November 2014 - ghc-tickets

[GHC] #9781: Make list monad operations fuse
by GHC 12 Nov '14

12 Nov '14

#9781: Make list monad operations fuse -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: dfeuer Type: task | Status: new Priority: normal | Milestone: 7.10.1 Component: Core Libraries | Version: 7.9 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Runtime Blocked By: | performance bug Related Tickets: | Test Case: | Blocking: | Differential Revisions: Phab:D455 -------------------------------------+------------------------------------- We like to think that `do {x <- xs; y <- f x ; return g y}` is the same as `[g y | x <- xs, y <- f x]`, but the former does not fuse nearly as well. Let's fix that. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9781> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #9555: internal error: ARR_WORDS object entered!
by GHC 12 Nov '14

12 Nov '14

#9555: internal error: ARR_WORDS object entered! -------------------------------------+------------------------------------- Reporter: walck | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 (LLVM) | Keywords: Resolution: | Architecture: x86_64 (amd64) Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: None/Unknown | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Changes (by thomie): * component: Compiler => Compiler (LLVM) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9555#comment:9> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9594: Cleanup of filepath package
by GHC 12 Nov '14

12 Nov '14

#9594: Cleanup of filepath package -------------------------------------+------------------------------------- Reporter: thomie | Owner: Type: task | Status: new Priority: normal | Milestone: Component: libraries (other) | Version: 7.9 Keywords: filepath | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: #8752 | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- I did a general cleanup/refactoring of the filepath package. Notable changes: * 10% less code * 2 tiny bug fixes * a few extra tests * some more documentation The commits are in my [https://github.com/thomie/filepath/commits/cleanup cleanup branch] on Github. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9594> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9621: New Data.Foldable methods
by GHC 12 Nov '14

12 Nov '14

#9621: New Data.Foldable methods -------------------------------------+------------------------------------- Reporter: hvr | Owner: ekmett Type: task | Status: new Priority: normal | Milestone: 7.10.1 Component: Core Libraries | Version: 7.8.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: #9586 | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- place-holder text; details to follow soon -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9621> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9662: stack overflow in type checker
by GHC 11 Nov '14

11 Nov '14

#9662: stack overflow in type checker -------------------------------------+------------------------------------- Reporter: Lemming | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Compile- Blocked By: | time crash Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- The attached program causes a stack overflow when loading into ghci-7.8.3 or ghci-7.9.20140929: {{{ $ ghci-7.8.3 -Wall BackpermuteTypeLoop.hs GHCi, version 7.8.3: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. [1 of 1] Compiling BackpermuteTypeLoop ( BackpermuteTypeLoop.hs, interpreted ) *** Exception: stack overflow }}} I have no idea, what's going on. The problem may be even not critical, because the program is not type-correct anyway. If you replace the `id` argument by the out-commented `modify` argument, you will get a nice type error message. The problem arised when using the Accelerate framework and it involves the `modify` function which helps tupling function arguments and untupling function results. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9662> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7862: Could not deduce (A) from the context (A, ...)
by GHC 11 Nov '14

11 Nov '14

#7862: Could not deduce (A) from the context (A, ...) -------------------------------------+------------------------------------- Reporter: alang9 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 (Type checker) | Keywords: Resolution: | Architecture: x86_64 (amd64) Operating System: Linux | Difficulty: Unknown Type of failure: GHC | Blocked By: rejects valid program | Related Tickets: Test Case: indexed- | types/should_compile/T7862 | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by Simon Peyton Jones <simonpj@…>): In [changeset:"2b67b8f9b259c95ef9394c3a8ff801dc00e968d9/ghc"]: {{{ #!CommitTicketReference repository="ghc" revision="2b67b8f9b259c95ef9394c3a8ff801dc00e968d9" Test Trac #7862 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7862#comment:9> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9077: Forcing the type to be IO {} instead of IO() causes a "panic! The impossible has happened" output.
by GHC 11 Nov '14

11 Nov '14

#9077: Forcing the type to be IO {} instead of IO() causes a "panic! The impossible has happened" output. -------------------------+------------------------------------------------- Reporter: | Owner: Westycoot | Status: new Type: bug | Milestone: Priority: | Version: 7.8.2 normal | Operating System: Unknown/Multiple Component: | Type of failure: Compile-time performance bug Compiler | Test Case: Keywords: | Blocking: Architecture: x86 | Difficulty: | Unknown | Blocked By: | Related Tickets: | -------------------------+------------------------------------------------- Below is the source code in which the bug occurs. It is easily reproduce- able, by having the type be IO{} instead of IO(). When ran, this code will produce the "panic! The impossible has happened" output. Which told me to report the bug here. By changing IO() to IO{} (which I did by accident), no exception is thrown, it simply tells the user to panic! {{{ main :: IO {} main = do e1 <- getLine e2 <- getLine print ((read e1) + (read e2)) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9077> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7862: Could not deduce (A) from the context (A, ...)
by GHC 11 Nov '14

11 Nov '14

#7862: Could not deduce (A) from the context (A, ...) -------------------------------------+------------------------------------- Reporter: alang9 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 (Type checker) | Keywords: Resolution: | Architecture: x86_64 (amd64) Operating System: Linux | Difficulty: Unknown Type of failure: GHC | Blocked By: rejects valid program | Related Tickets: Test Case: indexed- | types/should_compile/T7862 | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Changes (by simonpj): * testcase: => indexed-types/should_compile/T7862 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7862#comment:8> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7220: Confusing error message in type checking related to type family, fundep, and higher-rank type
by GHC 11 Nov '14

11 Nov '14

#7220: Confusing error message in type checking related to type family, fundep, and higher-rank type -------------------------------------+------------------------------------- Reporter: tsuyoshi | Owner: simonpj Type: bug | Status: closed Priority: normal | Milestone: 7.8.1 Component: Compiler | Version: 7.6.1-rc1 (Type checker) | Keywords: Resolution: fixed | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: None/Unknown | Test Case: | typecheck/should_fail/T7220 | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by simonpj): Richard's fix for #9404 makes this compile. He says: The reason this went wrong before is that the old method of inferring a type would get caught when unifying a `TauTv` (the metavariable given as the guess for `f`'s type) with a polytype, deferring to the solver. If we defer, then we don't have enough information to type-check `u` successfully, and we fail. With the new inferring types with `PolyTv`, no deferring happens, and `u` type-checks fine. But with the #9404 fix, `f` is inferred to have the type as given. Then, `u` is checked (by `tcPolyExprNC`) to have the argument type of `f`, which it does. No problems. I actually think that success is the right behavior here, so I chalk this up to a success of this patch. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7220#comment:4> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9786: Make quot/rem/div/mod with known divisors fast
by GHC 11 Nov '14

11 Nov '14

#9786: Make quot/rem/div/mod with known divisors fast -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: task | Status: new Priority: normal | Milestone: 7.12.1 Component: Compiler | Version: 7.9 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Runtime Blocked By: | performance bug Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- GHC (with NCG) currently optimizes `Int` division by powers of two, but not by other known divisors. The Intel Optimization Manual section 9.2.4 describes a general technique for replacing division by known, sufficiently small, divisors with multiplication. LLVM appears to go further in some fashion. There's no reason we can't do something similar. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9786> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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