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[Git][ghc/ghc][wip/apk/rts-flag-fixes] 68 commits: Specialise: Stop looping on recursive dictionaries in interestingDict
by Andreas Klebinger (＠AndreasK) 21 Sep '26

21 Sep '26

Andreas Klebinger pushed to branch wip/apk/rts-flag-fixes at Glasgow Haskell Compiler / GHC Commits: 578bd185 by Andreas Klebinger at 2026-08-29T07:16:05-04:00 Specialise: Stop looping on recursive dictionaries in interestingDict interestingDict now doesn't look through loopbreaker unfoldings. Doing so would cause infinite loops on certain dictionaries. Fixes #27705. - - - - - 7bf546fc by Simon Peyton Jones at 2026-08-31T23:48:53-04:00 Never make an absent filler for a constraint type mkAbsentFiller used isTerminatingType to decide, but that is not enough. Consider class Eq a => UC a where {} let u :: UC Int -- UC Int is a "non-terminating type" u = error "Absent" let e :: Eq Int -- Eq Int is a "terminating type" e = $p1UC u We clearly must not make a filler for `e`, because we speculatively evaluate it. But speculatively evaluating `e` forces `u`, so we must not make one for `u` either. Asking isDictTy instead is not enough either, because it does not catch a constraint hidden behind an unreduced type family application: type family F a :: Constraint type instance F W = TC W a :: F W => Int -> Int -- (F W) argument is absent Oops! Entered absent arg Arg: irred Type: F W So play safe and use isPredTy: never make an absent filler for any constraint-kinded type. Fixes #27627 - - - - - 5f474953 by Zubin Duggal at 2026-08-31T23:48:53-04:00 Add tests for absent fillers at dictionary types T27627 a unary class whose superclass is a non-unary class T27627a ...whose superclass is a Constraint-kinded type family T27627b ...whose superclass is a quantified constraint T27627c a unary class applied to itself, (UC (UC (TC a))) T27627e a (forall b. P b) dictionary that loops - - - - - cd5c6bcc by Zubin Duggal at 2026-08-31T23:48:53-04:00 An abstract TyCon may hide a unary class A class declared in an hs-boot file is an AbstractTyCon inside the module loop, and compiling the real declaration may reveal it to be a UnaryClassTyCon. - isTerminatingType returned True for such AbstractTyCons - IfaceToCore set the unary flag to False in the DFunId So we could end up speculating bottom dictionaries because inside a module loop we see an UnaryClassTyCon as an AbstractTyCon Use isTerminatingTyCon, which returns False for an abstract TyCon. The Bool in DFunId is now a cache for isTerminatingTyCon, set in mkDFunIdDetails. Fixes #27704 - - - - - abfc224a by Zubin Duggal at 2026-08-31T23:48:53-04:00 Specialise: don't replace dead args with absent fillers specHeader decides an argument is dead by calling isDeadBinder on a binder of the /optimised RHS/, then applies the filler to the /stable unfolding/ template instead. The two may differ, so the argument can be dead in the RHS and not in the template. The specialised function's unfolding then has an absent filler, and any call site that inlines it evaluates the error thunk. Dropping dead args in the specialiser is rarely worth it, to quote Simon, "The later worker/wrapper pass will pick up the dead arg later if it is really dead. Keeps the specialiser simpler." So instead of trying to check if the arg really is dead in the stable unfolding, just drop the logic for dropping dead args in the specialiser altogeher. Fixes #27703 - - - - - 1557fd1c by Zubin Duggal at 2026-08-31T23:48:53-04:00 CorePrep: don't speculate a call across an hs-boot edge We take care not to evaluate things that might be bottom, like a looping dictionary group, but our analysis is defeated by boot files. We only track recursion within a module, so two dictionaries that depend on each other across a module loop each look non-recursive, and we might speculate them. Any recursion we cannot see must cross an hs-boot edge, so refuse to speculate calls that cross one. Fixes #27717 - - - - - 4117e5ae by Wolfgang Jeltsch at 2026-08-31T23:49:35-04:00 Incorporate the `rethrowSTM` reexport into the `stm` submodule - - - - - 4bfbf5c8 by ARATA Mizuki at 2026-09-01T18:55:08-04:00 testsuite: Fix out-of-bounds access in T3586 unsafeRead and unsafeWrite use 0-based index. Looking at #3586, the expected output seems to be 2.8e8. Addresses #27596 - - - - - 3f9db6d4 by ARATA Mizuki at 2026-09-01T18:55:08-04:00 testsuite: Fix out-of-bounds access in T21305 writeInt64Array# takes an index measured in units of Int64 elements. Fixes #27596 - - - - - 44d7788f by Simon Peyton Jones at 2026-09-01T18:55:53-04:00 Fix buglet in INLINE-arity calculation for pattern synonyms This fixes #27744. The buglet was accidentally introduced by commit 3a0f9a51c1dacc474c7fd128082edd8bf4081256 Author: Simon Peyton Jones <simon.peytonjones(a)gmail.com> Date: Sat Aug 1 00:13:02 2026 +0100 Fix three bugs related to required type args and INLINE pragmas I failed to find all the calls to `addInlinePragArity`! - - - - - df058f1d by Simon Jakobi at 2026-09-02T07:18:06-04:00 testsuite: Migrate perf tests off collect_compiler_stats('all') The 'all' metric argument applies a single tolerance to bytes allocated, max_bytes_used and peak_megabytes_allocated, although their noise profiles are incompatible (#27653): allocations are nearly deterministic, residency needs 10-20%, and peak is quantized to 1 MB. Any single tolerance is too tight for one metric or too slack for another. This migrates the remaining users of 'all' (and of the 'all' default) to explicit per-metric collection, ahead of removing 'all' from the driver. peak_megabytes_allocated is dropped everywhere: its 1 MB granularity makes tight relative windows meaningless (#27613), and it is sensitive to GC timing. In #27489 it drifted by -5.3% while max_bytes_used moved by less than 0.1%. Where a test guards a memory property, max_bytes_used covers it at byte granularity. Where the motivating ticket was about compile-time memory (T11545, T15304, T26425), residency remains gated via max_bytes_used, now with a residency-appropriate tolerance. max_bytes_used is dropped where residency was only ever an accident of 'all': * T15630, T15630a, T20261: the underlying tickets (#15630, #20261) contain no memory data at all. One is a simplifier-ticks blowup and the other is stated entirely in allocation numbers, so the 20% window never had teeth. * T21839c: #21839's measurements show residency essentially flat (+0.16%) while allocations moved +7%, so allocations are the discriminating metric. They are already gated at 1% via collect_compiler_runtime. The ghc/max gate had previously broken CI spuriously (9fd11585eb widened it from 1% to 10% for that reason). Allocation tolerances are tightened to the testsuite's conventional 2% where 'all' previously left them at 10-20%. Assisted-by: Claude Fable 5 - - - - - 72dd2432 by Simon Jakobi at 2026-09-02T07:18:06-04:00 testsuite: Remove the 'all' metric argument of collect_stats 'all' gated bytes allocated, max_bytes_used and peak_megabytes_allocated at a single tolerance, although their noise profiles are incompatible, making such tests either flaky or toothless (#27653). Closes #27653. Assisted-by: Claude Fable 5 - - - - - 2228cb30 by Simon Jakobi at 2026-09-02T07:18:06-04:00 testsuite: Make the deviation argument of collect_stats mandatory Almost every caller passes an explicit tolerance matched to the metric's noise profile, and the silent 20% default is far slacker than 'bytes allocated' merits. Only two tests relied on it. They now state their tolerance explicitly: large-project gets 10%, in line with other large compile-time tests. T9848 gets 2%: its metric is byte-for-byte deterministic across CI jobs and platforms of a given test_env, has drifted only about 2.5% since 2015, and the fusion failure it guards against would show up as a roughly +30000% jump. Assisted-by: Claude Fable 5 - - - - - 56291fc5 by Cheng Shao at 2026-09-02T07:18:45-04:00 autoconf/ghc-toolchain: bump llvm upper bound to support llvm 23 This commit bumps llvm upper bound to support llvm 23. - - - - - 20eb3f41 by Cheng Shao at 2026-09-02T07:18:45-04:00 rts: fix compilation issues with clang 23 clang 23 has broadened `-Wall`/`-Wextra` ranges, exposing some minor issues in the rts when building with validate flavours: - Unused locals - `#pragma GCC diagnostic pop` mismatch This commit fixes those. - - - - - 9e7739ab by Simon Jakobi at 2026-09-03T13:45:43-04:00 Add -Wimplicit-field-strictness (#16836) This opt-in warning fires when a data constructor field lacks an explicit strictness annotation (`!` or `~`). It complements the LazyFieldAnnotations extension (4762a8bf30f) from GHC proposal 752, which makes `~` annotations available for this purpose. Deciding which fields to report requires their levity, so the check runs after typechecking. To keep the noise down, the diagnostic is emitted once per data declaration, grouped by constructor. Closes #16836. Assisted-by: Claude Fable 5 - - - - - 6a44d591 by mangoiv at 2026-09-03T13:46:22-04:00 simplifier: remove a bogus `assert` in `rebuild_app'` in `GHC.CoreToStg.Prep.cpeApp`. Prior to this commit commit 08bc245be70d95801bc1138804ed1de9474fbdc0 Author: sheaf <sam.derbyshire(a)gmail.com> Date: Sat Feb 28 16:30:43 2026 +0100 Clean up join points, casts & ticks This commit shores up the logic dealing with casts and ticks occurring in between a join point binding and a jump any `PlaceRuntime` ticks we observed were profiling ticks, even though that isn't necessary. The more liberal rules in the above commit allow e.g. breakpoint ticks (which are valid PlaceRuntime ticks) to legitimately appear in an argument position. Fixes #27556 - - - - - eaa95a6f by Andrei Borzenkov at 2026-09-04T08:08:40-04:00 Parentheses in prefix GADT constructors (#27423) Updated `splitLHsGadtTy` to allow looking through the parentheses for inner binders. General example of a code pattern that's allowed now: data S a where MkS :: (forall a. S a) That should work now with any combination of nested foralls and parentheses. We don't perform parenthesis unwrapping for record GADT constructors in accordance with GHC Proposal #402. To this end `con_inner_bndrs` no longer stores plain forall telescopes: `[HsForAllTelescope pass]` is replaced with `[LHsGadtTelescope pass]`, a new `HsArg`-style type whose `HsGadtForAll` holds an inner telescope and whose `HsGadtPar` holds a pair of parentheses. The parentheses carry no meaning for renaming or type checking; the only reason to record them is exact-printing. Updated `pprConDecl` to improve the `parse == parse . ppr . parse` property of GADT pretty-printing. The pretty printer can now output code that's similar to this: data T a where MkT1 :: (forall a. T a) MkT2 :: forall . forall a. T a These are special cases of inner forall binders for prefix GADT constructors, when we have either implicit or zero explicit outer binders. - - - - - 639456a8 by Evgeny Malyshev at 2026-09-04T08:09:25-04:00 HsPat: Add spacing to unary tuple patterns Use hsep when printing unary boxed TuplePat applications so that the MkSolo constructor is separated from its argument. The old hcat rendered wildcard and parenthesized arguments as MkSolo_ and MkSolo(). Add T27034 to exercise the HsPat splice-dump path with wildcard and variable arguments, and update existing affected golden output. Fixes #27034 Assisted-By: OpenAI Codex - - - - - 2908ab36 by Simon Jakobi at 2026-09-05T07:22:17-04:00 X86 NCG: use btr/bts/btc for single-bit operations Previously the Cmm patterns x & ~(1 << i) x | (1 << i) x ^ (1 << i) compiled to mov/shl/not/and-style sequences of 3-4 instructions. Now they compile to a single btr, bts or btc, matching what C compilers produce. When the bit index is a literal, constant folding has already collapsed these patterns into ones with a literal mask, such as x & 0xfffffeffffffffff for x & ~(1 << 40). Such masks are now also compiled to a bit-test instruction when they don't fit in an imm32 and would otherwise have to be loaded into a register first. For a variable bit index, this applies only when the shift is unchecked (uncheckedShiftL#, Data.Bits.unsafeShiftL): the bounds-checked shiftL used by e.g. the default clearBit/setBit/complementBit implementations wraps the shift in a bounds mask that this optimisation does not see through. With a literal index, the bounds mask is constant-folded away, so the checked operations benefit too. See Note [Bit-test instructions] in GHC.CmmToAsm.X86.CodeGen. Fixes #25233. Assisted-by: Claude Fable 5 - - - - - c673ecf0 by Simon Peyton Jones at 2026-09-05T07:22:59-04:00 Move HsStatic free-var test to typechecker A `static` form should have no free *term* variables, but it can have free *type* variables. Alas, the renamer does not really know what is a term variable and what is a type variable, because of required type arguments. This patch moves the test to the typechecker, which does know. Addresses #27664 - - - - - 5939ceaf by sheaf at 2026-09-05T22:06:18-04:00 Windows: enforce path convention in ./configure As detailed in Note [MSYS paths] in Hadrian.Utilities, the standing convention (using Windows-style paths with forward slashes) is now enforced in ./configure instead of within Hadrian, removing the need for 'cygpath' calls within Hadrian. Fixes #26683 - - - - - a6061455 by sheaf at 2026-09-05T22:06:18-04:00 Hadrian: introduce ExeSpawnPath Specific details about the filepath used to specify the executable to spawn with CreateProcess matters on Windows: whether we use forward or backward slashes, a leading ./, or an absolute path changes how the executable is found. This commit introduces 'ExeSpawnPath' which is a path that is guaranteed to be found when spawning a process. All command invocations now go through this type to ensure the path has been properly sanitised. See Note [NeedCurrentDirectoryForExePath] in Hadrian.Utilities. The same treatment is applied to hsc2hs. Updates hsc2hs submodule. - - - - - e28313e3 by sheaf at 2026-09-05T22:07:06-04:00 Preserve tick ordering in 'tickTickedExpr' 'GHC.Core.Utils.tickTickedExpr' tries to combine a tick 't1' into an existing stack of ticks 't2s'. There are two situations: 1. 't1' is subsumed by a tick in 't2s': drop it. 2. A tick in 't2s' is subsumed by 't1', say 't2'. This commit ensures that in case (2) we keep 't1' on the outside instead of replacing 't2' at its position in the stack. This avoids re-ordering source notes (which was the cause of #27749). This fixes a regression introduced in 2dadf3b0d05. Fixes #27749 - - - - - 3172f557 by sheaf at 2026-09-05T22:07:06-04:00 Consistently prefer local source note ticks GHC.Cmm.DebugBlock.cmmDebugGen (DWARF annotations) and GHC.Stg.Debug.quickSourcePos (-finfo-table-map) both contained logic to prioritise source note ticks from the current module. This commit commons up this logic and propagates it to a third consumer: IPE stack frames, in GHC.Driver.GenerateCgIPEStub. See the new function GHC.Types.Tickish.bestSourceNote. - - - - - 192be0b6 by Luite Stegeman at 2026-09-07T19:43:36-04:00 rts: fix ctoi_tuple_spill_words getting out of sync Fix a few places that were not updating ctoi_tuple_spill_words correctly, leading to corruption/crashes when dealing with large unboxed tuples in bytecode: - captureContinuationAndAbort - findRetryFrameHelper/findAtomicallyFrameHelper - interpretBCO bci_BRK_FUN fixes #27633 - - - - - 604eb43c by Simon Jakobi at 2026-09-07T19:44:15-04:00 Hadrian: don't capture the testsuite driver's output (#27780) a6061455d54 switched the Testsuite RunTest case from Shake's cmd to the cmd' wrapper. cmd' always captures stdout and stderr, and since the caller asks for Exit, it returns without dumping what it captured. As a result the testsuite output no longer appears in CI job logs: failures, performance metrics and the summary were lost with the job. Use cmdExe, the uncaptured cmd, as the other plain-cmd sites in that commit do. Fixes #27780. Assisted-by: Claude Fable 5.1 - - - - - 06eee015 by Luite Stegeman at 2026-09-08T06:03:06+02:00 rts: Fix missing memory barrier in eval_thunk_selector (#27477) unchain_thunk_selectors() was missing an ACQUIRE_LOAD for the indirectee, leading to segfaults and corruption during GC on weakly-ordered architectures. Fixes #27477 - - - - - f8b2bd8f by Alan Zimmerman at 2026-09-08T09:39:12-04:00 EPA Fix HsCmdDo exact print with comments Exact printing of HsCmdDo was ignoring the location for the do statements, and this is an annotation that can have comments in it. Update it so we print the statements as a unit, including any comments. Also add the result of auditing that we capture comments in all needed places, noting that the remaining Anno SrcSpan instances are benign. - - - - - 430967ab by Duncan Coutts at 2026-09-09T11:07:01+01:00 Reorder cmm decls in HeapStackCheck for a better logical grouping And put more section headers in to deliniate the groups. We're about to add more here, so better to organise it first. - - - - - 344080fd by Duncan Coutts at 2026-09-09T11:07:01+01:00 Add raisePrimIOException and add it to RTS<->ghc-internal API The raisePrimIOException is a new helper function that I/O primops will use to help them report I/O errors. This is implemented in Haskell (since that's a lot easier), but has a calling convention that is easy(ish) to use from Cmm in the I/O primops. So we add it to the RTS API struct, and since we'll use it from Cmm we also need a field accessor macro for cmm (in deriveConstants). See the Note about how we cannot have nice things due to async exceptions and thunks preventing us from using catch. - - - - - cfdb3399 by Duncan Coutts at 2026-09-09T11:07:01+01:00 Add new blocking functions for I/O primops See the Note [Thread blocking for new I/O primops], and the Note [Calling convention for raisePrimIOException]. The point is, it will allow us to report synchronous exceptions from I/O primops, and do so much more flexibly. Previously the I/O managers could only report async exceptions and only nullary exceptions. This was OK historically, but no good as we add more I/O managers and expand the range of I/O operations we support. - - - - - f09c09d8 by Duncan Coutts at 2026-09-09T11:07:01+01:00 Change the encoding of results from the I/O manager to I/O primops Previously we just had async continue or heap overflow. We now extend what we can report with synchronous success, and synchronous failure with an errno. See Note [Encoding of result of I/O manager operations] We don't use these two new cases yet, but we will. In particular an epoll I/O manager needs to be able to report synchronous success or failure for waitRead#/waitWrite#. - - - - - 30f074d9 by Duncan Coutts at 2026-09-09T11:07:01+01:00 Switch waitRead/Write# to use new blocking return frames and update the I/O managers to set the result before resuming the blocked threads. This makes it possible for I/O managers to report synchronous exceptions from the I/O primops, but that will be done in a subsequent commit. - - - - - a8786ced by Duncan Coutts at 2026-09-09T11:07:01+01:00 Switch Poll and Select I/O managers to report sync exceptions rather than using raiseAsync with blockedOnBadFD_closure. This uses the new mechanism in the blocking frame return code to report synchronous exceptions. - - - - - 7a9df79a by Duncan Coutts at 2026-09-09T11:07:01+01:00 Remove now-unused blockedOnBadFD It was previously thrown by the select and poll I/O managers, but now they use raisePrimIOException (with an EBADF errno). - - - - - 6b0424e3 by Duncan Coutts at 2026-09-09T11:07:01+01:00 Improve the docs for delay# waitRead# and waitWrite# Document that the waitRead/Write# can throw exceptions (this was true before too), and that all of them are async exception cancellation points. - - - - - afeb2c30 by Duncan Coutts at 2026-09-09T20:08:58-04:00 Enable printf warnings for trace functions and fix resulting warnings Most of the existing printf-style functions are annotated with attributes to enable gcc/clang warnings for the printf format string, but several trace functions in Trace.h were missing this annotation. Enable them, and fix the resulting warnings. - - - - - 9a442c93 by Alan Zimmerman at 2026-09-09T20:09:36-04:00 EPA: Exact print ConDeclGADT without custom enterAnn !16321 brought in explicit capture of parens in a ConDeclGADT. The ExactPrint update introduced a modification of the fundamental function in exact printing, `enterAnn`, by splitting it into a version allowing injection of functionality normally handled by the ExactPrint class methods. This commit refactors that code, to restore the prior `enterAnn` version, by following the convention in ExactPrint of introducing a helper data structure with its own `ExactPrint` instance to achieve the same effect. - - - - - 4e9297ea by Simon Jakobi at 2026-09-11T08:32:45-04:00 ci: Actually pass --ignore-perf-failures to the testsuite driver 684c0018d9 changed the IGNORE_PERF_FAILURES handling to append to RUNTEST_ARGS with bash array syntax, but the three use sites still expand RUNTEST_ARGS as a scalar, which yields only the first array element. The appended flag was therefore dropped in every job, so perf improvements kept failing Marge Bot batches and master pipelines, contrary to #19562. Append as a string instead, matching the existing --force-colors append in test_hadrian. Fixes #27563. Assisted-by: Claude Fable 5.1 - - - - - 4f78dfdf by Simon Jakobi at 2026-09-11T08:33:24-04:00 testsuite: Give T26537 a 1.5x compile timeout Its -fregs-graph compile step tends to time out in unoptimized builds (#27188, #27776). Assisted-by: Claude Fable 5.1 - - - - - 130286e3 by Alan Zimmerman at 2026-09-11T08:34:08-04:00 EPA: Remove ListBanana / ListParens from AnnListBrackets This is a step towards making AnnList only represent lists of items which can have either braces or layout. - - - - - a9827d13 by Simon Jakobi at 2026-09-11T18:53:32-04:00 Reject ~, UNPACK and multiplicity annotations on type data fields Only `!` was rejected so far. `~`, UNPACK and multiplicity annotations were silently accepted. None of them make sense at the type level, so restriction (R3) of Note [Type data declarations] now covers all of them. Fixes #27732. Assisted-by: Claude Fable 5.1 - - - - - c71d5e23 by Alan Zimmerman at 2026-09-11T18:54:11-04:00 EPA: Add a Note for the exact print main loop - - - - - 7a108e43 by Simon Jakobi at 2026-09-12T18:35:59-04:00 FastString: Drop mkFastStringWith's constructor callback All three callers passed the same callback, a partial application of mkNewFastStringShortByteString to the string being interned. That partial application is allocated as a closure before the table lookup, on the common hit path too, although the callback is needed only after a miss. Drop the parameter and call mkNewFastStringShortByteString directly after a miss. Since nothing is passed "with" anymore, rename the function to internSB. Suggested by Simon PJ in #27528: https://gitlab.haskell.org/ghc/ghc/-/work_items/27528#note_687031 Assisted-by: Claude Fable 5 - - - - - 82c73b22 by Alan Zimmerman at 2026-09-12T18:36:38-04:00 EPA: More targeted HsDo exact print annotation HsDo is multi-purpose, as encoded in its HsDoFlavour field. Some of these are in a layout context (DoExpr, MDoExpr), others are not (ListComp, MonadComp). We are moving towards using AnnList only in layout contexts, so we switch the HsDo TTG annotation from holding an AnnList for this, to holding Either (EpToken "[", EpToken "]") AnnList This also allows us to trim down AnnListBrackets to only have braces or None, thereby opening the door for unification with the existing layout context data type EpLayout. - - - - - 749d2448 by Luite Stegeman at 2026-09-15T14:07:01-04:00 rts: handle large CONSTR closures in compacting GC The function update_fwd_large in the compacting GC could run into an unexpected object with the following error: internal error: update_fwd_large: unknown/strange object 1 Closure type 1 is CONSTR. This patch adds cases for CONSTR and CONSTR_NOCAF. This is the same problem as #27434 (large AP closures, fixed by cca0d58963), which missed this case. Fixes #27649 - - - - - 177d6155 by Luite Stegeman at 2026-09-15T14:07:02-04:00 testsuite: fix T27434 test with compacting GC Ensure that the interpreter is actually run with the compacting GC - - - - - 5796aa63 by Luite Stegeman at 2026-09-15T14:07:49-04:00 rts: initialise the stack frame header for mask_frame and apply_mask_frame We must leave the stack in consistent state before jumping to mask_frame or apply_mask_frame because they may result. Failing to do so could lead to a crash if there were waiting exceptions. Fixes #27651 - - - - - 2486cc92 by Simon Peyton Jones at 2026-09-15T14:08:36-04:00 Re-introduce the "weird SpecDict" case In this commit commit f80375dd4945350a1d784e436975b48b9c736eaf Author: Simon Peyton Jones <simon.peytonjones(a)gmail.com> Date: Sun Jun 29 15:26:58 2025 +0100 Refactor of Specialise.hs I removed a test for a dictionary with unbound type variables. This turned out to be wrong; see #27629. So this MR re-introduces it. - - - - - 8e09a46f by Duncan Coutts at 2026-09-15T20:11:35-04:00 Refactor (and rename) removeFromQueues, to simplify I/O managers Rename it to unblockAndAppendToRunQueue which better reflects what it is intended to do. The post-condition for unblockAndAppendToRunQueue is that the TSO is on the run queue or it is in the process of migrating to another cap. Previously it achieved that by always directly adding the TSO to the run queue itself. But this actually made things more complicated for the I/O managers, because it meant they needed a separate code path for notifying for cancellation compared to notifying for completion. The general notification code would always add the TSO to the run queue itself. So the improvement is to allow different cases in unblockAndAppendToRunQueue to achieve the same outcome in different ways: either directly adding to the run queue or calling helper functions that do so themselves. This then allows the new I/O managers to share code between the sync and async cancellation, and to reuse their notifyIOCompletion helpers for cancellation. This avoids a source of bugs where the completion path may be updated but the cancellation path may be forgotten, or similarly in future for sync/async operations. Update all the existing in-RTS I/O managers, and the posix timeout code. - - - - - d668782c by Duncan Coutts at 2026-09-15T20:11:35-04:00 Document that awaitCompletedTimeoutsOrIO expects an empty run queue This was true before but implicit and not relied on much. It's better to be explicit, and allow things to depend on it. - - - - - 11d938bb by Duncan Coutts at 2026-09-15T20:11:35-04:00 Store the I/O opcode and fd in the StgAsyncIOOp This will be useful in several I/O managers and it is handy for logging and debugging. It also doesn't increase the size of the StgAsyncIOOp structure. There was enough spare padding space already. Update the poll I/O manager to set the new fields. Add a helper function to convert the enum IOReadOrWrite into the enum IOOpCode. Also change IOReadOrWrite to be an enum without a typedef, for consistency with other enumerations in IOManager.h - - - - - bfa87882 by Duncan Coutts at 2026-09-15T20:11:36-04:00 Add a new I/O manager based on select() Yes, this is the second such I/O manager, but it is a modern re-implementation based on the new in-RTS I/O manager infrastructure. So it is cleaner and faster than the old select I/O manager. Why do we need another I/O manager based on select? Why isn't the poll() one good enough as a baseline portable unix I/O manager? Because macOS. Apple Inc. is why we cannot have nice things. The man page for poll on macOS documents the fact that it does not work. At least, it does not work for all files. Specifically, it does not work for device files. Whereas macOS select() does work for device files. Aaaaarg! We _do_ want to deprecate and remove the old select I/O manager, but due to macOS we cannot do