Non-escaping lets, join-points and binding updatability

Nicolas Frisby nicolas.frisby at
Wed Oct 16 20:42:56 UTC 2013

If I understand correctly, the LNE-detection in CoreToSTG makes all of the
decisions; it's the only place that the StgLetNoEscape constructor arises.

Join-points are only implemented as LNE if they are detected to be LNE,
which they most often — but not always! — after all the core2core
simplification are.

I have seen let-bindings with no parameters be detected as LNE.


On Wed, Oct 16, 2013 at 11:27 AM, Jan Stolarek <jan.stolarek at>wrote:

> Hi all,
> I'm trying to understand this:
> 1. Note [What is a non-escaping let] says that one of conditions of
> binding being a non-escaping
> let is non-updatability.
> 2. My understanding is that a if a binding has at least one parameter it
> is non-updatable, though
> I suspect that converse does not have to be true (lambdas)
> 3. Join-points are implemented using LNE bindings and I can imagine a
> join-points not having any
> parameters (and not being a lambda).
> Three points above seem inconsistent - where does my reasoning go wrong? I
> suspect that the Note
> might be wrong and an updatable binding can in fact be a LNE binding.
> Janek
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