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

[via llvm-commits]

Andarwinux 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.

Could you take a look at [this](https://github.com/llvm/llvm-project/issues/165998)? I used bisect to determine the crash was caused by this PR, but your fix doesn't seem to fully fix the problem I'm encountering.

To be precise, the original crash was fixed, but it subsequently crashed in the same manner elsewhere. Furthermore, it appears the problem doesn't occur as long as --pgso=false is not specified.

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