[llvm] [FuncSpec] Skip SCCP on blocks of dead functions and poison their callsites (PR #154668)

[Mikael Holmen via llvm-commits]

mikaelholmen wrote:

> It seems that (post) dom tree analysis is not updated. I am still trying to compile LLVM with EXPENSIVE_CHECKS to reproduce. Hopefully, I will post the fix today. @mikaelholmen, feel free to revert if it's emergent.

No need to revert for me, I just noticed this in a private buildbot that we have and thought I'd mention it since I don't seen any comments about it from public bots here.

https://github.com/llvm/llvm-project/pull/154668