that until we have a replacement. This is that replacement. Until of course a nice new k-queue I/O manager arrives, which could become the new default for macOS and FreeBSD. Interestingly, this select I/O manager is actually faster than the poll one, on Linix, in some circumstances: specifically when many Haskell threads are waiting on the same fd. The poll I/O manager does O(n) work for n threads waiting on I/O, whereas the select one does O(fds) work for the number of fds that threads are waiting on. Usually this is 1:1, so it's not noticable, but one can concoct extreme benchmarks to show the difference. - - - - - 8e9de15a by Duncan Coutts at 2026-09-15T20:11:36-04:00 Minor updates in the poll I/O manager to keep in sync with select This keeps it in sync with select one. The changes are based on code review while implementing the new select I/O manager. The two I/O managers are so similar in structure that it makes sense to try to minimise the diff between them. This should aid understanding, and fixes to both in future. - - - - - 222668bb by Duncan Coutts at 2026-09-15T20:11:36-04:00 Document the new select I/O manager in the user guide in the RTS section about I/O managers. And add a changelog entry. - - - - - 0f48735b by Cheng Shao at 2026-09-15T20:12:23-04:00 Revert "wasm: workaround WebKit bug in dyld" This reverts commit c9b8465c2c338176fcab9d197e9d31f4aee11f68. The underlying webkit bug has been fixed in https://commits.webkit.org/314219@main. Closes #27564. - - - - - 809294f1 by Luite Stegeman at 2026-09-15T20:13:08-04:00 rts: make stg_threadLabelzh return a valid pointer for unlabeled threads. This fixes a segfault in the GC caused by stg_threadLabelzh returning a 0 pointer in a GC pointer field. stg_threadLabelzh returns a tuple of type (# Int#, ByteArray# #). If a thread has no label, the second field is unused. We must still return a valid heap object pointer. Instead of returning 0, we now return stg_DEAD_SLOT_closure. fixes #27618 - - - - - e2d57026 by Luite Stegeman at 2026-09-15T20:13:54-04:00 JS: fix selector thunk handling fix a bug where entering a selector thunk could lead to a crash if the selected field was still a thunk. fixes #27788 - - - - - 1b4a622f by sheaf at 2026-09-17T02:39:13-04:00 Improvements to type/data family handling This commit makes several improvements to the treatment of type and data families in GHC: - We consistently use "type family" instead of "type synonym family" to avoid a confusion with type synonyms. For example: - OpenSynFamilyTyCon ==> OpenTypeFamilyTyCon - ClosedSynFamilyTyCon => ClosedTypeFamilyTyCon - Various functions that were specific to data families have been renamed to make this clear. For example: - tyConFamInst_maybe ==> tyConDataFamInst_maybe - isFamInstTyCon ==> isDataFamInstTyCon - 'FamTyConFlav' has been refactored so that all closed type families share a single 'ClosedTypeFamilyTyCon' constructor. The corresponding 'IfaceFamTyConFlav' type was updated similarly. This is then used to tidy up the implementation of GHC.Core.FamInstEnv.reduceTyFamApp_maybe. - - - - - c5aa9098 by sheaf at 2026-09-17T02:39:13-04:00 Small refactor of lookupFamInstEnv This commit reworks the code for looking up family instances in GHC.Core.FamInstEnv, reducing duplication a little bit. No change in behaviour. - - - - - a3ad4588 by sheaf at 2026-09-17T02:39:14-04:00 Use a type family for boxing unboxed types This commit overhauls the way in which unboxed types are boxed, as per the updated Note [Boxing constructors] in GHC.Builtin.WiredIn.Types.Box. The main change is to allow boxing to be parametrised by representation, e.g. making 'Box ty' a valid type. We achieve this by implementing 'Box' using a closed type family: newtype Box (a :: TYPE r) = Box (BoxTF r) type BoxTF :: RuntimeRep -> Type type family BoxTF r where BoxTF IntRep = BoxInt BoxTF Int8Rep = BoxInt8 BoxTF WordRep = BoxWord BoxTF LiftedRep = Any @Type BoxTF (TupleRep [r1, r2]) = (BoxTF r1, BoxTF r2) ... BoxTF (SumRep rs) = BoxSum rs This new design solves the following problems: - It allows boxing a type whose 'RuntimeRep' has not yet been determined (e.g. because we only learn the 'RuntimeRep' after constraint solving). That is, 'Box @r a' is a perfectly valid type even if 'r' is an unfilled metavariable. This is a requirement to fix #25065 (in which we need to box a type whose 'RuntimeRep' is only filled in during constraint solving). - It handles boxing of unboxed tuples and unboxed sums, via recursive boxing. See Note [Boxing TupleRep and SumRep] in GHC.Builtin.WiredIn.Types.Box. 'Box', 'BoxTF' and all of the boxing data constructors are defined in a new 'ghc-internal' module, 'GHC.Internal.Box'. This module contains nothing but wired-in declarations, and GHC never loads its interface on account of a wired-in thing (GHC.Builtin.Modules.isWiredInOnlyModule); see Note [Loading instances for wired-in things] in GHC.Iface.Load. The individual boxing data constructors are deliberately left as an internal implementation detail, and not exported. The intended API is via the two new magic 'Id's: box :: forall {r} (a :: TYPE r). a -> Box a unbox :: forall {r} (a :: TYPE r). Box a -> a exported from 'GHC.PrimOps' (in 'ghc-experimental'). The old boxing data types (IntBox, WordBox, FloatBox, DoubleBox, DictBox) are no longer exported from base (CLC proposal #421). We use this new design to consistently desugar: - parallel comprehensions (GHC.HsToCore.ListComp.{deListComp,dsMcStmt}) - then/group/using statements (GHC.HsToCore.ListComp.{dsTransStmt,dsMcStmt}) - recursive do blocks (mdo/rec) (GHC.HsToCore.Expr.dsDo) - arrows (GHC.HsToCore.Arrows) by consistently using 'box'/'unbox' to deal with unboxed types being put into big tuples. We also adapt 'GHC.Tc.Gen.Match.{tcMcStmt,tcDoStmt}' to create fresh /representation-polymorphic/ type variables for the binders that we are going to put into a big tuple (previously, GHC only allowed lifted types in that position). These desugaring of box and unbox is explained in Note [Desugaring box & unbox] in GHC.Core.Make.Box. Roughly speaking, the desugaring looks like: box @r @ty e ==> K e unbox @r @ty e ==> case e of K x -> x where 'K' is the boxing data constructor at RuntimeRep 'r'. It's slightly more complicated than that in practice: we first need to insert a cast (see Note [The canonical type of a RuntimeRep]) using the new 'CanonicalProv' 'UnivCoProvenance', and unboxed tuples/sums need recursive logic explained in Note [box/unbox for unboxed tuples and sums], including a specific 'BoxSum' datatypes for unboxed sum (which also needed a wired-in type-level list indexing type family (!!)). The desugaring happens in two ways: - Occurrences of 'box'/'unbox' emitted by the typechecker are eliminated in the 'ds_app_var' case of GHC.HsToCore.Expr. - Other code that needs to box/unbox emits the appropriate code inline. This includes the big tuple machinery of GHC.Core.Make used by the desugarer (GHC.HsToCore.{Utils,Binds,Arrows,ListComp}) as well as the float-out pass (GHC.Core.Opt.SetLevels). Core Lint checks that no occurrence of 'box'/'unbox' survives desugaring. On the way, we overhaul the litany of big tuple functions by introducing data BigTupleLayout = BoxedElements | BareElements to distinguish the two kinds of "big tuples" that GHC routinely deals with; for example 'mkBigCoreVarTupSolo' becomes 'mkBigCoreVarTup BareElements'. All of this code is moved to the new module GHC.Core.Make.BigTuple. Fixes #20864 #22336 #22473 #25065 #27331 ------------------------- Metric Decrease: T9872a ------------------------- - - - - - 4cf7628a by Evgeny Malyshev at 2026-09-17T02:39:56-04:00 Fix the CompactionFailed documentation link to compact The old Haddock reference links into base instead of ghc-compact. Use an explicit URL because ghc-compact depends on base, not vice versa. Fixes #27558 Assisted-By: OpenAI Codex - - - - - 098bba70 by Facundo Domínguez at 2026-09-17T14:57:41-04:00 Remove the call to hoistFlag from processCmdLineP This call was undesirable because it was causing a reconstruction of the list of flag processors. Even relying on list fusion would not be sufficient because we want to replace the list with a data structure with faster lookups to address #25763. The removal is done in two moves: * We move CmdLineP to CmdLine.hs * Then we move the effect of hoisting to processArgs via a new function hoistEwM - - - - - e01799c7 by Facundo Domínguez at 2026-09-17T14:57:42-04:00 Do not create duplicate flag processors for the -W flag This makes simpler implementing the command line parser with a trie map holding flag processors. If we were to allow duplicate flag processors for any flag, the trie map would need to be a multimap. - - - - - 3875b257 by Facundo Domínguez at 2026-09-17T14:57:42-04:00 Replace the list of flag processors with a trie map in `processArgs` Previously `GHC.Driver.CmdLine.findArg` was called for each command-line argument, doing a linear search on the list of flag processors each time. This was somewhat costly as the list of flag processor has near 2000 elements. A lookup with a trie map is faster in general, but the speed up is only noticeable when calling `GHC.Driver.CmdLine.processArgs` sufficient times, so the amount of lookups piles up. This could happen in large projects with many units each having many dependencies. If only a module needs to be recompiled, the user still needs to wait for all of the flag parsing to complete. The benchmark at testsuite/tests/perf/compiler/cmdline-parser shows a 10x speed up when using the trie. The trie map is implemented in `GHC.Data.StringTrie`. The design is explained in Note [Processing command line argument fast] in GHC.Driver.Session. The commit also: * adds two property-based tests for trie map operations, * adds a benchmark of the command line parser, and * renames the predicate `arg_ok` to `valid_flag_suffix` to decide what flag processor should be used when there are multiple matching prefixes on a flag. Fixes #25763. - - - - - 5236634a by Andreas Klebinger at 2026-09-17T14:58:24-04:00 Compile Word64{Map,Set} with -O2 always. This is the hottest code and even if we build GHC with -O0 otherwise -O2 pays off for these modules. Fixes #27814. - - - - - 0a27641d by Andreas Klebinger at 2026-09-21T10:30:13+00:00 RTS flag: Change setting handling and allowed maximums. GC Generations: Now unconditionally bounded at 64. It was already bounded to 64 for the non-moving RTS but the bound is new for the threaded RTS. Nursery chunking: Instead of overwriting a user set value now we always check if a setting was explicitly set. If so we try to respect it. Max value for RTS flags during parsing: When using decodeSize we now use more accurate maximums. Fixing a number of bugs where we used word size based maximums unconditionally for 32bit fields. GC Generations: We only ever supported 64 generations in the non-threaded RTS so I made this the new explicit maximum. - - - - - 435 changed files: - .gitlab/ci.sh - + changelog.d/25763-cmdline-opt - + changelog.d/27556 - + changelog.d/27627 - + changelog.d/27703 - + changelog.d/27704 - + changelog.d/27717 - + changelog.d/27732 - + changelog.d/T27629 - + changelog.d/T27705 - + changelog.d/T27744 - + changelog.d/T27749 - + changelog.d/T27764 - + changelog.d/T27788-js-selector - + changelog.d/T27830-rts-flag-bounds - + changelog.d/allow-gadt-prefix-con-parens - + changelog.d/boxing-family - + changelog.d/clc-421 - + changelog.d/fix-compacting-gc-constr-27649 - + changelog.d/fix-control0-mask-trampoline - + changelog.d/fix-parallel-gc-selector-race-27477 - + changelog.d/fix-threadlabel-segfault-27618 - + changelog.d/implicit-field-strictness-warning - changelog.d/lazy-field-annotations - + changelog.d/llvm-23 - + changelog.d/ncg-x86-bit-test-instructions - + changelog.d/select-io-manager - compiler/GHC/Builtin.hs - compiler/GHC/Builtin/KnownKeys.hs - compiler/GHC/Builtin/Modules.hs - compiler/GHC/Builtin/Uniques.hs - compiler/GHC/Builtin/WiredIn/Ids.hs - compiler/GHC/Builtin/WiredIn/Prim.hs - compiler/GHC/Builtin/WiredIn/TypeLits.hs - compiler/GHC/Builtin/WiredIn/Types.hs - + compiler/GHC/Builtin/WiredIn/Types/Box.hs - compiler/GHC/Builtin/primops.txt.pp - compiler/GHC/Cmm/DebugBlock.hs - compiler/GHC/CmmToAsm/X86/CodeGen.hs - compiler/GHC/CmmToAsm/X86/Instr.hs - compiler/GHC/CmmToAsm/X86/Ppr.hs - compiler/GHC/Core.hs - compiler/GHC/Core/Coercion.hs - compiler/GHC/Core/Coercion/Axiom.hs - compiler/GHC/Core/DataCon.hs - compiler/GHC/Core/FamInstEnv.hs - compiler/GHC/Core/Lint.hs - compiler/GHC/Core/Make.hs - + compiler/GHC/Core/Make/BigTuple.hs - + compiler/GHC/Core/Make/Box.hs - compiler/GHC/Core/Opt/SetLevels.hs - compiler/GHC/Core/Opt/Specialise.hs - compiler/GHC/Core/Opt/WorkWrap/Utils.hs - compiler/GHC/Core/TyCo/Ppr.hs - compiler/GHC/Core/TyCo/Rep.hs - compiler/GHC/Core/TyCon.hs - compiler/GHC/Core/Type.hs - compiler/GHC/Core/Utils.hs - compiler/GHC/CoreToStg.hs - compiler/GHC/CoreToStg/AddImplicitBinds.hs - compiler/GHC/CoreToStg/Prep.hs - compiler/GHC/Data/FastString.hs - + compiler/GHC/Data/StringTrie.hs - compiler/GHC/Data/Word64Map/Internal.hs - compiler/GHC/Data/Word64Map/Strict/Internal.hs - compiler/GHC/Data/Word64Set/Internal.hs - compiler/GHC/Driver/CmdLine.hs - compiler/GHC/Driver/Flags.hs - compiler/GHC/Driver/GenerateCgIPEStub.hs - compiler/GHC/Driver/Main/Compile.hs - compiler/GHC/Driver/Main/Passes.hs - compiler/GHC/Driver/Session.hs - compiler/GHC/Hs/Decls.hs - compiler/GHC/Hs/Doc.hs - compiler/GHC/Hs/Expr.hs - compiler/GHC/Hs/Extension/Pass.hs - compiler/GHC/Hs/Instances.hs - compiler/GHC/Hs/Pat.hs - compiler/GHC/Hs/Type.hs - compiler/GHC/Hs/Utils.hs - compiler/GHC/HsToCore/Arrows.hs - compiler/GHC/HsToCore/Binds.hs - compiler/GHC/HsToCore/Expr.hs - compiler/GHC/HsToCore/ListComp.hs - compiler/GHC/HsToCore/Quote.hs - compiler/GHC/HsToCore/Utils.hs - compiler/GHC/Iface/Decl.hs - compiler/GHC/Iface/Ext/Ast.hs - compiler/GHC/Iface/Load.hs - compiler/GHC/Iface/Rename.hs - compiler/GHC/Iface/Syntax.hs - compiler/GHC/Iface/Tidy.hs - compiler/GHC/IfaceToCore.hs - compiler/GHC/Parser.y - compiler/GHC/Parser/Annotation.hs - compiler/GHC/Parser/PostProcess.hs - compiler/GHC/Rename/Expr.hs - compiler/GHC/Rename/HsType.hs - compiler/GHC/Rename/Module.hs - compiler/GHC/Stg/Debug.hs - compiler/GHC/Stg/Lint.hs - compiler/GHC/StgToJS/Apply.hs - compiler/GHC/StgToJS/CodeGen.hs - compiler/GHC/StgToJS/Symbols.hs - compiler/GHC/Tc/Deriv.hs - compiler/GHC/Tc/Deriv/Generate.hs - compiler/GHC/Tc/Deriv/Generics.hs - compiler/GHC/Tc/Errors/Ppr.hs - compiler/GHC/Tc/Errors/Types.hs - compiler/GHC/Tc/Gen/Expr.hs - compiler/GHC/Tc/Gen/HsType.hs - compiler/GHC/Tc/Gen/Match.hs - compiler/GHC/Tc/Gen/Pat.hs - compiler/GHC/Tc/Gen/Splice.hs - compiler/GHC/Tc/Instance/Family.hs - compiler/GHC/Tc/Instance/Typeable.hs - compiler/GHC/Tc/Module.hs - compiler/GHC/Tc/Solver/Default.hs - compiler/GHC/Tc/Solver/FunDeps.hs - compiler/GHC/Tc/TyCl.hs - compiler/GHC/Tc/TyCl/Instance.hs - compiler/GHC/Tc/TyCl/PatSyn.hs - compiler/GHC/Tc/Utils/Backpack.hs - compiler/GHC/Types/CompleteMatch.hs - compiler/GHC/Types/Demand.hs - compiler/GHC/Types/Error/Codes.hs - compiler/GHC/Types/Hint.hs - compiler/GHC/Types/Hint/Ppr.hs - compiler/GHC/Types/Id.hs - compiler/GHC/Types/Id/Info.hs - compiler/GHC/Types/Id/Make.hs - compiler/GHC/Types/Literal.hs - compiler/GHC/Types/Tickish.hs - compiler/GHC/Types/TyThing.hs - compiler/GHC/Types/TyThing/Ppr.hs - compiler/GHC/Types/Unique.hs - compiler/Language/Haskell/Syntax/Decls.hs - compiler/Language/Haskell/Syntax/Type.hs - compiler/ghc.cabal.in - configure.ac - docs/users_guide/exts/gadt_syntax.rst - docs/users_guide/exts/strict.rst - docs/users_guide/exts/type_data.rst - docs/users_guide/runtime_control.rst - docs/users_guide/using-warnings.rst - ghc/GHC/Driver/Session/Mode.hs - hadrian/src/Base.hs - hadrian/src/Builder.hs - hadrian/src/Hadrian/Builder.hs - hadrian/src/Hadrian/Builder/Ar.hs - hadrian/src/Hadrian/Oracles/Path.hs - hadrian/src/Hadrian/Utilities.hs - hadrian/src/Oracles/Setting.hs - hadrian/src/Oracles/TestSettings.hs - hadrian/src/Rules/BinaryDist.hs - hadrian/src/Rules/Changelog.hs - hadrian/src/Rules/Codes.hs - hadrian/src/Rules/Lint.hs - hadrian/src/Rules/Nofib.hs - hadrian/src/Rules/Test.hs - libraries/base/src/GHC/Base.hs - libraries/base/src/GHC/Exts.hs - libraries/base/src/GHC/RTS/Flags.hs - libraries/base/tests/all.T - libraries/ghc-internal/ghc-internal.cabal.in - libraries/ghc-internal/include/RtsIfaceSymbols.h - + libraries/ghc-internal/src/GHC/Internal/Box.hs - libraries/ghc-internal/src/GHC/Internal/Conc/IO.hs - libraries/ghc-internal/src/GHC/Internal/Event/Thread.hs - libraries/ghc-internal/src/GHC/Internal/Exts.hs - libraries/ghc-internal/src/GHC/Internal/IO/Exception.hs - libraries/ghc-internal/src/GHC/Internal/RTS/Flags.hsc - libraries/ghc-internal/src/GHC/Internal/TypeNats.hs - libraries/ghc-internal/src/GHC/Internal/Types.hs - libraries/stm - linters/lint-codes/LintCodes/Static.hs - m4/find_python.m4 - + m4/fp_canonicalise_win_path.m4 - m4/fp_find_nm.m4 - m4/fp_find_root.m4 - m4/fp_prog_ar.m4 - m4/fp_prog_ar_args.m4 - m4/fp_prog_sh.m4 - m4/fptools_alex.m4 - m4/fptools_happy.m4 - rts/Capability.c - rts/Continuation.c - rts/ContinuationOps.cmm - rts/HeapStackCheck.cmm - rts/IOManager.c - rts/IOManager.h - rts/IOManagerInternals.h - rts/Interpreter.c - rts/Messages.c - rts/Prelude.h - rts/PrimOps.cmm - rts/Printer.c - rts/ProfHeap.c - rts/RaiseAsync.c - rts/RtsFlags.c - rts/STM.c - rts/Schedule.c - rts/Sparks.c - rts/StableName.c - rts/StgMiscClosures.cmm - rts/ThreadPaused.c - rts/Threads.c - rts/Trace.h - rts/configure.ac - rts/eventlog/EventLog.c - rts/include/rts/Flags.h - rts/include/rts/RtsToHsIface.h - rts/include/rts/storage/Closures.h - rts/include/rts/storage/GC.h - rts/include/stg/MiscClosures.h - rts/posix/Poll.c - rts/posix/Poll.h - rts/posix/Select.c - + rts/posix/SelectBis.c - + rts/posix/SelectBis.h - rts/posix/Timeout.c - rts/posix/Timeout.h - rts/prim/atomic.c - rts/rts.cabal - rts/sm/Compact.c - rts/sm/Evac.c - rts/sm/GC.c - rts/sm/GCUtils.c - rts/sm/MBlock.c - rts/sm/NonMoving.c - rts/sm/NonMovingMark.c - rts/sm/Storage.c - rts/sm/Sweep.c - testsuite/driver/README.md - testsuite/driver/testlib.py - testsuite/tests/MiniQuickCheck.hs - testsuite/tests/arrows/should_run/all.T - + testsuite/tests/arrows/should_run/arrowrun005.hs - + testsuite/tests/arrows/should_run/arrowrun005.stdout - + testsuite/tests/bytecode/T27633/Obj.hs - + testsuite/tests/bytecode/T27633/T27633a.hs - + testsuite/tests/bytecode/T27633/T27633a.stdout - + testsuite/tests/bytecode/T27633/T27633b.hs - + testsuite/tests/bytecode/T27633/T27633b.stdout - + testsuite/tests/bytecode/T27633/all.T - + testsuite/tests/codeGen/should_gen_asm/T25233.asm - + testsuite/tests/codeGen/should_gen_asm/T25233.hs - + testsuite/tests/codeGen/should_gen_asm/T25233b.asm - + testsuite/tests/codeGen/should_gen_asm/T25233b.cmm - testsuite/tests/codeGen/should_gen_asm/all.T - testsuite/tests/codeGen/should_run/all.T - + testsuite/tests/core-to-stg/T27627/Callee.hs - + testsuite/tests/core-to-stg/T27627/Caller.hs - + testsuite/tests/core-to-stg/T27627/Main.hs - + testsuite/tests/core-to-stg/T27627/T27627.stdout - + testsuite/tests/core-to-stg/T27627/all.T - + testsuite/tests/core-to-stg/T27627a/Callee.hs - + testsuite/tests/core-to-stg/T27627a/Caller.hs - + testsuite/tests/core-to-stg/T27627a/Main.hs - + testsuite/tests/core-to-stg/T27627a/T27627a.stdout - + testsuite/tests/core-to-stg/T27627a/all.T - + testsuite/tests/core-to-stg/T27627b/Callee.hs - + testsuite/tests/core-to-stg/T27627b/Caller.hs - + testsuite/tests/core-to-stg/T27627b/Main.hs - + testsuite/tests/core-to-stg/T27627b/T27627b.stdout - + testsuite/tests/core-to-stg/T27627b/all.T - + testsuite/tests/core-to-stg/T27627c/Callee.hs - + testsuite/tests/core-to-stg/T27627c/Caller.hs - + testsuite/tests/core-to-stg/T27627c/Main.hs - + testsuite/tests/core-to-stg/T27627c/T27627c.stdout - + testsuite/tests/core-to-stg/T27627c/all.T - + testsuite/tests/core-to-stg/T27627e.hs - + testsuite/tests/core-to-stg/T27627e.stdout - + testsuite/tests/core-to-stg/T27627f/Callee.hs - + testsuite/tests/core-to-stg/T27627f/Caller.hs - + testsuite/tests/core-to-stg/T27627f/Inst.hs - + testsuite/tests/core-to-stg/T27627f/Main.hs - + testsuite/tests/core-to-stg/T27627f/T27627f.stdout - + testsuite/tests/core-to-stg/T27627f/all.T - + testsuite/tests/core-to-stg/T27704/Callee.hs - + testsuite/tests/core-to-stg/T27704/Callee.hs-boot - + testsuite/tests/core-to-stg/T27704/Main.hs - + testsuite/tests/core-to-stg/T27704/Mid.hs - + testsuite/tests/core-to-stg/T27704/T27704.stdout - + testsuite/tests/core-to-stg/T27704/all.T - + testsuite/tests/core-to-stg/T27704a/Callee.hs - + testsuite/tests/core-to-stg/T27704a/Callee.hs-boot - + testsuite/tests/core-to-stg/T27704a/Main.hs - + testsuite/tests/core-to-stg/T27704a/Mid.hs - + testsuite/tests/core-to-stg/T27704a/T27704a.stdout - + testsuite/tests/core-to-stg/T27704a/all.T - + testsuite/tests/core-to-stg/T27717/Callee.hs - + testsuite/tests/core-to-stg/T27717/Callee.hs-boot - + testsuite/tests/core-to-stg/T27717/Main.hs - + testsuite/tests/core-to-stg/T27717/Mid.hs - + testsuite/tests/core-to-stg/T27717/T27717.stdout - + testsuite/tests/core-to-stg/T27717/Ty.hs - + testsuite/tests/core-to-stg/T27717/all.T - testsuite/tests/core-to-stg/all.T - testsuite/tests/count-deps/CountDepsParser.stdout - + testsuite/tests/deSugar/should_compile/T25065a.hs - testsuite/tests/deSugar/should_compile/all.T - + testsuite/tests/deSugar/should_run/T20864.hs - + testsuite/tests/deSugar/should_run/T20864.stdout - + testsuite/tests/deSugar/should_run/T25065b.hs - + testsuite/tests/deSugar/should_run/T25065b.stdout - testsuite/tests/deSugar/should_run/all.T - testsuite/tests/driver/all.T - + testsuite/tests/driver/stringtrie.hs - + testsuite/tests/driver/stringtrie.stdout - testsuite/tests/ffi/should_run/T21305.hs - − testsuite/tests/gadt/T14320.stderr - testsuite/tests/gadt/T18191.hs - testsuite/tests/gadt/T18191.stderr - + testsuite/tests/gadt/T27423a.hs - + testsuite/tests/gadt/T27423b.hs - + testsuite/tests/gadt/T27423b.stderr - testsuite/tests/gadt/all.T - testsuite/tests/ghc-api/T25121_status.stdout - + testsuite/tests/ghci.debugger/scripts/T27633c.hs - + testsuite/tests/ghci.debugger/scripts/T27633c.script - + testsuite/tests/ghci.debugger/scripts/T27633c.stdout - + testsuite/tests/ghci.debugger/scripts/T27633c_obj.hs - testsuite/tests/ghci.debugger/scripts/all.T - + testsuite/tests/indexed-types/should_run/T27331.hs - + testsuite/tests/indexed-types/should_run/T27331.stdout - + testsuite/tests/indexed-types/should_run/T27331b.hs - + testsuite/tests/indexed-types/should_run/T27331b.stdout - + testsuite/tests/indexed-types/should_run/T27331b_Plugin.hs - testsuite/tests/indexed-types/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/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/javascript/T27788.hs - + testsuite/tests/javascript/T27788.stdout - testsuite/tests/javascript/all.T - testsuite/tests/linters/notes.stdout - testsuite/tests/parser/should_compile/DumpParsedAstComments.stderr - testsuite/tests/parser/should_compile/DumpSemis.stderr - + testsuite/tests/patsyn/should_compile/T27744.hs - testsuite/tests/patsyn/should_compile/all.T - + testsuite/tests/perf/compiler/T25763.stderr - testsuite/tests/perf/compiler/all.T - testsuite/tests/perf/compiler/large-project/all.T - testsuite/tests/perf/should_run/T3586.hs - testsuite/tests/perf/should_run/T3586.stdout - testsuite/tests/perf/space_leaks/all.T - testsuite/tests/printer/Makefile - + testsuite/tests/printer/T27423c.hs - testsuite/tests/printer/Test20297.stdout - testsuite/tests/printer/all.T - testsuite/tests/rename/should_fail/RnStaticPointersFail01.stderr - testsuite/tests/rename/should_fail/RnStaticPointersFail03.stderr - testsuite/tests/rename/should_fail/T26545.stderr - + testsuite/tests/rts/T27477.hs - + testsuite/tests/rts/T27477.stdout - + testsuite/tests/rts/T27618.hs - + testsuite/tests/rts/T27618.stdout - + testsuite/tests/rts/T27649.hs - + testsuite/tests/rts/T27649.stdout - testsuite/tests/rts/all.T - + testsuite/tests/rts/continuations/T27651.hs - + testsuite/tests/rts/continuations/T27651.stdout - testsuite/tests/rts/continuations/all.T - testsuite/tests/rts/rtsflags001.stderr-ws-32 - testsuite/tests/rts/rtsflags001.stderr-ws-64 - testsuite/tests/simplCore/should_compile/Makefile - testsuite/tests/simplCore/should_compile/T17966.stderr - + testsuite/tests/simplCore/should_compile/T27556.hs - + testsuite/tests/simplCore/should_compile/T27556.script - + testsuite/tests/simplCore/should_compile/T27629.hs - + testsuite/tests/simplCore/should_compile/T27629.stderr - + testsuite/tests/simplCore/should_compile/T27629Plugin.hs - + testsuite/tests/simplCore/should_compile/T27749.hs - + testsuite/tests/simplCore/should_compile/T27749.stderr - testsuite/tests/simplCore/should_compile/T7785.stderr - testsuite/tests/simplCore/should_compile/all.T - testsuite/tests/simplCore/should_compile/spec004.hs - testsuite/tests/simplCore/should_compile/spec004.stderr - + testsuite/tests/simplCore/should_run/T27703/Lib.hs - + testsuite/tests/simplCore/should_run/T27703/Main.hs - + testsuite/tests/simplCore/should_run/T27703/T27703.stdout - + testsuite/tests/simplCore/should_run/T27703/all.T - + testsuite/tests/simplCore/should_run/T27705.hs - + testsuite/tests/simplCore/should_run/T27705.stdout - + testsuite/tests/simplCore/should_run/T27705_Inst.hs - testsuite/tests/simplCore/should_run/all.T - testsuite/tests/th/T17380.stderr - testsuite/tests/th/T18612.stderr - + testsuite/tests/th/T27034.hs - + testsuite/tests/th/T27034.stderr - testsuite/tests/th/T8761.stderr - testsuite/tests/th/all.T - + testsuite/tests/type-data/should_fail/T27732a.hs - + testsuite/tests/type-data/should_fail/T27732a.stderr - + testsuite/tests/type-data/should_fail/T27732b.hs - + testsuite/tests/type-data/should_fail/T27732b.stderr - + testsuite/tests/type-data/should_fail/T27732c.hs - + testsuite/tests/type-data/should_fail/T27732c.stderr - + testsuite/tests/type-data/should_fail/T27732d.hs - + testsuite/tests/type-data/should_fail/T27732d.stderr - + testsuite/tests/type-data/should_fail/T27732e.hs - + testsuite/tests/type-data/should_fail/T27732e.stderr - + testsuite/tests/type-data/should_fail/T27732f.hs - + testsuite/tests/type-data/should_fail/T27732f.stderr - testsuite/tests/type-data/should_fail/TDStrictnessGADT.stderr - testsuite/tests/type-data/should_fail/TDStrictnessH98.stderr - testsuite/tests/type-data/should_fail/all.T - + testsuite/tests/typecheck/should_compile/T27664.hs - testsuite/tests/typecheck/should_compile/all.T - + testsuite/tests/warnings/should_compile/T16836a.hs - + testsuite/tests/warnings/should_compile/T16836a.stderr - + testsuite/tests/warnings/should_compile/T16836b.hs - + testsuite/tests/warnings/should_compile/T16836c.hs - + testsuite/tests/warnings/should_compile/T16836c.stderr - + testsuite/tests/warnings/should_compile/T16836d.hs - + testsuite/tests/warnings/should_compile/T16836d.stderr - testsuite/tests/warnings/should_compile/all.T - + testsuite/tests/warnings/should_fail/WExpectedNoArgError.stderr - testsuite/tests/warnings/should_fail/all.T - utils/check-exact/ExactPrint.hs - utils/check-exact/Utils.hs - utils/deriveConstants/Main.hs - utils/ghc-toolchain/src/GHC/Toolchain/Program.hs - utils/haddock/haddock-api/src/Haddock/Backends/Hoogle.hs - utils/haddock/haddock-api/src/Haddock/Convert.hs - utils/haddock/haddock-api/src/Haddock/GhcUtils.hs - utils/haddock/haddock-api/src/Haddock/Interface/Rename.hs - utils/haddock/haddock-api/src/Haddock/Types.hs - utils/hsc2hs - utils/jsffi/dyld.mjs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/a027e4976fc1b4d414be9f4e80d3a5… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/a027e4976fc1b4d414be9f4e80d3a5… You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc][wip/apk/rts-flag-fixes] 2 commits: Specialise: Stop looping on recursive dictionaries in interestingDict
by Andreas Klebinger (＠AndreasK) 21 Sep '26

