- Aug 05, 2022
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We don't actually emit rodata16 sections anywhere.
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- Aug 04, 2022
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I realised hydration was completely irrelavant for this cache because the ModDetails are pruned from the result. So now it simplifies things a lot to just store the ModIface and Linkable, which we can put into the cache straight away rather than wait for the final version of a HomeModInfo to appear.
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This patch fixes quite a tricky leak where we would end up retaining stale ModDetails due to rehydrating modules against non-finalised interfaces. == Loops with multiple boot files It is possible for a module graph to have a loop (SCC, when ignoring boot files) which requires multiple boot files to break. In this case we must perform the necessary hydration steps before and after compiling modules which have boot files which are described above for corectness but also perform an additional hydration step at the end of the SCC to remove space leaks. Consider the following example: ┌───────┐ ┌───────┐ │ │ │ │ │ A │ │ B │ │ │ │ │ └─────┬─┘ └───┬───┘ │ │ ┌────▼─────────▼──┐ │ │ │ C │ └────┬─────────┬──┘ │ │ ┌────▼──┐ ┌───▼───┐ │ │ │ │ │ A-boot│ │ B-boot│ │ │ │ │ └───────┘ └───────┘ A, B and C live together in a SCC. Say we compile the modules in order A-boot, B-boot, C, A, B then when we compile A we will perform the hydration steps (because A has a boot file). Therefore C will be hydrated relative to A, and the ModDetails for A will reference C/A. Then when B is compiled C will be rehydrated again, and so B will reference C/A,B, its interface will be hydrated relative to both A and B. Now there is a space leak because say C is a very big module, there are now two different copies of ModDetails kept alive by modules A and B. The way to avoid this space leak is to rehydrate an entire SCC together at the end of compilation so that all the ModDetails point to interfaces for .hs files. In this example, when we hydrate A, B and C together then both A and B will refer to C/A,B. See #21900 for some more discussion. ------------------------------------------------------- In addition to this simple case, there is also the potential for a leak during parallel upsweep which is also fixed by this patch. Transcibed is Note [ModuleNameSet, efficiency and space leaks] Note [ModuleNameSet, efficiency and space leaks] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ During unsweep the results of compiling modules are placed into a MVar, to find the environment the module needs to compile itself in the MVar is consulted and the HomeUnitGraph is set accordingly. The reason we do this is that precisely tracking module dependencies and recreating the HUG from scratch each time is very expensive. In serial mode (-j1), this all works out fine because a module can only be compiled after its dependencies have finished compiling and not interleaved with compiling module loops. Therefore when we create the finalised or no loop interfaces, the HUG only contains finalised interfaces. In parallel mode, we have to be more careful because the HUG variable can contain non-finalised interfaces which have been started by another thread. In order to avoid a space leak where a finalised interface is compiled against a HPT which contains a non-finalised interface we have to restrict the HUG to only the visible modules. The visible modules is recording in the ModuleNameSet, this is propagated upwards whilst compiling and explains which transitive modules are visible from a certain point. This set is then used to restrict the HUG before the module is compiled to only the visible modules and thus avoiding this tricky space leak. Efficiency of the ModuleNameSet is of utmost importance because a union occurs for each edge in the module graph. Therefore the set is represented directly as an IntSet which provides suitable performance, even using a UniqSet (which is backed by an IntMap) is too slow. The crucial test of performance here is the time taken to a do a no-op build in --make mode. See test "jspace" for an example which used to trigger this problem. Fixes #21900 -
I observed some unforced thunks in the NameCache which were retaining a whole Id, which ends up retaining a Type.. which ends up retaining old copies of HscEnv containing stale HomeModInfo.
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This will only have a (very) modest impact on memory but we don't want to retain old copies of DynFlags hanging around so best to force this value.
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This fixes #21236.
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Previously, we had to disable defer-type-errors in splices because of #7276. But this fix is no longer necessary, the test T7276 no longer segfaults and is now correctly deferred.
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This patch removes the TCvSubst data type and instead uses Subst as the environment for both term and type level substitution. This change is partially motivated by the existential type proposal, which will introduce types that contain expressions and therefore forces us to carry around an "IdSubstEnv" even when substituting for types. It also reduces the amount of code because "Subst" and "TCvSubst" share a lot of common operations. There isn't any noticeable impact on performance (geo. mean for ghc/alloc is around 0.0% but we have -94 loc and one less data type to worry abount). Currently, the "TCvSubst" data type for substitution on types is identical to the "Subst" data type except the former doesn't store "IdSubstEnv". Using "Subst" for type-level substitution means there will be a redundant field stored in the data type. However, in cases where the substitution starts from the expression, using "Subst" for type-level substitution saves us from having to project "Subst" into a "TCvSubst". This probably explains why the allocation is mostly even despite the redundant field. The patch deletes "TCvSubst" and moves "Subst" and its relevant functions from "GHC.Core.Subst" into "GHC.Core.TyCo.Subst". Substitution on expressions is still defined in "GHC.Core.Subst" so we don't have to expose the definition of "Expr" in the hs-boot file that "GHC.Core.TyCo.Subst" must import to refer to "IdSubstEnv" (whose codomain is "CoreExpr"). Most functions named fooTCvSubst are renamed into fooSubst with a few exceptions (e.g. "isEmptyTCvSubst" is a distinct function from "isEmptySubst"; the former ignores the emptiness of "IdSubstEnv"). These exceptions mainly exist for performance reasons and will go away when "Expr" and "Type" are mutually recursively defined (we won't be able to take those shortcuts if we can't make the assumption that expressions don't appear in types).
