[clang] [lld] [llvm] [lld][llvm/mc] Add support for sdata8 for FDE CIE (PR #174508)

[Farid Zakaria via cfe-commits]

fzakaria wrote:

@MaskRay -- Hi Ray, thanks for taking the time to look at this patch.
I've updated the title to also reflect llvm/mc.

I am not sure what entails "coordination" with GCC folks. Sending an email to their distribution list to let them know?
The other option would be for clang to emit sdata8 for medium code irrespective of the flag.

The lld changes are only a test file but although the changes are specific to `llvm-mc`; I hit the relocation overflow of the FDIE during relocations at link time which is why I tagged it as such.

If I don't include the clang driver option, this can still be toggle via `-Wa` ?

https://github.com/llvm/llvm-project/pull/174508