[llvm] [VPlan] Consistently use (Part, 0) for first lane scalar values (PR #80271)

[via llvm-commits]

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@@ -9127,7 +9127,7 @@ void VPWidenPointerInductionRecipe::execute(VPTransformState &State) {
          "Unexpected type.");
 
   auto *IVR = getParent()->getPlan()->getCanonicalIV();
-  PHINode *CanonicalIV = cast<PHINode>(State.get(IVR, 0));
+  PHINode *CanonicalIV = cast<PHINode>(State.get(IVR, VPIteration(0, 0)));
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ayalz wrote:

```suggestion
  PHINode *CanonicalIV = cast<PHINode>(State.get(IVR, 0, true /* scalar */));
```

https://github.com/llvm/llvm-project/pull/80271