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- Aug 02, 2022
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Instead of `` `cast` <Co:11> :: (Some -> Really -> Large Type)`` simply print `` `cast` <Co:11> :: ... ``
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Fixes #21894
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Fixes #21918
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- Jul 28, 2022
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This patch fixes #21806 by rectifying an incorrect claim about the usage of kind variables in the header of a data declaration with a standalone kind signature. It also adds some clarifications about the number of parameters expected in GADT declarations and in type family declarations.
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Fixes #21866
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- Jul 26, 2022
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The hadrian executable depends on QuickCheck for building, meaning this library (and its dependencies) will need to be built for bootstrapping GHC in the future. Building QuickCheck, however, can require TemplateHaskell. When building a statically linking GHC toolchain, TemplateHaskell can be tricky to get to work, and cross-compiling TemplateHaskell doesn't work at all without -fexternal-interpreter, so QuickCheck introduces an element of fragility to GHC's bootstrap. Since the selftest rules are the only part of hadrian that need QuickCheck, we can easily eliminate this bootstrap dependency when required by introducing a `selftest` flag guarding the rules' inclusion. Closes #8699.
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Residency monitoring under the non-moving collector is quite conservative (e.g. the reported value is larger than reality) since otherwise we would need to block on concurrent collection. Skip a few tests that are sensitive to residency. (cherry picked from commit 6880e4fb)
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This fixes a rather subtle bug in the logic responsible for scavenging objects evacuated to the non-moving generation. In particular, objects can be allocated into the non-moving generation by two ways: a. evacuation out of from-space by the garbage collector b. direct allocation by the mutator Like all evacuation, objects moved by (a) must be scavenged, since they may contain references to other objects located in from-space. To accomplish this we have the following scheme: * each nonmoving segment's block descriptor has a scan pointer which points to the first object which has yet to be scavenged * the GC tracks a set of "todo" segments which have pending scavenging work * to scavenge a segment, we scavenge each of the unmarked blocks between the scan pointer and segment's `next_free` pointer. We skip marked blocks since we know the allocator wouldn't have allocated into marked blocks (since they contain presumably live data). We can stop at `next_free` since, by definition, the GC could not have evacuated any objects to blocks above `next_free` (otherwise `next_free wouldn't be the first free block). However, this neglected to consider objects allocated by path (b). In short, the problem is that objects directly allocated by the mutator may become unreachable (but not swept, since the containing segment is not yet full), at which point they may contain references to swept objects. Specifically, we observed this in #21885 in the following way: 1. the mutator (specifically in #21885, a `lockCAF`) allocates an object (specifically a blackhole, which here we will call `blkh`; see Note [Static objects under the nonmoving collector] for the reason why) on the non-moving heap. The bitmap of the allocated block remains 0 (since allocation doesn't affect the bitmap) and the containing segment's (which we will call `blkh_seg`) `next_free` is advanced. 2. We enter the blackhole, evaluating the blackhole to produce a result (specificaly a cons cell) in the nursery 3. The blackhole gets updated into an indirection pointing to the cons cell; it is pushed to the generational remembered set 4. we perform a GC, the cons cell is evacuated into the nonmoving heap (into segment `cons_seg`) 5. the cons cell is marked 6. the GC concludes 7. the CAF and blackhole become unreachable 8. `cons_seg` is filled 9. we start another GC; the cons cell is swept 10. we start a new GC 11. something is evacuated into `blkh_seg`, adding it to the "todo" list 12. we attempt to scavenge `blkh_seg` (namely, all unmarked blocks between `scan` and `next_free`, which includes `blkh`). We attempt to evacuate `blkh`'s indirectee, which is the previously-swept cons cell. This is unsafe, since the indirectee is no longer a valid heap object. The problem here was that the scavenging logic *assumed* that (a) was the only source of allocations into the non-moving heap and therefore *all* unmarked blocks between `scan` and `next_free` were evacuated. However, due to (b) this is not true. The solution is to ensure that that the scanned region only encompasses the region of objects allocated during evacuation. We do this by updating `scan` as we push the segment to the todo-segment list to point to the block which was evacuated into. Doing this required changing the nonmoving scavenging implementation's update of the `scan` pointer to bump it *once*, instead of after scavenging each block as was done previously. This is because we may end up evacuating into the segment being scavenged as we scavenge it. This was quite tricky to discover but the result is quite simple, demonstrating yet again that global mutable state should be used exceedingly sparingly. Fixes #21885 (cherry picked from commit 0b27ea23) -
It can often be useful during debugging to be able to determine the state of a nonmoving segment. Introduce some state, enabled by DEBUG, to track this. (cherry picked from commit 40e797ef)
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(cherry picked from commit 19f8fce3)
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- Jul 25, 2022
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Cheng Shao authored
We no longer generate .s files anyway. Metric Decrease: MultiLayerModules T10421 T13035 T13701 T14697 T16875 T18140 T18304 T18923 T9198 -
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There was an assert error, as Gergo pointed out in #21896. I fixed this by adding an InScopeSet argument to tcUnifyTyWithTFs. And also to GHC.Core.Unify.niFixTCvSubst. I also took the opportunity to get a couple more InScopeSets right, and to change some substTyUnchecked into substTy. This MR touches a lot of other files, but only because I also took the opportunity to introduce mkInScopeSetList, and use it.
