.Data.FastString import GHC.Hs.Extension -import GHC.Types.Arity (Arity) +import GHC.Types.Arity (VisArity) import GHC.Types.SourceText (SourceText(..)) import GHC.Utils.Binary import GHC.Utils.Outputable @@ -125,12 +125,13 @@ infixl 1 `setInlinePragmaActivation`, -- | The arity /at which to/ inline a function. -- This may differ from the function's syntactic arity. data InlineSaturation - = AppliedToAtLeast !Arity + = AppliedToAtLeast !VisArity -- ^ Inline only when applied to @n@ explicit - -- (non-type, non-dictionary) arguments. + -- (required type or value) arguments. -- -- That is, 'AppliedToAtLeast' describes the number of -- *source-code* arguments the thing must be applied to. + | AnySaturation -- ^ There does not exist an explicit number of arguments -- that the inlining process should be applied to. ===================================== compiler/GHC/Types/Var.hs ===================================== @@ -82,7 +82,7 @@ module GHC.Types.Var ( -- * PiTyBinder PiTyBinder(..), PiTyVarBinder, isInvisiblePiTyBinder, isInvisibleAnonPiTyBinder, - isVisiblePiTyBinder, + isVisiblePiTyBinder, isRuntimePiTyBinder, isTyBinder, isNamedPiTyBinder, isAnonPiTyBinder, namedPiTyBinder_maybe, anonPiTyBinderType_maybe, piTyBinderType, @@ -757,7 +757,12 @@ instance NamedThing tv => NamedThing (VarBndr tv flag) where -- not. See Note [PiTyBinders] data PiTyBinder = Named ForAllTyBinder -- A type-lambda binder, with a ForAllTyFlag - | Anon (Scaled Type) FunTyFlag -- A term-lambda binder. Type here can be CoercionTy. + -- Erased (not passed at runtime) if the binder is + -- a type variable; not erased if coercion variable + + | Anon (Scaled Type) FunTyFlag -- A term-lambda binder, passing a runtime value + -- The argument can be a constraint (incl dictionary) + -- or an ordinary value -- The arrow is described by the FunTyFlag deriving Data @@ -792,6 +797,12 @@ namedPiTyBinder_maybe :: PiTyBinder -> Maybe TyCoVar namedPiTyBinder_maybe (Named tv) = Just $ binderVar tv namedPiTyBinder_maybe _ = Nothing +isRuntimePiTyBinder :: PiTyBinder -> Bool +isRuntimePiTyBinder (Anon {}) = True -- Always passed at runtime +isRuntimePiTyBinder (Named (Bndr tcv _)) = isCoVar tcv + -- isCoVar: see Note [Why ForAllTy can quantify over a coercion variable] + -- and Note [Unused coercion variable in ForAllTy], in GHC.Core.TyCo.Rep + -- | Does this binder bind a variable that is /not/ erased? Returns -- 'True' for anonymous binders. isAnonPiTyBinder :: PiTyBinder -> Bool @@ -817,7 +828,7 @@ piTyBinderType (Named (Bndr tv _)) = varType tv piTyBinderType (Anon ty _) = scaledThing ty {- Note [PiTyBinders] -~~~~~~~~~~~~~~~~~~~ +~~~~~~~~~~~~~~~~~~~~~ But a type like forall a. Maybe a -> forall b. (a,b) -> b @@ -830,14 +841,18 @@ argument to a Pi-type. GHC Core currently supports two different Pi-types: * Anon ty1 fun_flag: a non-dependent function type, - written with ->, e.g. ty1 -> ty2 - represented as FunTy ty1 ty2. These are - lifted to Coercions with the corresponding FunCo. + written with ->, e.g. ty1 -> ty2 + represented as FunTy ty1 ty2. + + See wrinkle (PIT1) + + These are lifted to Coercions with the corresponding FunCo. + + * Named (Var tcv forall_flag): a dependent polytype, + written with forall, e.g. forall (a:*). ty + represented as ForAllTy (Bndr a v) ty - * Named (Var tv forall_flag) - A dependent compile-time-only polytype, - written with forall, e.g. forall (a:*). ty - represented as ForAllTy (Bndr a v) ty + See wrinkle (PIT2) Both forms of Pi-types classify terms/types that take an argument. In other words, if `x` is either a function or a polytype, `x arg` makes sense @@ -845,12 +860,16 @@ words, if `x` is either a function or a polytype, `x arg` makes sense Wrinkles -* The Anon constructor of PiTyBinder contains a FunTyFlag. Since +(PIT1) The Anon constructor of PiTyBinder contains a FunTyFlag. Since the PiTyBinder really only describes the /argument/ it should perhaps only have a TypeOrConstraint rather than a full FunTyFlag. But it's very convenient to have the full FunTyFlag, say in mkPiTys, so that's what we do. +(PIT2) The `tcv` in `Named (Var tcv forall_flag) is usually a type variable + but can exceptionally be a coercion variable: see + Note [Why ForAllTy can quantify over a coercion variable]. + If it's a type variable it will be erased; if coercion variable it will not. Note [VarBndrs, ForAllTyBinders, TyConBinders, and visibility] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ===================================== libraries/base/tests/perf/ElemFusionUnknownList_O1.stderr ===================================== @@ -43,17 +43,17 @@ fusionElemFilter jump go1 eta fusionNotElemConcatMap - = \ x x1 -> + = \ x eta -> joinrec { go1 ds = case ds of { [] -> True; : y ys -> - case y of { I# x2 -> - case x of { I# x3 -> - case ==# x3 (+# x2 1#) of { + case y of { I# x1 -> + case x of { I# x2 -> + case ==# x2 (+# x1 1#) of { __DEFAULT -> - case ==# x3 (+# x2 2#) of { + case ==# x2 (+# x1 2#) of { __DEFAULT -> jump go1 ys; 1# -> False }; @@ -62,20 +62,20 @@ fusionNotElemConcatMap } } }; } in - jump go1 x1 + jump go1 eta fusionElemConcatMap - = \ x x1 -> + = \ x eta -> joinrec { go1 ds = case ds of { [] -> False; : y ys -> - case y of { I# x2 -> - case x of { I# x3 -> - case ==# x3 (+# x2 1#) of { + case y of { I# x1 -> + case x of { I# x2 -> + case ==# x2 (+# x1 1#) of { __DEFAULT -> - case ==# x3 (+# x2 2#) of { + case ==# x2 (+# x1 2#) of { __DEFAULT -> jump go1 ys; 1# -> True }; @@ -84,7 +84,7 @@ fusionElemConcatMap } } }; } in - jump go1 x1 + jump go1 eta fusionNotElemMap = \ x eta -> ===================================== libraries/base/tests/perf/ElemFusionUnknownList_O2.stderr ===================================== @@ -77,25 +77,25 @@ fusionElemFilter jump go1 eta fusionNotElemConcatMap - = \ x x1 -> - case x1 of { + = \ x eta -> + case eta of { [] -> True; : y ys -> - case y of { I# x2 -> - case x of { I# x3 -> - case ==# x3 (+# x2 1#) of { + case y of { I# x1 -> + case x of { I# x2 -> + case ==# x2 (+# x1 1#) of { __DEFAULT -> - case ==# x3 (+# x2 2#) of { + case ==# x2 (+# x1 2#) of { __DEFAULT -> joinrec { go1 ds = case ds of { [] -> True; : y1 ys1 -> - case y1 of { I# x4 -> - case ==# x3 (+# x4 1#) of { + case y1 of { I# x3 -> + case ==# x2 (+# x3 1#) of { __DEFAULT -> - case ==# x3 (+# x4 2#) of { + case ==# x2 (+# x3 2#) of { __DEFAULT -> jump go1 ys1; 1# -> False }; @@ -113,25 +113,25 @@ fusionNotElemConcatMap } fusionElemConcatMap - = \ x x1 -> - case x1 of { + = \ x eta -> + case eta of { [] -> False; : y ys -> - case y of { I# x2 -> - case x of { I# x3 -> - case ==# x3 (+# x2 1#) of { + case y of { I# x1 -> + case x of { I# x2 -> + case ==# x2 (+# x1 1#) of { __DEFAULT -> - case ==# x3 (+# x2 2#) of { + case ==# x2 (+# x1 2#) of { __DEFAULT -> joinrec { go1 ds = case ds of { [] -> False; : y1 ys1 -> - case y1 of { I# x4 -> - case ==# x3 (+# x4 1#) of { + case y1 of { I# x3 -> + case ==# x2 (+# x3 1#) of { __DEFAULT -> - case ==# x3 (+# x4 2#) of { + case ==# x2 (+# x3 2#) of { __DEFAULT -> jump go1 ys1; 1# -> True }; ===================================== testsuite/tests/simplCore/should_compile/T27589.hs ===================================== @@ -0,0 +1,9 @@ +module T28589 where + +wombat :: Num a => a -> a +{-# INLINE wombat #-} +wombat x = x+x*x + +g :: Num a => [a] -> [a] +g ys = map wombat ys + -- wombat should not inline here ===================================== testsuite/tests/simplCore/should_compile/T27589.stderr ===================================== @@ -0,0 +1,3 @@ +wombat [InlPrag=INLINE (sat-args=1)] :: forall a. Num a => a -> a +wombat + map @a @a (wombat @a $dNum) ys ===================================== testsuite/tests/simplCore/should_compile/T27590.hs ===================================== @@ -0,0 +1,10 @@ +{-# LANGUAGE RequiredTypeArguments #-} + +module Foo where + +wombat :: forall a -> a -> Maybe a +{-# INLINE wombat #-} +wombat t x = Just x + +g y = wombat Int (y+y) + -- wombat /should/ inline here ===================================== testsuite/tests/simplCore/should_compile/T27590.stderr ===================================== @@ -0,0 +1,2 @@ +wombat [InlPrag=INLINE (sat-args=2)] :: forall a -> a -> Maybe a +wombat ===================================== testsuite/tests/simplCore/should_compile/all.T ===================================== @@ -609,3 +609,5 @@ test('T4081', normal, compile, ['-O -ddump-simpl -dsuppress-uniques -dsuppress-a test('T27261', [extra_files(['T27261_aux.hs'])], multimod_compile, ['T27261', '-v0 -O']) test('T27296', [], makefile_test, ['T27296']) test('T27296b', [], makefile_test, ['T27296b']) +test('T27589', [grep_errmsg(r'wombat')], compile, ['-O -ddump-simpl -dno-typeable-binds -dsuppress-uniques']) +test('T27590', [grep_errmsg(r'wombat')], compile, ['-O -ddump-simpl -dno-typeable-binds -dsuppress-uniques']) ===================================== testsuite/tests/typecheck/should_compile/T27557.hs ===================================== @@ -0,0 +1,9 @@ +{-# LANGUAGE RequiredTypeArguments #-} + +module RequiredTypeArgumentsMkSymCo where + +import Data.Kind (Type) + +f :: forall a . forall (b :: Type) -> a -> a +f t = id +{-# INLINE f #-} ===================================== testsuite/tests/typecheck/should_compile/all.T ===================================== @@ -968,4 +968,4 @@ test('T24464', normal, compile, ['']) test('ExpansionQLIm', normal, compile, ['']) test('T23135', normal, compile, ['']) test('LazyFieldAnnotations', normal, compile, ['']) - +test('T27557', normal, compile, ['']) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/5086333fc5b9df0754819851d40b66d… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/5086333fc5b9df0754819851d40b66d… You're receiving this email because of your account on gitlab.haskell.org. 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[Git][ghc/ghc] Pushed new branch wip/fendor/has-field-hie
by Hannes Siebenhandl (＠fendor) 04 Aug '26

04 Aug '26

Hannes Siebenhandl pushed new branch wip/fendor/has-field-hie at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/fendor/has-field-hie You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc][wip/spj-reinstallable-base2] Allow GHC.Essentials to be hidden
by sheaf (＠sheaf) 04 Aug '26

04 Aug '26

sheaf pushed to branch wip/spj-reinstallable-base2 at Glasgow Haskell Compiler / GHC Commits: 0e2a6606 by sheaf at 2026-08-04T11:14:26+02:00 Allow GHC.Essentials to be hidden - - - - - 23 changed files: - compiler/GHC/Builtin.hs - compiler/GHC/Driver/Downsweep.hs - compiler/GHC/Driver/MakeFile.hs - compiler/GHC/HsToCore.hs - compiler/GHC/Iface/Errors/Ppr.hs - compiler/GHC/Iface/Errors/Types.hs - compiler/GHC/Iface/Load.hs - compiler/GHC/Iface/Make.hs - compiler/GHC/Iface/Recomp.hs - compiler/GHC/Parser/Header.hs - compiler/GHC/Unit/External.hs - compiler/GHC/Unit/Finder.hs - compiler/GHC/Unit/Finder/Types.hs - compiler/GHC/Unit/State.hs - libraries/base/base.cabal.in - testsuite/tests/cabal/T12485/Makefile - testsuite/tests/driver/T27013e/T27013e.stderr - testsuite/tests/driver/T27013f/T27013f.stderr - testsuite/tests/driver/multipleHomeUnits/multipleHomeUnitsModuleVisibility.stderr - testsuite/tests/ghci/scripts/all.T - testsuite/tests/interface-stability/base-exports.stdout - testsuite/tests/interface-stability/base-exports.stdout-javascript-unknown-ghcjs - testsuite/tests/interface-stability/base-exports.stdout-mingw32 The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/0e2a6606e655f602c15f2cf606547d2… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/0e2a6606e655f602c15f2cf606547d2… You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc][wip/sjakobi/T27368-ppr] Cmm: print unreachable blocks under -dppr-debug (#27368)
by Simon Jakobi (＠sjakobi) 04 Aug '26

04 Aug '26

Simon Jakobi pushed to branch wip/sjakobi/T27368-ppr at Glasgow Haskell Compiler / GHC Commits: bab97e52 by Simon Jakobi at 2026-08-04T10:35:15+02:00 Cmm: print unreachable blocks under -dppr-debug (#27368) Unreachable blocks linger in a CmmGraph's block map for most of the Cmm pipeline, but pprCmmGraph only ever printed the blocks reachable from the entry, so dumps looked consistent while the graph was not. Issues like #27368 were hard to debug due to this. pprCmmGraph now appends the stored-but-unreachable blocks under a "// unreachable blocks:" heading when -dppr-debug is on. See Note [unreachable blocks] in GHC.Cmm.Pipeline. Assisted-by: Claude Opus 5 - - - - - 8 changed files: - + changelog.d/T27368-ppr-unreachable-cmm-blocks.md - compiler/GHC/Cmm.hs - compiler/GHC/Cmm/Pipeline.hs - docs/users_guide/debugging.rst - testsuite/tests/cmm/should_compile/Makefile - + testsuite/tests/cmm/should_compile/T27368-ppr-debug.cmm - + testsuite/tests/cmm/should_compile/T27368-ppr-debug.stdout - testsuite/tests/cmm/should_compile/all.T Changes: ===================================== changelog.d/T27368-ppr-unreachable-cmm-blocks.md ===================================== @@ -0,0 +1,10 @@ +section: cmm +issues: #27368 +mrs: !16417 +synopsis: + Cmm dumps now show unreachable blocks under ``-dppr-debug`` +description: + Unreachable blocks stay in a Cmm graph's block map for most of the Cmm + pipeline, but ``-ddump-cmm-*`` only ever printed the blocks reachable from + the graph's entry. Adding ``-dppr-debug`` now appends the stored but + unreachable blocks, which makes bugs like #27368 visible in the dumps. ===================================== compiler/GHC/Cmm.hs ===================================== @@ -151,15 +151,28 @@ instance OutputableP Platform CmmGraph where toBlockMap :: CmmGraph -> LabelMap CmmBlock toBlockMap (CmmGraph {g_graph=GMany NothingO body NothingO}) = body +-- | Print the blocks reachable from the entry, in reverse postorder. +-- +-- Under @-dppr-debug@ the unreachable blocks stored in the graph are appended +-- too. See Note [unreachable blocks] in "GHC.Cmm.Pipeline". pprCmmGraph :: Platform -> CmmGraph -> SDoc pprCmmGraph platform g = text "{" <> text "offset" - $$ nest 2 (vcat $ map (pdoc platform) blocks) + $$ nest 2 (ppr_blocks blocks $$ unreachable) $$ text "}" - where blocks = revPostorder g - -- revPostorder has the side-effect of discarding unreachable code, - -- so pretty-printed Cmm will omit any unreachable blocks. This can - -- sometimes be confusing. + where + ppr_blocks :: [CmmBlock] -> SDoc + ppr_blocks = vcat . map (pdoc platform) + + blocks = revPostorder g + + unreachable = getPprDebug $ \debug -> + if not debug || mapNull dead_blocks + then empty + else text "// unreachable blocks:" + $$ nest 2 (ppr_blocks (mapElems dead_blocks)) + + dead_blocks = foldl' (\bs b -> mapDelete (entryLabel b) bs) (toBlockMap g) blocks revPostorder :: CmmGraph -> [CmmBlock] revPostorder g = {-# SCC "revPostorder" #-} ===================================== compiler/GHC/Cmm/Pipeline.hs ===================================== @@ -357,6 +357,7 @@ containing junk code. These aren't necessarily a problem, but removing them is good because it might save time in the native code generator later. +To make unreachable blocks visible in -ddump-cmm-* output, add -dppr-debug. -} dumpGraph :: Logger -> Platform -> Bool -> DumpFlag -> String -> CmmGraph -> IO () ===================================== docs/users_guide/debugging.rst ===================================== @@ -564,6 +564,11 @@ C-\- representation These flags dump various phases of GHC's C-\- pipeline. +Dumps of Cmm graphs print the blocks reachable from the entry, in reverse +post-order. To also show unreachable blocks, which can linger in the graph, +add :ghc-flag:`-dppr-debug`. These blocks are then listed under a +``// unreachable blocks:`` heading. + .. ghc-flag:: -ddump-cmm-verbose-by-proc :shortdesc: Show output from main C-\- pipeline passes (grouped by proc) :type: dynamic @@ -574,9 +579,6 @@ These flags dump various phases of GHC's C-\- pipeline. the chosen backend. Currently only the NCG backends runs additional passes ( :ghc-flag:`-ddump-opt-cmm` ). - Cmm dumps don't include unreachable blocks since we print - blocks in reverse post-order. - .. ghc-flag:: -ddump-cmm-verbose :shortdesc: Write output from main C-\- pipeline passes to files :type: dynamic ===================================== testsuite/tests/cmm/should_compile/Makefile ===================================== @@ -16,3 +16,11 @@ T16930: T23610: '$(TEST_HC)' $(TEST_HC_OPTS) T23610.cmm -S + +# Keep only the "Parsed Cmm" section (the one stage where the unreachable +# block still exists), masking the goto targets whose label uniques are not +# suppressed by -dsuppress-uniques (#21310). +T27368-ppr-debug: + '$(TEST_HC)' $(TEST_HC_OPTS) -c -no-hs-main -ddump-cmm-verbose-by-proc -dppr-debug -dsuppress-uniques -dsuppress-ticks T27368-ppr-debug.cmm 2>&1 \ + | sed -n '/^==* Parsed Cmm/,/^ \}\]/p' \ + | sed 's/goto c[0-9A-Za-z]*/goto _lbl_/g' ===================================== testsuite/tests/cmm/should_compile/T27368-ppr-debug.cmm ===================================== @@ -0,0 +1,19 @@ +#include "Cmm.h" + +// The block "dead" is stored in the graph but no block branches to it, so it +// only shows up in Cmm dumps under -dppr-debug. +testUnreachable (W_ x) +{ + if (x > 0) { + goto live; + } + return (x); + +dead: + x = x + 42; + return (x); + +live: + x = x - 1; + return (x); +} ===================================== testsuite/tests/cmm/should_compile/T27368-ppr-debug.stdout ===================================== @@ -0,0 +1,27 @@ +==================== Parsed Cmm ==================== +[testUnreachable() { // [R1] + { info_tbls: [] + stack_info: arg_space: 8 + } + {offset + _lbl_: + __locVar_::I64 = R1; + if (__locVar_::I64 > 0) goto _lbl_; else goto _lbl_; + _lbl_: + goto _lbl_; + _lbl_: + __locVar_::I64 = __locVar_::I64 - 1; + R1 = __locVar_::I64; + call (P64[(old + 8)])(R1) args: 8, res: 0, upd: 8; + _lbl_: + goto _lbl_; + _lbl_: + R1 = __locVar_::I64; + call (P64[(old + 8)])(R1) args: 8, res: 0, upd: 8; + // unreachable blocks: + _lbl_: + __locVar_::I64 = __locVar_::I64 + 42; + R1 = __locVar_::I64; + call (P64[(old + 8)])(R1) args: 8, res: 0, upd: 8; + } + }] ===================================== testsuite/tests/cmm/should_compile/all.T ===================================== @@ -13,6 +13,9 @@ test('T20725', normal, compile, ['-package ghc']) test('T23610', normal, makefile_test, ['T23610']) test('T24224', [cmm_src, grep_errmsg(r'(F64.*);', [1]), only_ways(['normal'])], compile, ['-no-hs-main -ddump-cmm -dsuppress-all -dsuppress-uniques']) test('T24474', cmm_src, compile, ['-optc-g3']) +# -dppr-debug makes stored-but-unreachable blocks visible in Cmm dumps (#27368). +# Skipped on wordsize(32) targets, where the dump would say I32/P32. +test('T27368-ppr-debug', [when(wordsize(32), skip)], makefile_test, ['T27368-ppr-debug']) test('T24474-cmm-gets-c-opts', cmm_src, compile, ['-optc-DFOO']) test('T24474-cmm-opt-order', cmm_src, compile, ['-optc-DFOO ' '-optCmmP-UFOO ' View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/bab97e52fda661ac21774bf3bd0ee43… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/bab97e52fda661ac21774bf3bd0ee43… You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc] Pushed new branch wip/mangoiv/ci-stages
by Magnus (＠MangoIV) 04 Aug '26

