Ben Gamari pushed to branch wip/backports-9.14 at Glasgow Haskell Compiler / GHC Commits: bdf66b51 by Simon Peyton Jones at 2025-08-15T06:26:00-04:00 Treat tuple dictionaries uniformly; don't unbox them See `Note [Do not unbox class dictionaries]` in DmdAnal.hs, sep (DNB1). This MR reverses the plan in #23398, which suggested a special case to unbox tuple dictionaries in worker/wrapper. But: - This was the cause of a pile of complexity in the specialiser (#26158) - Even with that complexity, specialision was still bad, very bad See https://gitlab.haskell.org/ghc/ghc/-/issues/19747#note_626297 And it's entirely unnecessary! Specialision works fine without unboxing tuple dictionaries. (cherry picked from commit ca7a9d421f602355822b674dd01fb48cd6291108) - - - - - 58d1744f by Simon Peyton Jones at 2025-08-15T06:27:36-04:00 Implement unary classes The big change is described exhaustively in Note [Unary class magic] in GHC.Core.TyCon Other changes * We never unbox class dictionaries in worker/wrapper. This has been true for some time now, but the logic is now centralised in functions in GHC.Core.Opt.WorkWrap.Utils, namely `canUnboxTyCon`, and `canUnboxArg` See Note [Do not unbox class dictionaries] in GHC.Core.Opt.WorkWrap.Utils. * Refactored the `notWorthFloating` logic in GHc.Core.Opt.SetLevels. I can't remember if I actually changed any behaviour here, but if so it's only in a corner cases. * Fixed a bug in `GHC.Core.TyCon.isEnumerationTyCon`, which was wrongly returning True for (##). * Remove redundant Role argument to `liftCoSubstWithEx`. It was always Representational. * I refactored evidence generation in the constraint solver: * Made GHC.Tc.Types.Evidence contain better abstactions for evidence generation. * I deleted the file `GHC.Tc.Types.EvTerm` and merged its (small) contents elsewhere. It wasn't paying its way. * Made evidence for implicit parameters go via a proper abstraction. * Fix inlineBoringOk; see (IB6) in Note [inlineBoringOk] This fixes a slowdown in `countdownEffectfulDynLocal` in the `effectful` library. Smaller things * Rename `isDataTyCon` to `isBoxedDataTyCon`. * GHC.Core.Corecion.liftCoSubstWithEx was only called with Representational role, so I baked that into the function and removed the argument. * Get rid of `GHC.Core.TyCon.tyConSingleAlgDataCon_maybe` in favour of calling `not isNewTyCon` at the call sites; more explicit. * Refatored `GHC.Core.TyCon.isInjectiveTyCon`; but I don't think I changed its behaviour * Moved `decomposeIPPred` to GHC.Core.Predicate Compile time performance changes: geo. mean +0.1% minimum -6.8% maximum +14.4% The +14% one is in T21839c, where it seems that a bit more inlining is taking place. That seems acceptable; and the average change is small Metric Decrease: LargeRecord T12227 T12707 T16577 T21839r T5642 Metric Increase: T15164 T21839c T3294 T5321FD T5321Fun WWRec (cherry picked from commit 9bd7fcc518111a1549c98720c222cdbabd32ed46) - - - - - 85 changed files: - compiler/GHC/Builtin/Types.hs - compiler/GHC/Core/Class.hs - compiler/GHC/Core/Coercion.hs - compiler/GHC/Core/DataCon.hs - compiler/GHC/Core/FamInstEnv.hs - compiler/GHC/Core/Opt/Arity.hs - compiler/GHC/Core/Opt/CprAnal.hs - compiler/GHC/Core/Opt/DmdAnal.hs - compiler/GHC/Core/Opt/OccurAnal.hs - compiler/GHC/Core/Opt/SetLevels.hs - compiler/GHC/Core/Opt/Specialise.hs - compiler/GHC/Core/Opt/WorkWrap/Utils.hs - compiler/GHC/Core/Predicate.hs - compiler/GHC/Core/TyCo/Rep.hs - compiler/GHC/Core/TyCon.hs - compiler/GHC/Core/Type.hs - compiler/GHC/Core/Unfold.hs - compiler/GHC/Core/Unfold/Make.hs - compiler/GHC/Core/Utils.hs - compiler/GHC/CoreToStg.hs - compiler/GHC/HsToCore/Binds.hs - compiler/GHC/HsToCore/Expr.hs - compiler/GHC/HsToCore/Foreign/Call.hs - compiler/GHC/Iface/Decl.hs - compiler/GHC/Iface/Syntax.hs - compiler/GHC/IfaceToCore.hs - compiler/GHC/Rename/Module.hs - compiler/GHC/StgToByteCode.hs - compiler/GHC/Tc/Errors.hs - compiler/GHC/Tc/Gen/Bind.hs - compiler/GHC/Tc/Gen/Expr.hs - compiler/GHC/Tc/Instance/Class.hs - compiler/GHC/Tc/Instance/Family.hs - compiler/GHC/Tc/Solver/Default.hs - compiler/GHC/Tc/Solver/Dict.hs - compiler/GHC/Tc/Solver/Equality.hs - compiler/GHC/Tc/Solver/Monad.hs - compiler/GHC/Tc/Solver/Solve.hs - compiler/GHC/Tc/TyCl.hs - compiler/GHC/Tc/TyCl/Build.hs - compiler/GHC/Tc/TyCl/Instance.hs - compiler/GHC/Tc/TyCl/PatSyn.hs - − compiler/GHC/Tc/Types/EvTerm.hs - compiler/GHC/Tc/Types/Evidence.hs - compiler/GHC/Tc/Utils/TcMType.hs - compiler/GHC/Types/Demand.hs - compiler/GHC/Types/Id.hs - compiler/GHC/Types/Id/Make.hs - compiler/GHC/Types/RepType.hs - compiler/ghc.cabal.in - testsuite/tests/core-to-stg/T24124.stderr - testsuite/tests/deSugar/should_compile/T2431.stderr - testsuite/tests/dmdanal/should_compile/T16029.stdout - testsuite/tests/dmdanal/should_compile/T23398.hs - testsuite/tests/dmdanal/should_compile/T23398.stderr - testsuite/tests/dmdanal/sigs/T21119.stderr - testsuite/tests/dmdanal/sigs/T21888.stderr - testsuite/tests/ghci.debugger/scripts/break011.stdout - testsuite/tests/ghci.debugger/scripts/break024.stdout - testsuite/tests/indexed-types/should_compile/T2238.hs - testsuite/tests/numeric/should_compile/T15547.stderr - testsuite/tests/numeric/should_compile/T23907.stderr - testsuite/tests/roles/should_compile/Roles14.stderr - testsuite/tests/roles/should_compile/Roles3.stderr - testsuite/tests/roles/should_compile/Roles4.stderr - testsuite/tests/simplCore/should_compile/DataToTagFamilyScrut.stderr - testsuite/tests/simplCore/should_compile/T15205.stderr - testsuite/tests/simplCore/should_compile/T17366.stderr - testsuite/tests/simplCore/should_compile/T17966.stderr - testsuite/tests/simplCore/should_compile/T22309.stderr - testsuite/tests/simplCore/should_compile/T22375DataFamily.stderr - testsuite/tests/simplCore/should_compile/T23307.stderr - testsuite/tests/simplCore/should_compile/T23307a.stderr - testsuite/tests/simplCore/should_compile/T25389.stderr - testsuite/tests/simplCore/should_compile/T25713.stderr - testsuite/tests/simplCore/should_compile/T7360.stderr - testsuite/tests/simplStg/should_compile/T15226b.stderr - testsuite/tests/tcplugins/CtIdPlugin.hs - testsuite/tests/typecheck/should_compile/Makefile - testsuite/tests/typecheck/should_compile/T12763.stderr - testsuite/tests/typecheck/should_compile/T14774.stdout - testsuite/tests/typecheck/should_compile/T18406b.stderr - testsuite/tests/typecheck/should_compile/T18529.stderr - testsuite/tests/typecheck/should_compile/all.T - testsuite/tests/unboxedsums/unpack_sums_7.stdout The diff was not included because it is too large. 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