Andrew,
In UefiCpuPkg\Library\CpuExceptionHandlerLib\X64\, there are two nasm files: ExceptionHandlerAsm.nasm and the other XCODE version.

The major diff between the two is the second operand in "mov rax, ASM_PFX(CommonInterruptEntry)" is patched at runtime by code, instead of relying on linker/loader to fix it.
Can I know more background why it's needed for XCODE?

Given Apple is switching away from X86 CPU, is the XCODE version still needed?

+ Mike because I found another commit by you for bug: 565 - Fix X64 XCODE5/NASM compatibility issue in UefiCpuPkg MpInitLib (tianocore.org)<https://bugzilla.tianocore.org/show_bug.cgi?id=565>.

Thanks,
Ray