04 Aug '26

Magnus pushed new branch wip/mangoiv/ci-stages at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/mangoiv/ci-stages You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc][wip/marge_bot_batch_merge_job] 8 commits: testsuite: Don't crash on non-UTF-8 test output
by Marge Bot (＠marge-bot) 04 Aug '26

04 Aug '26

Marge Bot pushed to branch wip/marge_bot_batch_merge_job at Glasgow Haskell Compiler / GHC Commits: 05a70d53 by Simon Jakobi at 2026-08-04T03:58:59-04:00 testsuite: Don't crash on non-UTF-8 test output read_stdout, read_stderr_for, read_comp_stderr and read_diff decoded strictly (the first three with UTF-8, read_diff with the locale encoding), so a test emitting invalid UTF-8 (binary output, or a crash truncating a multi-byte character) raised UnicodeDecodeError and was reported as a framework failure instead of its actual result. Decode with errors='replace', like read_no_crs and safe_print. Assisted-by: Claude Fable 5 - - - - - c463253f by Simon Jakobi at 2026-08-04T03:58:59-04:00 testsuite: Colorize the test summary, also in CI The summary headings were plain, and SUMMARY was colored unconditionally, so the escapes also ended up in the file written by --summary-file. Color is now decided per output sink via term_color.colored_if; see the comments in term_color. CI logs are not a tty, but GitLab's log viewer renders ANSI colors, so add --force-colors and pass it in .gitlab/ci.sh. Assisted-by: Claude Opus 5 - - - - - 263683a7 by Simon Jakobi at 2026-08-04T03:58:59-04:00 testsuite: Repeat unexpected failure output in the summary Finding out why a test failed meant scrolling back through a possibly very long log to the point where the test ran. The summary now repeats the captured output of unexpected failures, before the statistics, so the most interesting part is at the end of the log (#16720). Output mismatches report their diff instead of the mismatching stream (see Note [Redundant output in test results]). The repeated output is bounded per stream, and skipped altogether beyond MAX_SUMMARY_OUTPUT_TESTS failure blocks. Tests failing identically in several ways share one block. Test results now report a source-relative directory, stable regardless of where the run was started from. Assisted-by: Claude Fable 5 - - - - - e98becfa by Simon Jakobi at 2026-08-04T03:59:00-04:00 Word64Map: add compareSize compareSize m c compares the size of a map to an Int, but unlike compare (size m) c it stops traversing the map once the outcome is determined. Based on https://github.com/haskell/containers/pull/1139 Assisted-by: Claude Opus 5 - - - - - 556190e3 by Simon Jakobi at 2026-08-04T03:59:00-04:00 Use a pigeonhole sort for deterministic UniqDFM iteration Deterministic UniqDFM iteration used a list mergesort, allocating O(n log n) cons cells and contributing significantly to compiler allocations (#27459). Use a pigeonhole sort where appropriate, while retaining the mergesort fallback. See Note [Sorting a UDFM] and Note [Cost of deterministic iteration]. ------------------------- Metric Decrease: InstanceMatching InstanceMatching1 ManyAlternatives T13719 ------------------------- Assisted-by: gpt-5.6-sol via Codex CLI - - - - - fde542e0 by Vladislav Zavialov at 2026-08-04T03:59:01-04:00 Discard type arguments in tcPatToExpr (#27440, #27583) The builder expression of an implicitly bidirectional pattern synonym must not mention types written in the RHS: * Invisible type arguments led to a panic (#27440) * Required type arguments failed with out-of-scope variables (#27583) Both are now discarded, following the precedent established by pattern signatures (#9867). Discarding type arguments takes some care: a type pattern cannot be told from a value pattern by syntax alone, as the `type` keyword may be omitted. Consider: data T a b c where MkT :: forall a. forall b c -> a -> T a b c pattern P :: x -> T x y z pattern P x = MkT @a (type b) c x In P's right-hand side, `@a` and `type b` are clearly type arguments, but what about `c` and `x`? We can only tell by matching the patterns against MkT's type. So tcPatToExpr now runs in TcM and matches the arguments against the constructor's TyVarBinders using zipPatsBndrs, which is made public for this purpose. The resulting builder is $bP x = MkT _ _ x. See Note [Discarding types in the builder expression]. Test cases: T27440a T27440b T27440c T27440d T27440e T27583a T27583b T27583c T27583d T27583e T27583f T27583g Assisted-by: Claude Opus 5 - - - - - 898d5cff by Vladislav Zavialov at 2026-08-04T03:59:02-04:00 Test case for #20902 Starting with GHC 9.14.1 (the first major release to include 51e3ec83), and from point releases GHC 9.10.2 and GHC 9.12.3 (backports cc4470be68 and b30f25591e), all examples in this ticket are handled as expected. - - - - - e8911cb9 by Alan Zimmerman at 2026-08-04T03:59:03-04:00 EPA: Remove LocatedP, last use in WarningTxt The last step of removing LocatedP, by moving the AnnPragma for WarningTxt into its TTG extension point instead. This also allows us to remove LocatedP and SrcSpanAnnP - - - - - 43 changed files: - .gitlab/ci.sh - + changelog.d/T27440 - + changelog.d/T27583 - compiler/GHC/Builtin/Utils.hs - compiler/GHC/Data/Word64Map/Internal.hs - compiler/GHC/Data/Word64Map/Lazy.hs - compiler/GHC/Data/Word64Map/Strict.hs - compiler/GHC/Data/Word64Map/Strict/Internal.hs - compiler/GHC/Hs/Decls.hs - compiler/GHC/Hs/Dump.hs - compiler/GHC/Iface/Syntax.hs - compiler/GHC/Iface/Warnings.hs - compiler/GHC/Parser.y - compiler/GHC/Parser/Annotation.hs - compiler/GHC/Tc/Gen/Pat.hs - compiler/GHC/Tc/TyCl/PatSyn.hs - compiler/GHC/Types/Unique/DFM.hs - compiler/GHC/Unit/Module/Warnings.hs - testsuite/driver/runtests.py - testsuite/driver/term_color.py - testsuite/driver/testlib.py - + testsuite/tests/patsyn/should_compile/T27440a.hs - + testsuite/tests/patsyn/should_compile/T27440b.hs - + testsuite/tests/patsyn/should_compile/T27440c.hs - testsuite/tests/patsyn/should_compile/all.T - + testsuite/tests/patsyn/should_fail/T27440d.hs - + testsuite/tests/patsyn/should_fail/T27440d.stderr - testsuite/tests/patsyn/should_fail/all.T - + testsuite/tests/th/T20902.hs - testsuite/tests/th/all.T - + testsuite/tests/vdq-rta/should_compile/T27583a.hs - + testsuite/tests/vdq-rta/should_compile/T27583b.hs - + testsuite/tests/vdq-rta/should_compile/T27583c.hs - + testsuite/tests/vdq-rta/should_compile/T27583d.hs - + testsuite/tests/vdq-rta/should_compile/T27583e.hs - + testsuite/tests/vdq-rta/should_compile/T27583g.hs - testsuite/tests/vdq-rta/should_compile/all.T - + testsuite/tests/vdq-rta/should_fail/T27440e.hs - + testsuite/tests/vdq-rta/should_fail/T27440e.stderr - + testsuite/tests/vdq-rta/should_fail/T27583f.hs - + testsuite/tests/vdq-rta/should_fail/T27583f.stderr - testsuite/tests/vdq-rta/should_fail/all.T - utils/check-exact/ExactPrint.hs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/2791ab7aad7e2052945c56c4d4dad9… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/2791ab7aad7e2052945c56c4d4dad9… You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc][wip/T27455] 203 commits: Add missing req_interp modifier to T18441fail3 and T18441fail19
by Zubin (＠wz1000) 04 Aug '26

