February 2018 - ghc-tickets

[GHC] #14814: -g causes "cc failed in phase Assembler" in yaml package
by GHC 16 Feb '18

16 Feb '18

#14814: -g causes "cc failed in phase Assembler" in yaml package -------------------------------------+------------------------------------- Reporter: Fuuzetsu | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 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: -------------------------------------+------------------------------------- {{{#!bash git clone https://github.com/snoyberg/yaml cd yaml git checkout yaml-0.8.28 stack build yaml --resolver=lts-10.5 --ghc-options='-g' }}} With this I get (I'm using nix below but should be irrelevant): {{{ [nix-shell:~/programming/yaml]$ stack build yaml --nix -j1 --resolver=lts-10.5 --ghc-options='-g' raw-strings-qq-1.1: download raw-strings-qq-1.1: configure raw-strings-qq-1.1: build raw-strings-qq-1.1: copy/register Building all executables for `yaml' once. After a successful build of all of them, only specified executables will be rebuilt. yaml-0.8.28: configure (lib + exe) Configuring yaml-0.8.28... yaml-0.8.28: build (lib + exe) Preprocessing library for yaml-0.8.28.. Building library for yaml-0.8.28.. [ 1 of 10] Compiling Text.Libyaml ( Text/Libyaml.hs, .stack- work/dist/x86_64-linux-nix/Cabal-2.0.1.0/build/Text/Libyaml.o ) [ 2 of 10] Compiling Data.Yaml.Parser ( Data/Yaml/Parser.hs, .stack- work/dist/x86_64-linux-nix/Cabal-2.0.1.0/build/Data/Yaml/Parser.o ) [ 3 of 10] Compiling Data.Yaml.Internal ( Data/Yaml/Internal.hs, .stack- work/dist/x86_64-linux-nix/Cabal-2.0.1.0/build/Data/Yaml/Internal.o ) /run/user/1000/ghc25193_0/ghc_30.s: Assembler messages: /home/shana/programming/yaml//run/user/1000/ghc25193_0/ghc_30.s:67519:0: error: Error: can't resolve `.Lc1azh_entry_end' {*UND* section} - `c1azh_entry' {*UND* section} | 67519 | .quad .Lc1azh_entry_end-c1azh_entry | ^ `cc' failed in phase `Assembler'. (Exit code: 1) Progress: 1/2 -- While building custom Setup.hs for package yaml-0.8.28 using: /home/shana/.stack/setup-exe-cache/x86_64-linux-nix/Cabal- simple_mPHDZzAJ_2.0.1.0_ghc-8.2.2 --builddir=.stack-work/dist/x86_64 -linux-nix/Cabal-2.0.1.0 build lib:yaml exe:examples exe:json2yaml exe:yaml2json --ghc-options " -ddump-hi -ddump-to-file -fdiagnostics- color=always" Process exited with code: ExitFailure 1 Completed 2 action(s). }}} {{{ $ uname -a Linux kagami 4.14.12 #1-NixOS SMP Fri Jan 5 14:48:59 UTC 2018 x86_64 GNU/Linux }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14814> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13943: Compiler infinite loop with GHC-8.2
by GHC 15 Feb '18

