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Re: [GHC] #2988: Improve float-in
by GHC 22 Jan '18

22 Jan '18

#2988: Improve float-in -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: task | Status: new Priority: lowest | Milestone: Component: Compiler | Version: 6.10.1 Resolution: | Keywords: FloatInwards Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by simonpj): * keywords: => FloatInwards Comment: No it's not fixed. Here's a concrete test case {{{ module T2988 where foo :: Int -> Bool -> String foo y b = let x1 = y+1 x2 = x1 : [] x3 = 1 : x2 x4 = 2 : x3 x5 = 3 : x4 x6 = 4 : x5 in case b of True -> show x6 False -> show (reverse x6) }}} We get a cascade of one-at-a-time inlinings. Horrid. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/2988#comment:18> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #6087: Join points need strictness analysis
by GHC 22 Jan '18

22 Jan '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 simonpj): Huh. We have a flag `-flate-dmd-anal`, but it does not seem to be enabled by `-O` or `-O2`. Could someone do a nofib run to see if it makes a difference? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/6087#comment:15> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14692: Deriving Show with -XEmptyDataDeriving cases on the wrong argument
by GHC 22 Jan '18

22 Jan '18

#14692: Deriving Show with -XEmptyDataDeriving cases on the wrong argument -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.4.1 Component: Compiler | Version: 8.4.1-alpha1 Keywords: deriving | Operating System: Unknown/Multiple Architecture: | Type of failure: Incorrect result Unknown/Multiple | at runtime Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Running this program in GHC 8.4.1-alpha: {{{#!hs {-# LANGUAGE EmptyDataDeriving #-} {-# OPTIONS_GHC -ddump-deriv #-} module Main (main) where data Empty deriving Show loop :: Empty loop = let x = x in x main :: IO () main = print loop }}} One would expect this to loop infinitely at runtime, but in practice, that is not the case: {{{ $ /opt/ghc/8.4.1/bin/runghc Bug.hs ==================== Derived instances ==================== Derived class instances: instance GHC.Show.Show Main.Empty where GHC.Show.showsPrec z_a1Iu = case z_a1Iu of Derived type family instances: ==================== Filling in method body ==================== GHC.Show.Show [Main.Empty] GHC.Show.show = GHC.Show.$dmshow @(Main.Empty) ==================== Filling in method body ==================== GHC.Show.Show [Main.Empty] GHC.Show.showList = GHC.Show.$dmshowList @(Main.Empty) Bug.hs: Bug.hs:5:21-24: Non-exhaustive patterns in case }}} The `-ddump-deriv` output reveals why: the `showsPrec` implementation for `Empty` is casing on the //precedence// argument, not the actual value of type `Empty`! This results in the non-exhaustive patterns error. This is my fault, so I'll prepare a fix :) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14692> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14206: Add bit deposit and bit extraction primops
by GHC 22 Jan '18

22 Jan '18

#14206: Add bit deposit and bit extraction primops -------------------------------------+------------------------------------- Reporter: newhoggy | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 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: -------------------------------------+------------------------------------- Modern CPUs (on x86, Haswell and newer) have a PDEP instruction for efficient bit deposit and a PEXT instruction for efficient bit extraction. These instructions can be used to implement various data structures. I propose we add the following set of primops {{{#!hs pdep8# :: Word# -> Word# -> Word# pdep16# :: Word# -> Word# -> Word# pdep32# :: Word# -> Word# -> Word# pdep64# :: Word64# -> Word64# -> Word64# pdep# :: Word# -> Word# -> Word# pext8# :: Word# -> Word# -> Word# pext16# :: Word# -> Word# -> Word# pext32# :: Word# -> Word# -> Word# pext64# :: Word64# -> Word64# -> Word64# pext# :: Word# -> Word# -> Word# }}} Each primop compiles into either a single PDEP/PEXT instruction or a call to some fallback function, implemented in C. For reference, see the following library that implements FFI wrapper 32-bit and 64-bit functions for these instructions: https://github.com/haskell-works/hw-prim-bits -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14206> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14635: Double stacktrace with errorWithCallStack
by GHC 22 Jan '18

22 Jan '18

#14635: Double stacktrace with errorWithCallStack -------------------------------------+------------------------------------- Reporter: flip101 | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Documentation | 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: -------------------------------------+------------------------------------- Hello, The documentation of https://hackage.haskell.org/package/base-4.10.0.0/docs/GHC- Stack.html#t:CallStack uses the following code: {{{#!hs errorWithCallStack :: HasCallStack => String -> a errorWithCallStack msg = error (msg ++ "n" ++ prettyCallStack callStack) }}} But this is confusing because now you will get two stacktraces. One from error and one inside error with prettyCallStack. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14635> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9885: ghc-pkg parser eats too much memory
by GHC 22 Jan '18

