[llvm] [WIP][LSR][term-fold] Configure expander to avoid introducing new IVs (PR #80197)

[Craig Topper via llvm-commits]

topperc wrote:

This patch doesn't prevent generating IVs in the outer loops. Here's an example where this patch will cause an IV to be created https://godbolt.org/z/d74Yfnnxz

In the benchmark I reduced this from, the dynamic count did improve by creating the new IV. I guess the new IV was better than the `mul` and `getelementptr` terminator folding added to the outer loop.

https://github.com/llvm/llvm-project/pull/80197