15 Feb '18

#13943: Compiler infinite loop with GHC-8.2 -------------------------------------+------------------------------------- Reporter: vagarenko | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.2.1 Component: Compiler | Version: 8.2.1-rc3 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: -------------------------------------+------------------------------------- GHC-8.0.1 compile this module in less than one seconds on my machine. Both GHC-8.2rc2 and GHC-8.2rc3 eat all 8GB of memory and don't show any signs of stopping. -dshow-passes shows this: {{{ [1 of 1] Compiling Data.List.Unrolled ( unrolled.hs, unrolled.o ) *** Parser [Data.List.Unrolled]: !!! Parser [Data.List.Unrolled]: finished in 0.00 milliseconds, allocated 3.434 megabytes *** Renamer/typechecker [Data.List.Unrolled]: }}} and then nothing. Only memory consumption grows. Code: {{{#!hs {-# LANGUAGE MultiParamTypeClasses #-} {-# LANGUAGE TypeOperators #-} {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE FlexibleContexts #-} {-# LANGUAGE ScopedTypeVariables #-} {-# LANGUAGE UndecidableInstances #-} {-# LANGUAGE TypeApplications #-} {-# LANGUAGE TypeInType #-} {-# LANGUAGE AllowAmbiguousTypes #-} {-# LANGUAGE NoImplicitPrelude #-} {-# LANGUAGE GADTs #-} module Data.List.Unrolled where import GHC.TypeLits -- | Drop @n@ elements from a list class Drop (n :: Nat) where drop :: [a] -> [a] instance {-# OVERLAPPING #-} Drop 0 where drop xs = xs {-# INLINE drop #-} instance {-# OVERLAPPABLE #-} (Drop (n - 1)) => Drop n where drop [] = [] drop (_ : xs) = drop @(n - 1) xs {-# INLINE drop #-} -- | Take @n@ elements from a list class Take (n :: Nat) where take :: [a] -> [a] instance {-# OVERLAPPING #-} Take 0 where take _ = [] {-# INLINE take #-} instance {-# OVERLAPPABLE #-} (Take (n - 1)) => Take n where take [] = [] take (x : xs) = x : take @(n - 1) xs {-# INLINE take #-} -- | Split list at @n@-th element. splitAt :: forall (n :: Nat) a. (Take n, Drop n) => [a] -> ([a], [a]) splitAt xs = (take @n xs, drop @n xs) -- | Split list into chunks of the given length @c@. @n@ is length of the list. class ChunksOf (n :: Nat) (c :: Nat) where chunksOf :: [a] -> [[a]] instance {-# OVERLAPPING #-} ChunksOf 0 0 where chunksOf _ = [] {-# INLINE chunksOf #-} instance {-# OVERLAPPABLE #-} ChunksOf 0 c where chunksOf _ = [] {-# INLINE chunksOf #-} instance {-# OVERLAPPABLE #-} ChunksOf n 0 where chunksOf _ = [] {-# INLINE chunksOf #-} instance {-# OVERLAPPABLE #-} (Take c, Drop c, ChunksOf (n - 1) c) => ChunksOf n c where chunksOf xs = let (l, r) = splitAt @c xs in l : chunksOf @(n - 1) @c r {-# INLINE chunksOf #-} }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13943> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14790: eqTypeRep does not inline
by GHC 15 Feb '18

15 Feb '18

#14790: eqTypeRep does not inline -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.1-alpha2 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: -------------------------------------+------------------------------------- GHC never seems to inline `eqTypeRep`. That's no good! It produces a `Maybe`, which users will almost certainly want to match on immediately. I really don't understand ''why'' it doesn't inline. It's a tiny function, none of the functions it calls are themselves marked `INLINE`, and the advantage to inlining seems obvious. Does the `unsafeCoerce` get in the way somehow? If so, how can we fix it? Example: {{{#!hs {-# language GADTs, ScopedTypeVariables, TypeApplications #-} module Foo where import Type.Reflection foo :: forall proxy a. Typeable a => proxy a -> Bool foo _ = case eqTypeRep (typeRep @a) (typeRep @Int) of Just _ -> True Nothing -> False }}} compiles (with `-O2`) to {{{ foo = \ (@ (proxy_a6tT :: * -> *)) (@ a_a6tU) ($dTypeable_a6tW :: Typeable a_a6tU) -> let { lvl_s6Sc :: Maybe (a_a6tU :~~: Int) [LclId] lvl_s6Sc = eqTypeRep @ * @ * @ a_a6tU @ Int ($dTypeable_a6tW `cast` (base-4.11.0.0:Data.Typeable.Internal.N:Typeable[0] <*>_N <a_a6tU>_N :: (Typeable a_a6tU :: Constraint) ~R# (TypeRep a_a6tU :: *))) Foo.foo1 } in \ _ [Occ=Dead] -> case lvl_s6Sc of { Nothing -> GHC.Types.False; Just ds1_d6Rq -> GHC.Types.True } }}} For reference, `eqTypeRep` is defined like this: {{{#!hs eqTypeRep :: forall k1 k2 (a :: k1) (b :: k2). TypeRep a -> TypeRep b -> Maybe (a :~~: b) eqTypeRep a b | typeRepFingerprint a == typeRepFingerprint b = Just (unsafeCoerce HRefl) | otherwise = Nothing }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14790> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #6087: Join points need strictness analysis
by GHC 15 Feb '18

15 Feb '18

#6087: Join points need strictness analysis -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: bug | Status: infoneeded Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 7.4.1 Resolution: | Keywords: JoinPoints 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: | -------------------------------------+------------------------------------- Comment (by osa1): > comment:12 of #5075 identifies three more tickets that claim to benefit from late-dmd-anal. Let's see if they do. One of those tickets is the current ticket. I updated #5302. I checked #6070 but late demand analysis didn't make any difference in the example functions `h` and `c` shown in the ticket. I don't know how to generated the `CPR2.c_go2`, the ticket is missing that detail. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/6087#comment:29> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5302: Unused arguments in join points
by GHC 15 Feb '18

