September 2026 - ghc-commits

[Git][ghc/ghc][wip/sjakobi/cmmsink-touch] 2 commits: CmmSink: fix the safety argument for sinking past touch#
by Simon Jakobi (＠sjakobi) 08 Sep '26

08 Sep '26

Simon Jakobi pushed to branch wip/sjakobi/cmmsink-touch at Glasgow Haskell Compiler / GHC Commits: 5b1e1e19 by Simon Jakobi at 2026-09-08T18:52:28+02:00 CmmSink: fix the safety argument for sinking past touch# Note [Foreign calls clobber heap] claimed that sinking is intra-block, but the sinking pass also moves assignments into single-predecessor successor blocks. The correct argument is that no GC safe point can lie between a load's old and new position: after stack layout those are CmmCall nodes, which rule (C3)(d) still blocks, and suspendThread/resumeThread, which stay clobbering. Context: #27782. Assisted-by: Claude Fable 5.1 - - - - - ef34e1e3 by Simon Jakobi at 2026-09-08T19:02:41+02:00 CmmSink: classify every CallishMachOp's memory effect callishMachOpClobbersMemory now decides per constructor instead of allowing only touch# and prefetch. Most callish ops neither write memory nor imply ordering: the libm calls, the 64-bit fallbacks for 32-bit targets, the quotRem/carry/mul2 helpers, popcnt and friends, memcmp. Loads can now sink past them. Memcpy-likes, fences, atomics and suspend/resumeThread stay clobbering. See Note [Foreign calls clobber heap]. The common winning shape is a stack reload after a call return that is used after a quotRemInt#: case f x of I# y -> case quotRemInt# y d of (# q, r #) -> q +# n The reload of n stayed above the idiv, costing a load plus two moves because idiv clobbers rax and rdx. Now it is one add with a memory operand after the division. Context: #27782. Assisted-by: Claude Fable 5.1 - - - - - 6 changed files: - changelog.d/cmmsink-touch-27782 - compiler/GHC/Cmm/MachOp.hs - compiler/GHC/Cmm/Sink.hs - + testsuite/tests/codeGen/should_gen_asm/T27782b.asm - + testsuite/tests/codeGen/should_gen_asm/T27782b.cmm - testsuite/tests/codeGen/should_gen_asm/all.T Changes: ===================================== changelog.d/cmmsink-touch-27782 ===================================== @@ -1,6 +1,7 @@ section: codegen -synopsis: The Cmm sinking pass no longer treats ``touch#`` as clobbering - memory, so a load preceding a ``touch#`` can be folded into the - instruction that uses it, as in ``ByteString`` indexing. +synopsis: The Cmm sinking pass no longer treats ``touch#``, arithmetic + helpers such as ``quotRemInt#`` and ``timesWord2#``, bit operations, or + libm calls as clobbering memory, so a load preceding one of them can be + folded into the instruction that uses it, as in ``ByteString`` indexing. issues: #27782 mrs: !16650 ===================================== compiler/GHC/Cmm/MachOp.hs ===================================== @@ -885,9 +885,139 @@ callishMachOpHints op = case op of -- in GHC.Cmm.Sink. callishMachOpClobbersMemory :: CallishMachOp -> Bool callishMachOpClobbersMemory op = case op of + -- CQ[clobber-libm] + -- Q: these become C calls on most backends. Why is a C call to sin/pow + -- safe to sink a load past, given the stmCommitNestedTransaction + -- story in Note [Foreign calls clobber heap]? + -- A~ the counterexample is about RTS functions reached via ForeignTarget, + -- which stays clobbering. libm/ghc-prim helpers only read their + -- arguments and write errno, thread-local C memory no Cmm load reads. + -- Loads through caller-saved STG registers are stopped by rule (C1) + -- anyway (foreignTargetRegs in GHC.Cmm.Node). + MO_F64_Pwr -> False + MO_F64_Sin -> False + MO_F64_Cos -> False + MO_F64_Tan -> False + MO_F64_Sinh -> False + MO_F64_Cosh -> False + MO_F64_Tanh -> False + MO_F64_Asin -> False + MO_F64_Acos -> False + MO_F64_Atan -> False + MO_F64_Asinh -> False + MO_F64_Acosh -> False + MO_F64_Atanh -> False + MO_F64_Log -> False + MO_F64_Log1P -> False + MO_F64_Exp -> False + MO_F64_ExpM1 -> False + MO_F64_Fabs -> False + MO_F64_Sqrt -> False + MO_F32_Pwr -> False + MO_F32_Sin -> False + MO_F32_Cos -> False + MO_F32_Tan -> False + MO_F32_Sinh -> False + MO_F32_Cosh -> False + MO_F32_Tanh -> False + MO_F32_Asin -> False + MO_F32_Acos -> False + MO_F32_Atan -> False + MO_F32_Asinh -> False + MO_F32_Acosh -> False + MO_F32_Atanh -> False + MO_F32_Log -> False + MO_F32_Log1P -> False + MO_F32_Exp -> False + MO_F32_ExpM1 -> False + MO_F32_Fabs -> False + MO_F32_Sqrt -> False + + MO_I64_ToI -> False + MO_I64_FromI -> False + MO_W64_ToW -> False + MO_W64_FromW -> False + MO_x64_Neg -> False + MO_x64_Add -> False + MO_x64_Sub -> False + MO_x64_Mul -> False + MO_I64_Quot -> False + MO_I64_Rem -> False + MO_W64_Quot -> False + MO_W64_Rem -> False + MO_x64_And -> False + MO_x64_Or -> False + MO_x64_Xor -> False + MO_x64_Not -> False + MO_x64_Shl -> False + MO_I64_Shr -> False + MO_W64_Shr -> False + MO_x64_Eq -> False + MO_x64_Ne -> False + MO_I64_Ge -> False + MO_I64_Gt -> False + MO_I64_Le -> False + MO_I64_Lt -> False + MO_W64_Ge -> False + MO_W64_Gt -> False + MO_W64_Le -> False + MO_W64_Lt -> False + + MO_UF_Conv _ -> False + MO_S_Mul2 _ -> False + MO_S_QuotRem _ -> False + MO_U_QuotRem _ -> False + MO_U_QuotRem2 _ -> False + MO_Add2 _ -> False + MO_AddWordC _ -> False + MO_SubWordC _ -> False + MO_AddIntC _ -> False + MO_SubIntC _ -> False + MO_U_Mul2 _ -> False + + MO_VS_Quot _ _ -> False + MO_VS_Rem _ _ -> False + MO_VU_Quot _ _ -> False + MO_VU_Rem _ _ -> False + MO_I64X2_Min -> False + MO_I64X2_Max -> False + MO_W64X2_Min -> False + MO_W64X2_Max -> False + MO_Touch -> False -- pure liveness marker, no instructions MO_Prefetch_Data _ -> False -- reads memory, writes nothing - _ -> True + + MO_Memcpy _ -> True + MO_Memset _ -> True + MO_Memmove _ -> True + -- CQ[clobber-memcmp] + -- Q: memcmp reads both buffers and writes nothing, like prefetch. + -- Is there any RTS use where sinking a load past it matters? + MO_Memcmp _ -> False + + MO_PopCnt _ -> False + MO_Pdep _ -> False + MO_Pext _ -> False + MO_Clz _ -> False + MO_Ctz _ -> False + MO_BSwap _ -> False + MO_BRev _ -> False + + MO_AcquireFence -> True + MO_ReleaseFence -> True + MO_SeqCstFence -> True + MO_AtomicRMW {} -> True + -- CQ[clobber-atomic-read] + -- Q: an atomic read writes nothing. Why keep it clobbering? + -- A~ it carries an ordering: a plain load may not move past a seq-cst + -- read, and there is nothing to gain from allowing the relaxed case. + MO_AtomicRead {} -> True + MO_AtomicWrite {} -> True + MO_Cmpxchg _ -> True + MO_Xchg _ -> True + + MO_SuspendThread -> True + MO_ResumeThread -> True -- | The alignment of a 'memcpy'-ish operation. machOpMemcpyishAlign :: CallishMachOp -> Maybe Int ===================================== compiler/GHC/Cmm/Sink.hs ===================================== @@ -884,13 +884,23 @@ data AbsMem -- float accesses to heap, stack or virtual global registers stored in the -- capability (e.g. with unregisterised build, see #19237). -- --- Conversely, a few CallishMachOps neither write memory nor imply a +-- Conversely, most CallishMachOps neither write memory nor imply a -- barrier, and needn't block sinking ('callishMachOpClobbersMemory' in --- GHC.Cmm.MachOp classifies them): +-- GHC.Cmm.MachOp classifies them). Two deserve a word: +-- CQ[clobber-note-scope] +-- Q: the Note now says "most" but only explains touch# and prefetch. Where +-- is the argument for the arithmetic and libm ops? +-- A~ at callishMachOpClobbersMemory, see CQ[clobber-libm]. The +-- per-constructor rationale should live next to the classification, +-- the Note keeps the two cases that need a safety argument. +-- D~ move the touch#/prefetch bullets to the classification too, and have +-- the Note only point there. -- -- * MO_Touch is a pure liveness marker: no backend emits any code for it. --- Sinking is intra-block, so the Core-level touch# reordering hazard --- of #18040 does not arise. +-- The hazard of #18040, a read of the touched object delayed past a GC +-- safe point, cannot arise here: after stack layout the only safe points +-- are CmmCall nodes, which rule (C3)(d) still blocks, and +-- suspendThread/resumeThread, which stay clobbering. -- -- * MO_Prefetch_Data reads memory but writes nothing. ===================================== testsuite/tests/codeGen/should_gen_asm/T27782b.asm ===================================== @@ -0,0 +1,12 @@ +loadMul2: + movq + mulq + addq + movq + addq + jmp +loadBSwap: + bswapq + movq + addq + jmp ===================================== testsuite/tests/codeGen/should_gen_asm/T27782b.cmm ===================================== @@ -0,0 +1,19 @@ +#include "Cmm.h" + +// A load must sink past callish ops that don't clobber memory, so that it +// can be folded into the instruction that uses it. mul2u_64 also clobbers +// rax/rdx, so keeping the load live across it would cost extra moves. + +loadMul2 (W_ p, W_ x, W_ y) { + W_ a, hi, lo; + a = W_[p]; + (hi, lo) = prim %mul2u_64(x, y); + return (a + hi + lo); +} + +loadBSwap (W_ p, W_ x) { + W_ a, b; + a = W_[p]; + (b) = prim %bswap64(x); + return (a + b); +} ===================================== testsuite/tests/codeGen/should_gen_asm/all.T ===================================== @@ -28,6 +28,7 @@ test('T25233', [unless(arch('x86_64'), skip), test('T25233b', [unless(arch('x86_64'), skip), when(unregisterised(), skip)], compile_grep_asm, ['cmm', True, '']) test('T27782', is_amd64_codegen, compile_cmp_asm, ['cmm', '']) +test('T27782b', is_amd64_codegen, compile_cmp_asm, ['cmm', '']) is_aarch64_codegen = [ unless(arch('aarch64'), skip), when(unregisterised(), skip), View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/33f284d756ced7df18cd339911bdac… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/33f284d756ced7df18cd339911bdac… You're receiving this email because of your account on gitlab.haskell.org. 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[Git][ghc/ghc] Pushed new branch wip/T27724
by Simon Peyton Jones (＠simonpj) 08 Sep '26

