September 2017 - ghc-tickets

[GHC] #10012: Cheap-to-compute values aren't pushed into case branches inducing unnecessary register pressure
by GHC 22 Dec '17

22 Dec '17

#10012: Cheap-to-compute values aren't pushed into case branches inducing unnecessary register pressure -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.4 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Runtime Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Revisions: | -------------------------------------+------------------------------------- When characterizing bytestring's `Builder` interface[1] I noticed that some benchmarks involving repeated appends (e.g. `Host endian/1MB of Word8 in chunks of 16`) perform inexplicably much worse than others. A glance at the assembly revealed that a large number of `Word8`s are being evaluated and saved to registers, only to be later stored. E.g., ```#!asm # First we evaluate a number of Word8s, saving them in registers movzbl %bl,%ebx leaq 1(%r14),%rcx movzbl %cl,%ecx leaq 2(%r14),%rdx movzbl %dl,%edx leaq 3(%r14),%rsi movzbl %sil,%esi leaq 4(%r14),%r9 movzbl %r9b,%r9d leaq 5(%r14),%r10 movzbl %r10b,%r10d ... # Eventually we run out of registers and start spilling to the stack movq %rax,64(%rsp) leaq 7(%r14),%rax movzbl %al,%eax movq %rbx,72(%rsp) ... # Only after evaluating all of the needed words do we actually consume # them movq %rax,-152(%r12) movq 72(%rsp),%rax movq %rax,-144(%r12) movq 80(%rsp),%rax movq %rax,-136(%r12) movq 88(%rsp),%rax movq %rax,-128(%r12) ... movq %rsi,-56(%r12) movq %r9,-48(%r12) movq %r10,-40(%r12) movq %r11,-32(%r12) movq %r14,-24(%r12) ``` This is due to the fact that the `Word`s are bound outside of a case analysis and GHC is reluctant to push them inside of the branches. The float-in pass will only float a binding into a case if the value is "small" and at least one branch doesn't use the binding. Unfortunately the case expression in question has only two branches. This is demonstrated in the attached testcase. [1] https://github.com/kolmodin/binary/pull/65 [2] https://www.haskell.org/pipermail/ghc-devs/2015-January/007997.html -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10012> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13001: EnumFromThenTo is is not a good producer
by GHC 22 Dec '17

22 Dec '17

#13001: EnumFromThenTo is is not a good producer -------------------------------------+------------------------------------- Reporter: George | Owner: Type: bug | Status: new Priority: low | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: MacOS X Architecture: x86_64 | Type of failure: Runtime (amd64) | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{#!hs {-# OPTIONS_GHC -Wall #-} module Foo where testFromTo :: Int -> Int testFromTo n = length ([0..(10^n)] :: [Int]) testFromThenTo :: Int -> Int testFromThenTo n = length ([0,2..(10^n)] :: [Int]) }}} {{{ $ ghci -fobject-code -O GHCi, version 8.0.1: http://www.haskell.org/ghc/ :? for help Prelude> :load Foo :load Foo [1 of 1] Compiling Foo ( Foo.hs, Foo.o ) Ok, modules loaded: Foo (Foo.o). Prelude Foo> :set +s :set +s Prelude Foo> testFromTo 5 testFromTo 5 100001 (0.02 secs, 97,992 bytes) Prelude Foo> testFromThenTo 5 testFromThenTo 5 50001 (0.00 secs, 5,694,424 bytes) Prelude Foo> testFromThenTo 6 testFromThenTo 6 500001 (0.02 secs, 56,095,288 bytes) Prelude Foo> }}} I set the Type to bug rather than feature request as the source code in http://hackage.haskell.org/package/base-4.9.0.0/docs/src/GHC.Enum.html#enum… seems to be trying to do list fusion: {{{#!hs -- efdInt and efdtInt deal with [a,b..] and [a,b..c]. -- The code is more complicated because of worries about Int overflow. -- See Note [How the Enum rules work] {-# RULES "efdtInt" [~1] forall x1 x2 y. efdtInt x1 x2 y = build (\ c n -> efdtIntFB c n x1 x2 y) "efdtIntUpList" [1] efdtIntFB (:) [] = efdtInt #-} }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13001> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12905: Core lint with pattern synonym
by GHC 22 Dec '17

