[llvm] [VPlan] Make CanIV part of region. (PR #144803)

[via llvm-commits]

================
@@ -942,7 +969,12 @@ VPlan::~VPlan() {
         for (unsigned I = 0, E = R.getNumOperands(); I != E; I++)
           R.setOperand(I, &DummyValue);
       }
+    } else {
+      if (cast<VPRegionBlock>(VPB)->getCanonicalIV())
+        cast<VPRegionBlock>(VPB)->getCanonicalIV()->replaceAllUsesWith(
+            &DummyValue);
     }
----------------
ayalz wrote:

```suggestion
    } else if (auto *CanIV = cast<VPRegionBlock>(VPB)->getCanonicalIV()) {
      CanIV->replaceAllUsesWith(&DummyValue);
    }
```

https://github.com/llvm/llvm-project/pull/144803