From:	horst DOT kraemer AT snafu DOT de (Horst Kraemer)
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: GCC 2.95 global string crashes on 386..
Date:	Fri, 10 Sep 1999 11:32:08 GMT
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On Fri, 10 Sep 1999 11:27:19 +0800, "Rob Kramer"
<robk AT cyberway DOT com DOT sg> wrote:

> I've disassembled the executable, and it seems the compiler issues a locked 
> 'xaddl' instruction. I couldn't find opcode 'c1' in my 386 reference manual, 
> so this may be a 486++ instruction?

Yes.  The XADD instruction was introduced with 486 and produces
nonsense or a crash on a 386- system, of course,

> (I can't find anything but Intel's 386 
> manual online, sigh)
> 
>     2052:	f0 0f c1 02    	lock xaddl %eax,(%edx)

The effect is that (edx) will contain the sum of (edx) and eax, just
as for a normal add, but eax will not retain its old value but it gets
the old value of (edx).

Regards
Horst

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