- Apr 10, 2024
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Fixes a memory leak in rts/linker/PEi386.c
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- Apr 09, 2024
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Hopefully the final fix needed for #24533
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As there are many 'CompiledByteCode' objects alive during a GHCi session, representing its element in a more packed manner improves space behaviour at a minimal cost. When running GHCi on the agda codebase, we find around 380 live 'CompiledByteCode' objects. Packing their respective 'UnlinkedByteCode' can save quite some pointers.
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- Apr 08, 2024
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This allows us to use a NoCommentsLocation for the possibly trailing comma location in a StringLiteral. This in turn allows us to correctly roundtrip via makeDeltaAst.
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This allows us to use an EpDelta if needed when using makeDeltaAst.
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Thunk analysis showed that we have about 100_000 thunks (in agda and `-fwrite-simplified-core`) pointing to the name of the name decl. Forcing this thunk fixes this issue. The thunk created here is retained by the thunk created by forkM, it is better to eagerly force this because the result (a `Name`) is already retained indirectly via the `IfaceDecl`.
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In `FastStringTable`, we count the number of z-encoded FastStrings that exist in a GHC session. We used to UNPACK the counters to not waste memory, but live retainer analysis showed that we allocate a lot of `FastMutInt`s, retained by `mkFastZString`. We lazily compute the `FastZString`, only incrementing the counter when the `FastZString` is forced. The function `mkFastStringWith` calls `mkZFastString` and boxes the `FastMutInt`, leading to the following core: mkFastStringWith = \ mk_fs _ -> = case stringTable of { FastStringTable _ n_zencs segments# _ -> ... case ((mk_fs (I# ...) (FastMutInt n_zencs)) `cast` <Co:2> :: ...) ... Marking this field as `NOUNPACK` avoids this reboxing, eliminating the allocation of a fresh `FastMutInt` on every `FastString` allocation. -
`UnlinkedBCO`'s can occur many times in the heap. Each `UnlinkedBCO` references two `UArray`'s but never indexes them. They are only needed to encode the elements into a `ByteArray#`. The three words for the lower bound, upper bound and number of elements are essentially unused, thus we replace `UArray` with a wrapper around `ByteArray#`. This saves us up to three words for each `UnlinkedBCO`. Further, to avoid re-allocating these words for `ResolvedBCO`, we repeat the procedure for `ResolvedBCO` and add custom `Binary` and `Show` instances. For example, agda's repl session has around 360_000 UnlinkedBCO's, so avoiding these three words is already saving us around 8MB residency.
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- Apr 05, 2024
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So we can update it to a delta position in makeDeltaAst if needed.
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This allows us to update them for makeDeltaAst in ghc-exactprint
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For many, many years `GHCForeignImportPrim` has suffered from the rather restrictive limitation of not allowing any non-trivial types in arguments or results. This limitation was justified by the code generator allegely barfing in the presence of such types. However, this restriction appears to originate well before the NCG rewrite and the new NCG does not appear to have any trouble with such types (see the added `T24598` test). Lift this restriction. Fixes #24598.
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- Apr 04, 2024
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Before this patch: data ArgPat p = InvisPat (LHsType p) | VisPat (LPat p) With this patch: data Pat p = ... | InvisPat (LHsType p) ... And the same transformation in the TH land. The rest of the changes is just updating code to handle new AST and writing tests to check if it is possible to create invalid states using TH. Metric Increase: MultiLayerModulesTH_OneShot -
`Array` contains three additional `Word`'s we do not need in `FlatBag`. Move `FlatBag` to `SmallArray`. Expand the API of SmallArray by `sizeofSmallArray` and add common traversal functions, such as `mapSmallArray` and `foldMapSmallArray`. Additionally, allow users to force the elements of a `SmallArray` via `rnfSmallArray`.
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LinkedLists are notoriously memory ineffiecient when all we do is traversing a structure. As 'UnlinkedBCO' has been identified as a data structure that impacts the overall memory usage of GHCi sessions, we avoid linked lists and prefer flattened structure for storing. We introduce a new memory efficient representation of sequential elements that has special support for the cases: * Empty * Singleton * Tuple Elements This improves sharing in the 'Empty' case and avoids the overhead of 'Array' until its constant overhead is justified.
