lkml.org 
[lkml]   [2000]   [Nov]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectIn line ASM magic? What is this?
I am trying to understand what is going on in the following code.  The
reference for %2, i.e. "m"(*__xg(ptr)) seems like magic (from
.../include/i386/system.h). At the same time, the code "m" (*mem) from
the second __asm__ below (my code) seems to generate the required asm
code. Before I go with the simple version, could someone tell me why?
Inquiring minds want to know.

struct __xchg_dummy { unsigned long a[100]; };
#define __xg(x) ((struct __xchg_dummy *)(x))

__asm__ __volatile__(LOCK_PREFIX "cmpxchgl %b1,%2"
: "=a"(prev)
: "q"(new), "m"(*__xg(ptr)), "0"(old)
: "memory");


__asm__ __volatile__(
LOCK "cmpxchgl %1,%2\n\t"
:"=a" (result)
:"r" (new),
"m" (*mem),
"a0" (test)
: "memory");


George
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 12:45    [W:0.023 / U:3.456 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site