Matthew Pickering pushed to branch wip/fix-eventlog-flush-deadlock at Glasgow Haskell Compiler / GHC Commits: 741da00c by Ben Gamari at 2025-11-12T03:38:20-05:00 template-haskell: Better describe getQ semantics Clarify that the state is a type-indexed map, as suggested by #26484. - - - - - 8b080e04 by ARATA Mizuki at 2025-11-12T03:39:11-05:00 Fix incorrect markups in the User's Guide * Correct markup for C--: "C-\-" in reST * Fix internal links * Fix code highlighting * Fix inline code: Use ``code`` rather than `code` * Remove extra backslashes Fixes #16812 Co-authored-by: sheaf <sam.derbyshire@gmail.com> - - - - - a00840ea by Simon Peyton Jones at 2025-11-14T15:23:56+00:00 Make TYPE and CONSTRAINT apart again This patch finally fixes #24279. * The story started with #11715 * Then #21623 articulated a plan, which made Type and Constraint not-apart; a horrible hack but it worked. The main patch was commit 778c6adca2c995cd8a1b84394d4d5ca26b915dac Author: Simon Peyton Jones <simonpj@microsoft.com> Date: Wed Nov 9 10:33:22 2022 +0000 Type vs Constraint: finally nailed * #24279 reported a bug in the above big commit; this small patch fixes it commit af6932d6c068361c6ae300d52e72fbe13f8e1f18 Author: Simon Peyton Jones <simon.peytonjones@gmail.com> Date: Mon Jan 8 10:49:49 2024 +0000 Make TYPE and CONSTRAINT not-apart Issue #24279 showed up a bug in the logic in GHC.Core.Unify.unify_ty which is supposed to make TYPE and CONSTRAINT be not-apart. * Then !10479 implemented "unary classes". * That change in turn allows us to make Type and Constraint apart again, cleaning up the compiler and allowing a little bit more expressiveness. It fixes the original hope in #24279, namely that `Type` and `Constraint` should be distinct throughout. - - - - - c0a1e574 by Georgios Karachalias at 2025-11-15T05:14:31-05:00 Report all missing modules with -M We now report all missing modules at once in GHC.Driver.Makefile.processDeps, as opposed to only reporting a single missing module. Fixes #26551. - - - - - c9fa3449 by Sylvain Henry at 2025-11-15T05:15:26-05:00 JS: fix array index for registers We used to store R32 in h$regs[-1]. While it's correct in JavaScript, fix this to store R32 in h$regs[0] instead. - - - - - 9e469909 by Sylvain Henry at 2025-11-15T05:15:26-05:00 JS: support more than 128 registers (#26558) The JS backend only supported 128 registers (JS variables/array slots used to pass function arguments). It failed in T26537 when 129 registers were required. This commit adds support for more than 128 registers: it is now limited to maxBound :: Int (compiler's Int). If we ever go above this threshold the compiler now panics with a more descriptive message. A few built-in JS functions were assuming 128 registers and have been rewritten to use loops. Note that loops are only used for "high" registers that are stored in an array: the 31 "low" registers are still handled with JS global variables and with explicit switch-cases to maintain good performance in the most common cases (i.e. few registers used). Adjusting the number of low registers is now easy: just one constant to adjust (GHC.StgToJS.Regs.lowRegsCount). No new test added: T26537 is used as a regression test instead. - - - - - 0a64a78b by Sven Tennie at 2025-11-15T20:31:10-05:00 AArch64: Simplify CmmAssign and CmmStore The special handling for floats was fake: The general case is always used. So, the additional code path isn't needed (and only adds complexity for the reader.) - - - - - 15b311be by sheaf at 2025-11-15T20:32:02-05:00 SimpleOpt: refactor & push coercions into lambdas This commit improves the simple optimiser (in GHC.Core.SimpleOpt) in a couple of ways: - The logic to push coercion lambdas is shored up. The function 'pushCoercionIntoLambda' used to be called in 'finish_app', but this meant we could not continue to optimise the program after performing this transformation. Now, we call 'pushCoercionIntoLambda' as part of 'simple_app'. Doing so can be important when dealing with unlifted newtypes, as explained in Note [Desugaring unlifted newtypes]. - The code is re-structured to avoid duplication and out-of-sync code paths. Now, 'simple_opt_expr' defers to 'simple_app' for the 'App', 'Var', 'Cast' and 'Lam' cases. This means all the logic for those is centralised in a single place (e.g. the 'go_lam' helper function). To do this, the general structure is brought a bit closer to the full-blown simplifier, with a notion of 'continuation' (see 'SimpleContItem'). This commit also modifies GHC.Core.Opt.Arity.pushCoercionIntoLambda to apply a substitution (a slight generalisation of its existing implementation). - - - - - b33284c7 by sheaf at 2025-11-15T20:32:02-05:00 Improve typechecking of data constructors This commit changes the way in which we perform typecheck data constructors, in particular how we make multiplicities line up. Now, impedance matching occurs as part of the existing subsumption machinery. See the revamped Note [Typechecking data constructors] in GHC.Tc.Gen.App, as well as Note [Polymorphisation of linear fields] in GHC.Core.Multiplicity. This allows us to get rid of a fair amount of hacky code that was added with the introduction of LinearTypes; in particular the logic of