January 2018 - ghc-tickets

[GHC] #12005: Constraint instances not shown in `:info`
by GHC 13 Oct '18

13 Oct '18

#12005: Constraint instances not shown in `:info` -------------------------------------+------------------------------------- Reporter: Iceland_jack | 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: -------------------------------------+------------------------------------- {{{ $ ghci -ignore-dot-ghci -XKindSignatures -XRank2Types -XConstraintKinds -XAllowAmbiguousTypes -XInstanceSigs GHCi, version 8.1.20160428: http://www.haskell.org/ghc/ :? for help Prelude> import Data.Kind Prelude Data.Kind> class Defer (p :: Constraint) where defer :: (p => r) -> r Prelude Data.Kind> instance Defer () where defer :: r -> r; defer = id Prelude Data.Kind> :i Defer class Defer (p :: Constraint) where defer :: (p => r) -> r {-# MINIMAL defer #-} -- Defined at <interactive>:2:1 }}} Same happens with the [https://github.com/ekmett/constraints/blob/master/src/Data/Constraint/Defer… Data.Constraint.Deferrable] which defines: {{{#!hs instance (Typeable a, Typeable b) => Deferrable (a ~ b) instance (Deferrable a, Deferrable b) => Deferrable (a, b) instance (Deferrable a, Deferrable b, Deferrable c) => Deferrable (a, b, c) }}} but no instances are shown: {{{ ghci> import Data.Constraint.Deferrable ghci> :i Deferrable class Deferrable (p :: Constraint) where deferEither :: proxy p -> (p => r) -> Either String r {-# MINIMAL deferEither #-} -- Defined in ‘Data.Constraint.Deferrable’ }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12005> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8763: forM_ [1..N] does not get fused (10 times slower than go function)
by GHC 13 Oct '18

13 Oct '18

#8763: forM_ [1..N] does not get fused (10 times slower than go function) ------------------------------+-------------------------------------------- Reporter: nh2 | 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: | ------------------------------+-------------------------------------------- Apparently idiomatic code like {{{forM_ [1.._N]}}} does not get fused away. This can give serious performance problems when unnoticed. {{{ -- Slow: forM_ [0.._N-1] $ \i -> do ... -- Around 10 times faster: loop _N $ \i -> do ... {-# INLINE loop #-} loop :: (Monad m) => Int -> (Int -> m ()) -> m () loop bex f = go 0 where go !n | n == bex = return () | otherwise = f n >> go (n+1) }}} Full code example: https://gist.github.com/nh2/8905997 - the relevant alternatives are commented. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8763> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13112: Windows 64-bit GHC HEAD segfaults on the code with a lot of TH stuff.
by GHC 12 Oct '18

12 Oct '18

#13112: Windows 64-bit GHC HEAD segfaults on the code with a lot of TH stuff. --------------------------------------+--------------------------------- Reporter: awson | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 Keywords: | Operating System: Windows Architecture: x86_64 (amd64) | Type of failure: None/Unknown Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: --------------------------------------+--------------------------------- Currently GHC HEAD segfaults on Windows 64-bit when compiling `language-c-quote-0.11.7.1` package. It spits something like `Access violation in generated code when executing data at 0000000102fbcf40` (I'm using my #13108 patch here). After repeated run, when GHC hasn't recompile all files, but only part of them, it succeeds. If I delete intermediate files and repeat clean compilation, it segfaults again. Haddock always segfaults (since it always recompile all files), more details here: https://github.com/haskell/haddock/pull/568. Since these access violations consistently happen on executable data at virtual addresses above 4GB mark, this very much smells as a GHC bytecode generator/linker issue. I believe, GHC and Haddock succeed exactly when all executable addresses stay below 4GB mark. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13112> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13923: Add a suppression flag to stop Typeable bindings being emitted with -ddump-simpl
by GHC 11 Oct '18

11 Oct '18

#13923: Add a suppression flag to stop Typeable bindings being emitted with -ddump- simpl -------------------------------------+------------------------------------- Reporter: mpickering | Owner: (none) Type: task | Status: new Priority: low | Milestone: 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: -------------------------------------+------------------------------------- When reading core output, it is very distracting to always have to wade through a large number of bindings generated by `Typeable`. In most cases I don't care about any of these so it would be easier if there was some way to stop them being printed or being generated in the first place. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13923> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13128: Refactor AvailInfo to be more sensible
by GHC 10 Oct '18