04 Aug '26

Zubin pushed to branch wip/T27455 at Glasgow Haskell Compiler / GHC Commits: 09326ca6 by Matthew Pickering at 2026-06-20T23:41:12+02:00 Add missing req_interp modifier to T18441fail3 and T18441fail19 These tests require the interpreter but they were failing in a different way with the javascript backend because the interpreter was disabled and stderr is ignored by the test. - - - - - 521e55bf by Matthew Pickering at 2026-06-20T23:41:13+02:00 hadrian: Fill in more of the default.host toolchain file When you are building a cross compiler this file will be used to build stage1 and it's libraries, so we need enough information here to work accurately. There is still more work to be done (see for example, word size is still fixed). - - - - - 23c9b6c3 by Matthew Pickering at 2026-06-20T23:42:52+02:00 hadrian: Build stage 2 cross compilers * Most of hadrian is abstracted over the stage in order to remove the assumption that the target of all stages is the same platform. This allows the RTS to be built for two different targets for example. * Abstracts the bindist creation logic to allow building either normal or cross bindists. Normal bindists use stage 1 libraries and a stage 2 compiler. Cross bindists use stage 2 libararies and a stage 2 compiler. * hadrian: Make binary-dist-dir the default build target. This allows us to have the logic in one place about which libraries/stages to build with cross compilers. Fixes #24192 New hadrian target: * `binary-dist-dir-cross`: Build a cross compiler bindist (compiler = stage 1, libraries = stage 2) This commit also contains various changes to make stage2 compilers feasible. ------------------------- Metric Decrease: LinkableUsage02 ManyAlternatives ManyConstructors MultiComponentModulesRecomp MultiLayerModulesRecomp RecordUpdPerf T10421 T12150 T12227 T12425 T12707 T13035 T13379 T13820 T15703 T16577 T18140 T18282 T18698a T18698b T18923 T1969 T20049 T21839c T3294 T4801 T5030 T5321FD T5321Fun T5631 T5642 T6048 T783 T9020 T9198 T9233 T9630 T9872d T9961 parsing001 T3064 Metric Increase: T26989 hard_hole_fits ------------------------- Co-authored-by: Sven Tennie <sven.tennie(a)gmail.com> - - - - - 26fed8ab by Matthew Pickering at 2026-06-20T23:42:52+02:00 ci: Test cross bindists We remove the special logic for testing in-tree cross compilers and instead test cross compiler bindists, like we do for all other platforms. - - - - - 80c8910e by Matthew Pickering at 2026-06-20T23:42:52+02:00 ci: Introduce CROSS_STAGE variable In preparation for building and testing stage3 bindists we introduce the CROSS_STAGE variable which is used by a CI job to determine what kind of bindist the CI job should produce. At the moment we are only using CROSS_STAGE=2 but in the future we will have some jobs which set CROSS_STAGE=3 to produce native bindists for a target, but produced by a cross compiler, which can be tested on by another CI job on the native platform. CROSS_STAGE=2: Build a normal cross compiler bindist CROSS_STAGE=3: Build a stage 3 bindist, one which is a native compiler and library for the target - - - - - 8215573d by Sven Tennie at 2026-06-20T23:42:52+02:00 ci: Increase timeout for emulators Test runs with emulators naturally take longer than on native machines. Generate jobs.yml - - - - - 5acb7dbc by Matthew Pickering at 2026-06-20T23:42:52+02:00 ci: Javascript don't set CROSS_EMULATOR There is no CROSS_EMULATOR needed to run javascript binaries, so we don't set the CROSS_EMULATOR to some dummy value. - - - - - 48345343 by Sven Tennie at 2026-06-20T23:42:52+02:00 Javascript skip T23697 See #22355 about how HSC2HS and the Javascript target don't play well together. - - - - - 5e44fd05 by Sven Tennie at 2026-06-20T23:42:52+02:00 Mark T24602 as fragile It was skipped before (due to CROSS_EMULATOR being set, which changed for JS), so we don't make things worse by marking it as fragile. - - - - - ab349ec2 by Sven Tennie at 2026-06-20T23:42:52+02:00 Fix T22744 for GHCJS In fact, this test needs Template Haskell, not necessarily an interpreter. - - - - - c73352d8 by Sven Tennie at 2026-06-20T23:42:52+02:00 haddock-test: fix GHCJS haddock test failures Add --ghc-pkg-path flag support so haddock test runner can find cross-prefixed ghc-pkg (e.g. javascript-unknown-ghcjs-ghc-pkg) which is not on $PATH in cross install directories. Skip haddockHtmlTest on GHCJS: Threaded.hs uses forkOS in a TH splice, which GHCJS RTS doesn't support. Mark with js_skip in all.T. - - - - - 5e814e76 by Andreas Klebinger at 2026-06-22T23:00:24-04:00 compiler: Deduplicate hscTidy This function was accidentally duplicated during a refactor. Fixes #27351 - - - - - 473b97eb by sheaf at 2026-06-22T23:01:22-04:00 Avoid mkTick in Core Prep breaking ANF (part II) Hotfix for 2f9579765f55b3920ceb2e04995ff41a9d0e2d4e fixing a small oversight in the call to tickTickedExpr from mkTick, in which we improperly recursively called mkTick without passing on the preserve_anf flag. Fixes #27386 - - - - - 9284a1f7 by Simon Hengel at 2026-06-23T05:55:33-04:00 Don't use global variables to address concurrency bugs! (fixes #27234) This was originally introduce with 88f38b03025386f0f1e8f5861eed67d80495168a to address #17922. In this specific case a better fix would have been to synchronize on stderr: withHandle_ "stderrSupportsAnsiColors" stderr $ \ _ -> do ... But apparently the dependency on `terminfo` was removed in 32ab07bf3d6ce45e8ea5b55e8095174a6b42a7f0, preventing #17922 in the first place. - - - - - 44309cd3 by Alan Zimmerman at 2026-06-23T05:56:20-04:00 EPA: remove LocatedL / SrcSpanAnnL and LocatedLI / SrcSpanAnnLI This is part of a refactor towards only having LocatedA / SrcSpanAnnA It removes the stated items, but has to add back one for BooleanFormula, LocatedBF / SrcSpanAnnBF This commit also use the HsConDetails RecCon extension point to capture the braces in a record constructor - - - - - 2f6a5534 by Simon Jakobi at 2026-06-23T15:46:20+02:00 Add -dstable-core-dump-order for stable Core dump ordering (#27296) The order of top-level bindings in Core dumps (-ddump-simpl etc.) is the compiler's Unique-sensitive internal processing order, so an unrelated upstream change can reorder them and defeat a textual diff of two dumps. This adds an opt-in flag -dstable-core-dump-order that reorders the top-level bindings of dumps routed through dumpPassResult into a stable, Unique-independent order, so two dumps line up across rebuilds. See Note [Stable Core dump order] in GHC.Core.Ppr for the sort key and its rationale. Adds tests T27296 (binders GHC emits in non-source order by default, asserted to come out stably ordered under the flag) and T27296b (an untidied -ddump-float-out dump pinning the ordering of the anonymous lvl floats by literal value). Co-Authored-By: Claude Opus 4.8 <noreply(a)anthropic.com> - - - - - 141986e3 by mangoiv at 2026-06-24T15:51:14-04:00 compiler: refactor error reporting code for ExplicitLevelImports Refactors error reporting code for ExplicitLevelImports to pass in a RdrName and a GlobalReaderElt to be able to report errors that are faithful to the source and to more precisely distinguish between names that are in scope from different qualifications. Fixes #27385 and #26616 - - - - - aa7df6b6 by Simon Hengel at 2026-06-24T15:52:18-04:00 Set GHC_VERSION when calling custom pre-processors (see #25952) (so that pre-processors can emit backwards compatible code) - - - - - a9e494f2 by Simon Hengel at 2026-06-24T15:54:08-04:00 Add a flag to control GHCi specific error hints (close #27409) - - - - - a805b2a2 by Simon Hengel at 2026-06-24T15:55:20-04:00 Reference correct package in error messages for reexported modules (fixes #27417) - - - - - f235d183 by Simon Jakobi at 2026-06-25T05:51:18-04:00 Add explicit setBit/clearBit/complementBit for instance Bits Integer (#21176) The default setBit, clearBit, and complementBit methods allocate intermediate Integers per call. Define them explicitly via the new integerSetBit[#], integerClearBit[#] and integerComplementBit[#], built on the BigNat# primitives, which avoid those allocations. Allocation is not eliminated entirely -- the negative (IN) cases would need in-place mutation, which is left as future work. The default methods constant-folded on literal arguments via the integerOr/integerAnd/integerXor rules, which fold literal Integers of any size. The explicit functions have no such rule, so they (their Word-argument wrappers, and the Bits Integer methods) are marked INLINE to expose the underlying primops to the simplifier; see Note [INLINE for constant folding of bit operations]. This restores folding only on the small-int (IS) path -- large literal Integers (IP/IN) are no longer constant-folded, a minor regression for that case. T8832 covers the IS-path folding. The new golden-output test T21176 checks all three operations against the default implementations across the sign/size boundaries, recording each result plus its integerCheck validity. The base and ghc-bignum interface- stability export goldens gain the new functions. The main changelog entry lives in changelog.d under a new ghc-internal section (renamed from ghc-prim). CLC proposal: https://github.com/haskell/core-libraries-committee/issues/423 Co-Authored-By: Claude Opus 4.7 <noreply(a)anthropic.com> - - - - - 202ed264 by Marc Scholten at 2026-06-25T05:52:21-04:00 haddock: use Text in documentation pipeline This patch moves Haddock's documentation pipeline from String to Text where the data is already textual. It avoids repeated conversions while keeping the existing decoding behavior for invalid UTF-8 docstring chunks. The main changes are: * Render and carry docstrings as Text in Haddock-facing paths. * Use the Binary Text instance from GHC.Utils.Binary for Haddock interface files, and bump the Haddock binary interface version. * Add a FastString HTML instance so XHTML rendering avoids intermediate String allocation. * Keep HsDocStringChunk decoding lenient, matching the previous unpackHDSC behavior on invalid UTF-8 input. * Update the xhtml submodule to 3000.4.1.0, which contains the apostrophe escaping fix used by the Haddock test output. Co-authored-by: copilot-swe-agent[bot] <198982749%2BCopilot(a)users.noreply.github.com> Co-authored-by: Claude Opus 4.5 <noreply(a)anthropic.com> Assisted-by: Codex <codex(a)openai.com> - - - - - a72ff58f by mangoiv at 2026-06-25T05:53:07-04:00 compiler: rename ZonkAny to UnusedType and add pretty printing logic ZonkAny is a hard to understand name for users who do not know how the compiler works internally. Additionally, it is confusing that ZonkAny, while being a concrete type *represents* a meta variable, espeically in the compiler output. This patch changes the name of ZonkAny to UnusedType which is closer to its intended semantics and adds special pretty printing logic to display this type in the same fashion the compiler displays meta variables in other places, whenever they leak from the implementation to the user. It also exports the type from ghc-internal:GHC.Internal.Types in order to expose documentation. Fixes #27390 Co-Authored-By: Sam Derbyshire <sam.derbyshire(a)gmail.com> - - - - - 6813f002 by Simon Jakobi at 2026-06-26T04:51:47-04:00 Reg.Linear: drop Platform argument from most FR (FreeRegs) methods The FR class has one instance per CPU architecture, so any architecture-constant information its methods derived from the Platform argument can instead be baked into the instance. This removes the now needless Platform argument from frAllocateReg, frGetFreeRegs and frReleaseReg. frInitFreeRegs keeps its Platform argument: the initial allocatable set is genuinely platform-dependent, see Note [Aarch64 Register x18 at Darwin and Windows]. Fixes #26665 Co-Authored-By: Claude Opus 4.8 <noreply(a)anthropic.com> - - - - - 3b2a9409 by Zubin Duggal at 2026-06-26T04:52:39-04:00 testsuite: Report fragile failures as skipped in JUnit output - - - - - 27463426 by Rodrigo Mesquita at 2026-06-26T20:54:58-04:00 perf: Share Module in Iface Symbol Table This commit modifies the structure of the serialized `SymbolTable Name` to then re-use and share the `Module` (both on disk and in memory) across all `Name`s from the same module. The new structure looks like: <total name count> $modules.size for (mod, names) in $modules: $mod $names.size for table_ix, occ in $names $table_ix $occ i.e. we put the module just once, followed by all names in that module. When deserializing, we deserialize the module just once, and all the following `Name`s are constructed with a pointer to that same decoded `Module`. In `hoogle-test`, we must use `DNameEnv` rather than `Map Name`, otherwise the output fixities order was susceptible to changes in the uniques assigned to each Names, which is not stable. Fixes #27401 ------------------------- Metric Decrease: InstanceMatching LinkableUsage01 LinkableUsage02 hard_hole_fits ------------------------- - - - - - 412f1675 by Simon Hengel at 2026-06-26T20:55:41-04:00 Rename `MCDiagnostic` to `InternalMCDiagnostic` `MCDiagnostic` is meant to be used for compiler diagnostics. Any code that creates `MCDiagnostic` directly, without going through `GHC.Driver.Errors.printMessage`, sidesteps `-fdiagnostics-as-json` (see e.g. !14616, !14475, !14492 !14548). To avoid this in the future, this change more narrowly controls who creates `MCDiagnostic` (see #24113). - - - - - 6f212121 by Facundo Domínguez at 2026-06-26T20:56:27-04:00 Encapsulate options of occurAnalysePgm in a record - - - - - adfbb179 by Facundo Domínguez at 2026-06-26T20:56:27-04:00 Allow to configure the occurrence analyser to retain some dead bindings This is needed by plugins that are the only consumers of a binding which is otherwise unused in the program. See Note [Controlling elimination of dead bindings in occurrence analysis] added in this commit, or https://gitlab.haskell.org/ghc/ghc/-/issues/27240 for more discussion. - - - - - c745b11f by Copilot at 2026-06-26T20:56:27-04:00 Address documentation feedback - - - - - 2c2a4a2a by Copilot at 2026-06-26T20:56:27-04:00 Keep the imp_rules parameter of occurPgmAnalysePgm and add occ_opts to OccEnv - - - - - e2262b0e by Copilot at 2026-06-26T20:56:27-04:00 Strengthen T27240.hs with a binding that should be removed - - - - - 5f9d9268 by Copilot at 2026-06-26T20:56:27-04:00 Move the reference #27240 to a related paragraph - - - - - d86d2644 by Simon Hengel at 2026-06-26T20:57:10-04:00 Remove deprecated flag `-ddump-json` (see #24113) This was first deprecated in 9.10.1. - - - - - 3b15ff03 by Simon Jakobi at 2026-06-27T18:48:34+02:00 Tweak mk_mod_usage_info * Use O(log n) `elemModuleEnv` instead of O(n) `elem` to filter the direct imports. * Use `nonDetModuleEnvKeys` to avoid sorting the ent_map keys twice. * Prepend the presumably shorter list when creating all_mods with `(++)`. Actually this eliminates the `(++)` entirely, as it seems to fuse with the `filter` expression. As a result there is a tiny speed-up when generating the .hi-files for modules with many imports. None of the changes affect compilation determinism as the module list is explicitly sorted to ensure a canonical order. - - - - - 2d0fd154 by Alan Zimmerman at 2026-06-29T11:44:00-04:00 EPA: Remove LocatedC / SrcSpanAnnC This is part of a cleanup of the zoo of SrcSpanAnnXXX types for exact print annotations. This one removes SrcSpanAnnC used for storing exact print annotations for contexts. It replaces it with an explicit `HsContext` data type that carries the annotations and the context. So, replace type HsContext pass = [LHsType pass] with type HsContext pass = HsContextDetails pass (LHsType pass) data HsContextDetails pass arg = HsContext { hsc_ext :: !(XHsContext pass) , hsc_ctxt :: [arg] } | XHsContextDetails !(XXHsContextDetails pass) We need the parameterised HsContextDetails because it is used both for HsQual carrying 'LHsExpr p' and "normal" contexts carrying 'LHsType p'. - - - - - cca0d589 by Luite Stegeman at 2026-06-30T13:33:40-04:00 rts: handle large AP closures in compacting GC The function update_fwd_large in the compacting GC could run into an unexpected object with the following error: internal error: update_fwd_large: unknown/strange object 24 Closure type 24 is the AP closure, which was not handled in upd_fwd_large. This patch adds handling them. fixes #27434 - - - - - 42935858 by Luite Stegeman at 2026-06-30T13:33:40-04:00 testsuite: use compacting_gc way instead of hardcoding +RTS -c - - - - - bf7b5ce6 by Alan Zimmerman at 2026-06-30T13:34:23-04:00 EPA: Remove LocatedLW from LStmtLR HsDo already had its XDo extension point for an AnnList, which also appeared in LocatedLW. So we remove the redundant one and use the one inside HsDo as originally intended. Also delete LocatedLC/LocatedLS as they were unused - - - - - d7cfea49 by Recursion Ninja at 2026-06-30T21:37:12-04:00 Decoupling 'L.H.S' from 'GHC.Types.SourceText' * Migrated 'IntegralLit' to 'L.H.S.Lit'. * Migrated 'FractionalLit' to 'L.H.S.Lit'. * Migrated 'StringLiteral' to 'L.H.S.Lit'. * Added TTG extension points to the types above. * Added nice export list to 'GHC.Hs.Lit'. * Added 'rnOverLitVal' and 'tcOverLitVal' functions to 'GHC.Hs.Lit'. * Added instance 'Anno (StringLiteral (GhcPass p)) = SrcSpanAnnN' * Moved [Notes] about 'SourceText' from 'L.H.S.*' to 'GHC.*'. * Removed all references to 'SourceText' from 'L.H.S'. * Removed the trailing comma record field from 'StringLiteral' * Renamed exported functions for nomenclature consistency. * Deprecated the renamed functions Fixes #26953 - - - - - a1f2558b by Recursion Ninja at 2026-06-30T21:37:12-04:00 Monomorphising GHC pass parameters where appropriate - - - - - 7bf9e3c5 by Teo Camarasu at 2026-06-30T21:38:03-04:00 Make Q abstract This patch aims to clearly demarcate the internal and external interfaces of Q. In the past the `Quasi` typeclass was both part of the external, public-facing interface, and was used to give the implementation of `Q`. Now we separate out these two distinct roles. `Quasi` continues to exist in the public interface, but we introduce a new `MetaHandlers` type, which is equivalent to `Dict Quasi`. `Q a` is now defined to be `MetaHandlers -> IO a`, and, crucially, the constructor and the new `MetaHandlers` type are not exposed from the public interface. This gives us the ability to vary the interface on the GHC side without forcing a breaking change on the `template-haskell` side. Similarly `template-haskell` has more freedom to change the `Quasi` typeclass without needing any changes in `lib:ghc`. Implements https://github.com/ghc-proposals/ghc-proposals/pull/700 Resolves #27341 - - - - - 4262af36 by L0neGamer at 2026-06-30T21:38:56-04:00 generically defines mconcat in terms of internal type's Semigroup instance add changelog entry use simpler definition for mconcat `nonEmpty` isn't available yet; inline branches in case add test case fixup generically defines mconcat in terms of internal type's Semigroup instance add comment on Generically and deriving mishaps swap mconcat to foldr version add some strictness testing for mconcat add to `base` changelog entry - - - - - e22ad997 by Cheng Shao at 2026-06-30T21:39:43-04:00 hadrian/rts: fix unregisterised build for gcc 15+ This patch fixes unregisterised build for gcc 15+: - Pass -optc-Wno-error in hadrian when +werror enables -optc-Werror, see added comment for details. - For RTS functions that the codegen would emit calls, ensure their real prototype is hidden when the header is included in .hc fies (IN_STG_CODE), and the dummy prototype is provided to match the EFF_ convention. In the future we should get rid of EFF_ (#14647) and remove these hacks, but for now this patch makes unregisterised work again on newer toolchains. Fixes #27404. Co-authored-by: Codex <codex(a)openai.com> - - - - - 3f00f234 by Cheng Shao at 2026-06-30T21:40:32-04:00 compiler: fix missing handling of CmmUnsafeForeignCall node in LayoutStack This patch fixes missing handling of `CmmUnsafeForeignCall` middle node in the `LayoutStack` pass. Before proc-points splitting, this pass computes liveliness of local registers, and spills those alive across a Cmm native call onto the stack. It need to traverse all middle nodes in each block and check whether a local register is an assignee, if so then the previous mapping in `sm_regs` is invalidated and needs to be dropped. However, it didn't handle `CmmUnsafeForeignCall` node which may also assign to a local register. When proc-points splitting is enabled, this can produce an invalid basic block that doesn't properly backup the updated local register to the stack before doing a Cmm call, resulting in completely invalid runtime behavior. The patch also adds a `T27447` regression test. With no-TNTC or with LLVM backend, without the fix the test case would output a stale 0x1111111111111111 value, instead of the expected 0x2222222222222222 output. Fixes #27447. Co-authored-by: Codex <codex(a)openai.com> - - - - - 701088db by Ben Gamari at 2026-07-01T10:34:03-04:00 gitlab-ci: Drop vestigial references to make build system - - - - - 62d54a53 by Ben Gamari at 2026-07-01T10:34:03-04:00 gitlab-ci: Add support for running specifying a job's testsuite ways - - - - - 7f97ac2c by Ben Gamari at 2026-07-01T10:34:03-04:00 gitlab-ci: Run llvm testsuite ways in llvm jobs Addresses #25762. - - - - - 7ea75116 by ARATA Mizuki at 2026-07-01T10:34:03-04:00 testsuite: Add normalise_ddump_deriv setup function Some tests check the result of -ddump-deriv, which may contain INLINE pragmas depending on optimization flags. With normalise_ddump_deriv setup function, INLINE pragmas are stripped off. - - - - - c7a8199f by ARATA Mizuki at 2026-07-01T10:34:03-04:00 testsuite: Use -dsuppress-idinfo to make tests more robust Previously, T18052a and T21755 were failing on 'optasm' and 'optllvm' ways because of visibility of unfoldings. - - - - - a12122e5 by ARATA Mizuki at 2026-07-01T10:34:03-04:00 testsuite: Use a trick to keep large objects alive Previously, T17574 and T19381 were failing on 'optasm' and 'optllvm' ways because of compiler optimizations. Change them to use NOINLINE to prevent unwanted optimizations. - - - - - 1a95b327 by ARATA Mizuki at 2026-07-01T10:34:03-04:00 testsuite: Only run T24224 in 'normal' way This test is a frontend-only one and breaks if optimizations are enabled. - - - - - 8abea737 by ARATA Mizuki at 2026-07-01T10:34:03-04:00 testsuite: Ignore T18118's stderr When optimizations are enabled, the compiler emits a warning (You cannot SPECIALISE ...). The message is not important, so ignore it. - - - - - 9453a722 by ARATA Mizuki at 2026-07-01T10:34:03-04:00 testsuite: Mark T816 and tc216 broken with optimizations These tests are about type checking, so we should not care too much if they are broken with optimizations. See #26952 - - - - - 0aef9ec0 by Ben Gamari at 2026-07-01T10:34:03-04:00 testsuite: ds014 is not longer broken It now