[llvm] [DA] Overflow check in WeakCrossing Delta calculation (PR #185046)

[Michael Kruse via llvm-commits]

================
@@ -1387,7 +1387,10 @@ bool DependenceInfo::weakCrossingSIVtest(const SCEVAddRecExpr *Src,
   ++WeakCrossingSIVapplications;
   assert(0 < Level && Level <= CommonLevels && "Level out of range");
   Level--;
-  const SCEV *Delta = SE->getMinusSCEV(DstConst, SrcConst);
+  const SCEV *Delta = minusSCEVNoSignedOverflow(DstConst, SrcConst, *SE);
+  if (Delta == nullptr)
+    return false;
----------------
Meinersbur wrote:

```suggestion
  if (!Delta)
    return false;
```
[nit] consistent style with e.g. `if (!ConstCoeff)` below

https://github.com/llvm/llvm-project/pull/185046