[llvm] [DebugInfo] Add clang flag to enable function-level debug line attribution (PR #93985)

[David Blaikie via llvm-commits]

dwblaikie wrote:

Might want/need to start with this patch split up - adding the assembly first, then using it for LLVM code generation.

Which, I think, will mean needing to define some assembly directives to use this functionality in the assembler/assembly code (which, at a very cursory glance of this patch, aren't provided yet)?

While it's true we do emit some DWARF when using the integrated assembler that we cannot emit via assembly (the ability to use multiple separate line tables, I think, in LTO - only done when going direct to machine code via the integrated assembler, and when going via assembly we get one monolithic line table) - it's not an ideal state and this feature's a bit more intrusive than whether or not it's one line table or smaller separate line tables (those are at least roughly semantically equivalent - this new proposed feature isn't just a difference in encoding, but in functionality/content)

https://github.com/llvm/llvm-project/pull/93985