Mail Archives: djgpp/1999/09/10/09:51:43
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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