March 2015 - ghc-tickets

[GHC] #9979: Performance regression GHC 7.8.4 to GHC HEAD
by GHC 02 Mar '15

02 Mar '15

#9979: Performance regression GHC 7.8.4 to GHC HEAD -------------------------------------+------------------------------------- Reporter: alanz | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.11 Keywords: regression | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Testing with HEAD 023439980f6ef6ec051f676279ed2be5f031efe6 Baseline: GHC 7.8.4 {{{ ghc-config 7.8.4 cabal unpack haskell-src-exts cd haskell-src-exts-1.16.0.1/ cabal install --dependencies-only time (cabal clean && cabal build) real 2m38.696s user 5m17.256s sys 3m44.732s }}} Test : GHC HEAD {{{ ghc-config 7.11.20150112 cabal install --dependencies-only time (cabal clean && cabal build) real 3m35.027s user 6m45.664s sys 5m15.220s }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9979> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9994: Provide option to show current module in ghci prompt without listing imported modules.
by GHC 02 Mar '15

02 Mar '15

#9994: Provide option to show current module in ghci prompt without listing imported modules. -------------------------------------+------------------------------------- Reporter: shachaf | Owner: Type: feature | Status: new request | Milestone: Priority: normal | Version: 7.8.4 Component: GHCi | Operating System: Unknown/Multiple Keywords: | Type of failure: None/Unknown Architecture: | Blocked By: Unknown/Multiple | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- GHCi allows for `%s` in the prompt, which is replaced by the currently loaded module followed by all imported modules. However, my `.ghci` imports about a hundred modules, making the prompt way too long when I use `%s`. It would be useful to have an option for showing just the current module, and not all the imported modules. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9994> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5850: Greater customization of GHCi prompt
by GHC 02 Mar '15

02 Mar '15

#5850: Greater customization of GHCi prompt -------------------------------------+------------------------------------- Reporter: JamesFisher | Owner: jlengyel Type: feature request | Status: patch Priority: normal | Milestone: 7.12.1 Component: GHCi | Version: 7.4.1 Resolution: | Keywords: newcomer Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Blocked By: | Test Case: Related Tickets: #9994 | Blocking: | Differential Revisions: Phab:D559 -------------------------------------+------------------------------------- Changes (by thomie): * related: => #9994 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5850#comment:8> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10120: Unnecessary code duplication from case analysis
by GHC 02 Mar '15

