So if I understand correctly, OtherCon is only created
here:https://gitlab.haskell.org/ghc/ghc/-/blob/a952dd80d40bf6b67194a44ff71d7bf75957d29e/co
mpiler/GHC/Core/Opt/Simplify.hs#L3071-3077
simplAlt env _ imposs_deflt_cons case_bndr' cont' (Alt DEFAULT bndrs
rhs)
= assert (null bndrs) $
do { let env' = addBinderUnfolding env case_bndr'
(mkOtherCon imposs_deflt_cons)
-- Record the constructors that the case-binder
*can't* be.
; rhs' <- simplExprC env' rhs cont'
; return (Alt DEFAULT [] rhs') }
What you should know is that in Core case-expressions are actually
more like:
case scrut as b of alts
where `b` binds the evaluated result of `scrut.
So if I am to understand the `simplAlt` code correctly, `case_bndr'`
is the binder for
the evaluated result of `scrut`.
And what is recorded in the unfolding is that once we get to the
DEFAULT pattern, we
know that `case_bndr'` cannot be the constructors in
`imposs_deflt_cons` (probably the
constructor matched by the other alternatives).
Now... there's also a FloutOut pass, which might have floated that
`case_bndr'` to the
TopLevel.
And I think that is what you're seeing, and I think you can simply
ignore them.
Also... another thing that you should know is that
-fexpose-all-unfoldings doesn't
actually expose *all* unfoldings.
Bottoming bindings are never exposed.
That's why in the Clash compiler we have the following code when loading
core-expressions from .hi
fileshttps://github.com/clash-lang/clash-compiler/blob/cb93b418865e244da50e1d2bc85fbc01bf7
61f3f/clash-ghc/src-ghc/Clash/GHC/LoadInterfaceFiles.hs#L473-L481
loadExprFromTyThing :: CoreSyn.CoreBndr -> GHC.TyThing -> Maybe
CoreSyn.CoreExpr
loadExprFromTyThing bndr tyThing = case tyThing of
GHC.AnId _id | Var.isId _id ->
let _idInfo = Var.idInfo _id
unfolding = IdInfo.unfoldingInfo _idInfo
in case unfolding of
CoreSyn.CoreUnfolding {} ->
Just (CoreSyn.unfoldingTemplate unfolding)
CoreSyn.DFunUnfolding dfbndrs dc es ->
Just (MkCore.mkCoreLams dfbndrs (MkCore.mkCoreConApps dc es))
CoreSyn.NoUnfolding
#if MIN_VERSION_ghc(9,0,0)
| Demand.isDeadEndSig $ IdInfo.strictnessInfo _idInfo
#else
| Demand.isBottomingSig $ IdInfo.strictnessInfo _idInfo
#endif
-> do
let noUnfoldingErr = "no_unfolding " ++ showPpr
unsafeGlobalDynFlags bndr
Just (MkCore.mkAbsentErrorApp (Var.varType _id)
noUnfoldingErr)
_ -> Nothing
_ -> Nothing
i.e. when we encounter a NoUnfolding with a bottoming demand
signature, we conjure an
absentError out of thin air.
On Fri, 1 Apr 2022 at 10:05, ÉRDI Gergő <ge...@erdi.hu> wrote:
Hi,
I'm CC-ing the Clash mailing list because I believe they should
have
encountered the same problem (and perhaps have found a solution
to it
already!).
I'm trying to use `.hi` files compiled with
`ExposeAllUnfoldings` set to
reconstruct full Core bindings for further processing. By and
large, this
works, but I get tripped up on identifiers whose unfolding is
only given
as `OtherCon []`. It is unclear to me what is causing this --
some of them
are recursive bindings while others are not.
The problem, of course, is that if all I know about an
identifier is that
it is `OtherCon []`, that doesn't allow me to restore its
definition. So
is there a way to tell GHC to put "full" unfoldings everywhere in
`ExposeAllUnfoldings` mode?
Thanks,
Gergo
--
You received this message because you are subscribed to the
Google Groups
"Clash - Hardware Description Language" group.
To unsubscribe from this group and stop receiving emails from
it, send an
email to clash-language+unsubscr...@googlegroups.com.
To view this discussion on the web
visithttps://groups.google.com/d/msgid/clash-language/alpine.DEB.2.22.394.2204011556570.31
83073%40galaxy.
