What happens with repne movsb ?

flat assembler
Message board for the users of flat assembler.

Index > Main > What happens with repne movsb ?

Author

Thread

hckr83

Joined: 12 Nov 2006
Posts: 86
Location: usa

hckr83 25 Feb 2007, 01:16

I am working on an emulator and need to know what should be done when repne prefix is there and the string instruction is movsb..is it just ignored and acted like rep? or invalid opcode?

now I know most assemblers will warn against this, but at the bytelevel anything is possible..

_________________
x86 CPU Emulation library: http://sourceforge.net/projects/x86lib

25 Feb 2007, 01:16

vid
Verbosity in development

Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia

vid 25 Feb 2007, 07:07

why not just try it? Wink

25 Feb 2007, 07:07

MazeGen

Joined: 06 Oct 2003
Posts: 977
Location: Czechoslovakia

MazeGen 26 Feb 2007, 10:06

I guess it is the same like with 0xF3 prefix - if the repeated instruction doesn't alter ZF, it is REP prefix, otherwise it is REPE/REPZ.

26 Feb 2007, 10:06

Vasilev Vjacheslav

Joined: 11 Aug 2004
Posts: 392

Vasilev Vjacheslav 26 Feb 2007, 11:21

check intel instruction set

26 Feb 2007, 11:21

MazeGen

Joined: 06 Oct 2003
Posts: 977
Location: Czechoslovakia

MazeGen 26 Feb 2007, 11:39

According to oficial documentation, instructions like REPNE MOVSB or REPNE STOSB actually do not exist. And I found nothing related to their behaviour.

26 Feb 2007, 11:39

< Last Thread | Next Thread >

Forum Rules:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum