Simon Peyton Jones pushed to branch wip/case-bndr-unf at Glasgow Haskell Compiler / GHC Commits: ac870ad5 by Simon Jakobi at 2026-10-28T04:40:42-04:00 X86 NCG: use 32-bit POPCNT for sub-word popcounts A 32-bit write zero-extends the result to the full register, so we don't need to emit additional code for this. We also skip emitting zero-extension instructions for the argument when it is already visibly zero-extended. For the byte-wise popcount loop from #24813, this shrinks the popcount sequence from 5 instructions to 3. Assisted-by: Claude Fable 5.1 - - - - - 53087373 by Facundo Domínguez at 2026-10-28T04:41:32-04:00 Use a ShortByteString in Serialized instead of [Word8] This makes the in-memory representation 40x more compact for all values stored in annotations. A test is added to measure the representation size of annotations specified in the compiler input. The GHC API is modified. All functions that previously handled annotations in [Word8] form now use ShortByteString. The following definitions have modified types: * GHC.findGlobalAnns * GHC.Tc.Gen.Splice.getAnnotationsByTypeRep * GHC.Core.Opt.Monad.getAnnotations * GHC.Core.Opt.Monad.getFirstAnnotations * GHC.Types.Annotations.deserializeAnns * GHC.Types.Annotations.findAnns * GHC.Types.Annotations.findAnnsByTypeRep * GHC.Serialized.Serialized * GHC.Serialized.toSerialized * GHC.Serialized.fromSerialized * GHC.Serialized.serializeWithData * GHC.Serialized.deserializeWithData * GHCi.Message.ReifyAnnotations Fixes #28002. - - - - - cc533b66 by Sasha Bogicevic at 2026-10-31T09:18:15-04:00 Don't report -XStrict-generated bangs under -Wredundant-bang-patterns The -XStrict flag causes the desugarer to insert bang patterns. These are not user-written, so -Wredundant-bang-patterns must not report them. To achieve this, the desugarer now tracks whether it is desugaring compiler-generated code (similar to the typechecker's 'tcl_in_gen_code'). Bangs inserted by -XStrict are given generated spans, which suppresses the "redundant bang" warnings without otherwise affecting pattern-match warnings. Fixes #27323 - - - - - 13d38047 by Luite Stegeman at 2026-10-31T09:19:11-04:00 rts: tombstone Weak# copies that lose an evacuation race (#23160) Mark the losing copy of a Weak# during an evacuation race in parallel GC with stg_DEAD_WEAK_info. This ensures that the nonmoving GC doesn't follow dangling pointers, leading to crashes. Fixes #23160 - - - - - 63347328 by Zubin Duggal at 2026-10-31T09:19:52-04:00 ghci: Drop GHCi's exception context when rethrowing in ghc -e Fixes #27847. - - - - - a85fef3f by Zubin Duggal at 2026-10-31T09:19:52-04:00 base: Preserve exception context in modifyIOError Fixes #27851. CLC proposal: https://github.com/haskell/core-libraries-committee/issues/446 - - - - - 1d60b591 by Zubin Duggal at 2026-10-31T09:19:52-04:00 base: Preserve exception context in mapException Fixes #27851. CLC proposal: https://github.com/haskell/core-libraries-committee/issues/446 - - - - - 3c029a1b by Zubin Duggal at 2026-10-31T09:19:52-04:00 base: Preserve exception context when rethrowing exceptions in Handle reads Fixes #27875. CLC proposal: https://github.com/haskell/core-libraries-committee/issues/447 - - - - - ab2b317a by Zubin Duggal at 2026-10-31T09:19:52-04:00 base: Preserve exception context when rethrowing exceptions in hClose Fixes #27875. CLC proposal: https://github.com/haskell/core-libraries-committee/issues/447 - - - - - f5abf277 by Zubin Duggal at 2026-10-31T09:19:52-04:00 base: Preserve exception context when rethrowing exceptions in Windows openFile Fixes #27875. CLC proposal: https://github.com/haskell/core-libraries-committee/issues/447 - - - - - d842c672 by Zubin Duggal at 2026-10-31T09:19:52-04:00 base: Preserve exception context when rethrowing exceptions in