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[Git][ghc/ghc][master] Fix subtle bug in cast worker/wrapper
by Marge Bot (＠marge-bot) 12 Feb '26

12 Feb '26

Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC Commits: 99d8c146 by Simon Peyton Jones at 2026-02-12T17:36:59+00:00 Fix subtle bug in cast worker/wrapper See (CWw4) in Note [Cast worker/wrapper]. The true payload is in the change to the definition of GHC.Types.Id.Info.hasInlineUnfolding Everthing else is just documentation. There is a 2% compile time decrease for T13056; I'll take the win! Metric Decrease: T13056 - - - - - 8 changed files: - compiler/GHC/Core/Opt/Simplify/Iteration.hs - compiler/GHC/Core/Opt/WorkWrap.hs - compiler/GHC/Driver/Config/Core/Lint.hs - compiler/GHC/Types/Id/Info.hs - + testsuite/tests/simplCore/should_compile/T26903.hs - + testsuite/tests/simplCore/should_compile/T26903.stderr - testsuite/tests/simplCore/should_compile/T8331.stderr - testsuite/tests/simplCore/should_compile/all.T Changes: ===================================== compiler/GHC/Core/Opt/Simplify/Iteration.hs ===================================== @@ -474,14 +474,14 @@ leaving a simpler job for demand-analysis worker/wrapper. See #19874. Wrinkles -1. We must /not/ do cast w/w on +(CWW1) We must /not/ do cast w/w on f = g |> co otherwise it'll just keep repeating forever! You might think this is avoided because the call to tryCastWorkerWrapper is guarded by - preInlineUnconditinally, but I'm worried that a loop-breaker or an - exported Id might say False to preInlineUnonditionally. + preInlineUnconditionally, but I'm worried that a loop-breaker or an + exported Id might say False to preInlineUnconditionally. -2. We need to be careful with inline/noinline pragmas: +(CWW2) We need to be careful with inline/noinline pragmas: rec { {-# NOINLINE f #-} f = (...g...) |> co ; g = ...f... } @@ -496,15 +496,15 @@ Wrinkles f = $wf |> co ; g = ...f... } and that is bad: the whole point is that we want to inline that - cast! We want to transfer the pagma to $wf: + cast! We want to transfer the pragma to $wf: rec { {-# NOINLINE $wf #-} $wf = ...g... ; f = $wf |> co ; g = ...f... } c.f. Note [Worker/wrapper for NOINLINE functions] in GHC.Core.Opt.WorkWrap. -3. We should still do cast w/w even if `f` is INLINEABLE. E.g. - {- f: Stable unfolding = <stable-big> -} +(CWW3) We should still do cast w/w even if `f` is INLINEABLE. E.g. + {- f: Stable unfolding (arity 2) = <stable-big> -} f = (\xy. <big-body>) |> co Then we want to w/w to {- $wf: Stable unfolding = <stable-big> |> sym co -} @@ -513,15 +513,43 @@ Wrinkles Notice that the stable unfolding moves to the worker! Now demand analysis will work fine on $wf, whereas it has trouble with the original f. c.f. Note [Worker/wrapper for INLINABLE functions] in GHC.Core.Opt.WorkWrap. - This point also applies to strong loopbreakers with INLINE pragmas, see - wrinkle (4). -4. We should /not/ do cast w/w for non-loop-breaker INLINE functions (hence - hasInlineUnfolding in tryCastWorkerWrapper, which responds False to - loop-breakers) because they'll definitely be inlined anyway, cast and - all. And if we do cast w/w for an INLINE function with arity zero, we get +(CWW4) We should /not/ do cast w/w for INLINE functions (hence `hasInlineUnfolding` + in `tryCastWorkerWrapper`) because they'll definitely be inlined anyway, cast + and all. + + Moreover, if we do cast w/w for an INLINE function with arity zero, we get something really silly: we inline that "worker" right back into the wrapper! - Worse than a no-op, because we have then lost the stable unfolding. + In fact it is Much Worse than a no-op, because we have then lost the stable + unfolding --- aargh (see #26903). E.g. similar example to (CWW3) + {- g: Stable unfolding (arity 0) = <stable-big> -} NB arity 0! + g = (\xy. <big-body>) |> co + If we w/w to this: + {- $wg: Stable unfolding (arity 0) = <stable-big> |> sym co -} + $wg = \xy. <big-body> + g = $wg |> co + then we'll inline $wg at the call site in `g` giving + {- $wg: Stable unfolding (arity 0) = <stable-big> |> sym co -} + $wg = \xy. <big-body> + g = (<stable-big> |> sym co) |> co + and now we'll drop `$wg` as dead and we have lost the unfolding on `g`. + (We could /also/ give the binding `g = $wf |> co` a stable unfolding. Then + things would work right; but there is also no point in doing the cast + worker/wrapper in the first place.) + + NB: you might wonder about a loop-breaker with an INLINE pragma; after all, a + loop breaker won't "definitely be inlined anyway", so arguably we should not + disable cast w/w/ for it. But a Rec group can /look/ recursive at an early + stage, and subsequently /become/ non-recursive after some simplification. + (This is common in instance decls; see Note [Checking for INLINE loop breakers] + in GHC.Core.Lint.) So the danger is that we'll permanently lose that stable + unfolding that we specifically wanted (#26903). Simple solution: disable cast + w/w for /any/ INLINE function. See the defn + of `GHC.Types.Id.Info.hasInlineUnfolding`. + + The danger is that an INLINE pragma on a genuninely-recursive function + will kill worker-wrapper. Well, so be it. They are pretty suspicious anyway; + see Note [Checking for INLINE loop breakers]. All these wrinkles are exactly like worker/wrapper for strictness analysis: f is the wrapper and must inline like crazy @@ -586,11 +614,11 @@ tryCastWorkerWrapper env bind_cxt old_bndr bndr (Cast rhs co) | BC_Let top_lvl is_rec <- bind_cxt -- Not join points , not (isDFunId bndr) -- nor DFuns; cast w/w is no help, and we can't transform -- a DFunUnfolding in mk_worker_unfolding - , not (exprIsTrivial rhs) -- Not x = y |> co; Wrinkle 1 - , not (hasInlineUnfolding info) -- Not INLINE things: Wrinkle 4 - , typeHasFixedRuntimeRep work_ty -- Don't peel off a cast if doing so would - -- lose the underlying runtime representation. - -- See Note [Preserve RuntimeRep info in cast w/w] + , not (exprIsTrivial rhs) -- Not x = y |> co; see (CWW1) + , not (hasInlineUnfolding info) -- Not INLINE things: see (CWW4) + , typeHasFixedRuntimeRep work_ty -- Don't peel off a cast if doing so would + -- lose the underlying runtime representation. + -- See Note [Preserve RuntimeRep info in cast w/w] , not (isOpaquePragma (idInlinePragma old_bndr)) -- Not for OPAQUE bindings -- See Note [OPAQUE pragma] = do { uniq <- getUniqueM @@ -637,13 +665,13 @@ tryCastWorkerWrapper env bind_cxt old_bndr bndr (Cast rhs co) `setArityInfo` work_arity -- We do /not/ want to transfer OccInfo, Rules -- Note [Preserve strictness in cast w/w] - -- and Wrinkle 2 of Note [Cast worker/wrapper] + -- and (CWW2) of Note [Cast worker/wrapper] ----------- Worker unfolding ----------- -- Stable case: if there is a stable unfolding we have to compose with (Sym co); -- the next round of simplification will do the job -- Non-stable case: use work_rhs - -- Wrinkle 3 of Note [Cast worker/wrapper] + -- See (CWW4) of Note [Cast worker/wrapper] mk_worker_unfolding top_lvl work_id work_rhs = case realUnfoldingInfo info of -- NB: the real one, even for loop-breakers unf@(CoreUnfolding { uf_tmpl = unf_rhs, uf_src = src }) ===================================== compiler/GHC/Core/Opt/WorkWrap.hs ===================================== @@ -179,8 +179,9 @@ several liked-named Ids bouncing around at the same time---absolute mischief.) Notice that we refrain from w/w'ing an INLINE function even if it is -in a recursive group. It might not be the loop breaker. (We could -test for loop-breaker-hood, but I'm not sure that ever matters.) +in a recursive group. It might not be the loop breaker. (We used to +test for loop-breaker-hood, but see (CWW4) in Note [Cast worker/wrapper] +in GHC.Core.Opt.Simplify.Iteration.) Note [Worker/wrapper for INLINABLE functions] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ===================================== compiler/GHC/Driver/Config/Core/Lint.hs ===================================== @@ -132,8 +132,6 @@ perPassFlags dflags pass -- there may be some INLINE knots still tied, which is tiresomely noisy CoreDoSimplify cfg | SimplPhase InitialPhase <- sm_phase (so_mode cfg) - -> True - | otherwise -> False _ -> True ===================================== compiler/GHC/Types/Id/Info.hs ===================================== @@ -610,7 +610,12 @@ hasInlineUnfolding :: IdInfo -> Bool -- ^ True of a /non-loop-breaker/ Id that has a /stable/ unfolding that is -- (a) always inlined; that is, with an `UnfWhen` guidance, or -- (b) a DFunUnfolding which never needs to be inlined -hasInlineUnfolding info = isInlineUnfolding (unfoldingInfo info) +-- +-- Very important that this work with `realUnfoldingInfo` and so returns +-- True even for a loop-breaker that has an INLINE pragma. +-- See (CWW4) in Note [Cast worker/wrapper] in GHC.Core.Opt.Simplify.Iteration +-- for discussion, and #26903 for the dire consequences of getting this wrong. +hasInlineUnfolding info = isInlineUnfolding (realUnfoldingInfo info) setArityInfo :: IdInfo -> ArityInfo -> IdInfo setArityInfo info ar = ===================================== testsuite/tests/simplCore/should_compile/T26903.hs ===================================== @@ -0,0 +1,23 @@ +{-# LANGUAGE DefaultSignatures #-} +module T26903 where + +newtype T a = MkT [a] + +class C a where + op :: [a] -> [a] -> T a + + -- This default method + -- * Has an INLINE pragma + -- * Is too big to inline without a pragma + -- * Has arity zero + {-# INLINE[1] op #-} + default op :: Ord a => [a] -> [a] -> T a + op = \xs ys -> MkT $ if xs>ys then reverse (reverse (reverse (reverse xs))) + else reverse (reverse (reverse (reverse (xs ++ ys)))) + +instance C Int where {} + +test :: [Int] -> T Int +test xs = op [] xs + -- We expect to see `op` inlined into the RHS of `test` + ===================================== testsuite/tests/simplCore/should_compile/T26903.stderr ===================================== @@ -0,0 +1,52 @@ + +==================== Tidy Core ==================== +Result size of Tidy Core + = {terms: 127, types: 130, coercions: 48, joins: 0/0} + +$dmop + = (\ @a _ $dOrd xs ys -> + case $fOrdList_$ccompare $dOrd xs ys of { + __DEFAULT -> + reverse1 (reverse1 (reverse1 (reverse1 (++ xs ys) []) []) []) []; + GT -> reverse1 (reverse1 (reverse1 (reverse xs) []) []) [] + }) + `cast` <Co:20> :: ... + +$fCInt_$cop + = (\ xs ys -> + case $fOrdList_$s$ccompare xs ys of { + __DEFAULT -> + reverse1 (reverse1 (reverse1 (reverse1 (++ xs ys) []) []) []) []; + GT -> reverse1 (reverse1 (reverse1 (reverse xs) []) []) [] + }) + `cast` <Co:11> :: ... + +$fCInt1 + = \ xs ys -> + case $fOrdList_$s$ccompare xs ys of { + __DEFAULT -> + reverse1 (reverse1 (reverse1 (reverse1 (++ xs ys) []) []) []) []; + GT -> reverse1 (reverse1 (reverse1 (reverse xs) []) []) [] + } + +$fCInt = C:C ($fCInt1 `cast` <Co:11> :: ...) + +test4 = reverse1 [] [] + +test3 = reverse1 test4 [] + +test2 = reverse1 test3 [] + +test1 = reverse1 test2 [] + +test + = \ xs -> + case $fOrdList_$s$ccompare [] xs of { + __DEFAULT -> + (reverse1 (reverse1 (reverse1 (reverse1 (++ [] xs) []) []) []) []) + `cast` <Co:3> :: ...; + GT -> test1 `cast` <Co:3> :: ... + } + + + ===================================== testsuite/tests/simplCore/should_compile/T8331.stderr ===================================== @@ -56,11 +56,11 @@ ReaderT r (ST s) (a -> b) -> ReaderT r (ST s) a -> r -> ST s b)) "SPEC $c>> @(ST s) @_" forall (@s) (@r) ($dMonad :: Monad (ST s)). - $fMonadReaderT1 @(ST s) @r $dMonad + $fMonadReaderT_$c>> @(ST s) @r $dMonad = $fMonadAbstractIOSTReaderT_$s$c>> @s @r "SPEC $c>>= @(ST s) @_" forall (@s) (@r) ($dMonad :: Monad (ST s)). - $fMonadReaderT2 @(ST s) @r $dMonad + $fMonadReaderT1 @(ST s) @r $dMonad = ($fMonadAbstractIOSTReaderT2 @s @r) `cast` (forall (a ::~ <*>_N) (b ::~ <*>_N). <ReaderT r (ST s) a>_R ===================================== testsuite/tests/simplCore/should_compile/all.T ===================================== @@ -581,3 +581,4 @@ test('T26722', [grep_errmsg(r'SPEC')], compile, ['-O -dno-typeable-binds']) test('T26805', [grep_errmsg(r'fromInteger')], compile, ['-O -dno-typeable-binds -ddump-simpl -dsuppress-uniques']) test('T26826', normal, compile, ['-O']) +test('T26903', [grep_errmsg(r'reverse')], compile, ['-O -dno-typeable-binds -ddump-simpl -dsuppress-uniques -dsuppress-all']) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/99d8c146c12146e1e21b1f2d3180984… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/99d8c146c12146e1e21b1f2d3180984… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/io-manager-deadlock-detection] 4 commits: FIXUP Add wakeupIOManager support for select I/O manager
by Duncan Coutts (＠dcoutts) 12 Feb '26

