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Re: [GHC] #4900: DEPENDS pragma
by GHC 18 Nov '14

18 Nov '14

#4900: DEPENDS pragma -------------------------------------+------------------------------------- Reporter: cdsmith | Owner: Type: feature | Status: new request | Milestone: 7.10.1 Priority: normal | Version: Component: Compiler | Keywords: Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: None/Unknown | Test Case: TH_Depends | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by refold): Replying to [comment:71 GregWeber]: > I added the documentation: https://phabricator.haskell.org/D481 Thanks! -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4900#comment:72> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8627: mallocForeignPtrBytes documentation unobvious regarding memory alignment
by GHC 18 Nov '14

18 Nov '14

#8627: mallocForeignPtrBytes documentation unobvious regarding memory alignment ------------------------------------+------------------------------------- Reporter: schernichkin | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Documentation | Version: 7.6.3 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- According to the current documentation: mallocForeignPtr - is equivalent to do { p <- malloc; newForeignPtr finalizerFree p }. It's ok since we can read that the "block of memory is sufficiently aligned" if the mallocBytes function descriprion and newAlignedPinnedByteArray in the function implementation. mallocForeignPtrBytes - "similar to mallocForeignPtr" but will it alloc aligned memory? Internally it uses newPinnedByteArray which implies memory will not be aligned, but does it really makes any sense? Plz correct documentation to make it more obvious. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8627> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5462: Deriving clause for arbitrary classes
by GHC 18 Nov '14

18 Nov '14

#5462: Deriving clause for arbitrary classes -------------------------------------+------------------------------------- Reporter: simonpj | Owner: dreixel Type: feature | Status: patch request | Milestone: 7.10.1 Priority: normal | Version: 7.2.1 Component: Compiler | Keywords: Generics Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: #7346 None/Unknown | Test Case: | Blocking: | Differential Revisions: Phab:D476 | -------------------------------------+------------------------------------- Comment (by dreixel): I need to update that page. On it. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5462#comment:46> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #5462: Deriving clause for arbitrary classes
by GHC 18 Nov '14

18 Nov '14

#5462: Deriving clause for arbitrary classes -------------------------------------+------------------------------------- Reporter: simonpj | Owner: dreixel Type: feature | Status: patch request | Milestone: 7.10.1 Priority: normal | Version: 7.2.1 Component: Compiler | Keywords: Generics Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: #7346 None/Unknown | Test Case: | Blocking: | Differential Revisions: Phab:D476 | -------------------------------------+------------------------------------- Comment (by simonpj): Wiki page https://ghc.haskell.org/trac/ghc/wiki/Commentary/Compiler/GenericDeriving#U… -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/5462#comment:45> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9804: Layering: Suspicious dependency from Parser to TcEvidence
by GHC 17 Nov '14

17 Nov '14

#9804: Layering: Suspicious dependency from Parser to TcEvidence -------------------------------------+------------------------------------- Reporter: rodlogic | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.3 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- There is an import from Parser to TcEvidence module. Why does the parser need to know about type checking? The parser should produce an AST and through the AST (and global modules) be isolated from the rest of the compiler pipeline. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9804> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8647: Reduce allocations in `integer-gmp`
by GHC 17 Nov '14