executablePath Fixes #27875. CLC proposal: https://github.com/haskell/core-libraries-committee/issues/447 - - - - - c5a8bb9f by Simon Peyton Jones at 2026-10-31T09:20:34-04:00 Simplify a tc-trace which could crash the compiler The trace formatted an error message, which prematurely read the ExpType in a FunResCtxt. Solution: don't put call the error message formatting when tc-tracing. - - - - - ab49b1d2 by Simon Peyton Jones at 2026-10-31T09:20:34-04:00 Tiny comment change to uniqAway - - - - - 6efe4ba3 by Simon Peyton Jones at 2026-10-31T09:20:34-04:00 Make niFixSubst idempotent I discovered (when fixing #27994) that `niFixSubst` didn't actually generate an idempotent subsitution despite its claims. It could return a substitution that mentions domain variables on in its range, when those variables are hidden inside the kind of a type variable occurrence. As a result it can generate ill-kinded types. Boo! The fix is simple, and uses deep substitution. See Note [Finding the substitution fixpoint] I don't think it actually /caused/ any bugs, so there is no regression test. - - - - - 3b60ae7e by Simon Peyton Jones at 2026-10-31T09:20:34-04:00 Fix a nasty bug in fundeps This MR fixes #27994, which turned out to be very tricky. See Note [Exploiting closed type famililes], especially (CF7). I was ending up with TyVars (not TcTyVars) in the solver, because the substitution computed in `getRelevantBranches` mixed the two. The code was just too clever. I ended up simplifying it quite a bit. For /closed/ families we no longer call `trimQtvs` (was `trim_qtvs`). Open families still do use `trimQtvs`. See Note [trimQTvs] This patch also fixes one other buglet in the same code. * Over-saturated type families were being mis-handled. See the new use of `saturatedFamApp_maybe`. - - - - - e4610f2d by Facundo Domínguez at 2026-10-31T09:21:24-04:00 Have haddock --incremental look for the module in -this-unit-id - - - - - bc6c0db6 by sheaf at 2026-10-31T09:22:20-04:00 mightBeFunTy: hotfix for #27979 ce01ccb6 refactored 'GHC.Types.RepType.mightBeFunTy' to look through unary classes. That change introduced the helper function 'unwrap_type' which was supposed to always return an unwrapped type, but its fallback equation mistakenly returned the original type. This caused the subsequent 'tyConAppTyCon_maybe' to fail in cases where it should succeed (e.g. looking through foralls). In this commit, we move all the unary class unwrapping logic into 'unwrapType' where it belonged from the start, and update the documentation of 'unwrapType' to better explain what it should be used for (#26695). Fixes #27979 #26695 ------------------------- Metric Increase: T5642 ------------------------- - - - - - 233cce46 by Alan Zimmerman at 2026-10-31T09:23:01-04:00 EPA: Tidy up ExactPrint.markAnnListA' It takes an action which can modify the AnnList, but this is never used. So remove it. - - - - - 3594a908 by Sylvain Henry at 2026-10-31T09:23:51-04:00 gitmodules: ignore dirty libffi-clib submodule (#26785) `./boot` runs autoreconf in libraries/libffi-clib, which leaves `configure~` behind and rewrites the tracked `aclocal.m4` whenever the local automake version differs from the one that generated it. Every checkout then looks dirty. Ignore working-tree changes in the submodule (`ignore = dirty`); a changed submodule commit is still reported. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com> - - - - - 341223c0 by Rodrigo Mesquita at 2026-10-31T09:24:33-04:00 refactor: Keep the interactive Ids directly rather than Name Removes things like names <- map idName ids map (\i -> let id = find (\x -> i==idName x) names) idso and is more straightforward because there's less state going around (no more updating HscEnv as an output) It also kills `printTypeOfNames` completely, since now we just have the Ids. No longer `lookupName` names to get back the ids... ``` printTypeOfName :: GHC.GhcMonad m => Name -> m () printTypeOfName n = do maybe_tything <- GHC.lookupName n case maybe_tything of Nothing -> return () Just thing -> printTyThing thing ``` now is just `printTyThing . AnId` Also: ```diff - tythings <- catMaybes `liftM` mapM GHC.lookupName namesSorted - docs <- mapM pprTypeAndContents [i | AnId i <- tythings] + docs <- mapM pprTypeAndContents idsSorted ``` (and yes, in ExecBreaks there are only Ids, no TyThings, bc they are only constructed by the interpreter execution which can only bind ids. for TyThings use runDecls which doesn't return execBreaks.) There's some care to be had to make sure we use the "most refined" Ids, whereas when using `Name`s we'd always fetch the most refined Id from scratch. Fixes #28052 - - - - - 3fa06e36 by Simon Peyton Jones at 2026-11-02T23:38:38+00:00 Make pushCast pure, and move it to Simplify.Utils pushCast and pushCastMCo were in the SimplM monad, but no longer do anything monadic. (Historically, pushing a coercion into an argument used to simplify that argument; but now the coercion is recorded in the sc_cast field of ApplyToVal.) This patch makes them pure functions, and moves them, together with addCastMCo, optOutCoercion and Note [The sc_cast field of ApplyToVal], from GHC.Core.Opt.Simplify.Iteration to GHC.Core.Opt.Simplify.Utils, alongside the SimplCont type they manipulate. No change in behaviour. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> - - - - - 98c43ef5 by Simon Peyton Jones at 2026-11-02T23:38:38+00:00 Lambda and case binders have vanilla IdInfo (#27965) Lambda binders, case binders, and case-alternative binders should never have RULES, a (non-default) inline pragma, or a stable unfolding. See new Note [Core binder IdInfo invariants] in GHC.Core, which lays out the invariants. This patch * Makes Core Lint check the invariant, using the new predicate GHC.Types.Id.lamBndrInfoOK. * Fixes the desugarer, which violated it. For a strict binding let !x = rhs in body we generate let x = rhs in case x of x { DEFAULT -> body } re-using x (shadowed) as the case binder; see Note [Desugar Strict binds]. But the case binder inherited x's IdInfo, including, say, a NOINLINE pragma (e.g. `res1` in GHC.Internal.Control.Monad.ST.Lazy.Imp). Now GHC.HsToCore.Utils.seqVar gives the case binder vanilla IdInfo. This was not just a matter of taste. For example h fm s = let {-# NOINLINE res1 #-} !res1 = fm s !(f, s') = res1 in (f+1, s') The NOINLINE case binder becomes a NOINLINE alias `let res3 = res2`, which is never inlined, and survives (as a silly join point) into the final code. * Fixes the Simplifier, which could violate it when duplicating a StrictBind continuation, which makes a join point let x = <> in b ==> join j x = b in j <> If x has such IdInfo, we now use a fresh binder for the join point let x = <> in b ==> join j x' = let x = x' in b in j <> See (DSB1) in Note [Duplicating StrictBind]. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> - - - - - b51b00b4 by Simon Peyton Jones at 2026-11-02T23:38:38+00:00 Add varIsHNF, and use it in move_transit_vars `varIsHNF v` is the same as `exprIsHNF (Var v)`, but avoids building the Var only to take it apart. The (Var v) case of exprIsHNFlike now uses the shared varIsHNFlike, so the two cannot drift apart. In GHC.Core.Opt.WorkWrap.Utils.move_transit_vars we had the guard isUnliftedType var_ty || exprIsHNF (Var var) but exprIsHNF is already True of variables of (definitely) unlifted type, so the isUnliftedType test was redundant. Now it is just (varIsHNF var). No change in behaviour. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> - - - - - 8626d2d8 by Simon Peyton Jones at 2026-11-02T23:38:38+00:00 Use SimplClo for the argument of ApplyToVal This patch renames SimplSR to SimplClo (a "closure"), and uses it not only as the range of the Simplifier's substitution, but also as the argument of an ApplyToVal continuation. ApplyToVal used to have three fields sc_env :: StaticEnv sc_arg :: CoreExpr sc_cast :: MOutCoercion but now has just sc_dup :: DupFlag sc_arg :: SimplClo An un-simplified argument is (ContEx env arg mco), and an already-simplified one is (DoneEx arg _). See Note [The argument of ApplyToVal] in GHC.Core.Opt.Simplify.Utils. The main payoff is that, since the substitution maps an Id to a SimplClo, beta-reduction can substitute the argument for the lambda binder without further ado. Accordingly, preInlineUnconditionally is split into * preInlineLetUnconditionally, for let-bindings * preInlineBetaUnconditionally, for beta-redexes, which takes a SimplClo The latter omits some checks that cannot fire for lambda binders. Other notes * The new (ContEx env arg mco) form makes it easy to push a cast into an argument (mkCloCastMCo), whether or not it has been simplified. See Note [The MOutCoercion field of ContEx]. * `preInlineUnconditionally` gets split into two variants, one for let-bindings and one for beta-reduction (which takes a `SimplClo`). There is a little bit of duplication here, but not much. * Fixes #27962. The simplifier was previously dropping a cast when dealing with runRW#. The new `SimplClo` makes that bug much harder to allow. * Fixes #27963. contOutArgs, which supplies the arguments for Plan (BEFORE) rule matching, ignored the sc_cast field of ApplyToVal. So in (f |> co) n ==> f (n |> co1) -- co1 in sc_cast a rule for `f` saw `f n` rather than `f (n |> co1)`, and failed to match (the rule matcher checks the types of template variables). If f's unfolding is active, f may then be inlined, and the rule is lost for good. Now contOutArgs uses simplCloExpr, which includes the pending cast. Almost no change in behaviour, except for the #27963 bug-fix. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> - - - - - 8b5817c4 by Simon Peyton Jones at 2026-11-03T08:13:27+00:00 wibble Iteration.hs [skip ci] - - - - - 123 changed files: - .gitmodules - + changelog.d/T27323 - + changelog.d/T27847 - + changelog.d/T27962 - + changelog.d/T27963 - + changelog.d/T27979 - + changelog.d/T27994 - + changelog.d/T28002 - + changelog.d/T28002-api - + changelog.d/clc-446 - + changelog.d/clc-447 - + changelog.d/fix-nonmoving-weak-evacuation-race-23160 - + changelog.d/ghc-api-interactive-ids - + changelog.d/ncg-x86-subword-popcnt - compiler/GHC.hs - compiler/GHC/CmmToAsm/X86/CodeGen.hs - compiler/GHC/Core.hs - compiler/GHC/Core/Coercion/Axiom.hs - compiler/GHC/Core/Lint.hs - compiler/GHC/Core/Opt/Monad.hs - compiler/GHC/Core/Opt/Simplify/Env.hs - compiler/GHC/Core/Opt/Simplify/Iteration.hs - compiler/GHC/Core/Opt/Simplify/Utils.hs - compiler/GHC/Core/Opt/SpecConstr.hs - compiler/GHC/Core/Opt/WorkWrap/Utils.hs - compiler/GHC/Core/Ppr.hs - compiler/GHC/Core/Predicate.hs - compiler/GHC/Core/TyCo/FVs.hs - compiler/GHC/Core/TyCo/Subst.hs - compiler/GHC/Core/Type.hs - compiler/GHC/Core/Unify.hs - compiler/GHC/Core/Utils.hs - compiler/GHC/HsToCore/Match.hs - compiler/GHC/HsToCore/Match/Literal.hs - compiler/GHC/HsToCore/Monad.hs - compiler/GHC/HsToCore/Pmc.hs - compiler/GHC/HsToCore/Pmc/Desugar.hs - compiler/GHC/HsToCore/Types.hs - compiler/GHC/HsToCore/Utils.hs - compiler/GHC/Runtime/Context.hs - compiler/GHC/Runtime/Debugger.hs - compiler/GHC/Runtime/Eval.hs - compiler/GHC/Runtime/Eval/Types.hs - compiler/GHC/Runtime/Heap/Inspect.hs - compiler/GHC/Tc/Gen/Splice.hs - compiler/GHC/Tc/Instance/Family.hs - compiler/GHC/Tc/Solver/FunDeps.hs - compiler/GHC/Tc/Utils/Unify.hs - compiler/GHC/Types/Annotations.hs - compiler/GHC/Types/Id.hs - compiler/GHC/Types/RepType.hs - compiler/GHC/Types/Var/Env.hs - compiler/GHC/Utils/Outputable.hs - ghc/GHCi/UI.hs - ghc/GHCi/UI/Monad.hs - libraries/base/changelog.md - libraries/ghc-boot/GHC/Serialized.hs - libraries/ghc-internal/src/GHC/Internal/Control/Exception/Base.hs - libraries/ghc-internal/src/GHC/Internal/IO/Handle/Internals.hs - libraries/ghc-internal/src/GHC/Internal/IO/Handle/Text.hs - libraries/ghc-internal/src/GHC/Internal/IO/Handle/Windows.hs - libraries/ghc-internal/src/GHC/Internal/System/Environment/ExecutablePath.hsc - libraries/ghc-internal/src/GHC/Internal/System/IO/Error.hs - libraries/ghci/GHCi/Message.hs - libraries/ghci/GHCi/TH.hs - libraries/ghci/GHCi/TH/Binary.hs - rts/sm/Evac.c - testsuite/tests/annotations/should_run/Makefile - + testsuite/tests/annotations/should_run/T16841.hs - + testsuite/tests/annotations/should_run/T16841.stdout - testsuite/tests/annotations/should_run/all.T - + testsuite/tests/codeGen/should_compile/T27979.hs - + testsuite/tests/codeGen/should_compile/T27979.stderr - testsuite/tests/codeGen/should_compile/all.T - + testsuite/tests/codeGen/should_gen_asm/T24813.asm - + testsuite/tests/codeGen/should_gen_asm/T24813.cmm - testsuite/tests/codeGen/should_gen_asm/all.T - testsuite/tests/count-deps/CountDepsParser.stdout - + testsuite/tests/exceptions/T27851.hs - + testsuite/tests/exceptions/T27851.stderr - + testsuite/tests/exceptions/T27851b.hs - + testsuite/tests/exceptions/T27851b.stderr - + testsuite/tests/exceptions/T27851c.hs - + testsuite/tests/exceptions/T27851c.stdout - + testsuite/tests/exceptions/T27851d.hs - + testsuite/tests/exceptions/T27851d.stdout - + testsuite/tests/exceptions/T27851d.stdout-javascript-unknown-ghcjs - testsuite/tests/exceptions/all.T - testsuite/tests/ghc-e/should_fail/T18441fail7.stderr - testsuite/tests/ghc-e/should_run/ghc-e005.stderr - + testsuite/tests/ghci.debugger/scripts/RttiSharedTyVar.hs - + testsuite/tests/ghci.debugger/scripts/RttiSharedTyVar.script - + testsuite/tests/ghci.debugger/scripts/RttiSharedTyVar.stdout - testsuite/tests/ghci.debugger/scripts/all.T - + testsuite/tests/haddock/haddock_testsuite/IncrementalUnitId.hs - testsuite/tests/haddock/haddock_testsuite/Makefile - testsuite/tests/haddock/haddock_testsuite/all.T - + testsuite/tests/haddock/haddock_testsuite/haddockIncrementalUnitId.stdout - testsuite/tests/plugins/T26761Plugin.hs - testsuite/tests/plugins/all.T - + testsuite/tests/pmcheck/should_compile/T27323.hs - + testsuite/tests/pmcheck/should_compile/T27323b.hs - testsuite/tests/pmcheck/should_compile/all.T - + testsuite/tests/rts/T23160.hs - + testsuite/tests/rts/T23160.stdout - testsuite/tests/rts/all.T - testsuite/tests/simplCore/should_compile/T15445.stderr - + testsuite/tests/simplCore/should_compile/T27962.hs - + testsuite/tests/simplCore/should_compile/T27963.hs - + testsuite/tests/simplCore/should_compile/T27963.stderr - + testsuite/tests/simplCore/should_compile/T27965.hs - testsuite/tests/simplCore/should_compile/all.T - + testsuite/tests/typecheck/should_compile/T27994.hs - + testsuite/tests/typecheck/should_compile/T27994a.hs - + testsuite/tests/typecheck/should_compile/T27994b.hs - testsuite/tests/typecheck/should_compile/all.T - testsuite/tests/warnings/should_compile/Overflow.stderr-ws-32 - testsuite/tests/warnings/should_compile/Overflow.stderr-ws-64 - testsuite/tests/warnings/should_compile/T13256.stderr-ws-32 - testsuite/tests/warnings/should_compile/T13256.stderr-ws-64 - utils/check-exact/ExactPrint.hs - utils/haddock/CHANGES.md - utils/haddock/haddock-api/src/Haddock/Interface.hs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/24d1ab3bb660abb34da658f76098323... -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/24d1ab3bb660abb34da658f76098323... 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