08 Sep '26

Simon Peyton Jones pushed new branch wip/T27724 at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/T27724 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] 10 commits: rts: fix ctoi_tuple_spill_words getting out of sync
by Florian Ragwitz (＠rafl) 08 Sep '26

08 Sep '26

Florian Ragwitz pushed to branch wip/rafl/hpc-instances at Glasgow Haskell Compiler / GHC Commits: 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. - - - - - e4b02127 by Florian Ragwitz at 2026-09-08T06:55:31-07:00 hpc: Test desired HPC behaviour for class instances - - - - - ba47f0d2 by Florian Ragwitz at 2026-09-08T06:55:32-07:00 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. - - - - - fcc4d72d by Florian Ragwitz at 2026-09-08T06:55:32-07:00 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. - - - - - 361dd6eb by Florian Ragwitz at 2026-09-08T06:55:32-07:00 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. - - - - - 8baa9a7a by Florian Ragwitz at 2026-09-08T06:55:32-07:00 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. - - - - - 305a140b by Florian Ragwitz at 2026-09-08T06:55:32-07:00 Add a changelog entry for new HPC features - - - - - 33 changed files: - + changelog.d/fix-parallel-gc-selector-race-27477 - + changelog.d/hpc-classinsts - compiler/GHC/Hs/Doc.hs - compiler/GHC/Hs/Extension/Pass.hs - compiler/GHC/HsToCore.hs - compiler/GHC/HsToCore/Ticks.hs - compiler/GHC/Tc/Module.hs - compiler/GHC/Tc/TyCl/Instance.hs - compiler/GHC/Tc/Types.hs - compiler/GHC/Tc/Utils/Monad.hs - hadrian/src/Builder.hs - rts/Continuation.c - rts/Interpreter.c - rts/Schedule.c - rts/sm/Evac.c - + 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/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/hpc/instmeths/instmeths.hs - + testsuite/tests/hpc/instmeths/instmeths.stdout - + testsuite/tests/hpc/instmeths/test.T - + testsuite/tests/rts/T27477.hs - + testsuite/tests/rts/T27477.stdout - testsuite/tests/rts/all.T - utils/check-exact/ExactPrint.hs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/56d01e6947ba2faebf561b70b2194b… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/56d01e6947ba2faebf561b70b2194b… 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/romes/multi-threaded-debugger-p1] 23 commits: testsuite: Fix out-of-bounds access in T3586
by Rodrigo Mesquita (＠alt-romes) 08 Sep '26

