[llvm] [LVI] Handle icmp of ashr. (PR #68010)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

Basically okay, but I think the constants in the tests need to be adjusted from `icmp sge i8 %s, 0` to some other value like `icmp sge i8 %s, 1`. The zero constant is a bad choice because shifting zero gives you zero again, so the correct adjustment of the constant isn't tested for all predicates.

https://github.com/llvm/llvm-project/pull/68010