GHC.Tc.Gen.Head.tcInferDataCon. ------------------------- Metric Decrease: T10421 T14766 T15164 T15703 T19695 T5642 T9630 WWRec ------------------------- - - - - - b6faf5d0 by sheaf at 2025-11-15T20:32:02-05:00 Handle unsaturated rep-poly newtypes This commit allows GHC to handle unsaturated occurrences of unlifted newtype constructors. The plan is detailed in Note [Eta-expanding rep-poly unlifted newtypes] in GHC.Tc.Utils.Concrete: for unsaturated unlifted newtypes, we perform the appropriate representation-polymorphism check in tcInstFun. - - - - - 682bf979 by Mike Pilgrem at 2025-11-16T16:44:14+00:00 Fix #26293 Valid stack.yaml for hadrian - - - - - acc70c3a by Simon Peyton Jones at 2025-11-18T16:21:20-05:00 Fix a bug in defaulting Addresses #26582 Defaulting was doing some unification but then failing to iterate. Silly. I discovered that the main solver was unnecessarily iterating even if there was a unification for an /outer/ unification variable, so I fixed that too. - - - - - c12fa73e by Simon Peyton Jones at 2025-11-19T02:55:01-05:00 Make PmLit be in Ord, and use it in Map This MR addresses #26514, by changing from data PmAltConSet = PACS !(UniqDSet ConLike) ![PmLit] to data PmAltConSet = PACS !(UniqDSet ConLike) !(Map PmLit PmLit) This matters when doing pattern-match overlap checking, when there is a very large set of patterns. For most programs it makes no difference at all. For the N=5000 case of the repro case in #26514, compiler mutator time (with `-fno-code`) goes from 1.9s to 0.43s. All for the price for an Ord instance for PmLit - - - - - 41b84f40 by sheaf at 2025-11-19T02:55:52-05:00 Add passing tests for #26311 and #26072 This commit adds two tests cases that now pass since landing the changes to typechecking of data constructors in b33284c7. Fixes #26072 #26311 - - - - - 1faa758a by sheaf at 2025-11-19T02:55:52-05:00 mkCast: weaken bad cast warning for multiplicity This commit weakens the warning message emitted when constructing a bad cast in mkCast to ignore multiplicity. Justification: since b33284c7, GHC uses sub-multiplicity coercions to typecheck data constructors. The coercion optimiser is free to discard these coercions, both for performance reasons, and because GHC's Core simplifier does not (yet) preserve linearity. We thus weaken 'mkCast' to use 'eqTypeIgnoringMultiplicity' instead of 'eqType', to avoid getting many spurious warnings about mismatched multiplicities. - - - - - 55eab80d by Sylvain Henry at 2025-11-20T17:33:13-05:00 Build external interpreter program on demand (#24731) This patch teaches GHC how to build the external interpreter program when it is missing. As long as we have the `ghci` library, doing this is trivial so most of this patch is refactoring for doing it sanely. - - - - - 08bbc028 by Rodrigo Mesquita at 2025-11-20T17:33:54-05:00 Add tests for #23973 and #26565 These were fixed by 4af4f0f070f83f948e49ad5d7835fd91b8d3f0e6 in !10417 - - - - - 6b42232c by sheaf at 2025-11-20T17:34:35-05:00 Mark T26410_ffi as fragile on Windows As seen in #26595, this test intermittently fails on Windows. This commit marks it as fragile, until we get around to fixing it. - - - - - b7b7c049 by Andrew Lelechenko at 2025-11-21T21:04:01+00:00 Add nubOrd / nubOrdBy to Data.List and Data.List.NonEmpty As per https://github.com/haskell/core-libraries-committee/issues/336 - - - - - 352d5462 by Marc Scholten at 2025-11-22T10:33:03-05:00 Fix haddock test runner to handle UTF-8 output xhtml 3000.4.0.0 now produces UTF-8 output instead of escaping non-ASCII characters. When using --test-accept it previously wrote files in the wrong encoding because they have not been decoded properly when reading the files. - - - - - 2cf1b3a1 by Matthew Pickering at 2025-11-25T11:37:14+00:00 rts: Fix a deadlock with eventlog flush interval and RTS shutdown The ghc_ticker thread attempts to flush at the eventlog tick interval, this requires waiting to take all capabilities. At the same time, the main thread is shutting down, the schedule is stopped and then we wait for the ticker thread to finish. Therefore we are deadlocked. The solution is to use `newBoundTask/exitMyTask`, so that flushing can cooperate with the scheduler shutdown. Fixes #26573 - - - - - 179 changed files: - compiler/GHC.hs - compiler/GHC/Builtin/Types/Prim.hs - compiler/GHC/CmmToAsm/AArch64/CodeGen.hs - compiler/GHC/Core.hs - compiler/GHC/Core/Coercion.hs - compiler/GHC/Core/Coercion/Opt.hs - compiler/GHC/Core/DataCon.hs - compiler/GHC/Core/Lint.hs - compiler/GHC/Core/Multiplicity.hs - compiler/GHC/Core/Opt/Arity.hs - compiler/GHC/Core/Opt/Simplify/Iteration.hs - compiler/GHC/Core/RoughMap.hs - compiler/GHC/Core/SimpleOpt.hs - compiler/GHC/Core/TyCo/FVs.hs - compiler/GHC/Core/TyCo/Rep.hs - compiler/GHC/Core/Type.hs - compiler/GHC/Core/Unify.hs - compiler/GHC/Core/Utils.hs - compiler/GHC/Driver/Config/Core/Lint.hs - + compiler/GHC/Driver/Config/Interpreter.hs - compiler/GHC/Driver/Config/Linker.hs - compiler/GHC/Driver/DynFlags.hs - compiler/GHC/Driver/MakeFile.hs - compiler/GHC/Driver/Pipeline.hs - compiler/GHC/Driver/Pipeline/Execute.hs - compiler/GHC/Hs/Expr.hs - compiler/GHC/Hs/Syn/Type.hs - compiler/GHC/Hs/Utils.hs - compiler/GHC/HsToCore/Binds.hs - 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