March 2016 - ghc-tickets

[GHC] #11656: Alllow static pointers to local closed definitions
by GHC 29 Nov '16

29 Nov '16

#11656: Alllow static pointers to local closed definitions -------------------------------------+------------------------------------- Reporter: mboes | 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: -------------------------------------+------------------------------------- A limitation of the original patch implementing `-XStaticPointers` is that while the following all work, {{{#!hs t1 = static not t2 = static (\x -> case x of True -> False; False -> True) }}} the below does not: {{{#!hs t3 = static foo where foo True = False }}} Yet `foo` is perfectly "static": it's a closed expression that can readily be floated to top-level. So in short: `-XStaticPointers` should not consider only expressions with top-level identifiers, but in general any closed expression (which may involve local closed identifiers too). -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11656> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11158: Combine exprIsTrivial and cpe_ExprIsTrivial
by GHC 25 Nov '16

25 Nov '16

#11158: Combine exprIsTrivial and cpe_ExprIsTrivial -------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 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: -------------------------------------+------------------------------------- Look at `CoreUtils.exprIsTrivial` and `CorePrep.cpe_ExprIsTrivial`. They are identical! The latter has a comment saying {{{ cpe_ExprIsTrivial :: CoreExpr -> Bool -- Version that doesn't consider an scc annotation to be trivial. }}} but the code does not treat ticks any differently. So the question is: '''are they supposed to be different'''? And if not, can we just combine them? Peter W, Simon M: this is your territory. I don't understand tick stuff well enough. Simon -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11158> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11575: Program crashes only when compiled via LLVM
by GHC 23 Nov '16

23 Nov '16

#11575: Program crashes only when compiled via LLVM --------------------------------------+---------------------------------- Reporter: Guest00000 | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: None | Version: 7.10.3 Keywords: llvm | Operating System: Windows Architecture: x86_64 (amd64) | Type of failure: Runtime crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------------+---------------------------------- `llvm-test.hs`: {{{#!hs import System.IO import Foreign.Storable import Foreign.Marshal.Alloc import Data.Word main = do hSetBuffering stdout NoBuffering test 1000 test 5000 where test n = do allocaBytes (n * 4) $ \p -> do sequence_ [ pokeByteOff p (i * 4) (0x12345678 :: Word32) | i <- [ 0 .. n - 1 ] ] putStrLn $ show n ++ " fine" }}} ---- Cygwin shell: {{{ user@pc ~ $ ghc llvm-test.hs && ./llvm-test.exe [1 of 1] Compiling Main ( llvm-test.hs, llvm-test.o ) Linking llvm-test.exe ... 1000 fine 5000 fine user@pc ~ $ touch llvm-test.hs user@pc ~ $ ghc llvm-test.hs -fllvm && ./llvm-test.exe [1 of 1] Compiling Main ( llvm-test.hs, llvm-test.o ) Linking llvm-test.exe ... 1000 fine Segmentation fault }}} ---- {{{ <erikd> `Guest00000: try adding -O2 to the compiler command line. <`Guest00000> erikd: it now segfaults even before printing "1000 fine" <`Guest00000> wait, one time it printed one character "1" before crashing }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11575> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8300: split-objs doesn't split on LLVM
by GHC 22 Nov '16

22 Nov '16

#8300: split-objs doesn't split on LLVM ------------------------------------+------------------------------------- Reporter: rwbarton | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler (LLVM) | Version: 7.7 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- `-split-objs` is allowed with `-fllvm`, but it doesn't really do anything. E.g. in my perf-llvm build I have a `libHSbase-4.7.0.0.a` with `Applicative__1.o`, `Arrow__1.o` etc. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8300> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11532: ghc: panic! occured
by GHC 19 Nov '16

