Extended inline assembly error with gcc: impossible constraints

[Ayush_Agrawal]

The other day I was reading a document about inline assembly (http://www.delorie.com/djgpp/doc/brennan/brennan_att_inline_djgpp.html).

I got stuck at the rep_movsl code. I tried running it on my PC. At first I got no error when it was the only thing in the code. But when I tried to actually use it, the compiler complained "‘asm’ operand has impossible constraints".

I am unable to figure out my way. I have already googled about it, but all vain.

I was wondering if there was something wrong with my compiling command. All I am using is "gcc code.c".

I would be great if anyone could look at my code (below) and help me out.

Thnx.


#include <stdio.h>

#define rep_movsl(src, dest, numwords) \
__asm__ __volatile__ ( \
"cld\n\t" \
"rep\n\t" \
"movsl" \
: : "S" (src), "D" (dest), "c" (numwords) \
: "%ecx", "%esi", "%edi" )

int main(int argc, char const *argv[])
{
int arr1[4] = {1, 2, 3, 4};
int arr2[4];

rep_movsl(arr1, arr2, 4);

int i;
for(i=0;i<4;++i)
printf("%d ",arr2[i]);
return 0;
}