[llvm] [LAA][NFC] Add a test for #191867 (PR #213722)

[Ramkumar Ramachandra via llvm-commits]

================
@@ -348,6 +348,106 @@ exit:
   ret void
 }
 
+; Same as above but with an unrelated store-to-load forwarding deps that do have
+; a safe VF. Make sure those aren't reported as
+; `BackwardVectorizableButPreventsForwarding`. We provide two of those (%B and
+; %C) becase the order of processing matters, so we have one lexically before %A
+; and another after it.
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artagnon wrote:

```suggestion
; `BackwardVectorizableButPreventsForwarding`. We provide two of those (%A and
; %C) becase the order of processing matters, so we have one lexically before %B
; and another after it.
```

Would be good to line up lexical ordering with names as well?

https://github.com/llvm/llvm-project/pull/213722