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* Add two tests for #17366Simon Peyton Jones2022-11-017-0/+116
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* Shrink test case for #22357Simon Peyton Jones2022-11-011-678/+12
| | | | | Ryan Scott offered a cut-down repro case (60 lines instead of more than 700 lines)
* Add accurate skolem info when quantifyingSimon Peyton Jones2022-11-015-2/+65
| | | | | | | Ticket #22379 revealed that skolemiseQuantifiedTyVar was dropping the passed-in skol_info on the floor when it encountered a SkolemTv. Bad! Several TyCons thereby share a single SkolemInfo on their binders, which lead to bogus error reports.
* ThToHs: fix overzealous parenthesizationVladislav Zavialov2022-11-016-3/+23
| | | | | | | | | | | | | | | | | | Before this patch, when converting from TH.Exp to LHsExpr GhcPs, the compiler inserted more parentheses than required: ((f a) (b + c)) d This was happening because the LHS of the function application was parenthesized as if it was the RHS. Now we use funPrec and appPrec appropriately and produce sensibly parenthesized expressions: f a (b + c) d I also took the opportunity to remove the special case for LamE, which was not special at all and simply duplicated code.
* Typo: rename -fwrite-if-simplfied-core to -fwrite-if-simplified-coreKrzysztof Gogolewski2022-11-011-9/+9
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* Add missing dict binds to specialiserSimon Peyton Jones2022-10-272-0/+728
| | | | | | | | | | I had forgotten to add the auxiliary dict bindings to the /unfolding/ of a specialised function. This caused #22358, which reports failures when compiling Hackage packages fixed-vector indexed-traversable Regression test T22357 is snarfed from indexed-traversable
* Use TcRnVDQInTermType in noNestedForallsContextsErr (#20115)Vladislav Zavialov2022-10-263-3/+3
| | | | | | | | | | | | | | | | | | | | | When faced with VDQ in the type of a term, GHC generates the following error message: Illegal visible, dependent quantification in the type of a term (GHC does not yet support this) Prior to this patch, there were two ways this message could have been generated and represented: 1. with the dedicated constructor TcRnVDQInTermType (see check_type in GHC.Tc.Validity) 2. with the transitional constructor TcRnUnknownMessage (see noNestedForallsContextsErr in GHC.Rename.Utils) Not only this led to duplication of code generating the final SDoc, it also made it tricky to track the origin of the error message. This patch fixes the problem by using TcRnVDQInTermType exclusively.
* Testsuite: more precise test optionsSylvain Henry2022-10-2646-160/+139
| | | | | Necessary for newer cross-compiling backends (JS, Wasm) that don't support TH yet.
* Introduce TcRnWithHsDocContext (#22346)Vladislav Zavialov2022-10-2631-77/+77
| | | | | | | | | | | | | | | | | Before this patch, GHC used withHsDocContext to attach an HsDocContext to an error message: addErr $ mkTcRnUnknownMessage $ mkPlainError noHints (withHsDocContext ctxt msg) The problem with this approach is that it only works with TcRnUnknownMessage. But could we attach an HsDocContext to a structured error message in a generic way? This patch solves the problem by introducing a new constructor to TcRnMessage: data TcRnMessage where ... TcRnWithHsDocContext :: !HsDocContext -> !TcRnMessage -> TcRnMessage ...
* Broaden the in-scope sets for liftEnvSubst and composeTCvSubstRyan Scott2022-10-262-0/+24
| | | | | | | | | | | | | | | | | This patch fixes two distinct (but closely related) buglets that were uncovered in #22235: * `liftEnvSubst` used an empty in-scope set, which was not wide enough to cover the variables in the range of the substitution. This patch fixes this by populating the in-scope set from the free variables in the range of the substitution. * `composeTCvSubst` applied the first substitution argument to the range of the second substitution argument, but the first substitution's in-scope set was not wide enough to cover the range of the second substutition. We similarly fix this issue in this patch by widening the first substitution's in-scope set before applying it. Fixes #22235.