12 Feb '26

Duncan Coutts pushed to branch wip/io-manager-deadlock-detection at Glasgow Haskell Compiler / GHC Commits: ecf70089 by Duncan Coutts at 2026-02-12T22:53:53+00:00 FIXUP Add wakeupIOManager support for select I/O manager - - - - - d4fa6e0e by Duncan Coutts at 2026-02-12T22:54:21+00:00 FIXUP Add wakeupIOManager support for poll I/O manager - - - - - 731729ec by Duncan Coutts at 2026-02-12T22:55:07+00:00 FIXUP: remove now-unused HAVE_EVENTFD_H and #includes - - - - - 0810b12f by Duncan Coutts at 2026-02-12T22:58:13+00:00 FIXME: turns out we do not need the bool after_fork. Simplify and rebase. - - - - - 5 changed files: - rts/IOManager.h - rts/posix/MIO.c - rts/posix/Poll.c - rts/posix/Select.c - rts/posix/Signals.c Changes: ===================================== rts/IOManager.h ===================================== @@ -269,6 +269,8 @@ void initCapabilityIOManager(CapIOManager *iomgr); */ void freeCapabilityIOManager(CapIOManager *iomgr, bool after_fork); +// FIXME: turns out we do not need the bool after_fork. Simplify and rebase. + /* CapIOManager life cycle: * * alloc -> init -> free -> free struct (!after_fork) ===================================== rts/posix/MIO.c ===================================== @@ -22,10 +22,6 @@ # include <errno.h> #endif -#if defined(HAVE_EVENTFD_H) -# include <sys/eventfd.h> -#endif - #include <stdlib.h> #include <unistd.h> ===================================== rts/posix/Poll.c ===================================== @@ -158,9 +158,7 @@ void initCapabilityIOManagerPoll(CapIOManager *iomgr) void freeCapabilityIOManagerPoll(CapIOManager *iomgr, bool after_fork) { stgFree(iomgr->full_poll_table); - if (!after_fork) { - closeFdWakeup(iomgr->wakeup_fd_r, iomgr->wakeup_fd_w); - } + closeFdWakeup(iomgr->wakeup_fd_r, iomgr->wakeup_fd_w); } ===================================== rts/posix/Select.c ===================================== @@ -66,9 +66,7 @@ void initCapabilityIOManagerSelect(CapIOManager *iomgr) void freeCapabilityIOManagerSelect(CapIOManager *iomgr, bool after_fork) { - if (!after_fork) { - closeFdWakeup(iomgr->wakeup_fd_r, iomgr->wakeup_fd_w); - } + closeFdWakeup(iomgr->wakeup_fd_r, iomgr->wakeup_fd_w); } void wakeupIOManagerSelect(CapIOManager *iomgr) ===================================== rts/posix/Signals.c ===================================== @@ -37,10 +37,6 @@ # include <errno.h> #endif -#if defined(HAVE_EVENTFD_H) -# include <sys/eventfd.h> -#endif - #if defined(HAVE_TERMIOS_H) #include <termios.h> #endif View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/89687a43e569b42c0fd9e0f48a6272… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/89687a43e569b42c0fd9e0f48a6272… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/terrorjack/asan] 127 commits: Don't re-use stack slots for growing registers
by Cheng Shao (＠TerrorJack) 12 Feb '26