19 Nov '16

#11532: ghc: panic! occured -------------------------------------+------------------------------------- Reporter: cutsea | 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: -------------------------------------+------------------------------------- I'd like to try install by following: {{{ $ cabal sandbox init $ cabal install metadata Resolving dependencies... Notice: installing into a sandbox located at /home/cutsea110/devel/haskell/sandbox/.cabal-sandbox Configuring metadata-0.4.2.0... Building metadata-0.4.2.0... : : [1036 of 1286] Compiling Text.HTML5.MetaData.Schema.TelevisionStation[boot] ( Text/HTML5/MetaData/Schema/TelevisionStation.hs-boot, dist/dist-sandbox- 304cb20a/build/Text/HTML5/MetaData/Schema/TelevisionStation.o-boot ) [1037 of 1286] Compiling Text.HTML5.MetaData.Schema.TelevisionStation ( Text/HTML5/MetaData/Schema/TelevisionStation.hs, dist/dist-sandbox- 304cb20a/build/Text/HTML5/MetaData/Schema/TelevisionStation.o ) ghc: panic! (the 'impossible' happened) (GHC version 7.10.3 for x86_64-unknown-linux): LocalReg's live-in to graph cpd3t {_sp8MJ::P64} Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug cabal: Error: some packages failed to install: metadata-0.4.2.0 failed during the building phase. The exception was: ExitFailure 1 }}} -- regards. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11532> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8321: improve basic block layout on LLVM backend by predicting stack/heap checks
by GHC 17 Nov '16

17 Nov '16

#8321: improve basic block layout on LLVM backend by predicting stack/heap checks ------------------------------------+------------------------------------- Reporter: rwbarton | Owner: Type: feature request | Status: new Priority: normal | Milestone: 7.10.1 Component: Compiler (LLVM) | Version: 7.7 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- Currently we don't give the LLVM optimizer any information about which branch of an `if` is likely to be taken. As a result, the optimizer is likely to produce a basic block layout which is not optimal. Improving the layout can improve performance through better instruction cache usage and better branch prediction by the hardware. We can control LLVM's idea of what is likely with the `llvm.expect` intrinsic function. Some obvious branches which we can predict accurately are the stack and heap checks that appear near the entry of many functions. Here's a small example of some Cmm code and the output of the LLVM optimizer/compiler. {{{ block_c2Lc_entry() // [R1, R2] { info_tbl: [(c2Lc, label: block_c2Lc_info rep:StackRep [])] stack_info: arg_space: 0 updfr_space: Nothing } {offset c2Lc: Hp = Hp + 24; if (Hp > HpLim) goto c2Lm; else goto c2Ll; c2Lm: HpAlloc = 24; R2 = R2; R1 = R1; call stg_gc_pp(R2, R1) args: 8, res: 8, upd: 24; c2Ll: I64[Hp - 16] = :_con_info; P64[Hp - 8] = R1; P64[Hp] = R2; R1 = Hp - 14; Sp = Sp + 8; call (P64[Sp])(R1) args: 24, res: 0, upd: 24; } }] }}} {{{ 00000000000002b8 <c2Lc_info>: 2b8: 4c 89 e0 mov %r12,%rax 2bb: 4c 8d 60 18 lea 0x18(%rax),%r12 2bf: 4d 3b a5 18 01 00 00 cmp 0x118(%r13),%r12 2c6: 76 10 jbe 2d8 <c2Lc_info+0x20> 2c8: 49 c7 85 48 01 00 00 movq $0x18,0x148(%r13) 2cf: 18 00 00 00 2d3: e9 00 00 00 00 jmpq 2d8 <c2Lc_info+0x20> 2d4: R_X86_64_PC32 stg_gc_pp+0xfffffffffffffffc 2d8: 48 c7 40 08 00 00 00 movq $0x0,0x8(%rax) 2df: 00 2dc: R_X86_64_32S ghczmprim_GHCziTypes_ZC_con_info 2e0: 48 89 58 10 mov %rbx,0x10(%rax) 2e4: 4c 89 70 18 mov %r14,0x18(%rax) 2e8: 48 8b 45 08 mov 0x8(%rbp),%rax 2ec: 48 83 c5 08 add $0x8,%rbp 2f0: 49 8d 5c 24 f2 lea -0xe(%r12),%rbx 2f5: ff e0 jmpq *%rax 2f7: 90 nop }}} It would likely be better to invert the branch at `2c6` to a `ja`, so that the common case is adjacent to the function entry, and when `llvm.expect` is used on the condition in the branch, the LLVM optimizer does produce this alternate layout. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8321> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9940: GHCi crashes when I hold down control-c for a short time, and then hold down any key that would normally result in typing.
by GHC 16 Nov '16