appears to pass in the ways it was marked as broken in. Closes #14901. - - - - - 4692d1e4 by Ben Gamari at 2026-07-01T10:34:03-04:00 testsuite: Only run stack cloning tests in the normal way These are too dependent upon code generation specifics to pass in most other ways. - - - - - c154df26 by ARATA Mizuki at 2026-07-01T10:34:03-04:00 testsuite: Update options_ghc_fbyte-code The `-fbyte-code` option used to be overriden by `-fllvm` but it is no longer true since !14872 was merged. I updated the test to accept the new behavior. Closes #27049 - - - - - 5d8bb7b5 by ARATA Mizuki at 2026-07-01T10:34:03-04:00 testsuite: Only run T22744 in 'normal' way This test takes a long time on optimized ways. - - - - - d1e74c8e by ARATA Mizuki at 2026-07-01T10:34:03-04:00 testsuite: Disable tests that use -finfo-table-map on llvm ways Currently, -finfo-table-map does not work with -fllvm. See #26435 - - - - - 3bf38c84 by ARATA Mizuki at 2026-07-01T10:34:03-04:00 testsuite: Don't run T24726 on optimized ways If optimizations are enabled, the rewrite rule just fires and -drule-check will report nothing. - - - - - e4eef116 by ARATA Mizuki at 2026-07-01T10:34:03-04:00 testsuite: Use -fno-unoptimized-core-for-interpreter when running LinkableUsage01/02 Optimizations for the bytecode interpreter are considered experimental, and need a flag to be enabled. - - - - - 234a9872 by ARATA Mizuki at 2026-07-01T10:34:03-04:00 testsuite: Suppress unwanted optimizations on T25284 - - - - - 99a2af2f by ARATA Mizuki at 2026-07-01T10:34:03-04:00 testsuite: Don't run stack_big_ret with optimizations Stack layout may change with optimizations enabled. - - - - - 04c836df by ARATA Mizuki at 2026-07-01T10:34:04-04:00 testsuite: Mark memo001 broken on optimized ways See #27396 - - - - - 1a8a24f4 by ARATA Mizuki at 2026-07-01T10:34:04-04:00 testsuite: Mark syn-perf broken on optimized ways See #27398 - - - - - 40412093 by Duncan Coutts at 2026-07-01T10:34:50-04:00 Add a test for thread scheduler fairness It also tests that the interval timer and context switching works. We also test that fairness is lost when the context switching interval is too coarse for the duration of the test. We add this test before doing surgery on the interval timer, so we have decent coverage. - - - - - 3f34d557 by Duncan Coutts at 2026-07-01T10:34:50-04:00 Make exported stop/startTimer no-ops, and rename internal functions Specifically, internally rename: stop/startTimer to pause/unpauseTimer stop/startTicker to pause/unpauseTicker and keep stop/startTimer as exported functions, but now as no-ops. In the past the stop/startTicker actions were used incorrectly as if they were synchronous, which they are not. See issue #27105. We now document pause/unpackTicker as being async and not to be used for the purpose of concurrency safety. The existing stop/startTimer (note Timer not Ticker, the Timer calls the Ticker!) are also exported from the RTS as a public API. This was historically because the ticker used signals and it was important to suspend the timer signel over a process fork. So these functions were exported to be used by the process and unix libraries. We cannot just remove the RTS exports, but we now make them no-ops, and they can be removed from the process and unix library later. This was already documented in a changelog.d entry no-more-timer-signal but due to changes during the MR process the change to make stop/startTicker into no-ops didn't make it into the earlier MR. - - - - - 02e84e5f by Duncan Coutts at 2026-07-01T10:34:51-04:00 Make exitTicker/exitTimer unconditionally synchronous We never use them asynchronously, and we should never need to do so. And update some related comments. - - - - - 13db6a72 by Duncan Coutts at 2026-07-01T10:34:51-04:00 posix ticker: update and improve comments on (un)pause and exit Clarify what is async vs sync. - - - - - 43d9a07d by Duncan Coutts at 2026-07-01T10:34:51-04:00 posix ticker: split out ppoll/select helper functions Move the #ifdefs out of the main code body by introducing local helper functions and types, which themselves have two implementations (with a common API) based on ppoll or select. This helps improve clarity/readability. - - - - - a5491baa by Duncan Coutts at 2026-07-01T10:34:51-04:00 posix ticker: improve the implementation The existing implementation supported pausing and exiting, with the implementation of pausing reling on a mutex and condition variable. It needed to check the pause and stop shared variables on every iteration. It relies on ppoll or select, to wait on the timeout and also wait on an interrupt fd. The interrupt fd was only used for prompt exit/shutdown, and not for pausing or other notification. The pause only needed a lock and a memory operation, but the pause was not prompt. The resume used a lock, and signaling a cond var. The new implementation uses a somewhat more regular design: every notification is done by setting a shared variable and interrupting/notifying the ticker via the fd. The ticker thread does not need to check any shared variables on normal timer expiry, only when it recevies notification. This may be a micro-optimisation, but the tick occurs 100 times a second by default so any improvements in the hot path are amplified. When the ticker thread does receive notification it can check the various shared variables and update its local state. The blocking relies on using ppoll/select but without a timeout. This avoids the condition var and also allows further notifications when paused (also used for unpausing). This design can be extended with further notification types if needed by using and checking further shared vars (or making existing shared vars an enum or counter). This may be used in future for additional notifications to the ticker thread. This will likely be used to proxy wakeUpRts from a single handler context for example. And this approach, avoiding mutexes, is compatible with use from signal handlers. So overall, it's: * slightly simpler / more regular; * easier to extend with additional notifications; * probably slightly more efficient (but a micro-optimisation); * and supports calling notification from signal handlers - - - - - 5b20821e by Duncan Coutts at 2026-07-01T10:34:51-04:00 posix ticker: further minor local renaming for code clarity Improve the clarity with better choice of names for several local vars and function. - - - - - 1f3ec5e0 by Duncan Coutts at 2026-07-01T10:34:51-04:00 win32 ticker: split out local helper functions - - - - - 596e7307 by Duncan Coutts at 2026-07-01T10:34:51-04:00 win32 ticker: provide guarantee about concurrency and idempotency Use a lock to ensure pause/unpause can be used concurrently. Use a paused variable, protected by the lock, to ensure that pause and unpause are both idempotent. This is what the portable API expects. - - - - - 1870edd7 by Duncan Coutts at 2026-07-01T10:34:51-04:00 win32 ticker: make the initial tick be after one wait interval There is no need to tick immediately. This is consistent with the posix implementation. - - - - - 7c15ab5b by Duncan Coutts at 2026-07-01T10:34:51-04:00 ticker: remove now-unnecessary layer of enable/disable There was an atomic variable used to block *part* of the actions of the tick handler. This still did not make stopTimer synchronous, even for the part of the the handle_tick actions it covered. It also added a more expensive (sequentuially consistent) atomic operation in the hot path for the handle_tick action, whereas our new design requires no atomic ops at all. Now that we have eliminate the need for synchronous stop/startTicker, we don't need this not-quite-working-anyway atomic protocol. The new pause/unpauseTicker is explicitly asynchronous and idempotent. - - - - - 8585f8cb by Duncan Coutts at 2026-07-01T10:34:51-04:00 ticker: add TODOs about issue #27250: too much being done from handle_tick The handle_tick should not perform I/O, block, perform long-running operations or call arbitrary user code. Unfortunately, everything to do with the eventlog (at the moment) falls into all those categories. - - - - - 6e381626 by Duncan Coutts at 2026-07-01T22:29:55+01:00 Adjust releaseCapability_ precondition to allow cap->running_task == NULL There are two use cases for releaseCapability_: 1. The current Task (cap->running_task) releases the Capability. The Capability is marked free, and if there is any work to do, an appropriate Task is woken up. 2. There is no current task (cap->task == NULL), and thus the Capability is idle, and we want to wake up an idle Task to animate the Capability. This case uses always_wakeup. Currently, the precondition for releaseCapability_ is cap->running_task != NULL and so the 2nd use cases have to set cap->running_task (which is then immediately overwritten) just to satisfy the precondition. See the use cases in sendMessage and prodCapability. So we can relax the precondition to be: cap->running_task != NULL || always_wakeup so that in the always_wakeup case, we say it is ok for the cap->running_task to be NULL. This lets us simplify sendMessage and prodCapability. In particular it will allow prodCapability to not need a Task parameter. The ulterior motive for all this is that I want to be able to call prodCapability from an OS thread that is not itself a Task, in persuit of issue #27086: disentangle I/O managers from wakeUpRts. The most straightforward way to wake the RTS is using prodCapability, but the context in which we will need to do that are threads that are not Tasks. - - - - - 89404ebc by Duncan Coutts at 2026-07-01T22:29:55+01:00 prodCapability no longer needs to take a Task param Now that releaseCapability_ can accept cap->running_task == NULL then it is no longer necessary for prodCapability to require a Task. - - - - - 4e60c5f6 by Duncan Coutts at 2026-07-01T22:29:56+01:00 Define prodOneCapability There was an existing declaration for this in the header file, but no definition. Similarly, there is a declaration for prodAllCapabilities but no definition, and we don't need it, so remove the declaration. - - - - - 2527026f by Duncan Coutts at 2026-07-01T22:29:56+01:00 Add a wakeUpRtsViaTicker feature to the posix ticker It proxies a call to wakeUpRts, but crucially, this can be called from a signal handler context. It will be used for ctl-c handling. - - - - - aa5a03a5 by Duncan Coutts at 2026-07-01T22:29:56+01:00 Change how wakeUpRts works Previously it would call wakeupIOManager to get a capability to wake up and run. This works but it entangles the I/O managers with unrelated features: ctl-c handling and idle gc (the two features that use wakeUpRts). The reason it used wakeupIOManager is that this action is safe to use from a posix signal handler, since it just posts bytes to a pipe. Otherwise the more direct approach (used e.g. by sendMessage when the target capability is idle) is to use releaseCapability. But that uses condition variables and mutexes, which are not safe to use from within a signal handler. So instead of entangling the (multiple) I/O managers with this, we make wakeUpRts use the direct approach (using prodOneCapability). On win32 the ctl-c console handler can call wakeUpRts directly, since it is called in a proper thread. On posix, to deal with the signal handler problem, we make the signal handler ask the ticker thread to proxy the call to wakeUpRts, since the ticker thread is also a proper thread. This will allow the I/O managers to no longer be concerned with this. This is good because there are many I/O managers (and they're complicated), but there is (on posix) only one ticker implementation. So this is an overall reduction in coupling and complexity. Fixes issue #27086 - - - - - c6d53c16 by sheaf at 2026-07-02T21:35:44-04:00 Test driver: normalise line numbers into libraries When comparing the stdout of tests that print out callstacks, we can't rely on the stability of exact line:column spans pointing into libraries (e.g. ghc-internal), as any change (such as adding a comment) can change them. This commit addresses this by normalising away line:column in callstacks, but only when those point into internal libraries. We don't do this in general, as the exact span might be important to the test (e.g. for a span within the test module itself). Fixes #27387 - - - - - 81ee62e0 by Alan Zimmerman at 2026-07-02T21:36:33-04:00 EPA: Remove LocatedLW from MatchGroup This is the last usage of LocatedLW / SrcSpanAnnLW - - - - - 925959db by Recursion Ninja at 2026-07-04T04:14:12-04:00 Decoupling 'L.H.S' from 'GHC.Hs.Doc' * Migrated 'GHC.Hs.Doc' and 'GHC.Hs.DocString' AST defintions from 'GHC.*' namespace, to new 'Language.Haskell.Syntax.Doc' module in the 'L.H.S' "namespace." * Updated 'HsDocString to be TTG-parameterised as 'HsDocString pass'. * Added 'GHC.Hs.Extension.Pass': splits 'GhcPass'/'Pass' and all 'HsDocString' TTG instances out of 'GHC.Hs.Extension', which re-exports it unchanged (this is backwards compatible and prevents the introduction of a boot file). * Deleted 'GHC.Hs.Doc.hs-boot'; removed all 'L.H.S.*' imports of 'GHC.Hs.Doc'. * Updated 'GHC.Hs.DocString' to be TTG pass-parameterised throughout; moved 'mkHsDocStringChunk'/'unpackHDSC' here (require 'GHC.Utils.Encoding'). * Split 'GHC.Rename.Doc.rnHsDoc' from 'rnHsDocIdentifiersOnly'. * Updated parser, renamer, typechecker, HIE, and exact-print for new types. * Added 'HsDocString' TTG instances for 'DocNameI' to 'Haddock.Types'. * Killed the last module loop between GHC.* and LHS.*. - Only edges from LHS.* to GHC.Data.FastString now! Resolves #26971 - - - - - b7e24044 by mangoiv at 2026-07-04T04:14:56-04:00 ci: retry fetching test metrics Retry fetching test metrics to make the CI not fail if the services is temporarily unavailable - - - - - 4180af3f by Zubin Duggal at 2026-07-04T04:15:38-04:00 Bump semaphore-compat submodule to 2.0.1 This versions includes some cruicial fixes for darwin - - - - - 242d4317 by sheaf at 2026-07-04T04:16:19-04:00 Remove outdated comment in GHC.Data.ShortText There was a long comment in GHC.Data.ShortText about a workaround that was necessary when bootstrapping with GHC 9.2 and below. The actual logic has since been dropped, but the comment remained. This commit removes the vestigial comment. - - - - - 9b714c4c by Zubin Duggal at 2026-07-05T09:40:36+05:30 CorePrep: Don't speculatively evaluate bindings that we have already discovered to be absent In #25924, we segfault because speculation forces a projection out of a RUBBISH dictionary (which we generated because it absent). Solution: Don't speculate on bindings we already know are absent. Fixes 25924 - - - - - 4a59b3ee by Zubin Duggal at 2026-07-05T09:40:36+05:30 Don't make absent fillers for terminating types In #25924 we discovered that we could speculatively evaluate an absent filler for a dictionary, and project a field (a superclass selector) out of it, resulting in segfaults. Solution: Never make an absent filler or rubbish literal for a terminating type like a dictionary. mkAbsentFiller returns Nothing for isTerminatingType, so worker/wrapper and the specialiser keep the real argument instead. Some small metric decreases because we do a little less work in the simplifier now. Metric Decrease: T9872a T9872b T9872c TcPlugin_RewritePerf - - - - - 383ddcd4 by Alan Zimmerman at 2026-07-06T07:08:16-04:00 EPA: Move the 'where' annotation for PatSynBind This allows us to move it out of the MatchGroup exact print annotation too - - - - - 66d1a5d5 by fendor at 2026-07-07T16:57:56-04:00 Add 'backendInfoTableMapValidity' backend predicate Check whether the backend supports the `-finfo-table-map` flag and ignore it otherwise. Improve by-design documentation of `backendCodeOutput`. `Backend` is **abstract by design**. Make this clearer in `backendCodeOutput` which is incorrectly being used as a proxy for `Backend`. Instead, define the desired property predicates in GHC.Driver.Backend In the process, make `backendCodeOutput` total. - - - - - 74f1071d by fendor at 2026-07-07T16:57:56-04:00 Add failing test for `-finfo-table-map` and bytecode backend If you compile a module using the bytecode backend, with -finfo-table-map, then the info table map doesn't get populated for the module. This is because the -finfo-table-map code path is implemented mostly in the StgToCmm phase which isn't run when creating bytecode. Ticket #27039 - - - - - 28d63bca by mangoiv at 2026-07-07T16:59:16-04:00 ci: don't fail nightly if there have been no changes that night Fixes #27127 - - - - - 4ebfc478 by Rodrigo Mesquita at 2026-07-08T04:47:53-04:00 ttg: Using ShortText over FastString in the AST To make the AST independent of GHC, this commit replaces usages of `FastString` with `HText` in the AST, killing the last edge from Language.Haskell.* to GHC.* modules. Even though we /do/ want to use FastStrings in general -- critically in Names or Ids -- there is no particular reason for the FastStrings that occur in the AST proper to be FastStrings. Strings in the AST are typically unique and don't benefit particularly from being interned FastStrings with Uniques for fast comparison. `HText` is a type synonym for `ShortText` which uses GHC's Modified UTF-8 encoding exclusively. Modified UTF-8 must be used to represent the Haskell AST because the Haskell Report allows surrogate code points. `Data.Text.Text` functions use Standard UTF-8 which replace surrogates with a placeholder value, thus `Data.Text.Text` is unsuitable for AST strings. See the `Language.Haskell.Syntax.Text` module header for more details. Final progress towards #21592 Closes #21628 - - - - - d910b353 by Simon Peyton Jones at 2026-07-08T04:48:36-04:00 Update equality-type documenation in GHC.Builtin.Types.Prim Fix #27466 - - - - - b2530542 by Simon Peyton Jones at 2026-07-08T04:48:36-04:00 Honour -dsuppress-coercions in GHC.Core.TyCo.pprCo Fixes #27467 - - - - - 9a73179a by Facundo Domínguez at 2026-07-08T04:49:26-04:00 Add item to MR checklist asking to squash fixup commits after approval The checklist has an item that reads All commits are either individually buildable or squashed. This item could be checked immediately after sending the merge request though. If reviewers ask for amends later on, and the author amends the merge request, there was no item that would remind the contributors to squash the fixup commits before landing. This commit adds a new item After all approvals and before landing: all fixup commits are squashed with their originating commits. which should be harder to mark as done before approvals have been given. - - - - - ed09895d by Andreas Klebinger at 2026-07-08T16:53:27-04:00 Fix a profiling race condition resulting in segfaults. StgToCmm: Don't assume tagged FUN closures in closureCodeBody. When entering a closure the self/node pointer might not be tagged in some situations when a thunk is evaluated by multiple threads. So we most AND away the tag bits rather than subtracting an expected tag. Apply.cmm: Fix a race condition occuring when a thunk is mutated during GC. In stg_ap_0_fast when might need to run GC before entering a thunk. If this happens another thread or the GC itself might mutate the closure making entering it no longer valid. We now check for this. Add test and changelog for #27123 fixes. - - - - - 67c03eb2 by Cheng Shao at 2026-07-08T16:54:09-04:00 ghc-heap: fix invalid srtlen returned by peekItbl when no-TNTC This patch fixes the no-TNTC code path of `peekItbl` so that it looks at the right memory address when reading the `srt` field from the `StgInfoTable_` struct. Also adds a `T27465` regression test that reproduces the bug on no-TNTC builds before the fix. Fixes #27465. Co-authored-by: Codex <codex(a)openai.com> - - - - - 2ecabb4f by Zubin Duggal at 2026-07-09T09:23:25-04:00 hadrian: binary-dist-dir should not be the default target Revert behaviour to pre 23c9b6c392f52ec9d7a8618b204ff6b885f5fba2 In 23c9b6c392f52ec9d7a8618b204ff6b885f5fba2, we applied the following behaviour change: ``` hadrian: Build stage 2 cross compilers ... * hadrian: Make binary-dist-dir the default build target. This allows us to have the logic in one place about which libraries/stages to build with cross compilers. Fixes #24192 ``` This is a major regression to development experience, a plain hadrian/build --freeze1 now takes ages because we rebuild all docs (which need to go in the binary dist dir). `binary-dist-dir` is the wrong default target for regular GHC development work Fixes #27445 - - - - - e16388e3 by Zubin Duggal at 2026-07-09T09:23:25-04:00 .gitignore: Add the hadrian system.config introduced by commit 23c9b6c392f52ec9d7a8618b204ff6b885f5fba2 Since commit 23c9b6c392f52ec9d7a8618b204ff6b885f5fba2 Author: Matthew Pickering <matthewtpickering(a)gmail.com> Date: Thu Dec 21 16:17:41 2023 +0000 hadrian: Build stage 2 cross compilers ./configure produces /hadrian/cfg/system.config.