12 Feb '26

Cheng Shao pushed to branch wip/terrorjack/asan at Glasgow Haskell Compiler / GHC Commits: 023c301c by sheaf at 2026-01-13T04:57:30-05:00 Don't re-use stack slots for growing registers This commit avoids re-using a stack slot for a register that has grown but already had a stack slot. For example, suppose we have stack slot assigments %v1 :: FF64 |-> StackSlot 0 %v2 :: FF64 |-> StackSlot 1 Later, we start using %v1 at a larger format (e.g. F64x2) and we need to spill it again. Then we **must not** use StackSlot 0, as a spill at format F64x2 would clobber the data in StackSlot 1. This can cause some fragmentation of the `StackMap`, but that's probably OK. Fixes #26668 - - - - - d0966e64 by fendor at 2026-01-13T04:58:11-05:00 Remove `traceId` from ghc-pkg executable - - - - - 20d7efec by Simon Peyton Jones at 2026-01-13T12:41:22-05:00 Make SpecContr rules fire a bit later See #26615 and Note [SpecConstr rule activation] - - - - - 8bc4eb8c by Andrew Lelechenko at 2026-01-13T12:42:03-05:00 Upgrade mtl submodule to 2.3.2 Fixes #26656 - - - - - c94aaacd by Cheng Shao at 2026-01-13T12:42:44-05:00 compiler: remove iserv and only use on-demand external interpreter This patch removes `iserv` from the tree completely. Hadrian would no longer build or distribute `iserv`, and the GHC driver would use the on-demand external interpreter by default when invoked with `-fexternal-interpreter`, without needing to specify `-pgmi ""`. This has multiple benefits: - It allows cleanup of a lot of legacy hacks in the hadrian codebase. - It paves the way for running cross ghc's iserv via cross emulator (#25523), fixing TH/ghci support for cross targets other than wasm/js. - - - - - c1fe0097 by Peter Trommler at 2026-01-14T03:54:49-05:00 PPC NCG: Fix shift right MO code The shift amount in shift right [arithmetic] MOs is machine word width. Therefore remove unnecessary zero- or sign-extending of shift amount. It looks harmless to extend the shift amount argument because the shift right instruction uses only the seven lowest bits (i. e. mod 128). But now we have a conversion operation from a smaller type to word width around a memory load at word width. The types are not matching up but there is no check done in CodeGen. The necessary conversion from word width down to the smaller width would be translated into a no-op on PowerPC anyway. So all seems harmless if it was not for a small optimisation in getRegister'. In getRegister' a load instruction with the smaller width of the conversion operation was generated. This loaded the most significant bits of the word in memory on a big-endian platform. These bits were zero and hence shift right was used with shift amount zero and not one as required in test Sized. Fixes #26519 - - - - - 2dafc65a by Cheng Shao at 2026-01-14T03:55:31-05:00 Tree-wide cleanup of cygwin logic GHC has not supported cygwin for quite a few years already, and will not resume support in the forseeable future. The only supported windows toolchain is clang64/clangarm64 of the msys2 project. This patch cleans up the unused cygwin logic in the tree. Co-authored-by: Codex <codex(a)openai.com> - - - - - 66b96e2a by Teo Camarasu at 2026-01-14T03:56:13-05:00 Set default eventlog-flush-interval to 5s Resolves #26707 - - - - - d0254579 by Andrew Lelechenko at 2026-01-14T03:56:53-05:00 Document when -maxN RTS option was added - - - - - f25e2b12 by Cheng Shao at 2026-01-14T11:10:39-05:00 testsuite: remove obsolete --ci option from the testsuite driver This patch removes the obsolete `--ci` option from the testsuite driver: neither the CI scripts nor hadrian ever invokes the testsuite driver with `--ci`, and the perf notes are always fetched to the `refs/notes/perf` local reference anyway. - - - - - 7964763b by Julian Ospald at 2026-01-14T11:11:31-05:00 Fix fetch_cabal * download cabal if the existing one is of an older version * fix FreeBSD download url * fix unpacking on FreeBSD - - - - - 6b0129c1 by Julian Ospald at 2026-01-14T11:11:31-05:00 Bump toolchain in CI - - - - - 0f53ccc6 by Julian Ospald at 2026-01-14T11:11:31-05:00 Use libffi-clib Previously, we would build libffi via hadrian and bundle it manually with the GHC bindist. This now moves all that logic out of hadrian and allows us to have a clean Haskell package to build and link against and ship it without extra logic. This patch still retains the ability to link against a system libffi. The main reason of bundling libffi was that on some platforms (e.g. FreeBSD and Mac), system libffi is not visible to the C toolchain by default, so users would require settings in e.g. cabal to be able to compile anything. This adds the submodule libffi-clib to the repository. - - - - - 5e1cd595 by Peng Fan at 2026-01-14T11:12:26-05:00 NCG/LA64: add support for la664 micro architecture Add '-mla664' flag to LA664, which has some new features: atomic instructions, dbar hints, etc. 'LA464' is the default so that unrecognized instructions are not generated. - - - - - c56567ec by Simon Peyton Jones at 2026-01-15T23:19:04+00:00 Add evals for strict data-con args in worker-functions This fixes #26722, by adding an eval in a worker for arguments of strict data constructors, even if the function body uses them strictly. See (WIS1) in Note [Which Ids should be strictified] I took the opportunity to make substantial improvements in the documentation for call-by-value functions. See especially Note [CBV Function Ids: overview] in GHC.Types.Id.Info Note [Which Ids should be CBV candidates?] ditto Note [EPT enforcement] in GHC.Stg.EnforceEpt among others. - - - - - 9719ce5d by Simon Peyton Jones at 2026-01-15T23:19:04+00:00 Improve `interestingArg` This function analyses a function's argument to see if it is interesting enough to deserve an inlining discount. Improvements for * LitRubbish arguments * exprIsExpandable arguments See Note [Interesting arguments] which is substantially rewritten. - - - - - 7b616b9f by Cheng Shao at 2026-01-16T06:45:00-05:00 compiler: fix regression when compiling foreign stubs in the rts unit This patch fixes a regression when compiling foreign stubs in the rts unit introduced in 05e25647f72bc102061af3f20478aa72bff6ff6e. A simple revert would fix it, but it's better to implement a proper fix with comment for better understanding of the underlying problem, see the added comment for explanation. Co-authored-by: Codex <codex(a)openai.com> - - - - - c343ef64 by Sylvain Henry at 2026-01-16T06:45:51-05:00 base: remove GHC.JS.Prim.Internal.Build (#23432) See accepted CLC proposal https://github.com/haskell/core-libraries-committee/issues/329 - - - - - 29c0aceb by Simon Peyton Jones at 2026-01-16T17:18:11-05:00 Improve newtype unwrapping Ticket #26746 describes several relatively-minor shortcomings of newtype unwrapping. This MR addresses them, while also (arguably) simplifying the code a bit. See new Note [Solving newtype equalities: overview] and Note [Decomposing newtype equalities] and Note [Eager newtype decomposition] and Note [Even more eager newtype decomposition] For some reason, on Windows only, runtime allocations decrease for test T5205 (from 52k to 48k). I have not idea why. No change at all on Linux. I'm just going to accept the change. (I saw this same effect in another MR so I think it's a fault in the baseline.) Metric Decrease: T5205 - - - - - 8b59e62c by Andreas Klebinger at 2026-01-16T17:18:52-05:00 testsuite: Widen acceptance window for T5205. Fixes #26782 - - - - - 9e5e0234 by mangoiv at 2026-01-17T06:03:03-05:00 add a new issue template for getting verified To reduce spam created by new users, we will in future not grant any rights but reporting issues to new users. That is why we will have to be able to verify them. The added issue template serves that purpose. - - - - - b18b2c42 by Cheng Shao at 2026-01-17T06:03:44-05:00 llvm: fix split sections for llvm backend This patch fixes split sections for llvm backend: - Pass missing `--data-sections`/`--function-sections` flags to llc/opt. - Use `@llvm.compiler.used` instead of `@llvm.used` to avoid sections being unnecessarily retained at link-time. Fixes #26770. ------------------------- Metric Decrease: libdir size_hello_artifact size_hello_unicode ------------------------- Co-authored-by: Codex <codex(a)openai.com> - - - - - ebf66f67 by Cheng Shao at 2026-01-17T13:16:50-05:00 Update autoconf scripts Scripts taken from autoconf a2287c3041a3f2a204eb942e09c015eab00dc7dd - - - - - 598624b9 by Andreas Klebinger at 2026-01-17T13:17:32-05:00 CString.hs: Update incorrect comment. Fixes #26322 - - - - - eea2036b by Cheng Shao at 2026-01-18T10:00:49-05:00 libraries: bump haskeline submodule to 0.8.4.1 This patch bumps the haskeline submodule to 0.8.4.1 which includes an important fix for an ANSI handling bug on Windows (https://github.com/haskell/haskeline/pull/126) - - - - - 87d8f6c2 by Cheng Shao at 2026-01-18T10:01:30-05:00 hadrian: replace default -H32m/-H64m with -O64M to improve mutator productivity Most hadrian build flavours pass `-H32m`/`-H64m` to GHC as conventional wisdom to improve mutator productivity and reduce GC overhead. They were inherited from the legacy Make build system, and there used to be make flags to instrument a build process with `-Rghc-timing` option to collect GC stats of each GHC run from stderr. It's time to revisit whether there are better defaults for `-H32m`/`-H64m`, and this patch changes it to `-O64M` which indeed improves mutator productivity based on real statistics. `-O64M` is more aggressive than `-H64m`; it allows the old generation to grow to at least 64M before triggering major GC and reduces major GC runs. The stats of a clean build with `validate` flavour and `-H64m`: ``` h64m.log matched RTS stat lines: 5499 sum MUT cpu : 2400.808 s sum GC cpu : 1378.292 s sum MUT elapsed : 2788.253 s sum GC elapsed : 1389.233 s GC/MUT cpu ratio : 0.574 (GC is 57.4% of MUT) GC/MUT elapsed ratio : 0.498 (GC is 49.8% of MUT) GC fraction of (MUT+GC) cpu : 36.5% GC fraction of (MUT+GC) elapsed : 33.3% per-line GC/MUT cpu ratio: median 0.691, p90 1.777 per-line GC/MUT elapsed ratio: median 0.519, p90 1.081 ``` The stats of a clean build with `validate` flavour and `-O64M`: ``` o64m.log matched RTS stat lines: 5499 sum MUT cpu : 2377.383 s sum GC cpu : 1127.146 s sum MUT elapsed : 2758.857 s sum GC elapsed : 1135.587 s GC/MUT cpu ratio : 0.474 (GC is 47.4% of MUT) GC/MUT elapsed ratio : 0.412 (GC is 41.2% of MUT) GC fraction of (MUT+GC) cpu : 32.2% GC fraction of (MUT+GC) elapsed : 29.2% per-line GC/MUT cpu ratio: median 0.489, p90 1.099 per-line GC/MUT elapsed ratio: median 0.367, p90 0.806 ``` Mutator time is roughly in the same ballpark, but GC CPU time has reduced by 18.22%, and mutator productivity has increased from 63.5% to 67.8%. - - - - - 8372e13d by Cheng Shao at 2026-01-18T10:02:12-05:00 rts: remove unused .def files from rts/win32 This patch removes unused .def files from `rts/win32`, given we don't build .dll files for rts/ghc-internal/ghc-prim at all. Even when we resurrect win32 dll support at some point in the future, these .def files still contain incorrect symbols anyway and won't be of any use. - - - - - f6af485d by Cheng Shao at 2026-01-18T10:03:19-05:00 .gitmodules: use gitlab mirror for the libffi-clib submodule This patch fixes .gitmodules to use the gitlab mirror for the libffi-clib submodule, to make it coherent with other submodules that allow ghc developers to experiment with wip branches in submodules for ghc patches. Fixes #26783. - - - - - 41432d25 by Cheng Shao at 2026-01-18T10:05:13-05:00 hadrian: remove the horrible i386 speedHack When hadrian builds certain rts objects for i386, there's a horrible speedHack that forces -fno-PIC even for dynamic ways of those objects. This is not compatible with newer versions of gcc/binutils as well as clang/lld, and this patch removes it. Fixes #26792. - - - - - 323eb8f0 by Cheng Shao at 2026-01-18T21:48:19-05:00 hadrian: enable split sections for cross stage0 This patch fixes a minor issue with `splitSectionsArgs` in hadrian: previously, it's unconditionally disabled for stage0 libraries because it's not going to be shipped in the final bindists. But it's only true when not cross compiling. So for now we also need to enable it for cross stage0 as well. - - - - - 3fadfefe by Andreas Klebinger at 2026-01-18T21:49:01-05:00 RTS: Document -K behaviour better - - - - - 30f442a9 by Teo Camarasu at 2026-01-20T13:57:26-05:00 base: don't expose GHC.Num.{BigNat, Integer, Natural} We no longer expose GHC.Num.{BigNat, Integer, Natural} from base instead users should get these modules from ghc-bignum. We make this change to insulate end users from changes to GHC's implementation of big numbers. Implements CLC proposal 359: https://github.com/haskell/core-libraries-committee/issues/359 - - - - - 75a9053d by Teo Camarasu at 2026-01-20T13:58:07-05:00 base: deprecate GHC internals in GHC.Num Implements CLC proposal: https://github.com/haskell/core-libraries-committee/issues/360 - - - - - 9534b032 by Andreas Klebinger at 2026-01-20T13:58:50-05:00 ghc-experimental: Update Changelog I tried to reconstruct a high level overview of the changes and when they were made since we introduced it. Fixes #26506 Co-authored-by: Teo Camarasu <teofilcamarasu(a)gmail.com> - - - - - 346f2f5a by Cheng Shao at 2026-01-20T13:59:30-05:00 hadrian: remove RTS options in ghc-in-ghci flavour This patch removes the RTS options passed to ghc in ghc-in-ghci flavour, to workaround command line argument handling issue in hls/hie-boot that results in `-O64M` instead of `+RTS -O64M -RTS` being passed to ghc. It's not a hadrian bug per se, since ghc's own ghc-in-ghci multi repl works fine, but we should still make sure HLS works. Closes #26801. - - - - - 759fd15a by Andreas Klebinger at 2026-01-21T16:05:28-05:00 Don't build GHC with -Wcompat Without bumping the boot compiler the warnings it produces are often not actionable leading to pointless noise. Fixes #26800 - - - - - 3172db94 by Torsten Schmits at 2026-01-21T16:06:11-05:00 Use the correct field of ModOrigin when formatting error message listing hidden reexports - - - - - 485c12b2 by Cheng Shao at 2026-01-21T16:06:54-05:00 Revert "hadrian: handle findExecutable "" gracefully" This reverts commit 1e5752f64a522c4025365856d92f78073a7b3bba. The underlying issue has been fixed in https://github.com/haskell/directory/commit/75828696e7145adc09179111a0d631b… and present since 1.3.9.0, and hadrian directory lower bound is 1.3.9.0, so we can revert our own in house hack now. - - - - - 5efb58dc by Cheng Shao at 2026-01-21T16:07:36-05:00 rts: fix typo in TICK_ALLOC_RTS This patch fixes a typo in the `TICK_ALLOC_RTS` macro, the original `bytes` argument was silently dropped. The Cmm code has its own version of `TICK_ALLOC_RTS` not affected by this typo, it affected the C RTS, and went unnoticed because the variable `n` happened to also be available at its call site. But the number was incorrect. Also fixes its call site since `WDS()` is not available in C. - - - - - c406ea69 by Cheng Shao at 2026-01-21T16:07:36-05:00 rts: remove broken & unused ALLOC_P_TICKY This patch removes the `ALLOC_P_TICKY` macro from the rts, it's unused, and its expanded code is already broken. - - - - - 34a27e20 by Simon Peyton Jones at 2026-01-21T16:08:17-05:00 Make the implicit-parameter class have representational role This MR addresses #26737, by making the built-in class IP have a representational role for its second parameter. See Note [IP: implicit parameter class] in ghc-internal:GHC.Internal.Classes.IP In fact, IP is (unfortunately, currently) exposed by base:GHC.Base, so we ran a quick CLC proposal to agree the change: https://github.com/haskell/core-libraries-committee/issues/385 Some (small) compilations get faster because they only need to load (small) interface file GHC.Internal.Classes.IP.hi, rather than (large) GHC.Internal.Classes.hi. Metric Decrease: T10421 T12150 T12425 T24582 T5837 T5030 - - - - - ca79475f by Cheng Shao at 2026-01-21T16:09:00-05:00 testsuite: avoid re.sub in favor of simple string replacements This patch refactors the testsuite driver and avoids the usage of re.sub in favor of simple string replacements when possible. The changes are not comprehensive, and there are still a lot of re.sub usages lingering around the tree, but this already addresses a major performance bottleneck in the testsuite driver that might has to do with quadratic or worse slowdown in cpython's regular expression engine when handling certain regex patterns with large strings. Especially on i386, and i386 jobs are the bottlenecks of all full-ci validate pipelines! Here are the elapsed times of testing x86_64/i386 with -j48 before this patch: x86_64: `Build completed in 6m06s` i386: `Build completed in 1h36m` And with this patch: x86_64: `Build completed in 4m55s` i386: `Build completed in 4m23s` Fixes #26786. Co-authored-by: Codex <codex(a)openai.com> - - - - - 88c93796 by Zubin Duggal at 2026-01-21T16:09:42-05:00 ghc-toolchain: Also configure windres on non-windows platforms. It may be needed for cross compilation. Fixes #24588 - - - - - 9788c0ec by Cheng Shao at 2026-01-21T16:10:24-05:00 