This is the mail archive of the gcc-help@gcc.gnu.org mailing list for the GCC project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: My inline assembly has the cooties.


Marco Manfredini wrote:
Hi,
The first thing I always realize when I return to code with inline assembly is, that I forgot the dodgy intricacies again. Today I seem to suffer from paralytic blindness. Could someone please enlighten me, why this program prints 20 with gcc 4.2.2 and 1010 with gcc-3.4.4?



I give up. Is it because you didn't declare %0 as an early clobber?


Perhaps it should be: ...."=&r"(r)...

David Daney



#if 0
gcc $0 -o ${0%.*}
exit 0
#endif
#include <stdio.h>
struct S
{
int v; };


int main()
{
struct S a={10}; struct S b={1000}; int r=0;
__asm__ volatile(
"/*XXXXXXXXXXXXX [%0]=[%1]+[%2] XX */\n " "\t movl %1,%0 \n"
"\t addl %2,%0 \n"
:"=r"(r)
:"g"(a.v),"g"(b.v));
printf("%d\n",r);
}


Cheers Marco



Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]