{host,target} Add these to .gitignore - - - - - 7e8abf41 by Alan Zimmerman at 2026-07-09T09:24:12-04:00 EPA: Replace AnnListItem with simply [TrailingAnn] Remove the unnecessary wrapper around a single field. - - - - - 29032f17 by Zubin Duggal at 2026-07-09T09:24:58-04:00 testsuite: Keep real reason for fragile test failures - - - - - c34e03a7 by Zubin Duggal at 2026-07-09T09:24:58-04:00 testsuite: Fall back to the failure reason for empty JUnit bodies - - - - - 409d40f0 by Zubin Duggal at 2026-07-09T09:24:58-04:00 testsuite: Show output diffs in JUnit output Also refactor compare_outputs to return essentially a `Maybe Diff` (`CompareOutput`) instead of a bool, but more pythonic. This allows us to pass the diff through nice. - - - - - 06fee1ab by Zubin Duggal at 2026-07-09T09:24:58-04:00 perf notes: include stat deviation and acceptance window in notes so they show up in gitlab - - - - - 57c0f32c by mangoiv at 2026-07-10T11:08:38-04:00 driver: enable -finter-module-far-jumps by default this fixes a compatibility bug with certain binutils/gcc versions where we were seeing jump offset overflow errors. This commit can probably reverted if we stop supporting the problematic binutils/gcc verions (2.44 and 14.2, respectively) Reolves #26994 - - - - - 4396a6f2 by Andrea Vezzosi at 2026-07-10T11:09:25-04:00 [Fix #27287] preserve ModBreaks in ModIface - - - - - ed261a7e by Cheng Shao at 2026-07-14T17:59:38-04:00 hadrian: fix HLS support This patch fixes hadrian's HLS support so one can rely on HLS when working on the hadrian codebase. Fixes #27480. Not building/linking shared libraries for hadrian is a severely premature optimization; this top-level setting in `cabal.project` only affects home packages while the dependencies in the cabal store are built with vanilla/dynamic anyway, and even adding dynamic builds to home packages would not be costly due to cabal's usage of `-dynamic-too`. - - - - - eee8ec5b by Cheng Shao at 2026-07-14T18:00:20-04:00 compiler: fix miscompiled %load_relaxed, add missing %store_relaxed This patch fixes the %load_relaxed cmm primop compilation logic to correctly use relaxed memory ordering, and adds the missing %store_relaxed primop. Parsing logic of %load/%store with explicit ordering is covered in the AtomicFetch test case. Fixes #27483. Co-authored-by: Codex <codex(a)openai.com> - - - - - 1718230f by Alan Zimmerman at 2026-07-14T18:01:06-04:00 EPA: Keep binds and sigs together in HsValBindsLR We combine them into a single list for GhcPs, wrapped in the ValBind data type, which is the bind equivalent of ValD, having constructors for binds and sigs. This simplifies exact print processing, especially when using it to update the contents of local binds, as we no longer need AnnSortKey BindTag - - - - - 6bd1ad2a by Andreas Klebinger at 2026-07-14T18:01:49-04:00 Bump nofib submodule to account for MonoLocalBinds. New versions of GHC enable MonoLocalBinds by default. This breaks some of the benchmarks. I've fixed this and this bump pulls in that fix. - - - - - 7eb0f1c9 by Cheng Shao at 2026-07-14T18:02:31-04:00 testsuite: fix bytecodeIPE test under +ipe flavours This patch fixes the bytecodeIPE test under +ipe flavours. It used to fail under +ipe because the RTS is built with IPE info, then stg_AP_info in RTS carries IPE info, so whereFrom wouldn't return Nothing. Now the test checks IPE info of a datacon in the ghci-loaded module which is not affected by whether the RTS is built with IPE info or not. Fixes #27498. Co-authored-by: Codex <codex(a)openai.com> - - - - - ef038aae by cydparser at 2026-07-15T04:35:41-04:00 Reduce bytes allocated for `capabilities` in RTS (fixes #27487) In rts/Capability.c, `capabilities` is an array of pointers, but it was allocated as if it were an array of Capability's. - - - - - d377e83e by Cheng Shao at 2026-07-15T04:36:27-04:00 rts: fix missing UNTAG in stg_readTVarIOzh This patch fixes missing UNTAG on the current value closure read from StgTVar. UNTAG is a no-op when it's stg_TREC_HEADER_info which is word aligned; it may be a tagged closure, and reading info table from the tagged address is an unaligned load which may cause issues on platforms with strict alignment requirements. Co-authored-by: Codex <codex(a)openai.com> - - - - - 8ed03842 by Cheng Shao at 2026-07-15T04:36:27-04:00 rts: fix missing UNTAG in stg_control0zh_ll This patch fixes missing UNTAG on the cont closure returned by captureContinuationAndAbort. In case it's not NULL, captureContinuationAndAbort returns a tagged StgContinuation closure, in which case it must be untagged before accessing the apply_mask_frame field. In the past it worked out of luck: when apply_mask_frame was NULL then mask_frame_offset is also 0 so the control flow didn't diverge to a wrong path. Still, this is horribly wrong and will crash once StgContinuation struct is refactored and fields are shuffled around. Co-authored-by: Codex <codex(a)openai.com> - - - - - 5aa7000a by Cheng Shao at 2026-07-15T04:37:08-04:00 compiler: fix redundant AP thunk codegen when not using -ticky-ap-thunk This patch fixes a double negation confusion in !7525 that results in some redundant AP thunk code generation when not using -ticky-ap-thunk. Now, we use `stgToCmmUseStdApThunk` to indicate whether precomputed AP thunks in the RTS should be used, which defaults to `True`, unless `-ticky-ap-thunk` is passed. `-finfo-table-map` now also implies `-ticky-ap-thunk`, since when doing IPE profiling we want the generated AP thunks to be unique. Fixes #27502. ------------------------- Metric Decrease: T3064 ------------------------- Co-authored-by: Codex <codex(a)openai.com> - - - - - d43a7b7a by Brian McKenna at 2026-07-15T20:10:04+02:00 Strip ticks when desugaring bool guards The special `considerAccessible` pattern was broken when compiling with debug info. Compiling with debug info wraps expressions with `SourceNote` ticks, which broke the internals of the `desugarBoolGuard` function. Ticks are now ignored within this function. Fixes #27360 - - - - - ede4b17b by Ben Gamari at 2026-07-15T22:59:53-04:00 base: Display ExceptionContext in WhileHandling's textual description As originally-implemented the implementation for `WhileHandling(displayExceptionAnnotation)` would display the `ExceptionContext` of the exception which it carries (as this was the behavior of `displayException`, in terms of which `displayExceptionAnnotation` was implemented). However, in 284ffab3 the definition of `SomeException(displayException)` was changed to exclude the `ExceptionContext`. This means that `WhileHandling(displayExceptionAnnotation)` fails to describe the provenance of the exception which it captures, greatly limiting its utility. Return the implementation to its originally-specified behavior by implementing `WhileHandling(displayExceptionAnnotation)` in terms of `displayExceptionWithInfo`. Fixes #27456. - - - - - 0f64f348 by Cheng Shao at 2026-07-16T15:41:08+00:00 ci: add missing docker permission workaround in abi-test job - - - - - 660cb239 by Cheng Shao at 2026-07-16T19:37:48+00:00 bindist: Fix make install -j race condition on macos/freebsd This patch fixes make install -j race condition on macos/freebsd. BSD install fails with EEXIST when multiple install processes concurrently create the same prefix directory. So we add an `install_dirs` prerequisite job that sequentially creates the directories for subsequent jobs to work with. Fixes #27499. Co-authored-by: Codex <codex(a)openai.com> - - - - - 08130257 by Cheng Shao at 2026-07-16T19:37:48+00:00 ci: run bindist make install with -j This patch makes the ci scripts run `make install` with `-j` to reduce wall clock time when installing the bindist, see related issue for benchmark numbers. This only affects ghc ci logic, the user-facing default is up to distributors and is still `-j1`. Closes #27029. - - - - - d5ae6906 by Adam Gundry at 2026-07-17T04:57:43-04:00 Mark various language extension flags as deprecated (see #27329) The following language extensions are now deprecated: - AlternativeLayoutRule - AlternativeLayoutRuleTransitional - ParallelArrays - PolymorphicComponents - Rank2Types In addition, the warning `-Walternative-layout-rule-transitional` has been marked as deprecated, as it is emitted only under the deprecated extension `XAlternativeLayoutRuleTransitional`. - - - - - fe3b059c by Andrew Lelechenko at 2026-07-17T04:58:26-04:00 base: re-export GHC.Environment.getFullArgs from System.Environment CLC proposal https://github.com/haskell/core-libraries-committee/issues/431 - - - - - 722236dd by sheaf at 2026-07-18T08:48:31-04:00 Coercion optimisation: avoid double-Sym for InstCo Ticket #27374 pointed out an issue with GHC.Core.Coercion.Opt.optCoercion's handling of InstCo: it contravened (LC2) in Note [The LiftingContext in optCoercion] because it applied the ambient 'sym' to a coercion that was then added to the lifting context substitution. Fixes #27374 Co-authored-by: Simon Jakobi <simon.jakobi(a)gmail.com> - - - - - ff70fc75 by sheaf at 2026-07-18T08:48:31-04:00 Coercion optimisation: avoid exponential behaviour The change to coercion optimisation of 'InstCo' in the previous commit introduces exponential behaviour to the coercion optimiser. To avoid this, this commit provides a way to push in 'Sym' of an already-optimised coercion: GHC.Core.Coercion.Opt.mkDeepSymCo. See Note [Pushing Sym without re-optimising] in GHC.Core.Coercion.Opt. - - - - - dfef27f0 by Duncan Coutts at 2026-07-18T08:49:12-04:00 Move THREADED_RTS-conditional struct members to end of Capability Accessing members of the Capability struct from CMM code rely on accessor macros. (The macros are generated by deriveConstants). These macros have a single definition. This means that the offsets of all struct members must *not* vary based on THREADED_RTS vs !THREADED_RTS. This requires that any struct members that are conditional on THREADED_RTS must occur after the unconditional struct members. Hence we move all the ones that are conditional on THREADED_RTS to the end. Add a deriveConstants entry for the iomgr member of the Capability struct, which was the motivation for this change. Add warning messages to help our future selves. Debugging this took me a couple hours in gdb! - - - - - c254e022 by Duncan Coutts at 2026-07-18T08:49:12-04:00 Make the IOManager API use CapIOManager rather than Capability This makes the API somewhat more self-contained and more consistent. Now the IOManager API and each of the backends takes just the I/O manager structure. Previously we had a bit of a mixture, depending on whether the function needed access to the Capability or just the CapIOManager. We still need access to the cap, so we introduce a back reference to reach the capability, via iomgr->cap. Convert all uses in select and poll backends, but not win32 ones. Convert callers in the scheduler and elsewhere. Also convert the three CMM primops that call IOManager APIs. They just need to use Capability_iomgr(MyCapability()). - - - - - 4f3d8f31 by Duncan Coutts at 2026-07-18T08:49:12-04:00 Split posix/MIO.c out of posix/Signals.c The MIO I/O manager was secretly living inside the Signals file. Now it gets its own file, like any other self-respecting I/O manager. - - - - - 52ce04a9 by Duncan Coutts at 2026-07-18T08:49:12-04:00 Rationalise some scheduler run queue utilities Move them all to the same place in the file. Make some static that were used only internally. Also remove a redundant assignment after calling truncateRunQueue that is already done within truncateRunQueue. - - - - - 75bbdebc by Duncan Coutts at 2026-07-18T08:49:12-04:00 Rename initIOManager{AfterFork} to {re}startIOManager These are more accurate names, since these actions happen after initialisation and are really about starting (or restarting) background threads. - - - - - 724c0517 by Duncan Coutts at 2026-07-18T08:49:12-04:00 Free per-cap I/O managers during shutdown and forkProcess Historically this was not strictly necessary. The select and win32 legacy I/O managers did not maintain any dynamically allocated resources. The new poll one does (an auxillary table), and so this should be freed. After forkProcess, all threads get deleted. This includes threads waiting on I/O or timers. So as of this patch, resetting the I/O manager is just about tidying things up. For example, for the poll I/O manager this will reset the size of the AIOP table (which otherwise grows but never shrinks). In future however the re-initialising will become neeecessary for functionality, since some I/O managers will need to re-initialise wakeup fds that are set CLOEXEC. - - - - - c007d122 by Duncan Coutts at 2026-07-18T08:49:12-04:00 Add a TODO to the MIO I/O manager The direction of travel is to make I/O managers per-capability and have all their state live in the struct CapIOManager. The MIO I/O manager however still has a number of global variables. It's not obvious how handle these globals however. - - - - - b65ab7b3 by Duncan Coutts at 2026-07-18T08:49:12-04:00 Add a FIXME note in the Poll I/O manager - - - - - daf2bd6f by Duncan Coutts at 2026-07-18T08:49:12-04:00 Add missing updateRemembSetPushClosure in poll I/O manager For the non-moving GC. - - - - - e33ca830 by Duncan Coutts at 2026-07-18T08:49:12-04:00 Minor doc improvement to struct StgAsyncIOOp member outcome Mention the enumeration names, as well as their numeric values. The rest of the code uses the enum names. - - - - - 4edd2579 by Duncan Coutts at 2026-07-18T08:49:12-04:00 Minor doc improvements for StgTSOBlockInfo Clarify that certain union members are used only by certain legacy I/O managers. Hopefully we will be able to remove these at some point. - - - - - 536bedbb by Duncan Coutts at 2026-07-18T08:49:12-04:00 Avoid exporting various win32-specific rts symbols The BeginPrivate.h / EndPrivate.h scheme works perfectly well on Windows, but all of the rts/win32/*.h files were not using it. - - - - - 8139b5ac by Duncan Coutts at 2026-07-18T08:49:12-04:00 Remove wakeupIOManager, ioManagerWakeup and setIOManagerWakeupFd We no longer need wakeupIOManager for the threaded RTS case, so we can remove it and the bits only needed to support it. This includes the pipe/eventfd fd shared between the RTS and the in-library I/O manager used for waking up the I/O manager thread. The pipe/eventfd still exists, but it no longer has to be communicated to the RTS, since the RTS no longer needs to use it. So we remove the RTS API export setIOManagerWakeupFd, and remove uses of it within the I/O managers in ghc-internal. - - - - - 74fe7c66 by Duncan Coutts at 2026-07-18T08:49:12-04:00 Add a new interruptIOManager API for the I/O managers It will be used to interrupt awaitCompletedTimeoutsOrIO. Also update the return type and docs for awaitCompletedTimeoutsOrIO to have it return false when it gets interrupted, and have no useful post condition in that case. - - - - - 38792843 by Duncan Coutts at 2026-07-18T08:49:13-04:00 Add interruptIOManager support for select I/O manager Uses the FdWakup mechanism. - - - - - 2f3b00aa by Duncan Coutts at 2026-07-18T08:49:13-04:00 Add interruptIOManager support for poll I/O manager Uses the FdWakup mechanism. A quirk we have to cope with is that we now need to poll one more fd -- the wakeup_fd_r -- but this fd has no corresponding entry in the aiop_table. This is awkward since we have set up our aiop_poll_table to be an auxilliary table with matching indicies. The solution this patch uses (and described in the comments) is to have two tables: struct pollfd *aiop_poll_table, *full_poll_table; and to have the aiop_poll_table alias the tail of the full_poll_table. The head entry in the full_poll_table is the extra fd. So we poll the full_poll_table, while the aiop_poll_table still has matching indicies with the aiop_table. Hurrah for C aliasing rules. - - - - - cee50131 by Duncan Coutts at 2026-07-18T08:49:13-04:00 Add interruptIOManager support for win32 legacy I/O manager And remove unused related helper resetAbandonRequestWait. It is not called because the event is created in auto-reset mode, so never needs to be reset manually. - - - - - cf453143 by Duncan Coutts at 2026-07-18T08:49:13-04:00 Note lack of interruptIOManager support for WinIO I/O manager Though there's a plausible design, we can't sanely test it at the moment due to related WinIO bugs. Filed as issue #27403. - - - - - 1b74a0ad by Duncan Coutts at 2026-07-18T08:49:13-04:00 Be more explicit about enum IOReadOrWrite values, and type within cmm Belt and braces. - - - - - b388d093 by Brian McKenna at 2026-07-18T17:51:50-04:00 Ignore ticks in the pattern-match term oracle The term-oracle in the pattern-match checker is keyed by a canonical form of the scrutinee, computed by `makeDictsCoherent`. That canonical form was tick-sensitive: two occurrences of an otherwise identical expression that happened to carry different ticks were treated as distinct values, breaking long-distance information. This shows up in practice under `-finfo-table-map`, because the desugarer wraps every record-selector use site in a `SourceNote` carrying that site's span. For example: data Box = Box { unBox :: Maybe Int } f b = case unBox b of Nothing -> 0 Just _ -> let Just x = unBox b in x The two `unBox b` expressionss carry different SourceNote spans, the pattern-match checker sees them as different, the long-distance information from the outer `Just _` branch never reaches the let-pattern, and `Just x = unBox b` is wrongly reported as non-exhaustive. We now strip all ticks in `makeDictsCoherent`. This is documented as Wrinkle (UD1) of Note [Unique dictionaries in the TmOracle CoreMap]. Fixes #27314 - - - - - c23e1acb by Mrjtjmn at 2026-07-18T17:52:45-04:00 Add explanations for unsolved Typeable constraints This commit adds explanations for unsolved 'Typeable' constraints. GHC will now provide additional explanations for an unsolved constraint of the form 'Typeable ty', explain why GHC did not solve Typeable constraint. e.g.: - 'ty' is a polymorphic type (e.g. forall a. a -> a) - 'ty' is a qualified type (e.g. Eq Int => Int) - 'ty' is an unboxed sum type - 'ty' is an unreduced type family application - 'ty' whose kind is not typeable Fixes #26532 - - - - - cbef021e by Artem Pelenitsyn at 2026-07-19T07:49:55-04:00 ghc-internal: Lock.hs: fix typo and indentation - - - - - 42918646 by Duncan Coutts at 2026-07-19T07:50:36-04:00 Fix failing test GcStaticPointers for non-moving GC Minor mistake in asserting something before checking for that same thing. Specifically, Bdescr asserts HEAP_ALLOCED_GC, but Bdescr was being used prior to a guard that checks HEAP_ALLOCED_GC. The solution is just to move the use of Bdescr after the guard. Thanks to Simon Jakobi for identifying the problem. - - - - - c2f6dcd4 by Sasha Bogicevic at 2026-07-20T10:31:56+02:00 Improve error messages for invalid record wildcards Record wildcard hints are now shown in more contexts and include constructor arity; matching with `..` on a fieldless constructor now produces a dedicated error message. Fixes #21101 - - - - - 4c02e76b by Duncan Coutts at 2026-07-21T10:37:21-04:00 Mark test T27105 as fragile, citing issue #27522 Scheduler fairness is fine, except when it isn't. And it isn't on CI machines surprisingly often! See the issue for details. - - - - - 43dd2b15 by Recursion Ninja at 2026-07-21T17:09:53-04:00 Resolving many TTG related orphan type-class instances This is part a technical debt removal effort made possible now that separating out the AST via TTG has come to a close. As the AST in 'L.H.S' has been incrementally separated from the GHC internals, there are many accumulated orphan instance of 'Binary', 'NFData', 'Outputable', and 'Uniquable'. The orphan instance of data-types from within 'L.H.S' have had their orphan instances moved to either: 1. The module which defines the data-type 2. The module which defines the type-class; i.e. moving an orphan 'Binary' instance to 'GHC.Utils.Binary' Orphan instances resolved (37): | Data-type | Resolved instance(s) | Former orphan module(s) | | -------------------- | -------------------------- | ------------------------- | | Role | Binary, NFData, Outputable | GHC.Core.Coercion.Axiom | | SrcStrictness | Binary, NFData, Outputable | GHC.Core.DataCon | | SrcUnpackedness | Binary, NFData, Outputable | GHC.Core.DataCon | | Fixity | Binary, Outputable | GHC.Hs.Basic | | FixityDirection | Binary, Outputable | GHC.Hs.Basic | | LexicalFixity | Outputable | GHC.Hs.Basic | | CCallTarget | NFData | GHC.Hs.Decls.Foreign | | CType | NFData | GHC.Hs.Decls.Foreign | | Header | NFData | GHC.Hs.Decls.Foreign | | OverlapMode | Binary, NFData | GHC.Hs.Decls.Overlap | | WithHsDocIdentifiers | NFData, Outputable | GHC.Hs.Doc | | HsDocString | NFData | GHC.Hs.DocString | | HsDocStringChunk | Binary, Outputable | GHC.Hs.DocString | | HsDocStringDecorator | Binary, Outputable | GHC.Hs.DocString | | NamespaceSpecifier | Outputable | GHC.Hs.ImpExp | | ForAllTyFlag | Binary, NFData, Outputable | GHC.Hs.Specificity | | Specificity | Binary, NFData | GHC.Hs.Specificity | | PromotionFlag | Binary, Outputable | GHC.Types.Basic | | FieldLabelString | Outputable, Uniquable | GHC.Types.FieldLabel | | InlinePragma | Binary | GHC.Types.InlinePragma | ------------------------- Metric Decrease: hard_hole_fits ------------------------- Closes #21262, #27469 - - - - - ab9ab895 by Cheng Shao at 2026-07-21T17:10:53-04:00 rts: always use StgInt to represent cost center id Currently cost center id is modeled as `Int` and it should be `StgInt` uniformly in the RTS, hence this patch. Fixes #27524. - - - - - 94d8f83b by Cheng Shao at 2026-07-22T11:30:40-04:00 hadrian: clean up stale cabal package flags in the tree This patch cleans up stale cabal package flags in the tree and related hadrian/autoconf logic. Closes #27474. Co-authored-by: Codex <codex(a)openai.com> - - - - - 0bf1d8c9 by Sasha Bogicevic at 2026-07-22T11:31:21-04:00 parser: don't suggest ImportQualifiedPost when it is already enabled -Wprepositive-qualified-module unconditionally attached a hint to enable ImportQualifiedPost, even when the extension was already on (as it is by default under GHC2021). Record the extension's state in the PsWarnImportPreQualified diagnostic and drop the hint when it is already enabled. Fixes #27380 - - - - - 700a1dd1 by Simon Jakobi at 2026-07-23T11:21:20-04:00 ci: Reduce lint job setup costs Avoid fetching unnecessary history and submodules for lightweight lint jobs. Run changelog validation without Hadrian. Because the lint-author job is now based on the .lint template directly, we enhance it to allow Git to read from the runner-owned checkouts, In the previously used .lint-params template, this permissions issue was addressed via `chown`. Closes #27521. Assisted-by: gpt-5.6-sol via Codex CLI - - - - - 26a44fb0 by ARATA Mizuki at 2026-07-23T11:22:10-04:00 testsuite: Fix memory issues of doublex2_* and simd010 doublex2_* had reads from uninitialized memory. simd010 had out-of-bounds array access. Fixes #27544 - - - - - 4d798b17 by Duncan Coutts at 2026-07-23T17:26:18-04:00 Eliminate STM_AWOKEN It was used as nullary closure for the block_info.closure in the case of a thread being awoken after an STM transaction. However, while it was written, it was never read, so contributed nothing to the behaviour. Furthermore, in the only place it was set (in tryWakeupThread) the why_blocked was immediately overwritten by the NotBlocked status, and the block_info was updated accordingly (by appendToRunQueue). So it didn't even serve a purpose of clarifying an intermediate state, there really was no such intermediate state. Cleaning this up will allow the BlockedOnSTM case to follow the same pattern as the other why_blocked cases that do not use the block_info, and in turn this reduces the number of different categories. - - - - - e1cece79 by Duncan Coutts at 2026-07-23T17:26:18-04:00 Document that eventlog thread stop code ThreadBlocked is no longer used It has not been used since GHC 7.0.x (2011). In 7.2 all the BlockedOn* codes were added, and these were and are used instead of ThreadBlocked. - - - - - 795db115 by Duncan Coutts at 2026-07-23T17:26:18-04:00 Add a proper mapping to eventlog external thread stop status That is the mapping from rts-internal codes, to the coes used in the status field in the eventlog EVENT_STOP_THREAD event. See issue #9003 for what goes wrong when we mess this up. In that ticket, people note that we should really not require the internal tso->why_blocked codes to leak into the external eventlog thread stop codes. The same principle applies to the StgThreadReturnCode. This change properly separates them, and explicitly maps between them using a pair of (compact, constant) tables. These tables are pretty small (with no alignment constraints) and will soon shrink so it seems a sensible tradeoff. We also introduce and use proper EVENT_STOP_THREAD constants in the event log format