April 2018 - ghc-tickets

[GHC] #14673: Unary Unboxed Tuple Type Constructor
by GHC 21 Jun '18

21 Jun '18

#14673: Unary Unboxed Tuple Type Constructor -------------------------------------+------------------------------------- Reporter: andrewthad | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.1-alpha1 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: -------------------------------------+------------------------------------- The type constructor for a unary unboxed tuple cannot be written in GHC haskell. Consider the following value which is wrapped in by a unary unboxed tuple: {{{ >>> :type (# 5# #) (# 5# #) :: (# Int# #) }}} Now consider the type constructor for unboxed 2-tuples: {{{ >>> :set -fprint-explicit-kinds >>> :set -fprint-explicit-foralls >>> :kind! (# , #) (# , #) :: forall (k0 :: RuntimeRep) (k1 :: RuntimeRep). TYPE k0 -> TYPE k1 -> TYPE ('TupleRep ((':) RuntimeRep k0 ((':) RuntimeRep k1 ('[] RuntimeRep)))) = (#,#) }}} Horrid looking, but undoubtedly correct. But how can we do this for a unary unboxed tuple? The naive approach gives us the nullary tuple instead: {{{ >>> :kind! (# #) (# #) :: TYPE ('TupleRep ('[] RuntimeRep)) = (# #) }}} I do actually have a real use-case for this that I can discuss more if needed. For the syntax, I really haven't the faintest idea what I would expect. Maybe something like: `(## ##)` or `(# @1 #)`, but those both seem pretty bad. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14673> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14617: Join point test join001 doesn't seem to be properly automated
by GHC 21 Jun '18

21 Jun '18

#14617: Join point test join001 doesn't seem to be properly automated -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Test Suite | Version: 8.2.2 Keywords: JoinPoints | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The test `join001` was presumably used for manual testing (poring over the Core by hand). Unfortunately, the test suite runs it in an utterly bland fashion that doesn't appear to check whether the join point transformation is working as intended. The other join point tests run in this fashion (`join005` and `join006`) include notes indicating that Core Lint will trip if the desired property doesn't hold; there is no such note here. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14617> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14319: Stuck kind families can lead to lousy error messages
by GHC 21 Jun '18

21 Jun '18

#14319: Stuck kind families can lead to lousy error messages -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.4.1 Component: Compiler | Version: 8.3 (Type checker) | Keywords: TypeInType, | Operating System: Unknown/Multiple TypeFamilies | Architecture: | Type of failure: Poor/confusing Unknown/Multiple | error message Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{#!hs {-# language TypeFamilies, TypeInType, ScopedTypeVariables #-} module ArityError where import Data.Kind import GHC.TypeLits import Data.Proxy type family F (s :: Symbol) :: Type type family G (s :: Symbol) :: F s type instance G "Hi" = Maybe }}} This produces the error message {{{#!hs ArityError.hs:10:24: error: • Expecting one more argument to ‘Maybe’ Expected kind ‘F "Hi"’, but ‘Maybe’ has kind ‘* -> *’ • In the type ‘Maybe’ In the type instance declaration for ‘G’ | 10 | type instance G "Hi" = Maybe | ^^^^^ }}} This looks utterly bogus: `F "Hi"` is stuck, so we have no idea what arity it indicates. What I ''think'' is a term level version of this, {{{#!hs f :: forall (s :: Symbol). Proxy s -> F s f _ = Just }}} gives a much less confusing message: {{{ ArityError.hs:14:7: error: • Couldn't match expected type ‘F s’ with actual type ‘a0 -> Maybe a0’ The type variable ‘a0’ is ambiguous • In the expression: Just In an equation for ‘f’: f _ = Just • Relevant bindings include f :: Proxy s -> F s (bound at ArityError.hs:14:1) | 14 | f _ = Just | ^^^^ }}} The fix (I think) is to refrain from reporting arity errors when we don't know enough about the relevant arities. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14319> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13724: Clamping of llvm llc to -O1 and -O2
by GHC 21 Jun '18