ghci: print external interpreter trace messages to stderr instead of stdout This patch makes ghci print external interpreter trace messages to stderr instead of stdout, which is a much saner choice for diagnostic information. Closes #26807. - - - - - 0491f08a by Sylvain Henry at 2026-01-22T03:44:26-05:00 GC: don't use CAS without PARALLEL_GC on If we're not using the parallel GC, there is no reason to do a costly CAS. This was flagged as taking time in a perf profile. - - - - - 211a8f56 by Sylvain Henry at 2026-01-22T03:44:26-05:00 GC: suffix parallel GC with "par" instead of "thr" Avoid some potential confusion (see discussion in !15351). - - - - - 77a23cbd by fendor at 2026-01-22T03:45:08-05:00 Remove blanket ignore that covers libraries/ - - - - - 18bf7f5c by Léana Jiang at 2026-01-22T08:58:45-05:00 doc: update Flavour type in hadrian user-settings - - - - - 3d5a1365 by Cheng Shao at 2026-01-22T08:59:28-05:00 hadrian: add missing notCross predicate for stage0 -O0 There are a few hard-coded hadrian args that pass -O0 when compiling some heavy modules in stage0, which only makes sense when not cross-compiling and when cross-compiling we need properly optimized stage0 packages. So this patch adds the missing `notCross` predicate in those places. - - - - - ee937134 by Matthew Pickering at 2026-01-22T09:00:10-05:00 Fix ghc-experimental GHC.Exception.Backtrace.Experimental module This module wasn't added to the cabal file so it was never compiled or included in the library. - - - - - 1b490f5a by Zubin Duggal at 2026-01-22T09:00:53-05:00 hadrian: Add ghc-{experimental,internal}.cabal to the list of dependencies of the doc target We need these files to detect the version of these libraries Fixes #26738 - - - - - cdb74049 by Cheng Shao at 2026-01-22T14:52:36-05:00 rts: avoid Cmm loop to initialize Array#/SmallArray# Previously, `newArray#`/`newSmallArray#` called an RTS C function to allocate the `Array#`/`SmallArray#`, then used a Cmm loop to initialize the elements. Cmm doesn't have native for-loop so the code is a bit awkward, and it's less efficient than a C loop, since the C compiler can effectively vectorize the loop with optimizations. So this patch moves the loop that initializes the elements to the C side. `allocateMutArrPtrs`/`allocateSmallMutArrPtrs` now takes a new `init` argument and initializes the elements if `init` is non-NULL. - - - - - 4c784f00 by Cheng Shao at 2026-01-22T14:53:19-05:00 Fix testsuite run for +ipe flavour transformer This patch makes the +ipe flavour transformer pass the entire testsuite: - An RTS debug option `-DI` is added, the IPE trace information is now only printed with `-DI`. The test cases that do require IPE trace are now run with `-DI`. - The testsuite config option `ghc_with_ipe` is added, enabled when running the testsuite with `+ipe`, which skips a few tests that are sensitive to eventlog output, allocation patterns etc that can fail under `+ipe`. This is the first step towards #26799. Co-authored-by: Codex <codex(a)openai.com> - - - - - be8e5236 by Ben Gamari at 2026-01-23T03:28:45-05:00 hadrian: Bump QuickCheck upper bound This patch bumps QuickCheck upper bound to 2.18. selftest rule manually tested to work with current latest QuickCheck-2.17.1.0. - - - - - 5aa328fb by Zubin Duggal at 2026-01-23T03:29:30-05:00 Add genindex to index.rst. This adds a link to the index in the navigation bar. Fixes #26437 - - - - - 917ab8ff by Oleg Grenrus at 2026-01-23T10:52:55-05:00 Export labelThread from Control.Concurrent - - - - - 3f5e8d80 by Cheng Shao at 2026-01-23T10:53:37-05:00 ci: only push perf notes on master/release branches This patch fixes push_perf_notes logic in ci.sh to only push perf notes on master/release branches. We used to unconditionally push perf notes even in MRs, but the perf numbers in the wip branches wouldn't be used as baseline anyway, plus this is causing a space leak in the ghc-performance-notes repo. See #25317 for the perf notes repo size problem. Co-authored-by: Codex <codex(a)openai.com> - - - - - 414b9593 by Cheng Shao at 2026-01-24T07:11:51-05:00 ci: remove duplicate keys in .gitlab-ci.yml This patch removes accidentally duplicate keys in `.gitlab-ci.yml`. The YAML spec doesn't allow duplicate keys in the first place, and according to GitLab docs (https://docs.gitlab.com/ci/yaml/yaml_optimization/#anchors) the latest key overrides the earlier entries. - - - - - e5cb5491 by Cheng Shao at 2026-01-24T07:12:34-05:00 hadrian: drop obsolete configure/make builder logic for libffi This patch drops obsolete hadrian logic around `Configure libffiPath`/`Make libffiPath` builders, they are no longer needed after libffi-clib has landed. Closes #26815. - - - - - 2d160222 by Simon Hengel at 2026-01-24T07:13:17-05:00 Fix typo in roles.rst - - - - - 56db94f7 by Peter Trommler at 2026-01-26T11:26:18+01:00 PPC NCG: Generate clear right insn at arch width The clear right immediate (clrrxi) is only available in word and doubleword width. Generate clrrxi instructions at architecture width for all MachOp widths. Fixes #24145 - - - - - 5957a8ad by Wolfgang Jeltsch at 2026-01-27T06:11:40-05:00 Add operations for obtaining operating-system handles This contribution implements CLC proposal #369. It adds operations for obtaining POSIX file descriptors and Windows handles that underlie Haskell handles. Those operating system handles can also be obtained without such additional operations, but this is more involved and, more importantly, requires using internals. - - - - - 86a0510c by Greg Steuck at 2026-01-27T06:12:34-05:00 Move flags to precede patterns for grep and read files directly This makes the tests pass with non-GNU (i.e. POSIX-complicant) tools. There's no reason to use cat and pipe where direct file argument works. - - - - - 50761451 by Cheng Shao at 2026-01-27T21:51:23-05:00 ci: update darwin boot ghc to 9.10.3 This patch updates darwin boot ghc to 9.10.3, along with other related updates, and pays off some technical debt here: - Update `nixpkgs` and use the `nixpkgs-25.05-darwin` channel. - Update the `niv` template. - Update LLVM to 21 and update `llvm-targets` to reflect LLVM 21 layout changes for arm64/x86_64 darwin targets. - Use `stdenvNoCC` to prevent nix packaged apple sdk from being used by boot ghc, and manually set `DEVELOPER_DIR`/`SDKROOT` to enforce the usage of system-wide command line sdk for macos. - When building nix derivation for boot ghc, run `configure` via the `arch` command so that `configure` and its subprocesses pick up the manually specified architecture. - Remove the previous horrible hack that obliterates `configure` to make autoconf test result in true. `configure` now properly does its job. - Remove the now obsolete configure args and post install settings file patching logic. - Use `scheme-small` for texlive to avoid build failures in certain unused texlive packages, especially on x86_64-darwin. - - - - - 94dcd15e by Matthew Pickering at 2026-01-27T21:52:05-05:00 Evaluate backtraces for "error" exceptions at the moment they are thrown See Note [Capturing the backtrace in throw] and Note [Hiding precise exception signature in throw] which explain the implementation. This commit makes `error` and `throw` behave the same with regard to backtraces. Previously, exceptions raised by `error` would not contain useful IPE backtraces. I did try and implement `error` in terms of `throw` but it started to involve putting diverging functions into hs-boot files, which seemed to risky if the compiler wouldn't be able to see if applying a function would diverge. CLC proposal: https://github.com/haskell/core-libraries-committee/issues/383 Fixes #26751 - - - - - ef35e3ea by Teo Camarasu at 2026-01-27T21:52:46-05:00 ghc-internal: move all Data instances to Data.Data Most instances of Data are defined in GHC.Internal.Data.Data. Let's move all remaining instance there. This moves other modules down in the dependency hierarchy allowing for more parallelism, and it decreases the likelihood that we would need to load this heavy .hi file if we don't actually need it. Resolves #26830 Metric Decrease: T12227 T16875 - - - - - 5e0ec555 by sheaf at 2026-01-28T06:56:38-05:00 Add test case for #25679 This commit adds the T25679 test case. The test now passes, thanks to commit 1e53277af36d3f0b6ad5491f70ffc5593a49dcfd. Fixes #25679 - - - - - f1cd1611 by sheaf at 2026-01-28T06:56:38-05:00 Improve defaulting of representational equalities This commit makes the defaulting of representational equalities, introduced in 1e53277a, a little bit more robust. Now, instead of calling the eager unifier, it calls the full-blown constraint solver, which means that it can handle some subtle situations, e.g. involving functional dependencies and type-family injectivity annotations, such as: type family F a = r | r -> a type instance F Int = Bool [W] F beta ~R Bool - - - - - 25edf516 by sheaf at 2026-01-28T06:56:38-05:00 Improve errors for unsolved representational equalities This commit adds a new field of CtLoc, CtExplanations, which allows the typechecker to leave some information about what it has done. For the moment, it is only used to improve error messages for unsolved representational equalities. The typechecker will now accumulate, when unifying at representational role: - out-of-scope newtype constructors, - type constructors that have nominal role in a certain argument, - over-saturated type constructors, - AppTys, e.g. `c a ~R# c b`, to report that we must assume that 'c' has nominal role in its parameters, - data family applications that do not reduce, potentially preventing newtype unwrapping. Now, instead of having to re-construct the possible errors after the fact, we simply consult the CtExplanations field. Additionally, this commit modifies the typechecker error messages that concern out-of-scope newtype constructors. The error message now depends on whether we have an import suggestion to provide to the user: - If we have an import suggestion for the newtype constructor, the message will be of the form: The data constructor MkN of the newtype N is out of scope Suggested fix: add 'MkN' to the import list in the import of 'M' - If we don't have any import suggestions, the message will be of the form: NB: The type 'N' is an opaque newtype, whose constructor is hidden Fixes #15850, #20289, #20468, #23731, #25949, #26137 - - - - - 4d0e6da1 by Simon Peyton Jones at 2026-01-28T06:57:19-05:00 Fix two bugs in short-cut constraint solving There are two main changes here: * Use `isSolvedWC` rather than `isEmptyWC` in `tryShortCutSolver` The residual constraint may have some fully-solved, but still-there implications, and we don't want them to abort short cut solving! That bug caused #26805. * In the short-cut solver, we abandon the fully-solved residual constraint; but we may thereby lose track of Givens that are needed, and either report them as redundant or prune evidence bindings that are in fact needed. This bug stopped the `constraints` package from compiling; see the trail in !15389. The second bug led me to (another) significant refactoring of the mechanism for tracking needed EvIds. See the new Note [Tracking needed EvIds] in GHC.Tc.Solver.Solve It's simpler and much less head-scratchy now. Some particulars: * An EvBindsVar now tracks NeededEvIds * We deal with NeededEvIds for an implication only when it is fully solved. Much simpler! * `tryShortCutTcS` now takes a `TcM WantedConstraints` rather than `TcM Bool`, so that is can plumb the needed EvIds correctly. * Remove `ic_need` and `ic_need_implic` from Implication (hooray), and add `ics_dm` and `ics_non_dm` to `IC_Solved`. Pure refactor * Shorten data constructor `CoercionHole` to `CH`, following general practice in GHC. * Rename `EvBindMap` to `EvBindsMap` for consistency - - - - - 662480b7 by Cheng Shao at 2026-01-28T06:58:00-05:00 ci: use debian validate bindists instead of fedora release bindists in testing stage This patch changes the `abi-test`, `hadrian-multi` and `perf` jobs in the full-ci pipeline testing stage to use debian validate bindists instead of fedora release bindists, to increase pipeline level parallelism and allow full-ci pipelines to complete earlier. Closes #26818. - - - - - 39581ec6 by Cheng Shao at 2026-01-28T06:58:40-05:00 ci: run perf test with -j$cores This patch makes the perf ci job compile Cabal with -j$cores to speed up the job. - - - - - 607b287b by Wolfgang Jeltsch at 2026-01-28T15:41:53+02:00 Remove `GHC.Desugar` from `base` `GHC.Desugar` was deprecated and should have been removed in GHC 9.14. However, the removal was forgotten, although there was a code block that was intended to trigger a compilation error when the GHC version in use was 9.14 or later. This code sadly didn’t work, because the `__GLASGOW_HASKELL__` macro was misspelled as `__GLASGOW_HASKELL`. - - - - - e8f5a45d by sterni at 2026-01-29T04:19:18-05:00 users_guide: fix runtime error during build with Sphinx 9.1.0 Appears that pathto is stricter about what it accepts now. Tested Sphinx 8.2.3 and 9.1.0 on the ghc-9.10 branch. Resolves #26810. Co-authored-by: Martin Weinelt <hexa(a)darmstadt.ccc.de> - - - - - ce2d62fb by Jessica Clarke at 2026-01-29T19:48:51-05:00 PPC NCG: Use libcall for 64-bit cmpxchg on 32-bit PowerPC There is no native instruction for this, and even if there were a register pair version we could use, the implementation here is assuming the values fit in a single register, and we end up only using / defining the low halves of the registers. Fixes: b4d39adbb5 ("PrimOps: Add CAS op for all int sizes") Fixes: #23969 - - - - - 43d97761 by Michael Karcher at 2026-01-29T19:49:43-05:00 NCG for PPC: add pattern for CmmRegOff to iselExpr64 Closes #26828 - - - - - aeeb4a20 by Matthew Pickering at 2026-01-30T11:42:47-05:00 determinism: Use deterministic map for Strings in TyLitMap When generating typeable evidence the types we need evidence for all cached in a TypeMap, the order terms are retrieved from a type map determines the order the bindings appear in the program. A TypeMap is quite diligent to use deterministic maps, apart from in the TyLitMap, which uses a UniqFM for storing strings, whose ordering depends on the Unique of the FastString. This can cause non-deterministic .hi and .o files. An unexpected side-effect is the error message but RecordDotSyntaxFail8 changing. I looked into this with Sam and this change caused the constraints to be solved in a different order which results in a slightly different error message. I have accepted the new test, since the output before was non-deterministic and the new output is consistent with the other messages in that file. Fixes #26846 - - - - - 9e4d70c2 by Andrew Lelechenko at 2026-01-30T11:43:29-05:00 Upgrade text submodule to 2.1.4 - - - - - 631fa5ae by Recursion Ninja at 2026-01-31T22:30:11+00:00 Decouple `L.S.H.Decls` from importing `GHC.Types.Basic` Data-types within `GHC.Types.Basic` which describe components of the AST are migrated to `Language.Haskell.Syntax.Basic`. Related function definitions are also moved. Types moved to L.H.S. because they are part of the AST: * TopLevelFlag * RuleName Types moved from L.H.S. to GHC.Hs. because they are not needed in the AST: * TyConFlavour * TypeOrData * NewOrData Migrated instances: * `Outputable` instances moved to in `GHC.Utils.Outputable` * `Binary` instance of `Boxity` moved to to `GHC.Utils.Binary` * Other `Binary` instances are orphans to be migrated later. The `OverlapMode` data-type is given a TTG extension point. The `OverlapFlag` data-type, which depends on `OverlapMode`, is updated to support `OverlapMode` with a GHC "pass" type paramerter. In order to avoid module import cycles, `OverlapMode` and `OverlapFlag` are migrated to new modules (no way around this). * Migrated `OverlapMode` to new module `Language.Haskell.Syntax.Overlap` * Migrated `OverlapFlag` to new module `GHC.Hs.Decls.Overlap` - - - - - 9769cc03 by Simon Hengel at 2026-02-01T04:21:03-05:00 Update the documentation for MultiWayIf (fixes #25376) (so that it matches the implementation) - - - - - 5fc9442a by Peter Trommler at 2026-02-01T04:21:44-05:00 hadrian: Fix dependency generation for assembler Assembler files allow # for comments unless in column 1. A modern cpp for C treats those a preprocessor directives. We tell gcc that a .S file is assembler with cpp and not C. Fixes #26819 - - - - - 269c4087 by Simon Peyton Jones at 2026-02-01T19:38:10-05:00 Include current phase in the range for rule/unfoldings This MR fixes a bad loop in the compiler: #26826. The fix is to add (WAR2) to Note [What is active in the RHS of a RULE or unfolding?] in GHC.Core.Opt.Simplify.Utils - - - - - ddf1434f by Vladislav Zavialov at 2026-02-01T19:38:52-05:00 Refactor: merge HsMultilineString into HsString (#26860) Before this patch, HsLit defined two separate constructors to represent single-line and multi-line strings: data HsLit x ... | HsString (XHsString x) FastString | HsMultilineString (XHsMultilineString x) FastString I found this to be an unnecessary complication and an obstacle to unifying HsLit with HsTyLit. Now we use HsString for both kinds of literals. One user-facing change here is `ppr (HsString st