X-Authentication-Warning:	delorie.com: mail set sender to djgpp-bounces using -f
From:	RayeR <glaux AT centrum DOT cz>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Using inline asm
Date:	Sun, 28 Oct 2007 19:46:23 -0700
Organization:	http://groups.google.com
Lines:	24
Message-ID:	<1193625983.368281.325560@57g2000hsv.googlegroups.com>
References:	<471FEAC8 DOT 5179 DOT 2FAB88DB AT gerritvn DOT gpvno DOT co DOT za>
	<200710250120 DOT l9P1KEb2032374 AT envy DOT delorie DOT com>
	<1193303455 DOT 688747 DOT 180190 AT 50g2000hsm DOT googlegroups DOT com>
	<200710251524 DOT l9PFOeNi022585 AT envy DOT delorie DOT com>
NNTP-Posting-Host:	89.176.103.47
Mime-Version:	1.0
X-Trace:	posting.google.com 1193625983 17849 127.0.0.1 (29 Oct 2007 02:46:23 GMT)
X-Complaints-To:	groups-abuse AT google DOT com
NNTP-Posting-Date:	Mon, 29 Oct 2007 02:46:23 +0000 (UTC)
In-Reply-To:	<200710251524.l9PFOeNi022585@envy.delorie.com>
User-Agent:	G2/1.0
X-HTTP-UserAgent:	Mozilla/5.0 (Windows; U; Win98; en-US; rv:1.8.1.6) Gecko/20070802 SeaMonkey/1.1.4,gzip(gfe),gzip(gfe)
Complaints-To:	groups-abuse AT google DOT com
Injection-Info:	57g2000hsv.googlegroups.com; posting-host=89.176.103.47;
	posting-account=ps2QrAMAAAA6_jCuRt2JEIpn5Otqf_w0
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp
Reply-To:	djgpp AT delorie DOT com
Errors-To:	nobody AT delorie DOT com
X-Mailing-List:	djgpp AT delorie DOT com
X-Unsubscribes-To:	listserv AT delorie DOT com

> In the case of gcc, it means "changes in a way that is not known to
> gcc".  GCC will make no assumptions about the contents of the register
> after the asm.

Thanks all for explanation, so if I understand well, the example by
Peter show it right:

>asm("cpuid" : "=a" (eax) : "a" (level)  : "ebx", "ecx", "edx");

The last part of asm block lists the "clobbered" registers which was
changed by CPUID
and we need to tell GCC to restore them automatically - so no push/pop
needed around.
eax is excluded because it is input/output parameter so GCC knows it
was changed because
it had to put the value from a variable to eax.

When I needed some inline asm i looked for examples on the internet
and not all of it
was using the clobber list so it was confusing. I'll have to check my
src if I not
forget it somewhere but I think I was paranoic and used push/pop
instead..

- Raw text -