02 Mar '15

#10120: Unnecessary code duplication from case analysis -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.1-rc2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Runtime Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- Consider a case analysis like this, {{{#!hs predicate c = c == '-' || c == '_' || c == '.' || c == '~' || c == ':' || c == '@' || c == '&' || c == '=' || c == '+' || c == '$' || c == ',' f x | predicate x = do_something f x = do_something_else main = f 'a' }}} GHC in some cases appears to produce Core for this example by constructing a case analysis on `x`, replicating `do_something` in every branch, {{{#!hs $wa_r3UQ :: GHC.Prim.Char# -> GHC.Prim.State# GHC.Prim.RealWorld -> (# GHC.Prim.State# GHC.Prim.RealWorld, () #) [GblId, Arity=2, Str=DmdType <S,1*U><L,U>] $wa_r3UQ = \ (ww_s3TD :: GHC.Prim.Char#) (w_s3TA [OS=OneShot] :: GHC.Prim.State# GHC.Prim.RealWorld) -> case ww_s3TD of _ [Occ=Dead] { __DEFAULT -> (# w_s3TA, GHC.Tuple.() #); '$' -> GHC.IO.Handle.Text.hPutStr2 GHC.IO.Handle.FD.stdout lvl2_r3Uv GHC.Types.True w_s3TA; '&' -> GHC.IO.Handle.Text.hPutStr2 GHC.IO.Handle.FD.stdout lvl4_r3Ux GHC.Types.True w_s3TA; '+' -> GHC.IO.Handle.Text.hPutStr2 GHC.IO.Handle.FD.stdout lvl6_r3Uz GHC.Types.True w_s3TA; ',' -> GHC.IO.Handle.Text.hPutStr2 GHC.IO.Handle.FD.stdout lvl8_r3UB GHC.Types.True w_s3TA; '-' -> GHC.IO.Handle.Text.hPutStr2 GHC.IO.Handle.FD.stdout lvl10_r3UD GHC.Types.True w_s3TA; '.' -> GHC.IO.Handle.Text.hPutStr2 GHC.IO.Handle.FD.stdout lvl12_r3UF GHC.Types.True w_s3TA; ':' -> GHC.IO.Handle.Text.hPutStr2 GHC.IO.Handle.FD.stdout lvl14_r3UH GHC.Types.True w_s3TA; '=' -> GHC.IO.Handle.Text.hPutStr2 GHC.IO.Handle.FD.stdout lvl16_r3UJ GHC.Types.True w_s3TA; '@' -> GHC.IO.Handle.Text.hPutStr2 GHC.IO.Handle.FD.stdout lvl18_r3UL GHC.Types.True w_s3TA; '_' -> GHC.IO.Handle.Text.hPutStr2 GHC.IO.Handle.FD.stdout lvl20_r3UN GHC.Types.True w_s3TA; '~' -> GHC.IO.Handle.Text.hPutStr2 GHC.IO.Handle.FD.stdout lvl22_r3UP GHC.Types.True w_s3TA } }}} This seems to be sub-optimal for instruction cache efficiency, the number of branches in generated machine code, code size, and understandability of the resulting Core. I would have expected something like, ```#!hs f x = let p = pred x in case p of True -> do_something False -> do_something_else ``` -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10120> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10125: Inproper evaluation of type families
by GHC 02 Mar '15

02 Mar '15

#10125: Inproper evaluation of type families -------------------------------------+------------------------------------- Reporter: danilo2 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.4 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Hello! I've got here a small piece of code: {{{#!haskell {-# LANGUAGE DeriveDataTypeable #-} {-# LANGUAGE EmptyDataDecls #-} {-# LANGUAGE DataKinds #-} {-# LANGUAGE PolyKinds #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE TypeOperators #-} {-# LANGUAGE UndecidableInstances #-} module Data.TypeLevel.Bool where import Prelude hiding (Eq) import qualified Prelude as P import Data.Typeable import GHC.TypeLits type family Eq (a :: k) (b :: k) where Eq a a = True Eq a b = False type family If (cond :: Bool) (a :: k) (b :: k) where If True a b = a If False a b = b type family CmpBy (f :: k -> k -> Ordering) (a :: [k]) (b :: [k]) :: Ordering where CmpBy f '[] '[] = EQ CmpBy f (a ': as) (b ': bs) = If (Eq (f a b) EQ) (CmpBy f as bs) (f a b) type family TCompare (a :: [Nat]) (b :: [Nat]) :: Ordering where TCompare '[] '[] = EQ TCompare (a ': as) (b ': bs) = If (Eq a b) (TCompare as bs) (CmpNat a b) type N1 = '[1,2,3,5] type N2 = '[1,2,3,4] main = do print $ (Proxy :: Proxy GT) == (Proxy :: Proxy (TCompare N1 N2)) print $ (Proxy :: Proxy GT) == (Proxy :: Proxy (CmpBy CmpNat N1 N2)) }}} It does NOT compile, while it should. The type-level functions `TCompare` and `CmpBy CmpNat` should work exactly the same way. Right now the former one always returns `EQ`, so the program does not compile with an error: {{{ Bool.hs:49:41: Couldn't match type ‘'EQ’ with ‘'GT’ Expected type: Proxy (CmpBy CmpNat N1 N2) Actual type: Proxy 'GT In the second argument of ‘(==)’, namely ‘(Proxy :: Proxy (CmpBy CmpNat N1 N2))’ In the second argument of ‘($)’, namely ‘(Proxy :: Proxy GT) == (Proxy :: Proxy (CmpBy CmpNat N1 N2))’ }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10125> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10005: Operations on string literals won't be inlined
by GHC 02 Mar '15

