[llvm] [DebugInfo][LICM] Fix missing debug location updates (PR #91729)

[Paul T Robinson via llvm-commits]

pogo59 wrote:

> This may end up being an unpopular opinion (propagating the location is a noop because it'll get dropped, but it still has a runtime cost). @pogo59 wdyt? I might be making it up but I think I recall a similar discussion happening recently where you were involved.

I vaguely remember that, but not in enough detail to be sure I will say something consistent here.

It would be an unusual use of `assert` for sure, and I think it would be preferable to have a test that checks the location is lost. Then the test is already written, it will fail when we handle line locations differently, and a comment in the test can say we expect this to need updating when we fix hoist to do the right thing.

https://github.com/llvm/llvm-project/pull/91729