header. Previously there was not specification in the code for these (only in the docs): the values were encoded into the conversion code. This will allow us to renumber the internal why_blockd codes without breaking the eventlog output. - - - - - 6f1c8efa by Duncan Coutts at 2026-07-23T17:26:18-04:00 Remove unused tso->block_info.wakeup member Presumably it was used once, but not now. - - - - - 740b88a9 by Duncan Coutts at 2026-07-23T17:26:18-04:00 Document StgTSOBlockInfo to say what cases use what members In principle, tso->why_blocked is the tag for the StgTSOBlockInfo union, so we should be able to say for each union member the why_blocked cases that use that member. - - - - - 5b92eae2 by Duncan Coutts at 2026-07-23T17:26:18-04:00 Add a tso->block_info.mvar member and use it in preference to the generic block_info.closure union member, with casts. The plan is that when we know what case we're in (via tso->why_blocked) then we can always access the correct union member, and so we will only need to access block_info.closure for generic cases where we don't know or don't care. - - - - - d931715f by Duncan Coutts at 2026-07-23T17:26:18-04:00 Add a tso->block_info.unused member and use it in preference to the generic block_info.closure union member, with casts. The plan is that when we know what case we're in (via tso->why_blocked) then we can always access the correct union member, and so we will only need to access block_info.closure for generic cases where we don't know or don't care. - - - - - 47e28ebb by Duncan Coutts at 2026-07-23T17:26:18-04:00 Avoid storing to tso->block_info.closure In one case we can use a specific union member (.prev) instead. In several cases the stores were in fact redundant because of subsequent overwrites. In scavengeTSO we replace setting tso->block_info.closure to a valid closure, with an assertion that the block_info.unused is already set to END_TSO_QUEUE which is a valid (static) closure. - - - - - 96e4749d by Duncan Coutts at 2026-07-23T17:26:18-04:00 Renumber the tso->why_blocked constants We can do this now because we have separated the internal values from the external ones used in the eventlog. This lets us put them back into a deliberate order and consolodate some gaps. More importantly, it is a prepation for a slightly more sophisticated encoding. - - - - - 8f62661c by Duncan Coutts at 2026-07-23T17:26:18-04:00 Define constants for the existing stg_threadStatuszh return codes The stg_threadStatuszh reuses the internal tso->why_blocked codes but also extends them with a couple previously magic values. This is awkward since we need to know what those magic values are so we don't accidentally use those values to mean something else. By pulling a definition up to where the why_blocked codes are defined we will be able to avoid mistakenly assining those codes some meaning (or just changing the BlockedThreadComplete, BlockedThreadKilled code if necessary). - - - - - 42c69ae2 by Duncan Coutts at 2026-07-23T17:26:18-04:00 Extend the tso->why_blocked encoding to indicate block_info closures We use some bit tricks to cheaply and generically test if a tso->why_blocked tag implies that the corresponding tso->block_info will contain a non-trivial valid closure (i.e. not just block_info.unused set to END_TSO_QUEUE). In particular we arrange for most why_blocked values to naturally have a distinguishing bit, but for the BlockedOn{Read,Write,Delay} cases, they can come in either non-closure or closure forms. We allow an additional bit to distinguish these cases. The non-closure forms are only from legacy I/O managers: select and win32-legacy. So this extra bit mechanism will be able to be retired once the legacy I/O managers are themselves retired. This means in a few places we need to untag the why_blocked value before inspecting it, but in most places we do not. - - - - - 7c64632b by Duncan Coutts at 2026-07-23T17:26:18-04:00 Use BlockInfoForceNonClosure in the select I/O manager - - - - - 8fd7104a by Duncan Coutts at 2026-07-23T17:26:18-04:00 Use BlockInfoForceNonClosure in the win32-legacy I/O manager for the BlockedOn{Read,Write} since these use the non-heap allocated StgAsyncIOResult. - - - - - e0da603b by Duncan Coutts at 2026-07-23T17:26:18-04:00 Enforce the why_blocked and block_info rules in checkTSO We now check the cases wher IsBlockInfoClosure should hold, the cases that are supposed to use block_info.unused == END_TSO_QUEUE, and which cases are allowed to use BlockInfoForceNonClosure. This partially enforces the use of why_blocked as a tag for the block_info union. We could be stricter and check for the correct expected info table for the closure cases. - - - - - 1dd0f381 by Duncan Coutts at 2026-07-23T17:26:18-04:00 Use IsBlockInfoClosure to simplify several tests In GC and generic traversal we need to know if we should look at the block_info.closure or not. Now we can do just that using a cheap bit test on the why_blocked tag. This fixes issue 26717, where the problem was that some GC modes did not know when to look at block_info.closure, because the poll I/O manager uses a closure for BlockedOn{Read,Write} while the select I/O manager uses a non-closure. Now this information is in the why_blocked tag itself. - - - - - 7a00ffbc by Duncan Coutts at 2026-07-23T17:26:18-04:00 Remove the now-unused scavengeTSOIOManager The GC no longer has to delegate to the I/O manager, since it can use IsBlockInfoClosure to decide things itself. - - - - - 522a481f by Duncan Coutts at 2026-07-23T17:26:18-04:00 Remove duplicate assertion - - - - - 0874d965 by Duncan Coutts at 2026-07-23T17:26:18-04:00 Follow atomic access rules more consistently for tso->why_blocked The rule is this: store block_info *before* why_blocked store why_blocked using store release load why_blocked using load acquire load block_info *after* why_blocked This is a an atomic store release / load acquire pair and (if the reads are in a separate thread to the writes, and the read receives the value stored) then this guarantees a full "happens before" relationship of these stores and loads. In some cases, we do not need a full load acquire, because we don't read the block_info at all and so do not need any ordering. In this case we just need an atomic relaxed load. This was being followed in most places, but not all. If there's good reason in any case that we don't need atomic access, then we should document that in a comment. In the absence of that I think it's easier to follow the rule everywhere. - - - - - 8f0bdbe1 by Duncan Coutts at 2026-07-23T17:26:19-04:00 Add a changelog entry - - - - - 4fdfe757 by Alan Zimmerman at 2026-07-23T17:27:06-04:00 EPA: Keep decls together in ClassDecl Similar to 1718230f4d3d19d8c49c0e5d496cb0fb6f399528 for HsValBindsLR, this commit updates ClassDecl so that it no longer splits out the assorted `LHsDecl GhcPs` until the renamer. It does this by inserting a type family (separate from the classic TTG one) for this. So data TyClDecl ... | ClassDecl { ... tcdDecls :: XClassDecls pass with type instance XClassDecls GhcPs = [LHsDecl GhcPs] type instance XClassDecls GhcRn = ClassDeclX GhcRn type instance XClassDecls GhcTc = ClassDeclX GhcTc data ClassDeclX pass = ClassDeclX { tcdSigs :: [LSig pass], -- ^ Methods' signatures tcdMeths :: LHsBinds pass, -- ^ Default methods tcdATs :: [LFamilyDecl pass], -- ^ Associated types; tcdATDefs :: [LTyFamDefltDecl pass], -- ^ Associated type defaults tcdDocs :: [LDocDecl pass] -- ^ Haddock docs } - - - - - f586c885 by Simon Jakobi at 2026-07-24T18:05:00-04:00 ci: Use shallow submodule clones by default Limit submodule clones to depth one to reduce CI checkout costs. Keep fetching full submodule history for the submodule lint jobs, which inspect commits across a range. Assisted-by: gpt-5.6-sol via Codex CLI - - - - - 306120d2 by Duncan Coutts at 2026-07-24T18:05:43-04:00 Fix flaky test T3994 on FreeBSD On current FreeBSD versions, calling getpgid on a zombie process fails. In T3994, if we're really unlucky with delays and scheduling then we can end up in exactly that situation. Just catch that specific exception and ignore it. It's rare, and not our fault. - - - - - 7b116a0b by Cheng Shao at 2026-07-24T18:06:24-04:00 ci: add missing workaround for docker permissions in lint jobs Some lint jobs use ci-images with default user `ghc`, and the gitlab ci docker executor requires the `sudo chown` workaround to fix workspace directory permission issue. This patch adds the missing workarounds for the lint jobs. Fixes #27554. Co-authored-by: Codex <codex(a)openai.com> - - - - - 815149f3 by Andrzej Rybczak at 2026-07-25T15:06:43+00:00 Add -Wdefaulted-callstack Adds a new warning, -Wdefaulted-callstack, which warns when an implicit CallStack parameter is defaulted to the empty stack. In particular, this includes call sites where a function with a HasCallStack constraint is called from a definition that does *not* provide one. At such call sites the call stack is cut off and does not include the enclosing definition's callers, which can be a source of surprise if the user wants complete call stacks. Closes #27077. - - - - - f6f2343f by Zubin Duggal at 2026-07-25T17:40:51-04:00 UniqueDFM: alter should preserve insertion order Before it always inserting new elements at the end. This is problematic because instances get inserted into the map with `alterF`, which can change ordering of how instances are printed with `:info` depending on the order in which we consult interfaces I expect `alter id k = id` and `alter (fmap f) k = adjust f k`. Moving keys to the end breaks that (`adjust` already preserves position). Fixes #27532 - - - - - 5d0ab71a by fendor at 2026-07-27T17:31:05-04:00 Introduce global unit database cache As a first step for better sharing of `UnitInfo` across `UnitEnv`, we introduce a new datatype called `ExternalUnitDatabases`. It primarily serves as an in-memory representation of *all* `UnitDatabase`s across `UnitEnv`. This means, if multiple `HomeUnitEnv`s depend on the same database, one way or another, we make sure that we don't parse from disk every time. Instead, we store the in-memory representation in `ExternalUnitDatabases`. `ExternalUnitDatabaseCache` is the equivalent of `ExternalUnitState` in the `UnitEnv`. It is a mutable variable wrapping `ExternalUnitDatabases`. The mutable `ExternalUnitDatabaseCache` is used in `initUnits` to make sure we don't parse the same unit database multiple times. Almost by accident, we change the semantics of `initUnits` to honour modifications to `packageDBFlags`. The inability to change `packageDBFlags` while also reusing the already parsed `UnitDatabase`s was reported in #26423 as a bug. Hence, we think this behaviour change is warranted and acceptable, especially since it comes with a breaking change to the `initUnits` API. Add regression test for #26423 Closes #26423 - - - - - 6cce494a by fendor at 2026-07-27T17:31:05-04:00 Introduce UnitIndex for global external unit caching `UnitInfo`s have been observed to cause a lot of memory usage in #27500. Especially with multiple home units, as the same (external) units are processed from scratch, even though most of the time we end up with exactly the same `UnitInfo`. We introduce a `UnitEnv` global cache that allows us to store external unit information that is used across all `HomeUnitEnv`s. The most important change in this commit is the introduction of the `UnitIndex`. It stores a global mapping of `UnitId` -> `UnitInfo`, and `initUnits` always uses the cached `UnitInfo` entry to populate each `HomeUnitEnv`'s `UnitState`. This allows us to ensure the following property: > Each `UnitInfo` should be alive exactly once in GHC. All `UnitState`s should reference 'UnitInfo's stored in the 'UnitIndex'. This ensured by calling 'initUnits' with the 'UnitIndex'. In addition, the `ExternalUnitDatabases` may also hold a reference to each on-disk representation of `UnitInfo`. This means, we impose an hard upper bound on the number of `UnitInfo`s alive in the GHC session: > The number of alive `UnitInfo`s closure objects must be the > sum of all loaded unit database times two. We add performance regression tests that make sure the number of live `UnitInfo` cannot exceed this threshold. Closes #27500 ------------------------- Metric Decrease: MultiComponentModules MultiComponentModulesRecomp MultiComponentModulesRecomp100 mhu-perf LinkableUsage02 ------------------------- These metrics increases are especially notable, as we are not even sharing anything big but merely the global package database with 50 entries. It shows how careful sharing of `UnitInfo` can improve memory usage. We expect this to be much more notable when the whole cabal package database is shared across multiple home units. `LinkableUsage02` metric decreases on unreg and i386 platform, only. --- Technical details To share the `UnitInfo`s correctly, it is important that we extract the `WireMap` into the `UnitIndex`. At the moment of writing, `WireMap` must be globally the same for all `HomeUnitEnv`s. This is important, as we could otherwise not cache the "fully-resolved" `UnitInfo`, as we don't change the `UnitId` or `unitAbiHash` when resolving wired-in units. Thus, there could be ambiguities, when the `WireMap` is not the same for all `UnitState`s across the `UnitEnv`. We consider a `UnitInfo` fully-resolved, if wired-in units have been updated, the `UnitInfo` has been validated and variables in the unit config, such as `${pkgroot}` have been resolved. Updating the wired-in units requires the `WireMap` to be globally the same. - - - - - f8e3bee9 by Zubin Duggal at 2026-07-27T17:31:49-04:00 testsuite: skip runtime stats tests on debugged compilers Debugged flavours build the boot libraries without optimisation, so the runtime numbers do not match the baselines. - - - - - 1e326770 by Zubin Duggal at 2026-07-27T17:31:50-04:00 testsuite: mark #20706 tests fragile rather than broken Whether the static linux linker issues manifest depends on the host toolchain. - - - - - c0b13cbe by Zubin Duggal at 2026-07-27T17:31:50-04:00 testsuite: exclude libnuma from mostly-static It needs static system libraries (libnuma.a) that many platforms do not ship. Fixes #26914 - - - - - bee1913d by Alan Zimmerman at 2026-07-28T16:42:29-04:00 EPA: ClsInstDecl with decls as [LHsDecl GhcPs] in GhcPs Similar to 4fdfe75731e01dad7d7fa474c2703d0d3965afb1, this commit changes the as-parsed representation of class instance declarations to [LHsDecl GhcPs], and only separates them by type from the renamer onward. This also allows us to remove all the AnnSortKey machinery for exact printing, as it is now no longer needed. - - - - - 72c55eee by Cheng Shao at 2026-07-28T16:43:11-04:00 hadrian: implement and use writeFileAtomic to fix race condition This patch implements `writeFileAtomic` in hadrian and change all invocations of shake non-atomic `writeFile'` to use `writeFileAtomic`, to avoid multiple hadrian concurrent invocations overwriting the same in-tree generated file not in the build root directory. Fixes #27536. Additional notes: - `writeFileChanged`/`writeFileChangedBS` cannot be made atomic since it involves reading the file's older version, so their uses are left alone. It doesn't affect #27536 given their outputs are contained in the build root directory. - It's possible to shrink this patch by only making writes outside the build root directory atomic. But I think it's not worth the effort for fine grained distinction here, and atomic writes within the build root directory should also improve robustness of a hadrian build. - In the longer term we do want to make a ghc build only generate files within the build root directory, though that's a lot of work and outside the scope of this particular bugfix. Co-authored-by: Codex <codex(a)openai.com> - - - - - 46d4f963 by Sylvain Henry at 2026-07-29T06:38:40-04:00 RTS: correctly mark slop bytes when shrinking large arrays (#19048) Correctly mark slop bytes even when profiling is off so that heap census doesn't traverse garbage-collected closures. - - - - - 4762a8bf by Simon Jakobi at 2026-07-29T06:39:23-04:00 Add -XLazyFieldAnnotations (GHC proposal 752) Unbundle the prefix `~` lazy field annotation syntax from StrictData. The new LazyFieldAnnotations extension controls whether `~` is accepted on constructor fields. StrictData (and Strict, transitively) imply the new extension. See https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0752-l…. Closes #24455. Assisted-by: Claude Opus 4.8 - - - - - 0b6dcc84 by Simon Jakobi at 2026-07-29T06:40:04-04:00 testsuite: Relax T24471 residency tolerance T24471 peak residency fluctuates enough on i386 to cause spurious failures. Use the standard residency tolerance while retaining the existing allocation threshold. See https://gitlab.haskell.org/ghc/ghc/-/work_items/24471#note_682303. Assisted-by: gpt-5.6-sol via Codex CLI - - - - - 90e95b34 by Cheng Shao at 2026-07-29T06:40:45-04:00 compiler: fix missing top-level procedure labels in cmm dumps This patch fixes missing top-level procedure labels in some intermediate Cmm pass dumps. Fixes #27553. Co-authored-by: Codex <codex(a)openai.com> - - - - - 360a5946 by sheaf at 2026-07-29T06:41:35-04:00 Add some type-family-heavy performance tests FamAppCachePerf stress-tests the performance of lookups in the type family application cache. T27336 is a minimisation extracted from the reported reproducer. SimplCastPerf is a measure of coercion growth due to the simplifier calling mkTransCo without re-optimising the result. - - - - - 3ec9e2b9 by Mike Pilgrem at 2026-07-31T08:21:33-04:00 GHC Guide: Improve docs on response files - - - - - e5b2a1f7 by sheaf at 2026-07-31T08:22:23-04:00 Disable Core Lint for TcPlugin_RewritePerf This is a compiler performance test, but the test source hard-coded -dcore-lint, defeating the measurement. ------------------------- Metric Decrease: TcPlugin_RewritePerf ------------------------- - - - - - 85b10c00 by Alan Zimmerman at 2026-07-31T22:09:47+01:00 EPA: Remove LocatedP from OverlapMode We have type LocatedP = GenLocated SrcSpanAnnP type SrcSpanAnnP = EpAnn AnnPragma As the first step in removing this in favour of LocatedA which only captures location, comments and trailing annotations, we remove it from OverlapMode We do this by moving the AnnPragma into the TTG extension point instead. - - - - - c9a34a00 by Viktor Dukhovni at 2026-08-02T04:34:17-04:00 Fix note typo - - - - - 4f2a21f7 by Andreas Klebinger at 2026-08-02T22:46:46-04:00 Apply oneShot Monad trick to STG LintM - - - - - 21e4b89d by Andreas Klebinger at 2026-08-02T22:46:46-04:00 stgLint: Use a single reader env for read only arguments. - - - - - d415f38a by Alan Zimmerman at 2026-08-02T22:47:27-04:00 EPA: Remove LocatedP from CType The next step of removing use of LocatedP by moving the AnnPragma for CType into its TTG extension point instead. - - - - - 54ff5697 by Ben Gamari at 2026-08-04T13:01:25+05:30 base: Don't drop exception context in SomeException(toException) For reasons that are lost to time, the implementation of [CLC #200] that was merged inappropriately dropped `ExceptionContext` in the `toException` implementation given to `SomeException`. Fix this infelicity. [CLC #200]: https://github.com/haskell/core-libraries-committee/issues/200 - - - - - 885 changed files: - .gitignore - .gitlab-ci.yml - .gitlab/ci.sh - .gitlab/generate-ci/gen_ci.hs - .gitlab/jobs.yaml - .gitlab/merge_request_templates/Default.md - .gitlab/rel_eng/mk-ghcup-metadata/mk_ghcup_metadata.py - .gitlab/test-metrics.sh - + changelog.d/21101 - + changelog.d/26616 - + changelog.d/27380 - + changelog.d/27532 - + changelog.d/AbstractQ - + changelog.d/T21176 - + changelog.d/T21628 - + changelog.d/T26423 - + changelog.d/T26532 - + changelog.d/T26716 - + changelog.d/T27123.md - + changelog.d/T27314.md - + changelog.d/T27329 - + changelog.d/T27360 - + changelog.d/T27374 - + changelog.d/T27386 - + changelog.d/T27455 - + changelog.d/T27456 - + changelog.d/add_can_drop_to_occurence_analyser - changelog.d/config - + changelog.d/fix-absent-dict-projection - + changelog.d/fix-cmm-atomic-load-store - + changelog.d/fix-cmm-dump-labels - + changelog.d/fix-compacting-gc-ap-27434 - + changelog.d/fix-heap-census-large-arrays-19048 - + changelog.d/fix-layout-stack-fcall - + changelog.d/fix-make-install-j - + changelog.d/fix-peekitbl-no-tntc - + changelog.d/fix-unreg - + changelog.d/fix-use-std-ap-thunk - + changelog.d/generically-mconcat - + changelog.d/inter-module-far-jumps-aarch64-default - + changelog.d/interactive-error-hints - + changelog.d/lazy-field-annotations - + changelog.d/pp-set-ghc-version - + changelog.d/reexported-module-errors - + changelog.d/remove-ddump-json-flag - changelog.d/semaphore-v2 - + changelog.d/stable-core-dump-order-27296 - + changelog.d/stage2-cross-compilers - + changelog.d/unit-index - + changelog.d/unused-type - + changelog.d/warn-defaulted-callstack - compiler/GHC.hs - compiler/GHC/Builtin/Names.hs - compiler/GHC/Builtin/Types.hs - compiler/GHC/Builtin/Types/Prim.hs - compiler/GHC/Builtin/Utils.hs - compiler/GHC/ByteCode/Breakpoints.hs - compiler/GHC/ByteCode/Types.hs - compiler/GHC/Cmm/CLabel.hs - compiler/GHC/Cmm/LayoutStack.hs - compiler/GHC/Cmm/Parser.y - compiler/GHC/Cmm/Pipeline.hs - 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utils/haddock/haddock-api/src/Haddock/Interface/Create.hs - utils/haddock/haddock-api/src/Haddock/Interface/Json.hs - utils/haddock/haddock-api/src/Haddock/Interface/LexParseRn.hs - utils/haddock/haddock-api/src/Haddock/Interface/ParseModuleHeader.hs - utils/haddock/haddock-api/src/Haddock/Interface/Rename.hs - utils/haddock/haddock-api/src/Haddock/Interface/RenameType.hs - utils/haddock/haddock-api/src/Haddock/InterfaceFile.hs - utils/haddock/haddock-api/src/Haddock/Options.hs - utils/haddock/haddock-api/src/Haddock/Parser.hs - utils/haddock/haddock-api/src/Haddock/Types.hs - utils/haddock/haddock-api/src/Haddock/Utils/Json.hs - utils/haddock/haddock-api/src/Haddock/Utils/Json/Parser.hs - utils/haddock/haddock-api/src/Haddock/Utils/Json/Types.hs - utils/haddock/haddock-library/src/Documentation/Haddock/Doc.hs - utils/haddock/haddock-library/src/Documentation/Haddock/Markup.hs - utils/haddock/haddock-library/src/Documentation/Haddock/Parser.hs - utils/haddock/haddock-library/src/Documentation/Haddock/Parser/Util.hs - utils/haddock/haddock-library/src/Documentation/Haddock/Types.hs - utils/haddock/haddock-library/test/Documentation/Haddock/ParserSpec.hs - utils/haddock/haddock-test/src/Test/Haddock/Config.hs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/a3a29d44862d0a423fd5277b9f69ba… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/a3a29d44862d0a423fd5277b9f69ba… You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc][wip/sjakobi/nonmoving-gc-test-fixes] 2 commits: rts/js: Implement eq_thread
by Simon Jakobi (＠sjakobi) 04 Aug '26