21 Jun '18

#13724: Clamping of llvm llc to -O1 and -O2 -------------------------------------+------------------------------------- Reporter: angerman | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.4.1 Component: Compiler | Version: 8.3 (LLVM) | 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: -------------------------------------+------------------------------------- We currently clamp the optimization level of llvm llc (3.9 and 4.0) within `[1,2]`. The reason is that with `-O0`, the naive register allocator can topple over with {{{ Error while trying to spill R1 from class GPR: Cannot scavenge register without an emergency spill slot! }}} and with `-O3` the `llvm::SelectionDAGISel::LowerArguments` may break, when compiling `rts/HeapStackCheck.cmm` with the stage1 ghc. {{{ 0 llc 0x0000000102ae63e8 llvm::sys::PrintStackTrace(llvm::raw_ostream&) + 40 1 llc 0x0000000102ae69a6 SignalHandler(int) + 358 2 libsystem_platform.dylib 0x00007fffc23f4b3a _sigtramp + 26 3 libsystem_c.dylib 0x00007fffc226498b __vfprintf + 17876 4 llc 0x00000001029d5123 llvm::SelectionDAGISel::LowerArguments(llvm::Function const&) + 5699 5 llc 0x0000000102a21a35 llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&) + 3381 6 llc 0x0000000102a202b1 llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&) + 1457 7 llc 0x0000000101bdc474 (anonymous namespace)::ARMDAGToDAGISel::runOnMachineFunction(llvm::MachineFunction&) + 20 8 llc 0x00000001025573a6 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) + 134 9 llc 0x000000010274fb12 llvm::FPPassManager::runOnFunction(llvm::Function&) + 498 10 llc 0x000000010274fd23 llvm::FPPassManager::runOnModule(llvm::Module&) + 67 11 llc 0x00000001027501b8 llvm::legacy::PassManagerImpl::run(llvm::Module&) + 920 12 llc 0x000000010195f075 compileModule(char**, llvm::LLVMContext&) + 12133 13 llc 0x000000010195bf0b main + 491 14 libdyld.dylib 0x00007fffc21e5235 start + 1 Stack dump: 0. Program arguments: llc -O3 -mtriple=arm-unknown-linux-gnueabihf -enable-tbaa /var/folders/fv/xqjrpfj516n5xq_m_ljpsjx00000gn/T/ghc33674_0/ghc_6.bc -o /var/folders/fv/xqjrpfj516n5xq_m_ljpsjx00000gn/T/ghc33674_0/ghc_7.lm_s 1. Running pass 'Function Pass Manager' on module '/var/folders/fv/xqjrpfj516n5xq_m_ljpsjx00000gn/T/ghc33674_0/ghc_6.bc'. 2. Running pass 'ARM Instruction Selection' on function '@"stg_gc_f1$def"' }}} `opt` and `llc` should respect `-opt_lo` and `-opt_lc`, such that `-opt_lc=-O3` can be used to validate the behaviour. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13724> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14413: Profiling breaks determinism
by GHC 21 Jun '18

21 Jun '18

#14413: Profiling breaks determinism -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.4.1 Component: Compiler | Version: 8.2.1 Keywords: determinism | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- While looking at #5889 I noticed that `CostCentre` currently includes a `Unique` (although it's represented as an `Int` for reasons that aren't relevant here; I change this in Phab:D4148). This unique identifies the cost centre and appears to be derived from the unique of a binder. This presumably breaks determinism. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14413> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13240: Make it easier to find builds we may want to cancel
by GHC 21 Jun '18

21 Jun '18

#13240: Make it easier to find builds we may want to cancel -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: mpickering Type: feature | Status: new request | Priority: normal | Milestone: 8.4.1 Component: Trac & Git | Version: 8.0.1 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: -------------------------------------+------------------------------------- I'd love to have a relatively easy way to hunt down and abort Harbormaster builds that aren't very useful, and perhaps to avoid some obviously wasteful builds. Examples: 1. Someone pushed several versions of a single differential, and it seems clear that only the most recent version is likely to be of interest. 2. A build for a different architecture/OS has failed for a reason that seems obviously non-platform-specific. 3. Only documentation files have changed. Building these on one platform should be sufficient. 4. A differential was closed by a commit. Only the most recent build will be useful, if that. It would also be nice to get a list of build jobs waiting for specific platforms. These days, for example, we seem to have a lot more demand than supply for OSX bots. If we could get a list of all pending OSX builds, we could look through them by hand and see if any should be canceled. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13240> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13205: Run `validate --slow` during CI at least sometimes.
by GHC 21 Jun '18

21 Jun '18

#13205: Run `validate --slow` during CI at least sometimes. -------------------------------------+------------------------------------- Reporter: dobenour | Owner: 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: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- We really should run `validate --slow` at times. It would catch #13204. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13205> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10059: :i doesn't work for ~
by GHC 21 Jun '18

21 Jun '18

#10059: :i doesn't work for ~ -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 7.11 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Other Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- {{{#!hs Prelude> :set -XTypeOperators Prelude> :i (~) <interactive>:1:2: parse error on input ‘~’ Prelude> :k (~) (~) :: k -> k -> Constraint }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10059> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15098: Missing instances for Down
by GHC 20 Jun '18

20 Jun '18

#15098: Missing instances for Down -------------------------------------+------------------------------------- Reporter: ekmett | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: 8.6.1 Component: Core | Version: 8.2.2 Libraries | 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: -------------------------------------+------------------------------------- `Down` in `Data.Ord` is missing the instances for `Monad`, `MonadFix`, `MonadZip`, `Eq1`, `Ord1`, `Show1`, `Read1`, `Data`, `Generic`, `Generic1`, `Foldable`, `Traversable`. We added a bunch of common sense 'only one definition' instances over the last few GHC releases, but apparently we missed `Data.Ord.Down`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15098> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14023: Split up glasgow_exts.rst
by GHC 19 Jun '18

19 Jun '18

#14023: Split up glasgow_exts.rst -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: task | Status: new Priority: normal | Milestone: 8.4.1 Component: Documentation | Version: 8.0.1 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: -------------------------------------+------------------------------------- The `docs/users-guide/glasgow_exts.rst` is crazy large. This makes it difficult to navigate both while editing and reading. It should probably be split up into multiple files along the top-level headings. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14023> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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