s)` behaving differently for single-line strings containing newlines: x = "first line \ \asdf\n\ \second line" Previously, the literal was fed to `ftext` with its newlines, producing an ill-formed SDoc. This issue is now addressed by using `split` for both single-line and multi-line strings: vcat $ map text $ split '\n' (unpackFS src) See the parser/should_fail/T26860ppr test. In addition (and unrelatedly to the main payload of this patch), drop the unused pmPprHsLit helper. - - - - - 2b4f463c by Simon Peyton Jones at 2026-02-02T17:32:32+00:00 Remove exprIsCheap from doFloatFromRhs See #26854 and Note [Float when expandable] This patch simplifies the code, by removing an extra unnecessary test. - - - - - 9db7f21f by Brandon Chinn at 2026-02-03T09:15:10-05:00 Refactor: make function patterns exhaustive Also added missing (==) logic for: * HsMultilineString * HsInt{8,16,32} * HsWord{8,16,32} - - - - - aa9c5e2c by Hécate Kleidukos at 2026-02-03T15:58:35-05:00 driver: Hide source paths at verbosity level 1 by default - - - - - c64cca1e by mangoiv at 2026-02-03T15:59:29-05:00 ExplicitLevelImports: check staging for types just like for values Previously, imported types were entirely exempted from staging checks as the implicit stage persistance assumed to be all imported types to be well staged. ExplicitLevelImports' change specification, however, does not do such an exemption. Thus we want to introduce such a check, just like we have for values. ExplicitLevelImports does not, however, talk about local names - from its perspective, we could theoretically keep treating locally introduced types specially - e.g. an ill-staged used in a quote would only emit a warning, not an error. To allow for a potential future migration away from such wrinkles as the staging check in notFound (see Note [Out of scope might be a staging error]) we consistently do the strict staging check that we also do for value if ExplicitLevelImports is on. Closes #26098 - - - - - 5f0dbeb6 by Simon Hengel at 2026-02-03T16:00:12-05:00 Use Haddock formatting in deprecation message of `initNameCache` - - - - - 01ecb612 by Andreas Klebinger at 2026-02-04T09:56:25-05:00 testsuite: Explicitly use utf-8 encoding in rts-includes linter. Not doing so caused failures on windows, as python failed to pick a reasonable encoding even with locale set. Fixes #26850 - - - - - ea0d1317 by Zubin Duggal at 2026-02-04T09:57:06-05:00 Bump transformers submodule to 0.6.3.0 Fixes #26790 - - - - - cbe4300e by Simon Peyton Jones at 2026-02-05T04:31:04-05:00 Fix subtle bug in GHC.Core.Utils.mkTick This patch fixes a decade-old bug in `mkTick`, which could generate type-incorrect code! See the diagnosis in #26772. The new code is simpler and easier to understand. (As #26772 says, I think it could be improved further.) - - - - - a193a8da by Simon Peyton Jones at 2026-02-05T04:31:04-05:00 Modify a debug-trace in the Simplifier ...just to show a bit more information. - - - - - b579dfdc by Simon Peyton Jones at 2026-02-05T04:31:04-05:00 Fix long-standing interaction between ticks and casts The code for Note [Eliminate Identity Cases] was simply wrong when ticks and casts interacted. This patch fixes the interaction. It was shown up when validating #26772, although it's not the exactly the bug that's reported by #26772. Nor is it easy to reproduce, hence no regression test. - - - - - fac0de1e by Cheng Shao at 2026-02-05T04:31:49-05:00 libraries: bump Cabal submodule to 3.16.1.0 - - - - - 00589122 by Cheng Shao at 2026-02-05T04:31:49-05:00 libraries: bump deepseq submodule to 1.5.2.0 Also: - Get rid of usage of deprecated `NFData` function instance in the compiler - `T21391` still relies on `NFData` function instance, add `-Wno-deprecations` for the time being. - - - - - 84474c71 by Cheng Shao at 2026-02-05T04:31:50-05:00 libraries: bump directory submodule to 1.3.10.1 - - - - - 1a9f4662 by Cheng Shao at 2026-02-05T04:31:50-05:00 libraries: bump exceptions submodule to 0.10.12 - - - - - 2e39a340 by Peng Fan at 2026-02-07T03:42:01-05:00 NCG/LA64: adjust register usage to avoid src-register being clobbered - - - - - 9faf1b35 by Teo Camarasu at 2026-02-07T03:42:43-05:00 ghc-internal: Delete unnecessary GHC.Internal.Data.Ix This module merely re-exports GHC.Internal.Ix. It was copied from `base` when `ghc-internal` was split, but there is no reason to have this now. So, let's delete it. Resolves #26848 - - - - - d112b440 by Sven Tennie at 2026-02-07T10:47:56-05:00 Add cabal.project file to generate-ci This fixes the HLS setup for our CI code generation script (generate-ci). The project file simply makes `generate-ci` of the cabal file discoverable. - - - - - 5339f6f0 by Andreas Klebinger at 2026-02-07T10:48:40-05:00 CI: Don't collapse test results. This puts test output back into the primary test log instead of a subsection removing the need to expand a section to see test results. While the intention was good in practice the old behaviour mostly wastes time by requiring expansion of the section. Fixes #26882 - - - - - 0e1cd2e0 by Evan Piro at 2026-02-08T10:35:16-08:00 Linker.MacOS reduce dynflags import - - - - - 1c79a4cd by Michael Alan Dorman at 2026-02-09T08:11:51-05:00 Remove `extra_src_files` variable from `testsuite/driver/testlib.py` While reading through the test harness code, I noticed this variable with a TODO attached that referenced #12223. Although that bug is closed, it strongly implied that this special-case variable that only affected a single test was expected to be removed at some point. I also looked at 3415bcaa0b1903b5e12dfaadb5b774718e406eab---where it was added---whose commit message suggested that it would have been desirable to remove it, but that there were special circumstances that meant it had to remain (though it doesn't elucidate what those special circumstances are). However, the special circumstances were mentioned as if the test was in a different location than is currently is, so I decided to try changing the test to use the standard `extra_files` mechanism, which works in local testing. This also seems like a reasonable time to remove the script that was originally used in the transition, since it doesn't really serve a purpose anymore. - - - - - 0020e38a by Matthew Pickering at 2026-02-09T17:29:14-05:00 determinism: Use a stable sort in WithHsDocIdentifiers binary instance `WithHsDocIdentifiers` is defined as ``` 71 data WithHsDocIdentifiers a pass = WithHsDocIdentifiers 72 { hsDocString :: !a 73 , hsDocIdentifiers :: ![Located (IdP pass)] 74 } ``` This list of names is populated from `rnHsDocIdentifiers`, which calls `lookupGRE`, which calls `lookupOccEnv_AllNameSpaces`, which calls `nonDetEltsUFM` and returns the results in an order depending on uniques. Sorting the list with a stable sort before returning the interface makes the output deterministic and follows the approach taken by other fields in `Docs`. Fixes #26858 - - - - - 89898ce6 by echoumcp1 at 2026-02-09T17:30:01-05:00 Replace putstrln with logMsg in handleSeqHValueStatus Fixes #26549 - - - - - 7c52c4f9 by John Paul Adrian Glaubitz at 2026-02-10T13:52:43-05:00 rts: Switch prim to use modern atomic compiler builtins The __sync_*() atomic compiler builtins have been deprecated in GCC for a while now and also don't provide variants for 64-bit values such as __sync_fetch_and_add_8(). Thus, replace them with the modern __atomic_*() compiler builtins and while we're at it, also drop the helper macro CAS_NAND() which is now no longer needed since we stopped using the __sync_*() compiler builtins altogether. Co-authored-by: Ilias Tsitsimpis <iliastsi(a)debian.org> Fixes #26729 - - - - - cf60850a by Recursion Ninja at 2026-02-10T13:53:27-05:00 Decoupling L.H.S.Decls from GHC.Types.ForeignCall - Adding TTG extension point for 'CCallTarget' - Adding TTG extension point for 'CType' - Adding TTG extension point for 'Header' - Moving ForeignCall types that do not need extension to new L.H.S.Decls.Foreign module - Replacing 'Bool' parameters with descriptive data-types to increase clairty and prevent "Boolean Blindness" - - - - - 11a04cbb by Eric Lee at 2026-02-11T09:20:46-05:00 Derive Semigroup/Monoid for instances believed could be derived in #25871 - - - - - 15d9ce44 by Eric Lee at 2026-02-11T09:20:46-05:00 add Ghc.Data.Pair deriving - - - - - c85dc170 by Evan Piro at 2026-02-11T09:21:45-05:00 Linker.MacOS reduce options import - - - - - a541dd83 by Chris Wendt at 2026-02-11T16:06:41-05:00 Initialize plugins for `:set +c` in GHCi Fixes #23110. - - - - - 0f5a73bc by Cheng Shao at 2026-02-11T16:07:27-05:00 compiler: add Binary Text instance This patch adds `Binary` instance for strict `Text`, in preparation of making `Text` usable in certain GHC API use cases (e.g. haddock). This also introduces `text` as a direct dependency of the `ghc` package. - - - - - 9e58b8a1 by Cheng Shao at 2026-02-11T16:08:10-05:00 ghc-toolchain: add C11 check This patch partially reverts commit b8307eab80c5809df5405d76c822bf86877f5960 that removed C99 check in autoconf/ghc-toolchain. Now we: - No longer re-implement `FP_SET_CFLAGS_C11` similar to `FP_SET_CFLAGS_C99` in the past, since autoconf doesn't provide a convenient `AC_PROG_CC_C11` function. ghc-toolchain will handle it anyway. - The Cmm CPP C99 check is relanded and repurposed for C11. - The C99 logic in ghc-toolchain is relanded and repurposed for C11. - The C99 check in Stg.h is corrected to check for C11. The obsolete _ISOC99_SOURCE trick is dropped. - Usages of `-std=gnu99` in the testsuite are corrected to use `-std=gnu11`. Closes #26908. - - - - - 4df0adf6 by Simon Peyton Jones at 2026-02-11T21:50:13-05:00 Simplify the treatment of static forms This MR implements GHC proposal 732: simplify static forms, https://github.com/ghc-proposals/ghc-proposals/pull/732 thereby addressing #26556. See `Note [Grand plan for static forms]` in GHC.Iface.Tidy.StaticPtrTable The main changes are: * There is a new, simple rule for (static e), namely that the free term variables of `e` must be bound at top level. The check is done in the `HsStatic` case of `GHC.Rename.Expr.rnExpr` * That in turn substantially simplifies the info that the typechecker carries around in its type environment. Hooray. * The desugarer emits static bindings to top level directly; see the `HsStatic` case of `dsExpr`. * There is no longer any special static-related magic in the FloatOut pass. And the main Simplifier pipeline no longer needs a special case to run FloatOut even with -O0. Hooray. All this forced an unexpected change to the pattern match checker. It recursively invokes the main Hs desugarer when it wants to take a look at a term to spot some special cases (notably constructor applications). We don't want to emit any nested (static e) bindings to top level a second time! Yikes. That forced a modest refactor in GHC.HsToCore.Pmc: * The `dsl_nablas` field of `DsLclEnv` now has a `NoPmc` case, which says "I'm desugaring just for pattern-match checking purposes". * When that flag is set we don't emit static binds. That in turn forces a cascade of refactoring, but the net effect is an improvement; less risk of duplicated (even exponential?) work. See Note [Desugaring HsExpr during pattern-match checking]. 10% metric decrease, on some architectures, of compile-time max-bytes-used on T15304. Metric Decrease: T15304 - - - - - 7922f728 by Teo Camarasu at 2026-02-11T21:50:58-05:00 ghc-internal: avoid depending on GHC.Internal.Exts This module is mostly just re-exports. It made sense as a user-facing module, but there's no good reason ghc-internal modules should depend on it and doing so linearises the module graph - move considerAccessible to GHC.Internal.Magic Previously it lived in GHC.Internal.Exts, but it really deserves to live along with the other magic function, which are already re-exported from .Exts - move maxTupleSize to GHC.Internal.Tuple This previously lived in GHC.Internal.Exts but a comment already said it should be moved to .Tuple Resolves #26832 - - - - - b6a4a29b by Eric Lee at 2026-02-11T21:51:55-05:00 Remove unused Semigroup imports to fix GHC 9.14 bootstrapping - - - - - f3106625 by Cheng Shao at 2026-02-12T21:48:49+00:00 rts: add is-valid-utf8.c to .ubsan-suppressions A minor one in `bytestring` that might surface when building with +ubsan using clang. - - - - - 6a8fe33e by Cheng Shao at 2026-02-12T21:48:49+00:00 hadrian: add support for building with AddressSanitizer This patch adds a +asan flavour transformer to hadrian to build all stage1+ C/C++ code with AddressBehaviorSanitizer. This is particularly useful to catch potential out-of-bounds and use-after-free bugs in the RTS codebase. - - - - - 65c215de by Cheng Shao at 2026-02-12T21:48:49+00:00 ci: add ubsan+asan job We now have a `x86_64-linux-fedora43-quick-validate+debug_info+ubsan+asan` validate/nightly job with both UBSan/ASan enabled. This is enabled in full-ci pipelines as well as MR pipelines with `test-sanitizer` label. - - - - - 7fc5f49a by Cheng Shao at 2026-02-12T21:48:50+00:00 rts: add ASAN instrumentation to mblock allocator - - - - - 28902a4d by Cheng Shao at 2026-02-12T21:48:50+00:00 rts: add ASAN instrumentation to mgroup allocator - - - - - ad906baa by Cheng Shao at 2026-02-12T21:48:50+00:00 rts: add ASAN instrumentation to block allocator - - - - - 79c1ac58 by Cheng Shao at 2026-02-12T21:48:50+00:00 rts: add ASAN instrumentation to cap->pinned_object_empty - - - - - 15be2598 by Cheng Shao at 2026-02-12T21:48:50+00:00 rts: add ASAN instrumentation to gc_thread->free_blocks - - - - - 5fb86b6c by Cheng Shao at 2026-02-12T21:48:50+00:00 rts: add ASAN instrumentation to hash table free list - - - - - 28747c0e by Cheng Shao at 2026-02-12T21:48:50+00:00 rts: add ASAN instrumentation to per-Task InCall free list - - - - - 9c86f5e5 by Cheng Shao at 2026-02-12T21:48:50+00:00 WIP - - - - - 542 changed files: - .gitignore - .gitlab-ci.yml - .gitlab/ci.sh - .gitlab/darwin/nix/sources.json - .gitlab/darwin/toolchain.nix - + .gitlab/generate-ci/cabal.project - .gitlab/generate-ci/gen_ci.hs - + .gitlab/issue_templates/get-verified.md - .gitlab/jobs.yaml - .gitmodules - CODEOWNERS - cabal.project-reinstall - compiler/GHC/Builtin/Names.hs - compiler/GHC/Builtin/Types.hs - compiler/GHC/CmmToAsm/Config.hs - compiler/GHC/CmmToAsm/LA64/CodeGen.hs - compiler/GHC/CmmToAsm/PPC/CodeGen.hs - compiler/GHC/CmmToAsm/Reg/Linear.hs - compiler/GHC/CmmToAsm/Reg/Linear/StackMap.hs - compiler/GHC/CmmToAsm/X86/CodeGen.hs - compiler/GHC/CmmToLlvm.hs - compiler/GHC/CmmToLlvm/Base.hs - compiler/GHC/CmmToLlvm/CodeGen.hs - compiler/GHC/Core/Coercion.hs - compiler/GHC/Core/FamInstEnv.hs - compiler/GHC/Core/InstEnv.hs - compiler/GHC/Core/Lint.hs - compiler/GHC/Core/Map/Type.hs - compiler/GHC/Core/Opt/Arity.hs - compiler/GHC/Core/Opt/OccurAnal.hs - compiler/GHC/Core/Opt/Pipeline.hs - compiler/GHC/Core/Opt/SetLevels.hs - compiler/GHC/Core/Opt/Simplify/Env.hs - 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compiler/GHC/Hs/Binds.hs - compiler/GHC/Hs/Decls.hs - + compiler/GHC/Hs/Decls/Overlap.hs - compiler/GHC/Hs/Doc.hs - compiler/GHC/Hs/Expr.hs - compiler/GHC/Hs/Instances.hs - compiler/GHC/Hs/Lit.hs - compiler/GHC/Hs/Syn/Type.hs - compiler/GHC/Hs/Type.hs - compiler/GHC/Hs/Utils.hs - compiler/GHC/HsToCore.hs - compiler/GHC/HsToCore/Docs.hs - compiler/GHC/HsToCore/Errors/Types.hs - compiler/GHC/HsToCore/Expr.hs - compiler/GHC/HsToCore/Foreign/C.hs - compiler/GHC/HsToCore/Foreign/Call.hs - compiler/GHC/HsToCore/Foreign/Decl.hs - compiler/GHC/HsToCore/Foreign/JavaScript.hs - compiler/GHC/HsToCore/Foreign/Utils.hs - compiler/GHC/HsToCore/Foreign/Wasm.hs - compiler/GHC/HsToCore/GuardedRHSs.hs - compiler/GHC/HsToCore/Match.hs - compiler/GHC/HsToCore/Match/Literal.hs - compiler/GHC/HsToCore/Monad.hs - compiler/GHC/HsToCore/Pmc.hs - compiler/GHC/HsToCore/Pmc/Desugar.hs - compiler/GHC/HsToCore/Pmc/Solver.hs - compiler/GHC/HsToCore/Pmc/Solver/Types.hs - compiler/GHC/HsToCore/Quote.hs - compiler/GHC/HsToCore/Ticks.hs - compiler/GHC/HsToCore/Types.hs - compiler/GHC/Iface/Ext/Ast.hs - compiler/GHC/Iface/Syntax.hs - compiler/GHC/Iface/Tidy.hs - compiler/GHC/Iface/Tidy/StaticPtrTable.hs - compiler/GHC/Linker/Loader.hs - compiler/GHC/Linker/MacOS.hs - compiler/GHC/Linker/Unit.hs - compiler/GHC/Parser.y - compiler/GHC/Parser/PostProcess.hs - compiler/GHC/Parser/PostProcess/Haddock.hs - compiler/GHC/Parser/String.hs - compiler/GHC/Rename/Bind.hs - compiler/GHC/Rename/Env.hs - compiler/GHC/Rename/Expr.hs - compiler/GHC/Rename/HsType.hs - compiler/GHC/Rename/Module.hs - compiler/GHC/Rename/Names.hs - compiler/GHC/Rename/Splice.hs - compiler/GHC/Rename/Splice.hs-boot - compiler/GHC/Rename/Unbound.hs - compiler/GHC/Runtime/Heap/Inspect.hs - compiler/GHC/Runtime/Interpreter.hs - compiler/GHC/Runtime/Interpreter/Init.hs - compiler/GHC/Settings/IO.hs - compiler/GHC/Stg/EnforceEpt.hs - compiler/GHC/Stg/Lint.hs - compiler/GHC/StgToByteCode.hs - compiler/GHC/StgToCmm/Closure.hs - compiler/GHC/StgToCmm/Expr.hs - compiler/GHC/StgToCmm/Foreign.hs - 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[Git][ghc/ghc][wip/terrorjack/asan] 29 commits: Support statically linking executables properly
by Cheng Shao (＠TerrorJack) 12 Feb '26

