#12115: CoreLint error in safe program -------------------------------------+------------------------------------- Reporter: osa1 | Owner: Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: | codegen/should_compile/T12115 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by simonpj): * status: new => closed * testcase: => codegen/should_compile/T12115 * resolution: => fixed -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12115#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#12115: CoreLint error in safe program -------------------------------------+------------------------------------- Reporter: osa1 | Owner: Type: bug | Status: merge Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: | codegen/should_compile/T12115 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by thomie): This patch is causing the following panic in `tcrun051` (on Linux): {{{ [1 of 1] Compiling Main ( tcrun051.hs, tcrun051.o ) 7907 ghc: panic! (the 'impossible' happened) 7908 (GHC version 8.1.20160527 for x86_64-unknown-linux): 7909 unboxed tuple PrimRep 7910 7911 Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug 7912 7913 7914 *** unexpected failure for tcrun051(normal) 7915 }}} tcrun051.hs: {{{#!hs {-# LANGUAGE UnboxedTuples #-} module Main where -- Tests unboxed tuple slow calls {-# NOINLINE g #-} g :: Int -> (# Int, Int #) -> Int -> (# Int, (# Int #) #) -> (# #) -> Int g a (# b, c #) d (# e, (# f #) #) (# #) = a + b + c + d + e + f {-# NOINLINE h #-} h :: (Int -> (# Int, Int #) -> Int -> (# Int, (# Int #) #) -> (# #) -> Int) -> (Int, Int) h g = (g5, g5') where -- Apply all the arguments at once g5' = g 1 (# 2, 3 #) 4 (# 5, (# 6 #) #) (# #) -- Try to force argument-at-a-time application as a stress-test g1 = g 1 g2 = g1 `seq` g1 (# 2, 3 #) g3 = g2 `seq` g2 4 g4 = g3 `seq` g3 (# 5, (# 6 #) #) g5 = g4 `seq` g4 (# #) main = print $ h g }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12115#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#12115: CoreLint error in safe program -------------------------------------+------------------------------------- Reporter: osa1 | Owner: Type: bug | Status: merge Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: | codegen/should_compile/T12115 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Simon Peyton Jones ): In [changeset:"b43a7936ebf77bce744d50a131d686c83f63e60b/ghc" b43a793/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="b43a7936ebf77bce744d50a131d686c83f63e60b" More fixes for unboxed tuples This is a continuation of commit e9e61f18a548b70693f4ccd245bc56335c94b498 Date: Thu May 26 15:24:53 2016 +0100 Reduce special-casing for nullary unboxed tuple which related to Trac #12115. But typecheck/should_run/tcrun051 revealed that my patch was incomplete. This fixes it, by removing another special case in Type.repType. I had also missed a case in UnariseStg.unariseIdBinder. I took the opportunity to add explanatory notes Note [Unarisation] Note [Unarisation and nullary tuples] in UnariseStg }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12115#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#12115: CoreLint error in safe program -------------------------------------+------------------------------------- Reporter: osa1 | Owner: Type: bug | Status: merge Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: | codegen/should_compile/T12115 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire): I'm a bit lost with these patches. - The commentary says that `(# #)` becomes `Void#` during unarisation. But there is also a change in !TysWiredIn that removes the special case for nullary unboxed tuples. - `Note [The kind invariant]` is awfully out-of-date: {{{ Note [The kind invariant] ~~~~~~~~~~~~~~~~~~~~~~~~~ The kinds # UnliftedTypeKind OpenKind super-kind of *, # can never appear under an arrow or type constructor in a kind; they can only be at the top level of a kind. It follows that primitive TyCons, which have a naughty pseudo-kind State# :: * -> # must always be saturated, so that we can never get a type whose kind has a UnliftedTypeKind or ArgTypeKind underneath an arrow. Nor can we abstract over a type variable with any of these kinds. k :: = kk | # | ArgKind | (#) | OpenKind kk :: = * | kk -> kk | T kk1 ... kkn So a type variable can only be abstracted kk. }}} (I'm sure I'm implicated in letting this fall out-of-date. But I honestly don't know how to fix.) There is no `#` anymore, and there is no `OpenKind` anymore. One might think this means that a representation-polymorphic kind (that is, `TYPE r`) cannot appear below top-level, but indeed they do, as in the type of `error`. So I'm not sure what this is saying. Also, this Note is missing ''why'' these restrictions are in place. I recall several months ago moving to allow unsaturated unlifted things, but now we've backpedaled on this decision. I'm sure there's a good reason, but what is it? This Note is also missing ''where'' these restrictions are enforced. Is there a check in !CoreLint that we never abstract over a kind `* -> TYPE <something unlifted>`? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12115#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#12115: CoreLint error in safe program -------------------------------------+------------------------------------- Reporter: osa1 | Owner: Type: bug | Status: closed Priority: normal | Milestone: 8.0.2 Component: Compiler | Version: 8.0.1 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: | codegen/should_compile/T12115 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by bgamari): Opened #12536 to track the task of addressing comment:8. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12115#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler