December 2015 - ghc-tickets

Re: [GHC] #7289: Mingw FPU init not Windows compatible.
by GHC 30 Dec '15

30 Dec '15

#7289: Mingw FPU init not Windows compatible. -----------------------------------+----------------------------- Reporter: Lennart | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Runtime System | Version: 7.2.2 Resolution: | Keywords: Operating System: Windows | Architecture: x86 Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -----------------------------------+----------------------------- Comment (by Phyx-): Yeah it is, and it's also unlikely to be changed as they say it's wanted behavior http://article.gmane.org/gmane.comp.gnu.mingw.w64.general/10686. Even though it introduces some very odd/unexpected behavior https://github.com/numpy/numpy/issues/5194. It seems an easy solution/workaround is to indeed link in `CRT_fp8.o` or `CRT_fp10.o` -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7289#comment:7> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5834: Allow both INLINE and INLINABLE for the same function
by GHC 30 Dec '15

30 Dec '15

#5834: Allow both INLINE and INLINABLE for the same function -------------------------------------+------------------------------------- Reporter: rl | Owner: Type: feature request | Status: new Priority: normal | Milestone: 8.0.1 Component: Compiler | Version: 7.5 Resolution: | 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: | -------------------------------------+------------------------------------- Description changed by bgamari: Old description: > Sometimes you really want both. Here is a small example: > > {{{ > module T where > > foo :: Num a => a -> a -> a > foo x y = x+y+1 > }}} > > {{{ > module U where > > import T > > appl :: (a -> b) -> a -> b > {-# NOINLINE appl #-} > appl f x = f x > > bar :: Int -> Int -> Int > bar x y = appl foo x y > }}} > > If I mark `foo` as `INLINE`, then GHC generates this code for `bar`: > > {{{ > bar1 :: Int -> Int -> Int > bar1 = foo @ Int $fNumInt > > bar :: Int -> Int -> Int > bar = \ (x_aa0 :: Int) (y_aa1 :: Int) -> appl @ Int @ (Int -> Int) bar1 > x_aa0 y_aa1 > }}} > > Whereas with `INLINABLE`, we get a nice specialisation but, of course, > not guarantees with respect to inlining. > > In general, it seems that requiring a function to inline when it is > saturated and requiring it two specialise when it isn't are two different > things and shouldn't be mutually exclusive. New description: Sometimes you really want both. Here is a small example: {{{#!hs module T where foo :: Num a => a -> a -> a foo x y = x+y+1 }}} {{{#!hs module U where import T appl :: (a -> b) -> a -> b {-# NOINLINE appl #-} appl f x = f x bar :: Int -> Int -> Int bar x y = appl foo x y }}} If I mark `foo` as `INLINE`, then GHC generates this code for `bar`: {{{#!hs bar1 :: Int -> Int -> Int bar1 = foo @ Int $fNumInt bar :: Int -> Int -> Int bar = \ (x_aa0 :: Int) (y_aa1 :: Int) -> appl @ Int @ (Int -> Int) bar1 x_aa0 y_aa1 }}} Whereas with `INLINABLE`, we get a nice specialisation but, of course, not guarantees with respect to inlining. In general, it seems that requiring a function to inline when it is saturated and requiring it to specialise when it isn't are two different things and shouldn't be mutually exclusive. -- -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5834#comment:7> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7367: float-out causes extra allocation
by GHC 30 Dec '15

30 Dec '15

#7367: float-out causes extra allocation -------------------------------------+------------------------------------- Reporter: wurmli | Owner: Type: bug | Status: new Priority: normal | Milestone: Research | needed Component: Compiler | Version: 7.6.1 Resolution: | Keywords: Operating System: Linux | Architecture: x86_64 Type of failure: Runtime | (amd64) performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * milestone: 8.0.1 => Research needed Comment: As has been discussed in this ticket, GHC could in principle do better in optimizing imperative code such as this. However, exactly how this should be done is a topic that would require research. Setting the milestone appropriately. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7367#comment:23> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7289: Mingw FPU init not Windows compatible.
by GHC 30 Dec '15

