[clang] Adds an arbitrary pseudonym to clang"s windows mangler... (PR #97792)

[Max Winkler via cfe-commits]

MaxEW707 wrote:

@memory-thrasher

Godbolt for reference: https://godbolt.org/z/b9v8KhPET

I don't follow that MSVC 1920+ does not support this mangling properly. It appears that it does. I haven't dug too deep into the C++20 MSVC mangling for NTTP yet but it does appear MSVC does support this properly in its mangling scheme.

I am not opposed to doing our own ad-hoc mangling for now to just get this working but in general `-msvc` triple is supposed to adhere to msvc mangling including all its bugs. I'll try to get to this PR sometime this weekend under the assumption we will use the current custom ad-hoc mangling that isn't MSVC compatible in the interim.

Funnily enough we were just discussing this here, https://github.com/llvm/llvm-project/issues/94650#issuecomment-2209626547, and I was about to write up a discourse on such a discussion tomorrow morning.

https://github.com/llvm/llvm-project/pull/97792