10 Oct '18

#13128: Refactor AvailInfo to be more sensible -------------------------------------+------------------------------------- Reporter: mpickering | Owner: mpickering Type: task | Status: new Priority: low | Milestone: 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: -------------------------------------+------------------------------------- `AvailInfo` has been the bane of my life for the last 12 months and I want to tame it. There are two main problems with it. 1. There is this horrible invariant where if the parent is also exported then it is the first element of the list of children. 2. The set of children and field labels are represented as lists which means many expensive calls to functions from `ListSetOps`. 1 Is easy enough to solve by adding a flag which says whether the parent is exported or not. My naive attempt to solve the second problem was to replace the list by a `NameSet`. At the interface file boundary, the `NameSet` is converted into a list using `nameSetElemsStable` to maintain determinism and only pay the cost of using this expensive function once. This ran into problems in `RnModIface` where there are several functions which map over the list of children. NameSets don't support mapping and so this is difficult to implement in a satisfactory way. The next plan of attack is to distinguish between `IfaceAvailInfo` and `AvailInfo`. The former will use the old representation (lists) in order to maintain determinism but the latter will use sets. Distinguishing the two modes is useful conceptually and practically. The data type is used in quite a few different ways in lots of places which makes writing a nice interface hard. This ticket is to record my trail in case I don't make it to the end. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13128> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #11368: Pattern synonym name is mangled when patterns are non-exhaustive
by GHC 10 Oct '18

10 Oct '18

#11368: Pattern synonym name is mangled when patterns are non-exhaustive ---------------------------------------+--------------------------- Reporter: Iceland_jack | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 8.1 Keywords: PatternSynonyms | Operating System: Linux Architecture: x86 | Type of failure: Other Test Case: | Blocked By: Blocking: | Related Tickets: #11367 Differential Rev(s): | Wiki Page: ---------------------------------------+--------------------------- {{{ pattern A n <- ... where A 0 = ... }}} When a pattern synonym is non-exhaustive its name is mangled: {{{ >>> A 3 "*** Exception: /tmp/tmp.t0h0pMgwWb.hs:(4,1)-(5,14): Non-exhaustive patterns in function $bA }}} “Non-exhaustive patterns in pattern synonym A” [https://ghc.haskell.org/trac/ghc/ticket/11367?replyto=5#comment:1 Comment] from ticket #11367. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11368> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #10783: Partial type signatures should work with pattern synonym signatures
by GHC 10 Oct '18

10 Oct '18

#10783: Partial type signatures should work with pattern synonym signatures -------------------------------------+------------------------------------- Reporter: mpickering | 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 Revisions: | -------------------------------------+------------------------------------- {{{#!hs {-# LANGUAGE PatternSynonyms #-} pattern MyJust :: _ pattern MyJust a = Just a }}} GHC can correctly infer the type for the pattern without the type signature so (to me) it is unexpected that this inferred type is not reported to me when using partial type signatures. It just seems to not be implemented currently. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10783> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12932: -fexternal-interpreter` fails to find symbols
by GHC 08 Oct '18