17 Nov '14

#8647: Reduce allocations in `integer-gmp` ------------------------------+-------------------------------------------- Reporter: hvr | Owner: Type: task | Status: new Priority: normal | Milestone: 7.8.1 Component: libraries | Version: 7.6.3 (other) | Operating System: Unknown/Multiple Keywords: | Type of failure: Runtime performance bug Architecture: x86_64 | Test Case: (amd64) | Blocking: Difficulty: Unknown | Blocked By: | Related Tickets: #8638 | ------------------------------+-------------------------------------------- I've added `printf(3)`s to `integer-gmp`s GMP allocation/reallocation functions, and noticed there to a significant amount of allocations going on. This is due to the fact that the CMM wrappers call `gmpz_init()` to initialize the result, and this already allocates a 1-limb `StgArray`. But the actual GMP operations perform a reallocate-call (which by contract also needs `memcpy` the untouched limb over to the newly allocated structure) based on the type of operation and the involved operands, causing the optimistically allocated 1-limb structure to become garbage right away w/o even being written to. I've been able to get rid of most such superfluous allocations by replacing {{{#!c ccall __gmpz_init(mp_result1 "ptr"); }}} by {{{#!c MP_INT__mp_alloc(mp_result1) = 0; MP_INT__mp_size(mp_result1) = 0; MP_INT__mp_d(mp_result1) = 0; // (1) }}} which is handled properly by all GMP operations we make use of currently. This elegantly lets the very first allocation be performed within the GMP operation (which has better knowledge with respect to how many limbs the result will require) I've got working proof-of-concept code, which reduces the allocations the big-num heavy `nofib` programs (I've omitted the benchmarks which had a 0% allocation change): {{{ -------------------------------------------------------------------------------- Program Size Allocs Runtime Elapsed TotalMem -------------------------------------------------------------------------------- ... bernouilli -0.1% -5.2% 0.12 0.12 +0.0% kahan -0.1% -10.5% 0.17 0.17 +0.0% primetest -0.1% -12.8% 0.07 0.07 +0.0% rsa -0.1% -13.8% 0.02 0.02 +0.0% symalg -0.1% -2.3% 0.01 0.01 +0.0% ... -------------------------------------------------------------------------------- Min -0.1% -13.8% -3.1% -3.1% -6.5% Max -0.0% +0.4% +4.0% +4.0% +1.5% Geometric Mean -0.1% -0.5% +0.5% +0.4% -0.1% }}} `(1)` This should actually point to a proper static closure I didn't need this for the proof-of-concept ---- Another place which helps avoiding temporarily allocating 1-limb `StgArrays` which live only for the duration of GMP FFI calls are those caused by the `toBig`-casts, which I'm also experimenting by making use of GMP's big-int/small-int add/sub/mul primitives (the deltas shown above are actually measured on top of this optimization), here's what to expect from such an optimization by itself (i.e. w/o the realloc-optimization from above): {{{ bernouilli +0.1% -4.2% 0.12 0.12 +0.0% kahan +0.1% -12.6% 0.17 0.17 +0.0% power +0.1% -2.7% +2.2% +2.2% +0.0% rsa +0.1% -4.1% 0.02 0.02 +0.0% scs +0.1% -2.6% -1.6% -1.6% +0.0% }}} Thus, the `kahan` benchmark benefits from this optimization by -12.6%, and on top of that another -10.5% by also avoiding the GMP-reallocations. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8647> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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Re: [GHC] #4900: DEPENDS pragma
by GHC 17 Nov '14

17 Nov '14

#4900: DEPENDS pragma -------------------------------------+------------------------------------- Reporter: cdsmith | Owner: Type: feature | Status: new request | Milestone: 7.10.1 Priority: normal | Version: Component: Compiler | Keywords: Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: None/Unknown | Test Case: TH_Depends | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by GregWeber): I added the documentation: https://phabricator.haskell.org/D481 -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4900#comment:71> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8664: libffi does not recognize AArch64 (ARM64)
by GHC 17 Nov '14

17 Nov '14

#8664: libffi does not recognize AArch64 (ARM64) -------------------------------------+------------------------------------- Reporter: kgardas | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: libraries (other) | Version: 7.7 Keywords: | Operating System: Linux Architecture: arm | Type of failure: Building GHC Difficulty: Easy (less than 1 | failed hour) | Test Case: Blocked By: | Blocking: Related Tickets: | -------------------------------------+------------------------------------- Hello, bundled libffi-3.0.11's configure does not recognize aarch64/arm64 platform. This is easily solvable by replacing it with newer release. I tested 3.0.13 and it went well. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8664> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8671: Rebindable syntax creates bogus warning
by GHC 17 Nov '14