30 Dec '15

#7289: Mingw FPU init not Windows compatible. -----------------------------------+----------------------------- Reporter: Lennart | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Runtime System | Version: 7.2.2 Resolution: | Keywords: Operating System: Windows | Architecture: x86 Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -----------------------------------+----------------------------- Changes (by bgamari): * cc: Phyx-, simonmar (added) Comment: Phyx-, do you know whether this is still the case? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7289#comment:6> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5615: ghc produces poor code for `div` with constant powers of 2.
by GHC 30 Dec '15

30 Dec '15

#5615: ghc produces poor code for `div` with constant powers of 2. -------------------------------------+------------------------------------- Reporter: Lennart | Owner: | daniel.is.fischer Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Compiler | Version: 7.4.1-rc1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: x86 Type of failure: Runtime | Test Case: performance bug | Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * failure: None/Unknown => Runtime performance bug -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5615#comment:25> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5835: Make better use of known dictionaries
by GHC 30 Dec '15

30 Dec '15

#5835: Make better use of known dictionaries -------------------------------------+------------------------------------- Reporter: rl | Owner: Type: feature request | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 7.5 Resolution: | 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: | -------------------------------------+------------------------------------- Changes (by bgamari): * milestone: 8.0.1 => 8.2.1 Old description: > Example: > > {{{ > {-# LANGUAGE GADTs #-} > module T5835 where > > data T a where > T :: Eq a => a -> T a > > foo :: a -> T a -> Bool > {-# INLINE foo #-} > foo x = \(T y) -> x == y > > appl :: (a -> b) -> a -> b > {-# NOINLINE appl #-} > appl f x = f x > > bar :: T Int -> Bool > bar t = appl (foo 42) t > }}} > > GHC generates this for `bar`: > > {{{ > bar2 :: Int > bar2 = I# 42 > > bar1 :: T Int -> Bool > bar1 = > \ (ds_dhk :: T Int) -> > case ds_dhk of _ { T $dEq_agz y_aa4 -> > == @ Int $dEq_agz bar2 y_aa4 > } > > bar :: T Int -> Bool > bar = \ (t_aga :: T Int) -> appl @ (T Int) @ Bool bar1 t_aga > }}} > > Note how it want to get the `Eq` dictionary for `Int` from `T`. But we > know the `Eq Int` instance without inspecting `T` and `bar` could be > significantly simplified if we used that. New description: Example: {{{#!hs {-# LANGUAGE GADTs #-} module T5835 where data T a where T :: Eq a => a -> T a foo :: a -> T a -> Bool {-# INLINE foo #-} foo x = \(T y) -> x == y appl :: (a -> b) -> a -> b {-# NOINLINE appl #-} appl f x = f x bar :: T Int -> Bool bar t = appl (foo 42) t }}} GHC generates this for `bar`: {{{ bar2 :: Int bar2 = I# 42 bar1 :: T Int -> Bool bar1 = \ (ds_dhk :: T Int) -> case ds_dhk of _ { T $dEq_agz y_aa4 -> == @ Int $dEq_agz bar2 y_aa4 } bar :: T Int -> Bool bar = \ (t_aga :: T Int) -> appl @ (T Int) @ Bool bar1 t_aga }}} Note how it want to get the `Eq` dictionary for `Int` from `T`. But we know the `Eq Int` instance without inspecting `T` and `bar` could be significantly simplified if we used that. -- Comment: Looks like this won't make it for 8.0. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5835#comment:7> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #595: Overhaul GHC's overlapping/non-exhaustive pattern checking
by GHC 30 Dec '15

30 Dec '15

#595: Overhaul GHC's overlapping/non-exhaustive pattern checking -------------------------------------+------------------------------------- Reporter: simonmar | Owner: Type: task | Status: closed Priority: normal | Milestone: 8.0.1 Component: Compiler | Version: None Resolution: fixed | Keywords: warnings Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: N/A Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by adamgundry): * status: new => closed * resolution: None => fixed * milestone: ⊥ => 8.0.1 Comment: Great work @gkaracha! -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/595#comment:29> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #4012: Compilation results are not deterministic
by GHC 30 Dec '15

30 Dec '15

#4012: Compilation results are not deterministic -------------------------------------+------------------------------------- Reporter: kili | Owner: niteria Type: bug | Status: new Priority: high | Milestone: 8.0.1 Component: Compiler | Version: 6.12.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Other | Test Case: Blocked By: | Blocking: Related Tickets: #10424 | Differential Rev(s): Phab:D910, | Phab:D1073, Phab:D1133, Phab:D1192, | Phab:D1268, Phab:D1360, Phab:D1373, | Phab:D1396, Phab:D1457, Phab:D1468, Wiki Page: | Phab:D1487, Phab:D1504, Phab:D1508 -------------------------------------+------------------------------------- Changes (by bgamari): * owner: => niteria -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4012#comment:140> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #4012: Compilation results are not deterministic
by GHC 30 Dec '15

