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* Major refactor in the handling of equality constraintsSimon Peyton Jones2023-04-141-1/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This MR substantially refactors the way in which the constraint solver deals with equality constraints. The big thing is: * Intead of a pipeline in which we /first/ canonicalise and /then/ interact (the latter including performing unification) the two steps are more closely integreated into one. That avoids the current rather indirect communication between the two steps. The proximate cause for this refactoring is fixing #22194, which involve solving [W] alpha[2] ~ Maybe (F beta[4]) by doing this: alpha[2] := Maybe delta[2] [W] delta[2] ~ F beta[4] That is, we don't promote beta[4]! This is very like introducing a cycle breaker, and was very awkward to do before, but now it is all nice. See GHC.Tc.Utils.Unify Note [Promotion and level-checking] and Note [Family applications in canonical constraints]. The big change is this: * Several canonicalisation checks (occurs-check, cycle-breaking, checking for concreteness) are combined into one new function: GHC.Tc.Utils.Unify.checkTyEqRhs This function is controlled by `TyEqFlags`, which says what to do for foralls, type families etc. * `canEqCanLHSFinish` now sees if unification is possible, and if so, actually does it: see `canEqCanLHSFinish_try_unification`. There are loads of smaller changes: * The on-the-fly unifier `GHC.Tc.Utils.Unify.unifyType` has a cheap-and-cheerful version of `checkTyEqRhs`, called `simpleUnifyCheck`. If `simpleUnifyCheck` succeeds, it can unify, otherwise it defers by emitting a constraint. This is simpler than before. * I simplified the swapping code in `GHC.Tc.Solver.Equality.canEqCanLHS`. Especially the nasty stuff involving `swap_for_occurs` and `canEqTyVarFunEq`. Much nicer now. See Note [Orienting TyVarLHS/TyFamLHS] Note [Orienting TyFamLHS/TyFamLHS] * Added `cteSkolemOccurs`, `cteConcrete`, and `cteCoercionHole` to the problems that can be discovered by `checkTyEqRhs`. * I fixed #23199 `pickQuantifiablePreds`, which actually allows GHC to to accept both cases in #22194 rather than rejecting both. Yet smaller: * Added a `synIsConcrete` flag to `SynonymTyCon` (alongside `synIsFamFree`) to reduce the need for synonym expansion when checking concreteness. Use it in `isConcreteType`. * Renamed `isConcrete` to `isConcreteType` * Defined `GHC.Core.TyCo.FVs.isInjectiveInType` as a more efficient way to find if a particular type variable is used injectively than finding all the injective variables. It is called in `GHC.Tc.Utils.Unify.definitely_poly`, which in turn is used quite a lot. * Moved `rewriterView` to `GHC.Core.Type`, so we can use it from the constraint solver. Fixes #22194, #23199 Compile times decrease by an average of 0.1%; but there is a 7.4% drop in compiler allocation on T15703. Metric Decrease: T15703
* Type vs Constraint: finally nailedSimon Peyton Jones2022-11-111-4/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This big patch addresses the rats-nest of issues that have plagued us for years, about the relationship between Type and Constraint. See #11715/#21623. The main payload of the patch is: * To introduce CONSTRAINT :: RuntimeRep -> Type * To make TYPE and CONSTRAINT distinct throughout the compiler Two overview Notes in GHC.Builtin.Types.Prim * Note [TYPE and CONSTRAINT] * Note [Type and Constraint are not apart] This is the main complication. The specifics * New primitive types (GHC.Builtin.Types.Prim) - CONSTRAINT - ctArrowTyCon (=>) - tcArrowTyCon (-=>) - ccArrowTyCon (==>) - funTyCon FUN -- Not new See Note [Function type constructors and FunTy] and Note [TYPE and CONSTRAINT] * GHC.Builtin.Types: - New type Constraint = CONSTRAINT LiftedRep - I also stopped nonEmptyTyCon being built-in; it only needs to be wired-in * Exploit the fact that Type and Constraint are distinct throughout GHC - Get rid of tcView in favour of coreView. - Many tcXX functions become XX functions. e.g. tcGetCastedTyVar --> getCastedTyVar * Kill off Note [ForAllTy and typechecker equality], in (old) GHC.Tc.Solver.Canonical. It said that typechecker-equality should ignore