[clang] [clang] [x86] Rewrite the Sys V Classification Algorithm to Better Match SysV ABI and gcc (PR #221746)

[Eli Friedman via cfe-commits]

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

I'm not sure about forking the algorithm into two separate implementations... why did you decide to go this route?  I can see some reasons why you might, but I'd like to start from your explanation.

How hard would it be to modify the 24 algorithm to add narrow checks to detect cases that would be handled differently by the 23 algorithm?

https://github.com/llvm/llvm-project/pull/221746