[llvm] [Local][MergeFunc] Handle !callees when two calls are merged (PR #225307)

[Nikita Popov via llvm-commits]

https://github.com/nikic requested changes to this pull request.

Separate the SimplifyCFG and MergeFunc fixes. SimplifyCFG looks fine at a glance. MergeFunc should be fixed by switching to combining metadata instead of comparing it, as we recently did for poison flags.

https://github.com/llvm/llvm-project/pull/225307