08 Sep '26

Rodrigo Mesquita pushed to branch wip/romes/multi-threaded-debugger-p1 at Glasgow Haskell Compiler / GHC Commits: 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. - - - - - 54f51068 by Rodrigo Mesquita at 2026-09-08T14:46:32+01:00 wip: global break action for multi thread support the status Var must actually be global across all threads, otherwise all of them will block trying to write some Status Var no one is looking at at all have to fix these toggle untoggle things very satisfying solution with mutable state Matthew-certified big brain WIP HMmm almost there I think pretty great progressssssssss ExecOptions isolateThreadBreaks ThreadBreaksIsolationMode move to GHCi.Run.Breakpoints - - - - - 161 changed files: - + changelog.d/27556 - + changelog.d/T27744 - + changelog.d/T27749 - + changelog.d/T27764 - + changelog.d/allow-gadt-prefix-con-parens - + changelog.d/fix-parallel-gc-selector-race-27477 - + changelog.d/implicit-field-strictness-warning - changelog.d/lazy-field-annotations - + changelog.d/llvm-23 - + changelog.d/ncg-x86-bit-test-instructions - compiler/GHC.hs - 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/Utils.hs - compiler/GHC/CoreToStg/Prep.hs - compiler/GHC/Driver/Config.hs - compiler/GHC/Driver/Flags.hs - compiler/GHC/Driver/GenerateCgIPEStub.hs - compiler/GHC/Driver/Main/Compile.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/HsToCore/Quote.hs - compiler/GHC/Iface/Ext/Ast.hs - compiler/GHC/Rename/Expr.hs - compiler/GHC/Rename/HsType.hs - compiler/GHC/Rename/Module.hs - compiler/GHC/Runtime/Eval.hs - compiler/GHC/Runtime/Eval/Types.hs - compiler/GHC/Runtime/Interpreter.hs - compiler/GHC/Stg/Debug.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/TyCl.hs - compiler/GHC/Tc/TyCl/PatSyn.hs - compiler/GHC/Types/Error/Codes.hs - compiler/GHC/Types/Hint.hs - compiler/GHC/Types/Hint/Ppr.hs - compiler/GHC/Types/Tickish.hs - compiler/Language/Haskell/Syntax/Decls.hs - compiler/Language/Haskell/Syntax/Type.hs - configure.ac - docs/users_guide/exts/gadt_syntax.rst - docs/users_guide/exts/strict.rst - docs/users_guide/using-warnings.rst - ghc/GHCi/UI/Monad.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/tests/all.T - libraries/ghci/GHCi/Message.hs - libraries/ghci/GHCi/Run.hs - + libraries/ghci/GHCi/Run/Breakpoints.hs - libraries/ghci/ghci.cabal.in - 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/Continuation.c - rts/Interpreter.c - rts/ProfHeap.c - rts/Schedule.c - rts/eventlog/EventLog.c - rts/prim/atomic.c - rts/sm/Evac.c - testsuite/driver/README.md - testsuite/driver/testlib.py - + 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/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/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/patsyn/should_compile/T27744.hs - testsuite/tests/patsyn/should_compile/all.T - 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/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/all.T - + testsuite/tests/simplCore/should_compile/T27556.hs - + testsuite/tests/simplCore/should_compile/T27556.script - + testsuite/tests/simplCore/should_compile/T27749.hs - + testsuite/tests/simplCore/should_compile/T27749.stderr - testsuite/tests/simplCore/should_compile/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/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 - utils/check-exact/ExactPrint.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 The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/11468194c540e60eb9efce7a7a945e… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/11468194c540e60eb9efce7a7a945e… 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/romes/multi-threaded-debugger-p1
by Rodrigo Mesquita (＠alt-romes) 08 Sep '26

08 Sep '26

Rodrigo Mesquita pushed new branch wip/romes/multi-threaded-debugger-p1 at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/romes/multi-threaded-debugger… 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][master] EPA Fix HsCmdDo exact print with comments
by Marge Bot (＠marge-bot) 08 Sep '26

