Messages in this thread |  | | Date | Wed, 15 Nov 2000 12:55:46 -0800 | From | George Anzinger <> | Subject | In line ASM magic? What is this? |
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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");
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