[llvm] [DomTree] Reduce number of hash table lookups (NFC) (PR #73097)

[Nikita Popov via llvm-commits]

nikic wrote:

I don't think adding tests of that kind would be appropriate -- we should only test public API behavior, not implementation details. How many hash lookups the domtree implementation performs is a pure implementation detail, that we don't (and shouldn't) make any guarantees about. This isn't even something that affects the asymptotic computational complexity (something that could be considered an API guarantee), it "only" affects the constant factor.

https://github.com/llvm/llvm-project/pull/73097