12 Feb '26

Cheng Shao pushed to branch wip/terrorjack/asan at Glasgow Haskell Compiler / GHC Commits: 1ac1a541 by Julian Ospald at 2026-01-09T02:48:53-05:00 Support statically linking executables properly Fixes #26434 In detail, this does a number of things: * Makes GHC aware of 'extra-libraries-static' (this changes the package database format). * Adds a switch '-static-external' that will honour 'extra-libraries-static' to link external system dependencies statically. * Adds a new field to settings/targets: "ld supports verbatim namespace". This field is used by '-static-external' to conditionally use '-l:foo.a' syntax during linking, which is more robust than trying to find the absolute path to an archive on our own. * Adds a switch '-fully-static' that is meant as a high-level interface for e.g. cabal. This also honours 'extra-libraries-static'. This also attempts to clean up the confusion around library search directories. At the moment, we have 3 types of directories in the package database format: * library-dirs * library-dirs-static * dynamic-library-dirs However, we only have two types of linking: dynamic or static. Given the existing logic in 'mungeDynLibFields', this patch assumes that 'library-dirs' is really just nothing but a fallback and always prefers the more specific variants if they exist and are non-empty. Conceptually, we should be ok with even just one search dirs variant. Haskell libraries are named differently depending on whether they're static or dynamic, so GHC can conveniently pick the right one depending on the linking needs. That means we don't really need to play tricks with search paths to convince the compiler to do linking as we want it. For system C libraries, the convention has been anyway to place static and dynamic libs next to each other, so we need to deal with that issue anyway and it is outside of our control. But this is out of the scope of this patch. This patch is backwards compatible with cabal. Cabal should however be patched to use the new '-fully-static' switch. - - - - - ad3c808d by Julian Ospald at 2026-01-09T02:48:53-05:00 Warn when "-dynamic" is mixed with "-staticlib" - - - - - 322dd672 by Matthew Pickering at 2026-01-09T02:49:35-05:00 rts: Use INFO_TABLE_CONSTR for stg_dummy_ret_closure Since the closure type is CONSTR_NOCAF, we need to use INFO_TABLE_CONSTR to populate the constructor description field (this crashes ghc-debug when decoding AP_STACK frames sometimes) Fixes #26745 - - - - - 039bac4c by Ben Gamari at 2026-01-09T20:22:16-05:00 ghc-internal: Move STM utilities out of GHC.Internal.Conc.Sync This is necessary to avoid an import cycle on Windows when importing `GHC.Internal.Exception.Context` in `GHC.Internal.Conc.Sync`. On the road to address #25365. - - - - - 8c389e8c by Ben Gamari at 2026-01-09T20:22:16-05:00 base: Capture backtrace from throwSTM Implements core-libraries-committee#297. Fixes #25365. - - - - - e1ce1fc3 by Ben Gamari at 2026-01-09T20:22:16-05:00 base: Annotate rethrown exceptions in catchSTM with WhileHandling Implements core-libraries-committee#298 - - - - - c4ebdbdf by Cheng Shao at 2026-01-09T20:23:06-05:00 compiler: make getPrim eagerly evaluate its result This commit makes `GHC.Utils.Binary.getPrim` eagerly evaluate its result, to avoid accidental laziness when future patches build other binary parsers using `getPrim`. - - - - - 66a0c4f7 by Cheng Shao at 2026-01-09T20:23:06-05:00 compiler: implement fast get/put for Word16/Word32/Word64 Previously, `GHC.Utils.Binary` contains `get`/`put` functions for `Word16`/`Word32`/`Word64` which always loads and stores them as big-endian words at a potentially unaligned address. The previous implementation is based on loads/stores of individual bytes and concatenating bytes with bitwise operations, which currently cannot be fused to a single load/store operation by GHC. This patch implements fast `get`/`put` functions for `Word16`/`Word32`/`Word64` based on a single memory load/store, with an additional `byteSwap` operation on little-endian hosts. It is based on unaligned load/store primops added since GHC 9.10, and we already require booting with at least 9.10, so it's about time to switch to this faster path. - - - - - 641ec3f0 by Simon Peyton Jones at 2026-01-09T20:23:55-05:00 Fix scoping errors in specialisation Using -fspecialise-aggressively in #26682 showed up a couple of subtle errors in the type-class specialiser. * dumpBindUDs failed to call `deleteCallsMentioning`, resulting in a call that mentioned a dictionary that was not in scope. This call has been missing since 2009! commit c43c981705ec33da92a9ce91eb90f2ecf00be9fe Author: Simon Peyton Jones <simonpj(a)microsoft.com> Date: Fri Oct 23 16:15:51 2009 +0000 Fixed by re-combining `dumpBindUDs` and `dumpUDs`. * I think there was another bug involving the quantified type variables in polymorphic specialisation. In any case I refactored `specHeader` and `spec_call` so that the former looks for the extra quantified type variables rather than the latter. This is quite a worthwhile simplification: less code, easier to grok. Test case in simplCore/should_compile/T26682, brilliantly minimised by @sheaf. - - - - - 2433e91d by Cheng Shao at 2026-01-09T20:24:43-05:00 compiler: change sectionProtection to take SectionType argument This commit changes `sectionProtection` to only take `SectionType` argument instead of whole `Section`, since it doesn't need the Cmm section content anyway, and it can then be called in parts of NCG where we only have a `SectionType` in scope. - - - - - e5926fbe by Cheng Shao at 2026-01-09T20:24:43-05:00 compiler: change isInitOrFiniSection to take SectionType argument This commit changes `isInitOrFiniSection` to only take `SectionType` argument instead of whole `Section`, since it doesn't need the Cmm section content anyway, and it can then be called in parts of NCG where we only have a `SectionType` in scope. Also marks it as exported. - - - - - 244d57d7 by Cheng Shao at 2026-01-09T20:24:43-05:00 compiler: fix split sections on windows This patch fixes split sections on windows by emitting the right COMDAT section header in NCG, see added comment for more explanation. Fix #26696 #26494. ------------------------- Metric Decrease: LargeRecord T9675 size_hello_artifact size_hello_artifact_gzip size_hello_unicode size_hello_unicode_gzip Metric Increase: T13035 ------------------------- Co-authored-by: Codex <codex(a)openai.com> - - - - - 182f3d0f by Cheng Shao at 2026-01-09T20:25:28-05:00 iserv: add comment about -fkeep-cafs - - - - - 49675b69 by Matthew Craven at 2026-01-09T20:26:14-05:00 Account for "stupid theta" in demand sig for DataCon wrappers Fixes #26748. - - - - - f3c18890 by Samuel Thibault at 2026-01-10T15:48:22+01:00 hurd: Fix getExecutablePath build 3939a8bf93e27 ("GNU/Hurd: Add getExecutablePath support") added using /proc/self/exe for GNU/Hurd but missed adding the required imports for the corresponding code. - - - - - 7f15bd15 by Samuel Thibault at 2026-01-12T07:16:25-05:00 Fix the OS string encoding for GNU/Hurd Following https://github.com/haskell/cabal/pull/9434/files , and as seen in the various gnu_HOST_OS usages in the source code, it is expected that GNU/Hurd is advertised as "gnu", like the autotools do. - - - - - 1db2f240 by Andrew Lelechenko at 2026-01-12T07:17:06-05:00 Add since annotation for Data.Bifoldable1 Fixes #26432 - - - - - e038a383 by Sven Tennie at 2026-01-12T07:17:49-05:00 Ignore Windows CI tool directories in Git Otherwise, we see thousands of changes in `git status` which is very confusing to work with. - - - - - 5d7e9a85 by Cheng Shao at 2026-01-12T18:10:57+01:00 rts: add is-valid-utf8.c to .ubsan-suppressions A minor one in `bytestring` that might surface when building with +ubsan using clang. - - - - - b4e1c296 by Cheng Shao at 2026-01-12T18:10:57+01:00 hadrian: add support for building with AddressSanitizer This patch adds a +asan flavour transformer to hadrian to build all stage1+ C/C++ code with AddressBehaviorSanitizer. This is particularly useful to catch potential out-of-bounds and use-after-free bugs in the RTS codebase. - - - - - 35a9f131 by Cheng Shao at 2026-01-12T18:10:57+01:00 ci: add ubsan+asan job We now have a `x86_64-linux-fedora43-quick-validate+debug_info+ubsan+asan` validate/nightly job with both UBSan/ASan enabled. This is enabled in full-ci pipelines as well as MR pipelines with `test-sanitizer` label. - - - - - 929e04a3 by Cheng Shao at 2026-01-12T18:10:57+01:00 rts: add ASAN instrumentation to mblock allocator - - - - - 5d52e10e by Cheng Shao at 2026-01-12T18:10:57+01:00 rts: add ASAN instrumentation to mgroup allocator - - - - - 6223884e by Cheng Shao at 2026-01-12T18:10:57+01:00 rts: add ASAN instrumentation to block allocator - - - - - 5abb77e1 by Cheng Shao at 2026-01-12T18:10:57+01:00 rts: add ASAN instrumentation to cap->pinned_object_empty - - - - - 648d504d by Cheng Shao at 2026-01-12T18:10:57+01:00 rts: add ASAN instrumentation to gc_thread->free_blocks - - - - - b074fda3 by Cheng Shao at 2026-01-12T18:10:58+01:00 rts: add ASAN instrumentation to hash table free list - - - - - dc02cf7a by Cheng Shao at 2026-01-12T18:10:58+01:00 rts: add ASAN instrumentation to per-Task InCall free list - - - - - 1bf7b38a by Cheng Shao at 2026-02-12T21:46:31+00:00 WIP - - - - - 106 changed files: - .gitignore - .gitlab/generate-ci/gen_ci.hs - .gitlab/jobs.yaml - compiler/GHC/Cmm.hs - compiler/GHC/Cmm/InitFini.hs - compiler/GHC/CmmToAsm/AArch64/Ppr.hs - compiler/GHC/CmmToAsm/Ppr.hs - compiler/GHC/CmmToAsm/Wasm/FromCmm.hs - compiler/GHC/CmmToAsm/X86/Ppr.hs - compiler/GHC/CmmToC.hs - compiler/GHC/CmmToLlvm/Data.hs - compiler/GHC/Core/Opt/Specialise.hs - compiler/GHC/Driver/Backpack.hs - compiler/GHC/Driver/Config/Interpreter.hs - compiler/GHC/Driver/Downsweep.hs - compiler/GHC/Driver/DynFlags.hs - compiler/GHC/Driver/Pipeline.hs - compiler/GHC/Driver/Session.hs - compiler/GHC/Linker/Dynamic.hs - compiler/GHC/Linker/Executable.hs - compiler/GHC/Linker/Loader.hs - compiler/GHC/Linker/Unit.hs - compiler/GHC/Settings.hs - compiler/GHC/Settings/IO.hs - compiler/GHC/StgToJS/Linker/Utils.hs - compiler/GHC/Types/Id/Make.hs - compiler/GHC/Unit/Info.hs - compiler/GHC/Unit/State.hs - compiler/GHC/Utils/Binary.hs - configure.ac - distrib/configure.ac.in - docs/users_guide/phases.rst - ghc/Main.hs - hadrian/cfg/default.host.target.in - hadrian/cfg/default.target.in - hadrian/doc/flavours.md - hadrian/src/Flavour.hs - hadrian/src/Settings/Builders/Cabal.hs - libraries/base/changelog.md - libraries/base/src/Data/Bifoldable1.hs - libraries/base/src/GHC/Conc.hs - libraries/base/src/GHC/Conc/Sync.hs - libraries/ghc-boot/GHC/Unit/Database.hs - libraries/ghc-internal/ghc-internal.buildinfo.in - libraries/ghc-internal/ghc-internal.cabal.in - libraries/ghc-internal/src/GHC/Internal/Conc/IO.hs - libraries/ghc-internal/src/GHC/Internal/Conc/POSIX.hs - libraries/ghc-internal/src/GHC/Internal/Conc/Sync.hs - libraries/ghc-internal/src/GHC/Internal/Conc/Sync.hs-boot - libraries/ghc-internal/src/GHC/Internal/Conc/Windows.hs - libraries/ghc-internal/src/GHC/Internal/Event/Thread.hs - libraries/ghc-internal/src/GHC/Internal/Event/Windows/Thread.hs - + libraries/ghc-internal/src/GHC/Internal/STM.hs - libraries/ghc-internal/src/GHC/Internal/System/Environment/ExecutablePath.hsc - libraries/ghc-platform/src/GHC/Platform/ArchOS.hs - + m4/fp_linker_supports_verbatim.m4 - m4/prep_target_file.m4 - mk/system-cxx-std-lib-1.0.conf.in - rts/.ubsan-suppressions - rts/Hash.c - rts/StgMiscClosures.cmm - rts/Task.c - rts/configure.ac - rts/include/Stg.h - + rts/include/rts/ASANUtils.h - rts/rts.buildinfo.in - rts/rts.cabal - rts/sm/BlockAlloc.c - rts/sm/GCUtils.c - rts/sm/MBlock.c - rts/sm/Storage.c - + testsuite/driver/_elffile.py - testsuite/driver/runtests.py - testsuite/driver/testglobals.py - testsuite/driver/testlib.py - testsuite/ghc-config/ghc-config.hs - + testsuite/tests/dmdanal/should_run/T26748.hs - + testsuite/tests/dmdanal/should_run/T26748.stdout - testsuite/tests/dmdanal/should_run/all.T - + testsuite/tests/driver/fully-static/Hello.hs - + testsuite/tests/driver/fully-static/Makefile - + testsuite/tests/driver/fully-static/all.T - + testsuite/tests/driver/fully-static/fully-static.stdout - + testsuite/tests/driver/fully-static/test/Test.hs - + testsuite/tests/driver/fully-static/test/test.pkg - + testsuite/tests/driver/mostly-static/Hello.hs - + testsuite/tests/driver/mostly-static/Makefile - + testsuite/tests/driver/mostly-static/all.T - + testsuite/tests/driver/mostly-static/mostly-static.stdout - + testsuite/tests/driver/mostly-static/test/test.c - + testsuite/tests/driver/mostly-static/test/test.h - + testsuite/tests/driver/mostly-static/test/test.pkg - testsuite/tests/ffi/should_run/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 - testsuite/tests/interface-stability/base-exports.stdout-ws-32 - testsuite/tests/rts/T18623/all.T - testsuite/tests/rts/all.T - + testsuite/tests/simplCore/should_compile/T26682.hs - + testsuite/tests/simplCore/should_compile/T26682a.hs - testsuite/tests/simplCore/should_compile/all.T - utils/ghc-pkg/Main.hs - utils/ghc-toolchain/exe/Main.hs - utils/ghc-toolchain/src/GHC/Toolchain/Tools/Link.hs - utils/iserv/iserv.cabal.in The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/7608aad3149d145ace1c6f6459f98a… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/7608aad3149d145ace1c6f6459f98a… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc] Pushed new branch wip/ani-simon/app-do
by Apoorv Ingle (＠ani) 12 Feb '26

