September 2018 - ghc-tickets

[GHC] #14482: GHC -M mode fails to ensure that boot files are built before source files
by GHC 26 Nov '18

26 Nov '18

#14482: GHC -M mode fails to ensure that boot files are built before source files -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.4.1 Component: Compiler | Version: 8.2.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Imagine we have a module with a boot file. In general it is necessary to ensure that we compile the boot file *before* the source file to ensure that the `hi-boot` file exists when we go to typecheck the module (triggering the behavior observed in #14481). However, `ghc -M` doesn't guarantee this. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14482> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15019: Fix performance regressions from #14737
by GHC 26 Nov '18

26 Nov '18

#15019: Fix performance regressions from #14737 -------------------------------------+------------------------------------- Reporter: tdammers | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: #14737 Differential Rev(s): D4568 | Wiki Page: -------------------------------------+------------------------------------- #14737, while drastically improving performance on some edge cases, introduces performance regressions in 3 test cases: perf/compiler/parsing001.run perf/compiler/T9020.run perf/compiler/T12707.run -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15019> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15366: GHC.Conc.Windows has a surprising queue
by GHC 26 Nov '18

26 Nov '18

#15366: GHC.Conc.Windows has a surprising queue -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.8.1 Component: Core | Version: 8.4.3 Libraries | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Runtime Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- `GHC.Conc.Windows` seems to use `[DelayReq]` as a priority queue, and uses `foldr` to insert multiple elements into it. Unless these lists are always very short (are they?) that seems like a bad idea. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15366> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14534: Split T12971 into its own Makefile
by GHC 26 Nov '18

26 Nov '18

#14534: Split T12971 into its own Makefile -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: (none) Type: task | Status: new Priority: low | Milestone: 8.6.1 Component: Test Suite | Version: 8.2.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Other Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- `testsuite/tests/driver/Makefile` includes the `T12971` target. This (intentionally) has non-ASCII characters in it. As a result, any change to that makefile will trigger a lint error. We should give that test its own makefile to isolate it a bit. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14534> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15484: MultiLayerModules and T13701 timeout on i386 Linux
by GHC 26 Nov '18

26 Nov '18

#15484: MultiLayerModules and T13701 timeout on i386 Linux -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- CircleCI's Linux/i386 configuration fails with timeouts on `MultiLayerModules`, `T13701`, -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15484> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14190: Typeable imposes seemingly redundant constraints on polykinded instances
by GHC 26 Nov '18

26 Nov '18

#14190: Typeable imposes seemingly redundant constraints on polykinded instances -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.4.1 Component: Compiler | Version: 8.2.1 (Type checker) | Keywords: | Operating System: Unknown/Multiple TypeableReflection | Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- To derive `Data` for `Const`, we need {{{#!hs deriving instance (Typeable k, Data a, Typeable (b :: k)) => Data (Const a b) }}} Where's that `Typeable k` constraint come from? It turns out that for reasons I haven't looked into, we can only obtain `Typeable (Const a (b :: k))` if we have `Typeable k`; `(Typeable a, Typeable b)` is insufficient. Is there a reason for that? Annoyingly, we can actually ''get'' that: {{{#!hs weGotThat :: forall k (a :: k). Typeable a :- Typeable k weGotThat = Sub $ withTypeable (typeRepKind (typeRep :: TypeRep a)) Dict }}} But of course that doesn't help us. Could we use `UndecidableSuperClasses` to work around this problem? I think we likely can, although I'm concerned about the performance implications: {{{#!hs class (Typeable a, Typeable' k) => Typeable' (a :: k) instance (Typeable a, Typeable' k) => Typeable' (a :: k) withTypeable' :: forall k (a :: k) r. TypeRep a -> (Typeable' a => r) -> r withTypeable' tr f = withTypeable tr $ withTypeable (typeRepKind (typeRep @a)) f }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14190> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13573: Add Foldable1 / Traversable1 to base
by GHC 26 Nov '18

26 Nov '18

#13573: Add Foldable1 / Traversable1 to base -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: #10365 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- `NonEmpty` and `Semigroup` are in ''base'' and are on our way to add `Semigroup` as a superclass of `Monoid` (#10365), this is a fine time to ask if we should include [https://hackage.haskell.org/package/semigroupoids-5.1/docs/Data- Semigroup-Foldable.html Foldable1], [https://hackage.haskell.org/package/semigroupoids-5.1/docs/Data- Semigroup-Traversable.html Traversable1] in ''base'' as well. `Foldable` has partial functions already, functions that only make sense for non-empty structures such as `foldr1`, `foldl1`, `minimum` and `maximum`. There are also functions which ''could'' be defined in terms of `Foldable` like `head` / `tail` (for definition of `unimprove` and `Diff` see [https://github.com/ekmett/semigroupoids/issues/49 semigroupoids issue #49] and this [https://github.com/arkeet/difference/blob/0f0e14f51cf1ecd7ebf2d8c52204bd91a… github] page) {{{#!hs minimum1 :: (Ord a, Foldable1 f) => f a -> a minimum1 = S.getMin . foldMap1 S.Min maximum1 :: (Ord a, Foldable1 f) => f a -> a maximum1 = S.getMax . foldMap1 S.Max head1 :: Foldable1 f => f a -> a head1 = S.getFirst . foldMap1 S.First last1 :: Foldable1 f => f a -> a last1 = S.getLast . foldMap1 S.Last foldr1 :: Foldable1 t => (a -> a -> a) -> (t a -> a) foldr1 f = unimprove . foldMap1 (\a -> Diff (f a) a) foldl1 :: Foldable1 t => (a -> a -> a) -> (t a -> a) foldl1 f = unimprove . getDual . foldMap1 (\a -> Dual $ Diff (flip f a) a) }}} There is also the possibility of adding further functions such as `foldM`, `foldM_`, `foldrM` and `foldlM` for non-empty structures. As usual I don't have more concrete ideas, but let's start by testing the waters before submitting a ghc-proposal. I understand this may be controversial -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13573> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13362: GHC first generation of GC to be as large as largest cache size by default
by GHC 26 Nov '18