02 Mar '15

#10005: Operations on string literals won't be inlined -------------------------------------+------------------------------------- Reporter: fread2281 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.4 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- An example is attached, GHC won't optimize {{{ head "stringliteral" }}} into {{{ 's' }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10005> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10024: This bug tracker: Can not create filter `x contains y && x contains z`
by GHC 02 Mar '15

02 Mar '15

#10024: This bug tracker: Can not create filter `x contains y && x contains z` -------------------------------------+------------------------------------- Reporter: lspitzner | Owner: hvr Type: bug | Status: new Priority: normal | Milestone: Component: Trac & Git | Version: Keywords: trac | Operating System: Unknown/Multiple filter and | Type of failure: None/Unknown Architecture: Other | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- To Reproduce: - Start ticket search - Create filter "description" and set phrase to "foo" - Click the button "And" again, choose "description", set phrase to "bar" - The filter now is set to {{{description contains foo || description contains bar}}}, instead of the expected {{{s/||/&&/}}}. Note that setting phrase to "foo bar" seems to search for "foo bar", not {{{fold (||) . words}}}. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10024> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10025: Tracker: "My Tickets" does not work
by GHC 02 Mar '15

02 Mar '15

#10025: Tracker: "My Tickets" does not work -------------------------------------+------------------------------------- Reporter: lspitzner | Owner: hvr Type: bug | Status: new Priority: high | Milestone: Component: Trac & Git | Version: Keywords: trac my | Operating System: Unknown/Multiple tickets filter | Type of failure: None/Unknown Architecture: | Blocked By: Unknown/Multiple | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- I have non-zero set of tickets here, yet search returns empty list. No filters other than author=lspitzner. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10025> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9328: MINIMAL pragma should supprt negation
by GHC 02 Mar '15

02 Mar '15

#9328: MINIMAL pragma should supprt negation -------------------------------------+------------------------------------- Reporter: augustss | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Keywords: | Differential Revisions: Operating System: Unknown/Multiple | Architecture: Type of failure: None/Unknown | Unknown/Multiple Test Case: | Difficulty: Unknown Blocking: | Blocked By: | Related Tickets: -------------------------------------+------------------------------------- Consider this class declaration {{{ class Conv a where to :: Integer -> a from :: a -> Integer default to :: (Generic a) => Integer -> a to i = ... default from :: (Generic a) => a -> Integer from a = ... }}} The class provides default methods for the two methods using generics. An instance declaration for this type is likely to want to use the default for both methods or for none. So I'd like a MINIMAL pragma that can express this. E.g. {{{ {-# MINIMAL (to, from) | (!to, !from) #-} }}} I've used ! for negation (following the lead set by the MINIMAL pragma using a non-Haskell OR operator), so this says: either implement 'to' and 'from' or don't implement neither 'to' nor 'from'. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9328> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7828: RebindableSyntax and Arrow
by GHC 02 Mar '15

02 Mar '15

#7828: RebindableSyntax and Arrow -------------------------------------+------------------------------------- Reporter: | Owner: AlessandroVermeulen | Status: new Type: bug | Milestone: 7.12.1 Priority: normal | Version: 7.6.2 Component: Compiler (Type | Keywords: checker) | Architecture: Resolution: | Unknown/Multiple Operating System: Unknown/Multiple | Test Case: Type of failure: GHC rejects | Blocking: valid program | Differential Revisions: Phab:D72 Blocked By: | Related Tickets: #1537, #3613 | -------------------------------------+------------------------------------- Comment (by simonpj): It's stalled. The honest truth is: * No one knows about both GHC and arrows in enough detail to make progress. * I'm willing to support * But it really needs someone who cares about arrows to pay sustained attention. Maybe you? * comment:46 suggests the next steps Simon -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7828#comment:54> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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