17 Nov '14

#8671: Rebindable syntax creates bogus warning -------------------------+------------------------------------------------- Reporter: | Owner: thomaseding | Status: new Type: bug | Milestone: Priority: | Version: 7.6.3 normal | Operating System: Windows Component: | Type of failure: Incorrect warning at Compiler | compile-time Keywords: | Test Case: Architecture: | Blocking: Unknown/Multiple | Difficulty: | Unknown | Blocked By: | Related Tickets: | -------------------------+------------------------------------------------- {{{ {-# LANGUAGE RebindableSyntax #-} import Data.Void import Prelude ((.), ($), Int, id, Num(..)) (>>) :: (b -> c) -> (a -> b) -> (a -> c) (>>) = (.) return :: Void -> Void return = absurd run :: a -> (a -> b) -> b run x f = f x result :: Int result = run 8 $ do \n -> n * n id (+ 7) (* 2) }}} Compile with -Wall issues incorrect warnings. In fact the suggested fixes cause compile errors if implemented. {{{ Test.hs:22:5: Warning: A do-notation statement discarded a result of type Int. Suppress this warning by saying "_ <- \ n -> (*) n n", or by using the flag -fno-warn-unused-do-bind Test.hs:23:5: Warning: A do-notation statement discarded a result of type Int. Suppress this warning by saying "_ <- id", or by using the flag -fno-warn-unused-do-bind Test.hs:24:5: Warning: A do-notation statement discarded a result of type Int. Suppress this warning by saying "_ <- (( \ x_ -> (+) x_ 7))", or by using the flag -fno-warn-unused-do-bind }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8671> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8680: In STM: Variables only in left branch of orElse can invalidate the right branch transaction
by GHC 17 Nov '14

17 Nov '14

#8680: In STM: Variables only in left branch of orElse can invalidate the right branch transaction ------------------------------+-------------------------------------------- Reporter: jberryman | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.3 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Runtime performance bug Unknown/Multiple | Test Case: Difficulty: Unknown | Blocking: Blocked By: | Related Tickets: | ------------------------------+-------------------------------------------- I'm sorry if this is expected behavior; I'm still trying to wrap my head around this. I was surprised to learn that the right branch of an `orElse` can be invalidated by changes to the world only visible by the left branch. This might lead to starvation or performance issues for the use- case I was envisioning it for (e.g. several threads trying to take from one of a large set of TMVars in a randomized round-robin fashion). Here is a really bad example demonstrating current behavior: {{{ import Control.Concurrent import Control.Concurrent.STM import Control.Concurrent.STM.TSem import Control.Monad import System.IO import Debug.Trace main = do hSetBuffering stdout NoBuffering noMansLand <- replicateM 998 $ newTVarIO 0 t0 <- newTVarIO (1::Int) t999 <- newTVarIO (-1) let ts = t0:noMansLand++[t999] done <- atomically $ newTSem 0 forkIO $ atomically $ nestedOrElseMap done ts -- need enough time here for nestedOrElseMap thread above to move past t0 -- in this version, the modifications to t0 force nestedOrElseMap to be restarted forkIO (trace "starting vexing!" $ forever $ atomically $ (modifyTVar' t0 (+1) >> trace "vex" (return ()))) -- in this version nestedOrElseMap causes this transaction to be restarted and never makes progress: --forkIO (atomically (trace "starting vexing!" $ forever $ (modifyTVar' t0 (+1) >> trace "vex" (return ())))) atomically $ waitTSem done putStrLn "No livelock! Did the t0 counter get incremented?: " atomically (readTVar t0) >>= print -- another thread begins modifying head ts after we've moved to the right branch nestedOrElseMap :: TSem -> [TVar Int] -> STM () nestedOrElseMap done ts = trace "nestedOrElseMap starting" $ foldl1 orElse $ map transaction $ zip [(1::Int)..] ts where transaction (cnt,v) = do n <- traceShow cnt $ readTVar v if n < 0 then trace "@" (modifyTVar' v (subtract 1)) >> signalTSem done else retry }}} I can see it possibly being useful that both branches of an `orElse` see the same view of the variables they ''share'', but current behavior seems overzealous in restarting the whole transaction. Maybe this is an artifact of changes related to #7493? Or maybe it's obvious why this behavior has to be the way it is and its just not clicking for me. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8680> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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