* Make the specialiser handle polymorphic specialisationSimon Peyton Jones2022-10-253-11/+158
| | | | | | | | | | | | | | | | | | | | | | | | | | | Ticket #13873 unexpectedly showed that a SPECIALISE pragma made a program run (a lot) slower, because less specialisation took place overall. It turned out that the specialiser was missing opportunities because of quantified type variables. It was quite easy to fix. The story is given in Note [Specialising polymorphic dictionaries] Two other minor fixes in the specialiser * There is no benefit in specialising data constructor /wrappers/. (They can appear overloaded because they are given a dictionary to store in the constructor.) Small guard in canSpecImport. * There was a buglet in the UnspecArg case of specHeader, in the case where there is a dead binder. We need a LitRubbish filler for the specUnfolding stuff. I expanded Note [Drop dead args from specialisations] to explain. There is a 4% increase in compile time for T15164, because we generate more specialised code. This seems OK. Metric Increase: T15164
* Fix binder-swap bugSimon Peyton Jones2022-10-252-2/+0
| | | | | | | | | | | | | | | | | | | | | | | This patch fixes #21229 properly, by avoiding doing a binder-swap on dictionary Ids. This is pretty subtle, and explained in Note [Care with binder-swap on dictionaries]. Test is already in simplCore/should_run/T21229 This allows us to restore a feature to the specialiser that we had to revert: see Note [Specialising polymorphic dictionaries]. (This is done in a separate patch.) I also modularised things, using a new function scrutBinderSwap_maybe in all the places where we are (effectively) doing a binder-swap, notably * Simplify.Iteration.addAltUnfoldings * SpecConstr.extendCaseBndrs In Simplify.Iteration.addAltUnfoldings I also eliminated a guard Many <- idMult case_bndr because we concluded, in #22123, that it was doing no good.
* Convert Diagnostics in GHC.Tc.Gen.Splice (#20116)Aaron Allen2022-10-2451-54/+57
| | | | | | | Replaces uses of `TcRnUnknownMessage` in `GHC.Tc.Gen.Splice` with structured diagnostics. closes #20116
* Pin used way for test cloneMyStack (#21977)Sven Tennie2022-10-241-1/+5
| | | | | cloneMyStack checks the order of closures on the cloned stack. This may change for different ways. Thus we limit this test to one way (normal).
* Class layout info (#19623)Vladislav Zavialov2022-10-238-53/+123
| | | | Updates the haddock submodule.
* ci: Make fat014 test robustMatthew Pickering2022-10-202-4/+1
| | | | | | | | For some reason I implemented this as a makefile test rather than a ghci_script test. Hopefully making it a ghci_script test makes it more robust. Fixes #22313
* TyEq:N assertion: only for saturated applicationssheaf2022-10-192-0/+24
| | | | | | | | | | The assertion that checked TyEq:N in canEqCanLHSFinish incorrectly triggered in the case of an unsaturated newtype TyCon heading the RHS, even though we can't unwrap such an application. Now, we only trigger an assertion failure in case of a saturated application of a newtype TyCon. Fixes #22310
* Add SpliceTypes test for hie filesMatthew Pickering2022-10-193-0/+57
| | | | | | | This test checks that typed splices and quotes get the right type information when used in hiefiles. See #21619
* Disable some SIMD tests on non-X86 architecturessheaf2022-10-192-2/+4
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* Cmm Lint: relax SIMD register assignment checksheaf2022-10-191-2/+3
| | | | | | | | | | As noted in #22297, SIMD vector registers can be used to store different kinds of values, e.g. xmm1 can be used both to store integer and floating point values. The Cmm type system doesn't properly account for this, so we weaken the Cmm register assignment lint check to only compare widths when comparing a vector type with its allocated vector register.
