[llvm] Instruction: avoid crash in getStableDebugLoc when `this` isn't a DbgInfoIntrinsic (PR #66266)

[Augie Fackler via llvm-commits]

durin42 wrote:

> Thanks for getting a patch together -- IMO it there's no next instruction, we should return an empty source location, i.e. `return DebugLoc();`. 

I tried this, and that preserves the segfault.

We're working on extracting some sort of reduced input here, but if I disable optimizations to try and dump the information you requested I appear to invoke some sort of UB elder god and the test mysteriously passes.

https://github.com/llvm/llvm-project/pull/66266