October 2018 - ghc-tickets

[GHC] #15698: SingleEntry update flag for Stg bindings is not used
by GHC 03 Oct '18

03 Oct '18

#15698: SingleEntry update flag for Stg bindings is not used -------------------------------------+------------------------------------- Reporter: osa1 | Owner: (none) Type: task | Status: new Priority: lowest | Milestone: 8.6.1 Component: Compiler | Version: 8.6.1 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 was looking at code generation for bindings with different update flags. Update flag type is defined as: {{{ data UpdateFlag = ReEntrant | Updatable | SingleEntry }}} I realized that we don't care about the difference between `ReEntrant` and `SingleEntry`, we only care about whether a binding is updatable or not, which is defined as {{{ isUpdatable :: UpdateFlag -> Bool isUpdatable ReEntrant = False isUpdatable SingleEntry = False isUpdatable Updatable = True }}} So we could remove `SingleEntry` and replace all uses of it with `ReEntrant` and everything would work the same. This raises the question of whether we're missing an optimisation in the code generator. Looking at code generation differences of updatable and non-updatable bindings, it seems like for a thunk (a binding with no arguments) we generate a thunk header and push an update frame regardless of the update flag. As far as I can see, update flag is only used when generating AP and selector thunks (we don't generate AP or selector thunks if the binding is not updatable). My question is: it seems to me that if a thunk is single entry then we should be able to give it a non-thunk type (maybe FUN?) and avoid pushing an update frame in `closureCodeBody`. Am I missing anything or is this possible? Is this worth trying? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15698> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15701: HEAD: Build failure in ghc-prim
by GHC 03 Oct '18

03 Oct '18

#15701: HEAD: Build failure in ghc-prim -------------------------------------+------------------------------------- Reporter: trommler | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.8.1 Component: Compiler | Version: Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Building GHC Unknown/Multiple | failed Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Building GHC at changeset:21efbc7599e39ec93b8b I see the following message: {{{ checking whether GCC supports __atomic_ builtins... no configure: creating ./config.status config.status: error: cannot find input file: `ghc-prim.buildinfo.in' libraries/ghc-prim/ghc.mk:4: recipe for target 'libraries/ghc-prim/dist- install/package-data.mk' failed }}} And indeed there is no file `ghc-prim.buildinfo.in` in libraries/ghc-prim. There is no 8.7 for version so I am leaving it empty. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15701> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7897: MakeTypeRep fingerprints be proper, robust fingerprints
by GHC 03 Oct '18

03 Oct '18

#7897: MakeTypeRep fingerprints be proper, robust fingerprints -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: ⊥ Component: Compiler | Version: 7.6.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by adamgundry): * cc: adamgundry (added) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7897#comment:9> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7897: MakeTypeRep fingerprints be proper, robust fingerprints
by GHC 03 Oct '18

03 Oct '18

#7897: MakeTypeRep fingerprints be proper, robust fingerprints -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: ⊥ Component: Compiler | Version: 7.6.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by adamgundry): Another use case for this is in the `safecopy` package (see https://github.com/acid-state/acid- state/issues/102#issuecomment-426327014), where it would be useful to be able to notice that the developer has changed a type used for binary serialization purposes. That said, perhaps a TH/Generics solution would be possible, so it may not be worth changing the current semantics of fingerprints. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7897#comment:8> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #2783: RTS -K/-M options not honored
by GHC 03 Oct '18

03 Oct '18

#2783: RTS -K/-M options not honored -----------------------------------+------------------------------ Reporter: j.waldmann | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 6.10.2 Component: Runtime System | Version: 6.10.1 Resolution: | Keywords: Operating System: Linux | Architecture: x86 Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -----------------------------------+------------------------------ Changes (by bgamari): * owner: igloo => (none) * type: merge => bug * status: closed => new * resolution: fixed => Comment: It looks like this should be re-opened. The associated test has been fragile in the CircleCI slow-validate way. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/2783#comment:7> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9136: Constant folding in Core could be better
by GHC 02 Oct '18