08 Oct '18

#12932: -fexternal-interpreter` fails to find symbols ----------------------------------------+---------------------------- Reporter: dominic | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: MacOS X Architecture: Unknown/Multiple | Type of failure: Other Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: ----------------------------------------+---------------------------- {{{-fexternal-interpreter}}} fails to find symbols but if I run without it all is well. Is this a bug or am I doing something wrong? {{{ ~/Dropbox/Private/Stochastic/demo $ ghci -fexternal-interpreter -prof fe- handling-example.o -i../../monad-bayes/src -package-db=.cabal- sandbox/x86_64-osx-ghc-8.0.1-packages.conf.d -L/usr/local/opt/openblas/lib -lopenblas ghci -fexternal-interpreter -prof fe-handling-example.o -i../../monad- bayes/src -package-db=.cabal-sandbox/x86_64-osx-ghc-8.0.1-packages.conf.d -L/usr/local/opt/openblas/lib -lopenblas GHCi, version 8.0.1: http://www.haskell.org/ghc/ :? for help Prelude> :l app/Main.hs :l app/Main.hs [ 1 of 16] Compiling Control.Monad.Bayes.LogDomain ( ../../monad- bayes/src/Control/Monad/Bayes/LogDomain.hs, interpreted ) [ 2 of 16] Compiling Control.Monad.Bayes.Primitive ( ../../monad- bayes/src/Control/Monad/Bayes/Primitive.hs, interpreted ) [ 3 of 16] Compiling Control.Monad.Bayes.Class ( ../../monad- bayes/src/Control/Monad/Bayes/Class.hs, interpreted ) [ 4 of 16] Compiling Control.Monad.Bayes.Sampler ( ../../monad- bayes/src/Control/Monad/Bayes/Sampler.hs, interpreted ) [ 5 of 16] Compiling Control.Monad.Bayes.Sequential ( ../../monad- bayes/src/Control/Monad/Bayes/Sequential.hs, interpreted ) [ 6 of 16] Compiling Control.Monad.Bayes.Prior ( ../../monad- bayes/src/Control/Monad/Bayes/Prior.hs, interpreted ) [ 7 of 16] Compiling Control.Monad.Bayes.Rejection ( ../../monad- bayes/src/Control/Monad/Bayes/Rejection.hs, interpreted ) [ 8 of 16] Compiling Control.Monad.Bayes.Weighted ( ../../monad- bayes/src/Control/Monad/Bayes/Weighted.hs, interpreted ) [ 9 of 16] Compiling Control.Monad.Bayes.Population ( ../../monad- bayes/src/Control/Monad/Bayes/Population.hs, interpreted ) [10 of 16] Compiling Control.Monad.Bayes.Deterministic ( ../../monad- bayes/src/Control/Monad/Bayes/Deterministic.hs, interpreted ) [11 of 16] Compiling Control.Monad.Bayes.Conditional ( ../../monad- bayes/src/Control/Monad/Bayes/Conditional.hs, interpreted ) [12 of 16] Compiling Control.Monad.Bayes.Dist ( ../../monad- bayes/src/Control/Monad/Bayes/Dist.hs, interpreted ) [13 of 16] Compiling Control.Monad.Bayes.Coprimitive ( ../../monad- bayes/src/Control/Monad/Bayes/Coprimitive.hs, interpreted ) [14 of 16] Compiling Control.Monad.Bayes.Trace ( ../../monad- bayes/src/Control/Monad/Bayes/Trace.hs, interpreted ) [15 of 16] Compiling Control.Monad.Bayes.Inference ( ../../monad- bayes/src/Control/Monad/Bayes/Inference.hs, interpreted ) [16 of 16] Compiling Main ( app/Main.hs, interpreted ) Ok, modules loaded: Main, Control.Monad.Bayes.LogDomain, Control.Monad.Bayes.Primitive, Control.Monad.Bayes.Class, Control.Monad.Bayes.Population, Control.Monad.Bayes.Conditional, Control.Monad.Bayes.Inference, Control.Monad.Bayes.Sampler, Control.Monad.Bayes.Rejection, Control.Monad.Bayes.Weighted, Control.Monad.Bayes.Sequential, Control.Monad.Bayes.Trace, Control.Monad.Bayes.Dist, Control.Monad.Bayes.Prior, Control.Monad.Bayes.Deterministic, Control.Monad.Bayes.Coprimitive. *Main> main main ghc-iserv-prof: lookupSymbol failed in relocateSection (relocate external) /Users/dom/Dropbox/Private/Stochastic/demo/.cabal-sandbox/lib/x86_64-osx- ghc-8.0.1/hmatrix-0.18.0.0-ASQ7f3Yo6PP5MiGTxN80a6/libHShmatrix-0.18.0.0-ASQ7f3Yo6PP5MiGTxN80a6_p.a: unknown symbol `___ieee_divdc3' ghc-iserv-prof: Could not on-demand load symbol '_vectorScan' ghc-iserv-prof: lookupSymbol failed in relocateSection (relocate external) /Users/dom/Dropbox/Private/Stochastic/demo/.cabal-sandbox/lib/x86_64-osx- ghc-8.0.1/hmatrix-0.18.0.0-ASQ7f3Yo6PP5MiGTxN80a6/libHShmatrix-0.18.0.0-ASQ7f3Yo6PP5MiGTxN80a6_p.a: unknown symbol `_vectorScan' ghc-iserv-prof: Could not on-demand load symbol '_hmatrixzm0zi18zi0zi0zmASQ7f3Yo6PP5MiGTxN80a6_InternalziVectorizzed_constantAux_closure' ghc-iserv-prof: lookupSymbol failed in relocateSection (relocate external) /Users/dom/Dropbox/Private/Stochastic/demo/.cabal-sandbox/lib/x86_64-osx- ghc-8.0.1/hmatrix-0.18.0.0-ASQ7f3Yo6PP5MiGTxN80a6/libHShmatrix-0.18.0.0-ASQ7f3Yo6PP5MiGTxN80a6_p.a: unknown symbol `_hmatrixzm0zi18zi0zi0zmASQ7f3Yo6PP5MiGTxN80a6_InternalziVectorizzed_constantAux_closure' ghc-iserv-prof: Could not on-demand load symbol '_hmatrixzm0zi18zi0zi0zmASQ7f3Yo6PP5MiGTxN80a6_InternalziMatrix_Matrix_con_info' ghc-iserv-prof: lookupSymbol failed in relocateSection (relocate external) /Users/dom/Dropbox/Private/Stochastic/demo/.cabal-sandbox/lib/x86_64-osx- ghc-8.0.1/hmatrix-0.18.0.0-ASQ7f3Yo6PP5MiGTxN80a6/libHShmatrix-0.18.0.0-ASQ7f3Yo6PP5MiGTxN80a6_p.a: unknown symbol `_hmatrixzm0zi18zi0zi0zmASQ7f3Yo6PP5MiGTxN80a6_InternalziMatrix_Matrix_con_info' ghc-iserv-prof: Could not on-demand load symbol '_hmatrixzm0zi18zi0zi0zmASQ7f3Yo6PP5MiGTxN80a6_InternalziElement_zgzl_info' ghc-iserv-prof: lookupSymbol failed in relocateSection (relocate external) /Users/dom/Dropbox/Private/Stochastic/demo/.cabal-sandbox/lib/x86_64-osx- ghc-8.0.1/hmatrix-0.18.0.0-ASQ7f3Yo6PP5MiGTxN80a6/libHShmatrix-0.18.0.0-ASQ7f3Yo6PP5MiGTxN80a6_p.a: unknown symbol `_hmatrixzm0zi18zi0zi0zmASQ7f3Yo6PP5MiGTxN80a6_InternalziElement_zgzl_info' ghc-iserv-prof: Could not on-demand load symbol '_hmatrixzm0zi18zi0zi0zmASQ7f3Yo6PP5MiGTxN80a6_InternalziUtil_zdfIndexableVectorDouble_closure' ByteCodeLink.lookupCE During interactive linking, GHCi couldn't find the following symbol: hmatrixzm0zi18zi0zi0zmASQ7f3Yo6PP5MiGTxN80a6_InternalziUtil_zdfIndexableVectorDouble_closure This may be due to you not asking GHCi to load extra object files, archives or DLLs needed by your current session. Restart GHCi, specifying the missing library using the -L/path/to/object/dir and -lmissinglibname flags, or simply by naming the relevant files on the GHCi command line. Alternatively, this link failure might indicate a bug in GHCi. If you suspect the latter, please send a bug report to: glasgow-haskell-bugs(a)haskell.org *Main> }}} But without {{{-fexternal-interpreter}}} all is well. {{{ ~/Dropbox/Private/Stochastic/demo $ ghci -prof fe-handling-example.o -i ../../monad-bayes/src -package-db=.cabal-sandbox/x86_64-osx- ghc-8.0.1-packages.conf.d -L/usr/local/opt/openblas/lib -lopenblas ghci -prof fe-handling-example.o -i../../monad-bayes/src -package-db =.cabal-sandbox/x86_64-osx-ghc-8.0.1-packages.conf.d -L/usr/local/opt/openblas/lib -lopenblas GHCi, version 8.0.1: http://www.haskell.org/ghc/ :? for help Prelude> :l app/Main.hs :l app/Main.hs [ 1 of 16] Compiling Control.Monad.Bayes.LogDomain ( ../../monad- bayes/src/Control/Monad/Bayes/LogDomain.hs, interpreted ) [ 2 of 16] Compiling Control.Monad.Bayes.Primitive ( ../../monad- bayes/src/Control/Monad/Bayes/Primitive.hs, interpreted ) [ 3 of 16] Compiling Control.Monad.Bayes.Class ( ../../monad- bayes/src/Control/Monad/Bayes/Class.hs, interpreted ) [ 4 of 16] Compiling Control.Monad.Bayes.Sampler ( ../../monad- bayes/src/Control/Monad/Bayes/Sampler.hs, interpreted ) [ 5 of 16] Compiling Control.Monad.Bayes.Sequential ( ../../monad- bayes/src/Control/Monad/Bayes/Sequential.hs, interpreted ) [ 6 of 16] Compiling Control.Monad.Bayes.Prior ( ../../monad- bayes/src/Control/Monad/Bayes/Prior.hs, interpreted ) [ 7 of 16] Compiling Control.Monad.Bayes.Rejection ( ../../monad- bayes/src/Control/Monad/Bayes/Rejection.hs, interpreted ) [ 8 of 16] Compiling Control.Monad.Bayes.Weighted ( ../../monad- bayes/src/Control/Monad/Bayes/Weighted.hs, interpreted ) [ 9 of 16] Compiling Control.Monad.Bayes.Population ( ../../monad- bayes/src/Control/Monad/Bayes/Population.hs, interpreted ) [10 of 16] Compiling Control.Monad.Bayes.Deterministic ( ../../monad- bayes/src/Control/Monad/Bayes/Deterministic.hs, interpreted ) [11 of 16] Compiling Control.Monad.Bayes.Conditional ( ../../monad- bayes/src/Control/Monad/Bayes/Conditional.hs, interpreted ) [12 of 16] Compiling Control.Monad.Bayes.Dist ( ../../monad- bayes/src/Control/Monad/Bayes/Dist.hs, interpreted ) [13 of 16] Compiling Control.Monad.Bayes.Coprimitive ( ../../monad- bayes/src/Control/Monad/Bayes/Coprimitive.hs, interpreted ) [14 of 16] Compiling Control.Monad.Bayes.Trace ( ../../monad- bayes/src/Control/Monad/Bayes/Trace.hs, interpreted ) [15 of 16] Compiling Control.Monad.Bayes.Inference ( ../../monad- bayes/src/Control/Monad/Bayes/Inference.hs, interpreted ) [16 of 16] Compiling Main ( app/Main.hs, interpreted ) Ok, modules loaded: Main, Control.Monad.Bayes.LogDomain, Control.Monad.Bayes.Primitive, Control.Monad.Bayes.Class, Control.Monad.Bayes.Population, Control.Monad.Bayes.Conditional, Control.Monad.Bayes.Inference, Control.Monad.Bayes.Sampler, Control.Monad.Bayes.Rejection, Control.Monad.Bayes.Weighted, Control.Monad.Bayes.Sequential, Control.Monad.Bayes.Trace, Control.Monad.Bayes.Dist, Control.Monad.Bayes.Prior, Control.Monad.Bayes.Deterministic, Control.Monad.Bayes.Coprimitive. *Main> main main Old State: S {p = 96.41248458072532, z = 59.16931688468654, log_alpha = -3.3251317115519465} New state: S {p = 85.18277032500659, z = 47.518663747379414, log_alpha = -0.8056624325046409} Old State: S {p = 110.26606081933504, z = 47.25472896292412, log_alpha = -7.942692650345256} New state: S {p = 99.8466327066433, z = 38.81428385855752, log_alpha = -0.712367347081303} Old State: S {p = 101.53403093173365, z = 54.69189565042656, log_alpha = 0.797288536547407} New state: S {p = 101.52281529166201, z = 44.30057747486097, log_alpha = -2.015330785654092} Old State: S {p = 77.31689464064326, z = 46.619899785065876, log_alpha = 2.2759251158534526} New state: S {p = 116.2875593953072, z = 38.966471329788355, log_alpha = -0.7142394862058071} Old State: S {p = 76.9380013726558, z = 50.125629063113514, log_alpha = -3.2499432321011583} New state: S {p = 69.40844025380522, z = 41.55282023557805, log_alpha = -3.0159942091527503e-2} Old State: S {p = 69.40844025380522, z = 41.55282023557805, log_alpha = -3.0159942091527503e-2} New state: S {p = 68.03763906369906, z = 35.283787110815105, log_alpha = 1.3054304633451674} Old State: S {p = 69.40844025380522, z = 41.55282023557805, log_alpha = -3.0159942091527503e-2} New state: S {p = 68.03763906369906, z = 35.283787110815105, log_alpha = -0.9916988019989725} Old State: S {p = 69.40844025380522, z = 41.55282023557805, log_alpha = -3.0159942091527503e-2} New state: S {p = 68.03763906369906, z = 35.283787110815105, log_alpha = -3.611295894501775} Old State: S {p = 69.40844025380522, z = 41.55282023557805, log_alpha = -3.0159942091527503e-2} New state: S {p = 68.03763906369906, z = 35.283787110815105, log_alpha = -0.7617210597518349} Old State: S {p = 116.2875593953072, z = 38.966471329788355, log_alpha = -0.7142394862058071} New state: S {p = 109.6078122188652, z = 32.55851436113107, log_alpha = -0.4233108619474501} Old State: S {p = 68.03763906369906, z = 35.283787110815105, log_alpha = 1.3054304633451674} New state: S {p = 79.79830336014518, z = 30.422294131721443, log_alpha = 0.6993690927536277} Old State: S {p = 68.03763906369906, z = 35.283787110815105, log_alpha = -0.9916988019989725} New state: S {p = 64.90164005295357, z = 30.422294131721443, log_alpha = -0.3152970276116467} Old State: S {p = 68.03763906369906, z = 35.283787110815105, log_alpha = -0.9916988019989725} New state: S {p = 64.90164005295357, z = 30.422294131721443, log_alpha = -0.8415339406842459} Old State: S {p = 68.03763906369906, z = 35.283787110815105, log_alpha = 1.3054304633451674} New state: S {p = 79.79830336014518, z = 30.422294131721443, log_alpha = -0.755338763976243} Old State: S {p = 68.03763906369906, z = 35.283787110815105, log_alpha = -0.9916988019989725} New state: S {p = 64.90164005295357, z = 30.422294131721443, log_alpha = -0.12244882682932601} Old