12 Feb '26

Apoorv Ingle pushed new branch wip/ani-simon/app-do at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/ani-simon/app-do You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc] Pushed new branch wip/fix-wasm-js-main-logic
by Cheng Shao (＠TerrorJack) 12 Feb '26

12 Feb '26

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

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[Git][ghc/ghc][wip/marge_bot_batch_merge_job] 5 commits: Simplify the treatment of static forms
by Marge Bot (＠marge-bot) 12 Feb '26

12 Feb '26

Marge Bot pushed to branch wip/marge_bot_batch_merge_job at Glasgow Haskell Compiler / GHC Commits: 4df0adf6 by Simon Peyton Jones at 2026-02-11T21:50:13-05:00 Simplify the treatment of static forms This MR implements GHC proposal 732: simplify static forms, https://github.com/ghc-proposals/ghc-proposals/pull/732 thereby addressing #26556. See `Note [Grand plan for static forms]` in GHC.Iface.Tidy.StaticPtrTable The main changes are: * There is a new, simple rule for (static e), namely that the free term variables of `e` must be bound at top level. The check is done in the `HsStatic` case of `GHC.Rename.Expr.rnExpr` * That in turn substantially simplifies the info that the typechecker carries around in its type environment. Hooray. * The desugarer emits static bindings to top level directly; see the `HsStatic` case of `dsExpr`. * There is no longer any special static-related magic in the FloatOut pass. And the main Simplifier pipeline no longer needs a special case to run FloatOut even with -O0. Hooray. All this forced an unexpected change to the pattern match checker. It recursively invokes the main Hs desugarer when it wants to take a look at a term to spot some special cases (notably constructor applications). We don't want to emit any nested (static e) bindings to top level a second time! Yikes. That forced a modest refactor in GHC.HsToCore.Pmc: * The `dsl_nablas` field of `DsLclEnv` now has a `NoPmc` case, which says "I'm desugaring just for pattern-match checking purposes". * When that flag is set we don't emit static binds. That in turn forces a cascade of refactoring, but the net effect is an improvement; less risk of duplicated (even exponential?) work. See Note [Desugaring HsExpr during pattern-match checking]. 10% metric decrease, on some architectures, of compile-time max-bytes-used on T15304. Metric Decrease: T15304 - - - - - 7922f728 by Teo Camarasu at 2026-02-11T21:50:58-05:00 ghc-internal: avoid depending on GHC.Internal.Exts This module is mostly just re-exports. It made sense as a user-facing module, but there's no good reason ghc-internal modules should depend on it and doing so linearises the module graph - move considerAccessible to GHC.Internal.Magic Previously it lived in GHC.Internal.Exts, but it really deserves to live along with the other magic function, which are already re-exported from .Exts - move maxTupleSize to GHC.Internal.Tuple This previously lived in GHC.Internal.Exts but a comment already said it should be moved to .Tuple Resolves #26832 - - - - - b6a4a29b by Eric Lee at 2026-02-11T21:51:55-05:00 Remove unused Semigroup imports to fix GHC 9.14 bootstrapping - - - - - 99d8c146 by Simon Peyton Jones at 2026-02-12T17:36:59+00:00 Fix subtle bug in cast worker/wrapper See (CWw4) in Note [Cast worker/wrapper]. The true payload is in the change to the definition of GHC.Types.Id.Info.hasInlineUnfolding Everthing else is just documentation. There is a 2% compile time decrease for T13056; I'll take the win! Metric Decrease: T13056 - - - - - c1085eb0 by Simon Peyton Jones at 2026-02-12T14:46:12-05:00 Add regression tests for four StaticPtr bugs Tickets #26545, #24464, #24773, #16981 are all solved by the recently-landed MR commit 318ee13bcffa6aa8df42ba442ccd92aa0f7e210c Author: Simon Peyton Jones <simon.peytonjones(a)gmail.com> Date: Mon Oct 20 23:07:20 2025 +0100 Simplify the treatment of static forms This MR just adds regression tests for them. - - - - - 95 changed files: - compiler/GHC/Builtin/Names.hs - compiler/GHC/CmmToLlvm/CodeGen.hs - compiler/GHC/Core/Lint.hs - compiler/GHC/Core/Opt/Pipeline.hs - compiler/GHC/Core/Opt/SetLevels.hs - compiler/GHC/Core/Opt/Simplify/Iteration.hs - compiler/GHC/Core/Opt/WorkWrap.hs - compiler/GHC/CoreToStg/AddImplicitBinds.hs - compiler/GHC/Driver/Config/Core/Lint.hs - compiler/GHC/Hs/Binds.hs - compiler/GHC/Hs/Decls.hs - compiler/GHC/Hs/Expr.hs - compiler/GHC/Hs/Instances.hs - compiler/GHC/Hs/Syn/Type.hs - compiler/GHC/Hs/Utils.hs - compiler/GHC/HsToCore.hs - compiler/GHC/HsToCore/Docs.hs - compiler/GHC/HsToCore/Expr.hs - compiler/GHC/HsToCore/GuardedRHSs.hs - compiler/GHC/HsToCore/Match.hs - compiler/GHC/HsToCore/Monad.hs - compiler/GHC/HsToCore/Pmc.hs - compiler/GHC/HsToCore/Pmc/Desugar.hs - compiler/GHC/HsToCore/Pmc/Solver.hs - compiler/GHC/HsToCore/Quote.hs - compiler/GHC/HsToCore/Ticks.hs - compiler/GHC/HsToCore/Types.hs - compiler/GHC/Iface/Ext/Ast.hs - compiler/GHC/Iface/Tidy.hs - compiler/GHC/Iface/Tidy/StaticPtrTable.hs - compiler/GHC/Rename/Bind.hs - compiler/GHC/Rename/Expr.hs - compiler/GHC/Rename/Module.hs - compiler/GHC/Tc/Deriv.hs - compiler/GHC/Tc/Errors/Ppr.hs - compiler/GHC/Tc/Errors/Types.hs - compiler/GHC/Tc/Gen/Bind.hs - compiler/GHC/Tc/Gen/Expr.hs - compiler/GHC/Tc/Gen/Head.hs - compiler/GHC/Tc/Gen/Pat.hs - compiler/GHC/Tc/Gen/Sig.hs - compiler/GHC/Tc/Module.hs - compiler/GHC/Tc/Solver.hs - compiler/GHC/Tc/Solver/Monad.hs - compiler/GHC/Tc/TyCl/Instance.hs - compiler/GHC/Tc/TyCl/Utils.hs - compiler/GHC/Tc/Types.hs - compiler/GHC/Tc/Types/BasicTypes.hs - compiler/GHC/Tc/Types/Constraint.hs - compiler/GHC/Tc/Types/Origin.hs - compiler/GHC/Tc/Utils/Env.hs - compiler/GHC/Tc/Utils/Monad.hs - compiler/GHC/Tc/Utils/TcMType.hs - − compiler/GHC/Tc/Utils/TcMType.hs-boot - compiler/GHC/Tc/Zonk/TcType.hs - compiler/GHC/Tc/Zonk/Type.hs - compiler/GHC/Types/Id/Info.hs - compiler/GHC/Types/Id/Make.hs - libraries/ghc-internal/src/GHC/Internal/Exts.hs - libraries/ghc-internal/src/GHC/Internal/Heap/Closures.hs - libraries/ghc-internal/src/GHC/Internal/JS/Foreign/Callback.hs - libraries/ghc-internal/src/GHC/Internal/JS/Prim.hs - libraries/ghc-internal/src/GHC/Internal/JS/Prim/Internal/Build.hs - libraries/ghc-internal/src/GHC/Internal/Magic.hs - libraries/ghc-internal/src/GHC/Internal/Stack/Decode.hs - libraries/ghc-internal/src/GHC/Internal/Tuple.hs - libraries/ghc-internal/src/GHC/Internal/Wasm/Prim/Exports.hs - libraries/ghc-internal/src/GHC/Internal/Wasm/Prim/Imports.hs - libraries/ghc-internal/src/GHC/Internal/Wasm/Prim/Types.hs - testsuite/tests/codeGen/should_run/CgStaticPointers.hs - testsuite/tests/codeGen/should_run/CgStaticPointersNoFullLazyness.hs - testsuite/tests/ghci/scripts/T20150.stdout - testsuite/tests/interface-stability/ghc-experimental-exports.stdout - testsuite/tests/interface-stability/ghc-experimental-exports.stdout-mingw32 - testsuite/tests/interface-stability/ghc-prim-exports.stdout - testsuite/tests/interface-stability/ghc-prim-exports.stdout-mingw32 - testsuite/tests/parser/should_compile/DumpRenamedAst.stderr - testsuite/tests/parser/should_compile/T14189.stderr - testsuite/tests/rename/should_fail/RnStaticPointersFail01.stderr - testsuite/tests/rename/should_fail/RnStaticPointersFail03.stderr - + testsuite/tests/rename/should_fail/T26545.hs - + testsuite/tests/rename/should_fail/T26545.stderr - testsuite/tests/rename/should_fail/all.T - + testsuite/tests/simplCore/should_compile/T26903.hs - + testsuite/tests/simplCore/should_compile/T26903.stderr - testsuite/tests/simplCore/should_compile/T8331.stderr - testsuite/tests/simplCore/should_compile/all.T - + testsuite/tests/typecheck/should_compile/T24464.hs - testsuite/tests/typecheck/should_compile/all.T - + testsuite/tests/typecheck/should_run/T16981.hs - + testsuite/tests/typecheck/should_run/T16981.stdout - + testsuite/tests/typecheck/should_run/T24773.hs - + testsuite/tests/typecheck/should_run/T24773.stdout - testsuite/tests/typecheck/should_run/all.T - testsuite/tests/warnings/should_fail/CaretDiagnostics1.stderr The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/02e2d6f7c25529137f0c50dace0a34… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/02e2d6f7c25529137f0c50dace0a34… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/jeltsch/duplex-readability-and-writability] Tell users what “semi-closed” means for duplex handles
by Wolfgang Jeltsch (＠jeltsch) 12 Feb '26

12 Feb '26

Wolfgang Jeltsch pushed to branch wip/jeltsch/duplex-readability-and-writability at Glasgow Haskell Compiler / GHC Commits: 628441f4 by Wolfgang Jeltsch at 2026-02-12T21:29:21+02:00 Tell users what “semi-closed” means for duplex handles - - - - - 1 changed file: - libraries/ghc-internal/src/GHC/Internal/IO/Handle/Text.hs Changes: ===================================== libraries/ghc-internal/src/GHC/Internal/IO/Handle/Text.hs ===================================== @@ -361,19 +361,18 @@ unpack_nl !buf !r !w acc0 -- ----------------------------------------------------------------------------- -- hGetContents --- hGetContents on a DuplexHandle only affects the read side: you can --- carry on writing to it afterwards. - -- | Computation 'hGetContents' @hdl@ returns the list of characters -- corresponding to the unread portion of the channel or file managed -- by @hdl@, which is put into an intermediate state, /semi-closed/. --- In this state, @hdl@ is effectively closed, --- but items are read from @hdl@ on demand and accumulated in a special --- list returned by 'hGetContents' @hdl@. +-- In this state, @hdl@ is treated like a closed handle, with the +-- following exceptions: +-- +-- * Characters can be read from @hdl@ by evaluating portions of the +-- list returned by 'hGetContents' @hdl@. +-- * If the handle allows for independent reading and writing, as it is +-- the case for socket handles, writing continues to be possible. -- --- Any operation that fails because a handle is closed, --- also fails if a handle is semi-closed. The only exception is --- 'GHC.Internal.System.IO.hClose'. A semi-closed handle becomes closed: +-- A semi-closed handle becomes closed: -- -- * if 'GHC.Internal.System.IO.hClose' is applied to it; -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/628441f417d7c2f5bedc7be3ab5e817… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/628441f417d7c2f5bedc7be3ab5e817… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/T26903] Fix subtle bug in cast worker/wrapper
by Simon Peyton Jones (＠simonpj) 12 Feb '26

