[llvm-branch-commits] [mlir] [mlir][UB] Erase ops that precede `ub.unreachable` (PR #179104)

[Matthias Springer via llvm-branch-commits]

matthias-springer wrote:

@kuhar Here we have a problem:
```
func.func @foo() {
  if ... {
    spirv.Kill
  }
  ub.unreachable
}
```

We would erase the `spriv.Kill` operation.

https://github.com/llvm/llvm-project/pull/179104