Joachim Breitner
Hi,
Am Sonntag, den 11.06.2017, 10:44 -0400 schrieb Ben Gamari:
This is certainly one consideration. Another is that you would also need to teach the garbage collector to understand closures with sub- word-size fields. Currently we can encode whether each field of a closure is a pointer or not with a simple bitmap. If we naively allowed smaller fields we would need to increase the granularity of this representation to encode bytes.
Of course, one way to work around this would be to impose an invariant that guarantees that pointers are always word-aligned. Then we would probably want to shuffle sub-word sized fields, allowing two Word16s to inhabit a single word.
that is not an issue; we already sort field into pointers first, and non-pointers later. So all pointers are at the beginning and nicely aligned, and all the non-pointer data can follow in whatever weird format. The GC only needs to know how many words in total are used by the non-pointer data.
Ahh, great point. I stand corrected. Cheers, - Ben