[llvm] [LVI][ValueTracking] Take UB-implying attributes into account in `isSafeToSpeculativelyExecute` (PR #137604)

[Nikita Popov via llvm-commits]

nikic wrote:

It's a shame that this introduces a case where more attributes results in less optimization. The high level alternative here would be to instead to do something like we do with DropFlags on simplifyWithOpReplaced, just for dropping UB-implying flags in this case. Let's see what llvm-opt-benchmark says, but probably the extra complexity of that approach is not worth it.

https://github.com/llvm/llvm-project/pull/137604