From mboxrd@z Thu Jan  1 00:00:00 1970
From: Hendrik Visage <hvjunk@gmail.com>
Subject: Re: different asm code
Date: Mon, 18 Feb 2013 17:22:32 +0200
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To: horseriver <horserivers@gmail.com>
Cc: linux-assembly@vger.kernel.org

On Mon, Feb 18, 2013 at 7:06 AM, horseriver <horserivers@gmail.com> wrote:
> hi:)
>
>   I have compiled a .S file ,using command gcc -c x.S -o x.
>   Then I use objdump to look up its asm code, even find that some code is not the
>   same as that .S file , more important is , some code in origin  .S file has disappear .
>
>   what is about the reason ? If it is due to version , why some code chould get lost after compile?

Give examples please.

There are several "similar"/equivalent code/instructions that the
assembler could chose from.

Ie. to zero a register, you could
1) mov REGISTER,0
2) xor REGISTER, REGISTER
3) mv REGISTER,g0 (on a SPARC where g0 is always zero)