Re: [PATCH] i386 entry.S alignment tweak
Jamie Lokier (lkd@tantalophile.demon.co.uk)
Mon, 14 Dec 1998 13:45:13 +0000
On Mon, Dec 14, 1998 at 11:29:43AM +0000, Riley Williams wrote:
> I remember seeing some assembly that had the following sequence in the
> middle thereof (not for gcc but you can probably decode it):
>
> LOCK
> SEG ES
> MOV DI,DI
>
> The first time I read through that, I wondered what on earth it was
> supposed to do, and only later did I realise it was effectively a
> rather verbose NOP instruction...
Not just verbose, but very very slow on any of the modern processors.
Multiple nops would probably be faster :-)
GAS generates this for the same length:
leal 0x0(%esi,1),%esi
-- Jamid
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