[GC] GUFA: Handle function subtyping #8112
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tlively
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Dec 10, 2025
src/ir/possible-contents.cpp
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| // Subtyping info. | ||
| SubTypes* subTypes; |
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Can we use a reference here to make it impossible to fail to initialize this?
tlively
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Dec 11, 2025
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We were ignoring subtyping entirely, that is, the pass didn't realize that
an indirect call to a type might call something of a subtype. That situation
seems to not be common in practice, given we've never gotten a bug
report.
We could fully optimize this as we do data reads and writes: we could
consider the type of the flowing reference in CallRef (but not CallIndirect), etc.
However, for now do the far simpler thing and use the static type to connect
results to subtypes as needed.
For params, do something even simpler: Just hook them up at the type
level, which ignores exactness (as this would require even more work to
optimize, see TODO in the code).