July 2017 - ghc-tickets

[GHC] #14007: CI builds for integer-simple variant of GHC for Windows
by GHC 01 Aug '17

01 Aug '17

#14007: CI builds for integer-simple variant of GHC for Windows ---------------------------------------+--------------------------------- Reporter: varosi | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.2 Keywords: | Operating System: Windows Architecture: x86_64 (amd64) | Type of failure: None/Unknown Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: ---------------------------------------+--------------------------------- Currently for Haskell production non-open-source software integer-simple builds of GHC for Windows are needed. GMP Integer library is GPL and cannot be used for such production software. Is it possible to make such official builds of GHC? This will stimulate more Haskell as a production language. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14007> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14061: `instance Eq Dyn`
by GHC 01 Aug '17

01 Aug '17

#14061: `instance Eq Dyn` -------------------------------------+------------------------------------- Reporter: zaoqi | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.0.2 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: -------------------------------------+------------------------------------- {{{#!hs {-# LANGUAGE KindSignatures, GADTs #-} data Dyn :: * where Dyn :: a -> Dyn }}} How to write the correct `instance Eq Dyn`, do not change `data Dyn`? {{{#!hs {-# LANGUAGE MultiParamTypeClasses, FlexibleInstances #-} class GEq a b where geq :: a -> b -> Bool instance {-# OVERLAPPABLE #-} (Eq a) => GEq a a where geq = (==) instance {-# OVERLAPPING #-} GEq a b where geq _ _ = False }}} {{{#!hs instance Eq Dyn where Dyn a == Dyn b = geq a b }}} {{{ GHCi, version 8.0.2: http://www.haskell.org/ghc/ :? for help Prelude> :load Dyn.hs [1 of 1] Compiling Main ( Dyn.hs, interpreted ) Ok, modules loaded: Main. *Main> Dyn () == Dyn () False }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14061> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13567: Do loopification using join points
by GHC 01 Aug '17

01 Aug '17

#13567: Do loopification using join points -------------------------------------+------------------------------------- Reporter: simonpj | 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: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Here's an idea: use join points to accomplish all that the existing "loopification" patch does, and more. The idea is described under "New idea: use join points" in [wiki:Commentary/Compiler/Loopification]. This ticket is to discuss and track progress. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13567> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #1600: Optimisation: CPR the results of IO
by GHC 31 Jul '17

31 Jul '17

#1600: Optimisation: CPR the results of IO -------------------------------------+------------------------------------- Reporter: simonmar | Owner: (none) Type: task | Status: new Priority: lowest | Milestone: Component: Compiler | Version: 6.6.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: #8598 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by bgamari): What is the status of this, akio? > I wonder if this improvement justifies the added complexity to the compiler (about 400 lines of code added under `compiler/`). Right now I don't see any way to make the analysis/transformation more effective. Well, 2.6% improvement in runtime is quite sizeable. This sounds quite worthwhile to me. Good work! Simon, do you agree? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/1600#comment:74> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14067: Static Argument Transformation for tail-recursive functions
by GHC 31 Jul '17

31 Jul '17

#14067: Static Argument Transformation for tail-recursive functions -------------------------------------+------------------------------------- Reporter: nomeata | Owner: (none) Type: task | 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: -------------------------------------+------------------------------------- In #13966 it was determined that having a variant of the Static Argument Transformation (StaticArgumentTransformation) pass that would specifically look for tail-recursive functions, and turn them into recursive join points, would be beneficial. This ticket tracks this task. Consider {{{ f x y = case y of A -> f x y' B -> e2 C -> e3 }}} Here the first argument to f is "static"; that is, the same in every call. So we can transform like this {{{ f x y = joinrec $j y = case y of A -> $j y' B -> e2 C -> e3 in $j y }}} Note that `x` isn't passed around in every iteration. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14067> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14046: “Illegal type synonym family application in instance” is too strict in the presence of functional dependencies
by GHC 31 Jul '17