04 Aug '26

Simon Jakobi pushed to branch wip/sjakobi/nonmoving-gc-test-fixes at Glasgow Haskell Compiler / GHC Commits: 174ac772 by Simon Jakobi at 2026-08-04T07:46:35+02:00 rts/js: Implement eq_thread Since d1f3c63701, Eq ThreadId is implemented via the RTS function eq_thread, but the JS RTS never provided it, so comparing ThreadIds for equality on the JS backend crashed with ReferenceError: h$eq_thread is not defined Like the C implementation, h$eq_thread uses pointer equality: The JS RTS has exactly one thread object per thread. This function is exercised by the reshaped listThreads1 test. Assisted-by: Claude Fable 5 - - - - - a8b65750 by Simon Jakobi at 2026-08-04T07:46:41+02:00 testsuite: Make listThreads1 insensitive to the RTS's own threads listThreads1 expected `listThreads` to return exactly [ThreadId 1]. That holds only under a non-threaded RTS. Under a threaded RTS however there are more threads present, so we change the test to simply check that `myThreadId` is present in the list. Assisted-by: Claude Opus 5 - - - - - 3 changed files: - libraries/base/tests/listThreads1.hs - libraries/base/tests/listThreads1.stdout - rts/js/thread.js Changes: ===================================== libraries/base/tests/listThreads1.hs ===================================== @@ -2,5 +2,10 @@ module Main where import GHC.Conc.Sync +-- Regression test for the JS backend's ListThreadsOp, which used to omit the +-- running thread. Whatever other threads the RTS has is irrelevant here. main :: IO () -main = listThreads >>= print +main = do + tid <- myThreadId + ts <- listThreads + print (tid `elem` ts) ===================================== libraries/base/tests/listThreads1.stdout ===================================== @@ -1 +1 @@ -[ThreadId 1] +True ===================================== rts/js/thread.js ===================================== @@ -110,6 +110,10 @@ function h$rts_getThreadId(t) { // returns a CULLong RETURN_UBX_TUP2((t.tid / Math.pow(2,32))>>>0, (t.tid & 0xFFFFFFFF)>>>0); } +function h$eq_thread(t1,t2) { + return t1 === t2 ? 1 : 0; +} + function h$cmp_thread(t1,t2) { if(t1.tid < t2.tid) return -1; if(t1.tid > t2.tid) return 1; View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/1ac1d5549cd160d095e42d3b42fdac… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/1ac1d5549cd160d095e42d3b42fdac… You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc][wip/marge_bot_batch_merge_job] 8 commits: testsuite: Don't crash on non-UTF-8 test output
by Marge Bot (＠marge-bot) 04 Aug '26

04 Aug '26

Marge Bot pushed to branch wip/marge_bot_batch_merge_job at Glasgow Haskell Compiler / GHC Commits: 538e6cc2 by Simon Jakobi at 2026-08-03T21:36:45-04:00 testsuite: Don't crash on non-UTF-8 test output read_stdout, read_stderr_for, read_comp_stderr and read_diff decoded strictly (the first three with UTF-8, read_diff with the locale encoding), so a test emitting invalid UTF-8 (binary output, or a crash truncating a multi-byte character) raised UnicodeDecodeError and was reported as a framework failure instead of its actual result. Decode with errors='replace', like read_no_crs and safe_print. Assisted-by: Claude Fable 5 - - - - - 202ae00e by Simon Jakobi at 2026-08-03T21:36:45-04:00 testsuite: Colorize the test summary, also in CI The summary headings were plain, and SUMMARY was colored unconditionally, so the escapes also ended up in the file written by --summary-file. Color is now decided per output sink via term_color.colored_if; see the comments in term_color. CI logs are not a tty, but GitLab's log viewer renders ANSI colors, so add --force-colors and pass it in .gitlab/ci.sh. Assisted-by: Claude Opus 5 - - - - - 9250a22a by Simon Jakobi at 2026-08-03T21:36:46-04:00 testsuite: Repeat unexpected failure output in the summary Finding out why a test failed meant scrolling back through a possibly very long log to the point where the test ran. The summary now repeats the captured output of unexpected failures, before the statistics, so the most interesting part is at the end of the log (#16720). Output mismatches report their diff instead of the mismatching stream (see Note [Redundant output in test results]). The repeated output is bounded per stream, and skipped altogether beyond MAX_SUMMARY_OUTPUT_TESTS failure blocks. Tests failing identically in several ways share one block. Test results now report a source-relative directory, stable regardless of where the run was started from. Assisted-by: Claude Fable 5 - - - - - 99fa1402 by Simon Jakobi at 2026-08-03T21:36:47-04:00 testsuite: Expect length001 failure in nonmoving_thr_sanity length001 relies on an optimization rule to avoid excessive stack use. The nonmoving_thr_sanity way does not enable optimization, so classify its stack overflow as an expected failure, as is already done for the other unoptimized nonmoving ways. Assisted-by: gpt-5.6-sol via Codex CLI - - - - - 6680e449 by Simon Jakobi at 2026-08-03T21:36:47-04:00 testsuite: Omit T22859 in nonmoving threaded ways T22859 checks allocation-limit handlers with output that depends on precise allocation behaviour. The nonmoving threaded ways change where these limits are reached, just as the already-omitted LLVM ways do. Omit these ways instead of treating their incidental output differences as test failures. Assisted-by: gpt-5.6-sol via Codex CLI - - - - - 5e35c797 by Simon Jakobi at 2026-08-03T21:36:47-04:00 testsuite: Make listThreads1 insensitive to the RTS's own threads listThreads1 expected `listThreads` to return exactly [ThreadId 1]. That holds only under a non-threaded RTS. Under a threaded RTS however there are more threads present, so we change the test to simply check that `myThreadId` is present in the list. Assisted-by: Claude Opus 5 - - - - - fa59706c by Vladislav Zavialov at 2026-08-03T21:36:48-04:00 Discard type arguments in tcPatToExpr (#27440, #27583) The builder expression of an implicitly bidirectional pattern synonym must not mention types written in the RHS: * Invisible type arguments led to a panic (#27440) * Required type arguments failed with out-of-scope variables (#27583) Both are now discarded, following the precedent established by pattern signatures (#9867). Discarding type arguments takes some care: a type pattern cannot be told from a value pattern by syntax alone, as the `type` keyword may be omitted. Consider: data T a b c where MkT :: forall a. forall b c -> a -> T a b c pattern P :: x -> T x y z pattern P x = MkT @a (type b) c x In P's right-hand side, `@a` and `type b` are clearly type arguments, but what about `c` and `x`? We can only tell by matching the patterns against MkT's type. So tcPatToExpr now runs in TcM and matches the arguments against the constructor's TyVarBinders using zipPatsBndrs, which is made public for this purpose. The resulting builder is $bP x = MkT _ _ x. See Note [Discarding types in the builder expression]. Test cases: T27440a T27440b T27440c T27440d T27440e T27583a T27583b T27583c T27583d T27583e T27583f T27583g Assisted-by: Claude Opus 5 - - - - - 2791ab7a by Vladislav Zavialov at 2026-08-03T21:36:48-04:00 Test case for #20902 Starting with GHC 9.14.1 (the first major release to include 51e3ec83), and from point releases GHC 9.10.2 and GHC 9.12.3 (backports cc4470be68 and b30f25591e), all examples in this ticket are handled as expected. - - - - - 33 changed files: - .gitlab/ci.sh - + changelog.d/T27440 - + changelog.d/T27583 - compiler/GHC/Tc/Gen/Pat.hs - compiler/GHC/Tc/TyCl/PatSyn.hs - libraries/base/tests/all.T - libraries/base/tests/listThreads1.hs - libraries/base/tests/listThreads1.stdout - testsuite/driver/runtests.py - testsuite/driver/term_color.py - testsuite/driver/testlib.py - + testsuite/tests/patsyn/should_compile/T27440a.hs - + testsuite/tests/patsyn/should_compile/T27440b.hs - + testsuite/tests/patsyn/should_compile/T27440c.hs - testsuite/tests/patsyn/should_compile/all.T - + testsuite/tests/patsyn/should_fail/T27440d.hs - + testsuite/tests/patsyn/should_fail/T27440d.stderr - testsuite/tests/patsyn/should_fail/all.T - testsuite/tests/rts/all.T - + testsuite/tests/th/T20902.hs - testsuite/tests/th/all.T - + testsuite/tests/vdq-rta/should_compile/T27583a.hs - + testsuite/tests/vdq-rta/should_compile/T27583b.hs - + testsuite/tests/vdq-rta/should_compile/T27583c.hs - + testsuite/tests/vdq-rta/should_compile/T27583d.hs - + testsuite/tests/vdq-rta/should_compile/T27583e.hs - + testsuite/tests/vdq-rta/should_compile/T27583g.hs - testsuite/tests/vdq-rta/should_compile/all.T - + testsuite/tests/vdq-rta/should_fail/T27440e.hs - + testsuite/tests/vdq-rta/should_fail/T27440e.stderr - + testsuite/tests/vdq-rta/should_fail/T27583f.hs - + testsuite/tests/vdq-rta/should_fail/T27583f.stderr - testsuite/tests/vdq-rta/should_fail/all.T The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/ba632eb7b6bf04487156484e672467… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/ba632eb7b6bf04487156484e672467… You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc][wip/az/exactprint-annotation-rationalisation] 44 commits: Introduce global unit database cache
by Alan Zimmerman (＠alanz) 03 Aug '26

