Bug in SRT generation for procs in .cmm files?

[Simon Marlow]

Yes, I think my assumption was that we wouldn't be referring to any CAFs
from .cmm source code so we didn't need to track the CAFyness of labels. It
would be quite a pain to support this I think - in .cmm you can refer to
anything by its raw label, so we would have to either declare whether
something is CAFy or reverse engineer the original entity name and load the
interface file etc.  Furthermore we would need to tell the compiler about
the CAFyness of RTS labels somehow so that they could be added to SRTs
where necessary.

I'm fine with not running the SRT analysis on .cmm code.

Cheers
Simon


On Thu, 23 Jan 2020 at 14:57, Ömer Sinan Ağacan <omeragacan at gmail.com>
wrote:

> The main problem I'm trying to solve is explained in my comment [1].
> Basically
> when building .cmm files the new SRT algorithm re-order definitions in a
> way
> that breaks dependency ordering, which in turn breaks C backend, because
> in C we
> should declare before using. (see my comment for why we don't have this
> problem
> when building Haskell modules)
>
> If we don't allow defining CAFFY things in Cmm files then I can simply not
> do
> SRT analysis on Cmm files and avoid the problem.
>
> Ömer
>
> [1]: https://gitlab.haskell.org/ghc/ghc/merge_requests/1304#note_248547
>
> Ben Gamari <ben at well-typed.com>, 23 Oca 2020 Per, 15:17 tarihinde şunu
> yazdı:
> >
> > While it's true that in principle one could imagine a case where you
> would want a CAFfy Cmm proc, I can't think of any stuck cases in the RTS
> today. Consequently it wouldn't surprise me if this was broken.
> >
> > Frankly, I wouldn't worry too much about this if it's nontrivial to fix.
> >
> > Cheers,
> >
> > - Ben
> >
> > On January 23, 2020 1:54:04 AM EST, "Ömer Sinan Ağacan" <
> omeragacan at gmail.com> wrote:
> >>
> >> Hi Simon,
> >>
> >> Currently CmmParse only generates CmmLabels for procs, and those are
> considered
> >> non-CAFFY by hasCAF (and thus CmmBuildInfoTables).
> >>
> >> As a result if I have two procs in a .cmm file:
> >>
> >> - p1, refers to a CAF in base
> >> - p2, refers to p1
> >>
> >> I *think* (haven't checked) we don't consider p1 as CAFFY, and even if
> we do, we
> >> don't consider p2 as CAFFY becuase the reference from p2 to p1 won't be
> >> considered CAFFY by hasCAF.
> >>
> >> So we currently can't define a CAFFY Cmm proc in .cmm files as the SRT
> algorithm
> >> will never build SRTs for procs in .cmm files.
> >>
> >> Is this intentional? I'd expect this to be possible, because there's
> nothing
> >> preventing me from referring to a CAFFY definition in a library (e.g.
> base) in a
> >> .cmm file, but doing this would be a bug in runtime.
> >>
> >> Thanks,
> >>
> >> Ömer
> >> ________________________________
> >> ghc-devs mailing list
> >> ghc-devs at haskell.org
> >> http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs
> >
> >
> > --
> > Sent from my Android device with K-9 Mail. Please excuse my brevity.
>
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