22 Dec '17

#12905: Core lint with pattern synonym -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 8.0.1 (Type checker) | Keywords: typeable | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Yet another program from the type-indexed `Typeable` effort which breaks GHC (`master` branch as of 3bd1dd4d75fde3b922d4de08c16f29bdeb8e05d7) with a core lint error, {{{#!hs {-# LANGUAGE GADTs, TypeOperators, PatternSynonyms, TypeInType, PolyKinds, RankNTypes #-} module T where import GHC.Exts import Data.Kind import Data.Type.Equality data TypeRep (a :: k) where TrTyCon :: TypeRep (a :: k) TrApp :: forall k1 k2 (a :: k1 -> k2) (b :: k1). TypeRep (a :: k1 -> k2) -> TypeRep (b :: k1) -> TypeRep (a b) TrFun :: forall (r1 :: RuntimeRep) (r2 :: RuntimeRep) (a :: TYPE r1) (b :: TYPE r2). TypeRep a -> TypeRep b -> TypeRep (a -> b) pattern TRFun :: forall k (fun :: k). () => forall (r1 :: RuntimeRep) (r2 :: RuntimeRep) (arg :: TYPE r1) (res :: TYPE r2). (k ~ Type, fun ~~ (arg -> res)) => TypeRep arg -> TypeRep res -> TypeRep fun pattern TRFun arg res <- TrFun arg res where TRFun arg res = TrFun arg res }}} This program produces many core lint errors, although all of them fall into only a few classes. Here's one, {{{ *** Core Lint errors : in result of Desugar (before optimization) *** <no location info>: warning: In the coercion ‘Sym (Sym cobox_a3fT |> Sym cobox_a3fU)’ Kind application error in type ‘((->) |> <*>_N ->_N <*>_N ->_N Sym cobox) a’ Function kind = * -> * -> k Arg kinds = [(a, TYPE r1)] }}} {{{ <no location info>: warning: [RHS of $d~~_a3fO :: (fun :: k) ~~ ((a -> b) :: *)] Kind application error in coercion ‘Sym (Sym (<(->)>_N |> ((<*>_N -> <*>_N -> Sym cobox_a3fU) ; Sym (<*>_N -> <*>_N -> Sym cobox_a3fH))) |> (<*>_N -> <*>_N -> Sym cobox_a3fU)) <a>_N’ Function kind = * -> * -> * Arg kinds = [(a, TYPE r1)] }}} It appears that this is yet another case of the kind of `(->)` being too restrictive (#11714) since `a -> b` appears to be lifted to the coercion `TyConAppCo role (->) [a, b]`. Adding a `FunCo` constructor to `Coercion` would likely be an easy way to resolve this. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12905> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12670: Representation polymorphism validity check is too strict
by GHC 22 Dec '17

22 Dec '17

#12670: Representation polymorphism validity check is too strict -------------------------------------+------------------------------------- Reporter: bgamari | Owner: Type: bug | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 8.0.1 (Type checker) | Keywords: typeable | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- As of 465c6c5d15f8fb54afb78408f3a79e75e74d2cd4 GHC rejects this program, {{{#!hs {-# LANGUAGE GADTs #-} {-# LANGUAGE TypeInType #-} {-# LANGUAGE RankNTypes #-} module Hi where import GHC.Exts data TypeRep (a :: k) where TrFun :: forall (r1 :: RuntimeRep) (r2 :: RuntimeRep) (a :: TYPE r1) (b :: TYPE r2). TypeRep a -> TypeRep b -> TypeRep (a -> b) }}} Claiming that it has inappropriate polymorphism over `RuntimeRep`, {{{ $ ghc hi2.hs [1 of 1] Compiling Hi ( hi2.hs, hi2.o ) hi2.hs:7:5: error: • A representation-polymorphic type is not allowed here: Type: a Kind: TYPE r1 • In the definition of data constructor ‘TrFun’ In the data type declaration for ‘TypeRep’ }}} I suspect this check is unnecessarily strict since we never need to store a value of type `a` to represent `TypeRep a` at runtime. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12670> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #14288: ScopedTypeVariables with nexted foralls broken since 8.0.2
by GHC 20 Dec '17