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This file is just a place to accumlate notes about particular benchmarks, so that I don't keep re-inventing the wheel.
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This patch addresses #21831, point 2. See Note [generaliseDictPats] in SpecConstr I took the opportunity to refactor the construction of specialisation rules a bit, so that the rule name says what type we are specialising at. Surprisingly, there's a 20% decrease in compile time for test perf/compiler/T18223. I took a look at it, and the code size seems the same throughout. I did a quick ticky profile which seemed to show a bit less substitution going on. Hmm. Maybe it's the "don't do eta-expansion in stable unfoldings" patch, which is part of the same MR as this patch. Anyway, since it's a move in the right direction, I didn't think it was worth looking into further. Metric Decrease: T18223
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I think this change will make little difference except to reduce clutter. But that's it -- if it causes problems we can switch it on again.
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This fixes (1) in #21831. Easy, obviously correct.
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When bootstrapping GHC 9.4.*, the build will fail when configuring ghc-cabal as part of the make based build system due to this upper bound, as Cabal has been updated to a 3.8 release. Reference #21914, see especially ghc/ghc#21914 (comment 444699)
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Fixes #21902.
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On Windows, we create multiple levels of wrappers for GHCi which ultimately execute ghc --interactive. In order to handle console events properly, each of these wrappers must call FreeConsole() in order to hand off event processing to the child process. See #14150. In addition to this, FreeConsole must only be called from interactive processes (#13411). This commit makes two changes to fix this situation: 1. The hadrian wrappers generated using `hadrian/bindist/cwrappers/version-wrapper.c` call `FreeConsole` if the CPP flag INTERACTIVE_PROCESS is set, which is set when we are generating a wrapper for GHCi. 2. The GHCi wrapper in `driver/ghci/` calls the `ghc-$VER.exe` executable which is not wrapped rather than calling `ghc.exe` is is wrapped on windows (and usually non-interactive, so can't call `FreeConsole`: Before: ghci-$VER.exe calls ghci.exe which calls ghc.exe which calls ghc-$VER.exe After: ghci-$VER.exe calls ghci.exe which calls ghc-$VER.exe
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Gergo points out (#21801) that GHC.Core.Opt.Arity.tryEtaReduce was making an ill-formed cast. It didn't matter, because the subsequent guard discarded it; but still worth fixing. Spurious warnings are distracting.
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This patch fixes #21888, and simplifies finaliseArgBoxities by eliminating the (recently introduced) data type FinalDecision. A delicate interaction meant that this patch commit d1c25a48 Date: Tue Jul 12 16:33:46 2022 +0100 Refactor wantToUnboxArg a bit make worker/wrapper go into an infinite loop. This patch fixes it by narrowing the handling of case (B) of Note [Boxity for bottoming functions], to deal only the arguemnts that are type variables. Only then do we drop the trimBoxity call, which is what caused the bug. I also * Added documentation of case (B), which was previously completely un-mentioned. And a regression test, T21888a, to test it. * Made unboxDeeplyDmd stop at lazy demands. It's rare anyway for a bottoming function to have a lazy argument (mainly when the data type is recursive and then we don't want to unbox deeply). Plus there is Note [No lazy, Unboxed demands in demand signature] * Refactored the Case equation for dmdAnal a bit, to do less redundant pattern matching.
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GHC doesn't consistently require the ConstraintKinds extension to be enabled, as it allows programs such as type families returning a constraint without this extension. MR !7784 fixes this infelicity, but breaking user programs was deemed to not be worth it, so we document it instead. Fixes #21061.
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Approved by: https://github.com/haskell/core-libraries-committee/issues/61 This adds a default implementation for `mempty` and `(<>)` along with a matching `MINIMAL` pragma so that `Semigroup` and `Monoid` instances can be defined in terms of `sconcat` / `mconcat`. The description for each class has also been updated to include the equivalent set of laws for the `sconcat`-only / `mconcat`-only instances.
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Fixes DeepSubsumption08
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