21 Sep '26

Andreas Klebinger pushed to branch wip/apk/rts-flag-fixes at Glasgow Haskell Compiler / GHC Commits: 7f71dbae by Andreas Klebinger at 2026-09-21T09:32:55+00:00 Specialise: Stop looping on recursive dictionaries in interestingDict interestingDict now doesn't look through loopbreaker unfoldings. Doing so would cause infinite loops on certain dictionaries. Fixes #27705. - - - - - a027e497 by Andreas Klebinger at 2026-09-21T10:27:39+00:00 RTS flag: Change setting handling and allowed maximums. GC Generations: Now unconditionally bounded at 64. It was already bounded to 64 for the non-moving RTS but the bound is new for the threaded RTS. Nursery chunking: Instead of overwriting a user set value now we always check if a setting was explicitly set. If so we try to respect it. Max value for RTS flags during parsing: When using decodeSize we now use more accurate maximums. Fixing a number of bugs where we used word size based maximums unconditionally for 32bit fields. GC Generations: We only ever supported 64 generations in the non-threaded RTS so I made this the new explicit maximum. - - - - - 15 changed files: - + changelog.d/T27705 - + changelog.d/T27830-rts-flag-bounds - compiler/GHC/Core/Opt/Specialise.hs - docs/users_guide/runtime_control.rst - rts/RtsFlags.c - rts/include/rts/Flags.h - rts/include/rts/storage/GC.h - rts/sm/GC.c - rts/sm/Storage.c - testsuite/tests/rts/rtsflags001.stderr-ws-32 - testsuite/tests/rts/rtsflags001.stderr-ws-64 - + testsuite/tests/simplCore/should_run/T27705.hs - + testsuite/tests/simplCore/should_run/T27705.stdout - + testsuite/tests/simplCore/should_run/T27705_Inst.hs - testsuite/tests/simplCore/should_run/all.T Changes: ===================================== changelog.d/T27705 ===================================== @@ -0,0 +1,5 @@ +section: compiler +synopsis: Fixed an issue that caused the specializer to sometimes loop on recursive dictionary superclasses. +issues: #27705 +mrs: !16559 + ===================================== changelog.d/T27830-rts-flag-bounds ===================================== @@ -0,0 +1,5 @@ +section: rts +synopsis: Fix bugs in RTS flags handling: RTS Flags now respects -n even with large -A args and errors give more accurate bounds on valid value. +issues: #27830 #27829 +mrs: !16713 + ===================================== compiler/GHC/Core/Opt/Specialise.hs ===================================== @@ -3120,8 +3120,8 @@ interestingDict :: SpecEnv -> CoreExpr -> Bool -- This is a subtle and important function -- See Note [Interesting dictionary arguments] interestingDict env (Var v) -- See (ID3) and (ID5) + -- (ID6.a) Might fail for loop breaker dicts but that seems fine. | Just rhs <- maybeUnfoldingTemplate (idUnfolding v) - -- Might fail for loop breaker dicts but that seems fine. = interestingDict env rhs interestingDict env arg -- Main Plan: use exprIsConApp_maybe @@ -3136,9 +3136,9 @@ interestingDict env arg -- Main Plan: use exprIsConApp_maybe , isIPClass cls -- See (ID5) -> False - -- Otherwise we are unwrapping a unary type class + -- Shouldn't happen. | otherwise - -> exprIsHNF arg -- See (ID7) + -> pprTraceDebug "shouldn't happen anymore" (ppr arg) $ exprIsHNF arg -- See (ID7) | Just (_, _, data_con, _tys, args) <- exprIsConApp_maybe in_scope_env arg , Just cls <- tyConClass_maybe (dataConTyCon data_con) @@ -3152,7 +3152,8 @@ interestingDict env arg -- Main Plan: use exprIsConApp_maybe where arg_ty = exprType arg definitely_not_ip_like = not (couldBeIPLike arg_ty) - in_scope_env = ISE (substInScopeSet $ se_subst env) realIdUnfolding + -- idUnfolding rather than realIdUnfolding: See (ID6.a) + in_scope_env = ISE (substInScopeSet $ se_subst env) idUnfolding {- Note [Ticks on applications] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -3268,11 +3269,27 @@ case we can clearly specialise. But there are wrinkles: (Remember: a constraint tuple is just a class with N superclasses and no methods.) See discussion on #26831. -(ID7) A unary (single-method) class is currently represented by (meth |> co). We - will unwrap the cast (see (ID5)) and then want to reply "yes" if the method - has any struture. We rather arbitrarily use `exprIsHNF` for this. (We plan a - new story for unary classes, see #23109, and this special case will become - irrelevant.) +(ID6.a) If we deal with a recursive dictionary as in #27705 we want to avoid + infinite recursion while recursing into superclasses. + + For example we might have: + + class D1 a => D2 a + class D2 a => D1 a + + The primary concern is that we want to avoid looping on recursive instances. + We can achieve this by simply not looking through loop breakers by using idUnfolding + rather than realIdUnfolding. + + It's possible that this prevents specialization of edge cases that have loop breakers + in their recursive loop. But even if we can find a dictionary like this the simplifier + won't look through loopbreaker dictionaries either killing any potential benefit. + So while we could handle this case via a already-seen set or fuel we simply don't bother + for now. + +(ID7) A unary (single-method) class is currently handled by the same path as regular dicts + since they are represented by faking a regular Dictionary. + See Note [Unary class magic] for the details. (ID8) Sadly, if `exprIsConApp_maybe` says Nothing, we still want to treat a non-trivial argument as interesting. In T19695 we have this: ===================================== docs/users_guide/runtime_control.rst ===================================== @@ -635,10 +635,11 @@ performance. Set the number of generations used by the garbage collector. The default of 2 seems to be good, but the garbage - collector can support any number of generations. Anything larger + collector can in theory support any number of generations. Anything larger than about 4 is probably not a good idea unless your program runs for a *long* time, because the oldest generation will hardly ever - get collected. + get collected. Currently the RTS hardcodes a limit of 64 generations which + seems plenty. Specifying 1 generation with ``+RTS -G1`` gives you a simple 2-space collector, as you would expect. In a 2-space collector, the :rts-flag:`-A ===================================== rts/RtsFlags.c ===================================== @@ -141,8 +141,8 @@ void initRtsFlagsDefaults(void) if (maxStkSize == 0) maxStkSize = 8 * 1024 * 1024; // GcFlags.maxStkSiz is 32-bit, so we need to cap to prevent overflow (#17019) - else if (maxStkSize > UINT32_MAX * sizeof(W_)) - maxStkSize = UINT32_MAX * sizeof(W_); + else if (maxStkSize > (StgWord64) UINT32_MAX * sizeof(W_)) + maxStkSize = (StgWord64) UINT32_MAX * sizeof(W_); RtsFlags.GcFlags.statsFile = NULL; RtsFlags.GcFlags.giveStats = NO_GC_STATS; @@ -155,7 +155,7 @@ void initRtsFlagsDefaults(void) /* -A default. See #16499 for a discussion about the tradeoffs */ RtsFlags.GcFlags.minAllocAreaSize = (4 * 1024 * 1024) / BLOCK_SIZE; RtsFlags.GcFlags.largeAllocLim = 0; /* defaults to minAllocAreasize */ - RtsFlags.GcFlags.nurseryChunkSize = 0; + RtsFlags.GcFlags.nurseryChunkSize = -1; /* -1: Nothing set by user, normalized to off by default, 0: off explicitly, <n>: explicit size*/ RtsFlags.GcFlags.minOldGenSize = (1024 * 1024) / BLOCK_SIZE; /* -O default */ RtsFlags.GcFlags.maxHeapSize = 0; /* off by default */ RtsFlags.GcFlags.heapLimitGrace = (1024 * 1024); @@ -1239,19 +1239,19 @@ error = true; if (rts_argv[arg][2] == 'L') { RtsFlags.GcFlags.largeAllocLim = decodeSize(rts_argv[arg], 3, 2*BLOCK_SIZE, - HS_INT_MAX) / BLOCK_SIZE; + (StgWord64) HS_WORD32_MAX * BLOCK_SIZE) / BLOCK_SIZE; } else { // minimum two blocks in the nursery, so that we have one // to grab for allocate(). RtsFlags.GcFlags.minAllocAreaSize = decodeSize(rts_argv[arg], 2, 2*BLOCK_SIZE, - HS_INT_MAX) / BLOCK_SIZE; + (StgWord64) HS_WORD32_MAX * BLOCK_SIZE) / BLOCK_SIZE; } break; case 'n': OPTION_UNSAFE; RtsFlags.GcFlags.nurseryChunkSize - = decodeSize(rts_argv[arg], 2, 2*BLOCK_SIZE, HS_INT_MAX) + = decodeSize(rts_argv[arg], 2, 0, ((StgWord64) HS_INT32_MAX) * BLOCK_SIZE) / BLOCK_SIZE; break; @@ -1302,7 +1302,7 @@ error = true; case 'K': OPTION_UNSAFE; RtsFlags.GcFlags.maxStkSize = - decodeSize(rts_argv[arg], 2, 0, UINT32_MAX) + decodeSize(rts_argv[arg], 2, 0, (StgWord64) UINT32_MAX * sizeof(W_)) / sizeof(W_); break; @@ -1311,22 +1311,22 @@ error = true; switch(rts_argv[arg][2]) { case 'c': RtsFlags.GcFlags.stkChunkSize = - decodeSize(rts_argv[arg], 3, sizeof(W_), HS_WORD_MAX) + decodeSize(rts_argv[arg], 3, sizeof(W_), (StgWord64)HS_WORD32_MAX * sizeof(W_)) / sizeof(W_); break; case 'b': RtsFlags.GcFlags.stkChunkBufferSize = - decodeSize(rts_argv[arg], 3, sizeof(W_), HS_WORD_MAX) + decodeSize(rts_argv[arg], 3, sizeof(W_), (StgWord64)HS_WORD32_MAX * sizeof(W_)) / sizeof(W_); break; case 'i': RtsFlags.GcFlags.initialStkSize = - decodeSize(rts_argv[arg], 3, sizeof(W_), HS_WORD_MAX) + decodeSize(rts_argv[arg], 3, sizeof(W_), (StgWord64)HS_WORD32_MAX * sizeof(W_)) / sizeof(W_); break; default: RtsFlags.GcFlags.initialStkSize = - decodeSize(rts_argv[arg], 2, sizeof(W_), HS_WORD_MAX) + decodeSize(rts_argv[arg], 2, sizeof(W_), (StgWord64)HS_WORD32_MAX * sizeof(W_)) / sizeof(W_); break; } @@ -1339,7 +1339,7 @@ error = true; decodeSize(rts_argv[arg], 8, BLOCK_SIZE, HS_WORD_MAX); } else { RtsFlags.GcFlags.maxHeapSize = - decodeSize(rts_argv[arg], 2, BLOCK_SIZE, HS_WORD_MAX) + decodeSize(rts_argv[arg], 2, BLOCK_SIZE, (StgWord64) HS_WORD32_MAX * BLOCK_SIZE) / BLOCK_SIZE; // user give size in *bytes* but "maxHeapSize" is in // *blocks* @@ -1388,8 +1388,9 @@ error = true; #endif case 'G': OPTION_UNSAFE; - RtsFlags.GcFlags.generations = - decodeSize(rts_argv[arg], 2, 1, HS_INT_MAX); + // Capped at 64 by hardcoded array size in non-threaded RTS. + RtsFlags.GcFlags.generations = (uint32_t) + decodeSize(rts_argv[arg], 2, 1, GC_MAX_GENERATIONS); break; case 'H': @@ -1398,7 +1399,7 @@ error = true; RtsFlags.GcFlags.heapSizeSuggestionAuto = true; } else { RtsFlags.GcFlags.heapSizeSuggestion = (uint32_t) - (decodeSize(rts_argv[arg], 2, BLOCK_SIZE, HS_WORD_MAX) + (decodeSize(rts_argv[arg], 2, BLOCK_SIZE, (StgWord64) HS_WORD32_MAX * BLOCK_SIZE) / BLOCK_SIZE); } break; @@ -1407,7 +1408,7 @@ error = true; OPTION_UNSAFE; RtsFlags.GcFlags.minOldGenSize = (uint32_t)(decodeSize(rts_argv[arg], 2, BLOCK_SIZE, - HS_WORD_MAX) + (StgWord64) HS_WORD32_MAX * BLOCK_SIZE) / BLOCK_SIZE); break; @@ -1994,9 +1995,25 @@ static void normaliseRtsOpts (void) RtsFlags.GcFlags.minAllocAreaSize = RtsFlags.GcFlags.maxHeapSize; } - // If we have -A16m or larger, use -n4m. - if (RtsFlags.GcFlags.minAllocAreaSize >= (16*1024*1024) / BLOCK_SIZE) { - RtsFlags.GcFlags.nurseryChunkSize = (4*1024*1024) / BLOCK_SIZE; + // If no explicit size was given, and we have -A16m or larger, use -n4m. + if (RtsFlags.GcFlags.nurseryChunkSize == -1) { + if (RtsFlags.GcFlags.minAllocAreaSize >= (16*1024*1024) / BLOCK_SIZE) { + RtsFlags.GcFlags.nurseryChunkSize = (4*1024*1024) / BLOCK_SIZE; + } else { + RtsFlags.GcFlags.nurseryChunkSize = 0; + } + } + else if ( RtsFlags.GcFlags.nurseryChunkSize > 0 && RtsFlags.GcFlags.nurseryChunkSize < 2) { + errorBelch("nursery chunk size (-n) must be at least %" FMT_Word " large.", (W_)(2 * BLOCK_SIZE)); + errorBelch("Disabling nursery chunking"); + RtsFlags.GcFlags.nurseryChunkSize = 0; + } + // If the user gave a chunk size respect it, unless it's larger than + // minimum allocation area. + else if ( (StgWord64) RtsFlags.GcFlags.nurseryChunkSize > (StgWord64) RtsFlags.GcFlags.minAllocAreaSize) { + errorBelch("nursery chunk size (-n) is bigger than minimum alloc area size (-A)"); + errorBelch("Disabling nursery chunking"); + RtsFlags.GcFlags.nurseryChunkSize = 0; } if (RtsFlags.ParFlags.parGcLoadBalancingGen == ~0u) { @@ -2207,9 +2224,7 @@ decodeSize(const char *flag, uint32_t offset, StgWord64 min, StgWord64 max) val = (StgWord64)m; if (m < 0 || val < min || val > max) { - // printf doesn't like 64-bit format specs on Windows - // apparently, so fall back to unsigned long. - errorBelch("error in RTS option %s: size outside allowed range (%" FMT_Word " - %" FMT_Word ")", flag, (W_)min, (W_)max); + errorBelch("error in RTS option %s: size outside allowed range (%" FMT_Word64 " - %" FMT_Word64 ")", flag, (StgWord64)min, (StgWord64)max); stg_exit(EXIT_FAILURE); } ===================================== rts/include/rts/Flags.h ===================================== @@ -45,7 +45,7 @@ typedef struct _GC_FLAGS { uint32_t maxHeapSize; /* in *blocks* */ uint32_t minAllocAreaSize; /* in *blocks* */ uint32_t largeAllocLim; /* in *blocks* */ - uint32_t nurseryChunkSize; /* in *blocks* */ + int32_t nurseryChunkSize; /* in *blocks*, int to distinguish default off, vs explicit off */ uint32_t minOldGenSize; /* in *blocks* */ uint32_t heapSizeSuggestion; /* in *blocks* */ bool heapSizeSuggestionAuto; @@ -80,7 +80,7 @@ typedef struct _GC_FLAGS { * to handle the exception before we * raise it again. */ - StgWord heapLimitGrace; /* units: *blocks* + StgWord heapLimitGrace; /* units: *bytes* * After a HeapOverflow exception has * been raised, how much extra space is * given to the thread to handle the ===================================== rts/include/rts/storage/GC.h ===================================== @@ -52,6 +52,8 @@ // ie. StgWord. Note that we have had some tricky int overflows in a // couple of cases caused by using ints rather than longs (e.g. #5086) +#define GC_MAX_GENERATIONS 64 + typedef StgWord memcount; typedef struct nursery_ { ===================================== rts/sm/GC.c ===================================== @@ -154,7 +154,7 @@ static Condition gc_exit_leave_now_cv; #else // THREADED_RTS // Must match the alignment of gen_workspace. -StgWord8 the_gc_thread[sizeof(gc_thread) + 64 * sizeof(gen_workspace)] +StgWord8 the_gc_thread[sizeof(gc_thread) + GC_MAX_GENERATIONS * sizeof(gen_workspace)] ATTRIBUTE_ALIGNED(GEN_WORKSPACE_ALIGNMENT); #endif // THREADED_RTS ===================================== rts/sm/Storage.c ===================================== @@ -273,7 +273,7 @@ void storageAddCapabilities (uint32_t from, uint32_t to) if (RtsFlags.GcFlags.nurseryChunkSize == 0) { new_n_nurseries = to; } else { - memcount total_alloc = to * RtsFlags.GcFlags.minAllocAreaSize; + memcount total_alloc = to * (size_t) RtsFlags.GcFlags.minAllocAreaSize; new_n_nurseries = stg_max(to, total_alloc / RtsFlags.GcFlags.nurseryChunkSize); } ===================================== testsuite/tests/rts/rtsflags001.stderr-ws-32 ===================================== @@ -1 +1 @@ -rtsflags001: error in RTS option -H0m: size outside allowed range (4096 - 4294967295) +rtsflags001: error in RTS option -H0m: size outside allowed range (4096 - 17592186040320) ===================================== testsuite/tests/rts/rtsflags001.stderr-ws-64 ===================================== @@ -1 +1 @@ -rtsflags001: error in RTS option -H0m: size outside allowed range (4096 - 18446744073709551615) +rtsflags001: error in RTS option -H0m: size outside allowed range (4096 - 17592186040320) ===================================== testsuite/tests/simplCore/should_run/T27705.hs ===================================== @@ -0,0 +1,9 @@ +module Main where + +import T27705_Inst + +-- The dictionaries (D1/D2) are mutually recursive. We have to watch +-- out for the specializer looping on them. This was first detected in #22802 +-- but no test was added, which caused it to break again #27705 :( +main :: IO () +main = print (b (3 :: Int)) ===================================== testsuite/tests/simplCore/should_run/T27705.stdout ===================================== @@ -0,0 +1 @@ +42 ===================================== testsuite/tests/simplCore/should_run/T27705_Inst.hs ===================================== @@ -0,0 +1,13 @@ +{-# LANGUAGE UndecidableInstances, UndecidableSuperClasses, FlexibleInstances #-} +module T27705_Inst where + +-- The two dictionaries are mutually recursive, and we have to ensure the specialiser +-- doesn't loop when it's peaking through their unfoldings. +class D2 a => D1 a +class D1 a => D2 a +instance D2 Int => D1 Int +instance D1 Int => D2 Int + +{-# NOINLINE b #-} +b :: D1 a => a -> Int +b _ = 42 ===================================== testsuite/tests/simplCore/should_run/all.T ===================================== @@ -123,3 +123,5 @@ test('T24359b', normal, compile_and_run, ['-O']) test('T23429', normal, compile_and_run, ['-O']) test('T27071', normal, compile_and_run, ['-O -fworker-wrapper-cbv']) test('T27005', [], multimod_compile_and_run, ['T27005', '-O']) +test('T27705', [extra_hc_opts('+RTS -M500M -RTS')], multimod_compile_and_run, + ['T27705', '-O2 -fexpose-all-unfoldings']) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/575bb98eb289b1aac31d112c8f6d5d… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/575bb98eb289b1aac31d112c8f6d5d… You're receiving this email because of your account on gitlab.haskell.org. 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[Git][ghc/ghc][wip/apk/rts-flag-fixes] 68 commits: Specialise: Stop looping on recursive dictionaries in interestingDict
by Andreas Klebinger (＠AndreasK) 21 Sep '26