20 Dec '17

#14288: ScopedTypeVariables with nexted foralls broken since 8.0.2 -------------------------------------+------------------------------------- Reporter: | Owner: (none) MikolajKonarski | Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 (Type checker) | Keywords: | Operating System: Linux Architecture: x86_64 | Type of failure: GHC rejects (amd64) | valid program Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- The following example fails in 8.2.1 and 8.0.2. Works fine in 7.10.3. If that's intended (that only the first forall has extended scope), I didn't find any mention of that in GHC manual. The two commented out variants work fine in all. {{{#!hs {-# LANGUAGE ScopedTypeVariables #-} main :: IO () main = do -- let f :: forall a ref. ref () -> () -- let f :: forall ref. forall a. ref () -> () let f :: forall a. forall ref. ref () -> () f x = let r :: ref () r = x in () return $ f (Just ()) }}} The error (the same in 8.2.1 and 8.0.2) is: {{{#!hs $ ghc --make forall.hs [1 of 1] Compiling Main ( forall.hs, forall.o ) forall.hs:8:21: error: • Couldn't match type ‘ref’ with ‘ref1’ ‘ref’ is a rigid type variable bound by the type signature for: f :: forall a (ref :: * -> *). ref () -> () at forall.hs:6:29 ‘ref1’ is a rigid type variable bound by the type signature for: r :: forall (ref1 :: * -> *). ref1 () at forall.hs:7:22 Expected type: ref1 () Actual type: ref () • In the expression: x In an equation for ‘r’: r = x In the expression: let r :: ref () r = x in () • Relevant bindings include r :: ref1 () (bound at forall.hs:8:17) x :: ref () (bound at forall.hs:7:9) f :: ref () -> () (bound at forall.hs:7:7) }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14288> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #12512: UnboxedTupleRep-related panic involving typeclasses
by GHC 20 Dec '17

20 Dec '17

#12512: UnboxedTupleRep-related panic involving typeclasses -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | crash Test Case: | Blocked By: Blocking: | Related Tickets: #11723 Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- You can trigger a GHC panic by abusing `UnboxedTupleRep` in just the right way: {{{#!hs {-# LANGUAGE DataKinds #-} {-# LANGUAGE KindSignatures #-} {-# LANGUAGE StandaloneDeriving #-} {-# LANGUAGE UnboxedTuples #-} import GHC.Exts class Wat (a :: TYPE 'UnboxedTupleRep) deriving instance Wat (# a, b #) }}} {{{ $ /opt/ghc/8.0.1/bin/ghc Bug.hs [1 of 1] Compiling Bug ( Bug.hs, Bug.o ) ghc: panic! (the 'impossible' happened) (GHC version 8.0.1 for x86_64-unknown-linux): newTyConEtadArity (#,#) Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} This is probably a leak that #11723 didn't plug, as it only considered datatypes, not typeclasses. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12512> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #9244: Compiler could warn about type variable shadowing, and hint about ScopedTypeVariables
by GHC 18 Dec '17

18 Dec '17

#9244: Compiler could warn about type variable shadowing, and hint about ScopedTypeVariables -------------------------+------------------------------------------------- Reporter: | Owner: stusmith | Status: new Type: | Milestone: feature request | Version: 7.6.3 Priority: | Operating System: Unknown/Multiple normal | Type of failure: Incorrect warning at Component: | compile-time Compiler | Test Case: Keywords: | Blocking: Architecture: | Unknown/Multiple | Difficulty: | Unknown | Blocked By: | Related Tickets: | -------------------------+------------------------------------------------- GHC already warns about variable shadowing: {{{ timesTwoPlusOne x = timesTwo x + 1 where timesTwo x = x * 2 Warning: This binding for `x' shadows the existing binding bound at <location> }}} However the similar warning doesn't happen for type variables. {{{ tryMaybe :: IO a -> IO (Maybe a) tryMaybe action = do result <- (try action) :: IO (Either SomeException a) return $ case result of Left _ -> Nothing Right v -> Just v Couldn't match type `a' with `a1' `a' is a rigid type variable bound by the type signature for tryMaybe :: IO a -> IO (Maybe a) at types.hs:<line>:13 `a1' is a rigid type variable bound by an expression type signature: IO (Either SomeException a1) at types.hs:<line>:15 Expected type: IO a1 Actual type: IO a ... }}} Here, I thought that the 'a' in the function's type declaration was the same 'a' in the expression type declaration. However in Haskell 98, they are completely different variables. Suggestion: if a type variable is renamed by the compiler due to a clash with another type variable, issue a warning that the second shadows the first, and give a hint about using -XScopedTypeVariables and forall. Alternative suggestion: if an error is displayed, where the error contains a renamed type variable, issue a hint that the second shadows the first, and give a hint about using -XScopedTypeVariables and forall. -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9244> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13627: IndexError: pop from empty list
by GHC 16 Dec '17