31 Jul '17

#14046: “Illegal type synonym family application in instance” is too strict in the presence of functional dependencies -------------------------------------+------------------------------------- Reporter: lexi.lambda | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: GHC rejects Unknown/Multiple | valid program Test Case: | Blocked By: Blocking: | Related Tickets: #3485 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- GHC rejects the following instance, complaining about the use of a type synonym family in the instance head: {{{#!hs type family Fam a class Multi a b | a -> b instance Multi (Maybe a) (Fam a) }}} However, this seems too strict to me, since the second parameter of `Multi` is determined by a functional dependency. If I tweak the instance slightly to lift the second parameter out of the instance head into an equality constraint, GHC accepts the instance: {{{#!hs instance (b ~ Fam a) => Multi (Maybe a) b }}} It seems to me that, due to the functional dependency, these two instances are completely equivalent. Therefore, GHC should accept the first instance. This is similar to an old ticket, #3485, but that did not involve fundeps, so GHC’s error was correct. I’m pretty sure the addition of functional dependencies changes things, making the two actually equivalent. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14046> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11995: Can't infer type
by GHC 31 Jul '17

31 Jul '17

#11995: Can't infer type -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 (Type checker) | 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: -------------------------------------+------------------------------------- {{{#!hs import Data.Kind data NP :: forall k. (ĸ → Type) → ([k] → Type) where Nil :: NP f '[] (:*) :: f x → NP f xs → NP f (x:xs) newtype K a b = K a deriving Show unK (K a) = a h'collapse :: NP (K a) xs -> [a] h'collapse = \case Nil -> [] K x:*xs -> x : h'collapse xs }}} if we replace `xs` by an underscore: {{{ tJN0.hs:13:29-30: error: … • Could not deduce: (xs :: [ĸ]) ~~ ((':) ĸ x xs :: [ĸ]) from the context: ((k :: *) ~~ (ĸ :: *), (t :: [k]) ~~ ((':) ĸ x xs :: [ĸ])) bound by a pattern with constructor: :* :: forall k (f :: k -> *) (x :: k) (xs :: [k]). f x -> NP k k f xs -> NP k k f ((':) k x xs), in a case alternative at /tmp/tJN0.hs:13:3-9 ‘xs’ is a rigid type variable bound by a pattern with constructor: :* :: forall k (f :: k -> *) (x :: k) (xs :: [k]). f x -> NP k k f xs -> NP k k f ((':) k x xs), in a case alternative at /tmp/tJN0.hs:13:3 Expected type: NP ĸ k (K ĸ a) t Actual type: NP ĸ ĸ (K ĸ a) xs • In the first argument of ‘h'collapse’, namely ‘xs’ In the second argument of ‘(:)’, namely ‘h'collapse xs’ In the expression: x : h'collapse xs • Relevant bindings include xs :: NP ĸ ĸ (K ĸ a) xs (bound at /tmp/tJN0.hs:13:8) h'collapse :: NP ĸ k (K ĸ a) t -> [a] (bound at /tmp/tJN0.hs:11:1) Compilation failed. }}} Should it not be able to infer that? The Glorious Glasgow Haskell Compilation System, version 8.1.20160419 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11995> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14065: Type inference
by GHC 31 Jul '17

