[llvm] [SimplifyCFG] Hoist out implied conditions from successor (PR #158773)

[Vedant Paranjape via llvm-commits]

VedantParanjape wrote:

> The problem is not with the icmps, it's with the control flow. Note that in the test case from #155986 the icmp in the inner block controls a branch, and note that the "else" labels for both branches go to the same block. You need this kind of control flow for the transform to be correct.

It should work on CFGs like this you mean?

```
A-> B, C
B -> C, D
```

https://github.com/llvm/llvm-project/pull/158773