22 Jan '18

#9885: ghc-pkg parser eats too much memory -------------------------------------+------------------------------------- Reporter: gnezdo | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: ghc-pkg | Version: 7.8.3 Keywords: | Operating System: Linux Architecture: Unknown/Multiple | Type of failure: Runtime Difficulty: Moderate (less | performance bug than a day) | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Revisions: -------------------------------------+------------------------------------- Parsing of spec files in ghc-pkg scales very poorly. The following script demonstrates memory consumption growth as a function of the number of tokens in ld-options (16K leads to ~6G) #!/bin/bash # Demonstrates memory consumption behavior of ghc-pkg as a function of # the number of ld-options arguments. for i in {10..14}; do size=$((1 << $i)) echo $size rm -fr a.packages /usr/bin/ghc-pkg init a.packages cat > a.spec <<EOF name: project id: project license: AllRightsReserved version: 1.0 EOF echo -n ld-options: >> a.spec for i in $(seq 1 $size); do echo -n "x "; done >> a.spec /usr/bin/time /usr/bin/ghc-pkg --global-package-db a.packages register --force a.spec done exit 0 # This was collected with ghc-7.6.3. 7.8.3 fares as badly. % bash a.sh 1024 Reading package info from "a.spec" ... done. 0.03user 0.00system 0:00.03elapsed 97%CPU (0avgtext+0avgdata 17848maxresident)k 0inputs+32outputs (0major+4973minor)pagefaults 0swaps 2048 Reading package info from "a.spec" ... done. 0.09user 0.01system 0:00.10elapsed 99%CPU (0avgtext+0avgdata 60872maxresident)k 0inputs+56outputs (0major+15723minor)pagefaults 0swaps 4096 Reading package info from "a.spec" ... done. 0.41user 0.07system 0:00.49elapsed 99%CPU (0avgtext+0avgdata 294340maxresident)k 0inputs+104outputs (0major+74090minor)pagefaults 0swaps 8192 Reading package info from "a.spec" ... done. 1.72user 0.30system 0:02.04elapsed 99%CPU (0avgtext+0avgdata 1168836maxresident)k 0inputs+192outputs (0major+292716minor)pagefaults 0swaps 16384 Reading package info from "a.spec" ... done. 9.11user 1.38system 0:10.51elapsed 99%CPU (0avgtext+0avgdata 5396932maxresident)k 0inputs+376outputs (0major+1349736minor)pagefaults 0swaps -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9885> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14696: basement package fails to compile
by GHC 22 Jan '18

22 Jan '18

#14696: basement package fails to compile -----------------------------------+---------------------------- Reporter: asyropoulos | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 Keywords: | Operating System: Solaris Architecture: x86 | Type of failure: Other Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -----------------------------------+---------------------------- I have noticed that the basement package faisl to compile on Solaris. However, the following patch solves the problem. diff -Naur basement-0.0.6/Basement/Terminal/Size.hsc basement-0.0.6.new/Basement/Terminal/Size.hsc --- basement-0.0.6/Basement/Terminal/Size.hsc 2017-11-11 19:03:59.000000000 +0000 +++ basement-0.0.6.new/Basement/Terminal/Size.hsc 2018-01-21 15:03:03.899338329 +0000 @@ -20,6 +20,9 @@ #include <windows.h> #elif defined FOUNDATION_SYSTEM_UNIX #include <sys/ioctl.h> +#ifdef __sun +#include <sys/termios.h> +#endif #endif #include <stdio.h> -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14696> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14385: Clarify error message when missing GADTs extension
by GHC 21 Jan '18

21 Jan '18

#14385: Clarify error message when missing GADTs extension -------------------------------------+------------------------------------- Reporter: lyxia | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 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: -------------------------------------+------------------------------------- If we write a GADT declaration and forget to enable `GADTs` we get the following error message: {{{ ww.hs:1:1: error: • Illegal generalised algebraic data declaration for ‘T’ (Use GADTs to allow GADTs) • In the data declaration for ‘T’ }}} It could be made more explicit for new users that the suggestion is to use the '''extension''' `GADTs`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14385> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11645: Heap profiling - hp2ps: samples out of sequence
by GHC 21 Jan '18

21 Jan '18

#11645: Heap profiling - hp2ps: samples out of sequence -------------------------------------+------------------------------------- Reporter: thomie | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Profiling | Version: 8.0.1-rc2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: #664 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- `make TEST=hpc_fork WAY=prof` is failing, but it has nothing to do with `hpc`. {{{ hp2ps: hpc_fork.hp, line 9, samples out of sequence hp2ps error when processing heap profile for hpc_fork }}} hpc_fork.hs: {{{ module main where import system.posix.process import control.concurrent main = do pid1 <- forkprocess $ do threaddelay 100000 pid2 <- forkprocess $ do threaddelay 100000 print () }}} To reproduce: {{{ $ ghc-8.0.1 hpc_fork.hs -fforce-recomp -prof $ ./hpc_fork +RTS -hc $ hp2ps hpc_fork.hp }}} Example hpc_fork.hp: {{{ JOB "hpc_fork +RTS -hc" DATE "Thu Feb 25 22:37 2016" SAMPLE_UNIT "seconds" VALUE_UNIT "bytes" BEGIN_SAMPLE 0.000000 END_SAMPLE 0.000000 BEGIN_SAMPLE 0.005672 END_SAMPLE 0.005672 BEGIN_SAMPLE 0.003167 END_SAMPLE 0.003167 BEGIN_SAMPLE 0.003311 END_SAMPLE 0.003311 }}} This is a regression from 7.10.3. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11645> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14056: Figure out what to do about libffi
by GHC 21 Jan '18

21 Jan '18

#14056: Figure out what to do about libffi -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: task | Status: new Priority: normal | 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: -------------------------------------+------------------------------------- For some platform GHC depends upon `libffi` for foreign call support in the bytecode interpreter. Unfortunately `libffi`'s upstream seems to be unresponsive and there has not been a release in nearly three years. This means that there is currently no release which has, e.g., support for AArch64 and iOS's compact debug information. While we obviously want to avoid shipping our own patched libffi, at this point we are starting to run out of options. Consider options for resolving this. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14056> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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