[llvm] [DebugInfo][JumpThreading] Fix missing debug location updates (PR #91581)

[Orlando Cazalet-Hyams via llvm-commits]

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@@ -7,6 +7,9 @@
 ; parent blocks. And that ino jump-threading, the old dbg.value gets
 ; deleted.
 
+; Test debug location preserving in function threadGuard, which replaces
+; instructions with PHINodes at the end of the function. [[TMP1]]
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OCHyams wrote:

nit: "at the end of the function" are you referring to the code threadGuard? This feels like a comment that could go stale quite easily. I also find the first part a little hard to parse - perhaps the comment could be replaced with something along the lines of "Test that jump threading's `threadGuard` propagates the debug location to the `phi` from the instruction it replaces (`%retVal`)."?

also nit: `[[TMP1]]`?

My comment in the next test about `utils/update_test_checks.py` applies to this one too.



https://github.com/llvm/llvm-project/pull/91581