[llvm] Symbolize line zero as if no source info is available (PR #124846)

[Paul T Robinson via llvm-commits]

pogo59 wrote:

> Admittedly, the DWARF spec isn't /entirely/ clear that the file doesn't matter if line is zero - you could argue that the file is meaningful even if the line is zero and means the instruction came from "somewhere in this file" - but that generally hasn't been the interpretation the LLVM project has taken. (we could file a DWARF issue to get this clarified)

Not sure I've seen anyone suggest the "somewhere in this file" interpretation before. I find it hard to imagine "from this file but no particular line" as being usefully distinct from "no source line whatsoever." (And DWARF (at least as of v5) has no way to specify "no file" in any case.)

https://github.com/llvm/llvm-project/pull/124846