* Remove SIMD conversionssheaf2022-10-193-0/+45
| | | | | | | | | | | This patch makes it so that packing/unpacking SIMD vectors always uses the right sized types, e.g. unpacking a Word16X4# will give a tuple of Word16#s. As a result, we can get rid of the conversion instructions that were previously required. Fixes #22296
* Add VecSlot for unboxed sums of SIMD vectorsDai2022-10-194-0/+63
| | | | | | | | | This patch adds the missing `VecRep` case to `primRepSlot` function and all the necessary machinery to carry this new `VecSlot` through code generation. This allows programs involving unboxed sums of SIMD vectors to be written and compiled. Fixes #22187
* Add -fsuppress-error-contexts to disable printing error contexts in errorswip/diagnostics-configMatthew Pickering2022-10-183-0/+12
| | | | | | | | | | | | | In many development environments, the source span is the primary means of seeing what an error message relates to, and the In the expression: and In an equation for: clauses are not particularly relevant. However, they can grow to be quite long, which can make the message itself both feel overwhelming and interact badly with limited-space areas. It's simple to implement this flag so we might as well do it and give the user control about how they see their messages. Fixes #21722
* Allow configuration of error message printingMatthew Pickering2022-10-182-3/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This MR implements the idea of #21731 that the printing of a diagnostic method should be configurable at the printing time. The interface of the `Diagnostic` class is modified from: ``` class Diagnostic a where diagnosticMessage :: a -> DecoratedSDoc diagnosticReason :: a -> DiagnosticReason diagnosticHints :: a -> [GhcHint] ``` to ``` class Diagnostic a where type DiagnosticOpts a defaultDiagnosticOpts :: DiagnosticOpts a diagnosticMessage :: DiagnosticOpts a -> a -> DecoratedSDoc diagnosticReason :: a -> DiagnosticReason diagnosticHints :: a -> [GhcHint] ``` and so each `Diagnostic` can implement their own configuration record which can then be supplied by a client in order to dictate how to print out the error message. At the moment this only allows us to implement #21722 nicely but in future it is more natural to separate the configuration of how much information we put into an error message and how much we decide to print out of it. Updates Haddock submodule
* Fix GHCis interaction with tag inference.Andreas Klebinger2022-10-187-4/+31
| | | | | | | | | | | | | | | | | | | | | | | | | I had assumed that wrappers were not inlined in interactive mode. Meaning we would always execute the compiled wrapper which properly takes care of upholding the strict field invariant. This turned out to be wrong. So instead we now run tag inference even when we generate bytecode. In that case only for correctness not performance reasons although it will be still beneficial for runtime in some cases. I further fixed a bug where GHCi didn't tag nullary constructors properly when used as arguments. Which caused segfaults when calling into compiled functions which expect the strict field invariant to be upheld. Fixes #22042 and #21083 ------------------------- Metric Increase: T4801 Metric Decrease: T13035 -------------------------
* Fix T15155l not getting -fllvmKrzysztof Gogolewski2022-10-171-1/+1
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* Testsuite: Add a new tables_next_to_code predicate.Andreas Klebinger2022-10-171-1/+4
| | | | | | And use it to avoid T21710a failing on non-tntc archs. Fixes #22169
* Update the check-exact infrastructure to match ghc-exactprintAlan Zimmerman2022-10-176-4/+20
| | | | | | | | | | | | | | | | | | | | GHC tests the exact print annotations using the contents of utils/check-exact. The same functionality is provided via https://github.com/alanz/ghc-exactprint The latter was updated to ensure it works with all of the files on hackage when 9.2 was released, as well as updated to ensure users of the library could work properly (apply-refact, retrie, etc). This commit brings the changes from ghc-exactprint into GHC/utils/check-exact, adapting for the changes to master. Once it lands, it will form the basis for the 9.4 version of ghc-exactprint. See also discussion around this process at #21355
* DmdAnal: Look through unfoldings of DataCon wrappers (#22241)Sebastian Graf2022-10-173-0/+56
| | | | | | | | | | | | | | | | | | Previously, the demand signature we computed upfront for a DataCon wrapper lacked boxity information and was much less precise than the demand transformer for the DataCon worker. In this patch we adopt the solution to look through unfoldings of DataCon wrappers during Demand Analysis, but still attach a demand signature for other passes such as the Simplifier. See `Note [DmdAnal for DataCon wrappers]` for more details. Fixes #22241.
