May 2018 - ghc-tickets

[GHC] #15104: Update JMP_TBL targets during shortcutting for x86 codegen.
by GHC 31 May '18

31 May '18

#15104: Update JMP_TBL targets during shortcutting for x86 codegen. -------------------------------------+------------------------------------- Reporter: AndreasK | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.5 (NCG) | Keywords: CodeGen | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): Phab:D4595 | Wiki Page: -------------------------------------+------------------------------------- Jump tables are generated from Cmm Code in a few steps: 1. We start with a CmmSwitch at the end of the Cmm pipeline which gets turned into a JMP_TBL instruction. 2. During native codegen we generate static jump tables from JMP_TBL. (generateJumpTables) 3. We shortcut jump targets, for jump tables by updating the static tables. (shortcutBranches). This might update the jump targets with calculated address not represented by a label. After the third step the targets in the JMP_TBL instruction (which are the original labels) and in the static data can be out of sync. Phab:D4566 went part of the way, updating labels in JMP_TBL. However without tables next to code labels can be updated to non-label jump destinations which I did not consider at the time. Phab:D4595 is intended to fix this. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15104> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7411: Exceptions are optimized away in certain situations
by GHC 31 May '18

31 May '18

#7411: Exceptions are optimized away in certain situations -------------------------------------+------------------------------------- Reporter: SimonHengel | Owner: tdammers Type: bug | Status: new Priority: high | Milestone: 8.6.1 Component: Compiler | Version: 7.6.1 Resolution: | Keywords: seq, deepseq, | evaluate, exceptions Operating System: Linux | Architecture: x86_64 | (amd64) Type of failure: Incorrect result | Test Case: at runtime | simplCore/should_fail/T7411 Blocked By: | Blocking: Related Tickets: #5129 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by tdammers): Pinging simonpj: do you think we need more data than this before deciding to remove the state hack, or at least make `-fno-state-hack` the default? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7411#comment:33> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9479: Report required constraints when reporting the type of a hole
by GHC 31 May '18

31 May '18

#9479: Report required constraints when reporting the type of a hole -------------------------------------+------------------------------------- Reporter: dominiquedevriese | Owner: Type: feature request | Status: new Priority: low | Milestone: Component: Compiler (Type | Version: 7.8.3 checker) | Operating System: Keywords: holes | Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: Difficulty: Unknown | None/Unknown Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- For the following code {{{ module Test where test :: String test = show _h }}} GHC currently reports: {{{ Found hole ‘_h’ with type: a0 Where: ‘a0’ is an ambiguous type variable Relevant bindings include test :: String (bound at /tmp/Test.hs:4:1) In the first argument of ‘show’, namely ‘_h’ In the expression: show _h In an equation for ‘test’: test = show _h }}} It correctly does not report the lack of a `Show _a` instance as a separate type error. However, it would be useful if the report containing the type of the hole would also contain the constraints that apply to its type. Something like: {{{ Found hole ‘_h’ with type: a0 Where: ‘a0’ is an ambiguous type variable Applicable constraints: Show a0 Relevant bindings include test :: String (bound at /tmp/Test.hs:4:1) In the first argument of ‘show’, namely ‘_h’ In the expression: show _h In an equation for ‘test’: test = show _h }}} I am explicitly *not* suggesting to report a type like `Show a0 => a0` for the hole, because that might mistakenly suggest that we are looking for a value of type `forall a0. Show a0 => a0`, which we are not. A possible alternative is to use an imaginary exists type like `exists a0. Show a0 => a0` but that's probably just even more confusing. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9479> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15157: Use a better string type (ByteString?!) for HsDocString
by GHC 31 May '18