03 Aug '26

Alan Zimmerman pushed to branch wip/az/exactprint-annotation-rationalisation at Glasgow Haskell Compiler / GHC Commits: 5d0ab71a by fendor at 2026-07-27T17:31:05-04:00 Introduce global unit database cache As a first step for better sharing of `UnitInfo` across `UnitEnv`, we introduce a new datatype called `ExternalUnitDatabases`. It primarily serves as an in-memory representation of *all* `UnitDatabase`s across `UnitEnv`. This means, if multiple `HomeUnitEnv`s depend on the same database, one way or another, we make sure that we don't parse from disk every time. Instead, we store the in-memory representation in `ExternalUnitDatabases`. `ExternalUnitDatabaseCache` is the equivalent of `ExternalUnitState` in the `UnitEnv`. It is a mutable variable wrapping `ExternalUnitDatabases`. The mutable `ExternalUnitDatabaseCache` is used in `initUnits` to make sure we don't parse the same unit database multiple times. Almost by accident, we change the semantics of `initUnits` to honour modifications to `packageDBFlags`. The inability to change `packageDBFlags` while also reusing the already parsed `UnitDatabase`s was reported in #26423 as a bug. Hence, we think this behaviour change is warranted and acceptable, especially since it comes with a breaking change to the `initUnits` API. Add regression test for #26423 Closes #26423 - - - - - 6cce494a by fendor at 2026-07-27T17:31:05-04:00 Introduce UnitIndex for global external unit caching `UnitInfo`s have been observed to cause a lot of memory usage in #27500. Especially with multiple home units, as the same (external) units are processed from scratch, even though most of the time we end up with exactly the same `UnitInfo`. We introduce a `UnitEnv` global cache that allows us to store external unit information that is used across all `HomeUnitEnv`s. The most important change in this commit is the introduction of the `UnitIndex`. It stores a global mapping of `UnitId` -> `UnitInfo`, and `initUnits` always uses the cached `UnitInfo` entry to populate each `HomeUnitEnv`'s `UnitState`. This allows us to ensure the following property: > Each `UnitInfo` should be alive exactly once in GHC. All `UnitState`s should reference 'UnitInfo's stored in the 'UnitIndex'. This ensured by calling 'initUnits' with the 'UnitIndex'. In addition, the `ExternalUnitDatabases` may also hold a reference to each on-disk representation of `UnitInfo`. This means, we impose an hard upper bound on the number of `UnitInfo`s alive in the GHC session: > The number of alive `UnitInfo`s closure objects must be the > sum of all loaded unit database times two. We add performance regression tests that make sure the number of live `UnitInfo` cannot exceed this threshold. Closes #27500 ------------------------- Metric Decrease: MultiComponentModules MultiComponentModulesRecomp MultiComponentModulesRecomp100 mhu-perf LinkableUsage02 ------------------------- These metrics increases are especially notable, as we are not even sharing anything big but merely the global package database with 50 entries. It shows how careful sharing of `UnitInfo` can improve memory usage. We expect this to be much more notable when the whole cabal package database is shared across multiple home units. `LinkableUsage02` metric decreases on unreg and i386 platform, only. --- Technical details To share the `UnitInfo`s correctly, it is important that we extract the `WireMap` into the `UnitIndex`. At the moment of writing, `WireMap` must be globally the same for all `HomeUnitEnv`s. This is important, as we could otherwise not cache the "fully-resolved" `UnitInfo`, as we don't change the `UnitId` or `unitAbiHash` when resolving wired-in units. Thus, there could be ambiguities, when the `WireMap` is not the same for all `UnitState`s across the `UnitEnv`. We consider a `UnitInfo` fully-resolved, if wired-in units have been updated, the `UnitInfo` has been validated and variables in the unit config, such as `${pkgroot}` have been resolved. Updating the wired-in units requires the `WireMap` to be globally the same. - - - - - f8e3bee9 by Zubin Duggal at 2026-07-27T17:31:49-04:00 testsuite: skip runtime stats tests on debugged compilers Debugged flavours build the boot libraries without optimisation, so the runtime numbers do not match the baselines. - - - - - 1e326770 by Zubin Duggal at 2026-07-27T17:31:50-04:00 testsuite: mark #20706 tests fragile rather than broken Whether the static linux linker issues manifest depends on the host toolchain. - - - - - c0b13cbe by Zubin Duggal at 2026-07-27T17:31:50-04:00 testsuite: exclude libnuma from mostly-static It needs static system libraries (libnuma.a) that many platforms do not ship. Fixes #26914 - - - - - bee1913d by Alan Zimmerman at 2026-07-28T16:42:29-04:00 EPA: ClsInstDecl with decls as [LHsDecl GhcPs] in GhcPs Similar to 4fdfe75731e01dad7d7fa474c2703d0d3965afb1, this commit changes the as-parsed representation of class instance declarations to [LHsDecl GhcPs], and only separates them by type from the renamer onward. This also allows us to remove all the AnnSortKey machinery for exact printing, as it is now no longer needed. - - - - - 72c55eee by Cheng Shao at 2026-07-28T16:43:11-04:00 hadrian: implement and use writeFileAtomic to fix race condition This patch implements `writeFileAtomic` in hadrian and change all invocations of shake non-atomic `writeFile'` to use `writeFileAtomic`, to avoid multiple hadrian concurrent invocations overwriting the same in-tree generated file not in the build root directory. Fixes #27536. Additional notes: - `writeFileChanged`/`writeFileChangedBS` cannot be made atomic since it involves reading the file's older version, so their uses are left alone. It doesn't affect #27536 given their outputs are contained in the build root directory. - It's possible to shrink this patch by only making writes outside the build root directory atomic. But I think it's not worth the effort for fine grained distinction here, and atomic writes within the build root directory should also improve robustness of a hadrian build. - In the longer term we do want to make a ghc build only generate files within the build root directory, though that's a lot of work and outside the scope of this particular bugfix. Co-authored-by: Codex <codex(a)openai.com> - - - - - 46d4f963 by Sylvain Henry at 2026-07-29T06:38:40-04:00 RTS: correctly mark slop bytes when shrinking large arrays (#19048) Correctly mark slop bytes even when profiling is off so that heap census doesn't traverse garbage-collected closures. - - - - - 4762a8bf by Simon Jakobi at 2026-07-29T06:39:23-04:00 Add -XLazyFieldAnnotations (GHC proposal 752) Unbundle the prefix `~` lazy field annotation syntax from StrictData. The new LazyFieldAnnotations extension controls whether `~` is accepted on constructor fields. StrictData (and Strict, transitively) imply the new extension. See https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0752-l…. Closes #24455. Assisted-by: Claude Opus 4.8 - - - - - 0b6dcc84 by Simon Jakobi at 2026-07-29T06:40:04-04:00 testsuite: Relax T24471 residency tolerance T24471 peak residency fluctuates enough on i386 to cause spurious failures. Use the standard residency tolerance while retaining the existing allocation threshold. See https://gitlab.haskell.org/ghc/ghc/-/work_items/24471#note_682303. Assisted-by: gpt-5.6-sol via Codex CLI - - - - - 90e95b34 by Cheng Shao at 2026-07-29T06:40:45-04:00 compiler: fix missing top-level procedure labels in cmm dumps This patch fixes missing top-level procedure labels in some intermediate Cmm pass dumps. Fixes #27553. Co-authored-by: Codex <codex(a)openai.com> - - - - - 360a5946 by sheaf at 2026-07-29T06:41:35-04:00 Add some type-family-heavy performance tests FamAppCachePerf stress-tests the performance of lookups in the type family application cache. T27336 is a minimisation extracted from the reported reproducer. SimplCastPerf is a measure of coercion growth due to the simplifier calling mkTransCo without re-optimising the result. - - - - - 3ec9e2b9 by Mike Pilgrem at 2026-07-31T08:21:33-04:00 GHC Guide: Improve docs on response files - - - - - e5b2a1f7 by sheaf at 2026-07-31T08:22:23-04:00 Disable Core Lint for TcPlugin_RewritePerf This is a compiler performance test, but the test source hard-coded -dcore-lint, defeating the measurement. ------------------------- Metric Decrease: TcPlugin_RewritePerf ------------------------- - - - - - 85b10c00 by Alan Zimmerman at 2026-07-31T22:09:47+01:00 EPA: Remove LocatedP from OverlapMode We have type LocatedP = GenLocated SrcSpanAnnP type SrcSpanAnnP = EpAnn AnnPragma As the first step in removing this in favour of LocatedA which only captures location, comments and trailing annotations, we remove it from OverlapMode We do this by moving the AnnPragma into the TTG extension point instead. - - - - - c9a34a00 by Viktor Dukhovni at 2026-08-02T04:34:17-04:00 Fix note typo - - - - - 4f2a21f7 by Andreas Klebinger at 2026-08-02T22:46:46-04:00 Apply oneShot Monad trick to STG LintM - - - - - 21e4b89d by Andreas Klebinger at 2026-08-02T22:46:46-04:00 stgLint: Use a single reader env for read only arguments. - - - - - d415f38a by Alan Zimmerman at 2026-08-02T22:47:27-04:00 EPA: Remove LocatedP from CType The next step of removing use of LocatedP by moving the AnnPragma for CType into its TTG extension point instead. - - - - - e5f9f3eb by Alan Zimmerman at 2026-08-03T18:26:18+01:00 EPA: Remove LocatedP, last use in WarningTxt The last step of removing LocatedP, by moving the AnnPragma for WarningTxt into its TTG extension point instead. This also allows us to remove LocatedP and SrcSpanAnnP - - - - - 05a324bf by Alan Zimmerman at 2026-08-03T21:13:02+01:00 EPA: Replace AnnPragma with individual types We introduced AnnPragma as a common type for all pragma usages wrapped in LocatedP / SrcSpanAnnP. Now that those are gone, and the AnnPragma moved into the TTG points for the given items, we can ensure that each carries only the annotations it needs. So we remove AnnPragma, and in its place bring in AnnCType AnnWarningTxt AnnOverlap AnnAnnDecl AnnPragSCC - - - - - d1324892 by Alan Zimmerman at 2026-08-03T21:17:18+01:00 EPA: Remove LocatedE from WarningCategory - - - - - 0c65c751 by Alan Zimmerman at 2026-08-03T21:17:18+01:00 EPA: Remove LocateE from XCImport and XCExport - - - - - a4cff4ac by Alan Zimmerman at 2026-08-03T21:17:18+01:00 EPA: Remove LocatedE from HsRecFields dot - - - - - 819d8fd9 by Alan Zimmerman at 2026-08-03T21:17:18+01:00 EPA: Remove LocatedE completely, last usage for pats - - - - - b4b1871b by Alan Zimmerman at 2026-08-03T21:17:18+01:00 EPA: Remove AnnList (EpToken "where") usages This is moving toward removing the parameter from AnnList completely - - - - - e0912045 by Alan Zimmerman at 2026-08-03T21:17:18+01:00 EPA remove AnnList (EpToken "rec") usages - - - - - ee44383e by Alan Zimmerman at 2026-08-03T21:17:18+01:00 EPA: Remove last parameterised AnnList usage (EpaLocation) Also remove the parameter - - - - - 291eb095 by Alan Zimmerman at 2026-08-03T21:17:18+01:00 TTG: Add extension points to BooleanFormula They are currently unused, but will be used for exact print annotations next - - - - - a3b25808 by Alan Zimmerman at 2026-08-03T21:22:16+01:00 EPA: Remove LocatedBC / SrcSpanBF - - - - - 3748c627 by Alan Zimmerman at 2026-08-03T21:22:16+01:00 EPA: remove unused addTrailingAnnToL. Squash appropriately - - - - - 86fe1085 by Alan Zimmerman at 2026-08-03T21:22:16+01:00 EPS: Remove NoEpTok/NoEpUniTok, using an unhelpful SrcSpan instead Also introduce helper functions noEpTok and noEpUniTok to serve as simple replacements in code inserting an token annotation without location information. - - - - - 46d192a7 by Alan Zimmerman at 2026-08-03T21:22:16+01:00 EPA: Some haddock processing tweaks - - - - - 8c523fa1 by Alan Zimmerman at 2026-08-03T21:22:16+01:00 Some haddock exactprint tests - - - - - 48bc4217 by Alan Zimmerman at 2026-08-03T21:22:16+01:00 EPA: When adding comments honour trailing anns - - - - - 9a28180c by Alan Zimmerman at 2026-08-03T21:22:16+01:00 EPA: Uses Parsers.parseModule for exactprint tests This is the advertised way to parse for use for exact printing in the ghc-exactprint library, make sure we test using it. - - - - - a4e41fb9 by Alan Zimmerman at 2026-08-03T21:22:16+01:00 EPA Fix HsCmdDo exact print with comments TODO: add test based on proc-do-complex-four-out.hs - - - - - 4a2e28d2 by Alan Zimmerman at 2026-08-03T22:40:03+01:00 EPA: Add comments about remaining Anno SrcSpan instances - - - - - c44b4a0c by Alan Zimmerman at 2026-08-03T22:40:03+01:00 EPA: First pass implementation of HsList, for ClassDecls Just as a straight list replacement to start with, no payload. This shows the scope and invasiveness of the initial change - - - - - e6ee9704 by Alan Zimmerman at 2026-08-03T22:40:35+01:00 WIP - - - - - 331c5b27 by Alan Zimmerman at 2026-08-03T22:40:43+01:00 Enable ppr test for Haddock1. It currently fails - - - - - 6d3c2475 by Alan Zimmerman at 2026-08-03T22:40:43+01:00 WIP on removing NoEpAnn. Likely abandon - - - - - 7f8e094c by Alan Zimmerman at 2026-08-03T22:40:43+01:00 EPA: Add an overview doc for exact printing - - - - - 3b067e16 by Simon Peyton Jones at 2026-08-03T22:40:43+01:00 Added an intro section - - - - - 205 changed files: - + ExactPrint.md - + changelog.d/T26423 - + changelog.d/fix-cmm-dump-labels - + changelog.d/fix-heap-census-large-arrays-19048 - + changelog.d/lazy-field-annotations - + changelog.d/unit-index - compiler/GHC.hs - compiler/GHC/Builtin/Utils.hs - compiler/GHC/Cmm/Pipeline.hs - compiler/GHC/Core/Class.hs - compiler/GHC/CoreToIface.hs - compiler/GHC/Data/BooleanFormula.hs - compiler/GHC/Driver/Backpack.hs - compiler/GHC/Driver/Env.hs - compiler/GHC/Driver/Flags.hs - compiler/GHC/Driver/Main/Hsc.hs - compiler/GHC/Driver/Main/Interactive.hs - compiler/GHC/Driver/Main/Passes.hs - compiler/GHC/Driver/Session/Units.hs - compiler/GHC/Hs.hs - compiler/GHC/Hs/Binds.hs - compiler/GHC/Hs/Decls.hs - compiler/GHC/Hs/Decls/Overlap.hs - compiler/GHC/Hs/Doc.hs - compiler/GHC/Hs/DocString.hs - compiler/GHC/Hs/Dump.hs - compiler/GHC/Hs/Expr.hs - compiler/GHC/Hs/Extension/Pass.hs - compiler/GHC/Hs/ImpExp.hs - compiler/GHC/Hs/Instances.hs - compiler/GHC/Hs/Pat.hs - compiler/GHC/Hs/Stats.hs - compiler/GHC/Hs/Utils.hs - compiler/GHC/HsToCore/Docs.hs - compiler/GHC/HsToCore/Quote.hs - compiler/GHC/Iface/Ext/Ast.hs - compiler/GHC/Iface/Syntax.hs - compiler/GHC/Iface/Warnings.hs - compiler/GHC/IfaceToCore.hs - compiler/GHC/Parser.y - compiler/GHC/Parser/Annotation.hs - compiler/GHC/Parser/PostProcess.hs - compiler/GHC/Parser/PostProcess/Haddock.hs - compiler/GHC/Rename/Module.hs - compiler/GHC/Rename/Names.hs - compiler/GHC/Rename/Pat.hs - compiler/GHC/Rename/Splice.hs - compiler/GHC/Stg/Lint.hs - compiler/GHC/Tc/Deriv.hs - compiler/GHC/Tc/Errors/Ppr.hs - compiler/GHC/Tc/Errors/Types.hs - compiler/GHC/Tc/Module.hs - compiler/GHC/Tc/TyCl.hs - compiler/GHC/Tc/TyCl/Class.hs - compiler/GHC/Tc/TyCl/Instance.hs - compiler/GHC/Tc/Types/Origin.hs - compiler/GHC/Tc/Utils/Env.hs - compiler/GHC/Tc/Utils/Instantiate.hs - compiler/GHC/ThToHs.hs - compiler/GHC/Types/ForeignCall.hs - compiler/GHC/Types/Unique.hs - compiler/GHC/Unit/Env.hs - + compiler/GHC/Unit/External/Database.hs - + compiler/GHC/Unit/External/Index.hs - + compiler/GHC/Unit/External/ModuleOrigin.hs - + compiler/GHC/Unit/External/Providers.hs - + compiler/GHC/Unit/External/Query.hs - + compiler/GHC/Unit/External/Substitution.hs - + compiler/GHC/Unit/External/Validate.hs - + compiler/GHC/Unit/External/Visibility.hs - + compiler/GHC/Unit/External/Wired.hs - compiler/GHC/Unit/Home/Graph.hs - compiler/GHC/Unit/Info.hs - compiler/GHC/Unit/Module/Warnings.hs - compiler/GHC/Unit/State.hs - compiler/GHC/Unit/State.hs-boot - compiler/GHC/Unit/Types.hs - compiler/Language/Haskell/Syntax.hs - compiler/Language/Haskell/Syntax/Basic.hs - compiler/Language/Haskell/Syntax/BooleanFormula.hs - compiler/Language/Haskell/Syntax/Decls.hs - compiler/Language/Haskell/Syntax/Expr.hs - compiler/Language/Haskell/Syntax/Extension.hs - compiler/ghc.cabal.in - docs/users_guide/exts/strict.rst - docs/users_guide/using.rst - ghc/GHCi/UI.hs - hadrian/src/Hadrian/Builder/Ar.hs - hadrian/src/Hadrian/Utilities.hs - hadrian/src/Rules/BinaryDist.hs - hadrian/src/Rules/CabalReinstall.hs - hadrian/src/Rules/Documentation.hs - hadrian/src/Rules/Generate.hs - hadrian/src/Rules/Library.hs - hadrian/src/Rules/Nofib.hs - hadrian/src/Rules/Program.hs - hadrian/src/Rules/Register.hs - hadrian/src/Rules/Rts.hs - hadrian/src/Rules/SourceDist.hs - hadrian/src/Rules/Test.hs - hadrian/src/Rules/ToolArgs.hs - libraries/ghc-internal/src/GHC/Internal/Ix.hs - libraries/ghc-internal/src/GHC/Internal/LanguageExtensions.hs - rts/Apply.cmm - rts/ZeroSlop.c → rts/MarkSlop.c - rts/PrimOps.cmm - rts/Printer.c - rts/ProfHeap.c - rts/RtsFlags.c - rts/ThreadPaused.c - rts/include/Cmm.h - rts/include/rts/storage/ClosureMacros.h - rts/rts.cabal - rts/sm/NonMovingMark.c - rts/sm/Sanity.c - rts/sm/Storage.c - testsuite/driver/testlib.py - testsuite/tests/count-deps/CountDepsParser.stdout - + testsuite/tests/deSugar/should_run/LazyFieldAnnotationsSemantics.hs - + testsuite/tests/deSugar/should_run/LazyFieldAnnotationsSemantics.stdout - testsuite/tests/deSugar/should_run/all.T - + testsuite/tests/driver/T26423/Hello.hs - + testsuite/tests/driver/T26423/Makefile - + testsuite/tests/driver/T26423/T26423.hs - + testsuite/tests/driver/T26423/T26423.stderr - + testsuite/tests/driver/T26423/T26423.stdout - + testsuite/tests/driver/T26423/all.T - + testsuite/tests/driver/T26423/test/Test.hs - + testsuite/tests/driver/T26423/test/test.pkg - testsuite/tests/driver/T4437.hs - + testsuite/tests/driver/TUnitInfo/Foo.hs - + testsuite/tests/driver/TUnitInfo/Makefile - + testsuite/tests/driver/TUnitInfo/all.T - + testsuite/tests/driver/TUnitInfo/genMhu.sh - + testsuite/tests/driver/TUnitInfo/generic-unit-info-space-mhu.stdout - + testsuite/tests/driver/TUnitInfo/generic-unit-info-space-single.stdout - + testsuite/tests/driver/TUnitInfo/generic-unit-info-space.hs - + testsuite/tests/driver/TUnitInfo/generic-unit-info-space.stdout - 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testsuite/tests/printer/all.T - + testsuite/tests/rts/T19048.hs - + testsuite/tests/rts/T19048.stdout - testsuite/tests/rts/all.T - testsuite/tests/rts/linker/all.T - testsuite/tests/tcplugins/TcPlugin_RewritePerf.hs - testsuite/tests/tcplugins/TcPlugin_RewritePerf.stderr - + testsuite/tests/typecheck/should_compile/LazyFieldAnnotations.hs - testsuite/tests/typecheck/should_compile/all.T - testsuite/tests/typecheck/should_fail/LazyFieldsDisabled.stderr - + testsuite/tests/typecheck/should_fail/LazyFieldsDisabledStrictData.hs - + testsuite/tests/typecheck/should_fail/LazyFieldsDisabledStrictData.stderr - testsuite/tests/typecheck/should_fail/all.T - utils/check-exact/ExactPrint.hs - utils/check-exact/Main.hs - utils/check-exact/Parsers.hs - utils/check-exact/Transform.hs - utils/check-exact/Utils.hs - utils/haddock/haddock-api/src/Haddock.hs - utils/haddock/haddock-api/src/Haddock/Backends/Hoogle.hs - utils/haddock/haddock-api/src/Haddock/Backends/LaTeX.hs - utils/haddock/haddock-api/src/Haddock/Backends/Xhtml/Decl.hs - utils/haddock/haddock-api/src/Haddock/Convert.hs - utils/haddock/haddock-api/src/Haddock/GhcUtils.hs - utils/haddock/haddock-api/src/Haddock/Interface/Create.hs - utils/haddock/haddock-api/src/Haddock/Interface/Rename.hs - utils/haddock/haddock-api/src/Haddock/Types.hs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/2199059c89f8abbc8f6bbf75c1f823… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/2199059c89f8abbc8f6bbf75c1f823… You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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