[llvm] [LoopInterchange] Relax legality check to accept `[* =]` or `[= *]` (PR #193480)

[Michael Kruse via llvm-commits]

================
@@ -372,6 +372,21 @@ static bool isLegalToInterChangeLoops(CharMatrix &DepMatrix,
     if (isLexicographicallyPositive(Cur, 0, OuterLoopId) == true)
       continue;
 
+    // For the adjacent loops, if at least one of their direction is '=' or
+    // 'I', interchanging them is legal regardless of the diction of the other.
----------------
Meinersbur wrote:

```suggestion
    // 'I', interchanging them is legal regardless of the direction of the other.
```

https://github.com/llvm/llvm-project/pull/193480