Wolfgang Jeltsch pushed to branch wip/jeltsch/stm-exception-improvements at Glasgow Haskell Compiler / GHC Commits: db959f83 by Simon Jakobi at 2026-08-14T15:16:44-04:00 testsuite: Expect length001 failure in nonmoving_thr_sanity length001 relies on an optimization rule to avoid excessive stack use. The nonmoving_thr_sanity way does not enable optimization, so classify its stack overflow as an expected failure, as is already done for the other unoptimized nonmoving ways. Assisted-by: gpt-5.6-sol via Codex CLI - - - - - 4f2b7d90 by Simon Jakobi at 2026-08-14T15:16:44-04:00 testsuite: Omit T22859 in nonmoving threaded ways T22859 checks allocation-limit handlers with output that depends on precise allocation behaviour. The nonmoving threaded ways change where these limits are reached, just as the already-omitted LLVM ways do. Omit these ways instead of treating their incidental output differences as test failures. Assisted-by: gpt-5.6-sol via Codex CLI - - - - - c4abddcb by Simon Jakobi at 2026-08-14T15:16:44-04:00 rts/js: Implement eq_thread, and test Eq/Ord ThreadId (#16761) Since d1f3c63701, Eq ThreadId is implemented via the RTS function eq_thread, but the JS RTS never provided it, so comparing ThreadIds for equality on the JS backend crashed with ReferenceError: h$eq_thread is not defined Like the C implementation, h$eq_thread uses pointer equality: The JS RTS has exactly one thread object per thread. Since previously no test exercised eq_thread directly, this commit adds a test covering equality, its stability across GC, and agreement with Ord. Assisted-by: Claude Fable 5 - - - - - 4a7defa1 by Simon Jakobi at 2026-08-14T15:16:44-04:00 testsuite: Make listThreads1 insensitive to the RTS's own threads listThreads1 expected `listThreads` to return exactly [ThreadId 1]. That holds only under a non-threaded RTS. Under a threaded RTS however there are more threads present, so we change the test to simply check that `myThreadId` is present in the list. Assisted-by: Claude Opus 5 - - - - - b757727a by Vladislav Zavialov at 2026-08-14T15:17:27-04:00 Fix tcLookupId panic with RequiredTypeArguments and PatternSynonyms (#27586) The arguments declared on the left-hand side of a pattern synonym are looked up as term variables bound by its right-hand side. Prior to this patch, that lookup panicked with RequiredTypeArguments: data T a where MkT :: forall a -> T a pattern P :: Int -> T Int pattern P x = MkT x On the RHS, `x` looks like a term argument, so the renamer binds it in the term namespace. Only during type checking does it turn out to be a type variable, so the lookup on the LHS finds an ATyVar rather than an ATcId. As the lookup was done with tcLookupId, it resulted in a panic. Now the arguments are looked up with tcLookupPatSynArg, which reports an illegal term-level use of `x`, just as an ordinary function definition `f (MkT x) = x` does. Test cases: T27586a T27586b T27586c Assisted-by: Claude Opus 5 - - - - - c130188d by Rodrigo Mesquita at 2026-08-15T06:29:53-04:00 loopImports: Don't dup ms_uid in summary imports We were writing the ms_unitid of the mod summary with every single import of that module That complicated the code (as though the UnitId in that list could ever be something else) and also allocates unnecessarily per every mod import. Very slight allocation decrease measured locally in a few tests: (MultiComponentModulesRecomp: -0.06%; MultiComponentModulesRecomp100: -0.05%) Purely a clean up. - - - - - c71166a8 by Rodrigo Mesquita at 2026-08-15T06:29:53-04:00 downsweep: make control flow simpler and cache correct This refactor extracts the control flow of downsweep into a single function `dfsBuild`, which takes care of iteratively expanding and traversing all nodes of the in-construction module graph necessary to build a full `ModuleGraph`. There are three levels of caching going on, all of which are necessary to make sure we don't do repeated work (notably, NEVER summarise the same module twice). 