Finding Reduction Variables in a Loop

Hello everyone,

I’m trying to find reduction variables in a loop and I have a couple of questions about it.

Is it necessary that a reduction variable should be associated with a Phi node?

For my purpose, I tried using isReductionPHI() from LoopUtils.cpp (that is used by LoopVectorizer) for a toy C program (find below) that has a clear reduction variable but it still returns false.