[llvm] [DFAJumpThreading] Add an early exit heuristic for unpredictable values (PR #85015)

[Usman Nadeem via llvm-commits]

UsmanNadeem wrote:

Rebase and add check for subloops.
New compile-time after rebasing with @XChy's patch.

https://github.com/llvm/llvm-project/pull/85015