let/app invariant violated by code generated with mkCoreApp
Dr. ÉRDI Gergő
gergo at erdi.hu
Wed Nov 12 02:23:47 UTC 2014
Yep, that seems to work. I'll add a note explaining why we need unfoldings
On Nov 11, 2014 10:14 PM, "Simon Peyton Jones" <simonpj at microsoft.com>
> Oh bother, that is _so_ tiresome. The desugarer establishes the let/app
> invariant, so we get
> I# x_help
> but if x_help has a compulsory unfolding to (x void), returning an Int#,
> that violates the let/app invariant. Sigh. This is a ridiculous amount of
> work for a tiny corner (pattern synonyms for unboxed constants).
> Harump. Let's see. We are talking only of things like this
> pattern P = 4#
> correct? Perhaps it may be simpler to make the psWrapper in PatSyn be
> psWrapper :: Either Id Literal
> and treat such patterns specially from the moment we first see them? That
> would eliminate all this void stuff entirely.
> Pursuing the current line, though, I suppose that the desugarer could
> inline compulsory unfoldings during desugaring itself. In this line, add a
> case for when var has a compulsory unfolding.
> dsExpr (HsVar var) = return (varToCoreExpr var) -- See Note
> [Desugaring vars]
> That would, I suppose, be the quickest pathc.
> | -----Original Message-----
> | From: ghc-devs [mailto:ghc-devs-bounces at haskell.org] On Behalf Of Dr.
> | ERDI Gergo
> | Sent: 08 November 2014 14:03
> | To: GHC Devs
> | Subject: let/app invariant violated by code generated with mkCoreApp
> | Hi,
> | I'm trying to attach (f Void#) as a compulsory unfolding to an Id.
> | Here's what I tried originally:
> | let unfolding = mkCoreApp (Var worker_id) (Var voidPrimId)
> | wrapper_id' = setIdUnfolding wrapper_id $
> | mkCompulsoryUnfolding unfolding
> | However, when I try to use wrapper_id' in the desugarer, the Core
> | linter looks at me strange. This is the original Core:
> | f :: Int
> | [LclIdX, Str=DmdType]
> | f = break<1>() GHC.Types.I# Main.$WPAT
> | and this is the error message ($WPAT is the wrapper_id', PAT is the
> | worker_id in this example)
> | <no location info>: Warning:
> | In the expression: I# (PAT void#)
> | This argument does not satisfy the let/app invariant: PAT void#
> | Now, I thought I'd make sure mkCoreApp generated correct Core by
> | writing it out by hand:
> | let unfolding = Case (Var voidPrimId) voidArgId pat_ty
> | [(DEFAULT,,App (Var worker_id) (Var voidArgId))]
> | however, bizarrely, this *still* results in *the same* error message,
> | as if something was transforming it back to a straight App.
> | Anyone have any hints what I'm doing wrong here?
> | Bye,
> | Gergo
> | --
> | .--= ULLA! =-----------------.
> | \ http://gergo.erdi.hu \
> | `---= gergo at erdi.hu =-------'
> | You are in a twisty maze of little install diskettes.
> | _______________________________________________
> | ghc-devs mailing list
> | ghc-devs at haskell.org
> | http://www.haskell.org/mailman/listinfo/ghc-devs
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the ghc-devs