[llvm] [PredicateInfo] Support `PredicateInfo` by adding `PHI` nodes that pick up info from created branch predicates (PR #151132)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

> I don't know about the accuracy of this benchmark but I had put this earlier:

opt-bench doesn't provide any metric. It just shows IR diff for several real-world projects.
For compile-time overhead, you can use https://llvm-compile-time-tracker.com/. But this patch causes the stage2 build to fail: https://llvm-compile-time-tracker.com/show_error.php?commit=446351e22d0e4adf882551dbd3d2ced40ed8219e 

https://github.com/llvm/llvm-project/pull/151132