[llvm] [LoopUnroll] Fix block frequencies for epilogue (PR #159163)

[Joel E. Denny via llvm-commits]

jdenny-ornl wrote:

> > > It looks like this is causing a crash for the `opt -passes='loop-unroll<O3>'`:
> > 
> > 
> > Thanks. Is there a bot somewhere that shows the crash?
> 
> no, this is when building a large C/C++ workload

PR #165938 fixes it for me.

https://github.com/llvm/llvm-project/pull/159163