Date: Fri, 15 Mar 1996 12:32:21 -0700 From: nate@sneezy.sri.com (Nate Williams) To: hackers%FreeBSD.org@sri.com Subject: GAS question Message-ID: <199603151932.MAA11752@rocky.sri.MT.net>
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I'm bouncing this through sri.com in hopes that it gets to the mailing
lists due to Sprintnet problems. Please respond to
'nate@sneezy.sri.com' (it should be setup to do that).
]
Can someone explain to me the following piece of code please? I can't
find *any* documentation on it, and I've stared at it long enough but
still can't answer what it does definitively.
Thanks!
Nate
--------
inline int
apm_int(u_long *eax, u_long *ebx, u_long *ecx)
{
u_long cf;
__asm ("pushl %%ebp
pushl %%edx
pushl %%esi
xorl %3,%3
movl %3,%%esi
lcall _apm_addr
jnc 1f
incl %3
1:
popl %%esi
popl %%edx
popl %%ebp"
: "=a" (*eax), "=b" (*ebx), "=c" (*ecx), "=D" (cf)
: "0" (*eax), "1" (*ebx), "2" (*ecx)
);
apm_errno = ((*eax) >> 8) & 0xff;
return cf;
}
Most of this is obvious, but these two lines completely baffle me.
: "=a" (*eax), "=b" (*ebx), "=c" (*ecx), "=D" (cf)
: "0" (*eax), "1" (*ebx), "2" (*ecx)
Obviously it sets up some sort of mapping between the variables &
parameters and the assembly level registers, and some comments I've read
on similar code implies that it also says something regarding
optimizations (similar to volatile and const?).
Please help me oh gas gurus. :)
Nate
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