1. `dfsBuild` accumulates the final module graph and never revisits the same node of the module graph. Cache is keyed by the final `ModuleGraph`s `NodeKey`s. 2. For Module A in home-unit u1, each import in the list of imports needs to be *found* (call to `findImportedModuleWithIsBoot`): at this point, we only have the `ModuleName` of the import, not the `Module`. This *finding* is somewhat expensive, so we cache it as well (`ImportsCache`). The cache key is the home-unit to which the module belongs~[1], the import package qualifier, and the ModuleName. [1] Different home-units will have different package flags, which means potentially different `Module` resolution for the same `ModuleName`. 3. The most expensive operation we want to avoid is summarising a `Module` into a `ModSummary`, which notably involves parsing the module header from scratch. The third cache, in essence, maps a `Module` to its `ModSummary` (named `ModSummaryCache`). This cache upholds the invariant: we NEVER summarise the same module twice. In practice, the cache key is the Module's UnitId and the Source path; the reason is we need to distinguish between `.hs` and `.hs-boot` files, as their summaries will differ. Note that (2) can't guarantee this alone: Two ModuleName imports in separate units can (and likely do) map to the same `Module`. Note that the previous implementation failed to achieve the no-duplicate-work summarisation invariant, and we ended up doing a quadratic amount of processing in scenarios like test `MultiComponentModules100`. See also Note [Downsweep Control Flow and Caching] Fixes #27461 Perf changes: MultiComponentModules(normal) ghc/alloc 2,097,389,264 1,992,186,736 -5.0% GOOD MultiComponentModules100(normal) ghc/alloc 24,310,173,770 21,293,867,360 -12.4% GOOD MultiComponentModulesRecomp(normal) ghc/alloc 602,761,394 498,543,984 -17.3% GOOD MultiComponentModulesRecomp100(normal) ghc/alloc 11,885,968,240 8,895,404,864 -25.2% GOOD ------------------------- Metric Decrease: MultiComponentModules MultiComponentModules100 MultiComponentModulesRecomp MultiComponentModulesRecomp100 ------------------------- - - - - - ebc4047b by Rodrigo Mesquita at 2026-08-15T06:29:53-04:00 implicitRequirementsShallow can never reach HoleUnit findImportedModule will never return `HoleUnit` for a `ModuleName` (a `HoleUnit` can only be found as a signature instantiation, never as a directly *imported* thing) Therefore, we can drop `[ModuleName]` returned by `implicitRequirementsShallow`, which makes many things dead code. Namely, the call to `implicitRequirementsShallow` from GHC.Driver.Downsweep which was a performance bottleneck (for doing lots of duplicate work in findImportedModule) is now entirely gone. Fixes #27053 In an MR with this patch and the downsweep refactor (previous commit), CI says: MultiComponentModules(normal) ghc/alloc 2,097,396,728 1,943,662,304 -7.3% GOOD MultiComponentModules100(normal) ghc/alloc 24,310,182,136 17,227,574,440 -29.1% GOOD MultiComponentModulesRecomp(normal) ghc/alloc 602,769,518 449,973,656 -25.3% GOOD MultiComponentModulesRecomp100(normal) ghc/alloc 11,885,976,408 4,828,894,160 -59.4% GOOD ------------------------- Metric Decrease: MultiComponentModules MultiComponentModules100 MultiComponentModulesRecomp MultiComponentModulesRecomp100 ------------------------- - - - - - 85a6ab01 by Rodrigo Mesquita at 2026-08-15T06:29:53-04:00 downsweep: Cache negative results When traversing a module graph structure, a uniquely identified node should always expand to the same thing. I don't see how visiting the same node which failed to be expanded a first time would ever successfully expand the second time we try to expand it (eg. when coming from a different edge to it -- it is still the same node!). The node expansion is local, based just based on the node itself, not on the path to get there. Therefore, this patch removes the weird behavior and commentary of `dfsBuild` wrt to `Nothing` not being cached and being potentially expanded a second time around to something different, which was misleading and, ultimately, incorrect. Now, we have a `MGRes`, which is more explicit about a node being Skipped just being a node that is ignored whenever it is found (and that skip is cached) -- and we may want to do this due to failures or due to just trying nodes which might not work on purpose, like hs-boots. We uniformly cache positive and negative results and remove the assumption that there might be an ordering in which the same node visited at a later time might be expanded differently. This makes it possible to traverse the module nodes in parallel without a change in behavior, since there's no longer a hidden ordering requirement. - - - - - 56747c3f by Rodrigo Mesquita at 2026-08-15T06:29:53-04:00 Organize and clean-up GHC.Driver.Downsweep Simply some cosmetic changes, moving definitions around to structure the module better into its relevant sections (In go (ns ++ ss), it's not a problem to use ++ because it's a good producer and we won't have to append fully before processing the next item in go) - - - - - 12f64118 by Wolfgang Jeltsch at 2026-08-15T06:31:12-04:00 Add support for textual output of bytecode file content - - - - - a737df91 by Brandon Chinn at 2026-08-15T12:40:25-04:00 Add law in qualified strings doc - - - - - e3188581 by Zubin Duggal at 2026-08-15T12:41:06-04:00 DmdAnal: Fix maxDmdType We need to eta expand the smaller DmdType using defaultArgDmd, like in lubDmdType. Introduce zipDmdType as a common combinator to implement both maxDmdType and lubDmdType uniformly. fixes #27626 - - - - - ca9b0b22 by mangoiv at 2026-08-15T12:41:47-04:00 hadrian: set the executable bit for hie-bios.bat - - - - - 1aac7095 by sheaf at 2026-08-16T04:37:16-04:00 Avoid wasteful allocations in mkTyConAppCo The idiom "traverse isReflCo_maybe" followed by "map fst" used in 'GHC.Core.Coercion.mkTyConAppCo' was allocating a lot of waste. This commit uses 'GHC.Data.Unboxed.traverseMaybeUB' to avoid all these unnecessary intermediate allocations. In a quick microbenchmark for 'mkTyConAppCo', this change resulted in: - refl case (all argument coercions are reflexive): - -60% runtime - -80% allocations - non-refl case: - from 0% to -12% runtime (depending on which argument is non-refl) - from 0% to -70% allocations ( -- '' -- ) Fixes #27648 ------------------------- Metric Decrease: FamAppCachePerf SimplCastPerf T12425 T15703 T26426 T3064 T9872a T9872b T9872b_defer T9872c T9872d T5321Fun T9020 T9630 TcPlugin_RewritePerf Metric Increase: LinkableUsage02 ------------------------- - - - - - 3915e982 by Alan Zimmerman at 2026-08-16T04:37:58-04:00 EPA: Remove al_trailing from AnnList It was not being used - - - - - fed942ac by Andreas Klebinger at 2026-08-17T12:11:57-04:00 testsuite: Use sigkill in process009. SIGHUB might have been blocked by a (grand)*parent of the test. In such cases the test would fail as the python process would simply exist gracefully instead of committing to a premature end. By using SIGKILL we can rely on the signal not being blocked, fixing #27578 in the process. - - - - - 574c875f by Andreas Klebinger at 2026-08-17T12:12:39-04:00 Simplify comparison in DFM.hs Fixes #27669 - - - - - d8f1a2a3 by Alan Zimmerman at 2026-08-17T12:13:18-04:00 TTG: Add extension points to BooleanFormula They are currently unused, but will be used for exact print annotations next, allowing us to get rid of LocatedBF / SrcSpanAnnBF - - - - - 93a2b20f by Andreas Klebinger at 2026-08-18T04:31:04-04:00 Fix a number of incorrect module references: Fix module reference in Note [DataCon wrappers are conlike]. Fix module reference in Note [Detailed InertCans Invariants]. Fix module reference in Note [GHC's data format representations]. Fix module reference in Note [Grand plan for static forms]. Fix module reference in Note [How tuples work]. Fix module reference in Note [Solved dictionaries]. Fix module reference in Note [Stacktraces from Info Table Provenance Entries (IPE based stack unwinding)]. Fix module reference in Note [The VarBndr type and its uses]. Found the incorrect references with a llm. - - - - - eb0dfb01 by Simon Jakobi at 2026-08-18T04:31:44-04:00 ci: Run stack-hadrian-build only in full-ci pipelines The job exists to catch changes that break hadrian/build-stack (#18726), but nothing in the pipeline depends on it, and it can only break when hadrian's dependencies change. Restricting it to full-ci (like hadrian-multi) still covers marge-bot merge batches, so such breakage cannot reach master unnoticed, while ordinary validate pipelines skip the job. Assisted-by: Claude Fable 5 - - - - - b9160962 by Simon Jakobi at 2026-08-20T14:57:52-04:00 testsuite: Show baseline sample count and range in perf failures A perf baseline is the mean of all samples recorded for a commit, and it prints as a single number, hiding how far the samples spread. When the spread is wide, this can indicate an unstable metric that isn't actually useful as a signal for the perf tests. For example, in #27602, T27336's peak_megabytes_allocated baseline showed as 757 when the underlying samples were 605 and 909. When the baseline is averaged from more than one sample, say so in the failure output: the one-line stat-failure reason shows the sample range, and the detail block lists the raw samples. Single-sample baselines print exactly as before. Context: #27602 Assisted-by: Claude Fable 5 - - - - - a4979877 by Simon Jakobi at 2026-08-20T14:57:52-04:00 testsuite: Fold Baseline into CommitMetric A Baseline was just a CommitMetric plus the commit it came from, built by copying fields across. Since get_commit_metric already knows that commit, record it on CommitMetric itself and drop Baseline. This also collapses both branches of find_baseline into plain returns. Assisted-by: Claude Fable 5 - - - - - 99fb8d68 by Simon Jakobi at 2026-08-20T14:57:52-04:00 ci: Clarify comment on pushing perf notes after failures Context: #27602 Assisted-by: Claude Fable 5 - - - - - 2ca87972 by Alan Zimmerman at 2026-08-20T14:58:36-04:00 EPA: Remove LocatedBC / SrcSpanBF The custom annotations are now in the BooleanFormula TTG extension points, so LBooleanFormula can now use the standard LocatedA. - - - - - d2bc32aa by Simon Peyton Jones at 2026-08-21T12:59:26-04:00 Better handling of serialisation of wired-in names Fixes #27501 - - - - - d2795ffc by Alan Zimmerman at 2026-08-21T13:00:05-04:00 EPA: Remove NoEpTok/NoEpUniTok, using an unhelpful SrcSpan instead Also introduce helper functions noEpTok and noEpUniTok to serve as simple replacements in code inserting an token annotation without location information. - - - - - b5d29ab8 by Brandon Chinn at 2026-08-25T18:42:08-04:00 Add Data.RealFloat and Infinity/NegInfinity/NaN pattern synonyms (#26961) - - - - - e60eb3bc by Andreas Klebinger at 2026-08-25T18:42:59-04:00 rts linker: Fix pointer arithmetic issue in flushInstructionCacheRISCV64 We accidentally operated over `uint64_t*` when we should use `uint8_t`. Fixes #27569 - - - - - c1653dc0 by Wolfgang Jeltsch at 2026-08-26T16:44:58+03:00 Add `rethrowSTM` and improve STM-related documentation Adding `rethrowSTM` resolves #26758. The implementation of `rethrowSTM` is completely analogous to the one of `rethrowIO`. The following is established for the documentation of `throwSTM` and `catchSTM`: * Both operations are directly described as analogs of their `IO` counterparts. * There is no reference to `throw` in the documentation of `throwSTM`, because, although such a reference is great in the documentation of `throwIO`, it is somewhat out of place in the documentation of `throwSTM`. * Instead of repeating part of `throwIO`’s documentation, the documentation of `throwSTM` just recommends using `throwSTM` instead of `throw` and references the corresponding arguments in the documentation of `throwIO`. - - - - - 