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/*
* So far I cannot figure out how I used to compile this :/
* asm(".intel_syntax prefix");
*
*/
#include <stdio.h>
void asm_summation(int *n)
{
asm("xor eax, eax \n" /* summation */
"mov ecx, 0 \n" /* counter */
"mov edx, %0 \n" /* end */
"_loop: \n"
"add eax, ecx \n"
"inc ecx \n"
"cmp ecx, edx \n"
"jle _loop \n"
"mov %0, eax \n" : "=r" (*n) : "r" (*n) : "eax");
}
void asm_summation2(int *n)
{
if (*n <= 1)
{
*n = 0;
return;
}
asm("xor eax, eax \n" /* summation */
"mov ecx, %0 \n" /* counter */
"_loop2: \n"
"add eax, ecx \n"
"loop _loop2 \n"
"mov %0, eax \n" : "=r" (*n) : "r" (*n) : "eax");
}
void asm_rotate(int *n)
{
asm("mov eax, %0 \n"
"rol eax, 1 \n"
"mov %0, eax \n" : "=r" (*n) : "r" (*n) : "eax");
}
int main(int argc, char *argv[])
{
int i = 12;
/* output, input (r) = register, clobbered */
asm("mov eax, %0\n" : : "r" (i) : "eax");
printf("i is: %d\n", i);
int j = -1;
asm_summation2(&j);
printf("summation is %d\n", j);
int k = 2;
asm_rotate(&k);
printf("k = %d\n", k);
return 0;
}
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