the specified/inferred distinction when comparein two ForAllTys. But that wsa only weakly supported and (worse) implies that we need a separate typechecker equality, different from core equality. No no no. * GHC.Core.TyCon: kill off FunTyCon in data TyCon. There was no need for it, and anyway now we have four of them! * GHC.Core.TyCo.Rep: add two FunTyFlags to FunCo See Note [FunCo] in that module. * GHC.Core.Type. Lots and lots of changes driven by adding CONSTRAINT. The key new function is sORTKind_maybe; most other changes are built on top of that. See also `funTyConAppTy_maybe` and `tyConAppFun_maybe`. * Fix a longstanding bug in GHC.Core.Type.typeKind, and Core Lint, in kinding ForAllTys. See new tules (FORALL1) and (FORALL2) in GHC.Core.Type. (The bug was that before (forall (cv::t1 ~# t2). blah), where blah::TYPE IntRep, would get kind (TYPE IntRep), but it should be (TYPE LiftedRep). See Note [Kinding rules for types] in GHC.Core.Type. * GHC.Core.TyCo.Compare is a new module in which we do eqType and cmpType. Of course, no tcEqType any more. * GHC.Core.TyCo.FVs. I moved some free-var-like function into this module: tyConsOfType, visVarsOfType, and occCheckExpand. Refactoring only. * GHC.Builtin.Types. Compiletely re-engineer boxingDataCon_maybe to have one for each /RuntimeRep/, rather than one for each /Type/. This dramatically widens the range of types we can auto-box. See Note [Boxing constructors] in GHC.Builtin.Types The boxing types themselves are declared in library ghc-prim:GHC.Types. GHC.Core.Make. Re-engineer the treatment of "big" tuples (mkBigCoreVarTup etc) GHC.Core.Make, so that it auto-boxes unboxed values and (crucially) types of kind Constraint. That allows the desugaring for arrows to work; it gathers up free variables (including dictionaries) into tuples. See Note [Big tuples] in GHC.Core.Make. There is still work to do here: #22336. But things are better than before. * GHC.Core.Make. We need two absent-error Ids, aBSENT_ERROR_ID for types of kind Type, and aBSENT_CONSTRAINT_ERROR_ID for vaues of kind Constraint. Ditto noInlineId vs noInlieConstraintId in GHC.Types.Id.Make; see Note [inlineId magic]. * GHC.Core.TyCo.Rep. Completely refactor the NthCo coercion. It is now called SelCo, and its fields are much more descriptive than the single Int we used to have. A great improvement. See Note [SelCo] in GHC.Core.TyCo.Rep. * GHC.Core.RoughMap.roughMatchTyConName. Collapse TYPE and CONSTRAINT to a single TyCon, so that the rough-map does not distinguish them. * GHC.Core.DataCon - Mainly just improve documentation * Some significant renamings: GHC.Core.Multiplicity: Many --> ManyTy (easier to grep for) One --> OneTy GHC.Core.TyCo.Rep TyCoBinder --> GHC.Core.Var.PiTyBinder GHC.Core.Var TyCoVarBinder --> ForAllTyBinder AnonArgFlag --> FunTyFlag ArgFlag --> ForAllTyFlag GHC.Core.TyCon TyConTyCoBinder --> TyConPiTyBinder Many functions are renamed in consequence e.g. isinvisibleArgFlag becomes isInvisibleForAllTyFlag, etc * I refactored FunTyFlag (was AnonArgFlag) into a simple, flat data type data FunTyFlag = FTF_T_T -- (->) Type -> Type | FTF_T_C -- (-=>) Type -> Constraint | FTF_C_T -- (=>) Constraint -> Type | FTF_C_C -- (==>) Constraint -> Constraint * GHC.Tc.Errors.Ppr. Some significant refactoring in the TypeEqMisMatch case of pprMismatchMsg. * I made the tyConUnique field of TyCon strict, because I saw code with lots of silly eval's. That revealed that GHC.Settings.Constants.mAX_SUM_SIZE can only be 63, because we pack the sum tag into a 6-bit field. (Lurking bug squashed.) Fixes * #21530 Updates haddock submodule slightly. Performance changes ~~~~~~~~~~~~~~~~~~~ I was worried that compile times would get worse, but after some careful profiling we are down to a geometric mean 0.1% increase in allocation (in perf/compiler). That seems fine. There is a big runtime improvement in T10359 Metric Decrease: LargeRecord MultiLayerModulesTH_OneShot T13386 T13719 Metric Increase: T8095
* Misc cleanupKrzysztof Gogolewski2022-05-161-2/+2
| | | | | | | | - Remove groupWithName (unused) - Use the RuntimeRepType synonym where possible - Replace getUniqueM + mkSysLocalOrCoVar with mkSysLocalOrCoVarM No functional changes.
