[llvm] [DWARF5][COFF] Fix wrong relocation in .debug_line (PR #83773)

[Martin Storsjö via llvm-commits]

mstorsjo wrote:

I'm not very familiar with DWARF overall, or what DWARF 5 brings, but some extra context:

When the overall switch to DWARF 5 was made, the Windows targets stuck to DWARF 4, see 9c6272861032f511a23784ce0c5cc8f6ac2f625b and 6cf64b2d2858dc93c3ec93438bdaca2807847e9b. From what I remember, neither GDB nor LLDB worked with the DWARF 5 output. I guess this fix is the missing key here, although from what I remember, the breakage might have been bigger than just not finding the right souce files. It'd be interesting to know if GDB and LLDB work with our DWARF 5 output after this change.

We've had to do similar fixes for COFF before, for using the right kind of relative relocations - see e.g. 47046f05e66c23567d6672ea5a1afd8ed2c411ed.

Thus, my take on this is that the fix sounds reasonable and plausible, but I don't have all the nitty gritty details in mind right now.

https://github.com/llvm/llvm-project/pull/83773