Gary,

The edk2 is freestanding UEFI firmware and the runtime does not support floating point exceptions. 

I think a long time ago there was an optimization bug and the -mno-sse fixed it. 

The UEFI x64 ABI is Windows like and not Sys V like. 

Thanks,

Andrew Fish

> On Apr 4, 2019, at 10:13 AM, Gary Zibrat via Groups.Io <gzibrat=google.com@groups.io> wrote:
> 
> Does anyone know why -mno-sse is specified on Clang x64?
> https://github.com/tianocore/edk2/commit/6f756db5ea057ff10dd168c7627163cec046a3d9 <https://github.com/tianocore/edk2/commit/6f756db5ea057ff10dd168c7627163cec046a3d9>
> There doesn't seem to be a corresponding flag for other compilers.
> 
> I ask because a commit in LLVM breaks compilation of EDK2:
> https://reviews.llvm.org/rL357317#change-QSW9B7DqCGUI <https://reviews.llvm.org/rL357317#change-QSW9B7DqCGUI>
>