* Levity-polymorphic arrays and mutable variablessheaf2022-01-261-0/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch makes the following types levity-polymorphic in their last argument: - Array# a, SmallArray# a, Weak# b, StablePtr# a, StableName# a - MutableArray# s a, SmallMutableArray# s a, MutVar# s a, TVar# s a, MVar# s a, IOPort# s a The corresponding primops are also made levity-polymorphic, e.g. `newArray#`, `readArray#`, `writeMutVar#`, `writeIOPort#`, etc. Additionally, exception handling functions such as `catch#`, `raise#`, `maskAsyncExceptions#`,... are made levity/representation-polymorphic. Now that Array# and MutableArray# also work with unlifted types, we can simply re-define ArrayArray# and MutableArrayArray# in terms of them. This means that ArrayArray# and MutableArrayArray# are no longer primitive types, but simply unlifted newtypes around Array# and MutableArrayArray#. This completes the implementation of the Pointer Rep proposal https://github.com/ghc-proposals/ghc-proposals/pull/203 Fixes #20911 ------------------------- Metric Increase: T12545 ------------------------- ------------------------- Metric Decrease: T12545 -------------------------
* Increase type sharingBen Gamari2021-11-171-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | Fixes #20541 by making mkTyConApp do more sharing of types. In particular, replace * BoxedRep Lifted ==> LiftedRep * BoxedRep Unlifted ==> UnliftedRep * TupleRep '[] ==> ZeroBitRep * TYPE ZeroBitRep ==> ZeroBitType In each case, the thing on the right is a type synonym for the thing on the left, declared in ghc-prim:GHC.Types. See Note [Using synonyms to compress types] in GHC.Core.Type. The synonyms for ZeroBitRep and ZeroBitType are new, but absolutely in the same spirit as the other ones. (These synonyms are mainly for internal use, though the programmer can use them too.) I also renamed GHC.Core.Ty.Rep.isVoidTy to isZeroBitTy, to be compatible with the "zero-bit" nomenclature above. See discussion on !6806. There is a tricky wrinkle: see GHC.Core.Types Note [Care using synonyms to compress types] Compiler allocation decreases by up to 0.8%.
* Don't default type variables in type familiessheaf2021-10-261-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | This patch removes the following defaulting of type variables in type and data families: - type variables of kind RuntimeRep defaulting to LiftedRep - type variables of kind Levity defaulting to Lifted - type variables of kind Multiplicity defaulting to Many It does this by passing "defaulting options" to the `defaultTyVars` function; when calling from `tcTyFamInstEqnGuts` or `tcDataFamInstHeader` we pass options that avoid defaulting. This avoids wildcards being defaulted, which caused type families to unexpectedly fail to reduce. Note that kind defaulting, applicable only with -XNoPolyKinds, is not changed by this patch. Fixes #17536 ------------------------- Metric Increase: T12227 -------------------------
* Implement BoxedRep proposalwip/boxed-repBen Gamari2021-03-071-0/+1
| | | | | | | | | | | | | | | | | | | | | | | This implements the BoxedRep proposal, refactoring the `RuntimeRep` hierarchy from: ```haskell data RuntimeRep = LiftedPtrRep | UnliftedPtrRep | ... ``` to ```haskell data RuntimeRep = BoxedRep Levity | ... data Levity = Lifted | Unlifted ``` Updates binary, haddock submodules. Closes #17526. Metric Increase: T12545
* Extend nullary TyConApp optimisation to all TyConsBen Gamari2021-02-181-0/+2
| | | | | | | | | | | See Note [Sharing nullary TyConApps] in GHC.Core.TyCon. Closes #19367. Metric Decrease: T9872a T9872b T9872c