21 Sep '26

Andreas Klebinger pushed to branch wip/apk/rts-flag-fixes at Glasgow Haskell Compiler / GHC Commits: 578bd185 by Andreas Klebinger at 2026-08-29T07:16:05-04:00 Specialise: Stop looping on recursive dictionaries in interestingDict interestingDict now doesn't look through loopbreaker unfoldings. Doing so would cause infinite loops on certain dictionaries. Fixes #27705. - - - - - 7bf546fc by Simon Peyton Jones at 2026-08-31T23:48:53-04:00 Never make an absent filler for a constraint type mkAbsentFiller used isTerminatingType to decide, but that is not enough. Consider class Eq a => UC a where {} let u :: UC Int -- UC Int is a "non-terminating type" u = error "Absent" let e :: Eq Int -- Eq Int is a "terminating type" e = $p1UC u We clearly must not make a filler for `e`, because we speculatively evaluate it. But speculatively evaluating `e` forces `u`, so we must not make one for `u` either. Asking isDictTy instead is not enough either, because it does not catch a constraint hidden behind an unreduced type family application: type family F a :: Constraint type instance F W = TC W a :: F W => Int -> Int -- (F W) argument is absent Oops! Entered absent arg Arg: irred Type: F W So play safe and use isPredTy: never make an absent filler for any constraint-kinded type. Fixes #27627 - - - - - 5f474953 by Zubin Duggal at 2026-08-31T23:48:53-04:00 Add tests for absent fillers at dictionary types T27627 a unary class whose superclass is a non-unary class T27627a ...whose superclass is a Constraint-kinded type family T27627b ...whose superclass is a quantified constraint T27627c a unary class applied to itself, (UC (UC (TC a))) T27627e a (forall b. P b) dictionary that loops - - - - - cd5c6bcc by Zubin Duggal at 2026-08-31T23:48:53-04:00 An abstract TyCon may hide a unary class A class declared in an hs-boot file is an AbstractTyCon inside the module loop, and compiling the real declaration may reveal it to be a UnaryClassTyCon. - isTerminatingType returned True for such AbstractTyCons - IfaceToCore set the unary flag to False in the DFunId So we could end up speculating bottom dictionaries because inside a module loop we see an UnaryClassTyCon as an AbstractTyCon Use isTerminatingTyCon, which returns False for an abstract TyCon. The Bool in DFunId is now a cache for isTerminatingTyCon, set in mkDFunIdDetails. Fixes #27704 - - - - - abfc224a by Zubin Duggal at 2026-08-31T23:48:53-04:00 Specialise: don't replace dead args with absent fillers specHeader decides an argument is dead by calling isDeadBinder on a binder of the /optimised RHS/, then applies the filler to the /stable unfolding/ template instead. The two may differ, so the argument can be dead in the RHS and not in the template. The specialised function's unfolding then has an absent filler, and any call site that inlines it evaluates the error thunk. Dropping dead args in the specialiser is rarely worth it, to quote Simon, "The later worker/wrapper pass will pick up the dead arg later if it is really dead. Keeps the specialiser simpler." So instead of trying to check if the arg really is dead in the stable unfolding, just drop the logic for dropping dead args in the specialiser altogeher. Fixes #27703 - - - - - 1557fd1c by Zubin Duggal at 2026-08-31T23:48:53-04:00 CorePrep: don't speculate a call across an hs-boot edge We take care not to evaluate things that might be bottom, like a looping dictionary group, but our analysis is defeated by boot files. We only track recursion within a module, so two dictionaries that depend on each other across a module loop each look non-recursive, and we might speculate them. Any recursion we cannot see must cross an hs-boot edge, so refuse to speculate calls that cross one. Fixes #27717 - - - - - 4117e5ae by Wolfgang Jeltsch at 2026-08-31T23:49:35-04:00 Incorporate the `rethrowSTM` reexport into the `stm` submodule - - - - - 4bfbf5c8 by ARATA Mizuki at 2026-09-01T18:55:08-04:00 testsuite: Fix out-of-bounds access in T3586 unsafeRead and unsafeWrite use 0-based index. Looking at #3586, the expected output seems to be 2.8e8. Addresses #27596 - - - - - 3f9db6d4 by ARATA Mizuki at 2026-09-01T18:55:08-04:00 testsuite: Fix out-of-bounds access in T21305 writeInt64Array# takes an index measured in units of Int64 elements. Fixes #27596 - - - - - 44d7788f by Simon Peyton Jones at 2026-09-01T18:55:53-04:00 Fix buglet in INLINE-arity calculation for pattern synonyms This fixes #27744. The buglet was accidentally introduced by commit 3a0f9a51c1dacc474c7fd128082edd8bf4081256 Author: Simon Peyton Jones <simon.peytonjones(a)gmail.com> Date: Sat Aug 1 00:13:02 2026 +0100 Fix three bugs related to required type args and INLINE pragmas I failed to find all the calls to `addInlinePragArity`! - - - - - df058f1d by Simon Jakobi at 2026-09-02T07:18:06-04:00 testsuite: Migrate perf tests off collect_compiler_stats('all') The 'all' metric argument applies a single tolerance to bytes allocated, max_bytes_used and peak_megabytes_allocated, although their noise profiles are incompatible (#27653): allocations are nearly deterministic, residency needs 10-20%, and peak is quantized to 1 MB. Any single tolerance is too tight for one metric or too slack for another. This migrates the remaining users of 'all' (and of the 'all' default) to explicit per-metric collection, ahead of removing 'all' from the driver. peak_megabytes_allocated is dropped everywhere: its 1 MB granularity makes tight relative windows meaningless (#27613), and it is sensitive to GC timing. In #27489 it drifted by -5.3% while max_bytes_used moved by less than 0.1%. Where a test guards a memory property, max_bytes_used covers it at byte granularity. Where the motivating ticket was about compile-time memory (T11545, T15304, T26425), residency remains gated via max_bytes_used, now with a residency-appropriate tolerance. max_bytes_used is dropped where residency was only ever an accident of 'all': * T15630, T15630a, T20261: the underlying tickets (#15630, #20261) contain no memory data at all. One is a simplifier-ticks blowup and the other is stated entirely in allocation numbers, so the 20% window never had teeth. * T21839c: #21839's measurements show residency essentially flat (+0.16%) while allocations moved +7%, so allocations are the discriminating metric. They are already gated at 1% via collect_compiler_runtime. The ghc/max gate had previously broken CI spuriously (9fd11585eb widened it from 1% to 10% for that reason). Allocation tolerances are tightened to the testsuite's conventional 2% where 'all' previously left them at 10-20%. Assisted-by: Claude Fable 5 - - - - - 72dd2432 by Simon Jakobi at 2026-09-02T07:18:06-04:00 testsuite: Remove the 'all' metric argument of collect_stats 'all' gated bytes allocated, max_bytes_used and peak_megabytes_allocated at a single tolerance, although their noise profiles are incompatible, making such tests either flaky or toothless (#27653). Closes #27653. Assisted-by: Claude Fable 5 - - - - - 2228cb30 by Simon Jakobi at 2026-09-02T07:18:06-04:00 testsuite: Make the deviation argument of collect_stats mandatory Almost every caller passes an explicit tolerance matched to the metric's noise profile, and the silent 20% default is far slacker than 'bytes allocated' merits. Only two tests relied on it. They now state their tolerance explicitly: large-project gets 10%, in line with other large compile-time tests. T9848 gets 2%: its metric is byte-for-byte deterministic across CI jobs and platforms of a given test_env, has drifted only about 2.5% since 2015, and the fusion failure it guards against would show up as a roughly +30000% jump. Assisted-by: Claude Fable 5 - - - - - 56291fc5 by Cheng Shao at 2026-09-02T07:18:45-04:00 autoconf/ghc-toolchain: bump llvm upper bound to support llvm 23 This commit bumps llvm upper bound to support llvm 23. - - - - - 20eb3f41 by Cheng Shao at 2026-09-02T07:18:45-04:00 rts: fix compilation issues with clang 23 clang 23 has broadened `-Wall`/`-Wextra` ranges, exposing some minor issues in the rts when building with validate flavours: - Unused locals - `#pragma GCC diagnostic pop` mismatch This commit fixes those. - - - - - 9e7739ab by Simon Jakobi at 2026-09-03T13:45:43-04:00 Add -Wimplicit-field-strictness (#16836) This opt-in warning fires when a data constructor field lacks an explicit strictness annotation (`!` or `~`). It complements the LazyFieldAnnotations extension (4762a8bf30f) from GHC proposal 752, which makes `~` annotations available for this purpose. Deciding which fields to report requires their levity, so the check runs after typechecking. To keep the noise down, the diagnostic is emitted once per data declaration, grouped by constructor. Closes #16836. Assisted-by: Claude Fable 5 - - - - - 6a44d591 by mangoiv at 2026-09-03T13:46:22-04:00 simplifier: remove a bogus `assert` in `rebuild_app'` in `GHC.CoreToStg.Prep.cpeApp`. Prior to this commit commit 08bc245be70d95801bc1138804ed1de9474fbdc0 Author: sheaf <sam.derbyshire(a)gmail.com> Date: Sat Feb 28 16:30:43 2026 +0100 Clean up join points, casts & ticks This commit shores up the logic dealing with casts and ticks occurring in between a join point binding and a jump any `PlaceRuntime` ticks we observed were profiling ticks, even though that isn't necessary. The more liberal rules in the above commit allow e.g. breakpoint ticks (which are valid PlaceRuntime ticks) to legitimately appear in an argument position. Fixes #27556 - - - - - eaa95a6f by Andrei Borzenkov at 2026-09-04T08:08:40-04:00 Parentheses in prefix GADT constructors (#27423) Updated `splitLHsGadtTy` to allow looking through the parentheses for inner binders. General example of a code pattern that's allowed now: data S a where MkS :: (forall a. S a) That should work now with any combination of nested foralls and parentheses. We don't perform parenthesis unwrapping for record GADT constructors in accordance with GHC Proposal #402. To this end `con_inner_bndrs` no longer stores plain forall telescopes: `[HsForAllTelescope pass]` is replaced with `[LHsGadtTelescope pass]`, a new `HsArg`-style type whose `HsGadtForAll` holds an inner telescope and whose `HsGadtPar` holds a pair of parentheses. The parentheses carry no meaning for renaming or type checking; the only reason to record them is exact-printing. Updated `pprConDecl` to improve the `parse == parse . ppr . parse` property of GADT pretty-printing. The pretty printer can now output code that's similar to this: data T a where MkT1 :: (forall a. T a) MkT2 :: forall . forall a. T a These are special cases of inner forall binders for prefix GADT constructors, when we have either implicit or zero explicit outer binders. - - - - - 639456a8 by Evgeny Malyshev at 2026-09-04T08:09:25-04:00 HsPat: Add spacing to unary tuple patterns Use hsep when printing unary boxed TuplePat applications so that the MkSolo constructor is separated from its argument. The old hcat rendered wildcard and parenthesized arguments as MkSolo_ and MkSolo(). Add T27034 to exercise the HsPat splice-dump path with wildcard and variable arguments, and update existing affected golden output. Fixes #27034 Assisted-By: OpenAI Codex - - - - - 2908ab36 by Simon Jakobi at 2026-09-05T07:22:17-04:00 X86 NCG: use btr/bts/btc for single-bit operations Previously the Cmm patterns x & ~(1 << i) x | (1 << i) x ^ (1 << i) compiled to mov/shl/not/and-style sequences of 3-4 instructions. Now they compile to a single btr, bts or btc, matching what C compilers produce. When the bit index is a literal, constant folding has already collapsed these patterns into ones with a literal mask, such as x & 0xfffffeffffffffff for x & ~(1 << 40). Such masks are now also compiled to a bit-test instruction when they don't fit in an imm32 and would otherwise have to be loaded into a register first. For a variable bit index, this applies only when the shift is unchecked (uncheckedShiftL#, Data.Bits.unsafeShiftL): the bounds-checked shiftL used by e.g. the default clearBit/setBit/complementBit implementations wraps the shift in a bounds mask that this optimisation does not see through. With a literal index, the bounds mask is constant-folded away, so the checked operations benefit too. See Note [Bit-test instructions] in GHC.CmmToAsm.X86.CodeGen. Fixes #25233. Assisted-by: Claude Fable 5 - - - - - c673ecf0 by Simon Peyton Jones at 2026-09-05T07:22:59-04:00 Move HsStatic free-var test to typechecker A `static` form should have no free *term* variables, but it can have free *type* variables. Alas, the renamer does not really know what is a term variable and what is a type variable, because of required type arguments. This patch moves the test to the typechecker, which does know. Addresses #27664 - - - - - 5939ceaf by sheaf at 2026-09-05T22:06:18-04:00 Windows: enforce path convention in ./configure As detailed in Note [MSYS paths] in Hadrian.Utilities, the standing convention (using Windows-style paths with forward slashes) is now enforced in ./configure instead of within Hadrian, removing the need for 'cygpath' calls within Hadrian. Fixes #26683 - - - - - a6061455 by sheaf at 2026-09-05T22:06:18-04:00 Hadrian: introduce ExeSpawnPath Specific details about the filepath used to specify the executable to spawn with CreateProcess matters on Windows: whether we use forward or backward slashes, a leading ./, or an absolute path changes how the executable is found. This commit introduces 'ExeSpawnPath' which is a path that is guaranteed to be found when spawning a process. All command invocations now go through this type to ensure the path has been properly sanitised. See Note [NeedCurrentDirectoryForExePath] in Hadrian.Utilities. The same treatment is applied to hsc2hs. Updates hsc2hs submodule. - - - - - e28313e3 by sheaf at 2026-09-05T22:07:06-04:00 Preserve tick ordering in 'tickTickedExpr' 'GHC.Core.Utils.tickTickedExpr' tries to combine a tick 't1' into an existing stack of ticks 't2s'. There are two situations: 1. 't1' is subsumed by a tick in 't2s': drop it. 2. A tick in 't2s' is subsumed by 't1', say 't2'. This commit ensures that in case (2) we keep 't1' on the outside instead of replacing 't2' at its position in the stack. This avoids re-ordering source notes (which was the cause of #27749). This fixes a regression introduced in 2dadf3b0d05. Fixes #27749 - - - - - 3172f557 by sheaf at 2026-09-05T22:07:06-04:00 Consistently prefer local source note ticks GHC.Cmm.DebugBlock.cmmDebugGen (DWARF annotations) and GHC.Stg.Debug.quickSourcePos (-finfo-table-map) both contained logic to prioritise source note ticks from the current module. This commit commons up this logic and propagates it to a third consumer: IPE stack frames, in GHC.Driver.GenerateCgIPEStub. See the new function GHC.Types.Tickish.bestSourceNote. - - - - - 192be0b6 by Luite Stegeman at 2026-09-07T19:43:36-04:00 rts: fix ctoi_tuple_spill_words getting out of sync Fix a few places that were not updating ctoi_tuple_spill_words correctly, leading to corruption/crashes when dealing with large unboxed tuples in bytecode: - captureContinuationAndAbort - findRetryFrameHelper/findAtomicallyFrameHelper - interpretBCO bci_BRK_FUN fixes #27633 - - - - - 604eb43c by Simon Jakobi at 2026-09-07T19:44:15-04:00 Hadrian: don't capture the testsuite driver's output (#27780) a6061455d54 switched the Testsuite RunTest case from Shake's cmd to the cmd' wrapper. cmd' always captures stdout and stderr, and since the caller asks for Exit, it returns without dumping what it captured. As a result the testsuite output no longer appears in CI job logs: failures, performance metrics and the summary were lost with the job. Use cmdExe, the uncaptured cmd, as the other plain-cmd sites in that commit do. Fixes #27780. Assisted-by: Claude Fable 5.1 - - - - - 06eee015 by Luite Stegeman at 2026-09-08T06:03:06+02:00 rts: Fix missing memory barrier in eval_thunk_selector (#27477) unchain_thunk_selectors() was missing an ACQUIRE_LOAD for the indirectee, leading to segfaults and corruption during GC on weakly-ordered architectures. Fixes #27477 - - - - - f8b2bd8f by Alan Zimmerman at 2026-09-08T09:39:12-04:00 EPA Fix HsCmdDo exact print with comments Exact printing of HsCmdDo was ignoring the location for the do statements, and this is an annotation that can have comments in it. Update it so we print the statements as a unit, including any comments. Also add the result of auditing that we capture comments in all needed places, noting that the remaining Anno SrcSpan instances are benign. - - - - - 430967ab by Duncan Coutts at 2026-09-09T11:07:01+01:00 Reorder cmm decls in HeapStackCheck for a better logical grouping And put more section headers in to deliniate the groups. We're about to add more here, so better to organise it first. - - - - - 344080fd by Duncan Coutts at 2026-09-09T11:07:01+01:00 Add raisePrimIOException and add it to RTS<->ghc-internal API The raisePrimIOException is a new helper function that I/O primops will use to help them report I/O errors. This is implemented in Haskell (since that's a lot easier), but has a calling convention that is easy(ish) to use from Cmm in the I/O primops. So we add it to the RTS API struct, and since we'll use it from Cmm we also need a field accessor macro for cmm (in deriveConstants). See the Note about how we cannot have nice things due to async exceptions and thunks preventing us from using catch. - - - - - cfdb3399 by Duncan Coutts at 2026-09-09T11:07:01+01:00 Add new blocking functions for I/O primops See the Note [Thread blocking for new I/O primops], and the Note [Calling convention for raisePrimIOException]. The point is, it will allow us to report synchronous exceptions from I/O primops, and do so much more flexibly. Previously the I/O managers could only report async exceptions and only nullary exceptions. This was OK historically, but no good as we add more I/O managers and expand the range of I/O operations we support. - - - - - f09c09d8 by Duncan Coutts at 2026-09-09T11:07:01+01:00 Change the encoding of results from the I/O manager to I/O primops Previously we just had async continue or heap overflow. We now extend what we can report with synchronous success, and synchronous failure with an errno. See Note [Encoding of result of I/O manager operations] We don't use these two new cases yet, but we will. In particular an epoll I/O manager needs to be able to report synchronous success or failure for waitRead#/waitWrite#. - - - - - 30f074d9 by Duncan Coutts at 2026-09-09T11:07:01+01:00 Switch waitRead/Write# to use new blocking return frames and update the I/O managers to set the result before resuming the blocked threads. This makes it possible for I/O managers to report synchronous exceptions from the I/O primops, but that will be done in a subsequent commit. - - - - - a8786ced by Duncan Coutts at 2026-09-09T11:07:01+01:00 Switch Poll and Select I/O managers to report sync exceptions rather than using raiseAsync with blockedOnBadFD_closure. This uses the new mechanism in the blocking frame return code to report synchronous exceptions. - - - - - 7a9df79a by Duncan Coutts at 2026-09-09T11:07:01+01:00 Remove now-unused blockedOnBadFD It was previously thrown by the select and poll I/O managers, but now they use raisePrimIOException (with an EBADF errno). - - - - - 6b0424e3 by Duncan Coutts at 2026-09-09T11:07:01+01:00 Improve the docs for delay# waitRead# and waitWrite# Document that the waitRead/Write# can throw exceptions (this was true before too), and that all of them are async exception cancellation points. - - - - - afeb2c30 by Duncan Coutts at 2026-09-09T20:08:58-04:00 Enable printf warnings for trace functions and fix resulting warnings Most of the existing printf-style functions are annotated with attributes to enable gcc/clang warnings for the printf format string, but several trace functions in Trace.h were missing this annotation. Enable them, and fix the resulting warnings. - - - - - 9a442c93 by Alan Zimmerman at 2026-09-09T20:09:36-04:00 EPA: Exact print ConDeclGADT without custom enterAnn !16321 brought in explicit capture of parens in a ConDeclGADT. The ExactPrint update introduced a modification of the fundamental function in exact printing, `enterAnn`, by splitting it into a version allowing injection of functionality normally handled by the ExactPrint class methods. This commit refactors that code, to restore the prior `enterAnn` version, by following the convention in ExactPrint of introducing a helper data structure with its own `ExactPrint` instance to achieve the same effect. - - - - - 4e9297ea by Simon Jakobi at 2026-09-11T08:32:45-04:00 ci: Actually pass --ignore-perf-failures to the testsuite driver 684c0018d9 changed the IGNORE_PERF_FAILURES handling to append to RUNTEST_ARGS with bash array syntax, but the three use sites still expand RUNTEST_ARGS as a scalar, which yields only the first array element. The appended flag was therefore dropped in every job, so perf improvements kept failing Marge Bot batches and master pipelines, contrary to #19562. Append as a string instead, matching the existing --force-colors append in test_hadrian. Fixes #27563. Assisted-by: Claude Fable 5.1 - - - - - 4f78dfdf by Simon Jakobi at 2026-09-11T08:33:24-04:00 testsuite: Give T26537 a 1.5x compile timeout Its -fregs-graph compile step tends to time out in unoptimized builds (#27188, #27776). Assisted-by: Claude Fable 5.1 - - - - - 130286e3 by Alan Zimmerman at 2026-09-11T08:34:08-04:00 EPA: Remove ListBanana / ListParens from AnnListBrackets This is a step towards making AnnList only represent lists of items which can have either braces or layout. - - - - - a9827d13 by Simon Jakobi at 2026-09-11T18:53:32-04:00 Reject ~, UNPACK and multiplicity annotations on type data fields Only `!