31 May '18

#15157: Use a better string type (ByteString?!) for HsDocString -------------------------------------+------------------------------------- Reporter: sjakobi | Owner: (none) Type: task | Status: new Priority: normal | Milestone: 8.6.1 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: -------------------------------------+------------------------------------- `HsDocString` is currently defined as {{{ newtype HsDocString = HsDocString FastString }}} Alex Biehl and hvr mentioned that due to `FastString`'s (interning?) overhead it's not a good type to store haddocks. They suggested using `ByteString` instead. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15157> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15197: Apparent missing dependency in ghc-heap
by GHC 31 May '18

31 May '18

#15197: Apparent missing dependency in ghc-heap -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: new Priority: highest | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 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: -------------------------------------+------------------------------------- The `ghc-heap` library appears to be missing a dependency from `GHC.Exts.Heap.Closures` to `GHC.Exts.Heap.InfoTableProf`. This causes the vanilla build to fail (in particular when building the profiled way): {{{ “inplace/bin/ghc-stage1” -hisuf p_hi -osuf p_o -hcsuf p_hc -static -prof -eventlog -H32m -O -Wall -this-unit-id ghc-heap-8.5 -hide-all- packages -i -ilibraries/ghc-heap/. -ilibraries/ghc-heap/dist-install/build -Ilibraries/ghc-heap/dist-install/build -ilibraries/ghc-heap/dist- install/build/./autogen -Ilibraries/ghc-heap/dist-install/build/./autogen -Ilibraries/ghc-heap/. -optP-include -optPlibraries/ghc-heap/dist- install/build/./autogen/cabal_macros.h -package-id base-4.12.0.0 -package- id ghc-prim-0.5.3 -package-id rts -Wall -XHaskell2010 -O2 -no-user- package-db -rtsopts -Wno-deprecated-flags -Wnoncanonical-monad- instances -odir libraries/ghc-heap/dist-install/build -hidir libraries /ghc-heap/dist-install/build -stubdir libraries/ghc-heap/dist- install/build -c libraries/ghc-heap/./GHC/Exts/Heap/Closures.hs -o libraries/ghc-heap/dist-install/build/GHC/Exts/Heap/Closures.p_o -dyno libraries/ghc-heap/dist- install/build/GHC/Exts/Heap/Closures.dyn_olibraries/ghc- heap/GHC/Exts/Heap/Closures.hs:23:1: error: Could not find module ‘GHC.Exts.Heap.InfoTableProf’ It is a member of the hidden package ‘ghc-heap-8.5’. You can run ‘:set -package ghc-heap’ to expose it. (Note: this unloads all the modules in the current scope.) Use -v to see a list of the files searched for. | 23 | import GHC.Exts.Heap.InfoTableProf | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ }}} Building the `libraries/ghc-heap/dist- install/GHC/Exts/Heap/InfoTableProf.p_o` manually allows the build to proceed. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15197> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15088: Test T3234 is fragile
by GHC 31 May '18

31 May '18

#15088: Test T3234 is fragile -------------------------------------+------------------------------------- Reporter: mpickering | Owner: (none) Type: task | Status: new Priority: lowest | Milestone: 8.6.1 Component: Compiler | Version: 8.2.2 Keywords: newcomer | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The test for T3234 is quite fragile as it compares the whole output of `-ddump-simpl-stats`. #3234 should be consulted and then the test modified so that only the relevant part is extracted and compared. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15088> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #15198: `Language.Haskell.TH.Syntax.reify` returns * rather than Constraint
by GHC 31 May '18

31 May '18

#15198: `Language.Haskell.TH.Syntax.reify` returns * rather than Constraint -------------------------------------+------------------------------------- Reporter: benzrf | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.4.4 Component: Template | Version: 8.4.2 Haskell | Keywords: reify | Operating System: Linux constraint constraintkinds | Architecture: x86_64 | Type of failure: Incorrect result (amd64) | at runtime Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This module is sufficient to demonstrate the mistake: {{{#!hs {-# LANGUAGE ConstraintKinds #-} {-# LANGUAGE KindSignatures #-} {-# LANGUAGE RankNTypes #-} {-# LANGUAGE TemplateHaskell #-} module Bug where import Data.Kind import Data.Proxy import Language.Haskell.TH foo :: forall (k :: Constraint). Proxy k foo = Proxy return [] -- delimit declaration groups main :: IO () main = putStrLn $(do VarI _ ty _ <- reify 'foo let p = pprint ty [| p |]) }}} Running this in GHC 8.0.2 correctly prints out `forall (k_0 :: Constraint) . Data.Proxy.Proxy k_0`, but GHC 8.2.2 and 8.4.2 both print `forall (k_0 :: *) . Data.Proxy.Proxy k_0`. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15198> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12567: `ghc --make` recompiles unchanged files when using `-fplugin` OPTIONS
by GHC 30 May '18