State: S {p = 103.98419668715715, z = 51.46501997223569, log_alpha = NaN} New state: S {p = NaN, z = 41.96850310814045, log_alpha = -2.6446936218209336} Old State: S {p = 101.59457288618177, z = 50.895296415987694, log_alpha = NaN} New state: S {p = NaN, z = 41.61054780428653, log_alpha = -3.429882621028084} Old State: S {p = 87.94516676609489, z = 49.33016788299561, log_alpha = NaN} New state: S {p = NaN, z = 40.75469030451892, log_alpha = -0.3548643358912281} Old State: S {p = 85.99795164317248, z = 49.168021162595345, log_alpha = NaN} New state: S {p = NaN, z = 40.67497206346814, log_alpha = 2.1104720283005785} Old State: S {p = 78.54647250550833, z = 42.630247908299566, log_alpha = NaN} New state: S {p = NaN, z = 35.95097968042852, log_alpha = -0.6513484233809421} Old State: S {p = NaN, z = 40.75469030451892, log_alpha = -0.3548643358912281} New state: S {p = NaN, z = NaN, log_alpha = -1.5720943792122584} Old State: S {p = NaN, z = 40.75469030451892, log_alpha = -0.3548643358912281} New state: S {p = NaN, z = NaN, log_alpha = -1.6631770526157945} Old State: S {p = NaN, z = 40.67497206346814, log_alpha = 2.1104720283005785} New state: S {p = NaN, z = NaN, log_alpha = -1.2345329390236304} Old State: S {p = NaN, z = 35.95097968042852, log_alpha = -0.6513484233809421} New state: S {p = NaN, z = NaN, log_alpha = -1.820929341136602} Old State: S {p = NaN, z = 40.67497206346814, log_alpha = 2.1104720283005785} New state: S {p = NaN, z = NaN, log_alpha = -2.520535318849168} Old State: S {p = NaN, z = NaN, log_alpha = -1.5720943792122584} New state: S {p = NaN, z = NaN, log_alpha = -0.9471390581854239} Old State: S {p = NaN, z = NaN, log_alpha = -1.6631770526157945} New state: S {p = NaN, z = NaN, log_alpha = -1.0755021237404696} Old State: S {p = NaN, z = NaN, log_alpha = -1.2345329390236304} New state: S {p = NaN, z = NaN, log_alpha = -1.1239335260594507} Old State: S {p = NaN, z = NaN, log_alpha = -1.820929341136602} New state: S {p = NaN, z = NaN, log_alpha = -1.2944498914356701} Old State: S {p = NaN, z = NaN, log_alpha = -2.520535318849168} New state: S {p = NaN, z = NaN, log_alpha = -0.27411572356967484} Accept: False Old State: S {p = 111.8506804060528, z = 49.43995360167743, log_alpha = -9.192660539879242} New state: S {p = 100.79139727821112, z = 40.36178045350178, log_alpha = 1.3407944594098864} Old State: S {p = 112.56620850387993, z = 51.36209895306485, log_alpha = -2.625437037736268} New state: S {p = 101.35925858189091, z = 41.718829881234356, log_alpha = -0.7240542276022712} Old State: S {p = 124.03888190950703, z = 60.73043151177312, log_alpha = -5.946495216000299} New state: S {p = 108.98533165239414, z = 47.91166969904897, log_alpha = -0.8873500091662709} Old State: S {p = 98.02675197633516, z = 52.91365067391672, log_alpha = 2.312571443928833} New state: S {p = 138.1350004691826, z = 43.12261446736768, log_alpha = -0.2792667910662988} Old State: S {p = 94.54575888175407, z = 42.83674832921917, log_alpha = -7.3217354704711175} New state: S {p = 86.44898836218327, z = 35.83329122968358, log_alpha = -0.6931069199421952} Old State: S {p = 86.44898836218327, z = 35.83329122968358, log_alpha = -0.6931069199421952} New state: S {p = 82.70767613536381, z = 30.592809349196145, log_alpha = 0.3349397265296642} Old State: S {p = 86.44898836218327, z = 35.83329122968358, log_alpha = -0.6931069199421952} New state: S {p = 82.70767613536381, z = 30.592809349196145, log_alpha = -1.3495963112508207} Old State: S {p = 138.1350004691826, z = 43.12261446736768, log_alpha = -0.2792667910662988} New state: S {p = 129.45324316753013, z = 35.29589318379763, log_alpha = -0.386669465854595} Old State: S {p = 138.1350004691826, z = 43.12261446736768, log_alpha = -0.2792667910662988} New state: S {p = 129.45324316753013, z = 35.29589318379763, log_alpha = -0.2946746748816039} Old State: S {p = 138.1350004691826, z = 43.12261446736768, log_alpha = -0.2792667910662988} New state: S {p = 129.45324316753013, z = 35.29589318379763, log_alpha = 6.008701708774278e-2} Old State: S {p = 82.70767613536381, z = 30.592809349196145, log_alpha = 0.3349397265296642} New state: S {p = 84.42743985481702, z = 26.485152940386072, log_alpha = -0.8565266788034482} Old State: S {p = 82.70767613536381, z = 30.592809349196145, log_alpha = -1.3495963112508207} New state: S {p = 78.90510523061384, z = 26.485152940386072, log_alpha = -0.23947594100584424} Old State: S {p = 82.70767613536381, z = 30.592809349196145, log_alpha = -1.3495963112508207} New state: S {p = 78.90510523061384, z = 26.485152940386072, log_alpha = -1.6400685168014388} Old State: S {p = 82.70767613536381, z = 30.592809349196145, log_alpha = -1.3495963112508207} New state: S {p = 78.90510523061384, z = 26.485152940386072, log_alpha = -2.309718174473867} Old State: S {p = 82.70767613536381, z = 30.592809349196145, log_alpha = 0.3349397265296642} New state: S {p = 84.42743985481702, z = 26.485152940386072, log_alpha = 0.39960426429090445} Old State: S {p = 103.15456652417501, z = 48.70703230482669, log_alpha = 3.261489684559035} New state: S {p = 223.41791271148057, z = 40.00425989911341, log_alpha = -1.6654810839749887} Old State: S {p = 78.21539356172975, z = 49.34769089107648, log_alpha = 2.9941081783405235} New state: S {p = 165.5956281460007, z = 40.9594944371077, log_alpha = -0.6807278054716505} Old State: S {p = 121.27107377910983, z = 50.9432853913191, log_alpha = -8.126318808529764} New state: S {p = 108.916591323712, z = 41.2439385542472, log_alpha = 0.4369643557823619} Old State: S {p = 98.33533600637841, z = 50.915794054555995, log_alpha = -0.47638340582836275} New state: S {p = 91.42595876935069, z = 41.6915974374073, log_alpha = -1.570488913622821} Old State: S {p = 106.35901771371051, z = 58.39939541846798, log_alpha = 2.4859548939567686} New state: S {p = 153.7564635774571, z = 46.75791989853097, log_alpha = -0.7265425179819862} Old State: S {p = 165.5956281460007, z = 40.9594944371077, log_alpha = -0.6807278054716505} New state: S {p = 153.47230437543251, z = 33.25266900659429, log_alpha = -1.6781162212290632} Old State: S {p = 165.5956281460007, z = 40.9594944371077, log_alpha = -0.6807278054716505} New state: S {p = 153.47230437543251, z = 33.25266900659429, log_alpha = 0.7148953771487301} Old State: S {p = 165.5956281460007, z = 40.9594944371077, log_alpha = -0.6807278054716505} New state: S {p = 153.47230437543251, z = 33.25266900659429, log_alpha = 1.2994581914331431} Old State: S {p = 165.5956281460007, z = 40.9594944371077, log_alpha = -0.6807278054716505} New state: S {p = 153.47230437543251, z = 33.25266900659429, log_alpha = -0.6908099313919266} Old State: S {p = 165.5956281460007, z = 40.9594944371077, log_alpha = -0.6807278054716505} New state: S {p = 153.47230437543251, z = 33.25266900659429, log_alpha = 0.6115450247483429} Old State: S {p = 153.47230437543251, z = 33.25266900659429, log_alpha = 0.6115450247483429} New state: S {p = 149.84673299439467, z = 27.669736758576065, log_alpha = 2.249112097719827} Old State: S {p = 153.47230437543251, z = 33.25266900659429, log_alpha = 0.7148953771487301} New state: S {p = 150.56328821556426, z = 27.669736758576065, log_alpha = -1.6634676360703886} Old State: S {p = 153.47230437543251, z = 33.25266900659429, log_alpha = 0.6115450247483429} New state: S {p = 149.84673299439467, z = 27.669736758576065, log_alpha = -1.1143896901497614} Old State: S {p = 153.47230437543251, z = 33.25266900659429, log_alpha = -1.6781162212290632} New state: S {p = 143.93225309113896, z = 27.669736758576065, log_alpha = 1.2174133795952156} Old State: S {p = 153.47230437543251, z = 33.25266900659429, log_alpha = -1.6781162212290632} New state: S {p = 143.93225309113896, z = 27.669736758576065, log_alpha = 0.2956142597127277} Accept: False 4.962072576592402e-2 7.408640679453008 *Main> }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12932> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14626: No need to enter a scrutinised value
by GHC 08 Oct '18

