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From: Doug Rabson <dfr@nlsystems.com>
To: Daniel Eischen <eischen@vigrid.com>
Date: Sat, 3 Apr 2004 18:23:54 +0100
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cc: threads@freebsd.org
cc: Julian Elischer <julian@elischer.org>
Subject: Re: PERFORCE change 50188 for review
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On Friday 02 April 2004 21:22, Daniel Eischen wrote:
> On Fri, 2 Apr 2004, Julian Elischer wrote:
> >
> > The SUN API allows the destination of the %gs:0 to be changes at
> > runtime by the user this allowing the UTS to switch threads "on the
> > fly" without going back to the kernel.
>
> Yes, please, I don't see how the one extra indirection is
> really going to affect much.  This is where we intended to
> go months ago (and years ago WRT KSE in general), and
> everything has been designed around it.

I was just wandering around the internet looking at the scenery and I 
ended up here: 
http://gcc.gnu.org/onlinedocs/gcc/i386-and-x86-64-Options.html.

This document describes a new options (which is not supported by the 
compiler in current right now), -mno-tls-direct-seg-refs. This looks 
like it will do everything we need for both i386 and amd64, i.e. 
instead of code like:

	movl	%gs:x@ntpoff, %eax

it should generate:

	movl	%gs:0, %eax
	movl	x@ntpoff(%eax), %eax

Although I'm still not quite convinced that we can't do the first 
version with essentially zero cost for i386 at least.