30 May '18

#12567: `ghc --make` recompiles unchanged files when using `-fplugin` OPTIONS -------------------------------------+------------------------------------- Reporter: heisenbug | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 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: -------------------------------------+------------------------------------- Consider this bare-bones module {{{#!hs {-# OPTIONS -fplugin GHC.TypeLits.Normalise #-} module A where }}} compiling it will always say {{{ $ ghc --make A.hs [1 of 1] Compiling A ( A.hs, A.o ) [GHC.TypeLits.Normalise changed] }}} even when the module was compiled before. {{{ $ ghc A.hs -c -ddump-if-trace -ddump-hi-diffs }}} will give the reason: {{{ imported module ‘GHC.TypeLits.Normalise’ is from package ‘ghc-typelits- natnormalise-0.5’, which is not among previous dependencies }}} Which is the probable cause: when writing the `.hi` file, the used plugins' package dependencies should be also written out. AFAICS they are extracted fron the `DynFlags` but for this comparison in {{{ checkDependencies :: HscEnv -> ModSummary -> ModIface -> IfG RecompileRequired }}} but not found in the `ModSummary` that was originally written to disk. This is pretty nasty for `clash` compilations and the suspected bug is documented here: https://github.com/clash-lang/ghc-typelits- natnormalise/issues/2 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12567> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #7414: plugins always trigger recompilation
by GHC 30 May '18

30 May '18

#7414: plugins always trigger recompilation -------------------------------------+------------------------------------- Reporter: jwlato | Owner: (none) Type: feature request | Status: closed Priority: high | Milestone: 8.6.1 Component: Compiler | Version: 7.6.1 Resolution: fixed | Keywords: plugin, | RecompilationCheck Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: #12567 | Differential Rev(s): Phab:D4366 Wiki Page: | -------------------------------------+------------------------------------- Changes (by bgamari): * status: patch => closed * resolution: => fixed -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7414#comment:18> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #108: Header files from f.i. not propagated to non-local inlining
by GHC 30 May '18

30 May '18

#108: Header files from f.i. not propagated to non-local inlining --------------------------------+-------------------- Reporter: nhn | Owner: nobody Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 5.04.2 Resolution: Fixed | Keywords: Type of failure: None/Unknown | --------------------------------+-------------------- Changes (by Ben Gamari <ben@…>): * failure: => None/Unknown Comment: In [changeset:"1d1e2b77fdc2babdf4fff72b9120c6831e7b422f/ghc" 1d1e2b7/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="1d1e2b77fdc2babdf4fff72b9120c6831e7b422f" Implement "An API for deciding whether plugins should cause recompilation" This patch implements the API proposed as pull request #108 for plugin authors to influence the recompilation checker. It adds a new field to a plugin which computes a `FingerPrint`. This is recorded in interface files and if it changes then we recompile the module. There are also helper functions such as `purePlugin` and `impurePlugin` for constructing plugins which have simple recompilation semantics but in general, an author can compute a hash as they wish. Fixes #12567 and #7414 https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/002 2-plugin-recompilation.rst Reviewers: bgamari, ggreif Reviewed By: bgamari Subscribers: rwbarton, thomie, carter GHC Trac Issues: #7414, #12567 Differential Revision: https://phabricator.haskell.org/D4366 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/108#comment:5> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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