[llvm] [LICM][MustExec] Make must-exec logic for IV condition commutative (PR #93150)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

> I'm not sure what else can be done about that test.

Can we truncate the count?  I mean, the math in howManyLessThans doesn't fit into i64, but does the actual backedge-taken count overflow 64 bits?

https://github.com/llvm/llvm-project/pull/93150