` was rejected so far. `~`, UNPACK and multiplicity annotations were silently accepted. None of them make sense at the type level, so restriction (R3) of Note [Type data declarations] now covers all of them. Fixes #27732. Assisted-by: Claude Fable 5.1 - - - - - c71d5e23 by Alan Zimmerman at 2026-09-11T18:54:11-04:00 EPA: Add a Note for the exact print main loop - - - - - 7a108e43 by Simon Jakobi at 2026-09-12T18:35:59-04:00 FastString: Drop mkFastStringWith's constructor callback All three callers passed the same callback, a partial application of mkNewFastStringShortByteString to the string being interned. That partial application is allocated as a closure before the table lookup, on the common hit path too, although the callback is needed only after a miss. Drop the parameter and call mkNewFastStringShortByteString directly after a miss. Since nothing is passed "with" anymore, rename the function to internSB. Suggested by Simon PJ in #27528: https://gitlab.haskell.org/ghc/ghc/-/work_items/27528#note_687031 Assisted-by: Claude Fable 5 - - - - - 82c73b22 by Alan Zimmerman at 2026-09-12T18:36:38-04:00 EPA: More targeted HsDo exact print annotation HsDo is multi-purpose, as encoded in its HsDoFlavour field. Some of these are in a layout context (DoExpr, MDoExpr), others are not (ListComp, MonadComp). We are moving towards using AnnList only in layout contexts, so we switch the HsDo TTG annotation from holding an AnnList for this, to holding Either (EpToken "[", EpToken "]") AnnList This also allows us to trim down AnnListBrackets to only have braces or None, thereby opening the door for unification with the existing layout context data type EpLayout. - - - - - 749d2448 by Luite Stegeman at 2026-09-15T14:07:01-04:00 rts: handle large CONSTR closures in compacting GC The function update_fwd_large in the compacting GC could run into an unexpected object with the following error: internal error: update_fwd_large: unknown/strange object 1 Closure type 1 is CONSTR. This patch adds cases for CONSTR and CONSTR_NOCAF. This is the same problem as #27434 (large AP closures, fixed by cca0d58963), which missed this case. Fixes #27649 - - - - - 177d6155 by Luite Stegeman at 2026-09-15T14:07:02-04:00 testsuite: fix T27434 test with compacting GC Ensure that the interpreter is actually run with the compacting GC - - - - - 5796aa63 by Luite Stegeman at 2026-09-15T14:07:49-04:00 rts: initialise the stack frame header for mask_frame and apply_mask_frame We must leave the stack in consistent state before jumping to mask_frame or apply_mask_frame because they may result. Failing to do so could lead to a crash if there were waiting exceptions. Fixes #27651 - - - - - 2486cc92 by Simon Peyton Jones at 2026-09-15T14:08:36-04:00 Re-introduce the "weird SpecDict" case In this commit commit f80375dd4945350a1d784e436975b48b9c736eaf Author: Simon Peyton Jones <simon.peytonjones(a)gmail.com> Date: Sun Jun 29 15:26:58 2025 +0100 Refactor of Specialise.hs I removed a test for a dictionary with unbound type variables. This turned out to be wrong; see #27629. So this MR re-introduces it. - - - - - 8e09a46f by Duncan Coutts at 2026-09-15T20:11:35-04:00 Refactor (and rename) removeFromQueues, to simplify I/O managers Rename it to unblockAndAppendToRunQueue which better reflects what it is intended to do. The post-condition for unblockAndAppendToRunQueue is that the TSO is on the run queue or it is in the process of migrating to another cap. Previously it achieved that by always directly adding the TSO to the run queue itself. But this actually made things more complicated for the I/O managers, because it meant they needed a separate code path for notifying for cancellation compared to notifying for completion. The general notification code would always add the TSO to the run queue itself. So the improvement is to allow different cases in unblockAndAppendToRunQueue to achieve the same outcome in different ways: either directly adding to the run queue or calling helper functions that do so themselves. This then allows the new I/O managers to share code between the sync and async cancellation, and to reuse their notifyIOCompletion helpers for cancellation. This avoids a source of bugs where the completion path may be updated but the cancellation path may be forgotten, or similarly in future for sync/async operations. Update all the existing in-RTS I/O managers, and the posix timeout code. - - - - - d668782c by Duncan Coutts at 2026-09-15T20:11:35-04:00 Document that awaitCompletedTimeoutsOrIO expects an empty run queue This was true before but implicit and not relied on much. It's better to be explicit, and allow things to depend on it. - - - - - 11d938bb by Duncan Coutts at 2026-09-15T20:11:35-04:00 Store the I/O opcode and fd in the StgAsyncIOOp This will be useful in several I/O managers and it is handy for logging and debugging. It also doesn't increase the size of the StgAsyncIOOp structure. There was enough spare padding space already. Update the poll I/O manager to set the new fields. Add a helper function to convert the enum IOReadOrWrite into the enum IOOpCode. Also change IOReadOrWrite to be an enum without a typedef, for consistency with other enumerations in IOManager.h - - - - - bfa87882 by Duncan Coutts at 2026-09-15T20:11:36-04:00 Add a new I/O manager based on select() Yes, this is the second such I/O manager, but it is a modern re-implementation based on the new in-RTS I/O manager infrastructure. So it is cleaner and faster than the old select I/O manager. Why do we need another I/O manager based on select? Why isn't the poll() one good enough as a baseline portable unix I/O manager? Because macOS. Apple Inc. is why we cannot have nice things. The man page for poll on macOS documents the fact that it does not work. At least, it does not work for all files. Specifically, it does not work for device files. Whereas macOS select() does work for device files. Aaaaarg! We _do_ want to deprecate and remove the old select I/O manager, but due to macOS we cannot do that until we have a replacement. This is that replacement. Until of course a nice new k-queue I/O manager arrives, which could become the new default for macOS and FreeBSD. Interestingly, this select I/O manager is actually faster than the poll one, on Linix, in some circumstances: specifically when many Haskell threads are waiting on the same fd. The poll I/O manager does O(n) work for n threads waiting on I/O, whereas the select one does O(fds) work for the number of fds that threads are waiting on. Usually this is 1:1, so it's not noticable, but one can concoct extreme benchmarks to show the difference. - - - - - 8e9de15a by Duncan Coutts at 2026-09-15T20:11:36-04:00 Minor updates in the poll I/O manager to keep in sync with select This keeps it in sync with select one. The changes are based on code review while implementing the new select I/O manager. The two I/O managers are so similar in structure that it makes sense to try to minimise the diff between them. This should aid understanding, and fixes to both in future. - - - - - 222668bb by Duncan Coutts at 2026-09-15T20:11:36-04:00 Document the new select I/O manager in the user guide in the RTS section about I/O managers. And add a changelog entry. - - - - - 0f48735b by Cheng Shao at 2026-09-15T20:12:23-04:00 Revert "wasm: workaround WebKit bug in dyld" This reverts commit c9b8465c2c338176fcab9d197e9d31f4aee11f68. The underlying webkit bug has been fixed in https://commits.webkit.org/314219@main. Closes #27564. - - - - - 809294f1 by Luite Stegeman at 2026-09-15T20:13:08-04:00 rts: make stg_threadLabelzh return a valid pointer for unlabeled threads. This fixes a segfault in the GC caused by stg_threadLabelzh returning a 0 pointer in a GC pointer field. stg_threadLabelzh returns a tuple of type (# Int#, ByteArray# #). If a thread has no label, the second field is unused. We must still return a valid heap object pointer. Instead of returning 0, we now return stg_DEAD_SLOT_closure. fixes #27618 - - - - - e2d57026 by Luite Stegeman at 2026-09-15T20:13:54-04:00 JS: fix selector thunk handling fix a bug where entering a selector thunk could lead to a crash if the selected field was still a thunk. fixes #27788 - - - - - 1b4a622f by sheaf at 2026-09-17T02:39:13-04:00 Improvements to type/data family handling This commit makes several improvements to the treatment of type and data families in GHC: - We consistently use "type family" instead of "type synonym family" to avoid a confusion with type synonyms. For example: - OpenSynFamilyTyCon ==> OpenTypeFamilyTyCon - ClosedSynFamilyTyCon => ClosedTypeFamilyTyCon - Various functions that were specific to data families have been renamed to make this clear. For example: - tyConFamInst_maybe ==> tyConDataFamInst_maybe - isFamInstTyCon ==> isDataFamInstTyCon - 'FamTyConFlav' has been refactored so that all closed type families share a single 'ClosedTypeFamilyTyCon' constructor. The corresponding 'IfaceFamTyConFlav' type was updated similarly. This is then used to tidy up the implementation of GHC.Core.FamInstEnv.reduceTyFamApp_maybe. - - - - - c5aa9098 by sheaf at 2026-09-17T02:39:13-04:00 Small refactor of lookupFamInstEnv This commit reworks the code for looking up family instances in GHC.Core.FamInstEnv, reducing duplication a little bit. No change in behaviour. - - - - - a3ad4588 by sheaf at 2026-09-17T02:39:14-04:00 Use a type family for boxing unboxed types This commit overhauls the way in which unboxed types are boxed, as per the updated Note [Boxing constructors] in GHC.Builtin.WiredIn.Types.Box. The main change is to allow boxing to be parametrised by representation, e.g. making 'Box ty' a valid type. We achieve this by implementing 'Box' using a closed type family: newtype Box (a :: TYPE r) = Box (BoxTF r) type BoxTF :: RuntimeRep -> Type type family BoxTF r where BoxTF IntRep = BoxInt BoxTF Int8Rep = BoxInt8 BoxTF WordRep = BoxWord BoxTF LiftedRep = Any @Type BoxTF (TupleRep [r1, r2]) = (BoxTF r1, BoxTF r2) ... BoxTF (SumRep rs) = BoxSum rs This new design solves the following problems: - It allows boxing a type whose 'RuntimeRep' has not yet been determined (e.g. because we only learn the 'RuntimeRep' after constraint solving). That is, 'Box @r a' is a perfectly valid type even if 'r' is an unfilled metavariable. This is a requirement to fix #25065 (in which we need to box a type whose 'RuntimeRep' is only filled in during constraint solving). - It handles boxing of unboxed tuples and unboxed sums, via recursive boxing. See Note [Boxing TupleRep and SumRep] in GHC.Builtin.WiredIn.Types.Box. 'Box', 'BoxTF' and all of the boxing data constructors are defined in a new 'ghc-internal' module, 'GHC.Internal.Box'. This module contains nothing but wired-in declarations, and GHC never loads its interface on account of a wired-in thing (GHC.Builtin.Modules.isWiredInOnlyModule); see Note [Loading instances for wired-in things] in GHC.Iface.Load. The individual boxing data constructors are deliberately left as an internal implementation detail, and not exported. The intended API is via the two new magic 'Id's: box :: forall {r} (a :: TYPE r). a -> Box a unbox :: forall {r} (a :: TYPE r). Box a -> a exported from 'GHC.PrimOps' (in 'ghc-experimental'). The old boxing data types (IntBox, WordBox, FloatBox, DoubleBox, DictBox) are no longer exported from base (CLC proposal #421). We use this new design to consistently desugar: - parallel comprehensions (GHC.HsToCore.ListComp.{deListComp,dsMcStmt}) - then/group/using statements (GHC.HsToCore.ListComp.{dsTransStmt,dsMcStmt}) - recursive do blocks (mdo/rec) (GHC.HsToCore.Expr.dsDo) - arrows (GHC.HsToCore.Arrows) by consistently using 'box'/'unbox' to deal with unboxed types being put into big tuples. We also adapt 'GHC.Tc.Gen.Match.{tcMcStmt,tcDoStmt}' to create fresh /representation-polymorphic/ type variables for the binders that we are going to put into a big tuple (previously, GHC only allowed lifted types in that position). These desugaring of box and unbox is explained in Note [Desugaring box & unbox] in GHC.Core.Make.Box. Roughly speaking, the desugaring looks like: box @r @ty e ==> K e unbox @r @ty e ==> case e of K x -> x where 'K' is the boxing data constructor at RuntimeRep 'r'. It's slightly more complicated than that in practice: we first need to insert a cast (see Note [The canonical type of a RuntimeRep]) using the new 'CanonicalProv' 'UnivCoProvenance', and unboxed tuples/sums need recursive logic explained in Note [box/unbox for unboxed tuples and sums], including a specific 'BoxSum' datatypes for unboxed sum (which also needed a wired-in type-level list indexing type family (!!)). The desugaring happens in two ways: - Occurrences of 'box'/'unbox' emitted by the typechecker are eliminated in the 'ds_app_var' case of GHC.HsToCore.Expr. - Other code that needs to box/unbox emits the appropriate code inline. This includes the big tuple machinery of GHC.Core.Make used by the desugarer (GHC.HsToCore.{Utils,Binds,Arrows,ListComp}) as well as the float-out pass (GHC.Core.Opt.SetLevels). Core Lint checks that no occurrence of 'box'/'unbox' survives desugaring. On the way, we overhaul the litany of big tuple functions by introducing data BigTupleLayout = BoxedElements | BareElements to distinguish the two kinds of "big tuples" that GHC routinely deals with; for example 'mkBigCoreVarTupSolo' becomes 'mkBigCoreVarTup BareElements'. All of this code is moved to the new module GHC.Core.Make.BigTuple. Fixes #20864 #22336 #22473 #25065 #27331 ------------------------- Metric Decrease: T9872a ------------------------- - - - - - 4cf7628a by Evgeny Malyshev at 2026-09-17T02:39:56-04:00 Fix the CompactionFailed documentation link to compact The old Haddock reference links into base instead of ghc-compact. Use an explicit URL because ghc-compact depends on base, not vice versa. Fixes #27558 Assisted-By: OpenAI Codex - - - - - 098bba70 by Facundo Domínguez at 2026-09-17T14:57:41-04:00 Remove the call to hoistFlag from processCmdLineP This call was undesirable because it was causing a reconstruction of the list of flag processors. Even relying on list fusion would not be sufficient because we want to replace the list with a data structure with faster lookups to address #25763. The removal is done in two moves: * We move CmdLineP to CmdLine.hs * Then we move the effect of hoisting to processArgs via a new function hoistEwM - - - - - e01799c7 by Facundo Domínguez at 2026-09-17T14:57:42-04:00 Do not create duplicate flag processors for the -W flag This makes simpler implementing the command line parser with a trie map holding flag processors. If we were to allow duplicate flag processors for any flag, the trie map would need to be a multimap. - - - - - 3875b257 by Facundo Domínguez at 2026-09-17T14:57:42-04:00 Replace the list of flag processors with a trie map in `processArgs` Previously `GHC.Driver.CmdLine.findArg` was called for each command-line argument, doing a linear search on the list of flag processors each time. This was somewhat costly as the list of flag processor has near 2000 elements. A lookup with a trie map is faster in general, but the speed up is only noticeable when calling `GHC.Driver.CmdLine.processArgs` sufficient times, so the amount of lookups piles up. This could happen in large projects with many units each having many dependencies. If only a module needs to be recompiled, the user still needs to wait for all of the flag parsing to complete. The benchmark at testsuite/tests/perf/compiler/cmdline-parser shows a 10x speed up when using the trie. The trie map is implemented in `GHC.Data.StringTrie`. The design is explained in Note [Processing command line argument fast] in GHC.Driver.Session. The commit also: * adds two property-based tests for trie map operations, * adds a benchmark of the command line parser, and * renames the predicate `arg_ok` to `valid_flag_suffix` to decide what flag processor should be used when there are multiple matching prefixes on a flag. Fixes #25763. - - - - - 5236634a by Andreas Klebinger at 2026-09-17T14:58:24-04:00 Compile Word64{Map,Set} with -O2 always. This is the hottest code and even if we build GHC with -O0 otherwise -O2 pays off for these modules. Fixes #27814. - - - - - 575bb98e by Andreas Klebinger at 2026-09-21T12:19:21+02:00 RTS flag: Change setting handling and allowed maximums. GC Generations: Now unconditionally bounded at 64. It was already bounded to 64 for the non-moving RTS but the bound is new for the threaded RTS. Nursery chunking: Instead of overwriting a user set value now we always check if a setting was explicitly set. If so we try to respect it. Max value for RTS flags during parsing: When using decodeSize we now use more accurate maximums. Fixing a number of bugs where we used word size based maximums unconditionally for 32bit fields. GC Generations: We only ever supported 64 generations in the non-threaded RTS so I made this the new explicit maximum. - - - - - 435 changed files: - .gitlab/ci.sh - + changelog.d/25763-cmdline-opt - + changelog.d/27556 - + changelog.d/27627 - + changelog.d/27703 - + changelog.d/27704 - + changelog.d/27717 - + changelog.d/27732 - + changelog.d/T27629 - + changelog.d/T27705 - + changelog.d/T27744 - + changelog.d/T27749 - + changelog.d/T27764 - + changelog.d/T27788-js-selector - + changelog.d/allow-gadt-prefix-con-parens - + changelog.d/boxing-family - + changelog.d/clc-421 - + changelog.d/fix-compacting-gc-constr-27649 - + changelog.d/fix-control0-mask-trampoline - + changelog.d/fix-parallel-gc-selector-race-27477 - + changelog.d/fix-threadlabel-segfault-27618 - + changelog.d/implicit-field-strictness-warning - changelog.d/lazy-field-annotations - + changelog.d/llvm-23 - + changelog.d/ncg-x86-bit-test-instructions - + changelog.d/select-io-manager - compiler/GHC/Builtin.hs - compiler/GHC/Builtin/KnownKeys.hs - compiler/GHC/Builtin/Modules.hs - compiler/GHC/Builtin/Uniques.hs - compiler/GHC/Builtin/WiredIn/Ids.hs - compiler/GHC/Builtin/WiredIn/Prim.hs - compiler/GHC/Builtin/WiredIn/TypeLits.hs - compiler/GHC/Builtin/WiredIn/Types.hs - + compiler/GHC/Builtin/WiredIn/Types/Box.hs - compiler/GHC/Builtin/primops.txt.pp - compiler/GHC/Cmm/DebugBlock.hs - compiler/GHC/CmmToAsm/X86/CodeGen.hs - compiler/GHC/CmmToAsm/X86/Instr.hs - compiler/GHC/CmmToAsm/X86/Ppr.hs - compiler/GHC/Core.hs - compiler/GHC/Core/Coercion.hs - compiler/GHC/Core/Coercion/Axiom.hs - compiler/GHC/Core/DataCon.hs - compiler/GHC/Core/FamInstEnv.hs - compiler/GHC/Core/Lint.hs - compiler/GHC/Core/Make.hs - + compiler/GHC/Core/Make/BigTuple.hs - + compiler/GHC/Core/Make/Box.hs - compiler/GHC/Core/Opt/SetLevels.hs - compiler/GHC/Core/Opt/Specialise.hs - compiler/GHC/Core/Opt/WorkWrap/Utils.hs - compiler/GHC/Core/TyCo/Ppr.hs - compiler/GHC/Core/TyCo/Rep.hs - compiler/GHC/Core/TyCon.hs - compiler/GHC/Core/Type.hs - compiler/GHC/Core/Utils.hs - compiler/GHC/CoreToStg.hs - compiler/GHC/CoreToStg/AddImplicitBinds.hs - compiler/GHC/CoreToStg/Prep.hs - compiler/GHC/Data/FastString.hs - + compiler/GHC/Data/StringTrie.hs - compiler/GHC/Data/Word64Map/Internal.hs - compiler/GHC/Data/Word64Map/Strict/Internal.hs - compiler/GHC/Data/Word64Set/Internal.hs - compiler/GHC/Driver/CmdLine.hs - compiler/GHC/Driver/Flags.hs - compiler/GHC/Driver/GenerateCgIPEStub.hs - compiler/GHC/Driver/Main/Compile.hs - compiler/GHC/Driver/Main/Passes.hs - compiler/GHC/Driver/Session.hs - compiler/GHC/Hs/Decls.hs - compiler/GHC/Hs/Doc.hs - compiler/GHC/Hs/Expr.hs - compiler/GHC/Hs/Extension/Pass.hs - compiler/GHC/Hs/Instances.hs - compiler/GHC/Hs/Pat.hs - compiler/GHC/Hs/Type.hs - compiler/GHC/Hs/Utils.hs - compiler/GHC/HsToCore/Arrows.hs - compiler/GHC/HsToCore/Binds.hs - compiler/GHC/HsToCore/Expr.hs - compiler/GHC/HsToCore/ListComp.hs - compiler/GHC/HsToCore/Quote.hs - compiler/GHC/HsToCore/Utils.hs - compiler/GHC/Iface/Decl.hs - compiler/GHC/Iface/Ext/Ast.hs - 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compiler/GHC/Tc/TyCl/Instance.hs - compiler/GHC/Tc/TyCl/PatSyn.hs - compiler/GHC/Tc/Utils/Backpack.hs - compiler/GHC/Types/CompleteMatch.hs - compiler/GHC/Types/Demand.hs - compiler/GHC/Types/Error/Codes.hs - compiler/GHC/Types/Hint.hs - compiler/GHC/Types/Hint/Ppr.hs - compiler/GHC/Types/Id.hs - compiler/GHC/Types/Id/Info.hs - compiler/GHC/Types/Id/Make.hs - compiler/GHC/Types/Literal.hs - compiler/GHC/Types/Tickish.hs - compiler/GHC/Types/TyThing.hs - compiler/GHC/Types/TyThing/Ppr.hs - compiler/GHC/Types/Unique.hs - compiler/Language/Haskell/Syntax/Decls.hs - compiler/Language/Haskell/Syntax/Type.hs - compiler/ghc.cabal.in - configure.ac - docs/users_guide/exts/gadt_syntax.rst - docs/users_guide/exts/strict.rst - docs/users_guide/exts/type_data.rst - docs/users_guide/runtime_control.rst - docs/users_guide/using-warnings.rst - ghc/GHC/Driver/Session/Mode.hs - hadrian/src/Base.hs - hadrian/src/Builder.hs - hadrian/src/Hadrian/Builder.hs - hadrian/src/Hadrian/Builder/Ar.hs - hadrian/src/Hadrian/Oracles/Path.hs - hadrian/src/Hadrian/Utilities.hs - hadrian/src/Oracles/Setting.hs - hadrian/src/Oracles/TestSettings.hs - hadrian/src/Rules/BinaryDist.hs - hadrian/src/Rules/Changelog.hs - hadrian/src/Rules/Codes.hs - hadrian/src/Rules/Lint.hs - hadrian/src/Rules/Nofib.hs - hadrian/src/Rules/Test.hs - libraries/base/src/GHC/Base.hs - libraries/base/src/GHC/Exts.hs - libraries/base/src/GHC/RTS/Flags.hs - libraries/base/tests/all.T - libraries/ghc-internal/ghc-internal.cabal.in - libraries/ghc-internal/include/RtsIfaceSymbols.h - + libraries/ghc-internal/src/GHC/Internal/Box.hs - libraries/ghc-internal/src/GHC/Internal/Conc/IO.hs - libraries/ghc-internal/src/GHC/Internal/Event/Thread.hs - libraries/ghc-internal/src/GHC/Internal/Exts.hs - libraries/ghc-internal/src/GHC/Internal/IO/Exception.hs - libraries/ghc-internal/src/GHC/Internal/RTS/Flags.hsc - libraries/ghc-internal/src/GHC/Internal/TypeNats.hs - libraries/ghc-internal/src/GHC/Internal/Types.hs - libraries/stm - linters/lint-codes/LintCodes/Static.hs - 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+ testsuite/tests/warnings/should_compile/T16836a.stderr - + testsuite/tests/warnings/should_compile/T16836b.hs - + testsuite/tests/warnings/should_compile/T16836c.hs - + testsuite/tests/warnings/should_compile/T16836c.stderr - + testsuite/tests/warnings/should_compile/T16836d.hs - + testsuite/tests/warnings/should_compile/T16836d.stderr - testsuite/tests/warnings/should_compile/all.T - + testsuite/tests/warnings/should_fail/WExpectedNoArgError.stderr - testsuite/tests/warnings/should_fail/all.T - utils/check-exact/ExactPrint.hs - utils/check-exact/Utils.hs - utils/deriveConstants/Main.hs - utils/ghc-toolchain/src/GHC/Toolchain/Program.hs - utils/haddock/haddock-api/src/Haddock/Backends/Hoogle.hs - utils/haddock/haddock-api/src/Haddock/Convert.hs - utils/haddock/haddock-api/src/Haddock/GhcUtils.hs - utils/haddock/haddock-api/src/Haddock/Interface/Rename.hs - utils/haddock/haddock-api/src/Haddock/Types.hs - utils/hsc2hs - utils/jsffi/dyld.mjs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/6f2577441a020aa944c094f4d926dc… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/6f2577441a020aa944c094f4d926dc… You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc] Pushed new branch wip/apk/rts-flag-fixes
by Andreas Klebinger (＠AndreasK) 21 Sep '26

21 Sep '26

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

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[Git][ghc/ghc][wip/andrea/gbc-backport] 2 commits: Backport of bytecode objects and bytecode libraries
by Andrea Vezzosi (＠trac-Saizan) 21 Sep '26

