[llvm] [VPlan] Add VPPhiAccessors to provide interface for phi recipes (NFC) (PR #129388)

[Florian Hahn via llvm-commits]

================
@@ -1031,6 +1031,29 @@ void VPIRInstruction::print(raw_ostream &O, const Twine &Indent,
 }
 #endif
 
+static const VPBasicBlock *getIncomingBlockForRecipe(const VPRecipeBase *R,
----------------
fhahn wrote:

Updated to use `Idx` consistently.

https://github.com/llvm/llvm-project/pull/129388