* testsuite: Add test for #22282Ben Gamari2022-10-144-0/+24
| | | | | | This will complement mpickering's more general port of foundation's numerical testsuite, providing a test for the specific case found in #22282.
* Clearer error msg for newtype GADTs with defaulted kindFinley McIlwaine2022-10-1314-34/+53
| | | | | | | | | | | When a newtype introduces GADT eq_specs due to a defaulted RuntimeRep, we detect this and print the error message with explicit kinds. This also refactors newtype type checking to use the new diagnostic infra. Fixes #21447
* Add a perf test for the generics code pattern from #21839.Andreas Klebinger2022-10-136-0/+109
| | | | | | | | | This code showed a strong shift between compile time (got worse) and run time (got a lot better) recently which is perfectly acceptable. However it wasn't clear why the compile time regression was happening initially so I'm adding this test to make it easier to track such changes in the future.
* Unrestricted OverloadedLabels (#11671)Charles Taylor2022-10-123-0/+72
| | | | | Implements GHC proposal: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0170-unrestricted-overloadedlabels.rst
* Mark T7919 as fragileBryan Richter2022-10-121-3/+7
| | | | | | On x86_64-linux, T7919 timed out ~30 times during July 2022. And again ~30 times in September 2022.
* Separate IPE source file from spanBen Gamari2022-10-116-415/+106
| | | | | | The source file name can very often be shared across many IPE entries whereas the source coordinates are generally unique. Separate the two to exploit sharing of the former.
* Refactor IPE initializationBen Gamari2022-10-1114-381/+360
| | | | | | | | | | | | | | | Here we refactor the representation of info table provenance information in object code to significantly reduce its size and link-time impact. Specifically, we deduplicate strings and represent them as 32-bit offsets into a common string table. In addition, we rework the registration logic to eliminate allocation from the registration path, which is run from a static initializer where things like allocation are technically undefined behavior (although it did previously seem to work). For similar reasons we eliminate lock usage from registration path, instead relying on atomic CAS. Closes #22077.
* base: Move IPE helpers to GHC.InfoProvBen Gamari2022-10-112-2/+2
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* Don't keep exit join points so muchSimon Peyton Jones2022-10-115-27/+163
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | We were religiously keeping exit join points throughout, which had some bad effects (#21148, #22084). This MR does two things: * Arranges that exit join points are inhibited from inlining only in /one/ Simplifier pass (right after Exitification). See Note [Be selective about not-inlining exit join points] in GHC.Core.Opt.Exitify It's not a big deal, but it shaves 0.1% off compile times. * Inline used-once non-recursive join points very aggressively Given join j x = rhs in joinrec k y = ....j x.... where this is the only occurrence of `j`, we want to inline `j`. (Unless sm_keep_exits is on.) See Note [Inline used-once non-recursive join points] in GHC.Core.Opt.Simplify.Utils This is just a tidy-up really. It doesn't change allocation, but getting rid of a binding is always good. Very effect on nofib -- some up and down.
* Teach -fno-code about -fprefer-byte-codeMatthew Pickering2022-10-1113-22/+27
| | | | | | | | | | | | | | | | | This patch teachs the code generation logic of -fno-code about -fprefer-byte-code, so that if we need to generate code for a module which prefers byte code, then we generate byte code rather than object code. We keep track separately which modules need object code and which byte code and then enable the relevant code generation for each. Typically the option will be enabled globally so one of these sets should be empty and we will just turn on byte code or object code generation. We also fix the bug where we would generate code for a module which enables Template Haskell despite the fact it was unecessary. Fixes #22016
* Interface Files with Core DefinitionsMatthew Pickering2022-10-1131-4/+270
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This commit adds three new flags * -fwrite-if-simplified-core: Writes the whole core program into an interface file * -fbyte-code-and-object-code: Generate both byte code and object code when compiling a file * -fprefer-byte-code: Prefer to use byte-code if it's available when running TH splices. The goal for including the core bindings in an interface file is to be able to restart the compiler pipeline at the point just after simplification and before code generation. Once compilation is restarted then code can be created for the byte code backend. This can significantly speed up start-times for projects in GHCi. HLS already implements its own version of these extended interface files for this reason. Preferring to use byte-code means that we can avoid some potentially expensive code generation steps (see #21700) * Producing object code is much slower than producing bytecode, and normally you need to compile with `-dynamic-too` to produce code in the static and dynamic way, the dynamic way just for Template Haskell execution when using a dynamically linked compiler. * Linking many large object files, which happens once per splice, can be quite expensive compared to linking bytecode. And you can get GHC to compile the necessary byte code so `-fprefer-byte-code` has access to it by using `-fbyte-code-and-object-code`. Fixes #21067
* Tidy implicit bindsMatthew Pickering2022-10-114-10/+3
| | | | | We want to put implicit binds into fat interface files, so the easiest thing to do seems to be to treat them uniformly with other binders.
* Make rewrite rules "win" over inliningwip/T21851-rule-winSimon Peyton Jones2022-10-109-3/+124
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | If a rewrite rule and a rewrite rule compete in the simplifier, this patch makes sure that the rewrite rule "win". That is, in general a bit fragile, but it's a huge help when making specialisation work reliably, as #21851 and #22097 showed. The change is fairly straightforwad, and documented in Note [Rewrite rules and inlining] in GHC.Core.Opt.Simplify.Iteration. Compile-times change, up and down a bit -- in some cases because we get better specialisation. But the payoff (more reliable specialisation) is large. Metrics: compile_time/bytes allocated ----------------------------------------------- T10421(normal) +3.7% BAD T10421a(normal) +5.5% T13253(normal) +1.3% T14052(ghci) +1.8% T15304(normal) -1.4% T16577(normal) +3.1% BAD T17516(normal) +2.3% T17836(normal) -1.9% T18223(normal) -1.8% T8095(normal) -1.3% T9961(normal) +2.5% BAD geo. mean +0.0% minimum -1.9% maximum +5.5% Nofib results are (bytes allocated) +-------------------------------++----------+ | ||tsv (rel) | +===============================++==========+ | imaginary/paraffins || +0.27% | | imaginary/rfib || -0.04% | | real/anna || +0.02% | | real/fem || -0.04% | | real/fluid || +1.68% | | real/gamteb || -0.34% | | real/gg || +1.54% | | real/hidden || -0.01% | | real/hpg || -0.03% | | real/infer || -0.03% | | real/prolog || +0.02% | | real/veritas || -0.47% | | shootout/fannkuch-redux || -0.03% | | shootout/k-nucleotide || -0.02% | | shootout/n-body || -0.06% | | shootout/spectral-norm || -0.01% | | spectral/cryptarithm2 || +1.25% | | spectral/fibheaps || +18.33% | | spectral/last-piece || -0.34% | +===============================++==========+ | geom mean || +0.17% | There are extensive notes in !8897 about the regressions. Briefly * fibheaps: there was a very delicately balanced inlining that tipped over the wrong way after this change. * cryptarithm2 and paraffins are caused by #22274, which is a separate issue really. (I.e. the right fix is *not* to make inlining "win" over rules.) So I'm accepting these changes Metric Increase: T10421 T16577 T9961
* Export symbolSing, SSymbol, and friends (CLC#85)wip/clc-85Ryan Scott2022-10-067-13/+49
| | | | | | | | | | | | | | | This implements this Core Libraries Proposal: https://github.com/haskell/core-libraries-committee/issues/85 In particular, it: 1. Exposes the `symbolSing` method of `KnownSymbol`, 2. Exports the abstract `SSymbol` type used in `symbolSing`, and 3. Defines an API for interacting with `SSymbol`. This also makes corresponding changes for `natSing`/`KnownNat`/`SNat` and `charSing`/`KnownChar`/`SChar`. This fixes #15183 and addresses part (2) of #21568.