08 Oct '18

#14626: No need to enter a scrutinised value -------------------------------------+------------------------------------- Reporter: heisenbug | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 Keywords: performance | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: #13861 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- While analysing the output of #13861 I stumbled over an unnecessary pessimisation in handling of scrutinised values. With words of Simon (from https://phabricator.haskell.org/D4267 with minor edits added): Interesting. Yes, please make a ticket! (And transfer the info below into it.) I think the issue is this. Given (the STG-ish code) {{{#!hs data Colour = Red | Green | Blue f x = case x of y Red -> Green DEFAULT -> y }}} (here `y` is the case binder) we can just return `x` rather than entering it in DEFAULT branch, because `y` will be fully evaluated and its pointer will be correctly tagged. You absolutely can't check for an `OccName` of `"wild"`!! That is neither necessary nor sufficient :-). Instead, check `isEvaldUnfolding (idUnfolding y)`. See `Note [Preserve evaluatedness]` in `CoreTidy.hs`. And be sure to augment that note if you make the change. I would expect perf benefits to be small on average, but it's simple to implement. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14626> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14152: Float exit paths out of recursive functions
by GHC 08 Oct '18

08 Oct '18

#14152: Float exit paths out of recursive functions -------------------------------------+------------------------------------- Reporter: nomeata | Owner: (none) Type: task | 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: #14137 #10918 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This is a spin off of a discussion from #14137. == The problem == We generally avoid inlining or floating a binding into a recursive function, because we do not want to duplicat work/allocations. But sometimes the binding is only used inside the recursive function on the “exit path”. In which case it would be good to inline. Example: {{{#!hs let x = f x0 in let go 10 = h x go i = go (i+1) in go (0::Int) + 100 }}} It would be beneficial to inline `x`. The problem is that it is not very obvious that this occurence of `x` is ok for inlining. In particular, it is not syntactically visible. == Proposed solution == If we apply loopification (#14068), this would turn into {{{#!hs let x = f x0 in let go n = joinrec jgo 10 = h x jgo i = call jgo (i+1) in call jgo n in go (0::Int) + 100 }}} I’d like to call this ''first joinrec normal form'', defined as “every recursive function where all recursive calls are tail-recursive is a recursive join point”. This ticket proposes to transform this even further and ''float out all case alternatives that do not mention `jgo` as non-recursive join- points'', as so: {{{#!hs let x = f x0 in let go n = join jexit = h x joinrec jgo 10 = call jexit jgo i = call jgo (i+1) in call jgo n in go (0::Int) + 100 }}} I’d like to call this ''second `joinrec` normal form'', defined as “in first `joinrec` normal form, and all subexpressions of a recursive join point `j` that are in tail-call position and do not mention `j` are join calls”. If the floated expression has free variables that are bound inside the `joinrec`, they turn into parameters of the newly created joinpoint. At this point, GHC can tell that `go` is called at most once, and will therefore happily inline `x` into the right hand side of `jexit. == Alternative solutions == Ticket #10918 uses Call Arity results to learn that `x` is one-Shot, and inline it even in the original code. This works, but the problem is that float-out will undo this. See [ticket:10918#comment:5]. == Limitation === It only works for recursive functions that are join points, or can be turned into join points by loopification (#14068). It does not work forexample for {{{#!hs let x = f x0 let go 0 = h x go n = (go (n-1) + 1 in go 10 }}} although it would be equally desirable to float `h x` out of `go` so that `x` can be inlined. == Preservation == A remaining tricky point is that we need to stop one of these carefully- constructed non-recursive join points being inlined into a recursive join point, even if it is invoked at just one place. That should not be hard. And in a final run of the simplifer (or in CorePrep) we could switch off that restriction and let it inline. (Ticket #14137 is about inlining ''more'' join points into recursive join points, so it is the antithesis to the present ticket.) -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14152> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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