[clang] [llvm] [win][x64] Unwind v2 3/n: Add support for requiring unwind v2 to be used (equivalent to MSVC's /d2epilogunwindrequirev2) (PR #143577)

[Eli Friedman via llvm-commits]

https://github.com/efriedma-quic commented:

I'm a little concerned about the wording of the errors here. The "too many epilogues" and "too many opcodes" errors should say that it's not yet implemented, or something, so it's clear it's a limitation of the compiler.  Maybe try to suggest a workaround of some sort... maybe mention tail-calls since that's the most likely culprit.

The other conditions shouldn't occur at all: there's no reason to generate an epilogue that doesn't match the prologue, as far as I know.

https://github.com/llvm/llvm-project/pull/143577