[Bug inline-asm/66631] inability to clobber segment regs makes tls problematic

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66631

--- Comment #14 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Stas Sergeev from comment #12)
> Note that on x86_64 you can't set FS without a syscall.
> I would really hate doing that in asm it seems.

Yes because you are setting the TLS segment.  Again why are you abusing the fs
segment here not to be the TLS segment?