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- Apr 03, 2024
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This fixes #24582, a small but long-standing bug
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This MR started as: allow the simplifer to do more in one pass, arising from places I could see the simplifier taking two iterations where one would do. But it turned into a larger project, because these changes unexpectedly made inlining blow up, especially join points in deeply-nested cases. The main changes are below. There are also many new or rewritten Notes. Avoiding simplifying repeatedly ~~~~~~~~~~~~~~~ See Note [Avoiding simplifying repeatedly] * The SimplEnv now has a seInlineDepth field, which says how deep in unfoldings we are. See Note [Inline depth] in Simplify.Env. Currently used only for the next point: avoiding repeatedly simplifying coercions. * Avoid repeatedly simplifying coercions. see Note [Avoid re-simplifying coercions] in Simplify.Iteration As you'll see from the Note, this makes use of the seInlineDepth. * Allow Simplify.Iteration.simplAuxBind to inline used-once things. This is another part of Note [Post-inline for single-use things], and is really good for reducing simplifier iterations in situations like case K e of { K x -> blah } wher x is used once in blah. * Make GHC.Core.SimpleOpt.exprIsConApp_maybe do some simple case elimination. Note [Case elim in exprIsConApp_maybe] * Improve the case-merge transformation: - Move the main code to `GHC.Core.Utils.mergeCaseAlts`, to join `filterAlts` and friends. See Note [Merge Nested Cases] in GHC.Core.Utils. - Add a new case for `tagToEnum#`; see wrinkle (MC3). - Add a new case to look through join points: see wrinkle (MC4) postInlineUnconditionally ~~~~~~~~~~~~~~~~~~~~~~~~~ * Allow Simplify.Utils.postInlineUnconditionally to inline variables that are used exactly once. See Note [Post-inline for single-use things]. * Do not postInlineUnconditionally join point, ever. Doing so does not reduce allocation, which is the main point, and with join points that are used a lot it can bloat code. See point (1) of Note [Duplicating join points] in GHC.Core.Opt.Simplify.Iteration. * Do not postInlineUnconditionally a strict (demanded) binding. It will not allocate a thunk (it'll turn into a case instead) so again the main point of inlining it doesn't hold. Better to check per-call-site. * Improve occurrence analyis for bottoming function calls, to help postInlineUnconditionally. See Note [Bottoming function calls] in GHC.Core.Opt.OccurAnal Inlining generally ~~~~~~~~~~~~~~~~~~ * In GHC.Core.Opt.Simplify.Utils.interestingCallContext, use RhsCtxt NonRecursive (not BoringCtxt) for a plain-seq case. See Note [Seq is boring] Also, wrinkle (SB1), inline in that `seq` context only for INLINE functions (UnfWhen guidance). * In GHC.Core.Opt.Simplify.Utils.interestingArg, - return ValueArg for OtherCon [c1,c2, ...], but - return NonTrivArg for OtherCon [] This makes a function a little less likely to inline if all we know is that the argument is evaluated, but nothing else. * isConLikeUnfolding is no longer true for OtherCon {}. This propagates to exprIsConLike. Con-like-ness has /positive/ information. Join points ~~~~~~~~~~~ * Be very careful about inlining join points. See these two long Notes Note [Duplicating join points] in GHC.Core.Opt.Simplify.Iteration Note [Inlining join points] in GHC.Core.Opt.Simplify.Inline * When making join points, don't do so if the join point is so small it will immediately be inlined; check uncondInlineJoin. * In GHC.Core.Opt.Simplify.Inline.tryUnfolding, improve the inlining heuristics for join points. In general we /do not/ want to inline join points /even if they are small/. See Note [Duplicating join points] GHC.Core.Opt.Simplify.Iteration. But sometimes we do: see Note [Inlining join points] in GHC.Core.Opt.Simplify.Inline; and the new `isBetterUnfoldingThan` function. * Do not add an unfolding to a join point at birth. This is a tricky one and has a long Note [Do not add unfoldings to join points at birth] It shows