A way to count leading 0 bits of a 32 bit int in 5 instructions :)

Count leading zeros

#include <stdio.h>

/*
You can do the same with a built in function if your compiler supports it:

zeros = __builtin_clz(arg);
*/

int main(int argc, const char *argv[])
{
    // number for which you want to count leading zeros
    unsigned int arg = 2147483648;
    unsigned int result;

    asm ("bsr %0, %%eax\n"
         "movl $63, %%ecx\n"
         "cmovz %%ecx, %%eax\n"
         "xor $31, %%eax\n"
         "movl %%eax, %1\n"
         : "=r" (result)
         : "r" (arg)
         : "%eax", "%ecx");

    printf("zeros: %d\n", result);

    return 0;
}