08 Sep '26

Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC Commits: 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. - - - - - 3 changed files: - compiler/GHC/Hs/Doc.hs - compiler/GHC/Hs/Extension/Pass.hs - utils/check-exact/ExactPrint.hs Changes: ===================================== compiler/GHC/Hs/Doc.hs ===================================== @@ -58,6 +58,7 @@ import Language.Haskell.Syntax.Doc import Language.Haskell.Syntax.Extension import Language.Haskell.Syntax.Module.Name +-- Exact print annotations ignore LHsDoc, so bare SrcSpan is fine type instance Anno (WithHsDocIdentifiers (HsDocString (GhcPass pass)) (GhcPass pass)) = SrcSpan deriving instance (Data pass, Data (LIdP pass), Data a) => Data (WithHsDocIdentifiers a pass) ===================================== compiler/GHC/Hs/Extension/Pass.hs ===================================== @@ -46,6 +46,7 @@ type instance XRec (GhcPass p) a = XRecGhc a -- but pass-independent, source location type XRecGhc a = GenLocated (Anno a) a +-- Exact print annotations ignore LHsDoc, so bare SrcSpan is fine type instance Anno (HsDocString (GhcPass _)) = SrcSpan type instance Anno HsDocStringChunk = SrcSpan ===================================== utils/check-exact/ExactPrint.hs ===================================== @@ -3404,13 +3404,13 @@ instance ExactPrint (HsCmd GhcPs) where e' <- markAnnotated e return (HsCmdLet (tkLet', tkIn') binds' e') - exact (HsCmdDo (an0,loc) (L l es)) = do + exact (HsCmdDo (an0,loc) es) = do debugM $ "HsCmdDo" loc' <- printStringAtAA loc "do" (an1,es') <- markAnnList' an0 $ do - ee <- mapM markAnnotated es + ee <- markAnnotated es return ee - return (HsCmdDo (an1,loc') (L l es')) + return (HsCmdDo (an1,loc') es') -- --------------------------------------------------------------------- @@ -4508,10 +4508,10 @@ instance ExactPrint [LocatedA (StmtLR GhcPs GhcPs (LocatedA (HsCmd GhcPs)))] whe Just (initStmts, ls@(L _ (LastStmt _ _body _ _))) -> do debugM $ "LocatedL [ExprLStmt: snocView" ls' <- markAnnotated ls - initStmts' <- markAnnotated initStmts + initStmts' <- mapM markAnnotated initStmts return (initStmts' ++ [ls']) _ -> do - stmts' <- markAnnotated stmts + stmts' <- mapM markAnnotated stmts return stmts' instance ExactPrint [Located HsDocStringChunk] where View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/f8b2bd8fa07a421da6d62d2c01743ed… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/f8b2bd8fa07a421da6d62d2c01743ed… 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][master] rts: Fix missing memory barrier in eval_thunk_selector (#27477)
by Marge Bot (＠marge-bot) 08 Sep '26

