#include <stdio.h>
#include <time.h>
#include <stdlib.h>

__attribute__((noinline))
int cmpi(unsigned int x, unsigned int y) 
{
  return __builtin_memcmp(&x,&y,4);
}

__attribute__((noinline))
int cmpi2(unsigned int x, unsigned int y)
{
  asm("bswap %0" : "+r"(x));
  asm("bswap %0" : "+r"(y));
  return x - y;
}

__attribute__((noinline))
int cmpa(unsigned int * x, unsigned int * y, size_t size)
{
  return __builtin_memcmp(x,y,size);
}

__attribute__((noinline))
int cmpa2(unsigned int * x, unsigned int * y, size_t size)
{
  int i = 0;
  size /= 4;
  while (i < size && x[i] == y[i]) ++i;
  if (i == size) return 0;
  asm("bswap %0" : "+r"(x[i]));
  asm("bswap %0" : "+r"(y[i]));
  return x[i] - y[i];
}

int main()
{
  unsigned int x,y,i;
  int xa[256] = {}, ya[256] = {};
  int s,f;
  clock_t t;
  x = *(unsigned int *)("a  b");
  y = *(unsigned int *)("b  a");

  printf("Memory compare int:\n");
  t = clock();
  for (i = 0; i != 0x1000000; ++i)
    cmpi(x,y);
  s = clock() - t;
  printf("  %d\n", s);
  t = clock();
  for (i = 0; i != 0x1000000; ++i)
    cmpi2(x,y);
  f = clock() - t;
  printf("  %d\n",f);
  printf("  Speed up: %f\n", (double)s/f);


  printf("Memory compare 16 bytes:\n");
  xa[3] = 6;
  t = clock();
  for (i = 0; i != 0x1000000; ++i)
    cmpa(xa, ya, 16);
  s = clock() - t;
  printf("  %d\n", s);
  t = clock();
  for (i = 0; i != 0x1000000; ++i)
    cmpa2(xa, ya, 16);
  f = clock() - t;
  printf("  %d\n",f);
  printf("  Speed up: %f\n", (double)s/f);
  xa[3] = 0;

  xa[15] = 6;
  printf("Memory compare 64 bytes:\n");
  t = clock();
  for (i = 0; i != 0x1000000; ++i)
    cmpa(xa, ya, 64);
  s = clock() - t;
  printf("  %d\n", s);
  t = clock();
  for (i = 0; i != 0x1000000; ++i)
    cmpa2(xa, ya, 64);
  f = clock() - t;
  printf("  %d\n",f);
  printf("  Speed up: %f\n", (double)s/f);
  xa[15] = 0;

  xa[255] = 6;
  printf("Memory compare 256 bytes:\n");
  t = clock();
  for (i = 0; i != 0x1000000; ++i)
    cmpa(xa, ya, 256);
  s = clock() - t;
  printf("  %d\n", s);
  t = clock();
  for (i = 0; i != 0x1000000; ++i)
    cmpa2(xa, ya, 256);
  f = clock() - t;
  printf("  %d\n",f);
  printf("  Speed up: %f\n", (double)s/f);
}