PUBLIC
Just so this isn't prematurely all lost, I went back and looked for this
example. With the following two definitions:
subsequences :: [a] -> [[a]]
subsequences xs = [] : nonEmptySubsequences xs
nonEmptySubsequences :: [a] -> [[a]]
nonEmptySubsequences [] = []
nonEmptySubsequences (x:xs) = [x] : foldr f [] (nonEmptySubsequences xs)
where f ys r = ys : (x : ys) : r
If I save the interface, load it back and look at the unfoldings, I see that
`subsequences` has a useful unfolding:
subsequences Unf{Src=<vanilla>, TopLvl=True, Value=True,
ConLike=True, WorkFree=True, Expandable=True,
Guidance=IF_ARGS [0] 30 10}
Whereas `nonEmptySubsequenes` has a trivial one:
nonEmptySubsequences OtherCon []
The interface I save is created from the ModDetails returned by tidyProgram.
ExposeAllUnfoldings is set.
Unfortunately, I am unable to reproduce this from the command line using the
GHC executable, so before I put in the effort of making a minimal example of
using the GHC API to get this result, I would first like to know if this is
even an interesting case, or if there is some explanation for why one of these
two would have an unfolding when the other doesn't, in certain cases.
-----Original Message-----
From: ghc-devs <ghc-devs-boun...@haskell.org> On Behalf Of Gergo Érdi
Sent: Saturday, April 2, 2022 11:31 AM
To: Simon Peyton Jones <simon.peytonjo...@gmail.com>
Cc: GHC Devs <ghc-devs@haskell.org>; clash-langu...@googlegroups.com
Subject: [External] Re: Avoiding `OtherCon []` unfoldings, restoring
definitions from unfoldings
I'm using Prep's output (mostly so that it's in ANF) in my full compilation
pipeline, so ideally I would save Prep'd Core in my .hi-equivalents so that I
don't have to rerun Prep on them every time I use them.
I'll get back to you with some concrete examples of `OtherCon []` vs.
meaningful unfoldings next week.
Merging with my other question about shadowing problems with `toIface*`, in
summary it seems that what I really should be doing, is compiling up to Tidy,
taking the `CoreBinding`s from there and using `toIfaceBinding` on them to save
the definitions.
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