08 Sep '26

Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC Commits: 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 - - - - - 5 changed files: - + changelog.d/fix-parallel-gc-selector-race-27477 - rts/sm/Evac.c - + testsuite/tests/rts/T27477.hs - + testsuite/tests/rts/T27477.stdout - testsuite/tests/rts/all.T Changes: ===================================== changelog.d/fix-parallel-gc-selector-race-27477 ===================================== @@ -0,0 +1,10 @@ +section: rts +synopsis: Fix a parallel GC race on weakly-ordered architectures (AArch64) that could crash or silently corrupt the heap +description: + On weakly-ordered architectures such as AArch64 programs using + could crash during parallel garbage collection (segmentation fault + or ``internal error: eval_thunk_selector: strange selectee <n>``) or + continue running with silently corrupted heap data, due to a missing + memory barrier in the parallel GC. +mrs: !16488 +issues: #27477 ===================================== rts/sm/Evac.c ===================================== @@ -1361,7 +1361,11 @@ selector_loop: // from-space during marking, for example. We rely on the property // that evacuate() doesn't mind if it gets passed a to-space pointer. - info = RELAXED_LOAD((StgInfoTable**) &selectee->header.info); + // NB. this load must be ordered: the selectee may be updated + // concurrently by another GC thread's unchain_thunk_selectors(), + // which publishes an indirection by writing the indirectee and + // then RELEASE-storing the info pointer. See #27477. + info = ACQUIRE_LOAD((StgInfoTable**) &selectee->header.info); if (IS_FORWARDING_PTR(info)) { // We don't follow pointers into to-space; the constructor ===================================== testsuite/tests/rts/T27477.hs ===================================== @@ -0,0 +1,169 @@ +{-# LANGUAGE BangPatterns #-} + +-- Stress test for #27477: missing ACQUIRE in eval_thunk_selector +-- (rts/sm/Evac.c). +-- +-- With the bug present this test crashes or reports value mismatches +-- within a few seconds on AArch64; on strongly-ordered targets +-- it just passes. + +module Main (main) where + +import Control.Concurrent +import Control.Exception +import Control.Monad +import Data.IORef +import System.Environment +import System.Exit +import System.IO +import System.Mem (performMinorGC) + +data T = T { nxt :: T, val :: !Int } + +-- expected values and the cells that should evaluate to them +type Batch = ([Int], [T]) + +tailD, branchD, branchesPerCell :: Int +tailD = 12 -- shared tail length per cluster +branchD = 3 -- private branch length +branchesPerCell = 2 +-- tailD + branchD must stay below MAX_THUNK_SELECTOR_DEPTH (16) + +{-# NOINLINE spineEnd #-} +spineEnd :: T +spineEnd = errorWithoutStackTrace "spine end reached" + +-- Fully evaluated spine of constructors; cell i from the head has val i+1. +buildSpine :: Int -> IO T +buildSpine len = evaluate (go len (T spineEnd 0)) + where + go :: Int -> T -> T + go 0 acc = acc + go k acc = go (k - 1) (T acc k) + +-- k selector thunks, shallow-first: cell i selects from cell i-1, +-- cell 0 selects from t. If t evaluates to spine cell m (val m+1), +-- cell i evaluates to spine cell m+1+i (val m+2+i). +{-# NOINLINE selChain #-} +selChain :: Int -> T -> [T] +selChain 0 _ = [] +selChain k t = let t' = nxt t in t' : selChain (k - 1) t' + +lenL :: [a] -> Int +lenL = go 0 + where + go !n [] = n + go !n (_ : xs) = go (n + 1) xs + +everyN :: Int -> [a] -> [a] +everyN _ [] = [] +everyN n (x : xs) = x : everyN n (drop (n - 1) xs) + +-- One branch hanging off tail cell tj (which evaluates to val jval): +-- branch cell i evaluates to jval+1+i. Returned deepest-first. +{-# NOINLINE mkBranch #-} +mkBranch :: Int -> T -> IO Batch +mkBranch jval tj = do + let cells = selChain branchD tj + _ <- evaluate (lenL cells) + let expected = [ jval + 1 + i | i <- [0 .. branchD - 1] ] + pure (reverse expected, reverse cells) + +-- A cluster: one private spine, one shared tail of selectors over it, +-- branchesPerCell branches of selectors converging on every tail cell. +-- Neither