[llvm] [BranchFolder] Fix missing debug info with tail merging (PR #94715)

[Jeremy Morse via llvm-commits]

https://github.com/jmorse commented:

Am I right in thinking that this is preserving the source-location on branch instructions that _aren't_ merged but were manipulated during analysis? If so, LGTM.

It would be undesirable if we gave a source location to a branch that's been merged with other branches without using `DILocation::getMergedLocation` as it could cause an untrue line number to appear on a path that it shouldn't. I think (80% confidence) this patch shouldn't make that happen though.



https://github.com/llvm/llvm-project/pull/94715