[Mlir-commits] [mlir] [mlir][Interfaces] Add `ExecutionProgressOpInterface` + folding pattern (PR #179039)

[Matthias Springer]

matthias-springer wrote:

> I'm not sure it's safe to mark loops as `mustprogress` by default without looking at their body first which may contain operations that may not progress.

I believe this is at least well-defined. It doesn't matter what's inside of the loop. If the loop is "mustProgress", but something inside of the loop violates that property, we have UB and the loop can be replaced with `ub.poison`.

(Whether "mustProgress = true" should be the default... I agree, I would also feel more comfortable with `false` being the default.)

> For example, what if we have a nested loop where the inner one is marked as `mustProgress=false`? I'm not sure it's reasonable for the emitted of the outer loop to be responsible for deciding this -- seems like a footgun.

Note that this loop structure is not contradicting.
```
loop must_progress=true {
  loop must_progress=false {
    ...
  }
}
```

`must_progress=false` just means that we have no information.

> had a cannon pattern to set `mustProgress` when safe?

That sounds like a reasonable canonicalization to me.


https://github.com/llvm/llvm-project/pull/179039