31 Jul '17

#14065: Type inference -------------------------------------+------------------------------------- Reporter: zaoqi | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.2 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: -------------------------------------+------------------------------------- {{{#!hs --Copyright (C) 2017 Zaoqi --This program is free software: you can redistribute it and/or modify --it under the terms of the GNU Affero General Public License as published --by the Free Software Foundation, either version 3 of the License, or --(at your option) any later version. --This program is distributed in the hope that it will be useful, --but WITHOUT ANY WARRANTY; without even the implied warranty of --MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the --GNU Affero General Public License for more details. --You should have received a copy of the GNU Affero General Public License --along with this program. If not, see <http://www.gnu.org/licenses/>. {-# LANGUAGE DataKinds, KindSignatures, GADTs #-} import Control.Exception data Nat = Z | S Nat deriving (Eq, Ord) instance Enum Nat where succ = S pred (S x) = x pred _ = throw Underflow toEnum 0 = Z toEnum x | x < 0 = throw Underflow | otherwise = S . toEnum $ pred x fromEnum Z = 0 fromEnum (S x) = succ $ fromEnum x enumFrom x = x : enumFrom (S x) instance Num Nat where Z + x = x (S x) + y = S $ x + y Z * _ = Z (S x) * y = y + (x * y) abs = id signum Z = Z signum _ = S Z fromInteger 0 = Z fromInteger x | x < 0 = throw Underflow | otherwise = S . fromInteger $ pred x x - Z = x (S x) - (S y) = x - y _ - _ = throw Underflow negate Z = Z negate _ = throw Underflow instance Real Nat where toRational = toRational . toInteger instance Integral Nat where quot x y = fromInteger $ quot (toInteger x) (toInteger y) rem x y = fromInteger $ rem (toInteger x) (toInteger y) div x y = fromInteger $ div (toInteger x) (toInteger y) mod x y = fromInteger $ mod (toInteger x) (toInteger y) quotRem x y = let (x, y) = quotRem (toInteger x) (toInteger y) in (fromInteger x, fromInteger y) divMod x y = let (x, y) = divMod (toInteger x) (toInteger y) in (fromInteger x, fromInteger y) toInteger Z = 0 toInteger (S x) = succ $ toInteger x data Vec :: Nat -> * -> * where Nil :: Vec Z a Cons :: a -> Vec x a -> Vec (S x) a data ReadableVec :: * -> * where ReadableVec :: Vec x a -> ReadableVec a instance Read a => Read (ReadableVec a) where readsPrec x s = map (\(xs, r) -> (l2rv xs, r)) (readsPrec x s) where l2rv [] = ReadableVec Nil l2rv (x : xs) = case l2rv xs of ReadableVec rs -> ReadableVec (Cons x rs) instance Show a => Show (Vec x a) where showsPrec p xs = showsPrec p (ReadableVec xs) instance Show a => Show (ReadableVec a) where showsPrec p xs = showsPrec p (rv2l xs) where rv2l :: ReadableVec x -> [x] rv2l (ReadableVec Nil) = [] rv2l (ReadableVec (Cons x xs)) = x : rv2l (ReadableVec xs) }}} {{{ GHCi, version 8.0.2: http://www.haskell.org/ghc/ :? for help Prelude> :load Vec.hs [1 of 1] Compiling Main ( Vec.hs, interpreted ) Ok, modules loaded: Main. }}} {{{#!hs --Copyright (C) 2017 Zaoqi --This program is free software: you can redistribute it and/or modify --it under the terms of the GNU Affero General Public License as published --by the Free Software Foundation, either version 3 of the License, or --(at your option) any later version. --This program is distributed in the hope that it will be useful, --but WITHOUT ANY WARRANTY; without even the implied warranty of --MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the --GNU Affero General Public License for more details. --You should have received a copy of the GNU Affero General Public License --along with this program. If not, see <http://www.gnu.org/licenses/>. {-# LANGUAGE DataKinds, KindSignatures, GADTs #-} import Control.Exception data Nat = Z | S Nat deriving (Eq, Ord) instance Enum Nat where succ = S pred (S x) = x pred _ = throw Underflow toEnum 0 = Z toEnum x | x < 0 = throw Underflow | otherwise = S . toEnum $ pred x fromEnum Z = 0 fromEnum (S x) = succ $ fromEnum x enumFrom x = x : enumFrom (S x) instance Num Nat where Z + x = x (S x) + y = S $ x + y Z * _ = Z (S x) * y = y + (x * y) abs = id signum Z = Z signum _ = S Z fromInteger 0 = Z fromInteger x | x < 0 = throw Underflow | otherwise = S . fromInteger $ pred x x - Z = x (S x) - (S y) = x - y _ - _ = throw Underflow negate Z = Z negate _ = throw Underflow instance Real Nat where toRational = toRational . toInteger instance Integral Nat where quot x y = fromInteger $ quot (toInteger x) (toInteger y) rem x y = fromInteger $ rem (toInteger x) (toInteger y) div x y = fromInteger $ div (toInteger x) (toInteger y) mod x y = fromInteger $ mod (toInteger x) (toInteger y) quotRem x y = let (x, y) = quotRem (toInteger x) (toInteger y) in (fromInteger x, fromInteger y) divMod x y = let (x, y) = divMod (toInteger x) (toInteger