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

[Farid Zakaria via llvm-commits]

fzakaria wrote:

@MaskRay I also have a change that auto expands eh_frame and gcc_except_table automatically as needed if they are going to overflow, similar to how you landed that for eh_frame_hdr. 

It's a little more complex/larger of a change since it has to perform address calculation first and shift all the type entries in gcc_except_table that gets expanded BUT it can be applied regardless of mcmodel. 

Would you be interested in seeing this patch ?

For us at Meta, this allows us to also tackle pre compiled small code-models and I like that it fixes the issues as needed.

It's part of a series of changes I have been referring to as "reverse relaxation". 

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