WebAssembly / WebAssembly/binaryen
PossibleContents is not a lattice
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Description
IIUC, we have this structure:
Type(i32)
/ \
Global("g1", i32) Global("g2", i32)
| X |
Literal(1) Literal(2)
There is no unique least upper bound of the two literals and there is no unique greatest lower bound of the two globals. This is a problem because union and intersect are supposed to calculate unique least upper / greatest lower bounds.
I think there is a probably a way to solve this, but I'll have to think on it.
I ran into this while trying to simplify and complete the implementation of intersect as part of the investigation suggested here: https://github.com/WebAssembly/binaryen/pull/7538/files#r2054860951
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Read the PossibleContents lattice model and the intersect investigation referenced in WebAssembly/binaryen#7538. Compare the intended behavior of union and intersect for the shown literals and globals; done means the model has a decided resolution for their least upper and greatest lower bounds.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- cpp
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 5/5
- Estimated time
- Over a week
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 25/100