26 Nov '18

#13362: GHC first generation of GC to be as large as largest cache size by default -------------------------------------+------------------------------------- Reporter: varosi | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: Runtime | Version: 8.0.2 System | Keywords: numa cache gc | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This will improve performance a lot by default. If anyone needs different size - there is "-A" RTS option. Machines are very different. Currently this size is 512k by default for all different architectures and hardware no matter what. In most cases machines with larger caches have more RAM as well and vice versa. So this will affect positively both small and larger machines. It will be most efficient in most cases to keep short lived objects in caches. Most modern workstation and server machines have L3 cache as well, that is why I'm asking for "largest cache size". Second idea will be if there are two short lived generations on machines with second and third level caches with sizes that match both. For NUMA machines with non-unified caches (like [http://www.hardkernel.com/main/products/prdt_info.php?g_code=G143452239825 this strange and non-common ARM]) the common solution could be to set first generation to be with size of the largest cache of smallest core. Which will not be the optimal, but close to. [https://www.reddit.com/r/haskell/comments/5rf1r5/ghc_first_generation_of_gc… Related Reddit discussion] -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13362> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10844: CallStack should not be inlined
by GHC 26 Nov '18

26 Nov '18

#10844: CallStack should not be inlined -------------------------------------+------------------------------------- Reporter: nomeata | Owner: Type: task | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- The use of CallStack based error messages (since changeset:6740d70d95cb) has led to some code size increase, and I believe this needs to be improved. While investigating the #10788, I was looking at the core produced by that code, and I found this in the code: {{{ -- RHS size: {terms: 2, types: 0, coercions: 0} Main.main17 :: [Char] [GblId, Str=DmdType, Unf=Unf{Src=<vanilla>, TopLvl=True, Value=False, ConLike=False, WorkFree=False, Expandable=False, Guidance=IF_ARGS [] 100 0}] Main.main17 = unpackCString# "vecto_20t0fI93Jj9LUbaZg6e04I"# -- RHS size: {terms: 2, types: 0, coercions: 0} Main.main16 :: [Char] [GblId, Str=DmdType, Unf=Unf{Src=<vanilla>, TopLvl=True, Value=False, ConLike=False, WorkFree=False, Expandable=False, Guidance=IF_ARGS [] 110 0}] Main.main16 = unpackCString# "Data.Vector.Primitive.Mutable"# -- RHS size: {terms: 2, types: 0, coercions: 0} Main.main15 :: [Char] [GblId, Str=DmdType, Unf=Unf{Src=<vanilla>, TopLvl=True, Value=False, ConLike=False, WorkFree=False, Expandable=False, Guidance=IF_ARGS [] 120 0}] Main.main15 = unpackCString# "./Data/Vector/Primitive/Mutable.hs"# -- RHS size: {terms: 2, types: 0, coercions: 0} Main.main14 :: Int [GblId, Caf=NoCafRefs, Str=DmdType, Unf=Unf{Src=<vanilla>, TopLvl=True, Value=True, ConLike=True, WorkFree=True, Expandable=True, Guidance=IF_ARGS [] 10 20}] Main.main14 = I# 97# -- RHS size: {terms: 2, types: 0, coercions: 0} Main.main13 :: Int [GblId, Caf=NoCafRefs, Str=DmdType, Unf=Unf{Src=<vanilla>, TopLvl=True, Value=True, ConLike=True, WorkFree=True, Expandable=True, Guidance=IF_ARGS [] 10 20}] Main.main13 = I# 16# -- RHS size: {terms: 2, types: 0, coercions: 0} Main.main12 :: Int [GblId, Caf=NoCafRefs, Str=DmdType, Unf=Unf{Src=<vanilla>, TopLvl=True, Value=True, ConLike=True, WorkFree=True, Expandable=True, Guidance=IF_ARGS [] 10 20}] Main.main12 = I# 21# -- RHS size: {terms: 8, types: 0, coercions: 0} Main.main11 :: SrcLoc [GblId, Str=DmdType, Unf=Unf{Src=<vanilla>, TopLvl=True, Value=True, ConLike=True, WorkFree=True, Expandable=True, Guidance=IF_ARGS [] 10 80}] Main.main11 = SrcLoc Main.main17 Main.main16 Main.main15 Main.main14 Main.main13 Main.main14 Main.main12 }}} This is clearly a CallStack from a library, and there is no point in copying that into the (every?) use of wherever that came from, as it will only increase code size and slow down compilation. I don’t know how to fix it, though. Float out CallStacks more aggressively? Or is the problem that unfoldings are recorded before that can happen? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10844> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10803: New TypeSignatureSections extension
by GHC 26 Nov '18

26 Nov '18

#10803: New TypeSignatureSections extension -------------------------------------+------------------------------------- Reporter: hvr | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.12.1 Component: Compiler | Version: 7.10.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- = Preliminary specification Have - `(::` ''type'' `)` be syntax sugar for - `(\x -> x ::` ''type'' `)` This new syntax extension is enabled via a new `TypeSignatureSections` language pragma, i.e. {{{#!hs {#- LANGUAGE TypeSignatureSections #-} }}} TODO: formalise this a bit more -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10803> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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