up in two places - In `mkDupableAlt` do not add an inlining - (trickier) In `simplLetUnfolding` don't add an unfolding for a fresh join point I am not fully satisifed with this, but it works and is well documented. * In GHC.Core.Unfold.sizeExpr, make jumps small, so that we don't penalise having a non-inlined join point. Performance changes ~~~~~~~~~~~~~~~~~~~ * Binary sizes fall by around 2.6%, according to nofib. * Compile times improve slightly. Here are the figures over 1%. I investiate the biggest differnce in T18304. It's a very small module, just a few hundred nodes. The large percentage difffence is due to a single function that didn't quite inline before, and does now, making code size a bit bigger. I decided gains outweighed the losses. Metrics: compile_time/bytes allocated (changes over +/- 1%) ------------------------------------------------ CoOpt_Singletons(normal) -9.2% GOOD LargeRecord(normal) -23.5% GOOD MultiComponentModulesRecomp(normal) +1.2% MultiLayerModulesTH_OneShot(normal) +4.1% BAD PmSeriesS(normal) -3.8% PmSeriesV(normal) -1.5% T11195(normal) -1.3% T12227(normal) -20.4% GOOD T12545(normal) -3.2% T12707(normal) -2.1% GOOD T13253(normal) -1.2% T13253-spj(normal) +8.1% BAD T13386(normal) -3.1% GOOD T14766(normal) -2.6% GOOD T15164(normal) -1.4% T15304(normal) +1.2% T15630(normal) -8.2% T15630a(normal) NEW T15703(normal) -14.7% GOOD T16577(normal) -2.3% GOOD T17516(normal) -39.7% GOOD T18140(normal) +1.2% T18223(normal) -17.1% GOOD T18282(normal) -5.0% GOOD T18304(normal) +10.8% BAD T18923(normal) -2.9% GOOD T1969(normal) +1.0% T19695(normal) -1.5% T20049(normal) -12.7% GOOD T21839c(normal) -4.1% GOOD T3064(normal) -1.5% T3294(normal) +1.2% BAD T4801(normal) +1.2% T5030(normal) -15.2% GOOD T5321Fun(normal) -2.2% GOOD T6048(optasm) -16.8% GOOD T783(normal) -1.2% T8095(normal) -6.0% GOOD T9630(normal) -4.7% GOOD T9961(normal) +1.9% BAD WWRec(normal) -1.4% info_table_map_perf(normal) -1.3% parsing001(normal) +1.5% geo. mean -2.0% minimum -39.7% maximum +10.8% * Runtimes generally improve. In the testsuite perf/should_run gives: Metrics: runtime/bytes allocated ------------------------------------------ Conversions(normal) -0.3% T13536a(optasm) -41.7% GOOD T4830(normal) -0.1% haddock.Cabal(normal) -0.1% haddock.base(normal) -0.1% haddock.compiler(normal) -0.1% geo. mean -0.8% minimum -41.7% maximum +0.0% * For runtime, nofib is a better test. The news is mostly good. Here are the number more than +/- 0.1%: # bytes allocated ==========================++========== imaginary/digits-of-e1 || -14.40% imaginary/digits-of-e2 || -4.41% imaginary/paraffins || -0.17% imaginary/rfib || -0.15% imaginary/wheel-sieve2 || -0.10% real/compress || -0.47% real/fluid || -0.10% real/fulsom || +0.14% real/gamteb || -1.47% real/gg || -0.20% real/infer || +0.24% real/pic || -0.23% real/prolog || -0.36% real/scs || -0.46% real/smallpt || +4.03% shootout/k-nucleotide || -20.23% shootout/n-body || -0.42% shootout/spectral-norm || -0.13% spectral/boyer2 || -3.80% spectral/constraints || -0.27% spectral/hartel/ida || -0.82% spectral/mate || -20.34% spectral/para || +0.46% spectral/rewrite || +1.30% spectral/sphere || -0.14% ==========================++========== geom mean || -0.59% real/smallpt has a huge nest of local definitions, and I could not pin down a reason for a regression. But there are three big wins! Metric Decrease: CoOpt_Singletons LargeRecord T12227 T12707 T13386 T13536a T14766 T15703 T16577 T17516 T18223 T18282 T18923 T21839c T20049 T5321Fun T5030 T6048 T8095 T9630 T783 Metric Increase: MultiLayerModulesTH_OneShot T13253-spj T18304 T18698a T9961 T3294 -
Pure refactoring
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This is a pure refactor
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Ensure that WorkWrap preserves lambda binders, in case of join points. Sadly I have forgotten why I made this change (it was while I was doing a lot of meddling in the Simplifier, but * it does no harm, * it is slightly more efficient, and * presumably it made something better! Anyway I have kept it in a separate commit.