the spine nor the tail is returned: they must stay reachable +-- only through the branch selectors. +buildCluster :: IO [Batch] +buildCluster = do + sp <- buildSpine (tailD + branchD + 4) + let tails = selChain tailD sp + _ <- evaluate (lenL tails) + bss <- forM (zip [0 ..] tails) $ \(j, tj) -> + replicateM branchesPerCell (mkBranch (j + 2) tj) + pure (concat bss) + +verifyBatch :: IORef Int -> Int -> Batch -> IO () +verifyBatch errs wid (es0, ts0) = go es0 ts0 + where + go (e : es) (t : ts) = do + v <- evaluate (val t) + when (v /= e) $ do + hPutStrLn stderr $ + "MISMATCH worker=" ++ show wid + ++ " expected=" ++ show e ++ " got=" ++ show v + modifyIORef' errs (+ 1) + go es ts + go _ _ = pure () + +-- simple cyclic barrier +newtype Barrier = Barrier (MVar (Int, [MVar ()])) + +newBarrier :: IO Barrier +newBarrier = Barrier <$> newMVar (0, []) + +awaitBarrier :: Barrier -> Int -> IO () +awaitBarrier (Barrier st) total = do + w <- newEmptyMVar + join $ modifyMVar st $ \(k, ws) -> + if k + 1 == total + then pure ((0, []), mapM_ (\m -> putMVar m ()) ws) + else pure ((k + 1, w : ws), takeMVar w) + +worker :: Int -> Int -> Int -> Barrier -> [IORef [Batch]] -> IORef Int -> Int -> IO () +worker rounds clusters nWorkers bar slots errs wid = + forM_ [1 .. rounds] $ \(_r :: Int) -> do + -- build fresh selector clusters, publish them + batches <- concat <$> replicateM clusters buildCluster + writeIORef (slots !! wid) batches + awaitBarrier bar nWorkers + -- root each branch's deepest cell via fresh cons cells in our own + -- nursery (so our GC thread evacuates the shared cells itself), in + -- a per-worker interleaved order so that different GC threads + -- sweep different branches of the same shared tails concurrently + published <- mapM readIORef slots + let allBatches = concat published + ordered + | nWorkers > 1 = + concat [ everyN nWorkers (drop ((wid + k) `mod` nWorkers) allBatches) + | k <- [0 .. nWorkers - 1] ] + | otherwise = allBatches + deepTs = [ t | (_, t : _) <- ordered ] + deepEs = [ e | (e : _, _) <- ordered ] + _ <- evaluate (lenL deepTs) + _ <- evaluate (lenL deepEs) + awaitBarrier bar nWorkers + -- run a parallel GC with everything live + when (wid == 0) performMinorGC + awaitBarrier bar nWorkers + -- force everything and check the values + verifyBatch errs wid (deepEs, deepTs) + awaitBarrier bar nWorkers + +main :: IO () +main = do + hSetBuffering stderr LineBuffering + args <- getArgs + let atDef d i = if length args > i then read (args !! i) else d + rounds = atDef 600 0 + clusters = atDef 48 1 + n <- getNumCapabilities + bar <- newBarrier + slots <- replicateM n (newIORef []) + errs <- newIORef 0 + dones <- forM [0 .. n - 1] $ \i -> do + done <- newEmptyMVar + _ <- forkOn i $ + (worker rounds clusters n bar slots errs i >> putMVar done Nothing) + `catch` \e -> putMVar done (Just (e :: SomeException)) + pure done + results <- mapM takeMVar dones + forM_ results $ \r -> case r of + Just e -> do + hPutStrLn stderr ("worker exception: " ++ show e) + exitWith (ExitFailure 2) + Nothing -> pure () + ec <- readIORef errs + when (ec > 0) $ do + hPutStrLn stderr ("FAILED: " ++ show ec ++ " mismatches") + exitWith (ExitFailure 2) + putStrLn "OK" ===================================== testsuite/tests/rts/T27477.stdout ===================================== @@ -0,0 +1 @@ +OK ===================================== testsuite/tests/rts/all.T ===================================== @@ -720,3 +720,12 @@ test('T27585', , extra_run_opts('+RTS -i0 -RTS') ], compile_and_run, ['-O -rtsopts']) + +test('T27477', + [ extra_run_opts('600 24 +RTS -N4 -A1m -RTS') + , req_ghc_smp + , req_target_smp + , only_ways(['threaded1', 'threaded2']) + ], + compile_and_run, ['-O2']) + View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/06eee015be4e361fe9cb33e8a608ab2… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/06eee015be4e361fe9cb33e8a608ab2… 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/jeltsch/explicit-units-doc-fix] Change `explicitUnits` to `availableUnits`
by Wolfgang Jeltsch (＠jeltsch) 08 Sep '26