15 Feb '18

#5302: Unused arguments in join points -------------------------------------+------------------------------------- Reporter: reinerp | Owner: simonpj Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 7.0.3 Resolution: | Keywords: JoinPoints 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 osa1): * Attachment "Unboxed_stock.dump-stg" added. Unboxed.hs, default -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5302> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5302: Unused arguments in join points
by GHC 15 Feb '18

15 Feb '18

#5302: Unused arguments in join points -------------------------------------+------------------------------------- Reporter: reinerp | Owner: simonpj Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 7.0.3 Resolution: | Keywords: JoinPoints 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 osa1): * Attachment "Unboxed_late_dmd.dump-stg" added. Unboxed.hs, late demand analysis -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5302> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5302: Unused arguments in join points
by GHC 15 Feb '18

15 Feb '18

#5302: Unused arguments in join points -------------------------------------+------------------------------------- Reporter: reinerp | Owner: simonpj Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 7.0.3 Resolution: | Keywords: JoinPoints 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: | -------------------------------------+------------------------------------- Comment (by osa1): Just tried with GHC HEAD. Late demand analysis removes unused join point argument. {{{ let-no-escape { $j_s4wc [Occ=Once*!T[2], Dmd=<C(C(S)),1*C1(C1(U(U,U)))>] :: GHC.Prim.Int# -> GHC.Types.Int -> (# Unboxed.FingerTree Unboxed.Size (Unboxed.Node Unboxed.Size c_s44z), Unboxed.FingerTree Unboxed.Size (Unboxed.Node Unboxed.Size c_s44z) #) [LclId[JoinId(2)], Arity=2, Str=<S,U><L,A>, Unf=OtherCon []] = ... }}} After: {{{ let-no-escape { $w$j_s4BK [InlPrag=NOUSERINLINE[0], Occ=Once*!T[1], Dmd=<C(S),1*C1(U(U,U))>] :: GHC.Prim.Int# -> (# Unboxed.FingerTree Unboxed.Size (Unboxed.Node Unboxed.Size c_s45o), Unboxed.FingerTree Unboxed.Size (Unboxed.Node Unboxed.Size c_s45o) #) [LclId[JoinId(1)], Arity=1, Str=<S,U>, Unf=OtherCon []] = ... }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5302#comment:17> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #6070: Fun with the demand analyser
by GHC 15 Feb '18

15 Feb '18

#6070: Fun with the demand analyser -------------------------------------+------------------------------------- Reporter: simonpj | Owner: simonpj Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.4.1 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: | -------------------------------------+------------------------------------- Comment (by osa1): Just tried with GHC HEAD, unused arg in join point in `Unboxed.hs` vanishes with late demand analysis. {{{ let-no-escape { $j_s4wc [Occ=Once*!T[2], Dmd=<C(C(S)),1*C1(C1(U(U,U)))>] :: GHC.Prim.Int# -> GHC.Types.Int -> (# Unboxed.FingerTree Unboxed.Size (Unboxed.Node Unboxed.Size c_s44z), Unboxed.FingerTree Unboxed.Size (Unboxed.Node Unboxed.Size c_s44z) #) [LclId[JoinId(2)], Arity=2, Str=<S,U><L,A>, Unf=OtherCon []] = ... }}} After: {{{ let-no-escape { $w$j_s4BK [InlPrag=NOUSERINLINE[0], Occ=Once*!T[1], Dmd=<C(S),1*C1(U(U,U))>] :: GHC.Prim.Int# -> (# Unboxed.FingerTree Unboxed.Size (Unboxed.Node Unboxed.Size c_s45o), Unboxed.FingerTree Unboxed.Size (Unboxed.Node Unboxed.Size c_s45o) #) [LclId[JoinId(1)], Arity=1, Str=<S,U>, Unf=OtherCon []] = ... }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/6070#comment:9> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #6087: Join points need strictness analysis
by GHC 15 Feb '18

15 Feb '18

#6087: Join points need strictness analysis -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: bug | Status: infoneeded Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 7.4.1 Resolution: | Keywords: JoinPoints 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 osa1): * Attachment "Main_late_dmd.dump-stg" added. cse late demand analysis -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/6087> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #6087: Join points need strictness analysis
by GHC 15 Feb '18

15 Feb '18

#6087: Join points need strictness analysis -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: bug | Status: infoneeded Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 7.4.1 Resolution: | Keywords: JoinPoints 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 osa1): * Attachment "Main_stock.dump-stg" added. cse -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/6087> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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