* Fix a bug in continuation capture across multiple stack chunksAlexis King2022-10-012-0/+33
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* Boxity: Don't update Boxity unless worker/wrapper follows (#21754)wip/T21754Sebastian Graf2022-09-304-1/+19
| | | | | | | | A small refactoring in our Core Opt pipeline and some new functions for transfering argument boxities from one signature to another to facilitate `Note [Don't change boxity without worker/wrapper]`. Fixes #21754.
* Demand: Format Call SubDemands `Cn(sd)` as `C(n,sd)` (#22231)wip/T22231Sebastian Graf2022-09-2939-108/+116
| | | | | | | | Justification in #22231. Short form: In a demand like `1C1(C1(L))` it was too easy to confuse which `1` belongs to which `C`. Now that should be more obvious. Fixes #22231
* Avoid Data.List.group; prefer Data.List.NonEmpty.groupBodigrim2022-09-282-4/+5
| | | | | This allows to avoid further partiality, e. g., map head . group is replaced by map NE.head . NE.group, and there are less panic calls.
* Refactor UnfoldingSource and IfaceUnfoldingSimon Peyton Jones2022-09-2817-75/+66
| | | | | | | | | | | | | | | | | | | | | | I finally got tired of the way that IfaceUnfolding reflected a previous structure of unfoldings, not the current one. This MR refactors UnfoldingSource and IfaceUnfolding to be simpler and more consistent. It's largely just a refactor, but in UnfoldingSource (which moves to GHC.Types.Basic, since it is now used in IfaceSyn too), I distinguish between /user-specified/ and /system-generated/ stable unfoldings. data UnfoldingSource = VanillaSrc | StableUserSrc -- From a user-specified pragma | StableSystemSrc -- From a system-generated unfolding | CompulsorySrc This has a minor effect in CSE (see the use of isisStableUserUnfolding in GHC.Core.Opt.CSE), which I tripped over when working on specialisation, but it seems like a Good Thing to know anyway.
* Improve aggressive specialisationSimon Peyton Jones2022-09-2812-61/+116
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch fixes #21286, by not unboxing dictionaries in worker/wrapper (ever). The main payload is tiny: * In `GHC.Core.Opt.DmdAnal.finaliseArgBoxities`, do not unbox dictionaries in `get_dmd`. See Note [Do not unbox class dictionaries] in that module * I also found that imported wrappers were being fruitlessly specialised, so I fixed that too, in canSpecImport. See Note [Specialising imported functions] point (2). In doing due diligence in the testsuite I fixed a number of other things: * Improve Note [Specialising unfoldings] in GHC.Core.Unfold.Make, and Note [Inline specialisations] in GHC.Core.Opt.Specialise, and remove duplication between the two. The new Note describes how we specialise functions with an INLINABLE pragma. And simplify the defn of `spec_unf` in `GHC.Core.Opt.Specialise.specCalls`. * Improve Note [Worker/wrapper for INLINABLE functions] in GHC.Core.Opt.WorkWrap. And (critially) make an actual change which is to propagate the user-written pragma from the original function to the wrapper; see `mkStrWrapperInlinePrag`. * Write new Note [Specialising imported functions] in GHC.Core.Opt.Specialise All this has a big effect on some compile times. This is compiler/perf, showing only changes over 1%: Metrics: compile_time/bytes allocated ------------------------------------- LargeRecord(normal) -50.2% GOOD