[llvm] [VPlan] Implement interleaving as VPlan-to-VPlan transform. (PR #95842)

[via llvm-commits]

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@@ -1254,6 +1262,10 @@ void VPlanIngredient::print(raw_ostream &O) const {
 
 template void DomTreeBuilder::Calculate<VPDominatorTree>(VPDominatorTree &DT);
 
+bool VPValue::isDefinedOutsideVectorRegions() const {
+  return !hasDefiningRecipe() || !getDefiningRecipe()->getParent()->getParent();
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ayalz wrote:

```suggestion
  return !hasDefiningRecipe() || !getDefiningRecipe()->getParent()->getEnclosingLoopRegion();
```
?
Although replicate regions are expected to be nested inside loop regions.

Would be good to align "VectorRegions" and "LoopRegion" terms consistently.

https://github.com/llvm/llvm-project/pull/95842