[llvm] [VPlan] Verify and handle FOR legality during header phi creation (NFC). (PR #191298)

[Mel Chen via llvm-commits]

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@@ -717,7 +717,205 @@ createWidenInductionRecipe(PHINode *Phi, VPPhi *PhiR, VPIRValue *Start,
   return WideIV;
 }
 
-void VPlanTransforms::createHeaderPhiRecipes(
+/// Try to sink users of \p FOR after \p Previous.  \returns true if sinking
----------------
Mel-Chen wrote:

```suggestion
/// Try to sink users of \p FOR after \p Previous. \returns true if sinking
```

https://github.com/llvm/llvm-project/pull/191298