21 Sep '26

Andrea Vezzosi pushed to branch wip/andrea/gbc-backport at Glasgow Haskell Compiler / GHC Commits: fc171c5e by Andrea Vezzosi at 2026-09-21T10:10:29+02:00 Backport of bytecode objects and bytecode libraries Cherry-picked these commits and their dependencies: - 8f9ae3397d Load bytecode libraries to satisfy package dependencies - e36a5fcbea Add support for building bytecode libraries - 6bd8155c99 Add support for generating bytecode objects ------------------------- Metric Increase: MultiComponentModules MultiLayerModules MultiComponentModulesRecomp MultiLayerModulesRecomp MultiLayerModulesTH_Make MultiLayerModulesTH_OneShot TcPlugin_RewritePerf ------------------------- Full list of cherry-picked commits: rts/Interpreter: Factor out ctoi tuple info tables into data (cherry picked from commit d2b89603425b6d08df199deb7b84cfdbd711869a) compiler: only use `Name` instead of `Id` in `SptEntry` (cherry picked from commit 39b2e3823da3ab168aa2b7365f0f27e01b1ecd0e) Generalise thNameToGhcName by adding HasHscEnv (cherry picked from commit eb2ab1e2cadde93c330330ca7fdc64b31cd61473) Refactor ForAllCo (cherry picked from commit 94b62aa7e7b40b53442161a0c4f380955fda2f14) ghci: add :shell command (cherry picked from commit 06d2562362768051e4901878248cbad103e66e92) testsuite: remove legacy :shell trick (cherry picked from commit 186054f7e7a190ee175a6e93c6cfb63b8a67baca) docs: document :shell in ghci (cherry picked from commit 0a3a4aa30894820731e646e2788e9819b10a7d07) compiler/ghci: replace the LoadDLL message with LoadDLLs (cherry picked from commit a4d664c78642438f0f178ffa243e2ffdbdf20397) driver: separate downsweep/upsweep phase in loadPackages' (cherry picked from commit c7fc4baeddcfad500126b2e91ce94d2b9391560d) driver: emit single LoadDLLs message to load multiple DLLs (cherry picked from commit ab180104b61a930e8a1e906f013c151669ce6fff) driver: Load bytecode static pointer entries during linking (cherry picked from commit e9445c013fbccf9318739ca3d095a3e0a2e1be8a) loader: Unify loadDecls and loadModuleLinkables functions (cherry picked from commit da9633a9009a08132b974b0407c4057cae3577f7) testsuite: Use ghci_ways to set ways in PackedDataCon/UnboxedTuples/UnliftedDataTypeInterp tests (cherry picked from commit 1275d3607299734228adbbc47bfb69bf8800279f) Rename interpreterBackend to bytecodeBackend (cherry picked from commit c06b534bbd6dbb570b760f2e82b3e375d3956bcf) Improvements to 'mayLookIdentical' (cherry picked from commit 2b8baada761b13199b99268f243bebd009e6e1b5) Store SDoc context in SourceError (cherry picked from commit 129ce32d3a4f2601f5c2d1bbaeeb2fbaf8dc9ef9) Add support for generating bytecode objects (cherry picked from commit 6bd8155c991cfce7cca594bc63ba8f6ca6751667) rts: Eliminate uses of implicit constant arrays (cherry picked from commit 0c00c9c3b4e9b8515d4839f2c1d7d771781dc6f4) rts: use computed goto for instruction dispatch in the bytecode interpreter (cherry picked from commit 39567e85fa514c0c4dfeaf8faa586a47dd3e11ca) Remove the `CoreBindings` constructor from `LinkablePart` (cherry picked from commit b253013ebeea5273a1cc7bb0082ed952456af906) driver: Properly handle errors during LinkNode steps (cherry picked from commit 6c91582f915f80daff774db7738094bda6ab3b44) Build external interpreter program on demand (#24731) (cherry picked from commit 55eab80d337e47decacbe979c29a1b7b47d0a872) Use 'OsPath' in getModificationTimeIfExists (cherry picked from commit ef0dc33b2034fd91e11950751264e8b2e9f03fc4) Use OsPath in PkgDbRef and UnitDatabase, not FilePath (cherry picked from commit fa3bd0a67eea13701d1b50053636f9645e999308) Add support for building bytecode libraries (cherry picked from commit e36a5fcbeaa33abb17707173c9d1e81730f85008) Load bytecode libraries to satisfy package dependencies (cherry picked from commit 8f9ae3397dbcbb4b0bd7a574ffc6b1fbaa137b6c) - - - - - 19a57791 by Andrea Vezzosi at 2026-09-21T10:11:16+02:00 Backport of bytecode objects relevant bugfixes. Cherry-pick of these commits and what they depend on - 28f07d702a Make HPC work with bytecode interpreter - d95a19366f Add constants for bytecode in-memory buffer size - 9b64ad3a45 determinism: Use a deterministic renaming when writing bytecode files ------------------------- Metric Decrease: interpreter_steplocal Metric Increase: MultiLayerModulesTH_OneShot ------------------------- All cherry-picked commits, oldest first: driver: Hide source paths at verbosity level 1 by default (cherry picked from commit aa9c5e2ca0d42f7361fc465d79f5beb056987a41) determinism: Use a deterministic renaming when writing bytecode files Fixes #26499 (cherry picked from commit 9b64ad3a458bf4e4165f125059e4bc3d518c5834) compiler: implement string interning logic for BCONPtrFS (cherry picked from commit d054b4676298ea2189cd48fcf175676b97f559e7) compiler: use `Binary` instance of `BCOByteArray` for bytecode objects (cherry picked from commit fdf828aef8c78ae23ad058ed4696910b6beba232) Support arbitrary size unboxed tuples in bytecode (cherry picked from commit a85bd503a480cfa31f5afa09eb38f56c85c237de) Add specialized frames for small tuples (cherry picked from commit e2209031734770a51f04883e5b538b562449cba1) Extract Binary instances to `GHC.ByteCode.Binary` (cherry picked from commit acffb1b1da1a59dbded9ec2dcb65e495aee31f40) Add `seqNonEmpty` for evaluating `NonEmpty a` (cherry picked from commit e2ea8e25c5128afa8191669c751942348ab3043b) Record `LinkableUsage` instead of `Linkable` in `LoaderState` (cherry picked from commit 048b00b7c231dec199a4441caac279f3bbcd75f4) bytecode: Add magic header/version to bytecode files (cherry picked from commit 5cbc2c823fb0710c37f6e9144382dd59e0353782) Add constants for bytecode in-memory buffer size (cherry picked from commit d95a19366f64e6d866c8df0b1ab917884cc015dc) testsuite: filter stderr for static001 on darwin (cherry picked from commit b822c30aa6c0bf008c06c5bd4ee86313c40f652d) ghci: use ShortByteString for LookupSymbol/LookupSymbolInDLL/LookupClosure messages (cherry picked from commit 8dd6f453348e467686bd222551c89ecc466d36f0) ghci: use ShortByteString for MkCostCentres message (cherry picked from commit 371ef200bcb2664c4511daca75f72a52c1473950) Expose startupHpc as an rts symbol (cherry picked from commit f3485446d8c90aa39ee633606b488253ae23a255) Make HPC work with bytecode interpreter (cherry picked from commit 28f07d702a1b47230122df22e84b60fda49897c5) - - - - - 388 changed files: - + changelog.d/bytecode-interpreter-hpc-support - compiler/GHC.hs - compiler/GHC/Builtin/PrimOps.hs - compiler/GHC/ByteCode/Asm.hs - + compiler/GHC/ByteCode/Binary.hs - compiler/GHC/ByteCode/Breakpoints.hs - compiler/GHC/ByteCode/Instr.hs - compiler/GHC/ByteCode/Linker.hs - + compiler/GHC/ByteCode/Recomp/Binary.hs - + compiler/GHC/ByteCode/Serialize.hs - compiler/GHC/ByteCode/Types.hs - compiler/GHC/Core/Coercion.hs - compiler/GHC/Core/Coercion.hs-boot - compiler/GHC/Core/Coercion/Opt.hs - compiler/GHC/Core/Lint.hs - compiler/GHC/Core/Multiplicity.hs - compiler/GHC/Core/Opt/Arity.hs - compiler/GHC/Core/Opt/Monad.hs - compiler/GHC/Core/Reduction.hs - compiler/GHC/Core/TyCo/Compare.hs - compiler/GHC/Core/TyCo/FVs.hs - compiler/GHC/Core/TyCo/Ppr.hs - compiler/GHC/Core/TyCo/Rep.hs - compiler/GHC/Core/TyCo/Subst.hs - compiler/GHC/Core/TyCo/Tidy.hs - compiler/GHC/Core/Type.hs - compiler/GHC/Core/Unify.hs - compiler/GHC/CoreToIface.hs - compiler/GHC/Data/FlatBag.hs - 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View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/b3fda9baa7821003ef508e5926e5f8… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/b3fda9baa7821003ef508e5926e5f8… You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc][wip/az/exactprint-annotation-rationalisation] 71 commits: FastString: Drop mkFastStringWith's constructor callback
by Alan Zimmerman (＠alanz) 21 Sep '26

21 Sep '26

Alan Zimmerman pushed to branch wip/az/exactprint-annotation-rationalisation at Glasgow Haskell Compiler / GHC Commits: 7a108e43 by Simon Jakobi at 2026-09-12T18:35:59-04:00 FastString: Drop mkFastStringWith's constructor callback All three callers passed the same callback, a partial application of mkNewFastStringShortByteString to the string being interned. That partial application is allocated as a closure before the table lookup, on the common hit path too, although the callback is needed only after a miss. Drop the parameter and call mkNewFastStringShortByteString directly after a miss. Since nothing is passed "with" anymore, rename the function to internSB. Suggested by Simon PJ in #27528: https://gitlab.haskell.org/ghc/ghc/-/work_items/27528#note_687031 Assisted-by: Claude Fable 5 - - - - - 82c73b22 by Alan Zimmerman at 2026-09-12T18:36:38-04:00 EPA: More targeted HsDo exact print annotation HsDo is multi-purpose, as encoded in its HsDoFlavour field. Some of these are in a layout context (DoExpr, MDoExpr), others are not (ListComp, MonadComp). We are moving towards using AnnList only in layout contexts, so we switch the HsDo TTG annotation from holding an AnnList for this, to holding Either (EpToken "[", EpToken "]") AnnList This also allows us to trim down AnnListBrackets to only have braces or None, thereby opening the door for unification with the existing layout context data type EpLayout. - - - - - 749d2448 by Luite Stegeman at 2026-09-15T14:07:01-04:00 rts: handle large CONSTR closures in compacting GC The function update_fwd_large in the compacting GC could run into an unexpected object with the following error: internal error: update_fwd_large: unknown/strange object 1 Closure type 1 is CONSTR. This patch adds cases for CONSTR and CONSTR_NOCAF. This is the same problem as #27434 (large AP closures, fixed by cca0d58963), which missed this case. Fixes #27649 - - - - - 177d6155 by Luite Stegeman at 2026-09-15T14:07:02-04:00 testsuite: fix T27434 test with compacting GC Ensure that the interpreter is actually run with the compacting GC - - - - - 5796aa63 by Luite Stegeman at 2026-09-15T14:07:49-04:00 rts: initialise the stack frame header for mask_frame and apply_mask_frame We must leave the stack in consistent state before jumping to mask_frame or apply_mask_frame because they may result. Failing to do so could lead to a crash if there were waiting exceptions. Fixes #27651 - - - - - 2486cc92 by Simon Peyton Jones at 2026-09-15T14:08:36-04:00 Re-introduce the "weird SpecDict" case In this commit commit f80375dd4945350a1d784e436975b48b9c736eaf Author: Simon Peyton Jones <simon.peytonjones(a)gmail.com> Date: Sun Jun 29 15:26:58 2025 +0100 Refactor of Specialise.hs I removed a test for a dictionary with unbound type variables. This turned out to be wrong; see #27629. So this MR re-introduces it. - - - - - 8e09a46f by Duncan Coutts at 2026-09-15T20:11:35-04:00 Refactor (and rename) removeFromQueues, to simplify I/O managers Rename it to unblockAndAppendToRunQueue which better reflects what it is intended to do. The post-condition for unblockAndAppendToRunQueue is that the TSO is on the run queue or it is in the process of migrating to another cap. Previously it achieved that by always directly adding the TSO to the run queue itself. But this actually made things more complicated for the I/O managers, because it meant they needed a separate code path for notifying for cancellation compared to notifying for completion. The general notification code would always add the TSO to the run queue itself. So the improvement is to allow different cases in unblockAndAppendToRunQueue to achieve the same outcome in different ways: either directly adding to the run queue or calling helper functions that do so themselves. This then allows the new I/O managers to share code between the sync and async cancellation, and to reuse their notifyIOCompletion helpers for cancellation. This avoids a source of bugs where the completion path may be updated but the cancellation path may be forgotten, or similarly in future for sync/async operations. Update all the existing in-RTS I/O managers, and the posix timeout code. - - - - - d668782c by Duncan Coutts at 2026-09-15T20:11:35-04:00 Document that awaitCompletedTimeoutsOrIO expects an empty run queue This was true before but implicit and not relied on much. It's better to be explicit, and allow things to depend on it. - - - - - 11d938bb by Duncan Coutts at 2026-09-15T20:11:35-04:00 Store the I/O opcode and fd in the StgAsyncIOOp This will be useful in several I/O managers and it is handy for logging and debugging. It also doesn't increase the size of the StgAsyncIOOp structure. There was enough spare padding space already. Update the poll I/O manager to set the new fields. Add a helper function to convert the enum IOReadOrWrite into the enum IOOpCode. Also change IOReadOrWrite to be an enum without a typedef, for consistency with other enumerations in IOManager.h - - - - - bfa87882 by Duncan Coutts at 2026-09-15T20:11:36-04:00 Add a new I/O manager based on select() Yes, this is the second such I/O manager, but it is a modern re-implementation based on the new in-RTS I/O manager infrastructure. So it is cleaner and faster than the old select I/O manager. Why do we need another I/O manager based on select? Why isn't the poll() one good enough as a baseline portable unix I/O manager? Because macOS. Apple Inc. is why we cannot have nice things. The man page for poll on macOS documents the fact that it does not work. At least, it does not work for all files. Specifically, it does not work for device files. Whereas macOS select() does work for device files. Aaaaarg! We _do_ want to deprecate and remove the old select I/O manager, but due to macOS we cannot do that until we have a replacement. This is that replacement. Until of course a nice new k-queue I/O manager arrives, which could become the new default for macOS and FreeBSD. Interestingly, this select I/O manager is actually faster than the poll one, on Linix, in some circumstances: specifically when many Haskell threads are waiting on the same fd. The poll I/O manager does O(n) work for n threads waiting on I/O, whereas the select one does O(fds) work for the number of fds that threads are waiting on. Usually this is 1:1, so it's not noticable, but one can concoct extreme benchmarks to show the difference. - - - - - 8e9de15a by Duncan Coutts at 2026-09-15T20:11:36-04:00 Minor updates in the poll I/O manager to keep in sync with select This keeps it in sync with select one. The changes are based on code review while implementing the new select I/O manager. The two I/O managers are so similar in structure that it makes sense to try to minimise the diff between them. This should aid understanding, and fixes to both in future. - - - - - 222668bb by Duncan Coutts at 2026-09-15T20:11:36-04:00 Document the new select I/O manager in the user guide in the RTS section about I/O managers. And add a changelog entry. - - - - - 0f48735b by Cheng Shao at 2026-09-15T20:12:23-04:00 Revert "wasm: workaround WebKit bug in dyld" This reverts commit c9b8465c2c338176fcab9d197e9d31f4aee11f68. The underlying webkit bug has been fixed in https://commits.webkit.org/314219@main. Closes #27564. - - - - - 809294f1 by Luite Stegeman at 2026-09-15T20:13:08-04:00 rts: make stg_threadLabelzh return a valid pointer for unlabeled threads. This fixes a segfault in the GC caused by stg_threadLabelzh returning a 0 pointer in a GC pointer field. stg_threadLabelzh returns a tuple of type (# Int#, ByteArray# #). If a thread has no label, the second field is unused. We must still return a valid heap object pointer. Instead of returning 0, we now return stg_DEAD_SLOT_closure. fixes #27618 - - - - - e2d57026 by Luite Stegeman at 2026-09-15T20:13:54-04:00 JS: fix selector thunk handling fix a bug where entering a selector thunk could lead to a crash if the selected field was still a thunk. fixes #27788 - - - - - 1b4a622f by sheaf at 2026-09-17T02:39:13-04:00 Improvements to type/data family handling This commit makes several improvements to the treatment of type and data families in GHC: - We consistently use "type family" instead of "type synonym family" to avoid a confusion with type synonyms. For example: - OpenSynFamilyTyCon ==> OpenTypeFamilyTyCon - ClosedSynFamilyTyCon => ClosedTypeFamilyTyCon - Various functions that were specific to data families have been renamed to make this clear. For example: - tyConFamInst_maybe ==> tyConDataFamInst_maybe - isFamInstTyCon ==> isDataFamInstTyCon - 'FamTyConFlav' has been refactored so that all closed type families share a single 'ClosedTypeFamilyTyCon' constructor. The corresponding 'IfaceFamTyConFlav' type was updated similarly. This is then used to tidy up the implementation of GHC.Core.FamInstEnv.reduceTyFamApp_maybe. - - - - - c5aa9098 by sheaf at 2026-09-17T02:39:13-04:00 Small refactor of lookupFamInstEnv This commit reworks the code for looking up family instances in GHC.Core.FamInstEnv, reducing duplication a little bit. No change in behaviour. - - - - - a3ad4588 by sheaf at 2026-09-17T02:39:14-04:00 Use a type family for boxing unboxed types This commit overhauls the way in which unboxed types are boxed, as per the updated Note [Boxing constructors] in GHC.Builtin.WiredIn.Types.Box. The main change is to allow boxing to be parametrised by representation, e.g. making 'Box ty' a valid type. We achieve this by implementing 'Box' using a closed type family: newtype Box (a :: TYPE r) = Box (BoxTF r) type BoxTF :: RuntimeRep -> Type type family BoxTF r where BoxTF IntRep = BoxInt BoxTF Int8Rep = BoxInt8 BoxTF WordRep = BoxWord BoxTF LiftedRep = Any @Type BoxTF (TupleRep [r1, r2]) = (BoxTF r1, BoxTF r2) ... BoxTF (SumRep rs) = BoxSum rs This new design solves the following problems: - It allows boxing a type whose 'RuntimeRep' has not yet been determined (e.g. because we only learn the 'RuntimeRep' after constraint solving). That is, 'Box @r a' is a perfectly valid type even if 'r' is an unfilled metavariable. This is a requirement to fix #25065 (in which we need to box a type whose 'RuntimeRep' is only filled in during constraint solving). - It handles boxing of unboxed tuples and unboxed sums, via recursive boxing. See Note [Boxing TupleRep and SumRep] in GHC.Builtin.WiredIn.Types.Box. 'Box', 'BoxTF' and all of the boxing data constructors are defined in a new 'ghc-internal' module, 'GHC.Internal.Box'. This module contains nothing but wired-in declarations, and GHC never loads its interface on account of a wired-in thing (GHC.Builtin.Modules.isWiredInOnlyModule); see Note [Loading instances for wired-in things] in GHC.Iface.Load. The individual boxing data constructors are deliberately left as an internal implementation detail, and not exported. The intended API is via the two new magic 'Id's: box :: forall {r} (a :: TYPE r). a -> Box a unbox :: forall {r} (a :: TYPE r). Box a -> a exported from 'GHC.PrimOps' (in 'ghc-experimental'). The old boxing data types (IntBox, WordBox, FloatBox, DoubleBox, DictBox) are no longer exported from base (CLC proposal #421). We use this new design to consistently desugar: - parallel comprehensions (GHC.HsToCore.ListComp.{deListComp,dsMcStmt}) - then/group/using statements (GHC.HsToCore.ListComp.{dsTransStmt,dsMcStmt}) - recursive do blocks (mdo/rec) (GHC.HsToCore.Expr.dsDo) - arrows (GHC.HsToCore.Arrows) by consistently using 'box'/'unbox' to deal with unboxed types being put into big tuples. We also adapt 'GHC.Tc.Gen.Match.