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When exploring compile-time regressions after meddling with the Simplifier, I discovered that GHC.HsToCore.Pmc.Solver.Types.trvVarInfo was very delicately balanced. It's a small, heavily used, overloaded function and it's important that it inlines. By a fluke it was before, but at various times in my journey it stopped doing so. So I just added an INLINE pragma to it; no sense in depending on a delicately-balanced fluke.
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Eliminate a redundant case at birth. This sometimes reduces Simplifier iterations. See Note [Case elim in exprIsConApp_maybe].
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See Note [Eta expanding through CallStacks] in GHC.Core.Opt.Arity This is a one-line change, that fixes an inconsistency - || isCallStackPredTy ty + || isCallStackPredTy ty || isCallStackTy ty
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See the new Note [Floating join point bindings]. * Completely get rid of the complicated join_ceiling nonsense, which I have never understood. * Do not float join points at all, except perhaps to top level. * Some refactoring around wantToFloat, to treat Rec and NonRec more uniformly
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* Make `mkSymCo` and `mkInstCo` smarter Fixes #23642 * Fix return role of `SelCo` in the coercion optimiser. Fixes #23617 * Make the coercion optimiser `opt_trans_rule` work better for newtypes Fixes #23619
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I can't think of any good reason that anything in this MR should have changed the number of allocations, up or down. (Yes this is an empty commit.) Metric Decrease: T12227 -
All the changes are in fact not changes at all. Previously, the IoSubSystem data type was defined in GHC.RTS.Flags and exported from both GHC.RTS.Flags and GHC.IO.SubSystem. Now, the data type is defined in GHC.IO.SubSystem and still exported from both modules. Therefore, the same exports and same instances are still available from both modules. But the base-exports records only the defining module, and so it looks like a change when it is fully compatible. Related: we do add a deprecation to the export of the type via GHC.RTS.Flags, telling people to use the export from GHC.IO.SubSystem. Also the sort order for some unrelated Show instances changed. No idea why. The same changes apply in the other versions, with a few more changes due to sort order weirdness.
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Some GCC versions don't know about some warnings, and they complain that we're ignoring unknown warnings. So we try to ignore the warning based on the GCC version.
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Previously it was unclear that they did not work because the code path was shared with other I/O managers (in particular select()). Following the code carefully shows that what actually happens is that the calling thread would block forever: the thread will be put into the blocked queue, but no other action is scheduled that will ever result in it getting unblocked. It's better to just fail loudly in case anyone accidentally calls it, also it's less confusing code.
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Document the extra +RTS --info output in the user guide
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Using the new tracer class. Note: The unconditional definition of showIOManager should be compatible with the debugTrace change in 7c7d1f66. Co-authored-by:
Pi Delport <pi@well-typed.com>
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It's just to make sure an exception CAF is a GC root.
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Provide an opaque (forward) definition in Capability.h (since the cap contains a *CapIOManager) and then only provide a full definition in a new file IOManagerInternals.h. This new file is only supposed to be included by the IOManager implementation, not by its users. So that means IOManager.c and individual I/O manager implementations. The posix/Signals.c still needs direct access, but that should be eliminated. Anything that needs direct access either needs to be clearly part of an I/O manager (e.g. the sleect() one) or go via a proper API.
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