Re: x86 D flag: what's its status thru the program?

Lukasz Michal Rak <[email protected]> Mon, 5 Jul 2004 15:23:44 +0200 (CEST)
Newsgroups org.kernel.vger.linux-gcc
Message-ID <[email protected]>
	Hi all!

 The convention is that the D flag in IA32 is cleared. So if you call a
subroutine you have to clear D flag before making call. The subroutine can
change the state of D flag, but before returning the routine has to clear
the D flag.
 Hope I helped.

 Regards,

			Lukasz


> Is this Direction flag (for the movs instructions) has some assumed
> value (say, as after cld)?  I ask because the many program sources
> show interesting behaviour: from one side, this flag is always set
> before the string insns (cld or std), but from the other side, if the
> programs does std then it always does cld after.  So, nobody leaves it
> set, but nevertheless, everybody set it clear.  Why?
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