02 Oct '18

#9136: Constant folding in Core could be better ------------------------------+-------------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Runtime performance bug Unknown/Multiple | Test Case: Difficulty: Unknown | Blocking: Blocked By: | Related Tickets: | ------------------------------+-------------------------------------------- Constant folding in Core is still a bit feeble. For example, when staring at the code for `nofib/shootout/k-nucleotide` I saw this expression: {{{ (x +# 8) -# 1 }}} which would be relatively easy to optimise. The difficulty is knowing where to stop. What about `(8 +# x) -# 1`? Anyway, this ticket is to record the issue. Currently constant folding is done by the built-in RULES in `compiler/prelude/PrelRules`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9136> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10791: Add a --disable-large-memory-space configure option
by GHC 02 Oct '18

02 Oct '18

#10791: Add a --disable-large-memory-space configure option -------------------------------------+------------------------------------- Reporter: erikd | Owner: erikd Type: feature | Status: new request | Priority: normal | Milestone: 7.12.1 Component: Build | Version: 7.11 System | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- GHC recently started using large (1TB) address space on 64 bit systems. This feature is enabled by default but does not work on arm64-linux or amd64-solaris. Even just for testing, it would be nice to be able to disable this. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10791> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15699: Run sanity checker in more testsuite runs
by GHC 02 Oct '18

02 Oct '18

#15699: Run sanity checker in more testsuite runs -------------------------------------+------------------------------------- Reporter: bgamari | Owner: bgamari Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Continuous | Version: 8.4.3 Integration | 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: -------------------------------------+------------------------------------- Every testsuite run should run at least a subset of tests with the sanity checker enabled. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15699> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15697: Typed holes inferring a more polymorphic type
by GHC 02 Oct '18

02 Oct '18

#15697: Typed holes inferring a more polymorphic type -------------------------------------+------------------------------------- Reporter: sreenidhi | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.6.1 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: -------------------------------------+------------------------------------- Consider these two snippets. {{{#!hs testFailure :: Char testFailure = let x = id _ in x }}} Suggestions provided were {{{ /home/sreenidhi/Experiments/TypedHole.hs:3:14: error: • Found hole: _ :: a Where: ‘a’ is a rigid type variable bound by the inferred type of x :: a at /home/sreenidhi/Experiments/TypedHole.hs:3:7-14 • In the first argument of ‘id’, namely ‘_’ In the expression: id _ In an equation for ‘x’: x = id _ • Relevant bindings include x :: a (bound at /home/sreenidhi/Experiments/TypedHole.hs:3:7) testFailure :: Char (bound at /home/sreenidhi/Experiments/TypedHole.hs:2:1) }}} whereas for this one {{{#!hs testSuccess :: Char testSuccess = _ }}} It correctly suggests {{{ /home/sreenidhi/Experiments/TypedHole.hs:7:15: error: • Found hole: _ :: Char • In the expression: _ In an equation for ‘testSuccess’: testSuccess = _ • Relevant bindings include testSuccess :: Char (bound at /home/sreenidhi/Experiments/TypedHole.hs:7:1) Valid hole fits include testSuccess :: Char (bound at /home/sreenidhi/Experiments/TypedHole.hs:7:1) testFailure :: Char (defined at /home/sreenidhi/Experiments/TypedHole.hs:2:1) maxBound :: forall a. Bounded a => a with maxBound @Char (imported from ‘Prelude’ at /home/sreenidhi/Experiments/TypedHole.hs:1:1 (and originally defined in ‘GHC.Enum’)) minBound :: forall a. Bounded a => a with minBound @Char (imported from ‘Prelude’ at /home/sreenidhi/Experiments/TypedHole.hs:1:1 (and originally defined in ‘GHC.Enum’)) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15697> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7535: Using -with-rtsopts=-N should fail unless -threaded is also specified
by GHC 02 Oct '18

02 Oct '18

#7535: Using -with-rtsopts=-N should fail unless -threaded is also specified -------------------------------------+------------------------------------- Reporter: mhoermann | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: 4243 | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by osa1): The problem is `-with-rtsopts` is really dumb, it just puts whatever you pass to it in a file which is linked with the program to provide the options to the RTS. It does not do any checks on the input. For example, `-with-rtsopts=-blah-blah` is also accepted. Ideally I guess the compiler would have access to RTS argument parsers for all RTS variants, and check with the parser of the correct RTS variant (e.g. when building prof+debug way it would use the prof+debug runtime's parser). It seems like too much work and it's not clear whether the added complexity (for having access to RTS parsers in the compiler) would worth it. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7535#comment:8> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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