30 Dec '15

#4012: Compilation results are not deterministic -------------------------------------+------------------------------------- Reporter: kili | Owner: Type: bug | Status: new Priority: high | Milestone: 8.0.1 Component: Compiler | Version: 6.12.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Other | Test Case: Blocked By: | Blocking: Related Tickets: #10424 | Differential Rev(s): Phab:D910, | Phab:D1073, Phab:D1133, Phab:D1192, | Phab:D1268, Phab:D1360, Phab:D1373, | Phab:D1396, Phab:D1457, Phab:D1468, Wiki Page: | Phab:D1487, Phab:D1504, Phab:D1508 -------------------------------------+------------------------------------- Changes (by bgamari): * owner: niteria => * status: patch => new Comment: I'm going to remove the `patch` status since all of the outstanding diffs for this ticket have been merged. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4012#comment:139> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11305: TC Regression
by GHC 29 Dec '15

29 Dec '15

#11305: TC Regression -------------------------------------+------------------------------------- Reporter: hvr | Owner: Type: bug | Status: new Priority: highest | Milestone: 8.0.1 Component: Compiler | Version: 7.11 (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: -------------------------------------+------------------------------------- TODO: figure out better summary ;-) The following snippet extracted from Edward's `profunctors` package compiles with GHC 7.10.3, but fails to type-check with GHC HEAD: {{{#!hs {-# LANGUAGE RankNTypes #-} {-# LANGUAGE TypeOperators #-} module Data.Profunctor.Strong where import Control.Arrow import Control.Category import Data.Tuple import Prelude hiding (id,(.)) infixr 0 :-> type p :-> q = forall a b. p a b -> q a b class Profunctor p where dimap :: (a -> b) -> (c -> d) -> p b c -> p a d class ProfunctorFunctor t where promap :: Profunctor p => (p :-> q) -> t p :-> t q class ProfunctorFunctor t => ProfunctorMonad t where proreturn :: Profunctor p => p :-> t p projoin :: Profunctor p => t (t p) :-> t p class ProfunctorFunctor t => ProfunctorComonad t where proextract :: Profunctor p => t p :-> p produplicate :: Profunctor p => t p :-> t (t p) class Profunctor p => Strong p where first' :: p a b -> p (a, c) (b, c) first' = dimap swap swap . second' second' :: p a b -> p (c, a) (c, b) second' = dimap swap swap . first' ---------------------------------------------------------------------------- newtype Tambara p a b = Tambara { runTambara :: forall c. p (a, c) (b, c) } instance Profunctor p => Profunctor (Tambara p) where dimap f g (Tambara p) = Tambara $ dimap (first f) (first g) p instance ProfunctorFunctor Tambara where promap f (Tambara p) = Tambara (f p) instance ProfunctorComonad Tambara where proextract (Tambara p) = dimap (\a -> (a,())) fst p produplicate (Tambara p) = Tambara (Tambara $ dimap hither yon p) where hither :: ((a, b), c) -> (a, (b, c)) hither ~(~(x,y),z) = (x,(y,z)) yon :: (a, (b, c)) -> ((a, b), c) yon ~(x,~(y,z)) = ((x,y),z) instance Profunctor p => Strong (Tambara p) where first' = runTambara . produplicate }}} {{{ Strong.hs:57:12: error: • Couldn't match type ‘Tambara p (a, c) (b, c)’ with ‘forall c1. Tambara p (a, c1) (b, c1)’ Expected type: Tambara (Tambara p) a b -> Tambara p (a, c) (b, c) Actual type: Tambara (Tambara p) a b -> forall c. Tambara p (a, c) (b, c) • In the first argument of ‘(.)’, namely ‘runTambara’ In the expression: runTambara . produplicate In an equation for ‘first'’: first' = runTambara . produplicate • Relevant bindings include first' :: Tambara p a b -> Tambara p (a, c) (b, c) (bound at Strong.hs:57:3) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11305> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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