{tcMcStmt,tcDoStmt}' to create fresh /representation-polymorphic/ type variables for the binders that we are going to put into a big tuple (previously, GHC only allowed lifted types in that position). These desugaring of box and unbox is explained in Note [Desugaring box & unbox] in GHC.Core.Make.Box. Roughly speaking, the desugaring looks like: box @r @ty e ==> K e unbox @r @ty e ==> case e of K x -> x where 'K' is the boxing data constructor at RuntimeRep 'r'. It's slightly more complicated than that in practice: we first need to insert a cast (see Note [The canonical type of a RuntimeRep]) using the new 'CanonicalProv' 'UnivCoProvenance', and unboxed tuples/sums need recursive logic explained in Note [box/unbox for unboxed tuples and sums], including a specific 'BoxSum' datatypes for unboxed sum (which also needed a wired-in type-level list indexing type family (!!)). The desugaring happens in two ways: - Occurrences of 'box'/'unbox' emitted by the typechecker are eliminated in the 'ds_app_var' case of GHC.HsToCore.Expr. - Other code that needs to box/unbox emits the appropriate code inline. This includes the big tuple machinery of GHC.Core.Make used by the desugarer (GHC.HsToCore.{Utils,Binds,Arrows,ListComp}) as well as the float-out pass (GHC.Core.Opt.SetLevels). Core Lint checks that no occurrence of 'box'/'unbox' survives desugaring. On the way, we overhaul the litany of big tuple functions by introducing data BigTupleLayout = BoxedElements | BareElements to distinguish the two kinds of "big tuples" that GHC routinely deals with; for example 'mkBigCoreVarTupSolo' becomes 'mkBigCoreVarTup BareElements'. All of this code is moved to the new module GHC.Core.Make.BigTuple. Fixes #20864 #22336 #22473 #25065 #27331 ------------------------- Metric Decrease: T9872a ------------------------- - - - - - 4cf7628a by Evgeny Malyshev at 2026-09-17T02:39:56-04:00 Fix the CompactionFailed documentation link to compact The old Haddock reference links into base instead of ghc-compact. Use an explicit URL because ghc-compact depends on base, not vice versa. Fixes #27558 Assisted-By: OpenAI Codex - - - - - 098bba70 by Facundo Domínguez at 2026-09-17T14:57:41-04:00 Remove the call to hoistFlag from processCmdLineP This call was undesirable because it was causing a reconstruction of the list of flag processors. Even relying on list fusion would not be sufficient because we want to replace the list with a data structure with faster lookups to address #25763. The removal is done in two moves: * We move CmdLineP to CmdLine.hs * Then we move the effect of hoisting to processArgs via a new function hoistEwM - - - - - e01799c7 by Facundo Domínguez at 2026-09-17T14:57:42-04:00 Do not create duplicate flag processors for the -W flag This makes simpler implementing the command line parser with a trie map holding flag processors. If we were to allow duplicate flag processors for any flag, the trie map would need to be a multimap. - - - - - 3875b257 by Facundo Domínguez at 2026-09-17T14:57:42-04:00 Replace the list of flag processors with a trie map in `processArgs` Previously `GHC.Driver.CmdLine.findArg` was called for each command-line argument, doing a linear search on the list of flag processors each time. This was somewhat costly as the list of flag processor has near 2000 elements. A lookup with a trie map is faster in general, but the speed up is only noticeable when calling `GHC.Driver.CmdLine.processArgs` sufficient times, so the amount of lookups piles up. This could happen in large projects with many units each having many dependencies. If only a module needs to be recompiled, the user still needs to wait for all of the flag parsing to complete. The benchmark at testsuite/tests/perf/compiler/cmdline-parser shows a 10x speed up when using the trie. The trie map is implemented in `GHC.Data.StringTrie`. The design is explained in Note [Processing command line argument fast] in GHC.Driver.Session. The commit also: * adds two property-based tests for trie map operations, * adds a benchmark of the command line parser, and * renames the predicate `arg_ok` to `valid_flag_suffix` to decide what flag processor should be used when there are multiple matching prefixes on a flag. Fixes #25763. - - - - - 5236634a by Andreas Klebinger at 2026-09-17T14:58:24-04:00 Compile Word64{Map,Set} with -O2 always. This is the hottest code and even if we build GHC with -O0 otherwise -O2 pays off for these modules. Fixes #27814. - - - - - 7c93b793 by Alan Zimmerman at 2026-09-20T18:28:24+01:00 EPA: Add specific layout field to AnnList Up to now AnnList has effectively served to represent lists of things having layout, regardless of whether they do or not. In Haskell, layout is optional in many places, as there is also an alternative syntax using braces and semi-colons, which is free-form. This commit introduces AnnListLayout, a data structure capturing this distinction. It is deliberately set up similarly to EpLayout, so that these two can be merged in time. - - - - - d268c6d1 by Alan Zimmerman at 2026-09-20T18:28:24+01:00 EPA: Use EpaLocation in EpVirtualBraces reword: EPA Use vocurly as basis for AnnListLayout For the existing cases that populate AnnList. This also shows up AnnList usages that can never capture layout. - - - - - 9e35bd08 by Alan Zimmerman at 2026-09-20T18:28:24+01:00 EPA: Use vocurly as basis for AnnListLayout For the existing cases that populate AnnList. This also shows up AnnList usages that can never capture layout. - - - - - 80b4d2c0 by Alan Zimmerman at 2026-09-20T18:28:24+01:00 EPA: AnnList clean up patch for empty where clause - - - - - 21bac229 by Alan Zimmerman at 2026-09-20T19:14:58+01:00 EPA: Add TTG fields to FamilyInfo This commit is a simple add, with unused extension fields. It lays the groundwork for using them for exact print annotations - - - - - 06e028a0 by Alan Zimmerman at 2026-09-20T20:52:22+01:00 WIP annclassdecl - - - - - f34f809d by Alan Zimmerman at 2026-09-20T20:52:22+01:00 EPA: Update AnnClsInstDecl to contain AnnList It was already separately tracking the '{', '}' and leading ';' values. This aligns it with layout-introducing parser productions ('vocurly'), so the layout processing can be handled uniformly - - - - - ca29596c by Alan Zimmerman at 2026-09-20T20:52:22+01:00 EPA: Tidy up markAnnListA' It takes an action which can modify the AnnList, but this is never used. So remove it. - - - - - 830e610c by Alan Zimmerman at 2026-09-20T20:52:22+01:00 EPA: Use AnnList for GADT declarations - - - - - 4f0b7c93 by Alan Zimmerman at 2026-09-20T20:52:22+01:00 EPA: Use AnnList in AnnClassDecl - - - - - 6503897e by Alan Zimmerman at 2026-09-20T20:52:22+01:00 MOVE EPA: Plan for Fixing AnnList Layout Properly - - - - - 11fdedd2 by Alan Zimmerman at 2026-09-20T20:52:22+01:00 EPA: Make local binds located Use LHsLocalBinds instead of HsLocalBinds This reverses an earlier change, and brings processing of local binds into alignement with the exact printing principle that the LocatedA contents provide the location and extent of the enclosed item, together with any comments or context-specific trailing items like commas or semi colons. The internal TTG extension points only carry exact print annotations related to printing the item within its bounds. This change brings back the problem of EmptyLocalBinds, which by definition cannot have a location. These get a noSrcSpan location, which is ignored in the exact printing process. - - - - - d41e850f by Alan Zimmerman at 2026-09-20T20:52:22+01:00 EPA: Use AnnList in HsMultiIf It introduces layout, capture it - - - - - e0cce294 by Alan Zimmerman at 2026-09-20T20:52:22+01:00 EPA: Use AnnList in DecBrl - - - - - 5adbec51 by Alan Zimmerman at 2026-09-20T20:52:22+01:00 EPA: Replace AnnListLayout / AnnListBrackets with EpLayout - - - - - 8044effc by Alan Zimmerman at 2026-09-20T20:52:22+01:00 WIP: setLayoutBoth inside markAnnListA Current problem is it is a global one-shot, and MG has one too Check: is it needed? if so, honouring EpLayout may be needed - - - - - 2f24f746 by Alan Zimmerman at 2026-09-20T20:52:22+01:00 EPA some tests for layout. WIP - - - - - 9f9024c8 by Alan Zimmerman at 2026-09-20T20:52:22+01:00 Exactprint layout scope plan. Do not commit - - - - - 60d6a0bc by Alan Zimmerman at 2026-09-20T20:52:22+01:00 EPA: tidy up a bit. Combine somewhere else - - - - - 94fcd956 by Alan Zimmerman at 2026-09-20T20:52:22+01:00 EPA: Introduce LayoutFrame stacks in ExactPrint state - - - - - 9b15cb94 by Alan Zimmerman at 2026-09-20T20:52:22+01:00 Align with ghc-exactprint - - - - - d169c6b0 by Alan Zimmerman at 2026-09-20T20:52:22+01:00 EPA: Fix AnnList leading semis when layout When there is layout, anything printed triggers it, including leading semis. Add some test case examples too - - - - - 84453918 by Alan Zimmerman at 2026-09-20T20:52:22+01:00 Exactprint: tidy up layout capturing - - - - - 3c3e124c by Alan Zimmerman at 2026-09-20T20:52:22+01:00 EPA: add makeDelta test for Test20297 The original #20297 related to comment placement for exact printing after running ExactPrint.makeDelta on ParsedSource. Add an additional test that explicitly tests this. - - - - - 7c94b3d7 by Alan Zimmerman at 2026-09-20T20:52:22+01:00 EPA: Make ValBinds LocatedA in HsLocalBindsLR If we have items with an AnnList Annotation, as part of another, which has different content, it must be LocatedA. This is a technical requirement due to the way comment allocation happens during the makeDelta processing. Comments are queued for printing, and as soon as any non-comment is to be printed, the pending comments before that position are printed, and in makeDelta processing these attached as preceding comments to the thing just printed. The means they end up captured inside the layout region of the AnnList item. So for foo = x where -- comment x = 3 the comment ends up as a preceding comment of `x = 3`, inside the layout, and prints as foo = x where -- comment x = 3 - - - - - 9980ef78 by Alan Zimmerman at 2026-09-20T20:52:22+01:00 EPA: Make IPBinds LocatedA - - - - - 3d1272dd by Alan Zimmerman at 2026-09-20T20:52:22+01:00 EPA: Make ClsInstDecl decls LocatedA - - - - - 563b7f23 by Alan Zimmerman at 2026-09-20T20:52:22+01:00 EPA: Make ClassDecls decls LocatedA - - - - - 66d2fdd1 by Alan Zimmerman at 2026-09-20T21:17:59+01:00 EPA: Make ClosedTypeFamily equations Located For FamilyDecl/ClosedTypeFamily - - - - - b5bc2436 by Alan Zimmerman at 2026-09-20T21:17:59+01:00 EPA: Make dd_cons located - - - - - c322ca78 by Alan Zimmerman at 2026-09-20T21:17:59+01:00 EPA: Make HsMultiIf options located - - - - - 5baeed9f by Alan Zimmerman at 2026-09-20T21:17:59+01:00 EPA: Make DecBrl contents LocatedA - - - - - 5a41ea3e by Alan Zimmerman at 2026-09-20T21:17:59+01:00 EPA: Located do statements - - - - - 2e953071 by Alan Zimmerman at 2026-09-20T21:17:59+01:00 EPA: Print RecStmt located - - - - - 60ac0996 by Alan Zimmerman at 2026-09-20T21:17:59+01:00 EPA: HsCmdDo Located - - - - - 0896574b by Alan Zimmerman at 2026-09-20T21:17:59+01:00 Extend Test20297 for additional occurrences - - - - - 5393457c by Alan Zimmerman at 2026-09-20T21:17:59+01:00 EPA: Tweak PatSynBind location for comments - - - - - bc60b188 by Alan Zimmerman at 2026-09-20T21:17:59+01:00 EPA: WIP, add test for where ;; ValBinds - - - - - a4a67438 by Alan Zimmerman at 2026-09-20T21:17:59+01:00 EPA: Make EpVirtualBraces noSpanAnchor if no contents Otherwise the vocurly is emitted at the start of the next item parsed Check: is this needed, or just a check for empty contents? - - - - - be6786fb by Alan Zimmerman at 2026-09-20T21:17:59+01:00 WIP: turn of exactprint debug printing - - - - - 6aff12b6 by Alan Zimmerman at 2026-09-20T21:17:59+01:00 EPA: Remove CanUpdateAnchorOnly - - - - - 57e48af6 by Alan Zimmerman at 2026-09-20T21:17:59+01:00 Plan update DO NOT COMMIT - - - - - a20a6b49 by Alan Zimmerman at 2026-09-20T21:17:59+01:00 EPA: First pass implementation of HsList, for ClassDecls Just as a straight list replacement to start with, no payload. This shows the scope and invasiveness of the initial change - - - - - 6cc06851 by Alan Zimmerman at 2026-09-20T21:17:59+01:00 EPA: HsList attempt WIP - - - - - 2eead5fc by Alan Zimmerman at 2026-09-20T21:17:59+01:00 Enable ppr test for Haddock1. It currently fails - - - - - 74638b2e by Alan Zimmerman at 2026-09-20T21:17:59+01:00 WIP on removing NoEpAnn. Likely abandon - - - - - 6ee02071 by Alan Zimmerman at 2026-09-20T21:17:59+01:00 EPA: Add an overview doc for exact printing - - - - - 816483fb by Simon Peyton Jones at 2026-09-20T21:17:59+01:00 Added an intro section - - - - - 263 changed files: - + ANNLIST-LAYOUT-PLAN.md - + ExactPrint.md - + LAYOUT-SCOPE-PLAN.md - + changelog.d/25763-cmdline-opt - + changelog.d/T27629 - + changelog.d/T27788-js-selector - + changelog.d/boxing-family - + changelog.d/clc-421 - + changelog.d/fix-compacting-gc-constr-27649 - + changelog.d/fix-control0-mask-trampoline - + changelog.d/fix-threadlabel-segfault-27618 - + changelog.d/select-io-manager - compiler/GHC/Builtin.hs - compiler/GHC/Builtin/KnownKeys.hs - compiler/GHC/Builtin/Modules.hs - compiler/GHC/Builtin/Uniques.hs - compiler/GHC/Builtin/WiredIn/Ids.hs - compiler/GHC/Builtin/WiredIn/Prim.hs - compiler/GHC/Builtin/WiredIn/TypeLits.hs - compiler/GHC/Builtin/WiredIn/Types.hs - + compiler/GHC/Builtin/WiredIn/Types/Box.hs - compiler/GHC/Core/Coercion.hs - compiler/GHC/Core/Coercion/Axiom.hs - compiler/GHC/Core/DataCon.hs - compiler/GHC/Core/FamInstEnv.hs - compiler/GHC/Core/Lint.hs - compiler/GHC/Core/Make.hs - + compiler/GHC/Core/Make/BigTuple.hs - + compiler/GHC/Core/Make/Box.hs - compiler/GHC/Core/Opt/SetLevels.hs - compiler/GHC/Core/Opt/Specialise.hs - compiler/GHC/Core/TyCo/Ppr.hs - compiler/GHC/Core/TyCo/Rep.hs - compiler/GHC/Core/TyCon.hs - compiler/GHC/Core/Type.hs - compiler/GHC/CoreToStg.hs - compiler/GHC/CoreToStg/AddImplicitBinds.hs - compiler/GHC/Data/FastString.hs - + compiler/GHC/Data/StringTrie.hs - compiler/GHC/Data/Word64Map/Internal.hs - compiler/GHC/Data/Word64Map/Strict/Internal.hs - compiler/GHC/Data/Word64Set/Internal.hs - compiler/GHC/Driver/Backpack.hs - compiler/GHC/Driver/CmdLine.hs - compiler/GHC/Driver/Main/Compile.hs - compiler/GHC/Driver/Main/Interactive.hs - compiler/GHC/Driver/Main/Passes.hs - compiler/GHC/Driver/Session.hs - compiler/GHC/Hs.hs - compiler/GHC/Hs/Binds.hs - compiler/GHC/Hs/Decls.hs - compiler/GHC/Hs/DocString.hs - compiler/GHC/Hs/Dump.hs - compiler/GHC/Hs/Expr.hs - compiler/GHC/Hs/ImpExp.hs - compiler/GHC/Hs/Instances.hs - compiler/GHC/Hs/Stats.hs - compiler/GHC/Hs/Utils.hs - compiler/GHC/HsToCore/Arrows.hs - compiler/GHC/HsToCore/Binds.hs - compiler/GHC/HsToCore/Docs.hs - compiler/GHC/HsToCore/Expr.hs - compiler/GHC/HsToCore/Expr.hs-boot - compiler/GHC/HsToCore/ListComp.hs - compiler/GHC/HsToCore/Match.hs - compiler/GHC/HsToCore/Pmc/Desugar.hs - compiler/GHC/HsToCore/Quote.hs - compiler/GHC/HsToCore/Ticks.hs - compiler/GHC/HsToCore/Utils.hs - compiler/GHC/Iface/Decl.hs - compiler/GHC/Iface/Ext/Ast.hs - compiler/GHC/Iface/Load.hs - compiler/GHC/Iface/Rename.hs - compiler/GHC/Iface/Syntax.hs - compiler/GHC/Iface/Tidy.hs - compiler/GHC/IfaceToCore.hs - compiler/GHC/Parser.y - compiler/GHC/Parser/Annotation.hs - compiler/GHC/Parser/PostProcess.hs - compiler/GHC/Parser/PostProcess/Haddock.hs - compiler/GHC/Rename/Bind.hs - compiler/GHC/Rename/Expr.hs - compiler/GHC/Rename/Module.hs - compiler/GHC/Rename/Names.hs - compiler/GHC/Rename/Splice.hs - compiler/GHC/Rename/Utils.hs - compiler/GHC/Runtime/Eval.hs - compiler/GHC/Stg/Lint.hs - compiler/GHC/StgToJS/Apply.hs - compiler/GHC/StgToJS/CodeGen.hs - compiler/GHC/StgToJS/Symbols.hs - compiler/GHC/Tc/Deriv.hs - compiler/GHC/Tc/Deriv/Functor.hs - compiler/GHC/Tc/Deriv/Generate.hs - compiler/GHC/Tc/Deriv/Generics.hs - compiler/GHC/Tc/Gen/Arrow.hs - compiler/GHC/Tc/Gen/Bind.hs - compiler/GHC/Tc/Gen/Expr.hs - compiler/GHC/Tc/Gen/HsType.hs - compiler/GHC/Tc/Gen/Match.hs - compiler/GHC/Tc/Gen/Pat.hs - compiler/GHC/Tc/Gen/Splice.hs - compiler/GHC/Tc/Instance/Family.hs - compiler/GHC/Tc/Instance/Typeable.hs - compiler/GHC/Tc/Module.hs - compiler/GHC/Tc/Solver/Default.hs - compiler/GHC/Tc/Solver/FunDeps.hs - compiler/GHC/Tc/TyCl.hs - compiler/GHC/Tc/TyCl/Instance.hs - compiler/GHC/Tc/TyCl/PatSyn.hs - compiler/GHC/Tc/Types/Origin.hs - compiler/GHC/Tc/Utils/Backpack.hs - compiler/GHC/Tc/Utils/Env.hs - compiler/GHC/Tc/Zonk/Type.hs - compiler/GHC/ThToHs.hs - compiler/GHC/Types/CompleteMatch.hs - compiler/GHC/Types/Id.hs - compiler/GHC/Types/Id/Info.hs - compiler/GHC/Types/Id/Make.hs - compiler/GHC/Types/TyThing.hs - compiler/GHC/Types/TyThing/Ppr.hs - compiler/GHC/Types/Unique.hs - compiler/Language/Haskell/Syntax.hs - compiler/Language/Haskell/Syntax/Basic.hs - compiler/Language/Haskell/Syntax/Binds.hs - compiler/Language/Haskell/Syntax/Decls.hs - compiler/Language/Haskell/Syntax/Expr.hs - compiler/Language/Haskell/Syntax/Extension.hs - compiler/ghc.cabal.in - docs/users_guide/runtime_control.rst - ghc/GHC/Driver/Session/Mode.hs - ghc/GHCi/UI.hs - libraries/base/src/GHC/Base.hs - libraries/base/src/GHC/Exts.hs - libraries/base/src/GHC/RTS/Flags.hs - libraries/ghc-internal/ghc-internal.cabal.in - libraries/ghc-internal/include/RtsIfaceSymbols.h - + libraries/ghc-internal/src/GHC/Internal/Box.hs - libraries/ghc-internal/src/GHC/Internal/Exts.hs - libraries/ghc-internal/src/GHC/Internal/IO/Exception.hs - libraries/ghc-internal/src/GHC/Internal/RTS/Flags.hsc - libraries/ghc-internal/src/GHC/Internal/TypeNats.hs - libraries/ghc-internal/src/GHC/Internal/Types.hs - linters/lint-codes/LintCodes/Static.hs - rts/ContinuationOps.cmm - rts/IOManager.c - rts/IOManager.h - rts/IOManagerInternals.h - rts/Prelude.h - rts/PrimOps.cmm - rts/RaiseAsync.c - rts/StgMiscClosures.cmm - rts/configure.ac - rts/include/rts/Flags.h - rts/include/rts/RtsToHsIface.h - rts/include/rts/storage/Closures.h - rts/include/stg/MiscClosures.h - rts/posix/Poll.c - rts/posix/Poll.h - + rts/posix/SelectBis.c - + rts/posix/SelectBis.h - rts/posix/Timeout.c - rts/posix/Timeout.h - rts/rts.cabal - rts/sm/Compact.c - rts/sm/Evac.c - testsuite/tests/MiniQuickCheck.hs - testsuite/tests/arrows/should_run/all.T - + testsuite/tests/arrows/should_run/arrowrun005.hs - + testsuite/tests/arrows/should_run/arrowrun005.stdout - testsuite/tests/count-deps/CountDepsParser.stdout - + testsuite/tests/deSugar/should_compile/T25065a.hs - testsuite/tests/deSugar/should_compile/all.T - + testsuite/tests/deSugar/should_run/T20864.hs - + testsuite/tests/deSugar/should_run/T20864.stdout - 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testsuite/tests/printer/all.T - + testsuite/tests/rts/T27618.hs - + testsuite/tests/rts/T27618.stdout - + testsuite/tests/rts/T27649.hs - + testsuite/tests/rts/T27649.stdout - testsuite/tests/rts/all.T - + testsuite/tests/rts/continuations/T27651.hs - + testsuite/tests/rts/continuations/T27651.stdout - testsuite/tests/rts/continuations/all.T - testsuite/tests/simplCore/should_compile/Makefile - + testsuite/tests/simplCore/should_compile/T27629.hs - + testsuite/tests/simplCore/should_compile/T27629.stderr - + testsuite/tests/simplCore/should_compile/T27629Plugin.hs - testsuite/tests/simplCore/should_compile/all.T - + testsuite/tests/warnings/should_fail/WExpectedNoArgError.stderr - testsuite/tests/warnings/should_fail/all.T - utils/check-exact/ExactPrint.hs - utils/check-exact/Main.hs - utils/check-exact/Parsers.hs - utils/check-exact/Transform.hs - utils/check-exact/Utils.hs - utils/haddock/haddock-api/src/Haddock/Backends/Hoogle.hs - utils/haddock/haddock-api/src/Haddock/Backends/LaTeX.hs - utils/haddock/haddock-api/src/Haddock/Backends/Xhtml/Decl.hs - utils/haddock/haddock-api/src/Haddock/Convert.hs - utils/haddock/haddock-api/src/Haddock/GhcUtils.hs - utils/haddock/haddock-api/src/Haddock/Interface/Create.hs - utils/haddock/haddock-api/src/Haddock/Interface/Rename.hs - utils/haddock/haddock-api/src/Haddock/Types.hs - utils/jsffi/dyld.mjs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/fef901093d64de30368eb02fbc2061… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/fef901093d64de30368eb02fbc2061… You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc] Pushed new branch wip/az/epa-tidy-locatedxxx-25
by Alan Zimmerman (＠alanz) 21 Sep '26