142 changed files: - .gitlab-ci.yml - .gitlab/ci.sh - + changelog.d/27626 - + changelog.d/T27586 - + changelog.d/downsweep-refactor - + changelog.d/rethrow-stm - + changelog.d/show-byte-code - compiler/GHC/Builtin.hs - compiler/GHC/Builtin/WiredIn/Types.hs - compiler/GHC/ByteCode/Serialize.hs - + compiler/GHC/ByteCode/Show.hs - compiler/GHC/CmmToAsm/Format.hs - compiler/GHC/Core/Class.hs - compiler/GHC/Core/Coercion.hs - compiler/GHC/CoreToIface.hs - compiler/GHC/Data/BooleanFormula.hs - compiler/GHC/Data/Unboxed.hs - compiler/GHC/Data/Word64Map/Internal.hs - compiler/GHC/Data/Word64Map/Lazy.hs - compiler/GHC/Data/Word64Map/Strict.hs - compiler/GHC/Data/Word64Map/Strict/Internal.hs - compiler/GHC/Driver/Backpack.hs - compiler/GHC/Driver/Downsweep.hs - compiler/GHC/Driver/Env.hs - compiler/GHC/Driver/GenerateCgIPEStub.hs - compiler/GHC/Hs.hs - compiler/GHC/Hs/Dump.hs - compiler/GHC/Hs/Utils.hs - compiler/GHC/Iface/Binary.hs - compiler/GHC/Iface/Ext/Ast.hs - compiler/GHC/Iface/Syntax.hs - compiler/GHC/Iface/Tidy/StaticPtrTable.hs - compiler/GHC/IfaceToCore.hs - compiler/GHC/Parser.y - compiler/GHC/Parser/Annotation.hs - compiler/GHC/Parser/PostProcess.hs - compiler/GHC/Tc/Solver/InertSet.hs - compiler/GHC/Tc/TyCl/Class.hs - compiler/GHC/Tc/TyCl/PatSyn.hs - compiler/GHC/Tc/Utils/Backpack.hs - compiler/GHC/Types/Demand.hs - compiler/GHC/Types/Id/Make.hs - compiler/GHC/Types/Unique/DFM.hs - compiler/GHC/Types/Var.hs - 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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/module/mod185.stderr - testsuite/tests/parser/should_compile/DumpParsedAst.stderr - testsuite/tests/parser/should_compile/DumpParsedAstComments.stderr - testsuite/tests/parser/should_compile/DumpRenamedAst.stderr - testsuite/tests/parser/should_compile/DumpSemis.stderr - testsuite/tests/parser/should_compile/DumpTypecheckedAst.stderr - testsuite/tests/parser/should_compile/KindSigs.stderr - testsuite/tests/parser/should_compile/T14189.stderr - testsuite/tests/parser/should_compile/T15279.stderr - testsuite/tests/parser/should_compile/T15323.stderr - testsuite/tests/parser/should_compile/T20452.stderr - testsuite/tests/parser/should_compile/T20718.stderr - testsuite/tests/parser/should_compile/T20718b.stderr - testsuite/tests/parser/should_compile/T20846.stderr - testsuite/tests/parser/should_compile/T23315/T23315.stderr - testsuite/tests/printer/AnnotationNoListTuplePuns.stdout - testsuite/tests/printer/T18791.stderr - testsuite/tests/printer/Test20297.stdout - testsuite/tests/printer/Test24533.stdout - testsuite/tests/process/process009.hs - testsuite/tests/process/process009.stdout - testsuite/tests/rts/all.T - + testsuite/tests/show-bytecode/Example.hs - + testsuite/tests/show-bytecode/Makefile - + testsuite/tests/show-bytecode/all.T - + testsuite/tests/show-bytecode/normalize - + testsuite/tests/show-bytecode/show-bytecode-breakpoints.stdout - + testsuite/tests/show-bytecode/show-bytecode-breakpoints.stdout-javascript-unknown-ghcjs - + testsuite/tests/show-bytecode/show-bytecode-hpc.stdout - + testsuite/tests/show-bytecode/show-bytecode-vanilla.stdout - + testsuite/tests/show-bytecode/show-bytecode-vanilla.stdout-javascript-unknown-ghcjs - testsuite/tests/splice-imports/SI35.hs - + testsuite/tests/vdq-rta/should_fail/T27586a.hs - + testsuite/tests/vdq-rta/should_fail/T27586a.stderr - + testsuite/tests/vdq-rta/should_fail/T27586b.hs - + testsuite/tests/vdq-rta/should_fail/T27586b.stderr - + testsuite/tests/vdq-rta/should_fail/T27586c.hs - + testsuite/tests/vdq-rta/should_fail/T27586c.stderr - testsuite/tests/vdq-rta/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/check-ppr/Main.hs - utils/haddock/haddock-api/src/Haddock/Backends/Xhtml/Decl.hs - utils/haddock/haddock-api/src/Haddock/Interface/Rename.hs - utils/haddock/haddock-api/src/Haddock/Types.hs The diff was not included because it is too large. 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