[llvm] [DA] Check monotonicity for subscripts (PR #154527)

[Ryotaro Kasuga via llvm-commits]

https://github.com/kasuga-fj commented:

Most of the changes in test results are due to a failure to detect the lack of dependencies in patterns like the ones below:

```c
for (int i = 0; i < n; i++)
  for (int j = 0; j < m; j++)
    *B++ = ...;
```

At a glance, handling this case seems to require non-trivial effort, so if I do address it, I'd prefer to do it in a separate PR.

I've commented on the other cases individually.

https://github.com/llvm/llvm-project/pull/154527