16 Dec '17

#13627: IndexError: pop from empty list -------------------------------------+------------------------------------- Reporter: Lemming | Owner: (none) Type: bug | Status: new Priority: normal | 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: -------------------------------------+------------------------------------- ==== How to Reproduce ==== While doing a GET operation on `/attachment/ticket/13626/`, Trac issued an internal error. ''(please provide additional details here)'' Request parameters: {{{ {u'action': u'new', 'path': u'13626/', 'realm': u'ticket'} }}} User agent: `#USER_AGENT#` ==== System Information ==== ''Systeminformation nicht verfügbar'' ==== Enabled Plugins ==== ''Plugininformation nicht verfügbar'' ==== Interface Customization ==== ''Interface customization information not available'' ==== Python Traceback ==== {{{ Traceback (most recent call last): File "build/bdist.linux-x86_64/egg/trac/web/main.py", line 623, in _dispatch_request dispatcher.dispatch(req) File "build/bdist.linux-x86_64/egg/trac/web/main.py", line 259, in dispatch iterable=chrome.use_chunked_encoding) File "build/bdist.linux-x86_64/egg/trac/web/chrome.py", line 1164, in render_template encoding='utf-8') File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 184, in render return encode(generator, method=method, encoding=encoding, out=out) File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 58, in encode for chunk in iterator: File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 350, in __call__ for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 829, in __call__ for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 669, in __call__ for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 774, in __call__ for kind, data, pos in chain(stream, [(None, None, None)]): File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 594, in __call__ for ev in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "build/bdist.linux-x86_64/egg/trac/web/chrome.py", line 1431, in _strip_accesskeys for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "build/bdist.linux-x86_64/egg/trac/web/chrome.py", line 1420, in _generate for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "/usr/local/lib/python2.7/dist- packages/genshi/filters/transform.py", line 706, in _unmark for mark, event in stream: File "/usr/local/lib/python2.7/dist- packages/genshi/filters/transform.py", line 1101, in __call__ for mark, event in stream: File "/usr/local/lib/python2.7/dist- packages/genshi/filters/transform.py", line 118, in __iter__ event = self.stream.next() File "/usr/local/lib/python2.7/dist- packages/genshi/filters/transform.py", line 734, in __call__ for mark, event in stream: File "/usr/local/lib/python2.7/dist- packages/genshi/filters/transform.py", line 702, in _mark for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 618, in _include for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 378, in _match ctxt, start=idx + 1, **vars): File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 378, in _match ctxt, start=idx + 1, **vars): File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 362, in _match content = list(content) File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 618, in _include for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 326, in _match for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 315, in _strip event = next() File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 558, in _flatten for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/path.py", line 588, in _generate subevent = next() File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 618, in _include for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 315, in _strip event = next() File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 558, in _flatten for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/path.py", line 588, in _generate subevent = next() File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 618, in _include for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 315, in _strip event = next() File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 558, in _flatten for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/filters/i18n.py", line 178, in _generate for event in msgbuf.translate(gettext(msgbuf.format())): File "/usr/local/lib/python2.7/dist-packages/genshi/filters/i18n.py", line 1051, in translate events = self.events[order].pop(0) IndexError: pop from empty list }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13627> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #13418: IndexError: pop from empty list
by GHC 16 Dec '17

