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

[via llvm-commits]

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@@ -2890,11 +2890,8 @@ void InnerLoopVectorizer::fixNonInductionPHIs(VPTransformState &State) {
       PHINode *NewPhi = cast<PHINode>(State.get(VPPhi));
       // Make sure the builder has a valid insert point.
       Builder.SetInsertPoint(NewPhi);
-      for (unsigned Idx = 0; Idx < VPPhi->getNumOperands(); ++Idx) {
-        VPValue *Inc = VPPhi->getIncomingValue(Idx);
-        VPBasicBlock *VPBB = VPPhi->getIncomingBlock(Idx);
+      for (const auto &[Inc, VPBB] : VPPhi->incoming_values_and_blocks())
         NewPhi->addIncoming(State.get(Inc), State.CFG.VPBB2IRBB[VPBB]);
-      }
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ayalz wrote:

Is this return (in simplification?) worth the investment. Would an API of `getIncomingValue(Idx)`, `getIncomingBlock(Idx)`, and possibly `getNumIncomings()` common to all phi recipes suffice.

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