y) in (fromInteger x, fromInteger y) toInteger Z = 0 toInteger (S x) = succ $ toInteger x data Vec :: Nat -> * -> * where Nil :: Vec Z a Cons :: a -> Vec x a -> Vec (S x) a data ReadableVec :: * -> * where ReadableVec :: Vec x a -> ReadableVec a instance Read a => Read (ReadableVec a) where readsPrec x s = map (\(xs, r) -> (l2rv xs, r)) (readsPrec x s) where l2rv [] = ReadableVec Nil l2rv (x : xs) = case l2rv xs of ReadableVec rs -> ReadableVec (Cons x rs) instance Show a => Show (Vec x a) where showsPrec p xs = showsPrec p (ReadableVec xs) instance Show a => Show (ReadableVec a) where showsPrec p xs = showsPrec p (rv2l xs) where --rv2l :: ReadableVec x -> [x] rv2l (ReadableVec Nil) = [] rv2l (ReadableVec (Cons x xs)) = x : rv2l (ReadableVec xs) }}} {{{ GHCi, version 8.0.2: http://www.haskell.org/ghc/ :? for help Prelude> :load Vec.hs [1 of 1] Compiling Main ( Vec.hs, interpreted ) Vec.hs:79:22: error: • Could not deduce (Show a0) arising from a use of ‘showsPrec’ from the context: Show a bound by the instance declaration at Vec.hs:78:10-39 The type variable ‘a0’ is ambiguous These potential instances exist: instance Show ArithException -- Defined in ‘GHC.Exception’ instance Show ErrorCall -- Defined in ‘GHC.Exception’ instance Show SomeException -- Defined in ‘GHC.Exception’ ...plus 27 others ...plus 12 instances involving out-of-scope types (use -fprint-potential-instances to see them all) • In the expression: showsPrec p (rv2l xs) In an equation for ‘showsPrec’: showsPrec p xs = showsPrec p (rv2l xs) where rv2l (ReadableVec Nil) = [] rv2l (ReadableVec (Cons x xs)) = x : rv2l (ReadableVec xs) In the instance declaration for ‘Show (ReadableVec a)’ Vec.hs:82:34: error: • Couldn't match expected type ‘t’ with actual type ‘[t0]’ ‘t’ is untouchable inside the constraints: x ~ 'Z bound by a pattern with constructor: Nil :: forall a. Vec 'Z a, in an equation for ‘rv2l’ at Vec.hs:82:27-29 ‘t’ is a rigid type variable bound by the inferred type of rv2l :: ReadableVec t1 -> t at Vec.hs:82:9 Possible fix: add a type signature for ‘rv2l’ • In the expression: [] In an equation for ‘rv2l’: rv2l (ReadableVec Nil) = [] In an equation for ‘showsPrec’: showsPrec p xs = showsPrec p (rv2l xs) where rv2l (ReadableVec Nil) = [] rv2l (ReadableVec (Cons x xs)) = x : rv2l (ReadableVec xs) • Relevant bindings include rv2l :: ReadableVec t1 -> t (bound at Vec.hs:82:9) Vec.hs:83:46: error: • Couldn't match type ‘t’ with ‘[t1]’ ‘t’ is untouchable inside the constraints: x ~ 'S x1 bound by a pattern with constructor: Cons :: forall a (x :: Nat). a -> Vec x a -> Vec ('S x) a, in an equation for ‘rv2l’ at Vec.hs:83:28-36 ‘t’ is a rigid type variable bound by the inferred type of rv2l :: ReadableVec t1 -> t at Vec.hs:82:9 Possible fix: add a type signature for ‘rv2l’ Expected type: ReadableVec t1 -> [t1] Actual type: ReadableVec t1 -> t • In the second argument of ‘(:)’, namely ‘rv2l (ReadableVec xs)’ In the expression: x : rv2l (ReadableVec xs) In an equation for ‘rv2l’: rv2l (ReadableVec (Cons x xs)) = x : rv2l (ReadableVec xs) • Relevant bindings include xs :: Vec x1 t1 (bound at Vec.hs:83:35) x :: t1 (bound at Vec.hs:83:33) rv2l :: ReadableVec t1 -> t (bound at Vec.hs:82:9) Failed, modules loaded: none. }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14065> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13540: Enable -msse2 by default on i386
by GHC 31 Jul '17

31 Jul '17

#13540: Enable -msse2 by default on i386 -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: task | Status: new Priority: high | Milestone: 8.4.1 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: -------------------------------------+------------------------------------- SSE2 has been around for nearly 15 years now and at this point it is supported nearly universally. Currently we pass `-msse2` to numerically- sensitive testsuite tests since x87 is too imprecise. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13540> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12878: Use gold linker by default if available on ELF systems
by GHC 31 Jul '17

31 Jul '17

#12878: Use gold linker by default if available on ELF systems -------------------------------------+------------------------------------- Reporter: dobenour | Owner: Type: feature | Status: new request | Priority: normal | Milestone: Component: Driver | Version: 8.0.1 Keywords: | Operating System: Linux Architecture: | Type of failure: Compile-time Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- `ld.gold` is both faster and less buggy than `ld.bfd`, but only works on ELF. On ELF systems, we should thus prefer `ld.gold` when it is installed, even when `ld.bfd` is supported (as it is on x86). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12878> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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