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[Bug inline-asm/66631] inability to clobber segment regs makes tls problematic
- From: "stsp at users dot sourceforge.net" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Tue, 23 Jun 2015 10:00:21 +0000
- Subject: [Bug inline-asm/66631] inability to clobber segment regs makes tls problematic
- Auto-submitted: auto-generated
- References: <bug-66631-4 at http dot gcc dot gnu dot org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66631
--- Comment #16 from Stas Sergeev <stsp at users dot sourceforge.net> ---
Actually, Andrew, do you think this is even
TLS specific? No segregs are restored at all (not even DS,
I was wrong saying it is), so is it guaranteed, if FS
is restored by some other means, that gcc will not
start using some "movs" instruction before init_handler(),
or some ds-prefixed access?
So, my guess is this:
- If this is only TLS-specific and gcc really really doesn't
want to implement a nice possibility of clobber segregs,
then I'll probably start asking linux kernel people about
a possible solution. After all, restoring TLS is their task.
- BUT, if this is not TLS-specific but is unsafe with ANY
segreg, then I think gcc should just allow clobber.