21 Sep '26

Alan Zimmerman pushed new branch wip/az/epa-tidy-locatedxxx-25 at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/az/epa-tidy-locatedxxx-25 You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc][wip/rafl/hpc-instances] 44 commits: Reorder cmm decls in HeapStackCheck for a better logical grouping
by Florian Ragwitz (＠rafl) 21 Sep '26

21 Sep '26

Florian Ragwitz pushed to branch wip/rafl/hpc-instances at Glasgow Haskell Compiler / GHC Commits: 430967ab by Duncan Coutts at 2026-09-09T11:07:01+01:00 Reorder cmm decls in HeapStackCheck for a better logical grouping And put more section headers in to deliniate the groups. We're about to add more here, so better to organise it first. - - - - - 344080fd by Duncan Coutts at 2026-09-09T11:07:01+01:00 Add raisePrimIOException and add it to RTS<->ghc-internal API The raisePrimIOException is a new helper function that I/O primops will use to help them report I/O errors. This is implemented in Haskell (since that's a lot easier), but has a calling convention that is easy(ish) to use from Cmm in the I/O primops. So we add it to the RTS API struct, and since we'll use it from Cmm we also need a field accessor macro for cmm (in deriveConstants). See the Note about how we cannot have nice things due to async exceptions and thunks preventing us from using catch. - - - - - cfdb3399 by Duncan Coutts at 2026-09-09T11:07:01+01:00 Add new blocking functions for I/O primops See the Note [Thread blocking for new I/O primops], and the Note [Calling convention for raisePrimIOException]. The point is, it will allow us to report synchronous exceptions from I/O primops, and do so much more flexibly. Previously the I/O managers could only report async exceptions and only nullary exceptions. This was OK historically, but no good as we add more I/O managers and expand the range of I/O operations we support. - - - - - f09c09d8 by Duncan Coutts at 2026-09-09T11:07:01+01:00 Change the encoding of results from the I/O manager to I/O primops Previously we just had async continue or heap overflow. We now extend what we can report with synchronous success, and synchronous failure with an errno. See Note [Encoding of result of I/O manager operations] We don't use these two new cases yet, but we will. In particular an epoll I/O manager needs to be able to report synchronous success or failure for waitRead#/waitWrite#. - - - - - 30f074d9 by Duncan Coutts at 2026-09-09T11:07:01+01:00 Switch waitRead/Write# to use new blocking return frames and update the I/O managers to set the result before resuming the blocked threads. This makes it possible for I/O managers to report synchronous exceptions from the I/O primops, but that will be done in a subsequent commit. - - - - - a8786ced by Duncan Coutts at 2026-09-09T11:07:01+01:00 Switch Poll and Select I/O managers to report sync exceptions rather than using raiseAsync with blockedOnBadFD_closure. This uses the new mechanism in the blocking frame return code to report synchronous exceptions. - - - - - 7a9df79a by Duncan Coutts at 2026-09-09T11:07:01+01:00 Remove now-unused blockedOnBadFD It was previously thrown by the select and poll I/O managers, but now they use raisePrimIOException (with an EBADF errno). - - - - - 6b0424e3 by Duncan Coutts at 2026-09-09T11:07:01+01:00 Improve the docs for delay# waitRead# and waitWrite# Document that the waitRead/Write# can throw exceptions (this was true before too), and that all of them are async exception cancellation points. - - - - - afeb2c30 by Duncan Coutts at 2026-09-09T20:08:58-04:00 Enable printf warnings for trace functions and fix resulting warnings Most of the existing printf-style functions are annotated with attributes to enable gcc/clang warnings for the printf format string, but several trace functions in Trace.h were missing this annotation. Enable them, and fix the resulting warnings. - - - - - 9a442c93 by Alan Zimmerman at 2026-09-09T20:09:36-04:00 EPA: Exact print ConDeclGADT without custom enterAnn !16321 brought in explicit capture of parens in a ConDeclGADT. The ExactPrint update introduced a modification of the fundamental function in exact printing, `enterAnn`, by splitting it into a version allowing injection of functionality normally handled by the ExactPrint class methods. This commit refactors that code, to restore the prior `enterAnn` version, by following the convention in ExactPrint of introducing a helper data structure with its own `ExactPrint` instance to achieve the same effect. - - - - - 4e9297ea by Simon Jakobi at 2026-09-11T08:32:45-04:00 ci: Actually pass --ignore-perf-failures to the testsuite driver 684c0018d9 changed the IGNORE_PERF_FAILURES handling to append to RUNTEST_ARGS with bash array syntax, but the three use sites still expand RUNTEST_ARGS as a scalar, which yields only the first array element. The appended flag was therefore dropped in every job, so perf improvements kept failing Marge Bot batches and master pipelines, contrary to #19562. Append as a string instead, matching the existing --force-colors append in test_hadrian. Fixes #27563. Assisted-by: Claude Fable 5.1 - - - - - 4f78dfdf by Simon Jakobi at 2026-09-11T08:33:24-04:00 testsuite: Give T26537 a 1.5x compile timeout Its -fregs-graph compile step tends to time out in unoptimized builds (#27188, #27776). Assisted-by: Claude Fable 5.1 - - - - - 130286e3 by Alan Zimmerman at 2026-09-11T08:34:08-04:00 EPA: Remove ListBanana / ListParens from AnnListBrackets This is a step towards making AnnList only represent lists of items which can have either braces or layout. - - - - - a9827d13 by Simon Jakobi at 2026-09-11T18:53:32-04:00 Reject ~, UNPACK and multiplicity annotations on type data fields Only `!` was rejected so far. `~`, UNPACK and multiplicity annotations were silently accepted. None of them make sense at the type level, so restriction (R3) of Note [Type data declarations] now covers all of them. Fixes #27732. Assisted-by: Claude Fable 5.1 - - - - - c71d5e23 by Alan Zimmerman at 2026-09-11T18:54:11-04:00 EPA: Add a Note for the exact print main loop - - - - - 7a108e43 by Simon Jakobi at 2026-09-12T18:35:59-04:00 FastString: Drop mkFastStringWith's constructor callback All three callers passed the same callback, a partial application of mkNewFastStringShortByteString to the string being interned. That partial application is allocated as a closure before the table lookup, on the common hit path too, although the callback is needed only after a miss. Drop the parameter and call mkNewFastStringShortByteString directly after a miss. Since nothing is passed "with" anymore, rename the function to internSB. Suggested by Simon PJ in #27528: https://gitlab.haskell.org/ghc/ghc/-/work_items/27528#note_687031 Assisted-by: Claude Fable 5 - - - - - 82c73b22 by Alan Zimmerman at 2026-09-12T18:36:38-04:00 EPA: More targeted HsDo exact print annotation HsDo is multi-purpose, as encoded in its HsDoFlavour field. Some of these are in a layout context (DoExpr, MDoExpr), others are not (ListComp, MonadComp). We are moving towards using AnnList only in layout contexts, so we switch the HsDo TTG annotation from holding an AnnList for this, to holding Either (EpToken "[", EpToken "]") AnnList This also allows us to trim down AnnListBrackets to only have braces or None, thereby opening the door for unification with the existing layout context data type EpLayout. - - - - - 749d2448 by Luite Stegeman at 2026-09-15T14:07:01-04:00 rts: handle large CONSTR closures in compacting GC The function update_fwd_large in the compacting GC could run into an unexpected object with the following error: internal error: update_fwd_large: unknown/strange object 1 Closure type 1 is CONSTR. This patch adds cases for CONSTR and CONSTR_NOCAF. This is the same problem as #27434 (large AP closures, fixed by cca0d58963), which missed this case. Fixes #27649 - - - - - 177d6155 by Luite Stegeman at 2026-09-15T14:07:02-04:00 testsuite: fix T27434 test with compacting GC Ensure that the interpreter is actually run with the compacting GC - - - - - 5796aa63 by Luite Stegeman at 2026-09-15T14:07:49-04:00 rts: initialise the stack frame header for mask_frame and apply_mask_frame We must leave the stack in consistent state before jumping to mask_frame or apply_mask_frame because they may result. Failing to do so could lead to a crash if there were waiting exceptions. Fixes #27651 - - - - - 2486cc92 by Simon Peyton Jones at 2026-09-15T14:08:36-04:00 Re-introduce the "weird SpecDict" case In this commit commit f80375dd4945350a1d784e436975b48b9c736eaf Author: Simon Peyton Jones <simon.peytonjones(a)gmail.com> Date: Sun Jun 29 15:26:58 2025 +0100 Refactor of Specialise.hs I removed a test for a dictionary with unbound type variables. This turned out to be wrong; see #27629. So this MR re-introduces it. - - - - - 8e09a46f by Duncan Coutts at 2026-09-15T20:11:35-04:00 Refactor (and rename) removeFromQueues, to simplify I/O managers Rename it to unblockAndAppendToRunQueue which better reflects what it is intended to do. The post-condition for unblockAndAppendToRunQueue is that the TSO is on the run queue or it is in the process of migrating to another cap. Previously it achieved that by always directly adding the TSO to the run queue itself. But this actually made things more complicated for the I/O managers, because it meant they needed a separate code path for notifying for cancellation compared to notifying for completion. The general notification code would always add the TSO to the run queue itself. So the improvement is to allow different cases in unblockAndAppendToRunQueue to achieve the same outcome in different ways: either directly adding to the run queue or calling helper functions that do so themselves. This then allows the new I/O managers to share code between the sync and async cancellation, and to reuse their notifyIOCompletion helpers for cancellation. This avoids a source of bugs where the completion path may be updated but the cancellation path may be forgotten, or similarly in future for sync/async operations. Update all the existing in-RTS I/O managers, and the posix timeout code. - - - - - d668782c by Duncan Coutts at 2026-09-15T20:11:35-04:00 Document that awaitCompletedTimeoutsOrIO expects an empty run queue This was true before but implicit and not relied on much. It's better to be explicit, and allow things to depend on it. - - - - - 11d938bb by Duncan Coutts at 2026-09-15T20:11:35-04:00 Store the I/O opcode and fd in the StgAsyncIOOp This will be useful in several I/O managers and it is handy for logging and debugging. It also doesn't increase the size of the StgAsyncIOOp structure. There was enough spare padding space already. Update the poll I/O manager to set the new fields. Add a helper function to convert the enum IOReadOrWrite into the enum IOOpCode. Also change IOReadOrWrite to be an enum without a typedef, for consistency with other enumerations in IOManager.h - - - - - bfa87882 by Duncan Coutts at 2026-09-15T20:11:36-04:00 Add a new I/O manager based on select() Yes, this is the second such I/O manager, but it is a modern re-implementation based on the new in-RTS I/O manager infrastructure. So it is cleaner and faster than the old select I/O manager. Why do we need another I/O manager based on select? Why isn't the poll() one good enough as a baseline portable unix I/O manager? Because macOS. Apple Inc. is why we cannot have nice things. The man page for poll on macOS documents the fact that it does not work. At least, it does not work for all files. Specifically, it does not work for device files. Whereas macOS select() does work for device files. Aaaaarg! We _do_ want to deprecate and remove the old select I/O manager, but due to macOS we cannot do that until we have a replacement. This is that replacement. Until of course a nice new k-queue I/O manager arrives, which could become the new default for macOS and FreeBSD. Interestingly, this select I/O manager is actually faster than the poll one, on Linix, in some circumstances: specifically when many Haskell threads are waiting on the same fd. The poll I/O manager does O(n) work for n threads waiting on I/O, whereas the select one does O(fds) work for the number of fds that threads are waiting on. Usually this is 1:1, so it's not noticable, but one can concoct extreme benchmarks to show the difference. - - - - - 8e9de15a by Duncan Coutts at 2026-09-15T20:11:36-04:00 Minor updates in the poll I/O manager to keep in sync with select This keeps it in sync with select one. The changes are based on code review while implementing the new select I/O manager. The two I/O managers are so similar in structure that it makes sense to try to minimise the diff between them. This should aid understanding, and fixes to both in future. - - - - - 222668bb by Duncan Coutts at 2026-09-15T20:11:36-04:00 Document the new select I/O manager in the user guide in the RTS section about I/O managers. And add a changelog entry. - - - - - 0f48735b by Cheng Shao at 2026-09-15T20:12:23-04:00 Revert "wasm: workaround WebKit bug in dyld" This reverts commit c9b8465c2c338176fcab9d197e9d31f4aee11f68. The underlying webkit bug has been fixed in https://commits.webkit.org/314219@main. Closes #27564. - - - - - 809294f1 by Luite Stegeman at 2026-09-15T20:13:08-04:00 rts: make stg_threadLabelzh return a valid pointer for unlabeled threads. This fixes a segfault in the GC caused by stg_threadLabelzh returning a 0 pointer in a GC pointer field. stg_threadLabelzh returns a tuple of type (# Int#, ByteArray# #). If a thread has no label, the second field is unused. We must still return a valid heap object pointer. Instead of returning 0, we now return stg_DEAD_SLOT_closure. fixes #27618 - - - - - e2d57026 by Luite Stegeman at 2026-09-15T20:13:54-04:00 JS: fix selector thunk handling fix a bug where entering a selector thunk could lead to a crash if the selected field was still a thunk. fixes #27788 - - - - - 1b4a622f by sheaf at 2026-09-17T02:39:13-04:00 Improvements to type/data family handling This commit makes several improvements to the treatment of type and data families in GHC: - We consistently use "type family" instead of "type synonym family" to avoid a confusion with type synonyms. For example: - OpenSynFamilyTyCon ==> OpenTypeFamilyTyCon - ClosedSynFamilyTyCon => ClosedTypeFamilyTyCon - Various functions that were specific to data families have been renamed to make this clear. For example: - tyConFamInst_maybe ==> tyConDataFamInst_maybe - isFamInstTyCon ==> isDataFamInstTyCon - 'FamTyConFlav' has been refactored so that all closed type families share a single 'ClosedTypeFamilyTyCon' constructor. The corresponding 'IfaceFamTyConFlav' type was updated similarly. This is then used to tidy up the implementation of GHC.Core.FamInstEnv.reduceTyFamApp_maybe. - - - - - c5aa9098 by sheaf at 2026-09-17T02:39:13-04:00 Small refactor of lookupFamInstEnv This commit reworks the code for looking up family instances in GHC.Core.FamInstEnv, reducing duplication a little bit. No change in behaviour. - - - - - a3ad4588 by sheaf at 2026-09-17T02:39:14-04:00 Use a type family for boxing unboxed types This commit overhauls the way in which unboxed types are boxed, as per the updated Note [Boxing constructors] in GHC.Builtin.WiredIn.Types.Box. The main change is to allow boxing to be parametrised by representation, e.g. making 'Box ty' a valid type. We achieve this by implementing 'Box' using a closed type family: newtype Box (a :: TYPE r) = Box (BoxTF r) type BoxTF :: RuntimeRep -> Type type family BoxTF r where BoxTF IntRep = BoxInt BoxTF Int8Rep = BoxInt8 BoxTF WordRep = BoxWord BoxTF LiftedRep = Any @Type BoxTF (TupleRep [r1, r2]) = (BoxTF r1, BoxTF r2) ... BoxTF (SumRep rs) = BoxSum rs This new design solves the following problems: - It allows boxing a type whose 'RuntimeRep' has not yet been determined (e.g. because we only learn the 'RuntimeRep' after constraint solving). That is, 'Box @r a' is a perfectly valid type even if 'r' is an unfilled metavariable. This is a requirement to fix #25065 (in which we need to box a type whose 'RuntimeRep' is only filled in during constraint solving). - It handles boxing of unboxed tuples and unboxed sums, via recursive boxing. See Note [Boxing TupleRep and SumRep] in GHC.Builtin.WiredIn.Types.Box. 'Box', 'BoxTF' and all of the boxing data constructors are defined in a new 'ghc-internal' module, 'GHC.Internal.Box'. This module contains nothing but wired-in declarations, and GHC never loads its interface on account of a wired-in thing (GHC.Builtin.Modules.isWiredInOnlyModule); see Note [Loading instances for wired-in things] in GHC.Iface.Load. The individual boxing data constructors are deliberately left as an internal implementation detail, and not exported. The intended API is via the two new magic 'Id's: box :: forall {r} (a :: TYPE r). a -> Box a unbox :: forall {r} (a :: TYPE r). Box a -> a exported from 'GHC.PrimOps' (in 'ghc-experimental'). The old boxing data types (IntBox, WordBox, FloatBox, DoubleBox, DictBox) are no longer exported from base (CLC proposal #421). We use this new design to consistently desugar: - parallel comprehensions (GHC.HsToCore.ListComp.{deListComp,dsMcStmt}) - then/group/using statements (GHC.HsToCore.ListComp.{dsTransStmt,dsMcStmt}) - recursive do blocks (mdo/rec) (GHC.HsToCore.Expr.dsDo) - arrows (GHC.HsToCore.Arrows) by consistently using 'box'/'unbox' to deal with unboxed types being put into big tuples. We also adapt 'GHC.Tc.Gen.Match.{tcMcStmt,tcDoStmt}' to create fresh /representation-polymorphic/ type variables for the binders that we are going to put into a big tuple (previously, GHC only allowed lifted types in that position). These desugaring of box and unbox is explained in Note [Desugaring box & unbox] in GHC.Core.Make.Box. Roughly speaking, the desugaring looks like: box @r @ty e ==> K e unbox @r @ty e ==> case e of K x -> x where 'K' is the boxing data constructor at RuntimeRep 'r'. It's slightly more complicated than that in practice: we first need to insert a cast (see Note [The canonical type of a RuntimeRep]) using the new 'CanonicalProv' 'UnivCoProvenance', and unboxed tuples/sums need recursive logic explained in Note [box/unbox for unboxed tuples and sums], including a specific 'BoxSum' datatypes for unboxed sum (which also needed a wired-in type-level list indexing type family (!!)). The desugaring happens in two ways: - Occurrences of 'box'/'unbox' emitted by the typechecker are eliminated in the 'ds_app_var' case of GHC.HsToCore.Expr. - Other code that needs to box/unbox emits the appropriate code inline. This includes the big tuple machinery of GHC.Core.Make used by the desugarer (GHC.HsToCore.{Utils,Binds,Arrows,ListComp}) as well as the float-out pass (GHC.Core.Opt.SetLevels). Core Lint checks that no occurrence of 'box'/'unbox' survives desugaring. On the way, we overhaul the litany of big tuple functions by introducing data BigTupleLayout = BoxedElements | BareElements to distinguish the two kinds of "big tuples" that GHC routinely deals with; for example 'mkBigCoreVarTupSolo' becomes 'mkBigCoreVarTup BareElements'. All of this code is moved to the new module GHC.Core.Make.BigTuple. Fixes #20864 #22336 #22473 #25065 #27331 ------------------------- Metric Decrease: T9872a ------------------------- - - - - - 4cf7628a by Evgeny Malyshev at 2026-09-17T02:39:56-04:00 Fix the CompactionFailed documentation link to compact The old Haddock reference links into base instead of ghc-compact. Use an explicit URL because ghc-compact depends on base, not vice versa. Fixes #27558 Assisted-By: OpenAI Codex - - - - - 098bba70 by Facundo Domínguez at 2026-09-17T14:57:41-04:00 Remove the call to hoistFlag from processCmdLineP This call was undesirable because it was causing a reconstruction of the list of flag processors. Even relying on list fusion would not be sufficient because we want to replace the list with a data structure with faster lookups to address #25763. The removal is done in two moves: * We move CmdLineP to CmdLine.hs * Then we move the effect of hoisting to processArgs via a new function hoistEwM - - - - - e01799c7 by Facundo Domínguez at 2026-09-17T14:57:42-04:00 Do not create duplicate flag processors for the -W flag This makes simpler implementing the command line parser with a trie map holding flag processors. If we were to allow duplicate flag processors for any flag, the trie map would need to be a multimap. - - - - - 3875b257 by Facundo Domínguez at 2026-09-17T14:57:42-04:00 Replace the list of flag processors with a trie map in `processArgs` Previously `GHC.Driver.CmdLine.findArg` was called for each command-line argument, doing a linear search on the list of flag processors each time. This was somewhat costly as the list of flag processor has near 2000 elements. A lookup with a trie map is faster in general, but the speed up is only noticeable when calling `GHC.Driver.CmdLine.processArgs` sufficient times, so the amount of lookups piles up. This could happen in large projects with many units each having many dependencies. If only a module needs to be recompiled, the user still needs to wait for all of the flag parsing to complete. The benchmark at testsuite/tests/perf/compiler/cmdline-parser shows a 10x speed up when using the trie. The trie map is implemented in `GHC.Data.StringTrie`. The design is explained in Note [Processing command line argument fast] in GHC.Driver.Session. The commit also: * adds two property-based tests for trie map operations, * adds a benchmark of the command line parser, and * renames the predicate `arg_ok` to `valid_flag_suffix` to decide what flag processor should be used when there are multiple matching prefixes on a flag. Fixes #25763. - - - - - 5236634a by Andreas Klebinger at 2026-09-17T14:58:24-04:00 Compile Word64{Map,Set} with -O2 always. This is the hottest code and even if we build GHC with -O0 otherwise -O2 pays off for these modules. Fixes #27814. - - - - - b4a91362 by Florian Ragwitz at 2026-09-20T10:05:03-07:00 hpc: Test desired HPC behaviour for class instances - - - - - c1a23c96 by Florian Ragwitz at 2026-09-20T10:05:04-07:00 Extend TcGblEnv with a mapping from instance method Ids to DFunIds We want to use this in HPC to provide better support for instance methods. This is working towards #17155. - - - - - 3d388401 by Florian Ragwitz at 2026-09-20T10:05:04-07:00 hpc: Do not create top-level boxes for generated instance methods Users care about which of their written methods are or aren't covered, not whether all of the inherited methods are covered as well. Those should be covered where they are implemented. We achieve that by stopping to generate top-level boxes which will often appear as uncovered with no clear indication as to why, and no way to fix other than excercising code the user has not written. Fixes #17155. - - - - - 6d2d850a by Florian Ragwitz at 2026-09-20T10:05:04-07:00 hpc: Provide coverage information for class instances After fixing #17155, we no longer create top-level boxes for the source spans of instance heads (previously that was the source span used for inherited/generated instance methods). With those boxes gone, we can introduce a new top-level box for each class instance with that instance head source span, and provide more meaningful coverage semantics for it. We make the use of any of the instance's methods (user-written or generated) tick this box, providing the programmer with useful information about whether or not the instance was exercised at run-time, and whether the instance might be unnecessary. - - - - - da24bc69 by Florian Ragwitz at 2026-09-20T10:05:04-07:00 hpc: Don't allocate boxes for methodless classes With the plumbing we currently have, these could never be covered, which is not helpful to hpc users. This could be improved upon further. - - - - - c97d7901 by Florian Ragwitz at 2026-09-20T10:05:04-07:00 Add a changelog entry for new HPC features - - - - - 232 changed files: - .gitlab/ci.sh - + changelog.d/25763-cmdline-opt - + changelog.d/27732 - + changelog.d/T27629 - + changelog.d/T27788-js-selector - + changelog.d/boxing-family - + changelog.d/clc-421 - + changelog.d/fix-compacting-gc-constr-27649 - + changelog.d/fix-control0-mask-trampoline - + changelog.d/fix-threadlabel-segfault-27618 - + changelog.d/hpc-classinsts - + changelog.d/select-io-manager - compiler/GHC/Builtin.hs - compiler/GHC/Builtin/KnownKeys.hs - compiler/GHC/Builtin/Modules.hs - compiler/GHC/Builtin/Uniques.hs - compiler/GHC/Builtin/WiredIn/Ids.hs - compiler/GHC/Builtin/WiredIn/Prim.hs - compiler/GHC/Builtin/WiredIn/TypeLits.hs - compiler/GHC/Builtin/WiredIn/Types.hs - + compiler/GHC/Builtin/WiredIn/Types/Box.hs - compiler/GHC/Builtin/primops.txt.pp - compiler/GHC/Core/Coercion.hs - compiler/GHC/Core/Coercion/Axiom.hs - compiler/GHC/Core/DataCon.hs - compiler/GHC/Core/FamInstEnv.hs - compiler/GHC/Core/Lint.hs - compiler/GHC/Core/Make.hs - + compiler/GHC/Core/Make/BigTuple.hs - + compiler/GHC/Core/Make/Box.hs - compiler/GHC/Core/Opt/SetLevels.hs - compiler/GHC/Core/Opt/Specialise.hs - compiler/GHC/Core/TyCo/Ppr.hs - compiler/GHC/Core/TyCo/Rep.hs - compiler/GHC/Core/TyCon.hs - compiler/GHC/Core/Type.hs - compiler/GHC/CoreToStg.hs - compiler/GHC/CoreToStg/AddImplicitBinds.hs - compiler/GHC/Data/FastString.hs - + compiler/GHC/Data/StringTrie.hs - compiler/GHC/Data/Word64Map/Internal.hs - compiler/GHC/Data/Word64Map/Strict/Internal.hs - compiler/GHC/Data/Word64Set/Internal.hs - compiler/GHC/Driver/CmdLine.hs - compiler/GHC/Driver/Main/Compile.hs - compiler/GHC/Driver/Main/Passes.hs - compiler/GHC/Driver/Session.hs - compiler/GHC/Hs/Expr.hs - compiler/GHC/Hs/Pat.hs - compiler/GHC/Hs/Utils.hs - compiler/GHC/HsToCore.hs - compiler/GHC/HsToCore/Arrows.hs - compiler/GHC/HsToCore/Binds.hs - compiler/GHC/HsToCore/Expr.hs - compiler/GHC/HsToCore/ListComp.hs - compiler/GHC/HsToCore/Ticks.hs - compiler/GHC/HsToCore/Utils.hs - compiler/GHC/Iface/Decl.hs - compiler/GHC/Iface/Load.hs - compiler/GHC/Iface/Rename.hs - compiler/GHC/Iface/Syntax.hs - compiler/GHC/Iface/Tidy.hs - compiler/GHC/IfaceToCore.hs - compiler/GHC/Parser.y - compiler/GHC/Parser/Annotation.hs - compiler/GHC/Parser/PostProcess.hs - compiler/GHC/Rename/Module.hs - compiler/GHC/Stg/Lint.hs - compiler/GHC/StgToJS/Apply.hs - compiler/GHC/StgToJS/CodeGen.hs - compiler/GHC/StgToJS/Symbols.hs - compiler/GHC/Tc/Deriv.hs - compiler/GHC/Tc/Deriv/Generate.hs - compiler/GHC/Tc/Deriv/Generics.hs - compiler/GHC/Tc/Errors/Types.hs - compiler/GHC/Tc/Gen/HsType.hs - compiler/GHC/Tc/Gen/Match.hs - compiler/GHC/Tc/Gen/Pat.hs - compiler/GHC/Tc/Gen/Splice.hs - compiler/GHC/Tc/Instance/Family.hs - compiler/GHC/Tc/Instance/Typeable.hs - compiler/GHC/Tc/Module.hs - compiler/GHC/Tc/Solver/Default.hs - compiler/GHC/Tc/Solver/FunDeps.hs - compiler/GHC/Tc/TyCl.hs - compiler/GHC/Tc/TyCl/Instance.hs - compiler/GHC/Tc/Types.hs - compiler/GHC/Tc/Utils/Backpack.hs - compiler/GHC/Tc/Utils/Monad.hs - compiler/GHC/Types/CompleteMatch.hs - compiler/GHC/Types/Id.hs - compiler/GHC/Types/Id/Info.hs - compiler/GHC/Types/Id/Make.hs - compiler/GHC/Types/TyThing.hs - compiler/GHC/Types/TyThing/Ppr.hs - compiler/GHC/Types/Unique.hs - compiler/ghc.cabal.in - docs/users_guide/exts/type_data.rst - docs/users_guide/runtime_control.rst - ghc/GHC/Driver/Session/Mode.hs - libraries/base/src/GHC/Base.hs - libraries/base/src/GHC/Exts.hs - libraries/base/src/GHC/RTS/Flags.hs - libraries/ghc-internal/ghc-internal.cabal.in - libraries/ghc-internal/include/RtsIfaceSymbols.h - + libraries/ghc-internal/src/GHC/Internal/Box.hs - libraries/ghc-internal/src/GHC/Internal/Conc/IO.hs - libraries/ghc-internal/src/GHC/Internal/Event/Thread.hs - libraries/ghc-internal/src/GHC/Internal/Exts.hs - libraries/ghc-internal/src/GHC/Internal/IO/Exception.hs - libraries/ghc-internal/src/GHC/Internal/RTS/Flags.hsc - libraries/ghc-internal/src/GHC/Internal/TypeNats.hs - libraries/ghc-internal/src/GHC/Internal/Types.hs - linters/lint-codes/LintCodes/Static.hs - rts/Capability.c - rts/ContinuationOps.cmm - rts/HeapStackCheck.cmm - rts/IOManager.c - rts/IOManager.h - rts/IOManagerInternals.h - rts/Messages.c - rts/Prelude.h - rts/PrimOps.cmm - rts/Printer.c - rts/RaiseAsync.c - rts/STM.c - rts/Schedule.c - rts/Sparks.c - rts/StableName.c - rts/StgMiscClosures.cmm - rts/ThreadPaused.c - rts/Threads.c - rts/Trace.h - rts/configure.ac - rts/include/rts/Flags.h - rts/include/rts/RtsToHsIface.h - rts/include/rts/storage/Closures.h - rts/include/stg/MiscClosures.h - rts/posix/Poll.c - rts/posix/Poll.h - rts/posix/Select.c - + rts/posix/SelectBis.c - + rts/posix/SelectBis.h - rts/posix/Timeout.c - rts/posix/Timeout.h - rts/rts.cabal - rts/sm/Compact.c - rts/sm/Evac.c - rts/sm/GC.c - rts/sm/GCUtils.c - rts/sm/MBlock.c - rts/sm/NonMoving.c - rts/sm/NonMovingMark.c - rts/sm/Storage.c - rts/sm/Sweep.c - testsuite/tests/MiniQuickCheck.hs - testsuite/tests/arrows/should_run/all.T - + testsuite/tests/arrows/should_run/arrowrun005.hs - + testsuite/tests/arrows/should_run/arrowrun005.stdout - testsuite/tests/codeGen/should_run/all.T - testsuite/tests/count-deps/CountDepsParser.stdout - + testsuite/tests/deSugar/should_compile/T25065a.hs - testsuite/tests/deSugar/should_compile/all.T - + testsuite/tests/deSugar/should_run/T20864.hs - + testsuite/tests/deSugar/should_run/T20864.stdout - + testsuite/tests/deSugar/should_run/T25065b.hs - + testsuite/tests/deSugar/should_run/T25065b.stdout - testsuite/tests/deSugar/should_run/all.T - testsuite/tests/driver/all.T - + testsuite/tests/driver/stringtrie.hs - + testsuite/tests/driver/stringtrie.stdout - testsuite/tests/ghc-api/T25121_status.stdout - + testsuite/tests/hpc/instmeths/instmeths.hs - + testsuite/tests/hpc/instmeths/instmeths.stdout - + testsuite/tests/hpc/instmeths/test.T - + testsuite/tests/indexed-types/should_run/T27331.hs - + testsuite/tests/indexed-types/should_run/T27331.stdout - + testsuite/tests/indexed-types/should_run/T27331b.hs - + testsuite/tests/indexed-types/should_run/T27331b.stdout - + testsuite/tests/indexed-types/should_run/T27331b_Plugin.hs - testsuite/tests/indexed-types/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/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/javascript/T27788.hs - + testsuite/tests/javascript/T27788.stdout - testsuite/tests/javascript/all.T - testsuite/tests/linters/notes.stdout - testsuite/tests/parser/should_compile/DumpParsedAstComments.stderr - testsuite/tests/parser/should_compile/DumpSemis.stderr - + testsuite/tests/perf/compiler/T25763.stderr - testsuite/tests/perf/compiler/all.T - testsuite/tests/printer/Test20297.stdout - + testsuite/tests/rts/T27618.hs - + testsuite/tests/rts/T27618.stdout - + testsuite/tests/rts/T27649.hs - + testsuite/tests/rts/T27649.stdout - testsuite/tests/rts/all.T - + testsuite/tests/rts/continuations/T27651.hs - + testsuite/tests/rts/continuations/T27651.stdout - testsuite/tests/rts/continuations/all.T - testsuite/tests/simplCore/should_compile/Makefile - + testsuite/tests/simplCore/should_compile/T27629.hs - + testsuite/tests/simplCore/should_compile/T27629.stderr - + testsuite/tests/simplCore/should_compile/T27629Plugin.hs - testsuite/tests/simplCore/should_compile/all.T - + testsuite/tests/type-data/should_fail/T27732a.hs - + testsuite/tests/type-data/should_fail/T27732a.stderr - + testsuite/tests/type-data/should_fail/T27732b.hs - + testsuite/tests/type-data/should_fail/T27732b.stderr - + testsuite/tests/type-data/should_fail/T27732c.hs - + testsuite/tests/type-data/should_fail/T27732c.stderr - + testsuite/tests/type-data/should_fail/T27732d.hs - + testsuite/tests/type-data/should_fail/T27732d.stderr - + testsuite/tests/type-data/should_fail/T27732e.hs - + testsuite/tests/type-data/should_fail/T27732e.stderr - + testsuite/tests/type-data/should_fail/T27732f.hs - + testsuite/tests/type-data/should_fail/T27732f.stderr - testsuite/tests/type-data/should_fail/TDStrictnessGADT.stderr - testsuite/tests/type-data/should_fail/TDStrictnessH98.stderr - testsuite/tests/type-data/should_fail/all.T - + testsuite/tests/warnings/should_fail/WExpectedNoArgError.stderr - testsuite/tests/warnings/should_fail/all.T - utils/check-exact/ExactPrint.hs - utils/check-exact/Utils.hs - utils/deriveConstants/Main.hs - utils/haddock/haddock-api/src/Haddock/Convert.hs - utils/jsffi/dyld.mjs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/305a140bf79f2cc43458ac5ed7a334… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/305a140bf79f2cc43458ac5ed7a334… You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc] Pushed new branch wip/sjakobi/T26341-tests
by Simon Jakobi (＠sjakobi) 20 Sep '26

20 Sep '26

Simon Jakobi pushed new branch wip/sjakobi/T26341-tests at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/sjakobi/T26341-tests You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc] Pushed new branch wip/sjakobi/T27675-udfm-docs
by Simon Jakobi (＠sjakobi) 20 Sep '26

20 Sep '26

Simon Jakobi pushed new branch wip/sjakobi/T27675-udfm-docs at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/sjakobi/T27675-udfm-docs You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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