ManyConstructors(normal) +1.0% MultiLayerModulesTH_OneShot(normal) +2.6% PmSeriesG(normal) -1.1% T10547(normal) -1.2% T11195(normal) -1.2% T11276(normal) -1.0% T11303b(normal) -1.6% T11545(normal) -1.4% T11822(normal) -1.3% T12150(optasm) -1.0% T12234(optasm) -1.2% T13056(optasm) -9.3% GOOD T13253(normal) -3.8% GOOD T15164(normal) -3.6% GOOD T16190(normal) -2.1% T16577(normal) -2.8% GOOD T16875(normal) -1.6% T17836(normal) +2.2% T17977b(normal) -1.0% T18223(normal) -33.3% GOOD T18282(normal) -3.4% GOOD T18304(normal) -1.4% T18698a(normal) -1.4% GOOD T18698b(normal) -1.3% GOOD T19695(normal) -2.5% GOOD T5837(normal) -2.3% T9630(normal) -33.0% GOOD WWRec(normal) -9.7% GOOD hard_hole_fits(normal) -2.1% GOOD hie002(normal) +1.6% geo. mean -2.2% minimum -50.2% maximum +2.6% I diligently investigated some of the big drops. * Caused by not doing w/w for dictionaries: T13056, T15164, WWRec, T18223 * Caused by not fruitlessly specialising wrappers LargeRecord, T9630 For runtimes, here is perf/should+_run: Metrics: runtime/bytes allocated -------------------------------- T12990(normal) -3.8% T5205(normal) -1.3% T9203(normal) -10.7% GOOD haddock.Cabal(normal) +0.1% haddock.base(normal) -1.1% haddock.compiler(normal) -0.3% lazy-bs-alloc(normal) -0.2% ------------------------------------------ geo. mean -0.3% minimum -10.7% maximum +0.1% I did not investigate exactly what happens in T9203. Nofib is a wash: +-------------------------------++--+-----------+-----------+ | || | tsv (rel) | std. err. | +===============================++==+===========+===========+ | real/anna || | -0.13% | 0.0% | | real/fem || | +0.13% | 0.0% | | real/fulsom || | -0.16% | 0.0% | | real/lift || | -1.55% | 0.0% | | real/reptile || | -0.11% | 0.0% | | real/smallpt || | +0.51% | 0.0% | | spectral/constraints || | +0.20% | 0.0% | | spectral/dom-lt || | +1.80% | 0.0% | | spectral/expert || | +0.33% | 0.0% | +===============================++==+===========+===========+ | geom mean || | | | +-------------------------------++--+-----------+-----------+ I spent quite some time investigating dom-lt, but it's pretty complicated. See my note on !7847. Conclusion: it's just a delicate inlining interaction, and we have plenty of those. Metric Decrease: LargeRecord T13056 T13253 T15164 T16577 T18223 T18282 T18698a T18698b T19695 T9630 WWRec hard_hole_fits T9203
* matchLocalInst: do domination analysissheaf2022-09-287-0/+130
| | | | | | | | | | | | | | | | | | | | | | | | | | When multiple Given quantified constraints match a Wanted, and there is a quantified constraint that dominates all others, we now pick it to solve the Wanted. See Note [Use only the best matching quantified constraint]. For example: [G] d1: forall a b. ( Eq a, Num b, C a b ) => D a b [G] d2: forall a . C a Int => D a Int [W] {w}: D a Int When solving the Wanted, we find that both Givens match, but we pick the second, because it has a weaker precondition, C a Int, compared to (Eq a, Num Int, C a Int). We thus say that d2 dominates d1; see Note [When does a quantified instance dominate another?]. This domination test is done purely in terms of superclass expansion, in the function GHC.Tc.Solver.Interact.impliedBySCs. We don't attempt to do a full round of constraint solving; this simple check suffices for now. Fixes #22216 and #22223