12 Feb '26

Simon Peyton Jones pushed to branch wip/T26903 at Glasgow Haskell Compiler / GHC Commits: 99d8c146 by Simon Peyton Jones at 2026-02-12T17:36:59+00:00 Fix subtle bug in cast worker/wrapper See (CWw4) in Note [Cast worker/wrapper]. The true payload is in the change to the definition of GHC.Types.Id.Info.hasInlineUnfolding Everthing else is just documentation. There is a 2% compile time decrease for T13056; I'll take the win! Metric Decrease: T13056 - - - - - 8 changed files: - compiler/GHC/Core/Opt/Simplify/Iteration.hs - compiler/GHC/Core/Opt/WorkWrap.hs - compiler/GHC/Driver/Config/Core/Lint.hs - compiler/GHC/Types/Id/Info.hs - + testsuite/tests/simplCore/should_compile/T26903.hs - + testsuite/tests/simplCore/should_compile/T26903.stderr - testsuite/tests/simplCore/should_compile/T8331.stderr - testsuite/tests/simplCore/should_compile/all.T Changes: ===================================== compiler/GHC/Core/Opt/Simplify/Iteration.hs ===================================== @@ -474,14 +474,14 @@ leaving a simpler job for demand-analysis worker/wrapper. See #19874. Wrinkles -1. We must /not/ do cast w/w on +(CWW1) We must /not/ do cast w/w on f = g |> co otherwise it'll just keep repeating forever! You might think this is avoided because the call to tryCastWorkerWrapper is guarded by - preInlineUnconditinally, but I'm worried that a loop-breaker or an - exported Id might say False to preInlineUnonditionally. + preInlineUnconditionally, but I'm worried that a loop-breaker or an + exported Id might say False to preInlineUnconditionally. -2. We need to be careful with inline/noinline pragmas: +(CWW2) We need to be careful with inline/noinline pragmas: rec { {-# NOINLINE f #-} f = (...g...) |> co ; g = ...f... } @@ -496,15 +496,15 @@ Wrinkles f = $wf |> co ; g = ...f... } and that is bad: the whole point is that we want to inline that - cast! We want to transfer the pagma to $wf: + cast! We want to transfer the pragma to $wf: rec { {-# NOINLINE $wf #-} $wf = ...g... ; f = $wf |> co ; g = ...f... } c.f. Note [Worker/wrapper for NOINLINE functions] in GHC.Core.Opt.WorkWrap. -3. We should still do cast w/w even if `f` is INLINEABLE. E.g. - {- f: Stable unfolding = <stable-big> -} +(CWW3) We should still do cast w/w even if `f` is INLINEABLE. E.g. + {- f: Stable unfolding (arity 2) = <stable-big> -} f = (\xy. <big-body>) |> co Then we want to w/w to {- $wf: Stable unfolding = <stable-big> |> sym co -} @@ -513,15 +513,43 @@ Wrinkles Notice that the stable unfolding moves to the worker! Now demand analysis will work fine on $wf, whereas it has trouble with the original f. c.f. Note [Worker/wrapper for INLINABLE functions] in GHC.Core.Opt.WorkWrap. - This point also applies to strong loopbreakers with INLINE pragmas, see - wrinkle (4). -4. We should /not/ do cast w/w for non-loop-breaker INLINE functions (hence - hasInlineUnfolding in tryCastWorkerWrapper, which responds False to - loop-breakers) because they'll definitely be inlined anyway, cast and - all. And if we do cast w/w for an INLINE function with arity zero, we get +(CWW4) We should /not/ do cast w/w for INLINE functions (hence `hasInlineUnfolding` + in `tryCastWorkerWrapper`) because they'll definitely be inlined anyway, cast + and all. + + Moreover, if we do cast w/w for an INLINE function with arity zero, we get something really silly: we inline that "worker" right back into the wrapper! - Worse than a no-op, because we have then lost the stable unfolding. + In fact it is Much Worse than a no-op, because we have then lost the stable + unfolding --- aargh (see #26903). E.g. similar example to (CWW3) + {- g: Stable unfolding (arity 0) = <stable-big> -} NB arity 0! + g = (\xy. <big-body>) |> co + If we w/w to this: + {- $wg: Stable unfolding (arity 0) = <stable-big> |> sym co -} + $wg = \xy. <big-body> + g = $wg |> co + then we'll inline $wg at the call site in `g` giving + {- $wg: Stable unfolding (arity 0) = <stable-big> |> sym co -} + $wg = \xy. <big-body> + g = (<stable-big> |> sym co) |> co + and now we'll drop `$wg` as dead and we have lost the unfolding on `g`. + (We could /also/ give the binding `g = $wf |> co` a stable unfolding. Then + things would work right; but there is also no point in doing the cast + worker/wrapper in the first place.) + + NB: you might wonder about a loop-breaker with an INLINE pragma; after all, a + loop breaker won't "definitely be inlined anyway", so arguably we should not + disable cast w/w/ for it. But a Rec group can /look/ recursive at an early + stage, and subsequently /become/ non-recursive after some simplification. + (This is common in instance decls; see Note [Checking for INLINE loop breakers] + in GHC.Core.Lint.) So the danger is that we'll permanently lose that stable + unfolding that we specifically wanted (#26903). Simple solution: disable cast + w/w for /any/ INLINE function. See the defn + of `GHC.Types.Id.Info.hasInlineUnfolding`. + + The danger is that an INLINE pragma on a genuninely-recursive function + will kill worker-wrapper. Well, so be it. They are pretty suspicious anyway; + see Note [Checking for INLINE loop breakers]. All these wrinkles are exactly like worker/wrapper for strictness analysis: f is the wrapper and must inline like crazy @@ -586,11 +614,11 @@ tryCastWorkerWrapper env bind_cxt old_bndr bndr (Cast rhs co) | BC_Let top_lvl is_rec <- bind_cxt -- Not join points , not (isDFunId bndr) -- nor DFuns; cast w/w is no help, and we can't transform -- a DFunUnfolding in mk_worker_unfolding - , not (exprIsTrivial rhs) -- Not x = y |> co; Wrinkle 1 - , not (hasInlineUnfolding info) -- Not INLINE things: Wrinkle 4 - , typeHasFixedRuntimeRep work_ty -- Don't peel off a cast if doing so would - -- lose the underlying runtime representation. - -- See Note [Preserve RuntimeRep info in cast w/w] + , not (exprIsTrivial rhs) -- Not x = y |> co; see (CWW1) + , not (hasInlineUnfolding info) -- Not INLINE things: see (CWW4) + , typeHasFixedRuntimeRep work_ty -- Don't peel off a cast if doing so would + -- lose the underlying runtime representation. + -- See Note [Preserve RuntimeRep info in cast w/w] , not (isOpaquePragma (idInlinePragma old_bndr)) -- Not for OPAQUE bindings -- See Note [OPAQUE pragma] = do { uniq <- getUniqueM @@ -637,13 +665,13 @@ tryCastWorkerWrapper env bind_cxt old_bndr bndr (Cast rhs co) `setArityInfo` work_arity -- We do /not/ want to transfer OccInfo, Rules -- Note [Preserve strictness in cast w/w] - -- and Wrinkle 2 of Note [Cast worker/wrapper] + -- and (CWW2) of Note [Cast worker/wrapper] ----------- Worker unfolding ----------- -- Stable case: if there is a stable unfolding we have to compose with (Sym co); -- the next round of simplification will do the job -- Non-stable case: use work_rhs - -- Wrinkle 3 of Note [Cast worker/wrapper] + -- See (CWW4) of Note [Cast worker/wrapper] mk_worker_unfolding top_lvl work_id work_rhs = case realUnfoldingInfo info of -- NB: the real one, even for loop-breakers unf@(CoreUnfolding { uf_tmpl = unf_rhs, uf_src = src }) ===================================== compiler/GHC/Core/Opt/WorkWrap.hs ===================================== @@ -179,8 +179,9 @@ several liked-named Ids bouncing around at the same time---absolute mischief.) Notice that we refrain from w/w'ing an INLINE function even if it is -in a recursive group. It might not be the loop breaker. (We could -test for loop-breaker-hood, but I'm not sure that ever matters.) +in a recursive group. It might not be the loop breaker. (We used to +test for loop-breaker-hood, but see (CWW4) in Note [Cast worker/wrapper] +in GHC.Core.Opt.Simplify.Iteration.) Note [Worker/wrapper for INLINABLE functions] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ===================================== compiler/GHC/Driver/Config/Core/Lint.hs ===================================== @@ -132,8 +132,6 @@ perPassFlags dflags pass -- there may be some INLINE knots still tied, which is tiresomely noisy CoreDoSimplify cfg | SimplPhase InitialPhase <- sm_phase (so_mode cfg) - -> True - | otherwise -> False _ -> True ===================================== compiler/GHC/Types/Id/Info.hs ===================================== @@ -610,7 +610,12 @@ hasInlineUnfolding :: IdInfo -> Bool -- ^ True of a /non-loop-breaker/ Id that has a /stable/ unfolding that is -- (a) always inlined; that is, with an `UnfWhen` guidance, or -- (b) a DFunUnfolding which never needs to be inlined -hasInlineUnfolding info = isInlineUnfolding (unfoldingInfo info) +-- +-- Very important that this work with `realUnfoldingInfo` and so returns +-- True even for a loop-breaker that has an INLINE pragma. +-- See (CWW4) in Note [Cast worker/wrapper] in GHC.Core.Opt.Simplify.Iteration +-- for discussion, and #26903 for the dire consequences of getting this wrong. +hasInlineUnfolding info = isInlineUnfolding (realUnfoldingInfo info) setArityInfo :: IdInfo -> ArityInfo -> IdInfo setArityInfo info ar = ===================================== testsuite/tests/simplCore/should_compile/T26903.hs ===================================== @@ -0,0 +1,23 @@ +{-# LANGUAGE DefaultSignatures #-} +module T26903 where + +newtype T a = MkT [a] + +class C a where + op :: [a] -> [a] -> T a + + -- This default method + -- * Has an INLINE pragma + -- * Is too big to inline without a pragma + -- * Has arity zero + {-# INLINE[1] op #-} + default op :: Ord a => [a] -> [a] -> T a + op = \xs ys -> MkT $ if xs>ys then reverse (reverse (reverse (reverse xs))) + else reverse (reverse (reverse (reverse (xs ++ ys)))) + +instance C Int where {} + +test :: [Int] -> T Int +test xs = op [] xs + -- We expect to see `op` inlined into the RHS of `test` + ===================================== testsuite/tests/simplCore/should_compile/T26903.stderr ===================================== @@ -0,0 +1,52 @@ + +==================== Tidy Core ==================== +Result size of Tidy Core + = {terms: 127, types: 130, coercions: 48, joins: 0/0} + +$dmop + = (\ @a _ $dOrd xs ys -> + case $fOrdList_$ccompare $dOrd xs ys of { + __DEFAULT -> + reverse1 (reverse1 (reverse1 (reverse1 (++ xs ys) []) []) []) []; + GT -> reverse1 (reverse1 (reverse1 (reverse xs) []) []) [] + }) + `cast` <Co:20> :: ... + +$fCInt_$cop + = (\ xs ys -> + case $fOrdList_$s$ccompare xs ys of { + __DEFAULT -> + reverse1 (reverse1 (reverse1 (reverse1 (++ xs ys) []) []) []) []; + GT -> reverse1 (reverse1 (reverse1 (reverse xs) []) []) [] + }) + `cast` <Co:11> :: ... + +$fCInt1 + = \ xs ys -> + case $fOrdList_$s$ccompare xs ys of { + __DEFAULT -> + reverse1 (reverse1 (reverse1 (reverse1 (++ xs ys) []) []) []) []; + GT -> reverse1 (reverse1 (reverse1 (reverse xs) []) []) [] + } + +$fCInt = C:C ($fCInt1 `cast` <Co:11> :: ...) + +test4 = reverse1 [] [] + +test3 = reverse1 test4 [] + +test2 = reverse1 test3 [] + +test1 = reverse1 test2 [] + +test + = \ xs -> + case $fOrdList_$s$ccompare [] xs of { + __DEFAULT -> + (reverse1 (reverse1 (reverse1 (reverse1 (++ [] xs) []) []) []) []) + `cast` <Co:3> :: ...; + GT -> test1 `cast` <Co:3> :: ... + } + + + ===================================== testsuite/tests/simplCore/should_compile/T8331.stderr ===================================== @@ -56,11 +56,11 @@ ReaderT r (ST s) (a -> b) -> ReaderT r (ST s) a -> r -> ST s b)) "SPEC $c>> @(ST s) @_" forall (@s) (@r) ($dMonad :: Monad (ST s)). - $fMonadReaderT1 @(ST s) @r $dMonad + $fMonadReaderT_$c>> @(ST s) @r $dMonad = $fMonadAbstractIOSTReaderT_$s$c>> @s @r "SPEC $c>>= @(ST s) @_" forall (@s) (@r) ($dMonad :: Monad (ST s)). - $fMonadReaderT2 @(ST s) @r $dMonad + $fMonadReaderT1 @(ST s) @r $dMonad = ($fMonadAbstractIOSTReaderT2 @s @r) `cast` (forall (a ::~ <*>_N) (b ::~ <*>_N). <ReaderT r (ST s) a>_R ===================================== testsuite/tests/simplCore/should_compile/all.T ===================================== @@ -581,3 +581,4 @@ test('T26722', [grep_errmsg(r'SPEC')], compile, ['-O -dno-typeable-binds']) test('T26805', [grep_errmsg(r'fromInteger')], compile, ['-O -dno-typeable-binds -ddump-simpl -dsuppress-uniques']) test('T26826', normal, compile, ['-O']) +test('T26903', [grep_errmsg(r'reverse')], compile, ['-O -dno-typeable-binds -ddump-simpl -dsuppress-uniques -dsuppress-all']) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/99d8c146c12146e1e21b1f2d3180984… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/99d8c146c12146e1e21b1f2d3180984… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/T26831] Wibble
by Simon Peyton Jones (＠simonpj) 12 Feb '26

12 Feb '26

Simon Peyton Jones pushed to branch wip/T26831 at Glasgow Haskell Compiler / GHC Commits: 6efd8505 by Simon Peyton Jones at 2026-02-12T17:14:05+00:00 Wibble - - - - - 1 changed file: - compiler/GHC/CoreToStg/Prep.hs Changes: ===================================== compiler/GHC/CoreToStg/Prep.hs ===================================== @@ -1539,12 +1539,12 @@ cpeArg env dmd arg arg3 = cpeEtaExpand arity arg2 -- See Note [Eta expansion of arguments in CorePrep] ; let (arg_float, v') = mkNonRecFloat env lev v arg3 - ; pprTraceM "cpeArg" (vcat [ text "arg1" <+> ppr arg1 - , text "decision" <+> ppr dec - , text "arg2" <+> ppr arg2 - , text "arity" <+> ppr arity - , text "arg3" <+> ppr arg3 - ]) +-- ; pprTraceM "cpeArg" (vcat [ text "arg1" <+> ppr arg1 +-- , text "decision" <+> ppr dec +-- , text "arg2" <+> ppr arg2 +-- , text "arity" <+> ppr arity +-- , text "arg3" <+> ppr arg3 +-- ]) ; return (snocFloat floats2 arg_float, varToCoreExpr v') } } View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/6efd850531aa05d445964a1de53ec29… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/6efd850531aa05d445964a1de53ec29… You're receiving this email because of your account on gitlab.haskell.org.

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