* Various performance improvementsKrzysztof Gogolewski2020-06-171-4/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This implements several general performance improvements to GHC, to offset the effect of the linear types change. General optimisations: - Add a `coreFullView` function which iterates `coreView` on the head. This avoids making function recursive solely because the iterate `coreView` themselves. As a consequence, this functions can be inlined, and trigger case-of-known constructor (_e.g._ `kindRep_maybe`, `isLiftedRuntimeRep`, `isMultiplicityTy`, `getTyVar_maybe`, `splitAppTy_maybe`, `splitFunType_maybe`, `tyConAppTyCon_maybe`). The common pattern about all these functions is that they are almost always used as views, and immediately consumed by a case expression. This commit also mark them asx `INLINE`. - In `subst_ty` add a special case for nullary `TyConApp`, which avoid allocations altogether. - Use `mkTyConApp` in `subst_ty` for the general `TyConApp`. This required quite a bit of module shuffling. case. `myTyConApp` enforces crucial sharing, which was lost during substitution. See also !2952 . - Make `subst_ty` stricter. - In `eqType` (specifically, in `nonDetCmpType`), add a special case, tested first, for the very common case of nullary `TyConApp`. `nonDetCmpType` has been made `INLINE` otherwise it is actually a regression. This is similar to the optimisations in !2952. Linear-type specific optimisations: - Use `tyConAppTyCon_maybe` instead of the more complex `eqType` in the definition of the pattern synonyms `One` and `Many`. - Break the `hs-boot` cycles between `Multiplicity.hs` and `Type.hs`: `Multiplicity` now import `Type` normally, rather than from the `hs-boot`. This way `tyConAppTyCon_maybe` can inline properly in the `One` and `Many` pattern synonyms. - Make `updateIdTypeAndMult` strict in its type and multiplicity - The `scaleIdBy` gets a specialised definition rather than being an alias to `scaleVarBy` - `splitFunTy_maybe` is given the type `Type -> Maybe (Mult, Type, Type)` instead of `Type -> Maybe (Scaled Type, Type)` - Remove the `MultMul` pattern synonym in favour of a view `isMultMul` because pattern synonyms appear not to inline well. - in `eqType`, in a `FunTy`, compare multiplicities last: they are almost always both `Many`, so it helps failing faster. - Cache `manyDataConTy` in `mkTyConApp`, to make sure that all the instances of `TyConApp ManyDataConTy []` are physically the same. This commit has been authored by * Richard Eisenberg * Krzysztof Gogolewski * Arnaud Spiwack Metric Decrease: haddock.base T12227 T12545 T12990 T1969 T3064 T5030 T9872b Metric Increase: haddock.base haddock.Cabal haddock.compiler T12150 T12234 T12425 T12707 T13035 T13056 T15164 T16190 T18304 T1969 T3064 T3294 T5631 T5642 T5837 T6048 T9020 T9233 T9675 T9872a T9961 WWRec
* Linear types (#15981)Krzysztof Gogolewski2020-06-171-1/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This is the first step towards implementation of the linear types proposal (https://github.com/ghc-proposals/ghc-proposals/pull/111). It features * A language extension -XLinearTypes * Syntax for linear functions in the surface language * Linearity checking in Core Lint, enabled with -dlinear-core-lint * Core-to-core passes are mostly compatible with linearity * Fields in a data type can be linear or unrestricted; linear fields have multiplicity-polymorphic constructors. If -XLinearTypes is disabled, the GADT syntax defaults to linear fields The following items are not yet supported: * a # m -> b syntax (only prefix FUN is supported for now) * Full multiplicity inference (multiplicities are really only checked) * Decent linearity error messages * Linear let, where, and case expressions in the surface language (each of these currently introduce the unrestricted variant) * Multiplicity-parametric fields * Syntax for annotating lambda-bound or let-bound with a multiplicity * Syntax for non-linear/multiple-field-multiplicity records * Linear projections for records with a single linear field * Linear pattern synonyms * Multiplicity coercions (test LinearPolyType) A high-level description can be found at https://ghc.haskell.org/trac/ghc/wiki/LinearTypes/Implementation Following the link above you will find a description of the changes made to Core. This commit has been authored by * Richard Eisenberg * Krzysztof Gogolewski * Matthew Pickering * Arnaud Spiwack With contributions from: * Mark Barbone * Alexander Vershilov Updates haddock submodule.
* Modules: Utils and Data (#13009)Sylvain Henry2020-04-261-2/+2
| | | | | | | Update Haddock submodule Metric Increase: haddock.compiler
* Modules: Core (#13009)Sylvain Henry2020-03-161-0/+26
Update submodule: haddock