16 Nov '16

#9940: GHCi crashes when I hold down control-c for a short time, and then hold down any key that would normally result in typing. -------------------------------------------+------------------------------- Reporter: Dingus | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 7.6.3 Keywords: crash, control-c | Operating System: Windows Architecture: x86_64 (amd64) | Type of failure: GHCi crash Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------------+------------------------------- This is printed: (without the quotes at the beginning or end) " ghc.exe: panic! (the 'impossible' happened) (GHC version 7.6.3 for i386-unknown-mingw32): thread blocked indefinitely in an MVar operation Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug " I am able to reproduce it by: 1. starting ghci (with no arguments, or a file as an argument) 2. holding down contol-c for 2 seconds 3. holding down spacebar/a letter key for 2 seconds The timing varies. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9940> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10771: Installation of Ivory - Static flags have not been initialised
by GHC 14 Nov '16

14 Nov '16

#10771: Installation of Ivory - Static flags have not been initialised -------------------------------------+------------------------------------- Reporter: stiege | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.2 Keywords: | Operating System: Unknown/Multiple Architecture: x86_64 | Type of failure: Runtime crash (amd64) | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- Unfortunately I'm a Haskell newbie and can't provide very good detail for this report (I struggled to pass the Captcha!). However I will attach the output from a "make all" from the Ivory repository: https://github.com/GaloisInc/ivory.git Commit: '7ecea5839898b65430ca298fd1f3af4d2272e3fb'. Basically from what I can see, looks like it didn't work, output ends with: examples\Coroutine.hs:26:50: Warning: Unticked promoted constructor: `:->'. Use ':-> instead of `:->'. ghc.exe: panic! (the 'impossible' happened) (GHC version 7.10.2 for x86_64-unknown-mingw32): Static flags have not been initialised! Please call GHC.parseStaticFlags early enough. Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug ghc.exe: warning: _tzset from msvcrt is linked instead of __imp__tzset -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10771> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11660: Remove Type pretty-printer in favor of IfaceType
by GHC 13 Nov '16

13 Nov '16

#11660: Remove Type pretty-printer in favor of IfaceType -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: task | 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: -------------------------------------+------------------------------------- The `Type` pretty-printer has a fair amount of code in common with the pretty-printer for `IfaceType`. Moreover, both cases handle a number of special cases. With the introduction of `-fprint-explicit-runtime-reps` (Phab:D1961), there is now an inconsistency between these two. Let's resolve this inconsistency by eliminating the `Type` pretty-printer in favor of using the `IfaceType` printer. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11660> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11369: Suppress redundant-constraint warnings in case of empty classes
by GHC 07 Nov '16

07 Nov '16

#11369: Suppress redundant-constraint warnings in case of empty classes -------------------------------------+------------------------------------- Reporter: hvr | Owner: simonpj Type: bug | Status: new Priority: highest | Milestone: 8.0.1 Component: Compiler | Version: 8.1 (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: -------------------------------------+------------------------------------- The technique described in http://www.well-typed.com/blog/2015/07/checked-exceptions/ makes use of a class without any methods, i.e. {{{#!hs class Throws e }}} However, this by definition results in redundant constraints, e.g. {{{#!hs readFoo :: Throws IOError => FilePath -> IO Foo readFoo fn = {- ... -} }}} which GHC 8.0 warns about. I propose to suppress warnings in case a class which has no methods is used as seemingly redundant constraint. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11369> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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