GHC 8.10 backports?

[Viktor Dukhovni]

On Mon, Mar 22, 2021 at 12:39:28PM +0800, Gergő Érdi wrote:

> I'd love to have this in a GHC 8.10 release:
> https://mail.haskell.org/pipermail/ghc-devs/2021-March/019629.html

This is already in 9.0, 9.2 and master, but it is a rather non-trivial
change, given all the new work that went into the String case.  So I am
not sure it is small/simple enough to make for a compelling backport.

There's a lot of recent activity in this space.  See also
<https://gitlab.haskell.org/ghc/ghc/-/merge_requests/5259>, which is not
yet merged into master, and might still be eta-reduced one more step).

I don't know whether such optimisation tweaks (not a bugfix) are in
scope for backporting, we certainly need to be confident they'll not
cause any new problems.  FWIW, 5259 is dramatically simpler...

Of course we also have
<https://gitlab.haskell.org/ghc/ghc/-/merge_requests/4890> in much the
same territory, but there we're still blocked on someone figuring out
what's going on with the 20% compile-time hit with T13056, and whether
that's acceptable or not...

-- 
    Viktor.