[llvm] [llvm] Win x64 Unwind V2 2/n: Support dumping UOP_Epilog (PR #110338)

[Daniel Paoliello via llvm-commits]

dpaoliello wrote:

> Can you use yaml2obj to write testcases?

Done

> 12 bits seems a bit small, but I guess I'll see how you address that in followup patches.

Yep, it's one of the limitations of v2: epilogs must be within 4Kb of the function end.

Essentially, there will be two different modes that can be enabled:
* Enable v2 unwind info: this will emit v2 where possible, but fallback to v1 where requirements are not met.
* Require v2 unwind info: this will always emit v2, which means that we will need to change code generation to meet the requirements (move epilogs to within 4Kb of end, all prologs must be in "canonical" form, etc.).



https://github.com/llvm/llvm-project/pull/110338