[llvm] [WIP] Aarch64: Always emit .seh_endprologue (PR #158173)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

I think we only want the .seh_endprologue in the cases where we actually have an epilogue.  If we don't need a prologue or epilogue, we can completely omit the .pdata record as an optimization.  (https://learn.microsoft.com/en-us/cpp/build/arm64-exception-handling?view=msvc-170#pdata-records)

Strictly speaking, I think we something with cend to correctly express callee-pop calls, so the computed stack pointer on entry is consistent.  I'm not sure how much it matters in practice, though; the caller will usually have a frame pointer.

https://github.com/llvm/llvm-project/pull/158173