[llvm] [WinEH] Track changes in WinEHPrepare pass (PR #134121)

[Heejin Ahn via llvm-commits]

aheejin wrote:

A function has a personality function attached only when there are `invoke`s and `landingpad`/`catchpad`/`cleanuppad`s in the function, so I think checking the existence of a personality function should be fine.

https://github.com/llvm/llvm-project/pull/134121