08 Sep '26

Wolfgang Jeltsch pushed to branch wip/jeltsch/explicit-units-doc-fix at Glasgow Haskell Compiler / GHC Commits: 6e8e7bb6 by Wolfgang Jeltsch at 2026-09-08T16:23:47+03:00 Change `explicitUnits` to `availableUnits` The name `explicitUnits` is wrong, since only those units that are paired with `Just` values in this field are made available explicitly. - - - - - 4 changed files: - compiler/GHC/Driver/Downsweep.hs - compiler/GHC/Driver/Make.hs - compiler/GHC/SysTools/Cpp.hs - compiler/GHC/Unit/State.hs Changes: ===================================== compiler/GHC/Driver/Downsweep.hs ===================================== @@ -835,7 +835,7 @@ instantiationNodes uid unit_state = map (uid,) iuids_to_check where iuids_to_check :: [InstantiatedUnit] iuids_to_check = - nubSort $ concatMap (goUnitId . fst) (explicitUnits unit_state) + nubSort $ concatMap (goUnitId . fst) (availableUnits unit_state) where goUnitId uid = [ recur @@ -964,7 +964,7 @@ checkHomeUnitsClosed ue where external_depends = mapUniqMap (Set.fromList . unitDepends) (unitInfoMap this_units) this_units = homeUnitEnv_units this_uis - this_deps = [ toUnitId unit | (unit,Just _) <- explicitUnits this_units] + this_deps = [ toUnitId unit | (unit,Just _) <- availableUnits this_units] graphNodes :: [Node UnitId UnitId] graphNodes = go Set.empty home_id_set ===================================== compiler/GHC/Driver/Make.hs ===================================== @@ -479,7 +479,7 @@ warnUnusedPackages us dflags mod_graph = guard (not $ null $ unitExposedModules ui) return (unitId ui, unitPackageName ui, unitPackageVersion ui, flag) - unusedArgs = sortOn (\(u,_,_,_) -> u) $ mapMaybe resolve (explicitUnits us) + unusedArgs = sortOn (\(u,_,_,_) -> u) $ mapMaybe resolve (availableUnits us) warn = singleMessage $ mkPlainMsgEnvelope diag_opts noSrcSpan (DriverUnusedPackages unusedArgs) ===================================== compiler/GHC/SysTools/Cpp.hs ===================================== @@ -186,7 +186,7 @@ doCpp logger tmpfs dflags unit_env opts input_fn output_fn = do ghcVersionH <- getGhcVersionIncludeFlags dflags unit_env -- MIN_VERSION macros - let uids = explicitUnits unit_state + let uids = availableUnits unit_state pkgs = mapMaybe (lookupUnit unit_state . fst) uids mb_macro_include <- if not (null pkgs) && gopt Opt_VersionMacros dflags ===================================== compiler/GHC/Unit/State.hs ===================================== @@ -378,7 +378,7 @@ data UnitState = UnitState { -- -- This field is used for generating version macros and “unused packages” -- warnings. - explicitUnits :: [(Unit, Maybe PackageArg)], + availableUnits :: [(Unit, Maybe PackageArg)], homeUnitDepends :: Set UnitId, @@ -412,7 +412,7 @@ emptyUnitState = UnitState { trustedUnits = emptyTrustOverlay, packageNameMap = emptyUFM, preloadUnits = [], - explicitUnits = [], + availableUnits = [], homeUnitDepends = Set.empty, moduleNameProvidersMap = emptyUniqMap, pluginModuleNameProvidersMap = emptyUniqMap, @@ -912,7 +912,7 @@ mkUnitState logger unit_index cfg = do let pkgname_map = listToUFM [ (unitPackageName p, unitInstanceOf p) | p <- pkgs2 ] - -- The explicitUnits accurately reflects the set of units that are turned + -- 'availableUnits' accurately reflects the set of units that are turned -- on; as such, it also is the only way one can come up with requirements. -- The requirement context is directly based off of this: we simply -- look for nested unit IDs that are directly fed holes: the requirements @@ -954,7 +954,7 @@ mkUnitState logger unit_index cfg = do -- Force the result to avoid leaking input parameters let !state = UnitState { preloadUnits = dep_preload - , explicitUnits = explicit_pkgs + , availableUnits = explicit_pkgs , homeUnitDepends = home_unit_deps , unitInfoMap = pkg_db , trustedUnits = trustUnitsOverlay View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/6e8e7bb68dd5b45521f82089279aced… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/6e8e7bb68dd5b45521f82089279aced… 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/jeltsch/explicit-units-doc-fix] Correct the documentation of `explicitUnits`
by Wolfgang Jeltsch (＠jeltsch) 08 Sep '26

08 Sep '26

Wolfgang Jeltsch pushed to branch wip/jeltsch/explicit-units-doc-fix at Glasgow Haskell Compiler / GHC Commits: ce96a127 by Wolfgang Jeltsch at 2026-09-08T16:22:25+03:00 Correct the documentation of `explicitUnits` Resolves #27787. - - - - - 1 changed file: - compiler/GHC/Unit/State.hs Changes: ===================================== compiler/GHC/Unit/State.hs ===================================== @@ -369,10 +369,15 @@ data UnitState = UnitState { -- is always mentioned before the units it depends on. preloadUnits :: [UnitId], - -- | Units which we explicitly depend on (from a command line flag). - -- We'll use this to generate version macros and the unused packages warning. The - -- original flag which was used to bring the unit into scope is recorded for the - -- -Wunused-packages warning. + -- | The units that can be used by the respective home unit. Despite the + -- identifier, this does not just cover units that are enabled explicitly + -- using flags but also units from the package database that are enabled + -- implicitly in case @-hide-all-packages@ is absent. The former are paired + -- with 'Just' applied to the respective flags, the latter are paired with + -- 'Nothing'. + -- + -- This field is used for generating version macros and “unused packages” + -- warnings. explicitUnits :: [(Unit, Maybe PackageArg)], homeUnitDepends :: Set UnitId, @@ -907,7 +912,7 @@ mkUnitState logger unit_index cfg = do let pkgname_map = listToUFM [ (unitPackageName p, unitInstanceOf p) | p <- pkgs2 ] - -- The explicitUnits accurately reflects the set of units we have turned + -- The explicitUnits accurately reflects the set of units that are turned -- on; as such, it also is the only way one can come up with requirements. -- The requirement context is directly based off of this: we simply -- look for nested unit IDs that are directly fed holes: the requirements View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/ce96a127cf67c661a60e5c3dd37fa63… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/ce96a127cf67c661a60e5c3dd37fa63… 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/jeltsch/explicit-units-doc-fix
by Wolfgang Jeltsch (＠jeltsch) 08 Sep '26

08 Sep '26

Wolfgang Jeltsch pushed new branch wip/jeltsch/explicit-units-doc-fix at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/jeltsch/explicit-units-doc-fix 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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