Unboxed static pointers lead to missing SPT entries
I found what appears to be a regression following the merge of the new FloatOut based static pointers support. See https://github.com/mboes/bug-ptr-not-in-spt for a fully developed minimal example.
It seems to be quite hard to trigger this bug:
- I need to be using distributed-closure (not bare
- The static pointer needs to be defined in a separate module.
- The static pointer must refer to a value with at least one polymorphic argument.
- Compiler optimization level 1 needs to be turned on.
At any rate, I wasn't able to trigger it without all conditions above being true. Initial investigations by facundominguez point to static pointer unpacking in distributed-closure as the culprit. Likely unpacked static pointers are no longer recognized as such by the FloatOut pass and therefore never floated to top-level, hence breaking a fundamental invariant about static pointers.
This might explain why sometimes static pointers don't get added to the static pointer table (SPT), as in the above minimal example.