[llvm] Fix exact backedge count algorithm in Scalar-Evolution (PR #92560)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

I don't see anything obviously wrong in your example; probably something simple is going wrong.  Are you sure the expressions you're computing match the condition? Maybe try setting a breakpoint on ScalarEvolution::isImpliedCondBalancedTypes and step through.

https://github.com/llvm/llvm-project/pull/92560