16 Dec '17

#13418: IndexError: pop from empty list -------------------------------------+------------------------------------- Reporter: ralf | Owner: (none) Type: bug | Status: new Priority: normal | 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: -------------------------------------+------------------------------------- ==== How to Reproduce ==== While doing a GET operation on `/attachment/ticket/13417/`, Trac issued an internal error. ''(please provide additional details here)'' Request parameters: {{{ {u'action': u'new', 'path': u'13417/', 'realm': u'ticket'} }}} User agent: `Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.76 Safari/537.36` ==== System Information ==== ''Systeminformation nicht verfügbar'' ==== Enabled Plugins ==== ''Plugininformation nicht verfügbar'' ==== Interface Customization ==== ''Interface customization information not available'' ==== Python Traceback ==== {{{ Traceback (most recent call last): File "/usr/local/lib/python2.7/dist-packages/trac/web/main.py", line 613, in _dispatch_request dispatcher.dispatch(req) File "/usr/local/lib/python2.7/dist-packages/trac/web/main.py", line 273, in dispatch iterable=chrome.use_chunked_encoding) File "/usr/local/lib/python2.7/dist-packages/trac/web/chrome.py", line 1159, in render_template encoding='utf-8') File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 184, in render return encode(generator, method=method, encoding=encoding, out=out) File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 58, in encode for chunk in iterator: File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 350, in __call__ for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 829, in __call__ for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 669, in __call__ for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 774, in __call__ for kind, data, pos in chain(stream, [(None, None, None)]): File "/usr/local/lib/python2.7/dist-packages/genshi/output.py", line 594, in __call__ for ev in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "/usr/local/lib/python2.7/dist-packages/trac/web/chrome.py", line 1426, in _strip_accesskeys for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "/usr/local/lib/python2.7/dist-packages/trac/web/chrome.py", line 1415, in _generate for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "/usr/local/lib/python2.7/dist- packages/genshi/filters/transform.py", line 706, in _unmark for mark, event in stream: File "/usr/local/lib/python2.7/dist- packages/genshi/filters/transform.py", line 1101, in __call__ for mark, event in stream: File "/usr/local/lib/python2.7/dist- packages/genshi/filters/transform.py", line 118, in __iter__ event = self.stream.next() File "/usr/local/lib/python2.7/dist- packages/genshi/filters/transform.py", line 734, in __call__ for mark, event in stream: File "/usr/local/lib/python2.7/dist- packages/genshi/filters/transform.py", line 702, in _mark for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 618, in _include for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 378, in _match ctxt, start=idx + 1, **vars): File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 378, in _match ctxt, start=idx + 1, **vars): File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 362, in _match content = list(content) File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 618, in _include for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 326, in _match for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 315, in _strip event = next() File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 558, in _flatten for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/path.py", line 588, in _generate subevent = next() File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 618, in _include for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 315, in _strip event = next() File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 558, in _flatten for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/core.py", line 289, in _ensure for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/path.py", line 588, in _generate subevent = next() File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 618, in _include for event in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/template/markup.py", line 315, in _strip event = next() File "/usr/local/lib/python2.7/dist-packages/genshi/template/base.py", line 558, in _flatten for kind, data, pos in stream: File "/usr/local/lib/python2.7/dist-packages/genshi/filters/i18n.py", line 178, in _generate for event in msgbuf.translate(gettext(msgbuf.format())): File "/usr/local/lib/python2.7/dist-packages/genshi/filters/i18n.py", line 1051, in translate events = self.events[order].pop(0) IndexError: pop from empty list }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13418> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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[GHC] #8272: testing if SpLim=$rbp and Sp=$rsp changed performance at all
by GHC 15 Dec '17

15 Dec '17

#8272: testing if SpLim=$rbp and Sp=$rsp changed performance at all ----------------------------------------------+---------------------------- Reporter: carter | Owner: carter Type: task | Status: new Priority: normal | Milestone: 7.10.1 Component: Compiler | Version: 7.7 Keywords: callingConvention | Operating System: Architecture: x86_64 (amd64) | Unknown/Multiple Difficulty: Project (more than a week) | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: ----------------------------------------------+---------------------------- testing if SpLim=$rbp and Sp=$rsp changed performance at all would need a stack check but then push could be used to spill to the stack Idea via Nathan Howell. At the very least, the x86 PUSH instruction has a more succinct encoding than MOV. worth hacking out to see if this can measurable shift ghc perf on nofib or not. this would be part of a larger effort to explore ways to improve GHC's calling convention for modern hardware -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8272> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler

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