[llvm] [VPlan] Use scalar VPPhi instead of VPWidenPHIRecipe in createPlainCFG. (PR #150847)

[via llvm-commits]

================
@@ -207,8 +205,8 @@ void PlainCFGBuilder::createVPInstructionsForVPBB(VPBasicBlock *VPBB,
       // Phi node's operands may have not been visited at this point. We create
       // an empty VPInstruction that we will fix once the whole plain CFG has
       // been built.
-      NewR = new VPWidenPHIRecipe(Phi, nullptr, Phi->getDebugLoc(), "vec.phi");
-      VPBB->appendRecipe(NewR);
+      NewR = VPIRBuilder.createScalarPhi({}, Phi->getDebugLoc(), "vec.phi");
----------------
ayalz wrote:

Ok, may be good to clarify/document the distinction between VPWidenPHIRecipe and VPPhi - the former holds for VF>1 and/or UF>1, the latter holds for scalar, VF=UF=1, currently?

Would be good to resolve the discrepancy between buildScalarPhi and VPPhi, one way or another, if they continue to be synonymous.

https://github.com/llvm/llvm-project/pull/150847