[bitc-dev] CLEANUP: pragmatics of closure conversion

[Swaroop Sridhar]

Jonathan S. Shapiro wrote:
> Rules: Given a lambda form L and some /id/ that is free in L:
> 
>   PHASE I: INITIAL CLOSURE CONSTRUCTION
> 
>   1. If /id/ resolves to a globally defined identifier, stop. No
>      globally resolved identifier is ever inserted into a closure
>      record.
>   2. If /id/ is locally bound:
>      A. if /id/ is mutable, it must be heap-converted, and the reference
>         to the heap-converted object must be included in the closure
>         record.

Just to be super-precise, the /id/ must be heap converted only if it is
shallowly mutable. If the mutability is within a reference in the value
denoted by /id/ right?

>      B. if /id/ is non-mutable but of non-reference type, it must be
>         heap-converted and the reference to the heap-converted object
>         must be included in the closure record.
>      C. if /id/ is non-mutable and of reference type, a copy of /id/
>         must be included in the closure record.

Is the fact that the immutable unboxed values are closure converted as a
matter optimization (so that the closure record is small)?
   If so, we can say that heap-conversion is not necessary for primitive
   scalar values like int, bool, etc.

   Otherwise, we can place copies of immutable unboxed values in the
   closure. That is, handle B and C the same way.

Swaroop.