[llvm] [IndVars] Fix high-cost-expand check in LFTR (PR #125828)

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

Gentle ping. I think we ultimately want https://github.com/llvm/llvm-project/pull/126086, although we're still undecided on it, but I think this PR will give us many small improvements, and I think it is a step in the right direction.

https://github.com/llvm/llvm-project/pull/125828