[Mlir-commits] [mlir] [mlir][linalg] Account for preserved outs in fusion bounds (PR #228467)

[llvmlistbot at llvm.org]

https://github.com/MaheshRavishankar requested changes to this pull request.

Sorry, I think I need a bit more context on this change. Could you please provide that? Some of the examples added here for lit-tests are not necessarily caught as invalid by Linalg right now, but they are a bit ill-formed. For example take this operation

```
linalg.generic {
    indexing_maps = [affine_map<(d0, d1) -> ()>, affine_map<(d0, d1) -> (d0, d1)>,
                                     affine_map<(d0, d1) -> (d0)],
    iterator_types = ["parallel", "parallel"]}
    ins(%a : tensor<f32>) outs(%b, %c : tensor<?x?xf32>, tensor<?xf32>) ->
        (tensor<?x?xf32>, tensor<?xf32>)
```

this is inherently problematic cause if you write this as loops you get

```
for (i = ...) { // parallel
   for (j = ...) { // parallel
       b[i][j] = ...
       c[j] = ...
   }
}       
```

This is a race condition on `c`. Now Linalg operations inherently dont disallow that (maybe they should).

My issue with this change is something that was disallowed by default, is now allowed and the resulting operation's semantics isnt clear. 

https://github.com/llvm/llvm-project/pull/228467