[llvm] [PGO] Add `llvm.loop.estimated_trip_count` metadata (PR #148758)

[Mircea Trofin via llvm-commits]

mtrofin wrote:

> > still reading through, and sorry for the delay on my end, I was on vacation.
> 
> No worries. I'm still catching up after a vacation as well.
> 
> > One high level question, should this maybe also touch the bitcode validator?
> 
> Are you suggesting something similar to your ProfileVerifierPass?

No - llvm/lib/IR/Verifier.cpp rather. See e.g. visitProfMetadata there. You could get it to verify that the new metadata is well-formed (like, has the right number of arguments)

https://github.com/llvm/llvm-project/pull/148758